Corneal Ectasia

Cause
Lasik surgery weakens the corneal stroma, leading to progressive corneal
thinning and protrusion. Subclinical keratoconus and pellucid marginal
degeneration greatly increase the risk of progressive ectasia after lasik
A residual stromal bed thickness less than 250um likely weakens the cornea
excessively and increases the risk of ectasia.
A residual stromal bed thickness of less than 50% of the original corneal
thickness may also excessively weaken the cornea and predispose to ectasia
Prevention.
Review the preoperative corneal topography to exclude mild keratoconus and
pellucid marginal degeneration.
Make sure the expected residual bed thickness for each patient is >250um and
>50% of the original corneal thickness. Consider measuring the flap thickness
intraoperatively to be sure there is adequate residual stromal bed thickness for.
the planned ablation. Consider a surface ablation procedure if the residual
stromal bed thickness is <250um.
Management
A rigid gas-permeable contact lens is often to restore excellent vision of the eyes
with ectasia Intrastromal ring segments. Corneal transplantation maybe required
in contact lens-intolerant cases to improve vision