The fovea is the retinal location responsible for our most acute vision. There are several methods used to localize the fovea, but the fovea is not always easily identifiable. Landmarks used to determine the foveal location are variable in normal subjects and localization becomes even more difficult in instances of retinal disease. In normal subjects, the photoreceptor axons that make up the Henle fiber layer are cylindrical and the radial orientation of these fibers is centered on the fovea. The Henle fiber layer exhibits form birefringence, which predictably changes polarized light in scanning laser polarimetry imaging. In this study 3 graders were able to repeatably identify the fovea in 35 normal subjects using near infrared image types with differing polarization content. There was little intra-grader, inter-grader, and inter-image variability in the graded foveal position for 5 of the 6 image types examined, with accuracy sufficient for clinical purposes. This study demonstrates that scanning laser polarimetry imaging can localize the fovea by using structural properties inherent in the central macula.

Purpose To determine whether custom scanning laser polarimetry (SLP) images, differing in polarization content, can be used to accurately localize the fovea in the presence of non-exudative age-related macular degeneration (AMD). To determine whether alterations to the foveal structure in non-exudative AMD significantly disrupts the birefringent Henle fiber layer, responsible for the macular cross pattern in some SLP images. To determine whether phase retardation information, specifically color-coded information representing its magnitude and axis, allow better foveal localization than images including retardation amplitude only. Methods SLP images were acquired in 25 AMD subjects and 25 age-matched controls. Raw data were used to generate 5 custom image types differing in polarization content. The foveal location was marked by 3 graders in each image type for each subject. The difference in variability was compared between the AMD subjects and matched controls. We further determined whether the orientation of Henle fiber layer phase retardation improved localization in 10 subjects with the highest variability in images including only phase retardation amplitude. Results Images that differed in polarization content led to strikingly different visualizations of AMD pathology. The Henle fiber layer remained sufficiently intact to assist in fovea localization in all subjects, but with more variability in the AMD group. For both the AMD and matched control group, images containing birefringence amplitude and orientation information reduced the amount of intra-grader, inter-grader, and inter-image variability for estimating foveal location. Conclusions The disruption in Henle fiber birefringence was evident in the eyes with AMD, but nevertheless was sufficient to help in foveal localization despite macular pathology. Phase retardation amplitude and axis of orientation can be a useful tool in foveal localization in patients with AMD.

Significance:The pathological changes in clinically significant diabetic macular edema lead to greater retinal thickening in males than in females. Therefore, male sex should be considered a potential risk factor for identifying individuals with the most severe pathological changes. Understanding this excessive retinal thickening in males may help preserve vision.Purpose: To investigate the sex differences in retinal thickness for diabetic patients. We tested whether males with clinically significant macular edema had even greater central macular thickness than expected from sex differences without significant pathological changes. To determine which retinal layers contribute to abnormal retinal thickness.Methods: From 2047 underserved adult diabetics from Alameda County, CA, 142 patients with clinically significant macular edema were identified by EyePACS certified graders using color fundus images (Canon CR6-45NM). First, central macular thickness from spectral domain optical coherence tomography (iVue, Optovue) was compared for 21 males vs. 21 females without clinically significant macular edema. Then, a planned comparison contrasted the greater values of central macular thickness for males vs. females with clinically significant macular edema, as compared to those without. Mean retinal thickness and variability of central macular layers were compared for males vs. females.Results: Males without clinically significant macular edema had a 12 μm greater central macular thickness than females, 245 ± 21.3 μm and 233 ± 13.4 μm, respectively, t(40) = −2.18, P = .04.Males with clinically significant macular edema had a 67 μm greater central macular thickness than females, 383 ± 48.7 μm and 316 ± 60.4 μm, P < .001, i.e. males had 55 μm or > 5x more, t(20) = 2.35, P = .015. In males, the outer nuclear layer thickness was more variable F 10,10 = 9.34. Conclusions:Underserved diabetic males had thicker retinas than females, exacerbated by clinically significant macular edema.

Phase retardation changes in the central macula indicate loss and/or structural alterations to central cone photoreceptors in nonexudative AMD patients. Scanning laser polarimetry imaging is a noninvasive method for quantifying cone photoreceptor changes associated with central macular disease.

Our results demonstrate changes in inner and outer diabetic retinas not readily detectable by clinical exam. IRL had not thinned at the margins of the large FAZs, indicating neural mass did not yet decrease despite potential ischemia.