Semi-automated quantitative analysis of the middle limiting membrane in tubercular serpiginous-like choroiditis using swept-source optical coherence tomography

To analyze the longitudinal changes in the outer plexiform layer (OPL) in patients with tubercular serpiginous-like choroiditis (TB SLC) and compare it to the healthy control population. Clinical and imaging data of subjects with TB SLC (minimum 6-month follow-up) and healthy control subjects were reviewed. Optical coherence tomography (OCT) imaging obtained using swept-source device (DRI Triton, Topcon, Japan) from three visits (baseline, 3 months, and 6 months) were analyzed. Three OCT scans were chosen-one passing through the center of the fovea, one line above, and one line below. After random indexing to anonymize the images, they were pre-processed and fed into an automated pipeline to identify, crop, and measure the area of the OPL in the line scan. Longitudinal comparisons of OPL within the patient group were performed. The study included 32 eyes (16 patients; 11 males; mean age: 32.9 +/- 7.8 years) with TB SLC. Twenty-eight eyes (14 subjects; 10 males: mean age: 31.1 +/- 6.2 years) of healthy control subjects (age- and gender-matched) were also selected. The area of OPL was significantly different between the baseline and month 6 visit (6288 +/- 1803 versus 5487 +/- 1461; p = 0.0002) at the central scan passing through the fovea. For the scans above and below the fovea, the reduction in OPL area was significant at each visit (p < 0.0001). In comparison with healthy control subjects, OPL area values in patients with TB SLC were significantly lower at the month-3 (6116 +/- 1441 versus 7136 +/- 2539; p = 0.04) and the 6-month visit (5487 +/- 1461 versus 7136 +/- 2539; p < 0.001). The atrophied OPL at month 6 has been referred to as the "middle limiting membrane" (MLM). Subjects with TB SLC may develop progressive atrophy of the OPL resulting in formation of MLM, which is seen as a hyper-reflective line replacing the OPL. The analysis of longitudinal changes in the OPL may be useful in predicting anatomical and functional outcomes in these patients.