Clinical characteristics of eyes demonstrating atypical patterns in scanning laser polarimetry

Abstract

Purpose To characterize which clinical features are associated with the occurrence of atypical birefringence patterns (ABP) occasionally seen with scanning laser polarimetry (SLP). Methods Sixty-one subjects, including glaucoma patients, glaucoma suspects, and normal subjects, underwent a full clinical examination, standard visual field (VF) test, and a GDx-VCC SLP examination. One eye was selected from each patient. The magnitude of ABP was determined in two independent ways: using a support vector machine analysis (typical scan score (TSS)) and by a masked experienced observer. We assessed whether the magnitude of ABP was correlated with age, gender, the refractive state of the eye, corneal polarization axis and magnitude, GDx global parameters (TSNIT and NFI), and the VF status, as evident from glaucoma hemifield test (GHT), mean deviation (MD), and the pattern standard deviation (PSD). Results Of the 61 study eyes, 27 (44%) showed an ABP, based on a TSS cutoff (o82.5). A very high correlation was found between the TSS score and the masked experienced observer score (r 2 ¼ 0.80; Po0.001). The following clinical parameters were found, on bivariate analysis, to be significantly correlated with the presence of an ABP: age (r 2 ¼ 0.086; P ¼ 0.02); corneal polarization magnitude (r 2 ¼ 0.069; P ¼ 0.04); TSNIT (r 2 ¼ 0.16; Po0.001). Conclusion The presence and magnitude of ABP did not seem to be closely correlated with most clinical parameters. A low, but statistically significant, correlation was found for age and corneal polarization magnitude (r 2 ¼ 0.086 and 0.069, respectively). A lowmedium correlation was found for TSNIT (r 2 ¼ 0.16); however, we speculate that this might represent a confounding effect, rather than an underlying association. We conclude that none of the clinical parameters investigated in this study appears to be strongly correlated with the presence of an ABP on SLP scans performed using the commercially available GDx-VCC.

Retinal Nerve Fiber Layer Measurements by Scanning Laser Polarimetry With Enhanced Corneal Compensation in Healthy Subjects

“…22 Earlier studies with the VCC protocol also found a significant negative relationship between age and TSS with the number of ABP images being more in older individuals. 3,13,17 We however did not find such associations probably because of a limited range of TSS in our study.…”

Predictors of atypical birefringence pattern in scanning laser polarimetry

“…In the study by Orlev et al ,7 no correlation was found between refractive error and TSS in 61 glaucoma patients, glaucoma suspects and normal subjects. Bagga et al 3 also reported that there was no significant difference in mean refractive error between subjects (20 normal subjects, 45 glaucoma patients) with normal and abnormal birefringence patterns.…”

“…While it is commonly believed that ABP is more common in myopic eyes, a number of studies suggested that myopia may not result in ABP 3 7. Nevertheless, the relatively small number of myopic subjects in these studies may limit their generalizability.…”

New developments in scanning laser polarimetry for glaucoma

“…ARPs may provide spurious measurements of the RNFL [16] and occur in approximately 10-25% of healthy eyes and 15-51% of glaucomatous eyes [13,15,17,18]. In addition, they occur more frequently in eyes of elderly subjects [19] and appear to be more frequently present in eyes with lightly pigmented fundi and in high myopes.…”