Relationship Between Acuity and Contrast Sensitivity: Differences Due to Eye Disease

Association of Contrast Sensitivity With Eye Disease and Vision-Related Quality of Life

PURPOSE

To investigate contrast sensitivity (CS) as a screening tool to detect eye disease and assess its association with both eye disease and vision-related quality of life.

DESIGN

Cross-sectional study.

METHODS

Setting and population: Adults receiving care from a free clinic and a Federally Qualified Health Center in Michigan.

MAIN OUTCOME MEASURES

Screening positive for eye disease and Visual Function Questionnaire (VFQ) score.

OBSERVATION

Participants received a vision exam reviewed via telemedicine for disease, completed a demographic survey, and the 9-item VFQ. The ability of CS to predict eye disease was explored and area under the curve (AUC) is reported. Logistic and linear regression were used to investigate the continuous effect of CS on the probability of screening positive for eye disease and VFQ score, respectively, adjusting for age and visual acuity.

RESULTS

1159 included participants were, on average, 54.9 ± 14.5 years old, 62% identified as female, 34% as White, 54% as Black, 10% as Hispanic/Latino, and reported mean VFQ score of 79.7 ± 15.3. CS ranged from 0.00 to 1.95 log units (mean = 1.54 ± 0.24), 21% of eyes had glaucoma, 19% cataract, 6% DR, and 2% AMD. AUCs were 0.53 to 0.73. A 0.3 log unit decrease in better eye CS was associated with increased odds of glaucoma (odds ratio [OR] = 1.35, confidence interval [CI] = 1.09-1.67), cataract (OR = 1.35, CI = 1.05-1.72), DR (OR = 2.05, CI = 1.51-2.77), and AMD (OR = 2.08, CI = 1.10-3.91). A 0.3 log unit increase in better eye CS was associated with a 5.9 unit increase in VFQ.

CONCLUSION

While CS alone is not sufficient to identify people with eye disease, it is an important measure of visual function that can add value to comprehensive eye screening.

Object recognition via echoes: quantifying the crossmodal transfer of three-dimensional shape information between echolocation, vision, and haptics

Active echolocation allows blind individuals to explore their surroundings via self-generated sounds, similarly to dolphins and other echolocating animals. Echolocators emit sounds, such as finger snaps or mouth clicks, and parse the returning echoes for information about their surroundings, including the location, size, and material composition of objects. Because a crucial function of perceiving objects is to enable effective interaction with them, it is important to understand the degree to which three-dimensional shape information extracted from object echoes is useful in the context of other modalities such as haptics or vision. Here, we investigated the resolution of crossmodal transfer of object-level information between acoustic echoes and other senses. First, in a delayed match-to-sample task, blind expert echolocators and sighted control participants inspected common (everyday) and novel target objects using echolocation, then distinguished the target object from a distractor using only haptic information. For blind participants, discrimination accuracy was overall above chance and similar for both common and novel objects, whereas as a group, sighted participants performed above chance for the common, but not novel objects, suggesting that some coarse object information (a) is available to both expert blind and novice sighted echolocators, (b) transfers from auditory to haptic modalities, and (c) may be facilitated by prior object familiarity and/or material differences, particularly for novice echolocators. Next, to estimate an equivalent resolution in visual terms, we briefly presented blurred images of the novel stimuli to sighted participants (N = 22), who then performed the same haptic discrimination task. We found that visuo-haptic discrimination performance approximately matched echo-haptic discrimination for a Gaussian blur kernel σ of ~2.5°. In this way, by matching visual and echo-based contributions to object discrimination, we can estimate the quality of echoacoustic information that transfers to other sensory modalities, predict theoretical bounds on perception, and inform the design of assistive techniques and technology available for blind individuals.

Papadopoulou E, Almpanidou S, Karamitopoulos L, Almaliotis D. Evaluation of contrast sensitivity in visually impaired individuals using K-CS test. A novel smartphone-based contrast sensitivity test-Design and validation

BACKGROUND

To describe the development and investigate the accuracy of a novel smartphone-based Contrast Sensitivity (CS) application, the K-CS test.

METHODS

A total of 67 visually impaired and 50 normal participants were examined monocularly using the novel digital K-CS test and the Pelli-Robson (PR) chart. The K-CS test examines letter contrast sensitivity in logarithmic units, using eight levels of contrast from logCS = ~0,1 to logCS = ~2,1 at two spatial frequencies of 1.5 and 3 cycles per degree (cpd). The K-CS test was compared to the gold standard, PR test and intra-session test repeatability was also examined.

RESULTS

The K-CS test in normally sighted was found to agree well with the PR, providing comparable mean scores in logCS (±SD) (K-CS = 1.908 ± 0.06 versus PR = 1.93 ± 0.05) at 1.5 cpd and mean (± SD) logCS at 3 cpd (K-CS = 1.83 ± 0.13 versus PR = 1.86 ± 0.07). The mean best corrected visual acuity of visually impaired participants was 0.67 LogMAR (SD = 0.21) and the K-CS was also found to agree well with the Pelli-Robson in this group, with an equivalent mean (±SD) logCS at 1.5 cpd: (K-CS = 1.19 ± 0.27, PR = 1.15 ± 0.31), 3 cpd: K-CS = 1.01 ± 0.33, PR = 0.94 ± 0.34. Regarding the intra-session test repeatability, both the K-CS test and the PR test showed good repeatability in terms of the 95% limits of agreement (LoA): K-CS = ±0.112 at 1.5 cpd and ±0.133 at 3 cpd, PR = ±0.143 at 1.5 cpd and ±0.183 in 3 cpd in visually impaired individuals.

CONCLUSION

The K-CS test provides a quick assessment of the CS both in normally sighted and visually impaired individuals. The K-CS could serve as an alternative tool to assess contrast sensitivity function using a smartphone and provides results that agree well with the commonly used PR test.

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.

Assessment of visual function in blind mice and monkeys with subretinally implanted nanowire arrays as artificial photoreceptors

Retinal prostheses could restore image-forming vision in conditions of photoreceptor degeneration. However, contrast sensitivity and visual acuity are often insufficient. Here we report the performance, in mice and monkeys with induced photoreceptor degeneration, of subretinally implanted gold-nanoparticle-coated titania nanowire arrays providing a spatial resolution of 77.5 μm and a temporal resolution of 3.92 Hz in ex vivo retinas (as determined by patch-clamp recording of retinal ganglion cells). In blind mice, the arrays allowed for the detection of drifting gratings and flashing objects at light-intensity thresholds of 15.70-18.09 μW mm-2, and offered visual acuities of 0.3-0.4 cycles per degree, as determined by recordings of visually evoked potentials and optomotor-response tests. In monkeys, the arrays were stable for 54 weeks, allowed for the detection of a 10-μW mm-2 beam of light (0.5° in beam angle) in visually guided saccade experiments, and induced plastic changes in the primary visual cortex, as indicated by long-term in vivo calcium imaging. Nanomaterials as artificial photoreceptors may ameliorate visual deficits in patients with photoreceptor degeneration.

Effect of expansive optic flow and lateral motion parallax on depth estimation with normal and artificially reduced acuity

When an observer moves in space, the retinal projection of a stationary object either expands if the motion is toward the object or shifts horizontally if the motion contains a lateral component. This study examined the impact of expansive optic flow and lateral motion parallax on the accuracy of depth perception for observers with normal or artificially reduced acuity and asked whether any benefit is due to the continuous motion or to the discrete object image displacement. Stationary participants viewed a virtual room on a computer screen. They used an on-screen slider to estimate the depth of a target object relative to a reference object after seeing 2-second videos simulating five conditions: static viewing, expansive optic flow, and lateral motion parallax in either continuous motion or image displacement. Ten participants viewed the stimuli with normal acuity in Experiment 1 and 11 with three levels of artificially reduced acuity in Experiment 2. Linear regression models represented the relationship between the depth estimates of participants and the ground truth. Lateral motion parallax produced more accurate depth estimates than expansive optic flow and static viewing. Depth perception with continuous motion was more accurate than that with displacement under mild and moderate, but not severe, acuity reduction. For observers with both normal and artificially reduced acuity, lateral motion parallax was more helpful for object depth estimation than expansive optic flow, and continuous motion parallax was more helpful than object image displacement.

Parent-Reported Visual Concerns in Children with Cerebral Visual Impairment Presenting to a Pediatric Neurology Clinic

Purpose

Children with cerebral visual impairment (CVI) present with delayed developmental milestones. Pediatricians and pediatric neurologists are usually the first point of contact, and eye exam largely remains referral based. This study documented the visual concerns reported by parents of children with CVI visiting a pediatric neurology clinic. Additionally, we investigated the association between visual concerns, functional vision measures and visual functions.

Patients and Methods

A cross-sectional study was undertaken in children with CVI (chronological age range: 7 months-7 years). Visual concerns reported by the parents/caregivers were documented as open-ended statements. Additionally, a functional vision assessment was conducted using the CVI Range instrument with phase 1, 2 and 3 indicating low, moderate and high visual functioning, respectively. Grating acuity and contrast sensitivity were measured using Teller acuity cards-II and Ohio contrast cards respectively.

Results

A total of 73 children (mean age of 2.84 ± 1.87 years) were recruited. Sixty-eight parents reported visual concerns that were broadly grouped into 14 unique concerns. Nineteen parents (27.9%) reported more than one visual concern. Difficulty maintaining eye contact and recognizing faces were the top two visual concerns in phases 1 and 2. Missing objects in the lower visual field was the top concern in phase 3. A larger number of visual concerns were reported in phase 1 (43%) than phase 2 (40.6%) and phase 3 (16.2%). Multiple regression analysis revealed that grating acuity, contrast sensitivity and chronological age were able to predict the functional vision, F (3, 55) = 63.0, p < 0.001, r² = 0.77.

Conclusion

Targeted questions enquiring about eye contact and face recognition can be included in history elicitation in children with CVI in pediatric neurology clinics. In the presence of visual concerns, it will be important to assess grating acuity and contrast sensitivity. A poor functional vision score requires referral for eye examination and vision rehabilitation services.

The effect of filters and varying illumination on contrast sensitivity in eyes with moderate to severe visual impairment

PURPOSE

To investigate the effect of filters and illumination on contrast sensitivity in persons with cataract, pseudophakia, maculopathy and glaucoma to provide a guide for eye care providers in low vision rehabilitation.

MATERIALS AND METHODS

A within-subjects experimental design with a counter-balanced presentation technique was employed in this study. The contrast sensitivity of eyes with cataract, pseudophakia, maculopathy and glaucoma was measured with filters (no filter, yellow, pink and orange) combined with increasing illumination levels (100 lx, 300 lx, 700 lx and 1000 lx) using the SpotChecks™ contrast sensitivity chart. The data were analyzed using descriptive statistics and two-way repeated measures ANOVA.

RESULTS

The yellow filter at 100 lx significantly improved contrast sensitivity in the maculopathy group. There were no significant improvements with either intervention in the rest of the groups. There was, however, a significant interaction between filters and illumination in the cataract group.

CONCLUSION

There were small improvements in contrast sensitivity at low illumination levels with the yellow filter in the maculopathy group, and this could be considered in clinical practice and low vision rehabilitation. Overall, filters at most illumination levels did not benefit most groups.

Foveal crowding appears to be robust to normal aging and glaucoma unlike parafoveal and peripheral crowding

Visual crowding is the inability to recognize a target object in clutter. Previous studies have shown an increase in crowding in both parafoveal and peripheral vision in normal aging and glaucoma. Here, we ask whether there is any increase in foveal crowding in both normal aging and glaucomatous vision. Twenty-four patients with glaucoma and 24 age-matched normally sighted controls (mean age = 65 ± 7 vs. 60 ± 8 years old) participated in this study. For each subject, we measured the extent of foveal crowding using Pelli's foveal crowding paradigm (2016). We found that the average crowding zone was 0.061 degrees for glaucoma and 0.056 degrees for age-matched normal vision, respectively. These values fall into the range of foveal crowding zones (0.0125 degrees to 0.1 degrees) observed in young normal vision. We, however, did not find any evidence supporting increased foveal crowding in glaucoma (p = 0.375), at least in the early to moderate stages of glaucoma. In the light of previous studies on foveal crowding in normal young vision, we did not find any evidence supporting age-related changes in foveal crowding. Even if there is any, the effect appears to be rather inconsequential. Taken together, our findings suggest unlike parafoveal or peripheral crowding (2 degrees, 4 degrees, 8 degrees, and 10 degrees eccentricities), foveal crowding (<0.25 degrees eccentricity) appears to be less vulnerable to normal aging or moderate glaucomatous damage.

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.

Longitudinal Impact of Vision Impairment on Concern About Falling in People With Age-Related Macular Degeneration

Purpose

To explore the longitudinal impact of central vision loss on concern about falling (CF), over a 12-month period, in people with age-related macular degeneration (AMD).

Methods

Participants included 60 community-dwelling older people (age, 79.7 ± 6.4 years) with central vision impairment due to AMD. Binocular high-contrast visual acuity, contrast sensitivity, and visual fields were assessed at baseline and at 12 months. CF was assessed at both time points using the Falls Efficacy Scale–International (FES-I). Sensorimotor function (sit to stand, knee extension, postural sway, and walking speed) and neuropsychological function (reaction time, symptoms of anxiety and depression) were also assessed at both time points using validated instruments. Falls data were collected using monthly diaries during the 12 months.

Results

CF increased by a small but significant amount over the 12-month follow-up (2.1 units; P = 0.01), with increasing prevalence of high levels of CF (FES-I score ≥ 23), from 48% at baseline to 65% at 12 months. Linear mixed models showed that reduced contrast sensitivity was significantly associated with increased concern about falling (P= 0.004), whereas declines in both visual acuity and contrast sensitivity during the follow-up period were associated with increases in CF over the 12-month follow-up (P = 0.041 and P = 0.054, respectively), independent of age, gender, falls history, or number of comorbidities.

Conclusions

Higher levels of CF are common in older people with AMD, and levels increase over time; this increase is associated with declines in both visual acuity and contrast sensitivity. These findings highlight the need for regular assessment of both visual acuity and contrast sensitivity to identify those at greatest risk of developing higher CF.

Translational Relevance

Routine assessment of visual acuity and contrast sensitivity in older people with AMD will assist in identifying those at risk of developing high CF.

A Unified Rule for Binocular Contrast Summation Applies to Normal Vision and Common Eye Diseases

Purpose

Binocular summation refers to better visual performance with two eyes than with one eye. Little is known about the mechanism underlying binocular contrast summation in patients with common eye diseases who often exhibit binocularly asymmetric vision loss and structural changes along the visual pathway. Here we asked whether the mechanism of binocular contrast summation remains preserved in eye disease.

Methods

This study included 1035 subjects with normal ocular health, cataract, age-related macular degeneration, glaucoma, and retinitis pigmentosa. Monocular and binocular contrast sensitivity were measured by the Pelli-Robson contrast sensitivity chart. Interocular ratio (IOR) was quantified as the ratio between the poorer and better eye contrast sensitivity. Binocular summation ratio (BSR) was quantified as the ratio between binocular and better eye contrast sensitivity.

Results

All groups showed statistically significant binocular summation, with the BSR ranging from 1.25 [1.20, 1.30] in the glaucoma group to 1.31 [1.27, 1.36] in the normal vision group. There was no significant group difference in the BSR, after accounting for IOR. By fitting a binocular summation model Binocular = (Leftm + Rightm)1/m to the contrast sensitivity data, we found that the same binocular summation rule, reflected by the parameter m, applies across the five groups.

Conclusions

Cortical binocular contrast summation appears to be preserved in spite of eye diseases that can affect the two eyes differently. This finding supports the importance of assessing both monocular and binocular functions, rather than relying on a monocular assessment in the better eye as a potentially inaccurate surrogate measure.

Test-retest Repeatability of the Ohio Contrast Cards

SIGNIFICANCE

The Ohio Contrast Cards are a repeatable test of contrast sensitivity, and they reveal higher contrast sensitivity for low-vision patients than is shown by the Pelli-Robson chart.

PURPOSE

This study aimed to compare the contrast sensitivity results and test/retest ±limits of agreement for the Ohio Contrast Cards and the Pelli-Robson letter contrast sensitivity chart on two challenging groups of participants, and to compare the Ohio Contrast Card results with grating acuity and the Pelli-Robson results with letter acuity.

METHODS

The Ohio Contrast Card and Pelli-Robson tests were each performed twice by two different examiners within one visit on 40 elder patients in Primary Vision Care (>65 years old) and 23 to 27 low-vision school-aged students. Grating acuity was measured using the Teller Acuity Cards (all participants), and letter acuity was measured using ClearChart (elders) or the Bailey-Lovie chart (students).

RESULTS

The ±95% limits of agreement were similar for the Ohio Contrast Cards and the Pelli-Robson chart. The elders' limits of agreement were ±0.27 (Ohio Contrast Cards) and ±0.28 (Pelli-Robson); the students' limits of agreement were ±0.42 (Ohio Contrast Cards) and ±0.51 (Pelli-Robson). However, Ohio Contrast Card results were 0.41 log10 Michelson units more sensitive than the Pelli-Robson chart (over one line on the Pelli-Robson chart) for the elders and 0.90 log10 Michelson units (three lines on the Pelli-Robson chart) more sensitive for the elders (0.11 and 0.6 log10 Weber units, respectively). The Pelli-Robson results were correlated with letter acuities and Ohio Contrast Card results for both groups, and the Ohio Contrast Card results were correlated with Teller Acuity Card acuities for the elders.

CONCLUSIONS

The Ohio Contrast Cards and Pelli-Robson chart are similarly repeatable. Both contrast sensitivity tests can provide additional clinical information that is not available through visual acuity testing, and Ohio Contrast Card may provide additional information not available from the Pelli-Robson chart.

Simulating Visibility and Reading Performance in Low Vision

PURPOSE

Low vision reduces text visibility and causes difficulties in reading. A valid low-vision simulation could be used to evaluate the accessibility of digital text for readers with low vision. We examined the validity of a digital simulation for replicating the text visibility and reading performance of low-vision individuals.

METHODS

Low-vision visibility was modeled with contrast sensitivity functions (CSFs) with parameters to represent reduced acuity and contrast sensitivity. Digital filtering incorporating these CSFs were applied to digital versions of the Lighthouse Letter Acuity Chart and the Pelli-Robson Contrast Sensitivity Chart. Reading performance (reading acuity, critical print size, and maximum reading speed) was assessed with filtered versions of the MNREAD reading acuity Chart. Thirty-six normally sighted young adults completed chart testing under normal and simulated low-vision conditions. Fifty-eight low-vision subjects (thirty with macular pathology and twenty-eight with non-macular pathology) and fifteen normally sighted older subjects completed chart testing with their habitual viewing. We hypothesized that the performance of the normally sighted young adults under simulated low-vision conditions would match the corresponding performance of actual low-vision subjects.

RESULTS

When simulating low-vision conditions with visual acuity better than 1.50 logMAR (Snellen 20/630) and contrast sensitivity better than 0.15 log unit, the simulation adequately reduced the acuity and contrast sensitivity in normally sighted young subjects to the desired low-vision levels. When performing the MNREAD test with simulated low vision, the normally sighted young adults had faster maximum reading speed than both the Non-macular and Macular groups, by an average of 0.07 and 0.12 log word per minute, respectively. However, they adequately replicated the reading acuity as well as the critical print size, up to 2.00 logMAR of both low-vision groups.

CONCLUSION

A low-vision simulation based on clinical measures of visual acuity and contrast sensitivity can provide good estimates of reading performance and the accessibility of digital text for a broad range of low-vision conditions.

The Effects of 0.01% Atropine on Adult Myopes' Contrast Sensitivity

Purpose

Atropine at a low concentration is considered a safe and effective treatment to mitigate myopia progression. However, the potential unwanted side effects of administering atropine at a low dose on visual functions other than best corrected visual acuity has not been investigated. In this study, we investigate the short-term (12,16, and 20 h) and long-term (1, 2, and 4 weeks) effects of 0.01% atropine (i.e., 0.1 mg/ml) on contrast sensitivity (CS) in patients with myopia.

Methods

Thirty adults (23.33 ± 2.93 years old) with myopia between -1.00 and -6.00 diopters (D), astigmatism of -1.50 D or less, and anisometropia of 1.00 D or less, participated in this prospective, masked, placebo-controlled, randomized study. The participants were randomly assigned to receive 0.01% atropine or polyvinyl alcohol eye drops once nightly to both eyes for four weeks. CS was measured binocularly at baseline and 12, 16, 20 h, 1, 2, and 4 weeks after the first use of the eye drops.

Results

There was no statistically significant differences of CS found between atropine and placebo-controlled groups in both short-term and long-term. There was no statistically significant interaction effect found between the time and group.

Conclusion

We demonstrated no significant deleterious effect of 0.01% atropine on adult myopes’ CS.