An enhancement module to improve the atypical birefringence pattern using scanning laser polarimetry with variable corneal compensation

Abstract

Aim: To examine the repeatability and effect of an enhancement module on the severity of atypical birefringence patterns (ABP) using scanning laser polarimetery (SLP) with variable corneal compensation (VCC).

Methods: 16 patients with perimetric glaucoma (PG), 24 glaucoma suspect and pre-perimetric glaucoma (GSPPG), and 12 normal volunteers (N) were included. One randomly selected eye of each volunteer was scanned three times using VCC and enhanced corneal compensation (ECC) at the same session by the same examiner. Typical scan scores (TSS) were calculated to evaluate the ABP. Coefficients of variability (CoV), coefficients of repeatability (CoR), and intraclass correlation coefficients (ICC) were calculated.

Results: The mean TSS using ECC (n = 97.3 (5.5), GSPPG = 98.3 (3.5), PG = 99.2 (2.3)) was significantly higher (p = 0.02, 0.01, and 0.006, respectively) compared with VCC (86.5 (14.4), 88.2 (18.2), and 83.4 (2.2), respectively). VCC parameters had a CoR of 1.2–6.5, CoV of 1.9%–8.6%, and ICC of 0.8–0.9. ECC parameters had a CoR of 0.5–4.0, CoV of 0.3%–5.1%, and ICC of 0.2–0.9. TSNIT average was the overall best performing parameter with the highest repeatability and least variability using both techniques (CoR<2.1, CoV<2%).

Conclusion: The enhancement module significantly reduced the severity of ABP and maintained a high level of repeatability of retardation measurements.