Reproducibility of Macular, Retinal Nerve Fiber Layer, and ONH Measurements by OCT in Rhesus Monkeys: The Beijing Intracranial and Intraocular Pressure (iCOP) Study

Abstract

We evaluated repeatability and reproducibility of measurements of the retinal nerve fiber layer thickness (RNFLT), optic nerve head (ONH), and macular inner retinal layer (MIRL) by RTVue spectral-domain optical coherence tomography (OCT) in normal Rhesus monkeys. The experimental study included 15 adult Rhesus macaque monkeys. RNFLT, ONH parameters (area of disc, cup, and rim; volume of cup and rim; and cup-to-disc ratios), and MIRL thickness were imaged at three separate examinations within one month. Each eye was imaged three times at the first examination, and once at each of the two following examinations. We determined the intra-session and inter-session (inter-visit) within-subject SD (Sw), precision (1.96 × Sw), coefficient of variation (CVw, 100 × Sw/overall mean), and intraclass correlation coefficient (ICC). For the intra-session repeatability, ICC values ranged between 0.97 and 1.00 for all ONH parameters, and between 0.80 and 0.98 for all regional RNFLT parameters, with a value of 0.97 for the average RNFLT. For the inter-session (inter-visit) reproducibility, ICC values ranged from 0.93-1.00 for the ONH measurements and from 0.63-0.97 for regional RNFLT parameters, with a value of 0.96 for the average RNFLT. Again, the ICC values were lowest in the temporal inferior and temporal superior regions. The ICC value for the average MIRL thickness was 0.95. Repeatability and reproducibility of spectral-domain OCT measurements of the RNFL, ONH, and MIRL were high in normal monkey eyes. Spectral-domain OCT may be suitable to assess changes in follow-up examinations of monkeys with experimental glaucoma.