Masakazu Hirota

One-Year Outcome of 49-Channel Suprachoroidal–Transretinal Stimulation Prosthesis in Patients With Advanced Retinitis Pigmentosa

Purpose To determine the feasibility of a 49-channel suprachoroidal-transretinal stimulation (STS) retinal prosthesis that was implanted for 1 year. Methods Three patients with advanced retinitis pigmentosa (RP) and with less than or equal to hand motion (HM) vision were studied. A 49-channel STS system was implanted in a scleral pocket, and the stability of the prosthesis, adverse events, and its efficacy were investigated. Results The electrode array was implanted in a scleral pocket located under the parafoveal area through a scleral incision at 14 mm in patient (Pt) 1, 16 mm in Pt 2, and 18 mm in Pt 3 from the sclerocorneal limbus. No complications occurred during surgery in all cases. During the follow-up period, iridocyclitis developed in Pt 2 and Pt 3, which was successfully treated with topical medications. The implanted devices continued functioning and elicited phosphenes in all cases. The results of localization tests (P < 0.05) and table tests (P < 0.05) were significantly better with the prosthesis turned on than turned off in Pt 3. The deviations of the walking tests were smaller with the prosthesis turned on than off in Pt 2 and Pt 3 at multiple times after the implantation. Conclusions The 49-channel STS retinal prosthesis was able to elicit phosphenes in all patients with advanced RP for the entire 1-year experimental period without major complications. Better results on visual tasks were found in the eyes in which the electrode array was implanted closer to the fovea centralis.

False reaching movements in localization test and effect of auditory feedback in simulated ultra-low vision subjects and patients with retinitis pigmentosa.

PurposeTo determine the accuracy of reaching movements with localization tests in subjects with simulated ultra-low vision, and to examine the effectiveness of auditory feedback training in improving the accuracy of the reaching movements.MethodsTwenty-one subjects with simulated ultra-low vision and three patients with advanced retinitis pigmentosa (RP) were studied with the localization tester. The localization tester had white square targets with a visual angle of 10° that were projected randomly on a computer monitor screen. The subjects or RP patients were instructed to touch the center of the target. Each subject was tested 20 trials. The distance from the center of the target to the point where subjects touched, the deviation, was calculated automatically by the computer. We also examined the effect of auditory feedback on improving the accuracy of reaching movements.ResultsThe average angle of deviation in the subjects was not significantly correlated with visual acuity. The points touched by subjects with simulated low vision were located downward and horizontally toward the hand they used. They were condensed around the barycenter of the touched points (paired t tests; *p = 0.037). The touched points of the patients also deviated downward and condensed around the barycenter. The deviations decreased significantly with auditory feedback when trained over 100 trials.ConclusionsThe subjects with simulated ultra-low vision and the advanced RP patients had false orientations against the position of localized target systematically. An auditory feedback system may help to correct the false orientations for reaching movements in patients with very low vision.

Slow Cone Reflectance Changes during Bleaching Determined by Adaptive Optics Scanning Laser Ophthalmoscope in Living Human Eyes

To investigate the changes in the reflectance of human cone photoreceptors by an adaptive optics scanning laser ophthalmoscope (AO-SLO) during photobleaching. A custom-built AO-SLO with an observation light of 840-nm was used to measure the cone densities and the reflectance changes during bleaching by 630 nm red light emitting diodes. Measurements were made at 1° and 3° temporal to the fovea within an area of 1° × 1° in 8 eyes of 8 normal subjects. After dark-adaptation, images of the cone mosaics were recorded continuously for 5-min before, 5-min during, and after 5-min of light stimulation with a sampling rate of 5-Hz. The first positive peak (P1) was observed at 72.2 ± 15.0-s and a second positive peak (P2) at 257.5 ± 34.5-s at 1°. The increase of the reflectance of P1 was significantly larger at 1° (34.4 ± 13.9%) than at 3° (26.0 ± 10.5%; P = 0.03, Wilcoxon’s signed rank test). The average cone density at 1° (51123.13 ± 1401.23 cells/mm2) was significantly larger than that at 3° (30876.13 ± 1459.28 cells/mm2; P <0.001, Wilcoxon’s signed rank test). The changes in the reflectance of the cones during bleaching by red light had two peaks. The two peaks may be caused by regeneration of cone photopigment during bleaching.

Relationships Between Spatial Contrast Sensitivity and Parafoveal Cone Density in Normal Subjects and Patients With Retinal Degeneration

BACKGROUND AND OBJECTIVE To investigate the relationship between spatial contrast sensitivity (CS) and parafoveal cone density (PCD). PATIENTS AND METHODS Fifteen healthy individuals (mean age: 26.1 years ± 4.5 years) and nine patients with hereditary retinal degeneration (mean age: 31.6 years ± 13.4 years) without media opacities were studied. The CS was measured by CSV-1000 (VectorVision, Greenville, OH). The cone mosaic was photographed with an adaptive optics scanning laser ophthalmoscope (AOSLO) with a 1° × 1° field of view centered on the fovea. The PCD was calculated in an annular area with radii of 0.38° and 0.43°. The CS was converted to the logarithm (logCS), and the area under the logCS function (AULCSF) was determined. RESULTS The AULCSF was significantly and positively correlated with the PCD in the control (R2 = 0.522; P = .003) and retinal degeneration (R2 = 0.514; P = .03) groups. CONCLUSION PCD can predict the spatial contrast sensitivity in normal subjects or patients with retinal degeneration without media opacities. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:106-113.].

Automated measurements of human cone photoreceptor density in healthy and degenerative retina by region-based segmentation

Purpose The purpose of this study was to develop an algorithm based on region-based segmentation for automated calculations of human cone photoreceptor density of en face images obtained by an adaptive optics scanning laser ophthalmoscope (AOSLO). Subjects and methods Cone mosaics of 15 eyes of 15 healthy subjects were photographed by a custom-built AOSLO. The cone density was calculated at 0.5, 1.0, and 1.5 mm temporal from the fovea using a region-based segmentation method (RSM) developed in our laboratory. The cone density was also determined by a manual identification method (MIM) and a conventional spatial filtering method (SFM). The cone densities of three eyes of three patients with retinal degeneration were calculated by the three methods and compared to the results from normal eyes. Results The cone densities in healthy retinas determined by the RSM at 0.5, 1.0, and 1.5 mm temporal from the fovea were 28,436, 21,233, and 13,620 cells/mm2, respectively. These densities were in good agreement with a histological study and with in vivo AOSLO studies. The cone densities determined by RSM were different from those determined by MIM with a difference of 5% in healthy eyes. In eyes with retinal degeneration, with the appropriate threshold-level settings or spatial frequency bandwidth, the cone density measured by MIM was significantly closer to that measured by RSM than by SFM. Conclusion These results suggest that our method is more stable than conventional methods in cases of non-periodical photoreceptor structures such as the affected retinal area. Our method can be used in the longitudinal follow-up of retinal degenerative diseases and to determine the effect of therapy.

Objective Evaluation of Visual Fatigue Using Binocular Fusion Maintenance

Purpose In this study, we investigated whether an individuals visual fatigue can be evaluated objectively and quantitatively from their ability to maintain binocular fusion. Methods Binocular fusion maintenance (BFM) was measured using a custom-made binocular open-view Shack–Hartmann wavefront aberrometer equipped with liquid crystal shutters, wherein eye movements and wavefront aberrations were measured simultaneously. Transmittance in the liquid crystal shutter in front of the subjects nondominant eye was reduced linearly, and BFM was determined from the transmittance at the point when binocular fusion was broken and vergence eye movement was induced. In total, 40 healthy subjects underwent the BFM test and completed a questionnaire regarding subjective symptoms before and after a visual task lasting 30 minutes. Results BFM was significantly reduced after the visual task (P < 0.001) and was negatively correlated with the total subjective eye symptom score (adjusted R2 = 0.752, P < 0.001). Furthermore, the diagnostic accuracy for visual fatigue was significantly higher in BFM than in the conventional test results (aggregated fusional vergence range, near point of convergence, and the high-frequency component of accommodative microfluctuations; P = 0.007). Conclusions These results suggest that BFM can be used as an indicator for evaluating visual fatigue. Translational Relevance BFM can be used to evaluate the visual fatigue caused by the new visual devices, such as head-mount display, objectively.

Visual Target Strategies in Infantile Nystagmus Patients With Horizontal Jerk Waveform

The aim of this study was to propose a new pathophysiological hypothesis for involuntary eye oscillation in infantile nystagmus (IN): patients with IN exhibit impaired gaze fixation, horizontal smooth pursuit and optokinetic nystagmus (OKN) and use saccadic eye movements for these underlying impairments. In order to induce saccades, they make enough angle between gaze and target by precedent exponential slow eye movements. IN consists of the alternate appearance of the saccade and the slow eye movements. Unlike most previous theories, IN is therefore considered a necessary strategy allowing for better vision and not an obstacle to clear vision. In five patients with IN, eye movements were analyzed during the smooth pursuit test, saccadic eye movement test, OKN test and vestibulo-ocular reflex (VOR) test. Their gaze fixation, horizontal smooth pursuit, OKN and the last half of the slow phase of VOR were impaired. The lines obtained by connection of the end eye positions of fast phase of nystagmus coincided with the trajectories of targets. The findings indicate that patients followed the target by the fast but not the slow phase of nystagmus, which supports our hypothesis. By setting the direction of slow phase of nystagmus opposite to the direction of the OKN stimulation, enough angle can be effectively made between the gaze and target for the induction of saccade. This is the mechanism of reversed OKN response. In darkness and when eyes are closed, IN weakens because there is no visual target and neither the saccade for catching up the target or slow phase for induction of the saccade is needed.