|
2.4.1.2 Keratotomy
"Slice It"
Keratotomy ("cutting the cornea") follows the idea of changing the biostatics of the eyeball by making a partial thickness incision into the cornea. Most commonly the corneal center is flattened by making incisions in the periphery to correct myopia. Over time many patterns such as radial, trapezoidal or special T-Cuts have been developed. Radial Keratotomy (RK) makes incisions in certain meridians in the periphery to reduce its refractive power in the center of that meridian. RK was made famous by Russia's ophthalmologist Fyodorov in the late 70's [2.5.1]. However, the first long term results have usually shown an unexpected hyperopic shift.
2.4.1.3 Keratectomy
"Wedge It"
The excision of a piece of cornea is called keratectomy1. It is done to change the refraction of the cornea. It involves the removal of a lenticular or a crescentic piece of tissue. Keratectomy takes part in all keratomileusis procedures. The excision of the cornea can either been done mechanically or by light.
The photo refractive keratectomy (PRK) with the excimer laser is the most common keratectomy. Originally scientists tried to replace the manual keratotomy incisions by using the laser. However, the results in using the laser for keratotomy were poor, as the laser always removed tissue. Instead ablating total areas of cornea with laser, doing photo refractive keratectomy has been revolutional in Refractive Corneal Surgery [2.5.3]. Strictly speaking PRK is a superficial keratomileusis procedure.
2.4.1.4 Penetrating Keratoplasty in Aspects of Refraction
"Transplant It"
The major reason for doing a penetrating keratoplasty is to replace the central portion of a scarred or distorted cornea by healthier donor tissue. Until 1980 the major clinical challenge was to produce a clear graft that would last a long time. However, for usual refractive corneal problems, this procedure seems too expensive and risky.
2.4.1.5 Thermokeratoplasty
"Iron It"
Applying heat shrinks the corneal stromal collagen and flattens the cornea in this area. Various sources of power have been tried, such as thermal probe, radio frequency current and even different lengths of laser waves. The holmium YAG laser seemed a promising thermokeratoplasty tool, however its results have been poor due to very unstable refractive results: over time at least 50% of refractive correction has disappeared. | 
> Refractive Surgery > Classification
forward
