July 16, 2012 LASER is an acronym for “Light Amplification by Stimulated Emission of Radiation”. Ophthalmologic laser is a source of laser light mounted on a bio-microscope. Directed into the eye, the laser beam causes local photocoagulation. The trace of photocoagulation on the tissue is called a laser seal. The impulse of the laser light which causes photocoagulation has a variable size, intensity and duration.
There are several types of ophthalmologic lasers in use: argon, krypton, Nd-YAG (neodymium-doped yttrium aluminium garnet), carbon-dioxide (CO2), excimer.
Argon laser is mainly used for panretinal photocoagulation in proliferative diabetic retinopathy. Over a thousand laser seals from 0,1 mm to 0,5 mm are discharged all over the retina. Between seals remains network of intact parts of retina. Into the scar of the laser seal grow vessels from the choroid helping to nourish retina from the central retinal artery, which prevents the growth of retinal and vitreous neo-vascularization. Iris neo-vascularization (rubeosis iridis) in diabetic retinopathy sometimes spontaneously subsides after a successful panretinal photocoagulation.
Argon laser also treats subretinal neo-vascularization in macular degeneration. It also performs trabeculoplasty at open angle glaucoma: with the help of gonioskop a laser beam is directed into trabeculum and it photocoagulates a part of the trabeculum perimeter. Initially it causes the decrease of intraocular pressure, but after 6 months on the place of the seal are formed scars which prevent the runoff of aqueous humor at that point and the pressure rises above the initial. This, unfortunately, only delays anti-glaucoma surgery, but it does not replace it.
Krypton laser is used for photocoagulation near fovea because it causes less damage to the optic nerve tissue layer than the argon laser. It is also used when the media are blurred (cataract, vitreous hemorrhage).
Nd-YAG laser emits short pulses of laser light that cause “micro-explosions” of the tissue. It is used for creating openings in the iris (laser iridotomy in closed angle glaucoma), and in the posterior lens capsule, which may become blurred after extra-capsular cataract extraction.
CO2 laser causes evaporation of water from tissues. It is not mounted on a bio-microscope as other ophthalmic lasers, but it is kept in hand by the operator. It is used in ophthalmic plastic.
Excimer laser is used in refractive surgery. It uses argon and fluoride gases as a source of radiation, and it emits ultraviolet light.