Purpose
Hypodense regions (holes) can be seen in the circumpapillary retinal neural fiber layer (cpRNFL) on scans of glaucoma patients and suspects, obtained with frequency domain optical coherence tomography (fdOCT) [1]. We investigated whether and how the appearance of these holes changes over time.
Methods
Eighteen eyes of 14 glaucoma patients or suspects with RNFL holes seen on prior testing [1] were re-tested on average 31.6 months later (range 10 to 43 mos.). The average mean deviation of the 24-2 visual field (Zeiss Inc.) was -2.88 dB (0.53 to -8.17 dB) and -2.32 dB (1.11 to -7.01 dB) at the first and last test date respectively. Circumpapillary circle (1.7 mm radius) and disc cube scans were obtained (3D-OCT 2000, Topcon Inc., Tokyo). Three individuals experienced at reading OCT scans evaluated the images for change.
Results
Changes in the appearance of the holes were seen in 13 of the 18 eyes. These changes included a) holes enlarge and/or increase in number (Fig. 1A, n=10); b) holes breaking through the internal limiting membrane to form a notch (Fig. 1B, n=3); c) holes which collapsed with thinning of the RNFL (Fig. 1C, n=5). The mean time between tests was 33.1±8.3 and 26.0±15.8 months for the eyes with and without changes, respectively. Of the 13 eyes showing a change in the holes, 11 showed little or no change in MD (<0.5 dB). Two eyes, one like Fig. 1A and one like Fig. 1C, had larger changes (-2.3 and -2.9 dB) in MD.
Conclusions
The hypodense regions (holes) are thought to represent local loss of axons in the RNFL. [1] The size and extent of these holes can change over relatively short (18 months) time periods. These changes can occur without detectable changes in the visual field, but can affect the RNFL thickness as measured with fdOCT. 1. Xin D, Talamini CL, Raza AS et al, IOVS, 2011,7180-6.
Keywords: 610 nerve fiber layer •
550 imaging/image analysis: clinical