Abstract
Purpose :
To describe the concordance of keratoconus expression in two pairs of monozygotic twins before and after a combined CXL/PRK procedure.
Methods :
Two pairs of monozygotic twins with keratoconus (KCN) were included in this retrospective study. Improvement of flattest keratometry (k1), steepest keratometry (k2) and Index of Height Decentration (IHD) measured by AS-OCT and Scheimpflug tomography was compared between respective eyes of monozygotic twin siblings 12 and 24 months after the application of combined corneal cross linking (CXL) and partial topography guided photorefractive keratectomy (the Athens protocol).
Results :
Significant improvement was noted in all the keratometric indices of all 8 eyes after the combined CXL/PRK procedure.The difference in k1, k2 and IHD percentage improvement between the right eyes of each pair of twins was statistically significant at 12 and 24 months post op.(p<0.05) Statistically significant disconcordance in k1, k2 and IHD percentage improvement was likewise observed between the left eyes of each pair of twins at 12 and 24 months post op.(p<0.05)
Conclusions :
Monozygotic twin studies like this offer a unique template for better understanding the multifactorial nature of keratoconus. Although genetic predisposition in KCN is well documented, the disconcordance in keratometric indices improvement after a CXL/PRK procedure between respective eyes of monozygotic twins suggests that environmental influences may contribute to the disease expression as well.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.