Spatial contrast sensitivity from star- to sunlight in healthy subjects and patients with glaucoma

Riemannian color difference metric for spatial sinusoidal color variations

Several studies report on the sensitivity of human vision to static spatial sinusoidal achromatic and chromatic contrast variations. However, a Riemannian color difference metric, which includes the spatial and colorimetric properties of sinusoidal gratings, is lacking. Such a metric is important for various applications. Here we report on the development of a new Riemannian metric, for the prediction of detection ellipsoids in color space, for spatial sinusoidal gratings as a function of the grating's size, spatial frequency, luminance and chromaticity. The metric is based on measurements and models of achromatic and isoluminous chromatic contrast sensitivity functions available in literature, and the Riemannian metric for split fields which we reported earlier. We find adequate agreement with various data sets of experimental achromatic and isoluminous chromatic contrast sensitivity functions and with experimentally determined threshold ellipses of isoluminous chromatic Gabor gratings.

MNREAD Reading Vision in Adults With Glaucoma Under Mesopic and Photopic Conditions

Purpose

Despite good photopic visual acuity, glaucoma patients report difficulty performing daily activities under dim light such as reading. Here we investigated the impact of mesopic lighting conditions on reading vision of glaucoma patients.

Methods

The study design included 39 patients with glaucoma and 40 healthy controls. Reading vision was assessed with MNREAD charts under mesopic (2 cd/m2) and photopic (220 cd/m2) conditions. Four reading indexes: maximum reading speed (MRS), critical print size (CPS), reading acuity (RA), and reading accessibility index (ACC) were obtained from the MNREAD test yielding a plot of reading speed versus print size.

Results

Compared to photopic conditions, reading vision of both healthy controls and glaucoma patients significantly decreased under mesopic conditions (P < 0.05). For glaucoma patients (85% with mild or moderate glaucoma), MRS and ACC decreased by six words per minute and 0.1, respectively under mesopic conditions; CPS and RA increased by 0.25 and 0.18 logMAR, respectively. Moreover, under both photopic and mesopic conditions, reading vision of glaucoma patients was significantly worse than that of healthy controls, but the difference was greater under mesopic conditions (P < 0.05) even after controlling for age and visual acuity.

Conclusions

Mesopic conditions make reading more challenging for both healthy controls and glaucoma patients. However, reading in dim light appears to be more burdensome for glaucoma patients. Mesopic reading tests mediated by both cone and rod photoreceptor systems likely provide a more sensitive and comprehensive assessment of a patient's reading impairment than testing under photopic conditions.

Evaluation of the association between macular damage and disability glare in patients with advanced glaucoma

PURPOSE

This study aimed to investigate the factors associated with disability glare in patients with advanced glaucoma and evaluate the impact of disability glare on the vision-related quality of life.

METHODS

We prospectively studied 225 eyes (225 patients) with advanced glaucoma. The visual function was evaluated using the 10-2 and 24-2 Humphrey visual field (VF) (Dublin, California) and contrast sensitivity test. Structural parameters were obtained using RTVue optical coherence tomography and angiography (Fremont, California). Significant loss of macular vessel density (mVD) was defined as VD < 30%. Each participant completed the National Eye Institute Visual Function Questionnaire 25 (NEI-VFQ-25) and questions regarding subjective symptoms of glare.

RESULTS

Fifty-six patients (24.9%) experienced glare and had a lower NEI-VFQ-25 composite score (P = 0.017). The average retinal nerve fiber layer and ganglion cell complex thickness and mean deviation (MD) in the 24-2 VF test were not associated with glare. Significant superior or inferior mVD loss (P < 0.001; odds ratio [OR], 3.45; and 95% confidence interval [CI], 1.83-6.55), lower logarithmic contrast sensitivity at 0.75 cycles/degree (P < 0.001; OR, 0.27; and 95% CI, 0.13-0.56), and worse MD in the 10-2 VF test (P < 0.001; OR, 0.93; and 95% CI, 0.89-0.97) showed an association with glare.

CONCLUSION

In advanced glaucoma, central VF defect and mVD loss are associated with disability glare, which negatively impacts vision-related quality of life.

Binocular Interactions in Glaucoma Patients With Nonoverlapping Visual Field Defects: Contrast Summation, Rivalry, and Phase Combination

Purpose

In glaucoma, visual field defects in the left and right eye may be non-overlapping, resulting in an intact binocular visual field. In clinical management, these patients are often considered to have normal vision. However, visual performance also relies on binocular processing. The aim of this study was to evaluate binocular visual functions in glaucoma patients with intact binocular visual field, normal visual acuity, and stereoscopy.

Methods

We measured in 10 glaucoma patients and 12 age-similar controls: (1) monocular and binocular contrast sensitivity functions (CSF) using a modified quick CSF test to assess binocular contrast summation, (2) dominance during rivalry, and (3) contrast ratio at balance point with a binocular phase combination test. A mirror stereoscope was used to combine the left and right eye image (each 10° horizontally by 12° vertically) on a display.

Results

Area under the monocular and binocular CSF was lower in glaucoma compared to healthy (P < 0.001), but the binocular contrast summation ratio did not differ (P = 0.30). For rivalry, the percentage of time of mixed percept was 9% versus 18% (P = 0.056), the absolute difference of the percentage of time of dominance between the two eyes 19% versus 10% (P = 0.075), and the rivalry rate 8.2 versus 12.1 switches per minute (P = 0.017) for glaucoma and healthy, respectively. Median contrast ratio at balance point was 0.66 in glaucoma and 1.03 in controls (P = 0.011).

Conclusions

Binocular visual information processing deficits can be found in glaucoma patients with intact binocular visual field, normal visual acuity, and stereoscopy.

High-Pass Visual Acuity Loss and Macular Structure-Function Relationship in Patients With Primary Open-Angle Glaucoma

Purpose

The Logarithm of the Minimum Angle of Resolution (logMAR) chart is the most common clinical test for assessing central visual function in glaucoma. However, based on the use of these charts, visual acuity (VA) often remains normal even when severe macular damage exists. Here, we aim to investigate the potential advantages of high-pass VA in detecting glaucoma compared with conventional VA.

Methods

Monocular best-corrected VA measurements were compared for a novel high-pass electronic VA chart (e-chart) and a conventional e-chart in 113 primary open-angle glaucoma (POAG) patients with normal logMAR VA and 65 age-similar healthy controls. One hundred thirty-nine POAG patients underwent spectral-domain optical coherence tomography (SD-OCT) for measurement of macular ganglion cell layer plus inner plexiform layer (GCL+IPL) thickness. Structure-function relationships between OCT measurements and the two VAs were compared. The enrolled eyes were divided into two groups for further analyses according to macular visual field (MVF) defects, specifically two or more adjacent abnormal points within the 12 central sites of 30-2 VF.

Results

The mean deviation (MD) of 30-2 VF test was -12.77 ± 7.47 dB for glaucoma group and -1.70 ± 1.12 dB for control group. The mean difference of the two VAs was slightly larger in glaucoma group (0.29 logMAR) than in control group (0.22 logMAR). The area under the receiver operating characteristic curve of the high-pass e-chart was larger than that of conventional e-chart (0.917 vs. 0.757, P < 0.001). Significant correlations between high-pass VA and GCL+IPL thickness were found only in the MVF-damaged group. Compared with conventional VA, high-pass VA demonstrates stronger correlations with nasal-side macular GCL+IPL thickness (Fisher's Z-test, two-tailed, P2mmin diameter = 0.033 and P3mmin diameter = 0.005).

Conclusions

Compared with conventional VA, high-pass VA displays slightly higher sensitivity to visual loss in glaucoma and has a stronger correlation with the nasal-side macular GCL+IPL thickness.

Translational Relevance

The high-pass acuity test has the potential to be used as an ancillary tool to monitor glaucoma over time.

Glaucoma and Computer Use: Do Contrast and Color Enhancements Improve Visual Comfort in Patients?

PURPOSE

To estimate the impact of glaucoma on computer use and to assess specific adaptations of the graphical interface to this form of visual impairment.

DESIGN

Prospective, experimental cohort study.

PARTICIPANTS

Forty-nine participants were recruited: 16 patients with primary open-angle glaucoma (mean ± SD, 62.7 ± 5.6 years of age), 17 age-matched participants (mean ± SD, 59.1 ± 8.3 years of age), and 16 young control participants (mean ± SD, 23.3 ± 2.1 years of age).

METHODS

An ophthalmologic examination before the study evaluated the level of visual loss (mean deviation), visual acuity (logarithm of the minimum angle of resolution units), and contrast sensitivity (CS) of the primary open-angle glaucoma patients. Each participant underwent the following measurements: an information technology (IT) experience questionnaire, a preference task monitored by eye tracking, and a feedback session. The experimental task was based on ecological computer scenes with 3 enhancement levels (low, medium, and high), determined by gradual modulation of contrast, luminance, and color. Participants were asked to select the most readable and comfortable stimulus among 4 images displayed on the screen: the original computer scene and 3 enhanced versions.

MAIN OUTCOME MEASURES

Clinical, oculomotor, and subjective data were computed together in a multivariate model by using a principal component analysis (PCA).

RESULTS

The PCA revealed 3 principal components accounting for 72% of the total variance of the data and showed a greater need for enhanced computer scenes in glaucoma patients, an equal preference for low and medium enhancement within the 3 groups, and significantly longer oculomotor behavior in the patient groups. Subjective reports of difficulty using IT because of vision were correlated with visual impairment and high enhancement preference. Contrast sensitivity was critical to explaining the main variations of the data. A reduced CS had a significant effect on the preference for enhanced computer scenes (r = -0.43; P < 0.002) and a less effective exploration velocity (r = 0.43; P < 0.002).

CONCLUSIONS

Glaucoma alters the global exploration of computer scenes. High enhancement of the graphical interface could improve visual comfort during computer use. Subjective patients' reports underline the importance of including IT questions in visual-related quality-of-life questionnaires.

Contrast Sensitivity and Glaucoma

Spatial contrast sensitivity decline occurs in different types and stages of glaucoma. In this short review we discuss methods of assessing contrast sensitivity, the role of contrast sensitivity in the pathogenesis of glaucoma and its practical application in clinical practice.

Spatio-chromatic contrast sensitivity under mesopic and photopic light levels

Contrast sensitivity functions (CSFs) characterize the sensitivity of the human visual system at different spatial scales, but little is known as to how contrast sensitivity for achromatic and chromatic stimuli changes from a mesopic to a highly photopic range reflecting outdoor illumination levels. The purpose of our study was to further characterize the CSF by measuring both achromatic and chromatic sensitivities for background luminance levels from 0.02 cd/m² to 7,000 cd/m². Stimuli consisted of Gabor patches of different spatial frequencies and angular sizes, varying from 0.125 to 6 cpd, which were displayed on a custom high dynamic range (HDR) display with luminance levels up to 15,000 cd/m². Contrast sensitivity was measured in three directions in color space, an achromatic direction, an isoluminant “red-green” direction, and an S-cone isolating “yellow-violet” direction, selected to isolate the luminance, L/M-cone opponent, and S-cone opponent pathways, respectively, of the early postreceptoral processing stages. Within each session, observers were fully adapted to the fixed background luminance (0.02, 2, 20, 200, 2,000, or 7,000 cd/m²). Our main finding is that the background luminance has a differential effect on achromatic contrast sensitivity compared to chromatic contrast sensitivity. The achromatic contrast sensitivity increases with higher background luminance up to 200 cd/m² and then shows a sharp decline when background luminance is increased further. In contrast, the chromatic sensitivity curves do not show a significant sensitivity drop at higher luminance levels. We present a computational luminance-dependent model that predicts the CSF for achromatic and chromatic stimuli of arbitrary size.

How do different lighting conditions affect the vision and quality of life of people with glaucoma? A systematic review

This article is a systematic review of evidence regarding the impact of different lighting conditions on the vision and quality of life (QoL) of people with primary open-angle glaucoma (POAG). A systematic literature search was carried out using CINAHL, MEDLINE, PsycARTICLES, PsycINFO, Embase, and Ovid Nursing Database for studies: published up to April 2019; including people diagnosed with POAG; and assessing visual function or QoL in response to changing lighting/luminance levels or glare. Two researchers independently screened studies for eligibility. Data were extracted from eligible studies regarding study design, participant characteristics, outcomes, and results. Quality of included studies was critically appraised. Of 8437 studies, 56 eligible studies were included. Studies investigated the effects of lighting on the following domains among people with POAG: QoL (18/56), psychophysical measures (16/56), functional vision (10/56), activities of daily living (10/56), and qualitative findings (2/56). POAG negatively affects low-luminance contrast sensitivity, glare symptoms, and dark adaptation time and extent. In vision-related QoL questionnaires, people with POAG report problems with lighting, glare, and dark adaptation more frequently than any other domain. These problems worsen with progressing visual field loss. Early-stage POAG patients experience significantly more difficulties in low-luminance or changing lighting conditions than age-matched controls (AMCs), challenging perceptions of early-stage POAG as asymptomatic. However, performance-based studies seldom show significant differences between POAG participants and AMCs on tasks simulating daily activities under non-optimal lighting conditions. Further research with larger samples is required to optimise ambient and task-oriented lighting that can support patients' adaptation to POAG.