10. QUESTIONS FOR THE EXPERT

In this section we have tried to obtain spontaneous responses from a number of experts in keratoplasty, on some specific issues that many of those who practice this field can come across and that are often the subject of controversy. We hope that these testimonies give us a practical and complementary vision of what is presented throughout this book.

1) In endothelial keratoplasty, what is your strategy and technique in cases with (a) previous glaucoma surgery (whether conventional or with valves), (b) aphakia (with or without anterior chamber (AC) intraocular lens (IOL)) and (c) chronic edema with little corneal transparency?

Dr. Gerrit Melles. As our experience increases, descemet-endothelial keratoplasty (DEK/DMEK) can be performed in more difficult cases and in our hands it is the preferable endothelial transplant technique, even in complicated circumstances such as those cited.

(a) In case of previous glaucoma surgery, the greatest challenges are due to the position of the bleb or tube, and hypotonia. To avoid damaging the conjunctiva, the bleb or the tube, you have to choose a suitable position for the tunnelled lining incision or reopen a pre-existing one. Since these eyes often do not maintain pressure on the AC during descemetorhexis, this situation can be countered by smaller entrances, a Sinskey’s hook with infusion or an AC maintainer. To avoid damaging the graft during the deployment in eyes with drainage tubes, you can decentrate the graft away from the tube or first deploy it and raise it in the area without tube, before unfolding the part of the graft near the tube. If necessary, the tube can be trimmed or moved. At the end of surgery, a firm eyeball will promote adhesion of the graft. However, since achieving this can be difficult in those eyes, the 100% complete air bubble must be maintained > 60 minutes or left (in pseudophakic eyes), since the air will escape more quickly through the tube.

(b) In aphakic eyes, the challenge can also be hypotonia, which can be handled as in the previous case. If vitrectomized, the AC can be very deep, and the air can escape through the pupil to the vitreous chamber. If there are vitreous “mushrooms” or bridles, they must be eliminated before inserting the graft, as they can impede its proper deployment. Contraction of the pupil can help during surgery and to avoid complications such as vitreous prolapse and dislocation of the graft. In eyes with an iris fixation IOL in AC, it is not necessary to remove it since it will act as an artificial diaphragm separating the vitreous from the AC, which helps to obtain the firm eye at the end of the intervention. The presence of this type of IOL can be advantageous for deploying the graft, creating a narrower AC.

(c) In eyes with long-lasting corneal edema and reduced transparency, it may be important to know that visibility can sometimes be better under the operating microscope than at the slit lamp. Transparency can be increased by filling the AC with air during the descemetorhexis, which also induces corneal dehydration. The visibility of the graft can be improved with sufficient staining. To facilitate the unfolding, it is preferable to inject a double roll. The repeated application of viscoelastic on the external face of the cornea improves visibility during this step, so that it is rarely necessary to remove the epithelium. If we consider the cornea too edematous for a DEK, we may consider instead a thin ELK (thin-DSEK).

Dr. Paolo Rama. (a) In cases with previous glaucoma surgery, whether conventional or with a drainage tube, my first option is an ELK/DSAEK. It is an easier and safer procedure and it is more likely that the graft adheres than with the DEK/DMEK. I suggest the latter in patients with discrete corneal edema, and high visual potential and expectations or, perhaps, in case of failure of ELK due to rejection. I still consider a PK in cases with severe edematous keratopathy and marked involvement of the stroma, or in cases with repeated ELK failures.

(b) In cases of aphakia (with or without AC IOL) my first option is ELK. I rarely consider DEK in those cases. As in the previous one, the PK would be an option in severe edema or after multiple failures of endothelial keratoplasty.

(c) The ELK would also be my first option in cases of chronic edema with low transparency, removing the epithelium. I never consider DEK in these cases, in which the PK is an option as in the previous situations.

Dr. Mark Terry. (a) If a patient has corneal edema and a trabeculectomy or a drainage tube, we usually prefer the ELK/DSAEK to the DEK/DMEK. I have practiced the second in some of these cases, but almost always the air or gas bubble has disappeared completely or almost at the next day and the need to reinject is much higher than in normal cases. In addition, these eyes with glaucoma often have a limited visual potential and cannot appreciate the difference in visual quality between both techniques, so they are usually happy with the result of the first.

(b) I only perform ELK in aphakic eyes that are left without IOL. Usually we will place a secondary IOL sutured to the sclera (in ciliary sulcus) or iris and then an ELK above. These eyes are usually vitrectomized and although a DEK is possible after a wide vitrectomy, it is much more difficult to deploy the graft in those eyes, while the ELK causes less trauma and has more consistent results. If, over time, the patient is not happy with the vision achieved with the ELK, we can consider the complex replacement for the other.

(c) We perform endothelial keratoplasty in all eyes with corneal edema, even if it is severe with low transparency. Usually we do a DEK, but in certain circumstances (congenital endothelial dystrophy, aphakia, AC IOL, drainage tube) we go to ELK. Even patients who only reach a vision of 0.5 after endothelial keratoplasty due to low transparency of the cornea, but do not need a contact lens (CL) or have high astigmatism, prefer it to a PK with all its aberrations and associated optical problems.

2) What are your current indications for penetrating keratoplasty (PK)?

Prof. Juan Durán de la Colina: Full-thickness opacities, very advanced keratoconus, complex lesions of the anterior segment and re-transplant with previous irregular graft.

Dr. Toni Salvador: When there is involvement of all layers of the cornea.

Dr. Javier Celis: Currently, I always plan on lamellar surgery to begin with. Only in the cases with stromal opacification and endothelial decompensation did I indicate a penetrating keratoplasty as the first option. Another situation in which I practice a penetrating transplant is perforating trauma with involvement of the visual axis.

Dr. José Luis Güell: Those situations in which besides presenting an endothelial failure, I consider the opacity and/or irregularity of the anterior cornea irreversible and intractable through another approach and always in the presence of a competent limbus.

Prof. Jorge L. Alió: Generalized corneal opacities. Corneal edema of very long duration with structural changes in the cornea.

Dr. Ana Boto: Endothelial failure with stromal opacity that does not allow endothelial transplantation, and endothelial failure with moderate corneal ectasia.

Dr. Emeterio Orduña: In general, when it is impossible to perform a lamellar technique – in case of corneal perforations, opacities and pathologies that affect the entire corneal thickness and failure of previous keratoplasties with stromal and endothelial involvement. Conversion from DALK.

Dr. Toni Sabala: Corneal leukomas that affect the full thickness, secondary to bacterial keratitis, herpetic keratitis or other cause, advanced bullous keratopathy with clear signs of stromal involvement and keratoconus with a previous history of hydrops.

Dr. Victoria de Rojas: In cases with simultaneous involvement of stroma and endothelium. (1) Very advanced endothelial dysfunction with long-term stromal edema and haze in which a complete recovery of the stromal transparency is not foreseeable, despite the disappearance of stromal edema. However, if one of these cases occurs in patients with poor prognosis for PK (advanced age, dementia, mentally handicapped) in which it pays to sacrifice a better visual result for a greater safety of the procedure, we perform an endothelial keratoplasty. The same happens if the eye has poor visual prognosis and the priority is to resolve the corneal edema to eliminate discomfort or pain. (2) Replacement of previous PK due to endothelial failure if elevated astigmatism or corneal leukomas. If endothelial failure occurs in PK with low astigmatism and transparent stroma, we prefer to perform an endothelial transplant, preferably DEK/DMEK. (3) Deep leukomas that affect the entire stroma up to Descemet’s membrane (DM) according to biomicroscopy and OCT exploration. We intend to perform DALK to evaluate the final transparency of the residual bed, whether it is a very posterior stroma or DM. Occasionally, the DM itself is opacified or even presents folds with fibrosis. In such cases we must weigh the advantages of a DALK with a somewhat diminished final visual acuity compared to a PK with better visual acuity, according to patient type, visual needs and risk of rejection, etc. (4) Corneal leukomas secondary to corneal perforation that affect the visual axis. In these cases, in order to perform a DALK, a manual dissection technique with a minimal stromal bed should be performed, in which the residual leukoma could still affect visual acuity. In particular cases, it can be assessed if it compensates sacrificing a better visual result in order to preserve the advantages of a DALK. If the leukoma secondary to perforation were outside the visual axis, we would try a DALK with manual dissection technique. (5) Serious non-controlled infections with medical treatment if the affectation is deeper than 300 μm. If the affectation is between 150 and 300 μm we perform DALK. The depth of corneal involvement is measured by OCT. (6) Corneal perforation not susceptible to treatment with corneal adhesive or amniotic membrane.

Dr. Jaime Etxebarria: Eyes with corneal perforations, with corneal decompensation and narrow AC (being phakic), ICE syndromes, with the iris near the endothelium, keratolysis, repeated failed ELK/DSAEK, important descemetocele and combined transplant/vitrectomy surgeries.

Dr. Tomás Martí: The indications to perform a PK have been limited to those cases in which all layers of the cornea are affected. It is usually penetrating trauma, severe herpetic keratopathy with endothelitis, or those cases of long-term graft failure that present with stromal scarring. A particularly frequent case that in my opinion is easier to solve by means of PK, is that of patients with corneal edema bearing an AC IOL. Normally, these are very damaged corneas with subepithelial fibrosis and stromal scarring, with the added complication that we must replace the AC IOL with an iris fixated IOL. These cases we prefer to handle through a PK.

Dr. Alberto Villarrubia: Corneal alterations that have endothelial failure (or, simply Fuchs’ dystrophy without edema) and with concomitant stromal pathology (either of ectatic, dystrophic, or leukomatous origin).

3) What are the quality criteria you use for a good donor cornea?

Prof. Juan Durán de la Colina: Except for lamellar keratoplasty, superficial or deep, acceptable endothelial state. For DEK/DMEK, corneas from donors older than 50 years. For ELK/DSAEK I receive pre-cut corneas. In these cases, especially healthy endothelial state. I do not set exact figures because it also depends on the age of the recipient. For SALK, a large scleral ring is necessary.

Dr. Toni Salvador: My corneas come from a bank with their donor tissue quality criteria. For endothelial keratoplasty and PK a count higher than 2,000 cells/mm2. A staining of the endothelium with trypan blue <10%. A 2-mm scleral ring in the closest place to the limbus. For ELK and PK: no history of cataract or refractive surgery. For DEK, age between 50 and 80 years. And without deep stromal alterations. For PK: stroma free of opacities at least up to a diameter of 8 mm.

Dr. Javier Celis: When we evaluate a cornea, we distinguish according to the use that we are going to give it. If it is destined for an endothelial transplant, we select corneas with counts >2,500 cells/mm2 with low levels of polymegatism and pleomorphism. If in addition they are studied under optical microscopy we observe that the percentage of cells that stain with trypan blue is <10%. If the cornea is intended for a PK, the requirements are similar in terms of polymegatism, pleomorphism and staining of cells with trypan blue, but in this case, we place the cut at 2,000 cells/mm2.

Dr. José Luis Güell: Those that the information I receive from the bank allows me: expiration, cellularity, age, central diameter of transparent tissue and (when present) previous ophthalmological surgical history, especially lamellar surgery.

Prof. Jorge L. Alió: Simply those provided by the eye bank, together with the visualization of the endothelial map that it provides us.

Dr. Ana Boto: For endothelial transplantation: endothelial count >2,200 cells/mm2. ELK: also runner >3 mm. DEK: donor >50 years. For PK: endothelial count >2,000 cells/mm2 and transparent stroma (if we do not have an endothelial count, age of the donor <65 years without prior ocular surgery and normal cornea in the slit lamp), transparent cornea >8.5 mm. For DALK; transparent stroma, transparent cornea >8.5 mm approximately (if we do not have a second cornea the same criteria as PK).

Dr. Emeterio Orduña: No presence of endothelial corneal alterations, guttae, inflammatory cells. Absence of pleomorphism and polymegatism. Minimal or absent endothelial staining with trypan blue. Endothelial count >2,500 cells/mm2 for endothelial transplants, >2,000 cells/mm2 for DALK and PK. No ghost vessels or central stromal alterations or opacities, in the case of gerontoxon, diameter greater than 10 mm for DALK and PK, for endothelial would be valid if the endothelium maintains the mentioned quality criteria. Always with negative microbiological controls.

Dr. Toni Sabala: Endothelial count >2,200 cells/mm2, high hexagonality (>70%) and little polymorphism (<20%). I like to see the printed image of the specular microscopy.

Dra. Victoria de Rojas: The quality criteria vary according to the procedure for which it will be used. (1) For PK: transparent area >7 mm (the size of the transparent area must be equal to or greater than the diameter of the planned donor button since trepanation over the senile arch area results in ovalization of the shape of the button in that area, with induction of astigmatism for this reason), absence of leukomas, endothelial count >2,000 cells/mm2, eyes operated on refractive surgery are excluded. (2) For deep anterior lamellar keratoplasty (DALK): transparent area >7 mm (same consideration as for PK), absence of opacity, eyes operated on refractive surgery are excluded, endothelial count >2,000 cells/mm2 (They can be used for DALK corneas with lower endothelial count if another cornea is available with adequate counting in case of macroperforation that requires reconversion to penetrating keratoplasty). (3) For superficial anterior lamellar keratoplasty (SALK): transparent area >7 mm, absence of opacities, eyes operated on refractive surgery are excluded, scleral ring suitable for artificial chamber, corneal cell count is indifferent for this procedure. In addition, cryopreserved corneas can be used. (4) For Descemet-endothelial keratoplasty (DEK/DMEK): it is possible to use corneas with opacity or transparent area <7 mm if it does not affect the posterior stroma, or eyes with previous refractive surgery, endothelial count >2,500 cells/mm2, or donor age >55 years. (5) For endothelial lamellar keratoplasty (ELK/DSAEK): it is possible to use corneas with leukoma or a transparent area <7 mm if it does not affect the posterior stroma, eyes operated on by refractive surgery, endothelial count >2,500 cells/mm2, or scleral ring suitable for artificial chamber.

Dr. Jaime Etxebarria: Endothelial count >2,000 cells/mm2, with negative serologies and PCRs. Ideally, we should ask the tissue bank for a cell viability study (e.g. with alizarin red) since it is common to find eyes with many cells and, when dyeing them with trypan blue to make the extraction of endothelium, observe that many of them are not viable. We are obsessed with counting and we should be even more obsessed with evaluating cell viability, a circumstance to improve in most tissue banks.

Dr. Tomás Martí: Obviously it depends on the keratoplasty we intend to perform. In DALKs, in which we do not have endothelial demands, the only question to be considered is that they have a wide transparent area avoiding the senile arch. In PK we prefer young corneas with >2,200 cells/mm2, whereas for endothelial transplantation the ideal cornea should have >2,500 cells/mm2. For ELK, corneas of patients operated on refractive surgery can be used and for DEK it is necessary for donors to be >60 years old and we prefer cultured corneas in which DM is probably easier to extract.

Dr. Alberto Villarrubia: We are somewhat more permissive in PK, although this should not really be the case and the criteria should be the same in all cases. To perform a PK: healthy stroma and endothelium >2,200 cells/mm2. For a DALK: healthy stroma regardless of the endothelium. For an endothelial transplant, we prefer corneas with >2,500 cells/mm2.

4) In case of rejection, what is your treatment protocol?

Prof. Juan Durán de la Colina: Except for exceptional cases (great vascularization, ocular surface lesions) only topical treatment: topical prednisolone or dexamethasone: starting every hour or every two hours, depending on the aggressiveness, on the first day. Then, every 2-4 hours for 1 week, with progressive reduction according to response. In very aggressive cases I add a peribulbar triamcinolone injection.

Dr. Toni Salvador: In acute phase: 40 mg of sub-Tenon's triamcinolone.

Dr. Javier Celis: It will depend on the type of rejection and the type of transplant. In general, in epithelial rejections, I increase the frequency of the topical corticosteroid. In the stromal rejection of a DALK I also increase the frequency of topical corticosteroids. In transplants with endothelium (PK and endothelial) with suspicion of endothelial rejection, I initially inject a sub-Tenon's corticosteroid depot (triamcinolone or betamethasone), in addition to increasing the topical corticosteroid regimen. In some special cases, such as children or patients with psychomotor retardation or little collaboration, I use a megadose of intravenous corticosteroid (500 mg of methylprednisolone in adults). As a preventive treatment, in case of a 2nd PK, I start immunosuppressive treatment with mycophenolate mofetil.

Dr. José Luis Güell: Although it will depend on the type and severity of it, in general, topical steroids with high instillation frequency, systemic corticosteroids, cycloplegia and eye pressure control (especially after the first 3 or 4 days of corticosteroid treatment).

Prof. Jorge L. Alió: The treatment is hourly topical corticosteroids, following Leibowich’s pattern. We adjust the treatment according to the response of the case. Eventually intracameral triamcinolone is placed if the eye shows a large inflammatory reaction.

Dr. Ana Boto: Dexamethasone eye drops: 1 drop every 15 minutes the first hour; every hour the first day, every 2 hours the second day and decrease according to answer. If it is impossible to comply with this guideline, I use dexamethasone eye drops 4 times/day and 8 mg of sub-Tenon’s triamcinolone. If it is a case of high risk or single eye, we add azathioprine 100 mg/day or mycophenolate mofetil 1 g/12h. If in 48 hours it does not respond to the topical regimen and there are no contraindications, we add an i.v. bolus of methylprednisolone 500 or 1000 mg.

Dr. Emeterio Orduña: 1% prednisolone acetate eye drops, 1 drop every 15 minutes for 2 hours followed by 1 drop every 1 hour for 24 hours. If there is improvement, I maintain the treatment until remission and then we continue a maintenance schedule with mild corticosteroids (FML). In case of DEK/DMEK, the remission is always obtained. If there is no improvement or rejection established (in PK especially) we begin with periocular and systemic corticosteroids. Cyclosporine A 2% in eye drops may be helpful. If there is remission and maintenance of corticosteroids is required, they are progressively substituted with cyclosporine A or mycophenolate mofetil according to tolerance to minimum dose that manages to maintain transparency. If there is no remission or there is loss of transparency, the PK is repeated.

Dr. Toni Sabala: 1% prednisolone acetate eye drops, 1 drop every 5 minutes for the first 2 hours, then every hour for 3 days and dexamethasone ointment at night. Then we review the case.

Dr. Victoria de Rojas: Topical corticosteroids every hour (prednisolone acetate 1%), dexamethasone phosphate ointment at night, cycloplegic eye drop at night (according to reaction in AC). We add according to severity of the rejection subconjunctival methylprednisolone, or pulses of methylprednisolone (500 mg) followed by oral prednisone (1mg/kg/day) for 5 days.

Dr. Jaime Etxebarria: If the edema is mild, topical corticosteroid treatment. If it is somewhat bigger, peribulbar corticoid and topical corticosteroid. If it does not improve in 1 week, or if corneal edema is important at the beginning, 3 pulses of methylprednisolone 500 mg i.v. in 3 consecutive days and continue with oral prednisone 30 mg/24 hours and oral cyclosporine A 5-7 mg/kg/day divided into 3 doses.

Dr. Tomás Martí: Normally I start with dexamethasone 1 drop every hour during the first 48 hours, maintaining the intensive treatment until the total disappearance of the inflammatory signs, especially the keratic precipitates and the ciliary injection. If the diagnosis was early, it is usually accompanied by a disappearance of the edema and the recovery of the previous visual acuity. In cases of very intense and repeated rejections, I add systemic corticosteroid therapy with paulatin descent. To prevent rejection, I introduce topical cyclosporine A prior to surgery in cases of repeated transplants, very large keratoplasties, highly vascularized recipients or responders to corticosteroids, without being sure of its efficacy. In any case, the best prevention of endothelial rejection is to perform a DALK whenever possible or an endothelial transplant on a previous rejected keratoplasty, instead of a new penetrating keratoplasty. Exceptionally in selected cases and usually single eyes, I ask for the collaboration of the internist to establish a systemic immunosuppression regimen.

Dr. Alberto Villarrubia: We never give systemic corticosteroids. We always start with dexamethasone in eye drops every 2-3 hours, depending on the severity of the rejection, cycloplegic 2-3 times a day and dexamethasone ointment at bedtime. Topical dexamethasone is gradually reduced depending on the response.

5) What is the preferred trepanation method for PK? And for DALK?

Prof. Juan Durán de la Colina: Suction trephine in both cases. I do not reach the perforation, which I do with a knife.

Dr. Toni Salvador: Hessburg-Barron system, from endothelial side in donor and epithelial side in recipient. Manual calculation for DALK with the same trephine.

Dr. Javier Celis: I usually use Hessburg-Barron vacuum trephines for the PK and I am starting to use the Moria adjustable trephines for the DALKs.

Dr. José Luis Güell: Although theoretically it is not my favourite, I usually work with anterior suction trephines like Hessburg-Barron (Medical Mix or Moria).

Prof. Jorge L. Alió: Femtosecond laser, both for PK and for DALK. In these we only use it for lateral cutting and not for cutting the bed.

Dr. Ana Boto: Hanna’s trephine (Moria).

Dr. Emeterio Orduña: Usually we use Barron's trephines, although for the DALK I prefer the Moria trephines with which the depth of the cut is better graduated.

Dr. Toni Sabala: For the recipient we use single-use trephines, like Hessburg-Barron. For DALK we use calibrated trephines. For the preparation of the donor in DALK, we like to make the cut from the epithelial side, with the use of an artificial AC and the single-use trepan. This technique lengthens the total surgical time, because it requires finishing the endothelial cut with scissors. For this reason, we sometimes make the cut on the endothelial side, using a single-use punch. In PK the donor is cut from the endothelial face: we do not cut from the epithelial side for fear that the finish of the cut with the scissors could damage the endothelium.

Dr. Victoria de Rojas: PK: we use the Hessburg-Barron vacuum trephines. DALK: we prefer a cutting trephine with controlled depth like those of Moria or Coronet.

Dr. Jaime Etxebarria: Hessburg-Barron type trephines and die trephine always from endothelial face.

Dr. Tomás Martí: For PK I use an endothelial die in the donor and the Hessburg-Barron vacuum trephine in the receiver. In the DALK, for the donor I use an artificial AC and a vacuum trephine from the epithelial side. For the receiver I use a vacuum trephine calibrated to incise at the depth previously determined by OCT.

Dr. Alberto Villarrubia: We always use the Hesburg-Barron system, although lately we are changing to the calibrated trephines of Moria. In any case, if it is a day with enough time (rare), we carve both corneas (donor and recipient) from the epithelial side and with a femtosecond laser.

6) What criteria do you use to select the trepanation diameters in the receiver and in the donor in PK? And in the DALK?

Prof. Juan Durán de la Colina: My standard diameter in both cases is 8.00 mm, both donor and receiver. I can enlarge or reduce 0.25 mm according to the corneal diameter. In eyes with a narrow chamber, risk of anterior synechiae or associated reconstructive surgery, I can increase the donor by 0.25-0.50 mm.

Dr. Toni Salvador: In both cases, donor 0.25 mm bigger.

Dr. Javier Celis: In PK I usually use a 0.25 mm larger donor graft. In cases of myopia magna in PK I use the same diameter. In cases with AC lens, angular synechia or very narrow AC I use a donor graft 0.5 mm larger. In the DALK I use 0.25 mm greater donor in all cases.

Dr. José Luis Güell: In general, 0.5 mm greater in PK and 0.2 mm in DALK. Occasionally, when I intend to roughly reduce the axial length in PK, I use 0.2 mm greater.

Prof. Jorge L. Alió: In the PK, depending on the case, our ideal diameter is 7.5-7.75 mm with disparity with the donor of 0.25. In the DALK we make diameters of 8 mm or more. In both cases we use the femtosecond laser, with “zigzag” profiles in PK and “mushroom” in DALK.

Dr. Ana Boto: With cutting of the donor by endothelial side and receptor by epithelial side. In cases of keratoconus: the same diameter. In cases of non-keratoconus and without peripheral anterior synechiae: 0.25 mm greater in donor. If you have peripheral anterior synechiae or Ahmed valve, 0.5 mm greater donor to recipient. In DALK the same diameter if the receiver is a myopic eyeball; 0.25 mm greater the donor if it is hyperopic or emmetropic.

Dr. Emeterio Orduña: For the PK I use a diameter 0.5 mm greater in donor than in receiver, but in case of DALK, usually 0.25 mm greater, especially in keratoconus with associated myopia.

Dr. Toni Sabala: In PK ≤8.25 mm, we use a diameter 0.25 mm higher in the donor. In PK ≥8.50 mm, we use a diameter 0.5 mm greater in the donor. In DALK we have the impression that the diameter of the recipient bed does not vary much after trepanation (perhaps due to the presence of the remaining stroma-DM-endothelium, which prevents "dilation"). Therefore, in DALK we always use the same donor and recipient diameter if we cut through the epithelial side, and 0.25 mm larger if the grafts are cut by the endothelial side.

Dr. Victoria de Rojas: Both in PK and in DALK, we generally use a size of 7.75 to 8.25 mm (the most frequent 8.0 mm) in the receiver’s trepanation and in the donor we use a punch 0.25 mm bigger in general, except for large-diameter transplants (10-12 mm) in which we use a donor button 0.5 to 1.0 mm larger than trepanation in the receiver. In any of the cases, the definitive choice of trepanation in the recipient is made according to the white-white and the need to remove the entire affected area. The size of receiver trepanning that we use most is 7.75 mm and if the white-white is greater than 12.5 mm, the 8.25-8.5 mm. Regarding the area of corneal involvement, it is important to consider it, especially in the following circumstances: for example, in keratoconus it is convenient to evaluate the extent of the thinned area, aided by the Fleischer ring almost always present. In case of corneal infections, it is necessary to ensure that all the affected tissue is removed, and the size of the trephination will have to be selected accordingly. In perforations with corneal lysis it is also advisable to ensure that trepanation is performed in healthy tissue, outside the lysis area, in order to suture the corneal button safely.

Dr. Jaime Etxebarria: In the receiver, trepanation centered on the pupil (in keratoconus, somewhat deviated to inferior-temporal, with somewhat larger diameters). The size, leaving 1.5-3.0 mm with respect to limbus. The donor always of the same diameter as the recipient (also in DALK, except if the keratoconus is very large, in which case donor 0.25 mm greater, to try to avoid endothelial folds), except if there is AC lens or aphakia (donor 0.25-0.50 mm larger). In children <1 year, donor 0.50 mm greater; between 1-4 years, donor 0.25 mm greater; >4 years, same diameter.

Dr. Tomás Martí: In the PK I use a donor 0.25 mm larger than the trepanation of the receiver. In the keratoconus in which I decide to perform a PK, I perform a previous ultrasound to see if the myopia corresponds to the corneal cone or if there is also an increased axial length between the lens and the retinal echo. In these cases, I decrease the residual myopia after the PK, trepanning both of the same diameter. In the DALK, I trepan donor and recipient with the same diameter, usually 8mm, and both on the epithelial side.

Dr. Alberto Villarrubia: In both cases we measure the white to white distance both horizontally and vertically of the recipient at the start of surgery. In PK we try to trepan in the receiver a window that leaves 2 mm nasally and 2 mm temporally (for example, a 12-mm horizontal white to white would correspond to a donor trephination of 8.0 mm); in the receiver, in a standard case trepanned from the endothelial side, we use 0.25 mm more. In a DALK we choose measures 0.50 mm more than in PK, despite the risk of failing and having to convert to PK, with which the possibility of rejection increases due to its proximity to the limbus.

7) In which situation in a patient with keratoconus would you currently indicate a PK?

Prof. Juan Durán de la Colina: There are certain studies that support PK in keratoconus, because of its good long-term results. I indicate it in very advanced cases. A previous hydrops does not contraindicate a DALK.

Dr. Toni Salvador: Hydrops.

Dr. Javier Celis: Only in those cases that have had hydrops and have a dense and decompensated stroma. In the rest I always try a DALK, even in cases that have had a small hydrops. In cases where a DALK is not possible because of macroperforation, I revert to PK.

Dr. José Luis Güell: In most post-hydrops situations, although occasionally I get a posterior manual lamellar dissection that I consider good enough for DALK.

Prof. Jorge L. Alió: Previous hydrops, very deep stromal opacity. Extreme corneal thinness (the latter is a relative indication).

Dr. Ana Boto: Low endothelial count or non-reversible corneal edema, previous hydrops with rupture of the central DM and very advanced ectasias (except if there is mental retardation).

Dr. Emeterio Orduña: Corneal and keratoconic hydrops with high keratometry where intracorneal segments cannot be used or where they do not achieve good vision despite optical correction (glasses or contact lenses).

Dr. Toni Sabala: Patients who have had a previous hydrops. Also, if we cannot obtain a big bubble or an adequate descemetic plane, we prefer to convert to PK, except in patients with significant mental retardation, Down’s syndrome and patients with severe atopy, in whom it is interesting to perform a DALK although the dissection plane be pre-descemetic.

Dr. Victoria de Rojas: In cases with endothelial involvement (some keratoconus may present in association with Fuchs' dystrophy or posterior polymorphus dystrophy). If there are deep scars that affect the DM in the visual axis, depending on the cases, valuing advantages of a DALK with the possibility of slightly diminished visual acuity, compared to penetrating keratoplasty with better visual acuity. Most of the time, we lean towards the first option, talking to the patient. Some of these scars are a sequel to previous hydrops. In these cases, in which initially we indicated PK of first choice, we currently indicate DALK with a modified manual technique, leaving for the end the dissection in the area of the previous hydrops. If there is a prior history of hydrops, the big bubble technique cannot be applied due to the high risk of tearing the DM in the area of the previous breakage of the hydrops that would require reconversion to PK.

Dr. Jaime Etxebarria: I always try DALK except if there has been central hydrops.

Dr. Tomás Martí: In very pronounced cones, with great elongation of the DM, the results through DALK are not satisfactory due to the presence of folds, and in some cases it is better to perform a PK in the first intention.

Dr. Alberto Villarrubia: Initially, only in patients with hydrops. In very advanced cones, we know that the possibility of perforation is very high, but even so, we always try.

8) What is your favourite suture technique for PK? And for DALK?

Prof. Juan Durán de la Colina: Eight independent sutures and a continuous suture of 16 loops with nylon 10-0. In vascularized cases I use 16 independent sutures.

Dr. Toni Salvador: No neovessels: 8 independent and continuous suturing. With neovascularization: 16 independent points.

Dr. Javier Celis: In PK in eyes without problems of limbal insufficiency/neovessels I use 4 independent sutures and a continuous one of 16 loops. If there are neovessels or limbal insufficiency, I prefer 16 independent sutures. For the DALK I use the same criteria using continuous suture or 16 independent stitches according to the state of the recipient bed. In it, I take less depth in the donor graft than in the receiver, to try to achieve a perfect congruence between the donor and receiver Bowman’s and to avoid that there are steps left.

Dr. José Luis Güell: In both cases, nylon 10-0 independent sutures (usually 16, and in children 24), inverse knots 1-1-1 (the initial 4, 3-1-1).

Prof. Jorge L. Alió: In both cases, the continuous double torsion anti-torsion suture.

Dr. Ana Boto: Regular receiving bed: anti-torque continuous suture plus 4-8 interrupted sutures at times. Irregular bed, vascularization, inflammation, etc...: interrupted sutures.

Dr. Emeterio Orduña: On both occasions I use 16 independent sutures of 10-0 nylon.

Dr. Toni Sabala: For PK we use discontinuous sutures: 20 independent ones in grafts greater than ≥8.50 mm, and 16 in grafts ≤8.25 mm. For DALK we use combined sutures: 8 independent ones and a continuous suture of 16 loops (two between each independent one). We generally use large grafts of ≥8.50 mm in DALK. In these we use continuous suture because the stability of the graft during the suture is much greater than in the PK and can be easily manipulated during the following three weeks. On the other hand, I think it is almost more important to suture the DALKs well because they tend to have more incongruities and steps, while the PKs adapt better to the receiving window.

Dr. Victoria de Rojas: Our suture technique of choice in both PK and DALK is with 16 independent 10-0 nylon sutures. In the second, it is important that the puncture of the needle comes somehow less deep in the graft than in the recipient, to avoid the protrusion of the donor button with a step on the edge, which causes epithelialization and astigmatism problems. We enter about 2/3 in the donor and as deep as we can – avoiding drilling the DM – in the receiver. In a large diameter transplant, more stitches are needed. We prefer independent sutures in case it is necessary to remove some (early vascularization, sutures close to limbus, loose sutures, etc.).

Dr. Jaime Etxebarria: In PK, 16 independent sutures (I do not do continuous) to be able to play better with astigmatism. Entering 70% in donor and recipient. In DALK, 16 independent sutures for the same reason. Entering 50% in donor and 100% in recipient.

Dr. Tomás Martí: In the PK I always perform independent sutures; it is especially important to choose this type of suture in patients at high risk of rejection. In the DALK, in which obviously there is no danger of leakage, I perform a continuous suture in the form of isosceles triangles to minimize the torsional effect of the same.

Dr. Alberto Villarrubia: For both cases, independent sutures. Exceptionally, in some DALK with “cold” eye, I perform continuous anti-torque suture after 8 independent stitches.

9) In which cases do you think it is indicated to perform superficial anterior lamellar keratoplasty (SALK)?

Prof. Juan Durán de la Colina: The perfect indication is an anterior dystrophy (like Reis-Bücklers), if the lesion is superficial (<150 μm) and the topography is homogeneous.

Dr. Toni Salvador: Leukomas less than 250 μm deep, as long as it remains 150 μm of depth, and not very irregular (including post-adenoviral). Anterior dystrophies.

Dr. Javier Celis: Currently I do not perform this technique.

Dr. José Luis Güell: As long as we do not have OCT control with an endothelial reference surface in our femtosecond laser unit, in practice, I only indicate SALK in those situations where the opacity and/or irregularity is limited to the lenticule after LASIK surgery.

Prof. Jorge L. Alió: I never perform SALK. The visual results have been bad.

Dr. Ana Boto: Central white opacities of <100 μm in depth and regular surface.

Dr. Emeterio Orduña: I have used it very rarely for reconstructions of the anterior part of the cornea, probably waiting for a DALK according to the visual results, which in my experience are frustrating.

Dr. Toni Sabala: The indications are very few. Superficial leukoma, less than 150 μm deep, with little or no irregular astigmatism.

Dr. Victoria de Rojas: In opacities of the anterior stroma (affectation between 150-200 μm) not susceptible to treatment by therapeutic photokeratectomy or in which this has already failed, with minimum pachymetry of 500 μm.

Dr. Jaime Etxebarria: I never perform it since in my experience they look anatomically very good, but functionally they are inferior to a DALK.

Dr. Tomás Martí: Currently I do not perform SALK. Theoretically, it would be indicated in very superficial pathologies, like adenoviral infiltrates, or very superficial dystrophies, but in my experience the vision is much worse than in the DALK.

Dr. Alberto Villarrubia: We have never performed it for the purpose of visual rehabilitation, only with tectonic purposes in a very peripheral descemetocele or when there has already been a perforation. In the latter case, if the perforation is central and it is an eye with visual potential, we directly perform PK.

10) What is your technique of choice for SALK and why?

Prof. Juan Durán de la Colina: With femto-seconds laser; in the donor I use the Barron’s chamber. I perform a diameter of 7.5 mm and a depth of not more than 200 μm, both in donor and in receiver. I do not place sutures, only a CL for 7 days.

Dr. Toni Salvador: Manual microkeratome with heads of different thicknesses. It is the system that I have.

Dr. José Luis Güell: Preparation of a donor lenticule with the manual microkeratome, formerly with a whole eyeball, currently with artificial AC and suture thereof after manual extraction of the recipient's damaged lenticule.

Dr. Ana Boto: Keratectomy with a femtosecond laser, wait for the epithelization and topographic result before deciding whether to associate a corneal graft. I have only performed it in two cases with superficial opacity due to adenoviral keratitis infiltrates.

Dr. Emeterio Orduña: I perform SALK assisted with microkeratome, Amadeus system.

Dr. Toni Sabala: I only have experience with the microkeratome We always use the 150 μm head. I first cut the donor cornea, with a lot of serum pressure in the artificial AC to obtain a larger donor anterior lamina. Then I cut the receiver with the Moria suction rings, with the same microkeratome and head. We have three types of rings according to the corneal diameter of the receiver. Then I measure the diameter of the resultant bed in the receiver and trepan with a die of the same diameter the lamellar donor graft.

Dra. Victoria de Rojas: The one described by Hsu in 2008 and modified by Fogla in 2014 through microkeratome in two steps. A corneal flap with hinge is created with a microkeratome in the receiver of 9 mm in diameter and about 140-200 μm in thickness depending on the depth of the affectation, which is replaced in its place. After 4-6 weeks, the donor cornea is mounted in an artificial chamber and a free lenticule is carved by a microkeratome with the same parameters of thickness and diameter as in the receiver, which is then placed in a Barron’s trepan to cut it to a diameter of 7 mm. You obtain a button with vertical edges and that size. In the receiver, a partial trepanation is performed with a Barron’s trepan of 7 mm in diameter on the previously cut and replaced flap. The central 7 mm button thus obtained is removed and the button of the same diameter and thickness and vertical edges of the donor is placed in its place. The edges are dried, and a therapeutic CL is applied, which is removed in 2 weeks. Although the femtosecond laser allows to cut exactly the same diameter and vertical edge in donor and receiver, in the presence of opacities, the quality of the cut in the bed can be worse than that of the microkeratome, due to the interference of the opacities in the performance of the laser, which can lead to uncut areas. The microkeratome technique in two steps solves these drawbacks.

Dr. Alberto Villarrubia: Partial trepanation of about 2/3 of the corneal thickness and centered on the perforation or descemetocele, manual dissection of an anterior keratectomy at that level, and suture (with the knots always tight) of an anterior sheet if a donor that we have used for ELK/DSAEK.

11) What supplementary exams do you use to decide between a SALK or a DALK?

Prof. Juan Durán de la Colina: OCT and topography are essential.

Dr. Toni Salvador: Calculation of thickness of the lesion with OCT and corneal topography.

Dr. José Luis Güell: Clinical history, biomicroscopy and, in particular, high definition OCT to limit the extension of the lesion (intra or extra lenticular).

Dr. Ana Boto: Anterior segment OCT.

Dr. Toni Sabala: Corneal OCT to measure the depth of the lesion. Pachymetric map and ultrasonic central pachymetry. Topography to assess irregular astigmatism. Endothelial counting if possible.

Dr. Victoria de Rojas: The depth of stromal involvement evaluated by OCT.

Dr. Alberto Villarrubia: None. We do not perform SALK with optical purpose and we only do it in the aforementioned reconstructive cases, which do not need any complementary tests.

12) What is your technique of choice for DALK and why?

Prof. Juan Durán de la Colina: I try to perform a big bubble technique (BB), but I often require manual dissection.

Dr. Toni Salvador: Dry bubble technique according to Rama, monitored with perioperative pachymetry (residual stroma <50 μm). Low rate of conversion to PK in relation to that of the BB.

Dr. Javier Celis: It depends on the basic pathology and the patient's conditions. In cases with high visual demand and good vision in the other eye I always try to use a descemetic technique and among them I opt for the viscodissection. In the leukomas I do a study with OCT. If the opacity is deep, I attempt a descemetic technique. If the leukoma does not reach very deep planes, I perform a predescemetic technique with spatulas of Melles. In paediatric cases or only eyes, I also opt for a predescemetic technique and thus avoid a possible conversion to a PK.

Dr. José Luis Güell: My technique of choice is the viscodissection. The advantages are greater transparency of the corneal tissue during and at the end of the injection (when we get to surpass, as far as the level of dissection allows, the limit of the vertical incision) that allow us to see in detail the structures of the AC and provides a greater safety at the time of initially opening the bubble as well as during the dissection of the same. In those cases where we suspect a greater fragility of the posterior wall (for example in hydrops or when it is impossible to get the bubble), I prefer a manual layer dissection, trying to get as far back as possible.

Prof. Jorge L. Alió: BB technique after manually dissecting more than 50% of the stroma, after performing a vertical lateral cut with femto-second laser.

Dr. Ana Boto: If there is a severe opacity and inability to estimate the corneal thickness with OCT or pachymetry, manual dissection technique. If I can estimate thickness with OCT or pachymetry, big bubble technique locating the injection plane according to pachymetry.

Dr. Emeterio Orduña: I usually use the BB technique, although I have used the sclero-DALK (described by me) on several occasions, in which the predescemetic space is reached through a scleral approach with a deep flap reaching until the Schlemm's canal, similar to an EPNP, and from there I perform visco-dissection of the DM. It has the disadvantage of damaging the corneoscleral limbus, compromising future filtering surgeries.

Dr. Toni Sabala: I use the BB technique with Donald Tan’s modification, with a partial lamellar keratectomy prior to the injection of air. I prefer this technique because the percentage of obtaining the BB is higher, perhaps because it is assured that the air injection is very deep. It also makes it much easier to see what happens in the AC when performing BB, and the partial keratectomy is easier and less risky when performing it before the BB.

Dra. Victoria de Rojas: The BB technique. Although the literature and our personal experience have shown that, if the residual bed is less than 20% of the total pachymetry, the visual results in the long run are equal to those of a PK, the truth is that the visual recovery is quicker if you get a dissection at the level of the DM that if residual stroma remains, however little. Therefore, we try the BB technique with a modification introduced by Ganen4 and Coscarelli5, which consists in the creation of a stromal pocket outside the partial trepanation at a depth of 85% of the pachymetry in that point. In this pocket the spatula of Sarnicola is introduced to the center of the cornea, by means of which we inject air. This technique has greatly increased the rate of obtaining BB in our hands. If we cannot create a BB even after repeating this maneuver in non-pneumatized areas, we continue with manual dissection of the stroma up to the DM. To do this, we introduce Sarnicola’s spatula into the previously created tunnel and cut the tunnel roof with a 15° knife above it. We thus access a plane very close to the DM. With the forceps we hold the upper part of the stroma and with the spatula we dissect a tunnel perpendicular to the first to make a dissection type divide and conquer. The level of dissection we try depends on the cases. If they are of low risk of rejection such as keratoconus, we risk more to reach DM, which we achieve through this system in most cases. In cases with vascularized cornea or other characteristics of high risk of rejection, we prefer not to risk so much in the dissection to avoid a possible perforation that forces us to convert to PK. In cases with anterior corneal perforation or hydrops, we perform manual dissection from the beginning.

Dr. Jaime Etxebarria: I always try the BB, without previously removing a sheet of cornea. If I do not get it, I work layer by layer until I get full transparency "without granulation" by putting a drop of BSS on the cornea.

Dr. Tomás Martí: I use the BB technique. In cases where I cannot get it, I use a layer by layer technique until I can locate the predescemetic space.

Dr. Alberto Villarrubia: We have left the Melles’ technique (manual dissection) for the cases in which we are interested in ensuring success as much as possible, that is: single eye and Down syndrome. Sometimes we go directly to the manual dissection if we know that the possibility of piercing after a BB is very high: very curved corneas, dense scar, and if we are very interested in having a large graft. For the rest of the cases, we use BB, although lately we are performing a "small-bubble" technique assisted with femtosecond lasers in highly selected cases, with promising results.

13) What is your attitude towards an intraoperative microperforation in DALK?

Prof. Juan Durán de la Colina: I try to complete it, leaving the perforated area for the end. I rarely transform to PK. In cases of low risk and with good donor cornea I look for a predescemetic plane; otherwise, I am more conservative.

Dr. Toni Salvador: Finish the surgery and tamponade with air, prior peripheral iridotomy.

Dr. Javier Celis: If I can conclude the dissection of the anterior stroma and the AC is maintained with an air bubble, then I finish the surgery as in a normal case. If I cannot complete the dissection or the perforation is so large that the air escapes when I insert it into the AC, then I revert to a PK.

Dr. José Luis Güell: It is sometimes compromising to describe what a microperforation is, but once observed and whatever its size (which is the most important), I try to continue my dissection slowly and with the AC moderately collapsed, always trying not to enlarge the opening. Usually, even relatively large perforations do not prevent the end of surgery, but in all cases I perform peripheral iridectomy and leave a 20% SF6 bubble to facilitate adhesion and decrease the possibility of forming a double chamber in the immediate postoperative period.

Prof. Jorge L. Alió: If the induction of air in the AC is blocked by the microperforation, we consider it as such. If air comes out and no bubbles are retained, we transform to PK since macro perforation leads to a very long postoperative period with corneal edema and poor vision.

Dr. Ana Boto: I reserve that area for the end, leaving a little stroma over it.

Dr. Emeterio Orduña: I continue the dissection from another point and I try to continue with the surgery if possible. I leave an air bubble at the end with postoperative control of a pupillary block in a similar way to a DEK/DMEK.

Dr. Toni Sabala: Depends on how advanced the dissection is. If it is very at the beginning it can hinder much the surgery although I try to continue with it. I try to leave air in the AC to avoid a double chamber.

Dr. Victoria de Rojas: If it is a micro-perforation that keeps air in the AC, we do not reconvert and continue with the dissection leaving the microperforation area for the end, going around it if necessary. If it is a macroperforation and it is not possible to maintain an air bubble in the AC, we convert to PK. At the moment the perforation happens, and we introduce air into the AC, the pressure of it must be low, since it could convert a microperforation into a macroperforation.

Dr. Jaime Etxebarria: I try to finish the surgery by following another way than the microperforation. Always leave air in AC as if it were a DEK/DMEK.

Dr. Tomás Martí: I try to block the microperforation with air to continue the intervention. I leave a generous bubble of air in the postoperative period.

Dr. Alberto Villarrubia: I try to continue manually if it really is a microperforation and that it is also out of line of sight. Oftentimes, it is a perforation that does not allow us to finish the surgery and we have to reconvert to PK.

14) And before an endothelial detachment in the postoperative period of a DALK?

Prof. Juan Durán de la Colina: If I observe an excessive compression of the sutures, the possibility of spontaneous application is less, so I put on air. I rarely introduce SF6 at 20%. If I am interested in a large bubble, I expand the pupil to avoid pupillary block.

Dr. Toni Salvador: Air tamponade and peripheral iridotomy.

Dr. Javier Celis: If double chamber is observed and the DM presents undulations, I do air injection in AC. This usually produces an immediate reapplication of the DM and disappearance of the edema in the graft. If the DM is separated and rigid, the air/gas injection is usually not effective. It may be due to viscoelastic residues in the interface, in which case it will be necessary to remove it in the operating room. If there are no remains in the interphase, I wait several weeks and if the DM remains rigid and without applying to the stroma, then I propose doing some release in the DM and gas injection (SF6 at 20%).

Dr. José Luis Güell: If I consider that it has an extension, shape or location that does not allow a spontaneous reapplication with topical hyperosmolar treatment, I inject SF6 at 20% after checking the permeability of the iridectomy. If the latter does not exist and the corneal transparency does not allow me to perform it with Nd: YAG laser, I only inject air and keep the patient dilated to the maximum.

Dr. Ana Boto: If it is due to mild inflammation, I increase the corticoid therapy. If not, air injection in the AC and positioning in the operating room.

Dr. Emeterio Orduña: I do reinjection of air in consultation and I maintain the patient in supine position for 1 hour in a similar way to the DEK/DMEK. If re-adaptation is not achieved with 2-3 air injections, I use SF6 at 20%.

Dr. Victoria de Rojas: We have to differentiate two situations: (1) If a microperforation has occurred, it is most likely that the aqueous humour continues filtering into the space between the DM and the graft. To prevent this situation, it is best to leave an air bubble or SF6 at the end of the surgery, with the well dilated pupil when leaving the operating room to prevent a pupillary block. If a small double chamber is produced and the DM is close to the graft, we wait a week because sometimes it resolves spontaneously. If not, we inject SF6 at 20%. We evaluate the extension and location of the double chamber with OCT and we cite the patient in the early morning to follow it up after gas injection (discarding pupillary block), which we perform in the slit lamp because it allows to better locate where we are introducing the needle and avoid doing it in the double chamber. We inject the air (about 0.15 ml) in such a way that there is a bubble of about 2/3, which leaves free the lower margin of the dilated pupil when the patient is not in the supine position. We verify the perception of light and keep the patient lying down in the clinic. In 2 hours, the improvement or even resolution of the double chamber can be observed with a decrease in corneal edema. We monitor the patient for a couple of hours more, and if no blockage occurs, the patient is sent home. (2) If we are not aware that a micro perforation has occurred, the double chamber may be due to the lack of congruence of the curvature of the donor button and the DM of the receiver, as may occur in an advanced keratoconus. This double chamber usually resolves spontaneously, and the DM is applied on the donor button, although folds may occur in it that could affect visual acuity if they are in the central area. If the double chamber is not resolved, we inject SF6. If the DM of the receiver has a flatter curvature than that of the posterior face of the donor button, it can also give rise to a double chamber which, if not solved, will require injection of SF6. If this fails, we would resort to the circumferential resection of the DM except in 2 hours higher, with subsequent injection of SF6, as described by Sarnicola.

Dr. Jaime Etxebarria: Air in AC if it is phakic. If it dettaches again or in pseudophakic, SF6 at 20%. If it re-detaches, I try to remove sutures that I believe may be the cause of bad corneal donor-recipient apposition.

Dr. Tomás Martí: It depends. If the DALK was descemetic and there was no perforation, it will probably reapply spontaneously. If a stroma remnant was left and there was perforation, it probably will not be reapplied even if we inject air or SF6. The cases that, in my opinion, clearly benefit from the injection of air are those in which there was microperforation, but the detachment is only of the DM without stroma, in which fibrosis prevents the adherence.

Dr. Alberto Villarrubia: We remove 3-4 sutures and introduce an air bubble in the AC. With a tensioned eye, we suture the cornea and leave the patient in the operating room for half an hour. Then, the patient leaves the surgery with a 1/2-1/3 air bubble. If we fail in this first attempt, we do not perform a second; we wait around a month and, if it has not been solved spontaneously, we reconvert to PK.

15) What is your algorithm for correction of post-keratoplasty astigmatism (PK or DALK) once the sutures are removed?

Prof. Juan Durán de la Colina: Exceptionally, I use arcuate incisions. They are unpredictable and unstable. In high or irregular astigmatisms, I use CL, which is easier in bilateral cases or with previous keratoconus. In unilateral cases, provided that the rest of the eye structures are in good condition, I treat them by means of refractive surgery: LASIK or phakic (or pseudophakic) lens.

Dr. Toni Salvador: Initially contact lenses (RPG, scleral, toric). Glasses or PRK if there is intolerance and the astigmatism is <4 dioptres (D).

Dr. Javier Celis: It will depend on the conditions of each case. In astigmatisms up to 3D, I indicate correction with glasses. In the elderly, I always propose correction with contact lenses first. If it is a phakic patient and the astigmatism is more or less regular and stable, I use cataract surgery with a toric lens. If I do not have the possibility of an intraocular lens, I usually use intrastromal segments or arcuate incisions on the curved axis inside the graft with compression sutures on the flat axis. In cases of very high astigmatism, I resort to wedge resections. If the ectasia is very pronounced, as in late recurrences of keratoconus, I consider a new keratoplasty (tuck-in lamellar keratoplasty). I do not have experience in the correction with PRK or LASIK.

Dr. José Luis Güell: In principle I will try to correct it with glasses and/or contact lenses. The new models of the latter allow us to manage the majority of our patients even those with high residual astigmatism. If for any reason (intolerance, discomfort, unavailability to carry them), this rehabilitation is not possible, as long as 6 months have passed after suture extraction and we have 2 topographies and stable refractions separated by 3 months, we will consider surgery. Among them, my favourites would be: (1) LASIK if astigmatism <4 D and spherical equivalent (SE) <+2.00. (2) Arcuate keratotomies with the femtosecond laser if astigmatism >4D and SE close to 0. (3) Phakic lens implant (my favourites are Artisan or Artiflex) if the SE is >5D and the anatomy of the anterior segment allows it. These are my general recommendations, but each case must be considered individually.

Dr. Ana Boto: If there is good vision with glasses or contact lenses (CL), even with high astigmatism, I do not perform any procedure. If astigmatism is not tolerated and there is no possibility of using CL: arcuate incisions with femto-seconds laser (with compression sutures if the topographic cylinder is >6-8 D). If the astigmatism is very high and not corrected with arcuates, wedge resection and new suture. If the receiver periphery is very thinned or there is an ectasia of the peripheral button, I perform a peripheral lamellar graft in crescent.

Dr. Emeterio Orduña: I tend to handle it with relaxing arcuate incisions inside the graft and compression sutures to reduce it. According to the age of the patient and whether or not he is pseudophakic, I use toric IOLs for residual astigmatism if I consider it stabilized (the truth is that on few occasions and not with good results in the correction of the cylinder). I have no experience in laser refractive correction.

Dr. Toni Sabala: In astigmatisms <4D we prescribe glasses. On top of that we make arcuate incisions in the graft. In irregular astigmatisms we try to adapt contact lenses permeable to gas. If the patient has a cataract or more than 50 years, we value performing a lens surgery with toric IOL.

Dr. Victoria de Rojas: Once the sutures are removed, if the astigmatism is equal to or less than 3 D, we perform correction with glasses or contact lenses. In higher astigmatisms, we resort to arcuate incisions or implanting intracorneal segments according to magnitude and degree of irregularity. Another option if pachymetry allows it, is the correction through LASIK or PRK. If these measures do not achieve correction or are not suitable for a particular case, we resort to toric IOL implantation. In phakic eyes we would implant a toric phakic IOL, preferably in a posterior chamber (ICL or IPCL secondly according to correction range). In a pseudophakic eye we would implant a toric IOL in sulcus (secondary piggy-back). If the eye presents a cataract and we have to operate it, a primary piggy-back is preferable, with a spherical IOL in bag and a toric in sulcus. This would allow replacing or removing the toric IOL in those cases in which, for any circumstance, a new graft was necessary and the astigmatism changed.

Dr. Jaime Etxebarria: If the astigmatism is <4D and it is regular: glasses, contact lenses, toric IOL in bag or for phakic (usually in iridian support). If it is <4D but does not achieve good vision with glasses, I advise CL. If it is >4D, arcuate incisions and sutures in the flatter meridian. I think the key is to make a diagnosis as accurate as possible of what has happened: perform a topography, a careful examination of the edges of the scar by slit lamp and sometimes OCT. If there has been a dehiscence in some quadrant, it is useful to open it and suture again, trying to obtain a good apposition of the edges. In the less frequent cases in which the astigmatism appears in perfectly coaptate corneas and can be attributed to an oval trepanation or other causes, the correction can be attempted by means of LASIK. In these cases, it is convenient to do it in two stages, first the cut with the microkeratome, which when affecting the 360o of the scar can modify astigmatism noticeably, and after revaluating the residual ametropia, we can perform the laser ablation with good results.

Dr. Alberto Villarrubia: Glasses if the patient tolerates them, has good corrected vision and there is no great ametropia. Otherwise we try CL gas permeable. In any case, we usually offer the patient the right surgery to correct his ametropia: PRK with mitomycin C, phakic IOL (ICL), refractive lensectomy with toric IOL, or a combination of the former with one of the latter. If there is a lot of irregular astigmatism and it does not tolerate gas permeable CL, we offer the patient the possibility of ablation guided by topography, with which we have obtained moderately acceptable results.