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Editors Selection IGR 13-3

Structure Measurement: Frequency-domain OCT and holes in RNFL

Comment by David Huang on:

46382 Hypodense Regions ("Holes") in the Retinal Nerve Fiber Layer in Frequency-Domain OCT Scans of Glaucoma Patients and Suspects, Xin D; Talamini CL; Raza AS et al., Investigative Ophthalmology and Visual Science, 2011; 52: 7180-7186

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Xin et al. (1333) performed a prospective cross-sectional study of 208 eyes of 110 consecutive glaucoma patients and 45 eyes of 45 normal subjects. Using circular and cube scans with a frequency-domain OCT system, holes were found in the retinal nerve fiber layer (RNFL) in 16% of glaucomatous eyes but none of the normal eyes. As a rule, these holes occurred adjacent to blood vessels, with exceptions found in only 3 of 33 eyes. Most of the holes were in the superior and inferior quadrant.

Holes were found in the retinal nerve fiber layer in 16% of glaucomatous eyes but none of the normal eyes

They were seen in all depths within the RNFL. An example showed that the holes near the disc could be traced along the nerve fiber bundle to a track of depression and thinning further from disc. Examples were shown where holes were linked to defects in the corresponding visual field sector, though the statistical significance was not computed. The authors hypothesized that the holes were caused by focal glaucomatous RNFL loss. This was well supported by the results. The authors further explained that the holes might have been formed by nerve fibers pulling away from vessels or vessels contracting. In the opinion of this reviewer, it is more likely that the tenting effect of the vessel on the internal limiting membrane prevented a depression to form at the point of nerve fiber bundle loss and this caused a hole to form instead. This novel observation may have important diagnostic implications; the discovery of internal RNFL defects could aid in the early diagnosis of glaucoma.

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