Comparison Of Changes In Corneal Astigmatism Following Icl Implantation For Refractive Error Correction In Patients With Keratoconus And With Normal Corneas.

To assess the changes in corneal astigmatism after implantation of posterior chamber phakic Implantable Collamer Lenses (PCICL) in patients with Keratoconus (KC) and to compare the results with myopic patients having normal corneas and undergoing the same procedure.

Cornea and Anterior Segment Outpatient Clinics at King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia.

This is a prospective two-armed cohort study including patients with KC (GR1) and those without KC (GR2) undergoing PCICL (Visian ICL, STAAR Surgical) to correct their refractive error. Pre- and post-operative topographic astigmatism of both anterior and posterior corneal surfaces were assessed. The changes in the corneal astigmatism at 3 months to pre-surgery in GR1 and GR2 is the main outcome. 

The study included 25 patients with KC (GR1) and 27 patients without KC (GR2). 

The mean pre-operative Anterior Corneal astigmatism (ACA) was 2.83±0.50 diopters (D) and 1.91±0.87 D in GR1 and GR2, respectively (p = 0.0079). The mean pre-operative posterior corneal astigmatism (PCA) was 0.63 ±0.27 D and 0.44 ±0.19 D in GR1 and GR2, respectively (p=0.0049). Both ACA and PCA were higher in KC group.

At 12 weeks post-operatively, the mean ACA was 2.71±1.4 diopters (D) and 2.0±1.0 D in GR1 and GR2, respectively (p = 0.1460). The mean PCA was 0.65 ±0.27 D and 0.46 ±0.16 D in GR1 and GR2, respectively (p=0.0366). More changes in ACA were noted in KC group while PCA remained almost the same in both groups.

Changes in corneal astigmatism following surgical incisions are more magnified in biomechanically compromised corneas in comparison with normal corneas. This could potentially influence expected surgically induced astigmatism values and may need to be accounted for in calculations.