Purpose
To determine and characterize the rate of change (µm/year) of peripapillary retinal nerve fiber layer thickness (RNFLT) and ganglion cell complex (GCC) thickness in healthy, ocular hypertensive (OHT) and glaucoma eyes investigated with the RTVue-100 SD-OCT (Optovue, Inc., Fremont, CA).
Methods
In this observational study, 190 eyes of 101 Caucasian patients, consisting of 17 healthy control persons (normal optic nerve head and visual field, IOP≤21 mmHg), 17 OHTpatients (normal optic nerve head and visual field, IOP consistently >21 mmHg), and 67 glaucoma patients (corresponding glaucomatous optic nerve head damage and visual field deterioration) were imaged with the RTVue-100 SD-OCT at 6-month intervals (median follow-up 5.3 years and 11 visits) between 2008 and 2014. The OHT and glaucoma patients received the standard glaucoma treatment. Eyes with disease other than glaucoma or poor OCT image quality, and eyes which underwent cataract surgery at any time during the follow-up period were excluded from the analysis. Both eyes of the participants, if no exclusion criterion was met, were included in the study. The RTVue-100 SD-OCT data were analyzed using the trend analysis function of the Avanti RTVue XR SD-OCT (Optovue, Inc., Fremont, CA , software version 2014.1.0.51).
Results
The age distribution (mean ±SD) was 59.4±11.0 (normal), 53.4±14.8 (OHT), and 60.9±13.9 (glaucoma). The mean ±SD of the rate of change (µm/year) was -0.33±0.51, -0.44±0.62, and -0.69±0.93 for RNFLT, and -0.53±0.36, -0.54±0.52, and -0.80±0.78 for GCC, for the normal, OHT, and glaucoma eyes, respectively. Approximately 15% of the glaucoma eyes had RNFLT and GCC change rate which exceeded the highest rate of thinning of the normal eyes. The rates of change are similar between the normal and the OHT groups.
Conclusions
The RNFLT and GCC rates of change varied considerably among individuals in all 3 groups. In spite of intraocular pressure lowering medication, about 15% of the glaucoma eyes had rates of change (thinning) that exceeded the highest rate of the normal eyes, suggesting that the glaucoma treatment may not have sufficiently slowed down the progressive structural damage in these eyes. The study also suggests that a rate of change exceeding -1.5 µm/year as measured with the Optovue SD-OCT system is unlikely to be fully explained by normal aging.