Comparison between Corneal Biomechanics in Normal and Keratoconic Corneas Using Ocular Response Analyzer

Background: keratoconus (KC) is an idiopathic degenerative eye disease characterized by localized thinning and conical protrusion of the cornea, which typically develops in the inferior-temporal and central zones. Consequently, visual acuity is reduced due to irregular astigmatism and high myopia resulting from asymmetric topographical changes in the corneal surface. KC is the most prevalent form of corneal ectasia and affects all ethnicities. However, higher incidence has been reported in Asians when compared to caucasians. Aim of the work: this study aimed to compare the biomechanical properties of the cornea between topographically normal individuals with topographically keratoconic patients.
Patients and methods: this prospective study was carried out from January 2017 to July 2017 on 40 eyes of patients attending outpatient clinic of Ain Shams University Hospitals and Ophthalmology Department of Research Institute of Ophthalmology in Giza.
All participant names were hidden and were replaced by code numbers to maintain privacy of the patients. Ocular response analyzer (ORA) values were obtained from 20 eyes of keratoconus patients and 20 eyes of non keratoconus subjects both topographically tested.
Results: corneal hysteresis (CH) was found to be higher in normal group than keratoconus group; the values were found to be 10.9 ± 1.5 in normal group and 7.88 ± 1.23 in keratoconus group. Corneal resistance factor (CRF) was found to be higher in normal group than keratoconus group, the values were found to be 12.7 ± 1.05 in normal group and 6.7 ± 1.7 in keratoconus group. Goldmann correlated intraocular pressure (ORA_IOPg) was found to be higher in normal group than keratoconus group, the values were found to be 13.13 ± 2.91 in normal group and 10.31 ± 2.99 in keratoconus group. Corneal compensated intraocular pressure (ORA_IOPcc) was found to be 14.17 ± 3.44 in normal group and 14.23 ± 2.01 in keratoconus group, there was no difference between normal group and keratoconus group.
Conclusion: corneal biomechanical properties, characterized by corneal hysteresis and the corneal resistance factor, provide new indicators for the diagnosis of keratoconus.
Recommendations: this study recommended to follow up IOP in keratoconus patients by ORA due to false low results which may be taken by using the Goldman applanation intraocular pressure. Large studies should be done to detect the prevelance of keratoconus in Egypt as this information was missing from peerviewed studies we researched.