Michael H. Brent

Fixation stability during binocular viewing in patients with age-related macular degeneration.

PURPOSE The authors examined the fixation stability of patients with age-related macular degeneration (AMD) and large interocular acuity differences, testing them in monocular and binocular viewing conditions. The relationship between fixation stability and visual performance during monocular and binocular viewing was also studied. METHODS Twenty patients with AMD participated. Their monocular and binocular distance acuities were measured with the ETDRS charts. Fixation stability of the better and worse eye were recorded monocularly with the MP-1 microperimeter (Nidek Technologies Srl., Vigonza, PD, Italy) and binocularly with an EyeLink eye tracker (SR Research Ltd., Mississauga, Ontario, Canada). Additional recordings of monocular fixations were obtained with the EyeLink in viewing conditions when one eye viewed the target while the fellow eye was covered by an infrared filter so it could not see the target. RESULTS Fixation stability of the better eye did not change across viewing conditions. Fixation stability of the worse eye was 84% to 100% better in the binocular condition than in monocular conditions. Fixation stability of the worse eye was significantly larger (P < 0.05) than that of the better eye when recorded monocularly with the MP-1 microperimeter. This difference was dramatically reduced in the binocular condition but remained marginally significant (95% confidence interval, -0.351 to -0.006). For the better eye, there was a moderate relationship between fixation stability and visual acuity, both monocular and binocular, in all conditions in which this eye viewed the target. CONCLUSIONS Fixational ocular motor control and visual acuity are driven by the better-seeing eye when patients with AMD and large interocular acuity differences perform the tasks binocularly.

Reading training with threshold stimuli in people with central vision loss: a feasibility study.

Purpose To evaluate the effectiveness of a perceptual learning technique for improving reading performance of patients with central vision loss and to explore whether this learning generalizes to other visual functions. Methods Ten patients with central vision loss were trained binocularly, in four consecutive sessions, with serially presented words printed at each patient’s reading acuity limit. Patients read 10 blocks of 100 words in each session. They were encouraged to read the whole word and were discouraged to read letter by letter. Assessment sessions before and after training measured fixation stability, monocular and binocular visual acuity, as well as reading acuity, critical print size, and maximum reading speed with continuous text. Another six patients with central vision loss were included in a test-retest control group and were tested twice, 1 week apart, with no intervention. Results The average time required to read a block of trials decreased significantly with each training session. After training, continuous text reading improved in terms of reading acuity (p = 0.017) and maximum reading speed (p = 0.01), but critical print size did not change. Binocular acuity improved significantly from an average of 0.54 logMAR before training to 0.44 logMAR after training. Binocular ratio (better eye acuity/binocular acuity) increased from an average of 1.0 before training to 1.17 after training. There was a 62% improvement in fixation stability in the better eye and 58% in the worse eye. There were no changes in the outcome measures for the test-retest control group. Conclusions The technique described in this article can be used for vision rehabilitation of patients with central vision loss. When training is done with size threshold stimuli, learning generalizes to visual acuity, continuous text reading, and fixation stability.

Dexamethasone intravitreal implant as adjunct therapy for patients with wet age-related macular degeneration with incomplete response to ranibizumab

Purpose To evaluate the visual and anatomical outcomes of dexamethasone intravitreal implant (DXI; 700 μg, Ozurdex; Allergan, Irvine, California, USA) as adjunctive therapy for patients with refractory wet age-related macular degeneration (AMD). Methods Retrospective review of the medical records of seven patients (seven eyes) who initially responded well to intravitreal ranibizumab but subsequently developed persistent intra/sub-retinal fluid (IRF/SRF) and underwent a single injection of DXI, between May 2012 and May 2013. Two weeks after DXI, the patients continued with their monthly ranibizumab injections. Best corrected visual acuity (BCVA) logarithm of the minimum angle of resolution (logMAR) and central retinal thickness (CRT) were recorded at baseline, 2 weeks, 6 weeks, 3 months and 6 months after DXI injection. Complications were recorded too. Results All patients had at least 24 months of ranibizumab treatment. Mean age was 81.5±5.8 years. At baseline, mean BCVA was 0.53±0.13 logMAR (20/70 Snellen) and mean CRT was 273.14±50.94 μm. BCVA did not change significantly after DXI over the follow-up period. However, all eyes had lost fewer than 0.3 logMAR units. Complete resolution of the persistent IRF/SRF was achieved in five eyes (71.4%) at 6 weeks, and remained stable at 3 months. Two weeks after DXI injection, the mean CRT diminished compared with baseline (248.28±31.8 µm; p=0.03) and the greatest reduction was observed at 3 months after DXI injection (241.5±36.6 µm; p=0.04). Progression of lens opacity was detected in one case (50% of phakic eyes). Retreatment with DXI was performed in two eyes. Conclusions DXI appears to be effective in vision stabilisation, decreasing IRF/SRF and improvement of CRT in eyes with refractory wet AMD.

Retinal Blood Flow and Retinal Blood Oxygen Saturation in Mild to Moderate Diabetic Retinopathy.

PURPOSE The aim of this study was to evaluate the relationship between retinal blood flow (RBF) and retinal blood oxygen saturation (SO2) in mild to moderate nonproliferative diabetic retinopathy (NPDR) and in age-matched controls. METHODS One eye of each of 15 healthy subjects (68 ± 6 years) and 13 subjects with mild to moderate NPDR (67 ± 10 years) was dilated. None of the patients with NPDR had received treatment for their retinopathic changes or had any evidence of sight-threatening characteristics. Doppler Fourier-domain optical coherence tomography blood flow was measured using the prototype RTVue system; six separate measurements each comprising an upper and a lower nasal pupil scan were acquired. Six hyperspectral retinal measurements were acquired using a noninvasive hyperspectral retinal camera (prototype H-8.5 HR Camera). RESULTS Total RBF was significantly lower in NPDR when compared to controls (42.7 ± 7.5 vs. 33.0 ± 9.2 μL/min; P = 0.004). Mean retinal arterial and venular SO2 were higher in NPDR than in controls (94.7 ± 2.4% vs. 92.9 ± 1.6%, P = 0.02; 62.5 ± 5.7% vs. 56.3 ± 4.7%, P = 0.003). This study showed a correlation between RBF and arteriolar SO2 in both controls (r = 0.58, P = 0.02) and NPDR (r = 0.54, P = 0.05), but no correlation between venular RBF and venular SO2 in controls (r = 0.24, P = 0.83) or in NPDR (r = 0.23, P = 0.45). The arteriovenous difference (AV difference) was lower in the NPDR group when compared to controls (30.6 ± 6 vs. 36.7 ± 5.3, P = 0.008). CONCLUSIONS This study found a lower total RBF and a lower AV difference in the NPDR group, suggesting a reduced oxygen uptake from the retina in people with relatively early diabetic retinopathy.

Retinal blood flow in response to an intravitreal injection of ranibizumab for neovascular age-related macular degeneration

Purpose:  To assess the hemodynamic response of retinal arterioles and venules following a single intravitreal injection of ranibizumab in neovascular age‐related macular degeneration (NV‐AMD) patients and to assess the influence of the number of prior injections on this response.

Visual field expansion in patients with retinitis pigmentosa.

BACKGROUND To determine the effectiveness of using spectacle-mounted prisms for field expansion in patients with retinitis pigmentosa (RP). METHODS Vision-related activities of daily living (V-ADL) questionnaire scores and functional visual field score (FFS) measurements were conducted before and after a one-month trial of spectacle-mounted prisms in those patients with RP who had residual central visual fields of less than 10 degrees. RESULTS 16 patients were recruited who met study inclusion criteria. Mean V-ADL and FFS at baseline were 67.6 (73%) and 22.9 (46%), respectively. After a 1-month trial using spectacle-mounted prisms, V-ADL and FFS demonstrated significant improvement to 73.4 (80%, p < 0.05) and 27.0 (54%, p < 0.001), respectively. INTERPRETATION Spectacle-mounted prisms effectively create visual field expansion and noticeable spatial orientation benefits in patients with RP. This may provide an adjunctive tool in low vision rehabilitation and should be considered in all cases with RP with less than 10 degrees of visual field.

Courier: a better font for reading with age-related macular degeneration

OBJECTIVE This study examines the reading performance of patients with age-related macular degeneration (AMD) using 4 readily available fonts. DESIGN Experimental study. PARTICIPANTS Twenty-four patients with bilateral AMD participated. METHODS Reading performance (reading acuity, critical print size, and maximum reading speed) was measured for all patients, using 4 versions of the MNRead charts. These charts were printed in the following fonts: Times New Roman (serif, proportionally spaced), Arial (sans serif, proportionally spaced), Courier (serif, mono spaced), and Andale Mono (sans serif, mono spaced). RESULTS Reading acuity was significantly better on the Courier chart (0.58±0.21 logMAR) and significantly worse on the Arial chart (0.69±0.20 logMAR) than on any of the other charts (P<0.05). A larger proportion of patients were able to read≥1 sentences on the Courier chart than on any of the other charts. Reading speed dropped below the limit for fluent reading first with the Arial chart. There was no difference in maximum reading speed with the 4 fonts, and differences in critical print size failed to reach significance (P = 0.052). CONCLUSIONS Font has an effect on the reading performance of patients with AMD at print sizes close to their reading acuity. Courier was the most advantageous and Arial the worst font for reading smaller print. This is contrary to the advice given by agencies for the blind.

Fixation Patterns in Maculopathy: From Binocular to Monocular Viewing

Purpose. The goal of this study was to explore binocular coordination during fixation in patients with age-related macular degeneration (AMD) and to investigate whether there is a shift in eye position when the viewing condition changes from binocular to monocular. Methods. Sixteen people with normal vision and 12 patients with AMD were asked to look at a 3 deg fixation target with both eyes and with each eye individually while the fellow eye was covered by an infrared filter. Fixational eye movements were recorded for both eyes with an EyeLink eye-tracker in all conditions. The shift in eye position at the end of every fixation period was calculated for each eye. Results. All people with normal vision as well as the majority of patients had good binocular coordination during fixation in the binocular viewing condition. When the viewing condition changed from binocular to monocular, three patients (25%) had atypical shifts in their eye position. The shift was related to (1) loss of fixational control when the better eye was covered and the worse eye viewed the target or (2) a slow drift of the viewing eye that was associated with a large phoria in the covered eye. Conclusions. Patients with AMD have good binocular ocular motor coordination during fixation. A change in viewing condition from binocular to monocular can lead to disturbances in ocular motor control for some patients, especially in the worse eye.

High-Resolution Optical Coherence Tomography Retinal Imaging: A Case Series Illustrating Potential and Limitations

Purpose. To present a series of retinal disease cases that were imaged by spectral domain optical coherence tomography (SD-OCT) in order to illustrate the potential and limitations of this new imaging modality. Methods. The series comprised four selected cases (one case each) of age-related macular degeneration (ARMD), diabetic retinopathy (DR), central retinal artery occlusion (CRAO), and branch retinal vein occlusion (BRVO). Patients were imaged using the Heidelberg Spectralis (Heidelberg Engineering, Germany) in SD-OCT mode. Patients also underwent digital fundus photography and clinical assessment. Results. SD-OCT imaging of a case of age-related macular degeneration revealed a subfoveal choroidal neovascular membrane with detachment of the retinal pigment epithelium (RPE) and neurosensory retina. Using SD-OCT, the cases of DR and BRVO both exhibited macular edema with cystoid spaces visible in the outer retina. Conclusions. The ability of SD-OCT to clearly and objectively elucidate subtle morphological changes within the retinal layers provides information that can be used to formulate diagnoses with greater confidence.

Maximum reading speed and binocular summation in patients with central vision loss

OBJECTIVE Visual acuity is a poor predictor of the maximum reading speed of patients with central vision loss. This study examines the effects of binocular summation of acuity on the maximum reading speed of these patients. DESIGN Prospective, observational case series. PARTICIPANTS Twenty patients with central vision loss participated. METHODS Maximum reading speed was measured binocularly using the MNREAD acuity charts. Monocular and binocular acuities were measured with the Early Treatment Diabetic Retinopathy Study (ETDRS) chart. Binocular summation was evaluated with a binocular ratio (BR) calculated as the ratio between the acuity of the better eye to binocular acuity. Fixation stability and preferred retinal locus (PRL) distance from the former fovea were evaluated with the MP-1 microperimetre. RESULTS Six patients experienced acuity summation (BR > 1.05), 5 experienced acuity inhibition (BR < 0.95), and 9 showed equality (BR = 1 ± 0.05). There were no differences in the mean acuity of the better eye, fixation stability, or PRL distance from the fovea of the 3 groups. Maximum reading speed was significantly slower (p < 0.05) for patients who experienced binocular inhibition (mean 42 ± 27 words/min [wpm], median 40 wpm) than for those who experienced binocular summation (mean 107 ± 39 wpm, median 108 wpm) or equality (mean 111 ± 62 wpm, median 90 wpm). BR correlated with the maximum reading speed for the overall sample (r[18] = 0.49, p = 0.03). BR together with PRL distance from the former fovea in the better eye explained 45% of the variance in maximum reading speed. CONCLUSIONS Binocular summation of acuity rather than visual acuity alone affects maximum reading speed of patients with central vision loss. Patients with binocular inhibition read significantly slower than those with binocular summation or equality. Assessment of binocular summation is important when devising reading rehabilitation techniques.