A typical peripapillary scan is shown in
Figure 1B for a right eye. A magnified view of the region within the white box is presented in
Figure 2A, where blood vessels can be identified by the shadows they cast. The red ellipses show a cluster of three small holes to the left of a large blood vessel, with a larger hole falling to the right of the same vessel. Twenty-eight (25%) of the 110 patients had holes in at least one eye. Of the 208 eyes with GON, 33 (16%) had at least one hole. Holes were not found in any of the healthy control eyes.
Figure 2 shows examples of the pattern of holes seen in the RNFL. Some holes were small (
Figs. 2A,
2D,
2G), and some were relatively large (
Figs. 2E,
2F). In some eyes only a single hole was present in a region (
Figs. 2C,
2D,
2F,
2H), whereas in others they appeared near other holes (
Figs. 2A,
2B,
2E) and sometimes in clusters (
Fig. 2A). Of the 33 eyes with holes, 24 had more than one hole. These holes could be near each other (
Figs. 2A,
2B,
2E) or they could be in another area of the RNFL, often the other half of the RNFL.
The holes tended to occur immediately adjacent to a vessel, as shown in
Figures 2A to
2F. In fact, 31 of the 33 eyes had at least one hole near a vessel. Further, only three eyes had a hole that was not immediately adjacent to a vessel; two of these are shown in
Figures 2G and
2H.
Using the cube scans, it was often possible to follow the course of a hole across scan lines, confirming that the holes were not local artifacts.
Figure 3 provides an example.
Figure 3A (the same image as
Figure 2G) is from the standard circle scan with a radius of 1.7 mm. The holes are present, although more difficult to see in the equivalent circle scan (
Fig. 3B, green border) derived from the cube scan. The colored circles on the fdOCT image in
Figure 3C show the locations of derived circle scans closer to (blue) and further from (red) the optic disc than the 1.7 mm scan. The equivalent portions of these derived scans are shown in
Figure 3B, where a hole is present at radii of 1.2 and 1.7 mm but a depression is present at a radius of 2.4 mm. The symbols in
Figure 3C mark the centers of the holes (magenta circles) and depressions (orange triangles). Note in
Figure 3C that there are holes closer to the disc and a depression/thinning of the RNFL further from the disc and that together they trace a path consistent with that of an RNFL bundle.
The locations of the holes in all 33 eyes are shown in
Figure 4. The location, in degrees, is referenced to a 360° scale, where 0° is the most temporal point of the disc (9 o'clock for the right eye and 3 o'clock for the left). For reference, the Garway-Health et al.
7 disc sectors are indicated by the color bars on the 360° scale and on the fundus picture in
Figure 4A. To understand how to interpret this figure, consider the scan in
Figure 4B. This is the scan from eye 33 shown in
Figures 1B and
2A. As in
Figure 2A, one red ellipse encloses a cluster of three holes, and the other encloses an elongated hole. The locations of these holes for eye 33 are represented in
Figure 4C, by the same two red ellipses. The smaller circle has a red dot in the center, indicating that more than one hole could be discerned. A similar analysis was performed for the other 32 eyes, and the results were presented in the same fashion. This figure allows one to see at a glance where the holes tended to fall.
The holes tended to occur in the regions typically associated with arcuate defects in patients. Holes were not seen in the center of the temporal sector or in the inferior nasal sector of the disc. Interestingly, holes were more common in the superior (25 eyes) than the inferior (16 eyes) portions of the disc.
The holes were fairly evenly distributed across the RNFL. Twenty-two holes appeared near the vitreal border (e.g.,
Figs. 2A,
2E,
2H); 20 appeared deeper in the retina and close to the RNFL/RGC border (
Figs. 2B,
2F); 15 were in the middle of the RNFL (
Fig. 2B); and 13 extended more or less through the RNFL thickness.
Although a comparison of OCT results with visual fields was not a primary purpose here, 30 of the 33 eyes had reliable 24–2 visual fields (Zeiss Meditec, Jena, Germany), as defined by fewer than 15% false-positive or false-negative scores, obtained within 7 months of the OCT scan.
Figure 5 shows the visual fields associated with the eyes with the holes in
Figure 2. The tinted portions are the visual field regions associated with the disc sectors where the holes appeared according to the Garway-Health et al.
7 map. The regions bordered in black and red differentiate those regions (black) associated with the holes seen in
Figure 2 from those (red) associated with holes in another part of the scan. In general, holes were associated with regions of the visual field showing abnormal points (e.g.,
Figs. 5A–D [upper field],
5E,
5H). On the other hand, holes also were seen in eyes (
Fig. 5G) and hemifields (
Fig. 5D, lower field) within normal limits. For example, the eye associated with
Figure 5G had small holes (
Fig. 2G) in both the superior and the inferior disc. The visual field for the eye had a mean deviation (MD) of −0.25 dB and glaucoma hemifield test (GHT) results within normal limits; there was only one abnormal (5%) point. Seven eyes had MD and GHT scores within normal limits, and another two eyes had borderline GHT and normal MD values.
In general, the eyes with holes had mild to moderate field defects. The 30 eyes with holes and visual fields within 7 months of the fdOCT scan had a median MD of −3.78 dB. Twenty-six of these eyes had MD values better than −5 dB and only one had an MD worse than −8.04 dB. More holes were seen in nine eyes with MD values within normal limits.