Melanopsin-driven pupil response in summer and winter in unipolar seasonal affective disorder.

A retinal subsensitivity to environmental light may trigger Seasonal Affective Disorder (SAD) under low wintertime light conditions. The main aim of this study was to assess the responses of melanopsin-containing retinal ganglion cells in participants (N= 65) diagnosed with unipolar SAD compared to controls with no history of depression. Participants attended a summer visit, a winter visit, or both. Retinal responses to light were measured using the post-illumination pupil response (PIPR) to assess melanopsin-driven responses in the non-visual light input pathway. Linear mixed-effects modeling was used to test a group*season interaction on the Net PIPR (red minus blue light response, percent baseline). We observed a significant group*season interaction such that the PIPR decreased from summer to winter significantly in the SAD group while not in the control group. The SAD group PIPR was significantly lower in winter compared to controls but did not differ between groups in summer. Only 60% of the participants underwent an eye health exam, although all participants reported no history of retinal pathology, and eye exam status was neither associated with outcome nor different between groups. This seasonal variation in melanopsin driven non-visual responses to light may be a risk factor for SAD, and further highlights individual differences in responses to light for direct or indirect effects of light on mood.

Effects of acute peripheral/central visual field loss on standing balance.

Vision impairments such as age-related macular degeneration (AMD) and glaucoma are among the top risk factors for geriatric falls and falls-related injuries. AMD and glaucoma lead to loss of the central and peripheral visual fields, respectively. This study utilized a custom contact lens model to occlude the peripheral or central visual fields in healthy adults, offering a novel within-subject approach to improve our understanding of the etiology of balance impairments that may lead to an increased fall risk in patients with visual field loss. Two dynamic posturography tests, including an adapted version of the Sensory Organization Test and a virtual reality environment with the visual scene moving sinusoidally, were used to evaluate standing balance. Balance stability was quantified by displacement and time-normalized path length of the center of pressure. Nine young and eleven older healthy adults wore visual field occluding contact lenses during posturography assessments to compare the effects of acute central and peripheral visual field occlusion. The results found that visual field occlusion had greater impact on older adults than young adults, specifically when proprioceptive cues are unreliable. Furthermore, the results suggest that both central and peripheral visions are important in postural control; however, peripheral vision may be more sensitive to movement in the environment.

Identifying the Palisades of Vogt in Human Ex Vivo Tissue.

PURPOSE: The Palisades of Vogt (POV) constitute the corneal epithelial stem cell niche, but identification of this region in ex vivo tissue is difficult. Here we introduce a simple, direct method of identifying the POV in unsectioned, ex vivo human tissue. METHODS: Twenty-two eyes were studied, four whole and eighteen rims. Orientation of whole eyes was determined and the eyes were marked to maintain their cardinal orientation prior to dissection. Samples were imaged with brightfield, linearly polarized light and transmitted circularly polarized light (CPL), and optical coherence tomography (OCT) volumes were acquired in all twelve clock hrs around the limbus. Five samples were also fluorescently labeled to identify the epithelial basement membrane, and whole mounts were imaged with laser scanning confocal microscopy. Images were compared to confirm that the structures visible with polarized light were POV. RESULTS: Under CPL the POV presented as amber radial ridges visible in the superior and inferior regions of the tissue. Identification of POV was confirmed by correlating the structures seen under CPL, OCT and laser-scanning confocal microscopy. CONCLUSIONS: CPL can be used to quickly identify POV regions in donor tissue. This technique can assist in targeted harvesting of stem cell regions for research and tissue for limbal transplant.

Contact lens fitting and long-term management for the Boston keratoprosthesis.

OBJECTIVES: To examine the types of contact lenses used as bandage lenses in the postoperative management of patients with Boston type 1 keratoprosthesis (K-Pro). We examined the lens parameters, the number of trial lenses used to achieve successful fit, and lens replacement schedule. The strategies to achieving a successful fit in these complex patients are reviewed. METHODS: This was a single-center, retrospective chart review of patients who had undergone implantation of the Boston keratoprosthesis in 1 or more eyes from January 2006 to December 2011. Patients included male and female subjects aged 18 years or older who had been fit with bandage contact lenses as part of their postoperative management. RESULTS: Twenty-two eyes of 15 patients met the criteria for this review. The age range was 30 to 90 years. There were eight men and seven women. The average number of lenses to achieve a successful fit varied from 1 to 8, with an average of 2.22 trial lenses used per patient. By 6 months after the surgery, 12 K-Pro eyes showed visual acuity of 20/200 or better, with 7 of those eyes attaining better than 20/80 best-corrected Snellen distance acuity. CONCLUSIONS: Our results show that it is often necessary to use custom contact lenses for K-Pro patients. Management of poor tear film quality, protein deposition, inflammation, lens replacement schedule, and antibiotic resistance are related considerations.