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For most eyes with high myopia, optical coherence tomography (OCT) imaging can offer sufficient information to allow for accurate diagnosis of glaucomatous optic neuropathy (GON), despite some previous concerns, investigators say in a newly published report. However, any clinicians who read OCT scans from this class of patients must consider the potential for myopia-related OCT artifacts and segmentation errors, the study authors explain.
To establish this, researchers asked whether or not it was possible to diagnose GON in high myopes via an assessment of OCT imaging alone.
The researchers looked at the OCT scans of 100 eyes from 60 glaucoma patients or suspects. All subjects had corrected spherical refractive errors greater than −6.00 D and axial lengths greater than or equal to 26.5 mm, or both. The study appealed to both a glaucoma specialist and an OCT specialist to identify whether each eye showed GON. The glaucoma specialist used the subjects’ family history, repeat visits, intraocular pressure, 10-2 and 24-2 visual fields, and OCT data. The OCT specialist had only the components of the Heidelberg 3.5 mm inner circle scan, and the option of asking for additional information — which he requested in 37 of the 100 cases. This additional information could only include 3items: (1) the outer circle scans — the Heidelberg 4.1 mm circle scan and 4.7 mm circle scan, (2) a retinal nerve fiber layer (RNFL) thickness map and ganglion cell layer (GCL) thickness map, and (3) B-scans through the horizontal cube scan and vertical cube scan.
The glaucoma specialist, with comprehensive information at her disposal, classified 36 of the 100 eyes as nonglaucomatous (NG) and 64 as glaucomatous (G). The OCT specialist’s diagnosis matched in 97 of these 100 eyes. In the 37 where more information was sought before a diagnosis was reached, 11 had 1 or more disruptive coexisting pathologies — including high myopia. Of these eyes, the OCT specialist looked at the 2 outer circle scans, as well as the inner circle scan. The glaucoma specialist identified GON in 9 of these 11 eyes.
The subjects with high myopia who ended up in the G group typically showed deep circumpapillary RNFL (cpRNFL) defects, widespread cpRNFL damage, or local defects.
The researchers say that this test demonstrates that OCT scans have sufficient information to diagnose glaucoma in most eyes with high myopia. A percentage of scans — 36% of the NG eyes and 11% of the G eyes, in this study — may require additional imaging. The study’s authors added that in principle, this research shows artificial intelligence could be trained to recognize the particulars of diagnosing GON despite artifacts on OCT due to high myopia. In the meantime, human clinicians can be trained “to better use OCT scans for diagnosing glaucoma in eyes with high myopia.” B-scan imaging can also provide necessary information.
Prior to this research, the academic literature showed that the RNFL thickness maps of patients with high myopia may appear abnormally thin due to large axial length and retinal abnormalities. In addition, the tendency of the inferotemporal and superotemporal nerve fiber bundles to be more temporally oriented often resulted in an apparent lack of RNFL thickness in the inferior and superior retina. These anatomic differences can yield arcuate-like artifacts in the RNFL probability maps that mirror the arcuate defects found in glaucomatous eyes.
Some of the authors of this study disclosed financial relationships with relevant device manufacturers. Please see the original reference for a full list of authors’ disclosures.
Reference
Zemborain Z, Jarukasetphon R, Tsamis E, De Moraes C, Ritch R, Hood D. Optical coherence tomography can be used to assess glaucomatous optic nerve damage in most eyes with high myopia. J Glaucoma. 2020;29(10):833-845. doi: 10.1097/IJG.0000000000001631.
