Assessment of the Ocular Response Analyzer as an Instrument for Measurement of Intraocular Pressure and Corneal Biomechanics. (2nd November 2015)

• Record Type: Journal Article
• Authors: Elsheikh, Ahmed; Joda, Akram; Abass, Ahmed; Garway-Heath, David
• Is Part Of: Current eye research. Volume 40:Number 11(2015:Nov.)
• Page Start: 1111
• Page End: 1119
• Publication Date: 2015-11-02
• Subjects: Cornea -- intraocular pressure -- ocular biomechanics -- ocular response analyzer -- tonometry; Ophthalmology -- Periodicals; Eye -- Diseases -- Periodicals; Ophthalmology -- Periodicals; 573.88
• DOI: 10.3109/02713683.2014.978479
• Languages: English
• ISSNs: 0271-3683

Abstract

Abstract: Purpose : The purpose of this study is to provide better understanding of the Ocular Response Analyzer (ORA) and how reliable it is to produce intraocular pressure (IOP) measurements that are free of the effects of corneal stiffness parameters, and stiffness estimates that are independent of IOP. Materials and Methods : A numerical parametric study that closely represents the in-vivo conditions of the human eye and the ORA procedure was conducted to determine the correlation coefficient r 2 between ORA output and the values of true IOP and a number of stiffness parameters, namely corneal thickness, curvature and age. For the purpose of this exercise, the ORA output was put in the form k 1 P 1 + k 2 P 2 where k 1 and k 2 were variables and P 1 and P 2 were ORA's measured applanation pressures. Two separate clinical datasets involving Moorfields Eye Hospital, London and the University of New South Wales, Sydney participants, respectively, were used to validate the numerical results. Results : The numerical study results show a strong association between ( k 1 P 1 + k 2 P 2 ) and the true IOP over a wide range of k 1 and k 2 values apart from a narrow region approximately extending from ( k 1 = +2, k 2 = −2) to ( k 1 = −2, k 2 = +2). On the other hand, ( k 1 · P 1 + k 2 · P 2 ) was found to have a strong association with CCT, R and age (the stiffness parameters) over the same narrow region, beyond which the association was weak. Similar trends were found with the two clinical datasets. Conclusions : The results of this study show the potential of the ORA to provide reliable IOP measurements with weak dependence on the cornea's stiffness parameters and the considerably reduced reliability in producing stiffness estimates that are unaffected by IOP values.