A psychophysical technique for measuring cone photopigment bleaching

A new, clinically applicable test has been developed to measure the bleaching of the foveal cone photopigments. This noninvasive test is called steady-state color matching. Steady-state color matching is based on the dependence of a color match on the optical density of the cone photopigments. By measuring the color match as a function of retinal illuminance, it is possible to compute the optical density of the cone photopigments at each illuminance. Thus, abnormalities of photopigment bleaching can be detected. The healthy human visual system can adapt over an 11 log unit range of retinal illuminance. This wide range of adaptation is controlled by both photochemical and neural processes, and to a small extent by pupilary reflexes. In many retinal diseases, adaptational processes are disturbed. 1 ' 2 This research is concerned with abnormalities in photopigment kinetics, ie, the processes of photopigment bleaching and regeneration. These processes are a series of chemical reactions, with bleaching taking place in the photoreceptors, and regeneration requiring both the photoreceptors and the retinal pigment epithelium. At present, the only widely accepted procedure for measuring photopigment kinetics in both normals and patients is retinal densitometry. 1 ' 3 " 9 For instance, in patients with pathology of the photoreceptor-to-pigment epithelium interface, retinal densitometry has been used to demonstrate abnormalities in both the photosensitivity and the regeneration of photopigments. 7 ' 9 However, retinal densitometry is a difficult and costly procedure and requires assumptions concerning stray light that are difficult to test. 8 Thus, a convergent technique for measuring photopigment kinetics is desirable. We have developed a candidate technique, steadystate color matching, that provides rapid, easily-perFrom th

Retinal Vessel Cannulation with an Image-Guided Handheld Robot

Abstract—Cannulation of small retinal vessels is often prohibitively difficult for surgeons, since physiological tremor often exceeds the narrow diameter of the vessel (40-120 μm). Using an active handheld micromanipulator, we introduce an image-guided robotic system that reduces tremor and provides smooth, scaled motion during the procedure. The micromanipulator assists the surgeon during the approach, puncture, and injection stages of the procedure by tracking the pipette and anatomy viewed under the microscope. In experiments performed ex vivo by an experienced retinal surgeon on 40-60 μm vessels in porcine eyes, the success rate was 29 % (2/7) without the aid of the system and 63 % (5/8) with the aid of the system. R I

Subretinal Hyperreflective Material in the Comparison of Age-Related Macular Degeneration Treatments Trials

PurposeTo evaluate the association of subretinal hyperreflective material (SHRM) with visual acuity (VA), geographic atrophy (GA), and scar in the Comparison of Age-Related Macular Degeneration Treatments Trials (CATT).DesignProspective cohort study within a randomized clinical trial.ParticipantsThe 1185 CATT participants.MethodsMasked readers graded scar and GA on fundus photography and fluorescein angiography and graded SHRM on time-domain and spectral-domain (SD) optical coherence tomography (OCT) throughout 104 weeks. Measurements of SHRM height and width in the fovea, within the center 1 mm(2), or outside the center 1mm(2) were obtained on SD OCT images at 56 (n = 76) and 104 (n = 66) weeks.Main outcome measuresPresence of SHRM, as well as location and size, and associations with VA, scar, and GA.ResultsAmong CATT participants, the percentage with SHRM at enrollment was 77%, decreasing to 68% at 4 weeks after treatment and to 54% at 104 weeks. At 104 weeks, scar was present more often in eyes with persistent SHRM than in eyes with SHRM that resolved (64% vs. 31%; P < 0.0001). Among eyes with detailed evaluation of SHRM at weeks 56 (n = 76) and 104 (n = 66), mean VA letter score was 73.5 (standard error [SE], 2.8), 73.1 (SE, 3.4), 65.3 (SE, 3.5), and 63.9 (SE, 3.7) when SHRM was absent, present outside the central 1 mm(2), present within the central 1 mm(2) but not the foveal center, or present at the foveal center (P = 0.02), respectively. When SHRM was present, the median maximum height under the fovea, within the central 1 mm(2) including the fovea and anywhere within the scan, was 86 μm, 120 μm, and 122 μm, respectively. Visual acuity was decreased with greater SHRM height and width (P < 0.05).ConclusionsIn eyes with neovascular age-related macular degeneration (AMD), SHRM is common and often persists after anti-vascular endothelial growth factor treatment. At 2 years, eyes with scar were more likely to have SHRM than other eyes. Greater SHRM dimensions were associated with worse VA. In eyes with neovascular AMD, SHRM is an important morphologic biomarker