Overlap of conditions with neuro involvement can make things complicated. While glaucoma and multiple sclerosis (MS) may both cause optic neuropathy, presenting clinical signs and symptoms are typically distinct. However, classic findings can sometimes be absent. When OCT is used in attempt to differentiate the two, both can present with nerve fiber layer (NFL) thinning, making it challenging to parse the two from these scans alone.

New research published in Translational Vision Science & Technology addresses this issue, with researchers looking to distinguish between MS and glaucoma by identifying NFL thinning patterns. To achieve this, researchers first divided peripapillary NFL thickness into eight sectors. Then, percentage reduction was calculated relative to normative reference values. MS and glaucomatous eyes were grouped by severity of NFL thinning in the worst sector, including significant reduction (<1 percentile of normal reference), borderline reduction (1% to 5%) and no reduction (>5%).

One MS patient in this study had a superotemporal NFL defect associated with a cotton wool spot, which could be an atypical MS manifestation or relate to other disease, like hypertensive retinopathy. As such, presence of atypical patterns implies that the NFL pattern alone cannot be used for reliable diagnosis but must be interpreted in the context of other diagnostic information. These images from the study show typical NFL percentage reductions in multiple sclerosis and glaucoma. (NU: nasal upper; SN: superior nasal; NL: nasal lower; PI: pattern index; tPI: temporal pattern index; WSI: worst sector index; tWSI: temporal worst sector index.) Photo: Yeh PH, et al. Transl Vis Sci Technol. 2024;13(11):11. Click image to enlarge.

Included in the investigation were 58 control eyes of 58 subjects, 112 eyes of 56 MS patients and 92 eyes of 92 glaucoma patients. What the researchers were able to distinguish was a most pronounced reduction in MS eyes occurring in the temporal-upper and temporal-lower sectors, while in glaucomatous eyes, this was true of the inferior-temporal, inferior-nasal and superior-temporal sectors. The temporal pattern index had the best area under the curve of 0.96 with an accuracy of 92.6% in the significant reduction group, while also having a good area under the curve (0.88) and accuracy (76.7%) in the borderline reduction group.

The study authors write how, when looking for the sector with the worst percent reduction on OCT peripapillary scan, it is already possible to distinguish glaucoma and MS with high accuracy. There was 87.7% accuracy for eyes with significant NFL sector thinning and 72% accuracy for eyes with borderline sector thinning for the temporal worst-sector index. However, beyond identification of the worst sectors, combining information from multiple sectors further aided in diagnostic power, seen with the temporal pattern index which achieved the 0.96 area under the curve and 92.6% accuracy in the significant reduction group.

They also report that the nasal sector in the diagnostic indexes did not improve diagnostic power, and this was likely because the NFL in the nasal hemisphere is relatively spared in glaucoma and MS. The nasal sector would become important, though, if generalizing this approach to include other optic neuropathies like compressive optic neuropathy.

The authors are hopeful that “an important potential clinical use of our approach is the detection of optic nerve damage in MS patients, many of whom can develop NFL reduction without presenting with optic neuritis symptoms and findings.”