Catalina Palomo-Álvarez

Impaired Mesopic Visual Acuity in Eyes with Early Age-Related Macular Degeneration

PURPOSE To determine photopic and mesopic distance high-contrast visual acuity (HC-VA) and low-contrast visual acuity (LC-VA) in eyes with early age-related macular degeneration (AMD). METHODS Measurements were made in 22 subjects with early AMD and 28 healthy control subjects. Inclusion criteria included a photopic HC-VA of 20/25 or better. Distance VA was measured using HC (96%) and LC (10%) Bailey-Lovie logMAR letter charts under photopic (85 cd/m(2)) and mesopic (0.1-0.2 cd/m(2)) luminance conditions. RESULTS Mean mesopic distance HC-VA and LC-VA were significantly worse (0.1 logMAR and 0.28 logMAR, respectively) in the early AMD group than in the control group. Under mesopic conditions, the mean difference between LC-VA and HC-VA was significantly greater in the early AMD (0.45 logMAR) than the control group (0.27 logMAR). Mean differences between mesopic versus photopic HC-VA and mesopic versus photopic LC-VA were significantly greater in the early AMD than the control group (0.13 and 0.32 logMAR of difference between the means, respectively). Sensitivity and specificity were significantly greater for mesopic LC-VA than for mesopic HC-VA (Receiver Operating Characteristics, area under the curve [AUC], 0.94 ± 0.030 and 0.76 ± 0.067, respectively). AUC values for photopic HC-VA and LC-VA were below 0.70. CONCLUSIONS Visual acuity testing under low luminance conditions emerged as an optimal quantitative measure of retinal function in early AMD.

Normal Values for the Size of a Halo Produced by a Glare Source

PURPOSE To determine the size of a halo in the visual field induced by bright light in healthy eyes of all ages using the Vision Monitor (MonCv3; Metrovision, Pérenchies, France) and to assess the repeatability of the method. METHODS Measurements were made in the right eyes of 147 healthy subjects (mean age: 48.2 ± 16.2 years) who were classified into six age groups. Using the Vision Monitor, optotypes of low luminance were presented at a distance of 2.5 m. The visual angle subtended by the radius of the halo was calculated in minutes of arc (arc min). The repeatability of the method was determined in a subset of 37 subjects older than 50 years by calculating the Bland-Altman coefficient of repeatability. RESULTS The mean radius of the halo was 111.6 ± 39.8 arc min. Halo radius started to increase significantly from the age of 50 to 59 years. The relationship between halo radius and age (r = 0.65; P < .0001) was described by fitting a power function to the data. Halo size was independent of gender. The coefficient of repeatability of the method was ±44 arc min. CONCLUSIONS Halo size increases with age following a power model. The normal halo size values provided could help clinicians distinguish between normal or abnormal glare problems. The intersession repeatability observed for halo size measurement indicates this method could be useful for assessing visual impairment caused by glare.

Relationship between macular pigment and visual acuity in eyes with early age-related macular degeneration.

Purpose:  Today the extent to which MP impacts visual function in early AMD remains unclear. This study examines the relationship between macular pigment optical density (MPOD) and high‐contrast visual acuity (HC‐VA) and low‐contrast visual acuity (LC‐VA) in eyes with early age‐related macular degeneration (AMD).

Relationship between halo size and forward light scatter

Purpose To determine the relationship between the size of a halo induced by a glare source and forward scatter or visual acuity (VA) in healthy eyes. Method Measurements were made in the right eyes of 51 healthy individuals of mean age 29.3±7.5 years. Halo radius was measured using the Vision Monitor and low luminance (1 cd/m2) optotypes presented at a distance of 2.5 m. The visual angle subtended by the radius of the halo was calculated in minutes of arc (arc min). Forward scatter or, straylight, was measured using the compensation comparison technique. Best-corrected distance VA was measured using high contrast (HC) (96%) and low contrast (LC) (10%) Bailey-Lovie logMAR letter charts under photopic (85 cd/m2) and mesopic (0.15 cd/m2) luminance conditions. Results Mean halo radius was 202±43 arc min (3.4±0.7°) and mean retinal straylight was 0.95±0.12 log units. Mean photopic distance HC-VA and LC-VA were −0.02±0.06 and 0.12±0.09 logMAR, respectively. Mean mesopic distance HC-VA and LC-VA were 0.35±0.11 and 0.74±0.11 logMAR, respectively. Forward stepwise regression analysis revealed that halo radius was significantly correlated with straylight (r=0.45) and mesopic LC-VA (r=0.48), but not with photopic HC-VA and/or LC-VA and mesopic HC-VA. Conclusions In healthy eyes, the larger the halo size induced by a given glare source, the greater the forward-scatter (straylight) and worse the mesopic LC-VA. Halo size seems to be independent of photopic HC-VA or LC-VA and mesopic HC-VA.

Capacity of straylight and disk halo size to diagnose cataract.

Purpose To examine the capacity of straylight and disk halo size to diagnose cataract. Setting Faculty of Optics and Optometry, Universidad Complutense de Madrid, Spain. Design Prospective study. Methods Straylight, disk halo radius, and high‐contrast corrected distance visual acuity (CDVA) measurements were compared between patients with age‐related cataract and age‐matched normal‐sighted control subjects by calculating the area under the curve (AUC) receiver operating characteristic. Results Measurements were made in 53 eyes of 53 patients with a mean age of 67.94 years ± 7.11 (SD) and 31 eyes of 31 controls with a mean age 66.06 ± 5.43 years. Significantly worse (P < .001) mean straylight (1.38 ± 0.24 log[s]), mean disk halo radius (2.40 ± 0.18 log minutes of arc [arcmin]), and mean CDVA (0.17 ± 0.11 logMAR) were recorded in the cataract group than in the control group (1.17 ± 0.11 log[s], 2.10 ± 0.16 log arcmin, and 0.08 ± 0.08 logMAR). Significant differences in AUCs were observed for disk halo radius (0.89 ± 0.04) versus straylight (0.77 ± 0.05) (P = .03) and disk halo radius versus CDVA (0.72 ± 0.05) (P = .001). The comparison of disk halo radius versus the discriminant function with input from CDVA and straylight (0.80 ± 0.05) was at the limit of significance only (0.091 ± 0.05, P = .051). Conclusion Although all 3 variables discriminated well between normal eyes and eyes with cataract, the disk halo radius showed the best diagnostic capacity. Financial Disclosure Neither author has a financial or proprietary interest in any material or method mentioned.

Effects of Light Scatter and Blur on Low-Contrast Vision and Disk Halo Size

PURPOSE To investigate the individual effects of forward light scatter (FLS) and refractive blur on low-contrast vision and the size of the disk halo produced in response to an external glare source. METHODS Monocular disk halo radius, high- and low-contrast distance visual acuity (HCVA, LCVA), and contrast sensitivity (CS) were determined in 25 eyes of 25 healthy subjects under normal, FLS, and blur conditions. FLS was induced using the filter Black ProMist 2 to simulate an early cataract. Blur was induced using a +1.00 diopter lens to simulate an uncorrected refractive error. RESULTS Similar significant mean increases in halo radius were observed for the FLS (0.32 ± 0.10 log arc min; P < .0001) and refractive blur (0.40 ± 0.18 log arc min; P < .0001). Under induced blur, 3 lines of HCVA (0.32 ± 0.15 logMAR; P < .0001) and 4 lines of LCVA (0.39 ± 0.16 logMAR; P < .0001) were lost. FLS had a minimal (but significant) effect on HCVA, but worsened mean LCVA by more than 1 line (0.13 ± 0.10 logMAR; P < .0001). Similar significant mean CS reductions of 0.17 ± 0.12 (P < .0001) and 0.14 ± 0.12 log units (P < .0001) were produced in response to FLS and refractive blur, respectively (approximately 1 triplet). CONCLUSIONS Forward light scatter and refractive blur contributed to an increased size of the disk halo produced by a glare source in similar proportion. Although defocus blur has a substantial effect on LCVA, a loss of more than 1 line of LCVA after best refractive correction would be indicative of FLS.