Tonometry by Ocular Response Analyzer in Keratoconic and Warpage Eyes in Comparison with Normal Eyes

PURPOSE: To compare intraocular pressure (IOP) values measured by ocular response analyzer (ORA) in contact lens-induced corneal warpage, normal, and keratoconic eyes. METHODS: In a prospective, observational case–control study, 94 eyes of 47 warpage-suspected cases and 46 eyes of 23 keratoconic patients were enrolled. Warpage-suspected cases were followed until a definite diagnosis was made (warpage, nonwarpage normal, or keratoconus). ORA tonometry and corneal biomechanics testing were performed for all cases in each visit. We had 2–3 measured corneal-compensated IOP (IOPcc) and Goldmann-correlated IOP (IOPg) for each patient (based on group) with at least 2-week interval. RESULTS: After following up of warpage-suspected patients, finally 44 eyes of 22 patients had confirmed soft contact lens-related corneal warpage. Forty-six eyes of 23 people were finally diagnosed as nonwarpage normal eyes. Forty-six eyes of 23 known keratoconus patients were also included for comparison. The demographic and refractive data were not different between the warpage and nonwarpage normal groups but were different in the keratoconus group. Both IOPcc and IOPg were statistically different with the highest value in the warpage group followed by normal and keratoconus groups; the same trend was observed in central corneal thickness (CCT). The mean of IOPg was 14.94 ± 2.65, 13.7 ± 2.33, and 10.86 ± 3 and IOPcc was 15.73 ± 2.4, 15.28 ± 2.43, and 14.08 ± 2.55 in the warpage, normal, and keratoconus groups, respectively. IOPg and IOPcc in the warpage group (based on baseline diagnosis) did not regress to become closer to IOP of normal eyes after discontinuation of contact lens in their follow-up visits (P value for IOPg and IOPcc trends in the warpage group was 0.07 and 0.09 controlling for CCT, respectively). Both IOPcc and IOPg were significantly lower in keratoconic eyes in comparison with normal eyes. After correction for the confounding effect of CCT, a lower IOPcc in keratoconus versus warpage remained significant (P = 0.02). CONCLUSION: Both IOPcc and IOPg were statistically different with the highest value in the warpage group followed by normal and keratoconus groups, just like their CCT. After correction for the confounding effect of CCT, there was no statistically significant difference between the three groups in their measured IOPcc and IOPg except for IOPcc in keratoconus versus warpage (P = 0.02).