Linkage between retinal ganglion cell density and the nonuniform spatial integration across the visual field.

The ability to integrate visual information over space is a fundamental component of human pattern vision. Regardless of whether it is for detecting luminance contrast or for recognizing objects in a cluttered scene, the position of the target in the visual field governs the size of a window within which visual information is integrated. Here we analyze the relationship between the topographic distribution of ganglion cell density and the nonuniform spatial integration across the visual field. The extent of spatial integration for luminance detection (Ricco's area) and object recognition (crowding zone) are measured at various target locations. The number of retinal ganglion cells (RGCs) underlying Ricco's area or crowding zone is estimated by computing the product of Ricco's area (or crowding zone) and RGC density for a given target location. We find a quantitative agreement between the behavioral data and the RGC density: The variation in the sampling density of RGCs across the human retina is closely matched to the variation in the extent of spatial integration required for either luminance detection or object recognition. Our empirical data combined with the simulation results of computational models suggest that a fixed number of RGCs subserves spatial integration of visual input, independent of the visual-field location.

Altered eye movements during reading under degraded viewing conditions: Background luminance, text blur, and text contrast.

Degraded viewing conditions caused by either natural environments or visual disorders lead to slow reading. Here, we systematically investigated how eye movement patterns during reading are affected by degraded viewing conditions in terms of spatial resolution, contrast, and background luminance. Using a high-speed eye tracker, binocular eye movements were obtained from 14 young normally sighted adults. Images of text passages were manipulated with varying degrees of background luminance (1.3-265 cd/m2), text blur (severe blur to no blur), or text contrast (2.6%-100%). We analyzed changes in key eye movement features, such as saccades, microsaccades, regressive saccades, fixations, and return-sweeps across different viewing conditions. No significant changes were observed for the range of tested background luminance values. However, with increasing text blur and decreasing text contrast, we observed a significant decrease in saccade amplitude and velocity, as well as a significant increase in fixation duration, number of fixations, proportion of regressive saccades, microsaccade rate, and duration of return-sweeps. Among all, saccade amplitude, fixation duration, and proportion of regressive saccades turned out to be the most significant contributors to reading speed, together accounting for 90% of variance in reading speed. Our results together showed that, when presented with degraded viewing conditions, the patterns of eye movements during reading were altered accordingly. These findings may suggest that the seemingly deviated eye movements observed in individuals with visual impairments may be in part resulting from active and optimal information acquisition strategies operated when visual sensory input becomes substantially deprived.

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.

Cortical Reorganization of Peripheral Vision Induced by Simulated Central Vision Loss.

When one's central vision is deprived, a spared part of the peripheral retina acts as a pseudofovea for fixation. The neural mechanisms underlying this compensatory adjustment remain unclear. Here we report cortical reorganization induced by simulated central vision loss. Human subjects of both sexes learned to place the target at an eccentric retinal locus outside their blocked visual field for object tracking. Before and after training, we measured visual crowding-a bottleneck of object identification in peripheral vision, using psychophysics and fMRI. We found that training led to an axis-specific reduction of crowding. The change of the crowding effect was reflected in the change of BOLD signal, as a release of cortical suppression in multiple visual areas starting as early as V1. Our findings suggest that the adult visual system is capable of reshaping its oculomotor control and sensory coding to adapt to impoverished visual input.SIGNIFICANCE STATEMENT By simulating central vision loss in normally sighted adults, we found that oculomotor training not only induces PRL, but also facilitates form processing in peripheral vision. As subjects learned to place the target at an eccentric retinal locus, "visual crowding"-the detrimental effect of clutter on peripheral object identification-was reduced. The reduction of the crowding effect was accompanied by a release of response suppression in the visual cortex. These findings indicate that the adult visual system is capable of reshaping the peripheral vision to adapt to central vision loss.

An allometric pharmacokinetic model and minimum effective analgesic concentration of fentanyl in patients undergoing major abdominal surgery.

BACKGROUND: We aimed to characterise the population pharmacokinetics of fentanyl in adults and to determine the minimum effective concentration (MEC) and minimum effective analgesic concentration (MEAC) of i.v. fentanyl in patients after major abdominal open surgery. METHODS: In the pharmacokinetic study, subjects received an intravenous bolus of fentanyl 100 µg during operation, and arterial blood was sampled at pre-set intervals. In addition, data from previously published fentanyl pharmacokinetic studies were incorporated to build a pharmacokinetic model. In the MEAC study, subjects were asked to rate their pain every 10 min using a VAS (0=no pain, 10=most severe pain) in the PACU. The first blood sample was obtained when wound pain was rated as ≥3 at rest or ≥5 during compression. Then, fentanyl 50 µg was administered every 10 min until the pain intensity had decreased to <3 at rest and <5 during compression, at which point the second blood was sampled and the first MEAC of fentanyl was measured. The same procedure was repeated to obtain a third sample (MEC) and a fourth sample (second MEAC). RESULTS: In the population pharmacokinetic study (n=95), the plasma concentration of fentanyl over time was well-described by the three-compartment mammillary model using an allometric expression. The V1, V2, V3, Cl, Q1, and Q2 of a 70 kg subject were 10.1, 26.5, 206 L, 0.704, 2.38, and 1.49 L min-1, respectively. In the MEAC study (n=30), the median (inter-quartile range) MEC and MEAC were 0.72 (0.58-1.05) ng ml-1, and 0.99 (0.76-1.28) ng ml-1, respectively. CONCLUSION: These results provide a scientific basis for the use of fentanyl for acute postoperative pain management in surgical patients. CLINICAL TRIAL REGISTRATION: KCT0003273 (http://cris.nih.go.kr).

Three-dimensional binocular eye-hand coordination in normal vision and with simulated visual impairment.

Sensorimotor coupling in healthy humans is demonstrated by the higher accuracy of visually tracking intrinsically-rather than extrinsically-generated hand movements in the fronto-parallel plane. It is unknown whether this coupling also facilitates vergence eye movements for tracking objects in depth, or can overcome symmetric or asymmetric binocular visual impairments. Human observers were therefore asked to track with their gaze a target moving horizontally or in depth. The movement of the target was either directly controlled by the observer's hand or followed hand movements executed by the observer in a previous trial. Visual impairments were simulated by blurring stimuli independently in each eye. Accuracy was higher for self-generated movements in all conditions, demonstrating that motor signals are employed by the oculomotor system to improve the accuracy of vergence as well as horizontal eye movements. Asymmetric monocular blur affected horizontal tracking less than symmetric binocular blur, but impaired tracking in depth as much as binocular blur. There was a critical blur level up to which pursuit and vergence eye movements maintained tracking accuracy independent of blur level. Hand-eye coordination may therefore help compensate for functional deficits associated with eye disease and may be employed to augment visual impairment rehabilitation.

Common constraints limit Korean and English character recognition in peripheral vision.

The visual span refers to the number of adjacent characters that can be recognized in a single glance. It is viewed as a sensory bottleneck in reading for both normal and clinical populations. In peripheral vision, the visual span for English characters can be enlarged after training with a letter-recognition task. Here, we examined the transfer of training from Korean to English characters for a group of bilingual Korean native speakers. In the pre- and posttests, we measured visual spans for Korean characters and English letters. Training (1.5 hours × 4 days) consisted of repetitive visual-span measurements for Korean trigrams (strings of three characters). Our training enlarged the visual spans for Korean single characters and trigrams, and the benefit transferred to untrained English symbols. The improvement was largely due to a reduction of within-character and between-character crowding in Korean recognition, as well as between-letter crowding in English recognition. We also found a negative correlation between the size of the visual span and the average pattern complexity of the symbol set. Together, our results showed that the visual span is limited by common sensory (crowding) and physical (pattern complexity) factors regardless of the language script, providing evidence that the visual span reflects a universal bottleneck for text recognition.

Effects of mindfulness-based intervention to improve task performance for children with intellectual disabilities.

BACKGROUND: Task performance is a critical factor for learning in individuals with intellectual disabilities. This study aimed to examine mindfulness-based intervention (MBI) to improve task performance for children with intellectual disability (ID). METHODS: Three elementary school children with ID participated in the study. A multiple baseline design across subjects was used. The intervention was consisted of "understanding the necessary concept of mindfulness, practice of awareness and attention, and practice focusing on mindful behaviours." Mediating materials including expressive arts supplies were used to help each subject to understand the content and the progress of the intervention programme. RESULTS: The results showed that all of the three subjects showed an improvement in task performance and a decrease in task-avoidance behaviours. The mothers reported that her children's daily life behaviours were distinctively improved as he/she participated in the intervention. CONCLUSION: The finding suggests that MBI would be a valuable adjunct to a wide range of applications to support individuals with ID to learn a variety of adaptive behaviour.

Association between Glaucoma and At-fault Motor Vehicle Collision Involvement among Older Drivers: A Population-based Study.

OBJECTIVE: To examine the association between glaucoma and motor vehicle collision (MVC) involvement among older drivers, including the role of visual field impairment that may underlie any association found. DESIGN: A retrospective, population-based study. PARTICIPANTS: A sample of 2000 licensed drivers aged ≥70 years who reside in north central Alabama. METHODS: At-fault MVC involvement over the 5 years before enrollment was obtained from state records. Three aspects of visual function were measured: habitual binocular distance visual acuity, binocular contrast sensitivity (CS), and the binocular driving visual field constructed from combining the monocular visual fields of each eye. Poisson regression was used to calculate crude and adjusted rate ratios (RRs) and 95% confidence intervals (CIs). MAIN OUTCOMES MEASURES: At-fault MVC involvement over the 5 years before enrollment. RESULTS: Drivers with glaucoma (n = 206) had a 1.65 times higher MVC rate (95% CI, 1.20-2.28; P = 0.002) compared with those without glaucoma after adjusting for age, and mental status. Among those with glaucoma, drivers with severe visual field loss had higher MVC rates (RR, 2.11; 95% CI, 1.09-4.09; P = 0.027), whereas no association was found among those with impaired visual acuity and CS. When the visual field was subdivided into 6 regions (upper, lower, left, and right visual fields; horizontal and vertical meridians), we found that impairment in the left, upper, or lower visual field was associated with higher MVC rates, and an impaired left visual field showed the highest RR (3.16; P = 0.001) compared with other regions. However, no association was found in deficits in the right side or along the horizontal or vertical meridian. CONCLUSIONS: A population-based study suggests that older drivers with glaucoma are more likely to have a history of at-fault MVC involvement than those without glaucoma. Impairment in the driving visual field in drivers with glaucoma seems to have an independent association with at-fault MVC involvement, whereas visual acuity and CS impairments do not.

Integrating oculomotor and perceptual training to induce a pseudofovea: A model system for studying central vision loss.

People with a central scotoma often adopt an eccentric retinal location (Preferred Retinal Locus, PRL) for fixation. Here, we proposed a novel training paradigm as a model system to study the nature of the PRL formation and its impacts on visual function. The training paradigm was designed to effectively induce a PRL at any intended retinal location by integrating oculomotor control and pattern recognition. Using a gaze-contingent display, a simulated central scotoma was induced in eight normally sighted subjects. A subject's entire peripheral visual field was blurred, except for a small circular aperture with location randomly assigned to each subject (to the left, right, above, or below the scotoma). Under this viewing condition, subjects performed a demanding oculomotor and visual recognition task. Various visual functions were tested before and after training at both PRL and nonPRL locations. After 6-10 hr of the training, all subjects formed their PRL within the clear window. Both oculomotor control and visual recognition performance significantly improved. Moreover, there was considerable improvement at PRL location in high-level function, such as trigram letter-recognition, reading, and spatial attention, but not in low-level function, such as acuity and contrast sensitivity. Our results demonstrated that within a relatively short time, a PRL could be induced at any intended retinal location in normally-sighted subjects with a simulated scotoma. Our training paradigm might not only hold promise as a model system to study the dynamic nature of the PRL formation, but also serve as a rehabilitation regimen for individuals with central vision loss.

Radial-tangential anisotropy of crowding in the early visual areas.

Crowding, the inability to recognize an individual object in clutter (Bouma H. Nature 226: 177-178, 1970), is considered a major impediment to object recognition in peripheral vision. Despite its significance, the cortical loci of crowding are not well understood. In particular, the role of the primary visual cortex (V1) remains unclear. Here we utilize a diagnostic feature of crowding to identify the earliest cortical locus of crowding. Controlling for other factors, radially arranged flankers induce more crowding than tangentially arranged ones (Toet A, Levi DM. Vision Res 32: 1349-1357, 1992). We used functional magnetic resonance imaging (fMRI) to measure the change in mean blood oxygenation level-dependent (BOLD) response due to the addition of a middle letter between a pair of radially or tangentially arranged flankers. Consistent with the previous finding that crowding is associated with a reduced BOLD response [Millin R, Arman AC, Chung ST, Tjan BS. Cereb Cortex (July 5, 2013). doi:10.1093/cercor/bht159], we found that the BOLD signal evoked by the middle letter depended on the arrangement of the flankers: less BOLD response was associated with adding the middle letter between radially arranged flankers compared with adding it between tangentially arranged flankers. This anisotropy in BOLD response was present as early as V1 and remained significant in downstream areas. The effect was observed while subjects' attention was diverted away from the testing stimuli. Contrast detection threshold for the middle letter was unaffected by flanker arrangement, ruling out surround suppression of contrast response as a major factor in the observed BOLD anisotropy. Our findings support the view that V1 contributes to crowding.

Placing a saline bag underneath the heart enhances transgastric transesophageal echocardiographic imaging during cardiac displacement for off-pump coronary artery bypass surgery.

OBJECTIVE: The authors hypothesized that placing a saline bag (saline-filled surgical glove) underneath a displaced heart would improve ultrasound transmission for transgastric (TG) imaging and transesophageal echocardiography (TEE) to visualize left ventricular regional wall motion (LV-RWM) during cardiac displacement for off-pump coronary artery bypass (OPCAB) surgery. DESIGN: Prospective observational study. SETTING: Tertiary University Hospital. PARTICIPANTS: Adult patients undergoing OPCAB surgery. INTERVENTIONS: Intraoperative TEE examination MEASUREMENT AND MAIN RESULTS: For off-line analyses of LV-readable segments, mid-esophageal (ME, 4-chamber, 2-chamber, and long-axis) and TG (basal- and mid-short-axis) TEE views were recorded under 3 different intraoperative conditions in 13 cases of OPCAB surgery: Before cardiac displacement (Tcontrol), after cardiac displacement (Tdisplaced), and after placing the saline bag underneath the displaced heart (Tsaline-bag). There were more LV-readable segments in the 17-segment model using integrated ME and TG views(ME + TG views) at Tsaline-bag and Tcontrol (mean[95% confidence interval], 17[17-17] and 17[17-17]) than using ME+TG at Tdisplaced (15[15-16], P = 0.002 and P<0.001, respectively). Using ME + TG views provided more LV-readable segments in the 17-segment model than using ME views at Tsaline-bag (vs. 16[14-16], P < 0.001), but not at Tdisplaced (vs. 15[14-15]). Incidences of inadequate RWM monitoring (LV-readable segments<14/17 using ME + TG views) at Tsaline-bag and Tcontrol (all 0/13) were less frequent than at Tdisplaced (3/13, all P = 0.038). There were more LV-readable segments in TG basal- and mid-short-axis views at Tsaline-bag (median [range], 6[5-6] and 5[5-6]) than at Tdisplaced (0[0-2] and 0[0-1], all P < 0.05). CONCLUSIONS: Placing a saline bag underneath the displaced heart enhances the ability of TEE to visualize global LV-RWM by improving TG TEE imaging during OPCAB surgery.

Impact of Glaucomatous Ganglion Cell Damage on Central Visual Function.

Glaucoma, a leading cause of irreversible blindness, is characterized by the progressive loss of retinal ganglion cells (RGCs) and subsequent visual field defects. RGCs, as the final output neurons of the retina, perform key computations underpinning human pattern vision, such as contrast coding. Conventionally, glaucoma has been associated with peripheral vision loss, and thus, relatively little attention has been paid to deficits in central vision. However, recent advancements in retinal imaging techniques have significantly bolstered research into glaucomatous damage of the macula, revealing that it is prevalent even in the early stages of glaucoma. Thus, it is an opportune time to explore how glaucomatous damage undermines the perceptual processes associated with central visual function. This review showcases recent studies addressing central dysfunction in the early and moderate stages of glaucoma. It further emphasizes the need to characterize glaucomatous damage in both central and peripheral vision, as they jointly affect an individual's everyday activities.

Correction: Compensation for Blur Requires Increase in Field of View and Viewing Time.

[This corrects the article DOI: 10.1371/journal.pone.0162711.].

Estimating Visual Acuity Without a Visual Acuity Chart.

Purpose: This study explored whether visual acuity (VA) can be inferred from self-reported ability to recognize everyday objects using a set of yes/no questions. Methods: Participants answered 100 yes/no questions designed to assess their ability to recognize familiar objects at typical viewing distances, such as distinguishing between a full moon and a half moon on a clear night. The questions demanded VA ranging from normal to severe vision impairment. Responses were analyzed using item response theory, and the results were compared with participants' VA values. Results: We recruited 385 participants from 4 sites in the United States. Participants had a mean age of 56.7 years with VA ranging from -0.3 to 2.0 logarithm of the minimum angle of resolution (logMAR) (mean = 0.58). A strong relationship was observed between participants' estimated vision ability and their VA (r = -0.72). The linear relationship can be used to predict each participant's VA based on their estimated vision ability. The average signed and unsigned prediction errors were 0 and 0.24 logMAR, respectively, with a coefficient of repeatability of 0.59 logMAR between the estimated VA and measured VA. The same linear function was used to determine the VA limit required for each question. For instance, the VA limit for the moon question was 1.0 logMAR. Conclusions: Yes/no questions about everyday visual activities have the potential to estimate an individual's VA. Future refinements may enhance reliability. Translational Relevance: The survey provides insights into the real-world visual capabilities of people with low vision, making it potentially useful for telehealth applications.

The effects of the Trendelenburg position and intrathoracic pressure on the subclavian cross-sectional area and distance from the subclavian vein to pleura in anesthetized patients.

BACKGROUND: The effects of maneuvers to increase intrathoracic pressure and of Trendelenburg position on the cross-sectional area (CSA) of the subclavian vein (SCV) and the relationship between the SCV and adjacent structures have not been investigated. METHODS: In ultrasonography-guided SCV catheterization (N = 30), the CSA of the SCV and the distance between the SCV and pleura (DSCV-pleura) were determined during 10-second airway opening, and 10-second positive inspiratory hold with 20 cm H2O in the supine position (S-0, and S-20) and the 10° Trendelenburg position (T-0, and T-20). In addition to a statistical significance of P < 0.05, CSA and DSCV-pleura differences of ≥15% were defined as clinically relevant changes. RESULTS: CSA (mean [95% confidence interval]) in S-20, T-0, and T-20 (1.02 [0.95-1.14] cm(2), 1.04 [0.95-1.15] cm(2), and 1.14 [1.04-1.24] cm(2), respectively) was significantly larger than a CSA in S-0 (0.93 [0.86-1.00] cm(2), all P < 0.001). However, only the increase of CSA in T-20 vs S-0 (0.21 cm(2), 23.2%) was clinically meaningful (≥15%). The number of patients who showed CSA increase ≥15% was more in S-0 to T-20 (57%) compared with those in S-0 to S-20 (23%) and S-0 to T-0 (27%). DSCV-pleura measurements (mean) in S-20 and T-20 (0.61 and 0.60 cm) were significantly shorter than those in S-0 (0.70 cm, all P < 0.001), but the reductions of DSCV-pleura were not clinically meaningful (≥15%). CONCLUSIONS: The combined application of inspiratory hold and Trendelenburg position provided a greater and more relevant degree of CSA increase without compromising DSCV-pleura, which may facilitate SCV catheterization. Further investigations are needed to determine whether these results affect the success rate of catheterization and the risk of procedural injury.

Higher-contrast requirements for recognizing low-pass-filtered letters.

Kwon and Legge (2011) found that high levels of letter recognition accuracy are possible even when letters are severely low-pass filtered (0.9 cycles per letter). How is letter recognition possible with such severe reduction in the spatial resolution of stimulus letters? Clues may come from understanding the possible interaction between contrast and spatial resolution in letter recognition. Here, we asked what the effect is on the contrast threshold for detecting and recognizing letters as the spatial-frequency cutoff of letters is reduced (in cycles per letter). We measured contrast thresholds of seven normally sighted subjects for detecting and recognizing single letters of the English alphabet. The letters were low-pass filtered with several cutoff frequencies (0.9-3.5 cycles per letter, including unfiltered letters). We found that differences in contrast thresholds between detection and recognition increased substantially with decreasing cutoff frequency. We also incorporated the human contrast sensitivity function into an ideal observer model and found qualitatively good agreement between the pattern of performance for the model and our human subjects. Our findings show that the human visual system requires higher contrast for letter recognition when spatial resolution is severely limited. Good agreement between the model and human subjects shows that the greater contrast requirement for recognizing low-pass letters is due to a reduction in the information content of the letters rather than a change in human visual processing. The reduction in stimulus information may be due to increasing stimulus similarity associated with a reduction in spatial-frequency cutoff.

Altered Eye Movements During Reading With Simulated Central and Peripheral Visual Field Defects.

Purpose: Although foveal vision provides fine spatial information, parafoveal and peripheral vision are also known to be important for efficient reading behaviors. Here we systematically investigate how different types and sizes of visual field defects affect the way visual information is acquired via eye movements during reading. Methods: Using gaze-contingent displays, simulated scotomas were induced in 24 adults with normal or corrected-to-normal vision during a reading task. The study design included peripheral and central scotomas of varying sizes (aperture or scotoma size of 2°, 4°, 6°, 8°, and 10°) and no-scotoma conditions. Eye movements (e.g., forward/backward saccades, fixations, microsaccades) were plotted as a function of either the aperture or scotoma size, and their relationships were characterized by the best fitting model. Results: When the aperture size of the peripheral scotoma decreased below 6° (11 visible letters), there were significant decreases in saccade amplitude and velocity, as well as substantial increases in fixation duration and the number of fixations. Its dependency on the aperture size is best characterized by an exponential decay or growth function in log-linear coordinates. However, saccade amplitude and velocity, fixation duration, and forward/regressive saccades increased more or less linearly with increasing central scotoma size in log-linear coordinates. Conclusions: Our results showed differential impacts of central and peripheral vision loss on reading behaviors while lending further support for the importance of foveal and parafoveal vision in reading. These apparently deviated oculomotor behaviors may in part reflect optimal reading strategies to compensate for the loss of visual information.

Reading Vision in Adults With Early and Intermediate Age-Related Macular Degeneration Under Mesopic and Photopic Conditions.

Purpose: Reading is involved in various daily activities that operate under a wide range of luminance levels. Rod- and cone-mediated mesopic visual function is known to be impaired even in early/intermediate age-related macular degeneration (AMD). It remains unclear whether and to what extent mesopic reading is impaired in early/intermediate AMD. Here, we assessed differences in reading vision between photopic and mesopic conditions in early/intermediate AMD and compared their performance to those in older adults with normal macular health. Methods: The study included 30 patients with early/intermediate AMD and 30 healthy controls. Reading performance was tested on the MNREAD iPad app under mesopic (2 cd/m2 with a neural-density filter) and photopic (220 cd/m2) conditions. Four reading indices-maximum reading speed (MRS), critical print size (CPS), reading acuity (RA), and reading accessibility index (ACC)-were obtained from the MNREAD test, yielding a function representing reading speed versus print size. Results: Compared to photopic conditions, patients with AMD and healthy controls both exhibited noticeable decreases in reading vision under mesopic conditions (P < 0.001) despite normal photopic visual acuity. This decrease was more pronounced in AMD even after adjusting for age (P < 0.001): Under mesopic conditions, MRS and ACC decreased by 8 words per minute and 0.1, respectively; CPS and RA were enlarged by 0.27 and 0.24 logMAR, respectively. Conclusions: Reading vision deteriorates under mesopic conditions compared to photopic conditions in early/intermediate AMD and is accentuated compared to this difference in healthy controls. Translational Relevance: A mesopic reading test may provide a more sensitive and comprehensive assessment of a patient's reading impairment.

Despite Impaired Binocular Function, Binocular Disparity Integration Across the Visual Field Is Spared in Normal Aging and Glaucoma.

Purpose: To examine how binocularly asymmetric glaucomatous visual field damage affects binocular disparity processing across the visual field. Methods: We recruited 18 patients with primary open-angle glaucoma, 16 age-matched controls, and 13 young controls. Participants underwent standard clinical assessments of binocular visual acuity, binocular contrast sensitivity, stereoacuity, and perimetry. We employed a previously validated psychophysical procedure to measure how sensitivity to binocular disparity varied across spatial frequencies and visual field sectors (i.e., with full-field stimuli spanning the central 21° of the visual field and with stimuli restricted to annular regions spanning 0°-3°, 3°-9°, or 9°-21°). We employed measurements with annular stimuli to model different possible scenarios regarding how disparity information is combined across visual field sectors. We adjudicated between potential mechanisms by comparing model predictions to the patterns observed with full-field stimuli. Results: Perimetry confirmed that patients with glaucoma exhibited binocularly asymmetric visual field damage (P < 0.001). Across participant groups, foveal regions preferentially processed disparities at finer spatial scales, whereas periphery regions were tuned for coarser scales (P < 0.001). Disparity sensitivity also decreased from fovea to periphery (P < 0.001) and across participant groups (Ps < 0.01). Finally, similar to controls, patients with glaucoma exhibited near-optimal disparity integration, specifically at low spatial frequencies (P < 0.001). Conclusions: Contrary to the conventional view that glaucoma spares central vision, we find that glaucomatous damage causes a widespread loss of disparity sensitivity across both foveal and peripheral regions. Despite these losses, cortical integration mechanisms appear to be well preserved, suggesting that patients with glaucoma make the best possible use of their remaining binocular function.