Intereye asymmetry in bilateral keratoconus, keratoconus suspect and normal eyes and its relationship with disease severity.

BACKGROUND/AIM: To describe the intereye asymmetry in patients with keratoconus (KC), keratoconus suspect (KCS) and normal participants, and to evaluate the relationship between asymmetry and disease severity.

METHODS: In this prospective observational comparative study, 446 patients with bilateral KC, 68 patients with bilateral KCS and 306 normal participants underwent topographic, keratometric and pachymetric evaluations by Pentacam as well as refractive and visual acuity examinations. The intereye asymmetry in each parameter was calculated and compared between the groups.

RESULTS: All parameters were significantly different between the worse and better eyes in the KC group (p<0.05), but not in the KCS and normal groups. No significant differences were observed in the measurements of the worse and better eyes of the normal group (p>0.05). There was a statistically significant greater intereye asymmetry in all parameters in the KC group compared with the KCS and normal groups (p<0.05). The intraclass correlations were poor in patients with KC, moderate to good in patients suspected with KC and strong in normal participants. There were statistically significant relationships between the intereye asymmetry in all parameters and KC severity in the worse eye in which intereye asymmetry significantly increased with an increase in disease severity, based on Keratoconus Severity Score classification (p<0.05). According to receiver operating characteristic analysis, the intereye asymmetry would effectively discriminate KC and KCS from normal eyes.

CONCLUSION: KC is an asymmetric disease, and the degree of asymmetry is associated with disease severity. The analysis of intereye asymmetry should be performed along with unilateral evaluation in the screening of KC.