Abstract
Abstract: :
Purpose: Minimising the induced astigmatism during penetrating keratoplasty is essential to optimise vision. We investigated the use of the Flieringa or scleral fixation ring with regards to its effect on astigmatism. Methods: 80 patients receiving penetrating keratoplasty were evaluated for their refraction pre and post suture removal, the disease necessitating penetrating keratoplasty, lens status intraoperatively and whether a continuous or interrupted suture was used was noted. Results: The primary reason for surgery in this group was keratoconus (16%), Fuchs corneal dystrophy (19%) pseudo or aphakic bullous keratopathy (8%) and corneal scar (8%). 80% were sutured with a continuous suture, the remaining 20% with interrupted sutures. A Flieringa ring was used in 43% of cases. For all diseases combined there was no difference in the median sphere pre suture removal whether a Flieringa ring was used or not (+1.5 D in both groups). For all diseases there was no significant difference in the median cylinder pre suture removal whether a Flieringa ring was used or not (–4 D in both groups). Post suture removal the astigmatism results were lower in the ring group but not statistically significantly so (with Flieringa ring –0.5 D median sphere vs +1.25 D without [P = 0.174 Wilcoxon rank–sum test], with Flieringa ring –4 D median cyl vs –4.5 D without [P = 0.839] When the keratoconus patients were removed from the study group, to decrease the effect of residual host pathology on astigmatism results, there was no significant difference in the median sphere pre suture removal whether a Flieringa ring was used or not (+1.375 D if used vs +1.25 D if not used) and there was no significant difference in the median cylinder pre suture removal whether a Flieringa ring was used or not ( –3.5 D if used vs –4 if not used) Post suture removal there was some evidence (P = 0.049) that the sphere was lower if the ring was used (with Flieringa ring +0.125 D median sphere vs +2.25 D without). There was slightly less post suture removal cylinder between the groups where a ring was used (–2.5 D) and when it was not (–5.25 D) although this was not significant (P = 0.401) Conclusion: These data provide little evidence that using a Flieringa ring decreases the amount of induced cylinder or sphere pre suture removal. When keratoconus patients were removed from the sample, there is some evidence (P = 0.049) that using a Flieringa ring will result in less sphere post suture removal and there is less cylinder resultant post suture removal but not statistically significantly so with these numbers.
Keywords: astigmatism • transplantation • cornea: clinical science