Abstract
Purpose :
In this retrospective cross-sectional study, we compared the left-right asymmetry in keratoconus (KC) to a healthy control group of candidates for refractive surgery. In addition, these differences were assessed in relation to the KC stage of the more severely affected “worse eye”.
Methods :
We included patients with the diagnosis of KC on at least one eye according to Pentacam’s Topographic Keratoconus Classification (TKC≥0.5) and no history of ocular surgery. The control group comprised patients that had been scheduled for laser refractive surgery after the eyes had been classified as healthy. Main outcome measures include visual acuity (VA), refraction, topographic (Placido disk), tomographic (Pentacam) and biomechanical (Ocular Response Analyzer) parameters from each eye. Results were compared intra-individually and between the KC group and the control group. Eyes were labeled into "worse eye" and "contralateral eye" according to TKC. In case of equal TKC in KC and in the control group, the left eye was defined as “worse”.
Results :
The study included preoperative datasets of 68 healthy refractive patients (35±13 years) and 353 datasets of KC patients (37±11 years). The age distribution was not significantly different (p=0.219). The KC group comprised significantly more male patients than the control group (72% vs. 39.7%, p<0.001). In KC the TKC staging was equal for both eyes in 13.9%, in the remaining eyes the right eye was found to be worse in 56.4%. Inter-lateral TKC differences (0-0.5/0.5-1/1-2/>2) were found in 27.2%/17.6%/12.7%/28.6%, respectively. Mean difference in TKC was 1.2±1.0 stages. The inter-lateral differences of VA, refraction, topographic, tomographic and biomechanical parameters were significantly different from those of the control group (all p<0.023). A comparison between different TKC groups revealed an increase of asymmetry for most parameters with increasing KC severity of the worse eye.
Conclusions :
We found that the left-right asymmetry is a frequent clinical feature in keratoconus which is evident with various diagnostic tools. The asymmetry of KC patients significantly differs from normal patients even in early stages of KC. The asymmetry is increasing with the severity of KC in the worse eye.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.