Optic Disc Parameters by Spectral Domain Optical Coherence Tomography: Normative Values and Associations in Adult Emmetropic, Myopic

Abstract

Abstract
Objectives: To study the optic disc parameters in adult emmetropic, myopic and hypermetropic Pakistani population eyes using Topcon spectral domain optical coherence tomography (SD-OCT) and its variation with refractive error and axial length.
Methods: This cross sectional study was carried out in Ophthalmology Department of Shifa Foundation Falahee Clinic after approval from Ethical Committee and IRB, over a period of one year starting from January 2016. A total of 93 eyes (including 35 myopes 29 emmetropes and 29 hypermetropes) of 93 patients were enrolled, and autorefraction, axial length measurements and optic disc analysis done. Various optic disc parameters were obtained using Topcon SD OCT. A definable optic cup was absent in 9.68% (n=9) of the patients so they were excluded. One-way ANOVA was applied to compare the variables amongst three groups after adjustment for ocular magnification by using Littman's formula. Pearson correlation coefficients (r) were measured to establish the relationship of the optic disc parameters with axial length and disc area.

Results: The study included 51.2% males (n=43) and 48.8% (n=41) females. Mean age was 30.82±8.01years. Mean±SD of cup-disc ratio was 0.33±0.14 and disc area was 2.24±0.44mm2. Statistically significant difference was found among the three groups in disc area (p=0.001). No correlation was observed between disc parameters and axial length except for the linear and vertical CDR. Positive correlation was observed between disc area and various disc parameters.
Conclusions: This study provides normal values for the optic disc parameters in healthy adult Pakistani eyes
as measured by OCT. We also report that optic disc parameters are significantly associated with refractive
error, axial length and disc area.