Hypodense Regions ("Holes") Are Seen in the Retinal Nerve Fiber Layer of the Frequency-Domain OCT Scans of Glaucoma Patients and Glaucoma Suspects

Abstract

 

Purpose:

 

To better understand hypodense regions ("holes") that appear in the retinal nerve fiber layer (RNFL) of frequency-domain optic coherence tomography (fdOCT) scans of glaucoma patients and glaucoma suspects.

 

Methods:

 

Peripapillary circle (1.7 mm radius) and 3D optic disc fdOCT scans (Topcon 3D OCT 2000) were obtained on 205 eyes from 108 patients (57.7±12.8 yrs) with glaucomatous optic neuropathy (GON) and 45 eyes of 45 controls (48.0±12.6 yrs) with normal fundus exams. Consecutive patients with GON referred for multifocal VEP testing were included if they were over 25 yrs, and had good quality scans and reliable 24-2 visual fields (VF) (Zeiss Meditec). The 205 eyes were divided into those with normal and abnormal VFs, where a VF was considered abnormal if the PSD and/or GHT was abnormal. Holes in the RNFL were identified independently by 2 observers on the circle scans; presence of holes was verified on successive slices of 3D disc scans.

 

Results:

 

A total of 90 holes were found in 32 (16%) eyes of 27 (25%) patients. While some holes were relatively large (fig. left), some were small (fig. right). 72 (80%) of the holes were located adjacent to blood vessels. Holes were not found in any of the healthy control eyes. Of the 32 eyes with holes, 9 were glaucoma suspect eyes with normal VFs (e.g. fig. right). Five of the remaining 23 eyes had abnormal VFs with holes that were associated with a hemifield without a VF defect, as defined as a cluster of 3 abnormal points.

 

Conclusions:

 

The RNFL holes seen in patients with GON are probably due to local loss of RNFL fibers and can occur in eyes of glaucoma suspects with normal VFs.  

 

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • nerve fiber layer • visual fields