These days refractive error can be corrected by reshaping cornea through ultraviolet rays (193nm) called excimer laser. LASIK and PRK are famous refractive procedures. They can correct upto -8 diopters of myopia, upto 3 diopters of astigmatism and 4 diopters of hypermetropia. 

Lasers Used in Ophthalmology

2.      Nd:YAG (Neodymium–Yttrium– Aluminium–Garnet)1064 Posterior capsulotomy, iridotomy, vitreolysis

3.      Frequency-doubled Nd:YAG 532 Retinal photocoagulation, cyclophotocoagulation

4.      Argon green 514 Trabeculoplasty, iridoplasty, pupillomydriasis, retinal photocoagulation*

5.      Diode laser 800 Retinal photocoagulation

6.      Krypton red 714 Retinal photocoagulation through vitreous hemorrhage

7.      Excimer (argon fluoride) 193 Photorefractive keratectomy (PRK), phototherapeutic keratectomy (PTK), LASIK, LASEK

8.      Femtosecond laser (neodymium-glass) 1053 Femtosecond laser assisted refractive surgery, lamellar and full thickness corneal transplants

refractive surgery: 

(i) radial keratotomy whereby radial incisions are made in the cornea;

(ii) arcuate keratotomy by arc shaped incisions in the steeper or more myopic meridian to reduce astigmatism;

(iii) keratomileusis, in which tissue is resected and modified in shape before replacement

(iv) epikeratophakia, whereby donor corneal tissue is attached to the host cornea after removal of the epithelium.

(iv) excimer laser refractive surgery

1. photorefractive keratectomy (PRK) the surface of the cornea is ablated by the laser leading to a flatter cornea to

neutralize myopia. 

2. LASIK or laser-assisted in situ keratomileusis in which a superficial circular flap of epithelium and stroma cut with an automated sharp blade called a microkeratome, leaving an attachment as a hinge on one side. The hinged flap thus created is 120–150 mm thick, is lifted up with a smooth blunt spatula and the stromal bed ablated with a laser which precisely sculpts the cornea to the desired extent ensuring a minimum residual stromal bed thickness of 250 mm to maintain adequate corneal biomechanical stability and prevent iatrogenic ectasia. Following this, the flap is reposited and remains in place

Advances:

1. laser-assisted epithelial keratomileusis or LASEK :use of alcohol to lift a thin flap of epithelium

2. Epi-LASIK use of a special microkeratome designed to cut and separate a thin flap of epithelium and Bowman’s layer of a 

3. Femtosecond laser to pre-fashion the anterior flap to a desired size and depth without using a surgical blade.