Resolution acuity across the visual field for mesopic and scotopic illumination

Effect of low luminance on face recognition in adults with central and peripheral vision loss

PURPOSE

To investigate the effect of low luminance on face recognition, specifically facial identity discrimination (FID) and facial expression recognition (FER), in adults with central vision loss (CVL) and peripheral vision loss (PVL) and to explore the association between clinical vision measures and low luminance FID and FER.

METHODS

Participants included 33 adults with CVL, 17 with PVL and 20 controls. FID and FER were assessed under photopic and low luminance conditions. For the FID task, 12 sets of three faces with neutral expressions were presented and participants asked to indicate the odd-face-out. For FER, 12 single faces were presented and participants asked to name the expression (neutral, happy or angry). Photopic and low luminance visual acuity (VA) and contrast sensitivity (CS) were recorded for all participants and for the PVL group, Humphrey Field Analyzer (HFA) 24-2 mean deviation (MD).

RESULTS

FID accuracy in CVL, and to a lesser extent PVL, was reduced under low compared with photopic luminance (mean reduction 20% and 8% respectively; p < 0.001). FER accuracy was reduced only in CVL (mean reduction 25%; p < 0.001). For both CVL and PVL, low luminance and photopic VA and CS were moderately to strongly correlated with low luminance FID (ρ = 0.61-0.77, p < 0.05). For PVL, better eye HFA 24-2 MD was moderately correlated with low luminance FID (ρ = 0.54, p = 0.02). Results were similar for low luminance FER. Together, photopic VA and CS explained 75% of the variance in low luminance FID, and photopic VA explained 61% of the variance in low luminance FER. Low luminance vision measures explained little additional variance.

CONCLUSION

Low luminance significantly reduced face recognition, particularly for adults with CVL. Worse VA and CS were associated with reduced face recognition. Clinically, photopic VA is a good predictor of face recognition under low luminance conditions.

The role of peripheral vision during decision-making in dynamic viewing sequences

Decision-making in team sports necessitates monitoring multiple performers located at different distances (i.e., viewing eccentricities) from a critical information source. The processing of peripheral information is generally impaired under anxiety and when responding to stimuli located at larger eccentricities. These hypotheses have not been sufficiently tested in dynamic performance environments. We examined how pressure and eccentricities affect decision-making and visual behaviour in 4v4 basketball defensive scenarios using a head mounted display. Experienced players monitored plays from the first-person perspective (centre position) and made defensive steps towards opponents threatening the basket from different eccentricities under low- and high-pressure. To tax working memory, participants simultaneously performed a backward counting task. Players responded slower and with lower accuracy to opponents at larger eccentricities. Players mostly fixated on the ball-carrier, but over 50% of fixations were located on peripheral players, indicating that information in the periphery must be frequently updated with foveal vision (i.e., pivot strategy). When pressured, participants increased mental effort and improved counting performance; however, gaze behaviour and decision-making were relatively unaffected. Findings suggest that basketball players respond more quickly to opponents positioned at lower compared to higher eccentricities at the cost of impaired responses to opponents in the periphery.

Enhanced S-Cone Syndrome: Elevated Cone Counts Confer Supernormal Visual Acuity in the S-Cone Pathway

Purpose

To measure photoreceptor packing density and S-cone spatial resolution as a function of retinal eccentricity in patients with enhanced S-cone syndrome (ESCS) and to discuss the possible mechanisms supporting their supernormal S-cone acuity.

Methods

We used an adaptive optics scanning laser ophthalmoscope (AOSLO) to characterize photoreceptor packing. A custom non-AO display channel was used to measure L/M- and S-cone-mediated visual acuity during AOSLO imaging. Acuity measurements were obtained using a four-alternative, forced-choice, tumbling E paradigm along the temporal meridian between the fovea and 4° eccentricity in five of six patients and in seven control subjects. L/M acuity was tested by presenting long-pass-filtered optotypes on a black background, excluding wavelengths to which S-cones are sensitive. S-cone isolation was achieved using a two-color, blue-on-yellow chromatic adaptation method that was validated on three control subjects.

Results

Inter-cone spacing measurements revealed a near-uniform cone density profile (ranging from 0.9-1.5 arcmin spacing) throughout the macula in ESCS. For comparison, normal cone density decreases by a factor of 14 from the fovea to 6°. Cone spacing of ESCS subjects was higher than normal in the fovea and subnormal beyond 2°. Compared to the control subjects (n = 7), S-cone-mediated acuities in patients with ESCS were normal near the fovea and became increasingly supernormal with retinal eccentricity. Beyond 2°, S-cone acuities were superior to L/M-cone-mediated acuity in the ESCS cohort, a reversal of the trend observed in normal retinas.

Conclusions

Higher than normal parafoveal cone densities (presumably dominated by S-cones) confer better than normal S-cone-mediated acuity in ESCS subjects.

The Effect of Induced Intraocular Stray Light on Recognition Thresholds for Pseudo-High-Pass Filtered Letters

Purpose

The Moorfields Acuity Chart (MAC)—comprising pseudo-high-pass filtered “vanishing optotype” (VO) letters—is more sensitive to functional visual loss in age-related macular degeneration (AMD) compared to conventional letter charts. It is currently unknown the degree to which MAC acuity is affected by optical factors such as cataract. This is important to know when determining whether an individual's vision loss owes more to neural or optical factors. Here we estimate recognition acuity for VOs and conventional letters with simulated lens aging, achieved using different levels of induced intraocular light scatter.

Methods

Recognition thresholds were determined for two experienced and one naive participant with conventional and VO letters. Stimuli were presented either foveally or at 10 degrees in the horizontal temporal retina, under varying degrees of intraocular light scatter induced by white resin opacity-containing filters (WOFs grades 1 to 5).

Results

Foveal acuity only became significantly different from baseline (no filter) for WOF grade 5 with conventional letters and WOF grades 4 and 5 with VOs. In the periphery, no statistical difference was found for any stray-light level for both conventional and VOs.

Conclusions

Recognition acuity measured with conventional and VOs is robust to the effects of simulated lens opacification, and thus its higher sensitivity to neural damage should not simultaneously be confounded by such optical factors.

Translational Relevance

The MAC may be better able to differentiate between neural and optical deficits of visual performance, making it more suitable for the assessment of patients with AMD, who may display both types of functional visual loss.

Spatial Dissociation of Subretinal Drusenoid Deposits and Impaired Scotopic and Mesopic Sensitivity in AMD

Purpose

Subretinal drusenoid deposits (SDD) first appear in the rod-rich perifovea and can extend to the cone-rich fovea. To refine the spatial relationship of visual dysfunction with SDD burden, we determined the topography of mesopic and scotopic light sensitivity in participants with non-neovascular AMD with and without SDD.

Methods

Thirty-three subjects were classified into three groups: normal (n = 9), AMD-Drusen (with drusen and without SDD; n = 12), and AMD-SDD (predominantly SDD; n = 12). Mesopic and scotopic microperimetry were performed using 68 targets within the Early Treatment Diabetic Retinopathy Study grid, including points at 1.7° from the foveal center (rod:cone ratio, 0.35). Age-adjusted linear regression was used to compare mesopic and scotopic light sensitivities across groups.

Results

Across the entire Early Treatment Diabetic Retinopathy Study grid and within individual subfields, the three groups differed significantly for mesopic and scotopic light sensitivities (all P < 0.05). The AMD-SDD group exhibited significantly decreased mesopic and scotopic sensitivity versus both the normal and the AMD-Drusen groups (all P < 0.05), while AMD-Drusen and normal eyes did not significantly differ (all P > 0.05). The lowest relative sensitivities were recorded for scotopic light levels, especially in the central subfield, in the AMD-SDD group.

Conclusions

SDD-associated decrements in rod-mediated vision can be detected close to the foveola, and these deficits are proportionately worse than functional loss in the rod-rich perifovea. This finding suggests that factors other than the previously hypothesized direct cytotoxicity to photoreceptors and local transport barrier limitations may negatively impact vision. Larger prospective studies are required to confirm these observations.

Identifying the Retinal Layers Linked to Human Contrast Sensitivity Via Deep Learning

Purpose

Luminance contrast is the fundamental building block of human spatial vision. Therefore contrast sensitivity, the reciprocal of contrast threshold required for target detection, has been a barometer of human visual function. Although retinal ganglion cells (RGCs) are known to be involved in contrast coding, it still remains unknown whether the retinal layers containing RGCs are linked to a person's contrast sensitivity (e.g., Pelli-Robson contrast sensitivity) and, if so, to what extent the retinal layers are related to behavioral contrast sensitivity. Thus the current study aims to identify the retinal layers and features critical for predicting a person's contrast sensitivity via deep learning.

Methods

Data were collected from 225 subjects including individuals with either glaucoma, age-related macular degeneration, or normal vision. A deep convolutional neural network trained to predict a person's Pelli-Robson contrast sensitivity from structural retinal images measured with optical coherence tomography was used. Then, activation maps that represent the critical features learned by the network for the output prediction were computed.

Results

The thickness of both ganglion cell and inner plexiform layers, reflecting RGC counts, were found to be significantly correlated with contrast sensitivity (r = 0.26 ∼ 0.58,Ps < 0.001 for different eccentricities). Importantly, the results showed that retinal layers containing RGCs were the critical features the network uses to predict a person's contrast sensitivity (an average R² = 0.36 ± 0.10).

Conclusions

The findings confirmed the structure and function relationship for contrast sensitivity while highlighting the role of RGC density for human contrast sensitivity.

Association between Topographic Features of the Retinal Nerve Fiber Bundle and Good Visual Acuity in Patients with Glaucoma

Purpose: Maintaining visual acuity in glaucoma patients is an important part of preventing the deterioration of quality of vision. We identified specific areas of the papillomacular bundle (PMB) that were strongly associated with visual acuity, based on en-face images derived from optical coherence topography (OCT) wide scans.Methods: The study recruited 23 eyes of 21 glaucoma patients (age: 61.3 ± 13.0 years, M: F = 9:12, Humphrey field analyzer-measured mean deviation: -19.9 ± 6.5 dB) with good best-corrected visual acuity (20/20 or more) and a remaining PMB with a maximum width no more than half that of the vertical disc diameter. En-face images were derived from 12 × 9 mm wide-scan images made with DRI-OCT (Triton, Topcon). Averaged en-face images were created by identifying the disc center and fovea line (DFL) and aligning it between images. We then measured the frequency of remaining PMB at 10 µm intervals along a vertical line intersecting the DFL at its midpoint. Finally, we used a logistic analysis in a much larger group of patients to identify cases of glaucoma with low BCVA (<20/20).Results: In the averaged en-face image, the residual PMB area appeared as a high-intensity region above the DFL. Analysis showed that residual PMB was most common in an area 830-870 µm above the DFL. The correlation coefficient of residual PMB in this area to BCVA was -0.57 (p < .01), and among OCT parameters in this residual PMB area, the AUC to identify decreased BCVA was highest for ganglion cell complex thickness (0.85, p < .01), with a cutoff of 87.5 µm.Conclusions: This study identified specific areas of the PMB that were associated with BCVA in wide-scan, en-face OCT images from glaucoma patients. This suggests that it may be possible to identify visual impairment during glaucoma treatment by measuring this area.