Influence of Macular Pathology Associated With Age–Related Macular Degeneration in Scanning Laser Polarimetry

Abstract

Abstract: : Purpose: To investigate whether pathology associated with early and late stage of age–related macular degeneration affect the characteristic retardation pattern in macular imaging using scanning laser polarimetry (SLP). Methods: SLP was performed with a GDx (LDT) in 76 eyes, 43 with choroidal neovascularization (CNV) and in 33 with drusen only. Patients were grouped in three categories according to the regularity of the macular bowtie: regular, disrupted, or no bowtie. Statistical comparison among the groups was performed using Chi–squares, with groups matched for age and only one eye per patient. The age of patients in the three categories was compared by ANOVA. Results: In the CNV group 17 patients presented with regular, 7 with disrupted, and 19 with no bowtie pattern, but bowties distributed as 24, 6, and 3, respectively in the drusen group (Chi–square = 8.38, p < .025). The distributions were significantly different (Chi–square = 9.42, p < .01), for the age–matched comparison. Age did not differ across the three categories of bowtie (F = .759, p = .47). Of the total 36 eyes which lacked a regular bowtie, 33 did not have a uniform birefringence image, i.e. had features related to the retinal pathology. Conclusions: According to the current theory, presence of a macular bowtie implies that the Henle fiber layer is sufficiently intact to allow the birefringence to be measured. This is remarkable in several cases with severe subfoveal pathology. More patients with CNV than with only drusen had disrupted or missing bowties, and pathological retinal changes rather than random variations in corneal polarization properties are likely to account for this difference.

Keywords: imaging/image analysis: clinical • age-related macular degeneration