Author: Ameen Marashi, MD

History

Documentation of age, duration of visual loss is essential, which includes blurred vision, micropsia, metamorphopsia, scotoma, along with detailed familial and ocular history such as previous axial length [1]. The medical history should be investigated for systemic diseases such as Marfan syndrome, Down syndrome, Stickler syndrome, etc.

Ocular Examination

A list of ocular examination should set

1) Best-corrected visual acuity (BCVA) for near and far is an essential step that can perform by a trained optometrist or certified ophthalmologist to document the visual impairment, as myopia -6.00 diopters and more considered as pathological myopia[1].

2) A slit-lamp examination done with a thorough exam of clarity and regularity of the cornea and conjunctival abnormality such injection of conjunctival vessels should be documented. Any other inflammations of the conjunctiva or eyelids documented, along with iris exam and crystalline lens exam to rule out cataract or intraocular lens (IOL) to document the position and clarity of the posterior capsule.

3) Intra Ocular Pressure (IOP) documentation is essential as high IOP may be associated with pathological myopia and patients with glaucoma history; in cases of increased IOP, then gonioscopy is necessary, any associated mild to moderate glaucoma can be managed with topical antihypertensive eye drops.

Note when high IOP spotted a corrected IOP documented after central

corneal thickness measurement. High IOP is a risk factor for RRD.

4) Bilateral dilated fundus exam is an essential and detailed examination of the optic disc, macula, posterior pole, a mid-peripheral and peripheral retinal exam with specialized indirect wide-field lenses using

slit-lamp biomicroscopy or indirect ophthalmoscopy with scleral indentation to document the following:

· Optic disc crescent or tilted optic disc

· Staphyloma, which is outward protruding all eye globe layers, which has five different types [2]:

1. Wide macular

2. Narrow macular

3. Peripapillary

4. Nasal

5. Inferior

6. And other compound forms of staphyloma

· Tessellated fundus changes.

· Diffuse chorioretinal atrophy, where fundus looks ill-defined grayish-yellow chorioretinal atrophy as only large choroidal vessels are visible [3] .

· Patchy chorioretinal atrophy features well defined of all choroid and

outer retinal tissue atrophy with only inner retinal tissue with sclera [3] .

· Macular atrophy.

· Lacquer cracks, which are splits in Bruch's membrane, appear as yellowish lines [4] .

· Subretinal bleeding may happen as a complication of Lacquer cracks

(without the presence of CNVm) or as a complication of CNVm

· Myopic choroidal neovascular membrane (CNVm), which appears as well defined with minimal or no exudation and less bleeding at the edge of patchy atrophy

· Fuchs' spot is a result of RPE proliferation in CNVm scar phase

· Epiretinal membrane.

· Macular hole.

· The presence of peripheral retinal holes, tears, or detachment should be ruled out.

· Posterior vitreous detachment or syneresis.

Diagnostic tests

Fundus images

It is an essential tool to document the progression of pathological myopia as pathological changes increase with age and time as patchy chorioretinal atrophy appears over diffuse chorioretinal atrophy nevertheless, Lacquer cracks may widen and induce patchy chorioretinal atrophy. However, Lacquer cracks may precede the development of CNVm, which may proliferate at the edge of patchy chorioretinal atrophy, and the later, when it regresses, it forms scar-forming Fuchs’ spot and then develop atrophy that will surround the Fuchs’ spot [5].

Fundus image helps to classify myopic degeneration as it documents the presence of tessellated fundus to diffuse & patchy chorioretinal atrophy to macular atrophy and presence of Plus lesions such as Lacquer cracks, myopic CNVm, and Fuchs’s spot [3].

Optical Coherence Tomography (OCT)

SD-OCT may show difficulties in capturing high-quality images for myopic patients due to the short wavelength of the laser beam and pathological myopia best studied with OCT using SS-OCT.

OCT is a necessary ancillary test to diagnose patients with myopic degeneration, which shows the following characteristics:

· Changes in retinal contours that exhibits straight sclera with curvature slope toward the optic nerve, concave shape symmetrical (both sides of sclera curved posteriorly symmetrically around the fovea) or asymmetrical around the fovea, or irregular curvature [6].

· Rarely the macula looks convex creating dome-shaped myopic maculopathy, which may be associated with subretinal fluids. [7].

· In diffuse chorioretinal atrophy, the choroid thinned and maybe only a large choroidal vessel remains under the RPE.

· In patchy chorioretinal atrophy, the choroid is absent along with photoreceptors layers and RPE, and only sclera and inner retinal tissue are visible.

· In myopic CNVm, there would be subretinal hyperreflective material that may not show signs of exudation, such as subretinal or intraretinal fluids. Thus, the OCT can’t differentiate the subretinal bleeding from CNVm. Subretinal fibrosis has more chance to appear in a larger and thicker CNV lesion. In cases of the wider area of CNV leakage on FFA and cases of advanced macular myopic degeneration [15].

· OCT is the tool of choice to diagnose myopic traction maculopathy, which presents epiretinal membrane as a hyperreflective band causing vitreomacular traction with cystoid macular formation mostly in the inner retinal layers in tubular form inducing schisis where in severe cases lamellar or full-thickness holes may even form macular detachment.

OCT is important to assess treatment efficacy for CNVm or progression post follow up, and surgical success for myopic traction vitreomacular traction has the following features:

· Reduce the size or resolved subretinal CNVm

· Release of macular traction induced by epiretinal membrane

OCT angiography

In cases of myopic CNVm, OCTa can clearly show the subretinal choroidal neovascularization in the outer retinal slab, which can be well- circumscribed with hyporeflective background and with hyperreflective borders. As branching, looping, and anastomosis of the vascular network may indicate an active CNVm [14].

OCTa can be very useful to follow up CNVm regression post intravitreal injection of Anti-VEGF.

Fluorescein Fundus Angiography (FFA)

FFA has unique characteristics in diagnosing pathological myopia such as:

· FFA may show window defect and choroidal filling defect with scleral staining in patchy chorioretinal atrophy.

Lacquer cracks appear hyperfluorescence (linear window defect), in contrast to myopic stretch lines, which appears hypofluorescence, which appears in FAF as increased autofluorescence and is a sign of RPE proliferation [8].

· FFA is the tool of choice to diagnose the presence of myopic CNVm as it has well-defined hyperfluorescence borders, which may show minimal or no leak in all phases of angiography. Still, subretinal hemorrhage may induce blocked fluorescence, and thus FFA is beneficial to rule out the presence of CNVm in cases presented with subretinal blood.

Note that the physician should obtain signed consent explaining the rare complications of FFA, including death 1/200000, and FFA facility should have an emergency plan in situ

B & A-scan

B-scan is very useful in cases with media opacities such as dense cataract to rule out retinal detachment or peripheral retinal tears along with the ability to evaluate posterior vitreous detachment and vitreous syneresis.

A-scan is a vital tool to record the axial length changes and to monitor the progression of myopia as an axial length above 26.5 mm, considered as pathological myopia [1].

Managing patients with pathological myopia

Treatment options

Low concentration Atropine

Low concentration of atropine used to slow the progression of myopia in children, there are multiple doses suggested, such as 0.05. 0.025, and 0.01 %

VEGF Blockade agents

Is only indicated in cases complicated with myopic CNVm [9], the injection should be carried out in sterile condition where injection site is prepared by disinfecting the skin using povidone-iodine 10%.

After installing topical anesthesia, and the conjunctiva disinfected using povidone-iodine 4%.

The injection is carried out after placing sterile drape and lid speculum isolating eyelashes in the superior temporal quadrant.

Injection site measured with calipers 4 mm from the limbus in phakic patients and 3.5 mm in pseudophakic patients, Injection site measured with calipers 4 mm from the limbus in phakic patients and 3.5 mm in pseudophakic or aphakic patients. A 30-gauge half-inch needle is used to inject VEGF blockade agents then a cotton tip applicator is placed over the injection site to prevent the reflux of fluid.

Laser photocoagulation

Considered in cases of symptomatic peripheral retinal holes or tears The laser can be applied under local anesthesia using slit-lamp microscopy or indirect ophthalmoscopy, usually a spot size between 200 and 500 μm with a power enough to induce desired retinal burn with duration 0.1 to 0.2 seconds. Three rows of confluent gray to white laser applications (forming a zone 500 to 1000 μm wide) should be applied around the break or lattice degeneration; however, it is essential to apply laser anterior to retinal break after applying the laser to posterior and lateral edges prevent extension of break and in cases of retinal dialysis the anterior horns of dialysis should be lasered.

Usually, the chorioretinal adhesion happens faster than cryotherapy so it is advisable to have headrest when there are subretinal fluids for days.

Complications are rare as the laser may induce corneal burns, iatrogenic retinal holes, or hemorrhages in cases where increased power is used.

Pars Plana Vitrectomy

Indicated for cases of retinal detachment or myopic traction maculopathy with ILM peeling sparing the fovea to avoid damaging it by peeling the ILM away from the center and as it becomes close to the fovea, ILM peeling start from a new site till completing the entire macula leaving only the center of fovea [10].

Treatment plan

In cases of high myopia in childhood

Topical low concentration of Atropine 0.05% once a day at bedtime [11] and myopic progression reevaluated every five years using axial length and refraction.

In cases of myopic CNVm

Intravitreal injection of VEGF blockade agents considered as a treatment of choice [9] when the presence of CNVm established using OCTa, or FFA, usually one injection is needed and followed up monthly and reinjecting only required if CNVm not regressed, however in myopic CNVm intravitreal injection of Anti-VEGF may offer a short term improvement of vision [12], but a long term is unknown as CNVm related atrophy may develop later and cause reduced vision [13].

In cases of symptomatic peripheral tears or/and holes

Laser photocoagulation retinopexy around peripheral retinal tears or/and holes by applying three rows of confluent burns.

In cases of macular hole, myopic traction maculopathy or retinal detachment

Pars Plana vitrectomy indicated with ILM peeling sparing the fovea for cases of myopic traction maculopathy [10] and in cases of macular hole; however, in cases of retinal detachment, a Pars Plana vitrectomy with subretinal fluid drainage and laser retinopexy around retinal tears and hole with gas or silicone oil tamponade required.

Follow up and prognosis

- The pathological myopic degeneration increases with age in about 40% of patients; children with high myopia may not reveal pathological retinal findings related to myopia.

- Lacquer cracks may widen and progresse to patchy chorioretinal atrophy and myopic CNVm.

- Myopic CNVm progresses to scar phase without treatment then to an atrophic phase, which will reduce vision even in light of Anti-VEGF treatment.

Add your scientific contribution

These guidelines were reviewed and updated in January 2021