The second cardinal suture is the most important in keratoplasty. SUTURE PLACEMENT is crucial to obtain a good refractive outcome following corneal transplantation. (18) Femtosecond laser corneal surgery has been increasing in popularity and has the potential to overcome many of the problems of manual or automated trephines or microkeratomes. (17) Although penetrating keratoplasty (PKP) generally results in clear corneal grafts, the procedure is frequently complicated by refractive imperfections and wound-healing problems. Tilt, eccentric trephination, poor quality blades, damaged corneal blocks, asymmetric pressure from lid speculums and scleral rings can all cause irregular astigmatism. Regional thinning, vascularisation, keratoconus and aphakic patients tend to have more irregular astigmatism. (13) mechanical epithelial removal, corneal haze and scarring and irregular surface healing can lead to irregular astigmatism. (13) (Figure 3) There is sometimes continuous hyperopic shift that also reduces visual acuity. Visual distortion and glare are more marked in patients having more than 8 incisions, incisions located inside the 3 mm central zone and hypertrophic scarring. (13) Healing of these incisions involves irregular fibrous tissue and epithelial plugs, leading to an asymmetric central flattening. Healing of the RK incisions is very slow and unpredictable, often incomplete even years after surgery. (12) It is important, once again, to evaluate the relative contribution of the opacity versus the optical effect of the scar tissue, before attempting laser correction of the irregular astigmatism. Irregular astigmatism occurs relative to the type of trauma as well as with the surgical technique used in the primary repair. (11) CORNEAL TRAUMA is an important cause of irregular astigmatism due to scar formation and consequent local variation of the refractive properties of the cornea. hereditary endothelial dystrophy 1 and 2 and X-linked endothelial corneal dystrophy).
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