Preferred retinal loci and macular scotoma characteristics in patients with age-related macular degeneration

Development and Validation of Performance-Based Assessment of Daily Living Tasks in Age-Related Macular Degeneration

Purpose

To establish the reliability and validity of five performance-based activities of daily living task tests (ADLTT), to correlate structure to function, to evaluate the impact of visual impairment (VI) on age-related macular degeneration (AMD), and to develop new outcome measures.

Methods

A multidisciplinary team developed five ADLTTs: (1) reading test (RT); (2) facial expression (FE) recognition; (3) item search (IS) task; (4) money counting (MC) task; and (5) making a drink (MD), tested with binocular and monocular vision. ADLTTs were tested for known-group (i.e., difference between AMD group and controls) and convergent (i.e., correlation to other measures of visual function), validity metrics, and test-retest reliability in 36 patients with VI (visual acuity (logMAR VA > 0.4) in at least one eye caused by AMD versus 36 healthy controls without VI.

Results

Compared to controls, AMD patients had a slower reading speed (-77.41 words/min; P < 0.001); took longer to complete MC using monocular worse eye and binocular vision (15.13 seconds and 4.06 seconds longer compared to controls, respectively; P < 0.001); and MD using monocular worse eye vision (9.37 sec; P = 0.033), demonstrating known-group validity. Only RT and MC demonstrated convergent validity, showing correlations with VA, contrast sensitivity, and microperimetry testing. Moderate to good test-retest reliability was observed for MC and MD (interclass correlation coefficient = 0.55 and 0.77; P < 0.001) using monocular worse eye vision.

Conclusions

Real-world ADL functioning associated with VI-related AMD can be assessed with our validated ADLTTs, particularly MC and MD.

Translational Relevance

This study validates visual function outcome measures that are developed for use in future clinical practice and clinical trials.

Saccadic re-referencing training with gaze-contingent FRL-'fixation': Effects of scotoma type and size adaptation

Foveal vision loss makes the fovea as saccadic reference point maladaptive. Training programs have been proposed that shift the saccadic reference point from the fovea to an extrafoveal location, just outside the area of vision loss. We used a visual search task to train normal-sighted participants to fixate target items with a predetermined 'forced retinal location' (FRL) adjacent to a simulated central scotoma. We found that training was comparatively successful for scotomata that had either a sharp or blurry demarcation from the background. Completing the task with sharp-edged scotoma resulted in overall higher training gains. Training with blurry-edged scotoma, however, yielded overall better results when scotoma size was increased after training and participants needed to adapt to a more eccentric FRL, as may be necessary in patients with progressive degenerative eye diseases.

Efficient versus inefficient visual search as training for saccadic re-referencing to an extrafoveal location

Central vision loss is one of the leading causes of visual impairment in the elderly and its frequency is increasing. Without formal training, patients adopt an unaffected region of the retina as a new fixation location, a preferred retinal locus (PRL). However, learning to use the PRL as a reference location for saccades, that is, saccadic re-referencing, is protracted and time-consuming. Recent studies showed that training with visual search tasks can expedite this process. However, visual search can be driven by salient external features - leading to efficient search, or by internal goals, usually leading to inefficient, attention-demanding search. We compared saccadic re-referencing training in the presence of a simulated central scotoma with either an efficient or an inefficient visual search task. Participants had to respond by fixating the target with an experimenter-defined retinal location in the lower visual field. We observed that comparable relative training gains were obtained in both tasks for a number of behavioral parameters, with higher training gains for the trained task, compared to the untrained task. The transfer to the untrained task was only observed for some parameters. Our findings thus confirm and extend previous research showing comparable efficiency for exogenously and endogenously driven visual search tasks for saccadic re-referencing training. Our results also show that transfer of training gains to related tasks may be limited and needs to be tested for saccadic re-referencing-training paradigms to assess its suitability as a training tool for patients.

The Saccade Main Sequence in Patients With Retinitis Pigmentosa and Advanced Age-Related Macular Degeneration

Purpose

Most eye-movement studies in patients with visual field defects have examined the strategies that patients use while exploring a visual scene, but they have not investigated saccade kinematics. In healthy vision, saccade trajectories follow the remarkably stereotyped "main sequence": saccade duration increases linearly with saccade amplitude; peak velocity also increases linearly for small amplitudes, but approaches a saturation limit for large amplitudes. Recent theories propose that these relationships reflect the brain's attempt to optimize vision when planning eye movements. Therefore, in patients with bilateral retinal damage, saccadic behavior might differ to optimize vision under the constraints imposed by the visual field defects.

Methods

We compared saccadic behavior of patients with central vision loss, due to age-related macular degeneration (AMD), and patients with peripheral vision loss, due to retinitis pigmentosa (RP), to that of controls with normal vision (NV) using a horizontal saccade task.

Results

Both patient groups demonstrated deficits in saccade reaction times and target localization behavior, as well as altered saccade kinematics. Saccades were generally slower and the shape of the velocity profiles were often atypical, especially in the patients with RP. In the patients with AMD, the changes were far less dramatic. For both groups, saccade kinematics were affected most when the target was in the subjects' blind field.

Conclusions

We conclude that defects of the central and peripheral retina have distinct effects on the saccade main sequence, and that visual inputs play an important role in planning the kinematics of a saccade.

A gaze-contingent saccadic re-referencing training with simulated central vision loss

Patients with central vision loss (CVL) adopt an eccentric retinal location for fixation, a preferred retinal location (PRL), to compensate for vision loss at the fovea. Although most patients with CVL are able to rapidly use a PRL instead of the fovea, saccadic re-referencing to a PRL develops slowly. Without re-referencing, saccades land the saccade target in the scotoma. This results in corrective saccades and leads to inefficient visual exploration. Here, we tested a new method to train saccadic re-referencing. Healthy participants performed gaze-contingent visual search tasks with simulated central scotoma in which participants had to fixate targets with an experimenter-defined forced retinal location (FRL). In experiment 1, we compared single-target search and foraging search tasks in the course of five training sessions. Results showed that both tasks improved the efficiency of gaze sequences and led to saccadic re-referencing to the FRL. In experiment 2, we trained participants extensively for 25 sessions, both with and without a gaze-contingent FRL-marker visible during training. After extensive training, observers' performance approached that of foveal vision. Thus, gaze-contingent FRL-fixation may become an efficient tool for saccadic re-referencing training in patients with central vision loss.

Multi-res: An interface for improving reading without central vision

Loss of sharp foveal vision, as is inherent to Macular Degeneration (MD), severely impacts reading. One strategy for preserving patients' reading ability involves a one-by-one serial visual presentation (SVP) of words, whereby words are viewed extrafoveally. However, the method is limited as patients often retain the natural tendency to foveate words, thus bringing those words in the scotomal region. Additionally, SVP offers no compensation for the fact that orthographic input is degraded outside the fovea. Addressing these issues, here we tested a novel interface wherein texts are presented word-by-word, but with multiple repetitions (Multi-Res) of each word being displayed simultaneously around the fovea. We hypothesized that the Multi-Res setup would lead readers to make fewer detrimental eye movements, and to recognize words faster as a consequence of multiplied orthographic input. We used eye-tracking to simulate a gaze-contingent foveal scotoma in normally-sighted participants, who read words either in classic SVP or in Multi-Res mode. In line with our hypotheses, reading was drastically better in the Multi-Res condition, with faster recognition, fewer saccades and increased oculomotor stability. We surmise that the Multi-Res method has good potential for improving reading in central vision loss, over and above classic SVP techniques.

Longitudinal Changes of Fixation Stability and Location Within 24 Months in Stargardt Disease: ProgStar Report No. 16

PURPOSE

Stargardt disease type 1 (STGD1) is the most common macular dystrophy. The assessment of fixation describes an important dimension of visual function, but data on its progression over time are limited. We present longitudinal changes and investigate its usefulness for clinical trials.

DESIGN

International, multicenter, prospective cohort study.

METHODS

Included were 239 individuals with genetically confirmed STGD1 (one or more disease-causing ATP binding cassette subfamily A member 4 [ABCA4] variant). We determined the fixation stability (FS) using 1 SD of the bivariate contour ellipse area (1 SD-BCEA) and fixation location (FL) using the eccentricity of fixation from the fovea during five study visits every 6 months.

RESULTS

At baseline, 239 patients (105 males [44%]) and 459 eyes, with a median age of 32 years, were included. The baseline mean logBCEA was 0.70 ± 1.41 log deg² and the mean FL was 6.25° ± 4.40°. Although the mean logBCEA did not monotonically increase from visit to visit, the overall yearly increase in the logBCEA was 0.124 log deg² (95% CI, 0.063-0.185 log deg²). The rate of change was not different between the 2 years but increased faster in eyes without flecks outside of the vascular arcades and depended on baseline logBCEA. FL did not change statistically significantly over time.

CONCLUSIONS

Fixation parameters are unlikely to be sensitive outcome measures for clinical trials in STGD1 but may provide useful ancillary information in selected cases to longitudinally describe and understand an eye's visual function.

Exploration of dynamic text presentations in bilateral central vision loss

PURPOSE

Dynamic text presentation methods may improve reading ability in patients with central vision loss (CVL) by eliminating the need for accurate eye movements. We compared rapid serial visual presentation (RSVP) and horizontal scrolling text presentation (scrolling) on reading rate and reading acuity in CVL observers and normally-sighted controls with simulated CVL (simCVL).

METHODS

CVL observers' (n = 11) central scotomas and preferred retinal loci (PRL) for each eye were determined with MAIA microperimetry and fixation analysis. SimCVL controls (n = 16) used 4° inferior eccentric viewing, enforced with an Eyelink eye-tracker. Observers read aloud 4-word phrases randomly drawn from the MNREAD sentences. Six font sizes (0.50-1.30 logMAR) were tested with the better near acuity eye and both eyes of CVL observers. Three font sizes (0.50-1.00 logMAR) were tested binocularly in simCVL controls. Text presentation duration of each word for RSVP or drift speed for scrolling was varied to determine reading rate, defined as 50% of words read correctly. In a subset of CVL observers (n = 7), relationships between PRL eccentricity, reading threshold and rate were explored.

RESULTS

SimCVL controls demonstrated significantly faster reading rates for RSVP than scrolling text (p < 0.0001), and there was a significant main effect of font size (p < 0.0001). CVL patients demonstrated no significant differences in binocular reading rate between font sizes (p = 0.12) and text presentation (p = 0.25). Similar results were seen under monocular conditions. Reading acuity for RSVP and scrolling worsened with increasing PRL eccentricity (μ = 4.5°, p = 0.07). RSVP reading rate decreased significantly with increasing eccentricity (p = 0.02).

CONCLUSIONS

Consistent with previous work, reading acuity worsened with increasing PRL eccentricity. RSVP and scrolling text presentations significantly affected reading rate in simCVL, but not in CVL observers, suggesting that simCVL results may not generalise to pathological CVL.

Association of Reading Performance in Geographic Atrophy Secondary to Age-Related Macular Degeneration With Visual Function and Structural Biomarkers

Importance

As a disabling and frequent disease, geographic atrophy secondary to age-related macular degeneration (AMD) constitutes an important study subject. Emerging clinical trials require suitable end points. The characterization and validation of reading performance as a functional outcome parameter is warranted.

Objective

To prospectively evaluate reading performance in geographic atrophy and to assess its association with established visual function assessments and structural biomarkers.

Design, Setting, and Participants

The noninterventional, prospective natural history Directional Spread in Geographic Atrophy study included patients with geographic atrophy secondary to AMD who were recruited at the University Hospital in Bonn, Germany. Participants were enrolled from June 2013 to June 2016. Analysis began December 2019 and ended January 2021.

Main Outcomes and Measures

Reading acuity and reading speed were assessed using Radner charts. Longitudinal fundus autofluorescence and infrared reflectance images were semiautomatically annotated for geographic atrophy, followed by extraction of shape-descriptive variables. Linear mixed-effects models were applied to investigate the association of those variables with reading performance.

Results

A total of 150 eyes of 85 participants were included in this study (median [IQR] age, 77.9 [72.4-82.1] years; 51 women [60%]; 34 men [40%]). Reading performance was impaired with a median (IQR) monocular reading acuity of 0.9 (0.4-1.3) logarithm of the reading acuity determination and a reading speed of 52.8 (0-123) words per minute. In the multivariable cross-sectional analysis, best-corrected visual acuity, area of geographic atrophy in the central Early Treatment Diabetic Retinopathy Study (ETDRS) subfield, classification of noncenter vs center-involving geographic atrophy, and area of geographic atrophy in the inner-right ETDRS subfield showed strongest associations with reading acuity (cross-validated R2for reading acuity = 0.69). Regarding reading speed, the most relevant variables were best-corrected visual acuity, low-luminance visual acuity, area of geographic atrophy in the central ETDRS subfield, in the inner-right ETDRS subfield, and in the inner-upper ETDRS subfield (R2 for reading speed = 0.67). In the longitudinal analysis, a similar prediction accuracy for reading performance was determined (R2 for reading acuity = 0.73; R2 for reading speed = 0.70). Prediction accuracy did not improve when follow-up time was added as an independent variable. Binocular reading performance did not differ from reading performance in the better-seeing eye.

Conclusions and Relevance

The association of reading acuity and speed with visual functional and structural biomarkers supports the validity of reading performance as a meaningful end point in clinical trials. These findings suggest that measures in clinical and low-vision care for patients with geographic atrophy should focus primarily on the better-seeing eye.

Evaluating Reading Performance in Different Preferred Retinal Loci in Persian-Speaking Patients with Age-Related Macular Degeneration

Purpose:

To evaluate reading performance in different preferred retinal loci (PRLs) using a Persian version of a Minnesota Low Vision Reading (MNREAD) chart in Persian-speaking patients with age-related macular degeneration (AMD).

Methods:

In this cross-sectional study, 35 patients with AMD were assessed. The reading performance was investigated by the MNREAD chart without using low vision aids. The location of PRL was determined monocularly using an MP1 microperimeter (Nidek Technologies, Padua, Italy). The anatomical location of the fovea was determined using optical coherence tomography (OCT). Images were taken with the MP1 microperimeter, and Spectralis HRA-OCT device was processed using graphic software to determine the location of the PRL on the retina.

Results:

Thirty-five patients (51 eyes) with a mean age of 73.8 ± 7.7 years (range, 54–88 years) were assessed. Mean best corrected distance visual acuity (logMAR) was 0.65 ± 0.35 (range, 0.2–1.3). Mean levels of reading acuity (RA) (P = 0.009) and critical print size (CPS) (P = 0.015) were significantly different in different locations of PRL. Average scores of maximum reading speed (MRS) (P = 0.058) and reading accessibility index (ACC) (P = 0.058) were not statistically significant in different locations of PRL. There was a positive correlation between PRL-fovea distance and RA (P < 0.001, r = 0.591) and CPS (P < 0.001, r = 0.614). Significant negative correlations were observed between PRL-fovea distance and MRS (P < 0.001, r = −0.519) and ACC (P < 0.001, r = −0.545).

Conclusions:

This study provides evidence for differences in the reading performance of Persian-speaking patients with AMD in different PRL locations. The average scores of all reading indices obtained in the right-field PRL are lower than those in other areas and are highly correlated with the PRL-fovea distance.

Biofeedback stimulation in the visually impaired: a systematic review of literature

BACKGROUND

It is estimated that approximately 1.3 billion people live with some form of distance or near visual impairment. Numerous studies have been carried out to evaluate the effects of biofeedback (BF) and establish if it could be a useful tool in vision rehabilitation for various eye diseases.

OBJECTIVE

This systematic review aimed: 1) to examine the current evidence of BF efficacy for the rehabilitation of the visually impaired and 2) to describe methodological variations used in previous BF studies to provide recommendations for vision rehabilitation interventions.

METHODS

A systematic review was conducted in the Medline, PubMed, Cochrane Library and Web of Science databases to collect documents published between January 2000 and May 2020. Of the 1,960 studies identified, 43 met the criteria for inclusion. The following information was collected from each study: sample size, control group, any eye disease, apparatus used, frequency and number of sessions of BF, main outcomes of training and whether a follow-up was conducted. The first group included studies published as scientific articles in peer-reviewed journals. The second group included abstracts of studies presented at peer-reviewed conferences. Publications were also grouped according to the eye disease treated.

RESULTS

25 articles and 18 peer-reviewed conference abstracts (PRCAs) were included in this review. BF stimulation is a commonly used technique for the treatment of visual impairment caused by macular disease. Most BF studies evaluate the effect of training on the preferred retinal locus (PRL), particularly with regard to fixation location and stability. Across these studies, participants who received BF intervention improved fixation stability and reading speed. High variability in the number of sessions and the duration of BF training was found. Most studies did not use a control group.

CONCLUSIONS

The findings of this review present evidence for biofeedback treatment in vision rehabilitation, with improved oculomotor abilities. Currently, it is not possible to formulate evidence-based recommendations for a standard training procedure due to the poor quality of existing randomised controlled trials. High-quality studies are needed to develop standard protocols for a range of eye diseases.

How Much Do Clinical and Microperimetric Findings Affect Reading Speed in Low Vision Patients with Age-related Macular Degeneration?

Purpose: To investigate the factors affecting the reading speed of patients with central scotoma due to age-related macular degeneration (AMD).Materials and Methods: We included 63 eyes of 63 patients with AMD who applied to our low vision clinic between August 2018 and September 2019 in this prospective study. We evaluated socio-demographic characteristics, eye examination findings and Minnesota Low Vision Reading Test (MNREAD) results. We used the MAIA microperimeter device to evaluate the properties of the preferred retinal locus for fixation (PRL) of the patients. Evaluations included the assessment of the effects of all parameters on reading speed.Results: The PRL was most commonly in the nasal (31%) and superior (26%) quadrants. Twenty-nine percent of the cases preferred the left visual field. PRL localization had no effect on reading speed, whereas, fixation stability, educational status, presence of foveal absolute scotoma, reading acuity and duration of reading interruption were found to have the most significant effects. Multiple regression analysis showed that reading speed decreased by 67 units in the presence of unstable fixation, by 17 units in the presence of foveal absolute scotoma, by 3 units with every 0.1 increase in logMAR value, and by 1.7 units with every 1-year increase in reading interruption. Additionally, being a university graduate was associated with an increased reading speed (by 18 units)Conclusion: Increased reading performance is one of the factors that can improve quality of life. The factors found to affect the reading speed in the current study may guide the rehabilitation process in low vision patients.

The Effect of Age-Related Macular Degeneration on Components of Face Perception

Purpose

Patients with age-related macular degeneration (AMD) experience difficulty with discriminating between faces. We aimed to use a new clinical test to quantify the impact of AMD on face perception and to determine the specific aspects that are affected.

Methods

The Caledonian face test uses an adaptive procedure to measure face discrimination thresholds: the minimum difference required between faces for reliable discrimination. Discrimination thresholds were measured for full-faces, external features (head-shape and hairline), internal features (nose, mouth, eyes, and eyebrows) and shapes (non-face task). Participants were 20 patients with dry AMD (logMAR VA = 0.14 to 0.62), 20 patients with wet AMD (0.10 to 0.60), and 20 age-matched control subjects (−0.18 to +0.06).

Results

Relative to controls, full-face discrimination thresholds were, on average, 1.76 and 1.73 times poorer in participants with dry and wet AMD, respectively. AMD also reduced sensitivity to face features, but discrimination of the internal, relative to external, features was disproportionately impaired. Both distance VA and contrast sensitivity were significant independent predictors of full-face discrimination thresholds (R² = 0.66). Sensitivity to full-faces declined by a factor of approximately 1.19 per 0.1 logMAR reduction in VA.

Conclusions

Both dry and wet AMD significantly reduce sensitivity to full-faces and their component parts to similar extents. Distance VA and contrast sensitivity are closely associated with face discrimination sensitivity. These results quantify the extent of sensitivity impairment in patients with AMD and predict particular difficulty in everyday tasks that rely on internal feature information, including recognition of familiar faces and facial expressions.

Efficacy of biofeedback rehabilitation based on visual evoked potentials analysis in patients with advanced age-related macular degeneration

Age-related macular degeneration (AMD) is a progressive and degenerative disorder of the macula. In advanced stages, it is characterized by the formation of areas of geographic atrophy or fibrous scars in the central macula, which determines irreversible loss of central vision. These patients can benefit from visual rehabilitation programmes with acoustic “biofeedback” mechanisms that can instruct the patient to move fixation from the central degenerated macular area to an adjacent healthy area, with a reorganization of the primary visual cortex. In this prospective, comparative, non-randomized study we evaluated the efficacy of visual rehabilitation with an innovative acoustic biofeedback training system based on visual evoked potentials (VEP) real-time examination (Retimax Vision Trainer, CSO, Florence), in a series of patients with advanced AMD compared to a control group. Patients undergoing training were subjected to ten consecutive visual training sessions of 10 min each, performed twice a week. Patients in the control group did not receive any training. VEP biofeedback rehabilitation seems to improve visual acuity, reading performances, contrast sensitivity, retinal fixation and sensitivity and quality of life in AMD patients.

Effectiveness of Low Vision Rehabilitation Using Microperimetric Acoustic Biofeedback Training in Patients with Central Scotoma

PURPOSE

To evaluate the efficacy of visual rehabilitation with microperimeter biofeedback in patients with central scotoma.

MATERIALS AND METHODS

35 consecutive patients with central scotoma (17 age-related macular degeneration (AMD), 14 Stargardt disease, and 4 cone dystrophy) were included in the study. Visual acuity, reading performance by Minnesota Low Vision Reading Test (MNREAD), quality of life by 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25), and fixation analysis by MAIA microperimeter were evaluated before and 1 month after training. The rehabilitation program consisted of 10 training sessions of 10 minutes.

RESULTS

The median best-corrected visual acuity (BCVA) was 0.80 logMAR (range 0.3 to 1.3 logMAR). Fifty-nine percent of patients with AMD developed a preferred retinal locus (PRL) nasal to the fovea, and 64% of the patients with Stargardt disease preferred a PRL superior to the fovea. The PRL location in 3 of 4 cone dystrophy patients was nasal to the fovea. The mean PRL distance from the fovea was 7.57 ± 3.61 degrees. Fixation stability improved with P1 values of 22.34 ± 11.81 versus 32.05 ± 18.79 (p = .003) and 95% bivariate contour ellipse area (BCEA) values of 41.6 versus 23.6 (p = .018) before and after training, respectively. There was a significant difference in reading acuity between before and after training (p = 0.008). The overall score and near activities score of NEI VFQ-25 were found to be increased at the end of the rehabilitation (p < 0.001).

CONCLUSION

Rehabilitation with acoustic biofeedback in patients with central scotoma looks like a useful technique for improving fixation stability, reading performance and quality of life.

Saccadic movements assessment in eccentric fixation: A study in patients with Stargardt disease

PURPOSE

To investigate saccadic movements in subjects with eccentric fixation due to a deep central scotoma in Stargardt disease (STGD).

METHODS

We studied 10 patients with STGD and 10 healthy subjects (control group). Saccadic movements of all the 20 subjects were assessed by using the eye tracker technique Tobii Glasses Pro 2. Standard measurements of reading ability (MNREAD charts), visual acuity (ETDRS charts), contrast sensitivity (Pelli-Robson charts), reading contrast threshold and speed (REX charts), retinal sensitivity and stability and localization of the fixation (MP1 fundus perimetry) were obtained in all subjects.

RESULTS

The saccadic movements time was significantly slower in STGD than in healthy subjects (699 ± 193 ms vs 299 ± 40 ms, p < 0.001). When STGD patients moved fixation to the target localized in retinal scotomatous areas, the movement was significantly slower compared to non scotomatous areas in the retina (1103 ± 798 ms vs 524 ± 187 ms, p = 0.039). There was a trend toward a correlation between slow saccadic movements in STGD subjects and the reading performance indices, although statistical significance was not achieved.

CONCLUSION

Ocular saccades guided by eccentric fixation in STGD patients are significantly slower than in the control group, especially when the target corresponds to retinal areas with a deep scotoma. These results can explain the worse reading performance in STGD subjects, in particular when a non-viewing area on the right part of the text is present.

Location and stability of the preferred retinal locus in native Persian-speaking patients with age-related macular degeneration

CLINICAL RELEVANCE

The findings of this study can be used in the selection of the preferred retinal locus to establish better rehabilitation services such as eccentric viewing training for patients with age-related macular degeneration.

BACKGROUND

The aim of this study was to determine the characteristics of the preferred retinal locus in native Persian-speaking patients with age-related macular degeneration.

METHODS

In this non-interventional case series, all patients with a diagnosis of age-related macular degeneration referred to the Retina Clinic of the Rassoul Akram Hospital, Tehran, Iran, were evaluated. The fixation characteristics were evaluated monocularly using the MP1 microperimeter (Nidek Technologies, Padua, Italy). Optical coherence tomography was used to determine the location of the central fovea. The images were overlaid and the preferred retinal locus-fovea distance was measured using Image J software.

RESULTS

Fifty-one eyes of 35 patients with a mean age of 73.8 ± 7.7-years were evaluated in this study. Inferior-field, left-field, central-field, right-field, and superior-field preferred retinal locus were detected in 49 per cent, 33.3 per cent, 7.8 per cent, 5.9 per cent, and 3.9 per cent of the subjects, respectively. Fixation was stable in 70.6 per cent, relatively unstable in 15.7 per cent, and unstable in 13.7 per cent of the participants. Significant differences were not found in the mean values of logMAR visual acuity between different fields of the preferred retinal locus after Bonferroni correction (p = 0.031). Analysis of co-variance showed no significant difference in mean sensitivity values between different locations of the preferred retinal locus (p = 0.07). The mean preferred retinal locus-fovea distance was not significantly different between different fields of the preferred retinal locus (p = 0.063).

CONCLUSIONS

Native Persian-speaking patients with central scotoma secondary to age-related macular degeneration place their self-selected preferred retinal locus most frequently in the inferior and left visual field, which would result in scotoma displacement to the superior and right visual field. Fixation stability was statistically similar in different locations of preferred retinal locus, but it improved with decreasing the preferred retinal locus-fovea distance.

Low-Intensity Laser Light Projection for Improved Reading Abilities in Low-Vision Patients

PURPOSE

To evaluate the efficacy of a new laser imaging device that projects images onto functioning macular areas, to improve visual acuity (VA) in low-vision patients with macular diseases.

METHODS

An interventional case series of consecutive patients with low vision in their right eyes (RE). RE VA was measured by showing the patients digits of various standard sizes and measuring their best-corrected VA (BCVA). Then, using the I.C.INSIDE device to project the same standard digits onto functioning macular areas. Patient's ability to recognize the digits with the I.C.INSIDE device was correlated with patient's performance using telescopic low-vision aids. The main outcome measure was change in VA with the different visual aids.

RESULTS

Eleven patients (6 males and 5 females) with an average age of 75 ± 6.7 years and low vision in their RE due to macular diseases were included in the study. Baseline BCVA was 1.554 ± 0.50 logMAR. Low-vision aids improved mean VA in 10 patients to 0.64 ± 0.40 logMAR (p < .0001), further improvement was noticed in 8 patients to 0.35 ± 0.16 logMAR (p < .0001) using the laser device, but, three patients did not recognize any digit using the laser device.

CONCLUSIONS

The I.C.INSIDE device significantly improved baseline VA in low-vision patients with macular diseases, using extra-foveal fixation.

Biofeedback Low Vision Rehabilitation with Retimax Vision Trainer in Patients with Advanced Age-related Macular Degeneration: A Pilot Study

PURPOSE

To evaluate the effectiveness of Visual Evoked Potential (VEP) biofeedback rehabilitation in selected low vision patients with advanced age-related macular degeneration (AMD).

DESIGN

Retrospective observational cohort study.

METHODS

Patients affected by advanced AMD, central macular atrophy with unstable fixation and best corrected visual acuity (BCVA) between 20/100 and 20/320 were considered. Selected patients underwent fundus photography and microperimetry with fixation analysis for the selected eye (highest BCVA). Ten consecutive training sessions of 10 min each were performed twice a week in the selected eye with Retimax Vision Trainer (CSO, Florence). BCVA, reading acuity and reading speed, contrast sensitivity, fixation, retinal sensitivity and quality of life questionnaire (VFQ-25) were evaluated at baseline and 7 days following the final session.

RESULTS

Significant improvements in terms of BCVA [p = .011], reading speed [p = .007], VFQ-25 score [p = .007], retinal sensitivity [p = .021] and fixation stability in the central 2° and 4° [p = .048; p = .037] post-treatment were observed for the 9 patients enrolled, with insignificant improvements observed in reading acuity and contrast sensitivity [p = .335; p = .291].

CONCLUSIONS

Preliminary results support VEP biofeedback rehabilitation improvements for visual function and quality of life in advanced AMD patients with low vision.

The Effect of Simulated Central Field Loss on Street-crossing Decision-Making in Young Adult Pedestrians

SIGNIFICANCE

This study explored the street-crossing decision-making performance of young normally sighted subjects with simulated central field loss (CFL). The results suggest that using eccentric viewing enables a person to make safe and reliable street-crossing decisions.

PURPOSE

This study tested the hypothesis that, as the diameter of an experimentally induced central scotoma increases, the accuracy and reliability of street-crossing decisions worsen.

METHODS

Street-crossing decisions were measured in 20 young subjects aged between 23 and 31 years while monocularly viewing a nonsignalized, one-way street for different vehicular arrival times. Using a 5-point rating scale, subjects judged whether they could cross the street before vehicular arrival with habitual vision and simulated CFL with eccentric viewing. The CFL was induced using soft contact lenses with different central opaque diameters. Using receiver operating characteristic curve analysis, we obtained subjects' accuracy (amount of time in seconds where subjects either overestimated or underestimated vehicular arrival time relative to their actual crossing time) and reliability (how quickly subjects transitioned from judging insufficient to sufficient time to cross relative to their actual crossing time).

RESULTS

The centrally opaque contact lenses induced central scotomata with a mean (standard deviation) diameter of 17.12° (5.83°). No significant difference in street-crossing accuracy (P = .35) or reliability (P = .09) was found between the normal, habitual vision and simulated CFL conditions. No statistically significant correlations were found between scotoma diameter and the accuracy and reliability of subjects' street-crossing decisions (P = .83 and P = .95, respectively).

CONCLUSIONS

The findings of this study suggest that adopting eccentric viewing enables a person to successfully mitigate the negative effects of an absolute central scotoma on the accuracy and reliability of their street-crossing decisions.

THE OASIS MP-1 SUBSTUDY: Characterization of the Effect of Ocriplasmin on Microperimetry Parameters

The MP-1 substudy of the OASIS trial evaluated the effects of ocriplasmin and symptomatic VMA resolution on visual fixation and macular sensitivity using microperimetry, identifying parameters that were distinct between patients with and without VMA resolution.

Purpose:

To evaluate the effects of ocriplasmin and symptomatic vitreomacular adhesion resolution on visual fixation and macular sensitivity using microperimetry.

Methods:

MP-1 parameters were analyzed from 3 OASIS sites after the use of standardized instruments and testing procedures over 24 months.

Results:

A total of 27 patients (19 ocriplasmin, 8 sham) were evaluated. Mean distance of the preferred fixation locus to the anatomical center was farther in the sham group at baseline and farther in the sham versus ocriplasmin group throughout the study. Retinal sensitivity values were consistently higher in the ocriplasmin versus sham group after Month 3. Fewer patients in the ocriplasmin group had predominantly eccentric fixation at study end compared with the sham group, which also had an increased number of patients with unstable fixation. Patients with vitreomacular adhesion resolution had lower bivariate contour area, fewer relative scotomas, and higher retinal sensitivity parameters at baseline than those with unresolved vitreomacular adhesion.

Conclusion:

Substudy results suggest that fixation and sensitivity parameters tended to be better in the ocriplasmin group than in the sham group over time. The substudy identified parameters that were distinct between patients with and without vitreomacular adhesion resolution, suggesting that microperimetry warrants further study as a relevant biomarker for visual function.

Temporal modulation improves dynamic peripheral acuity

Macular degeneration and related visual disorders greatly limit foveal function, resulting in reliance on the peripheral retina for tasks requiring fine spatial vision. Here we investigate stimulus manipulations intended to maximize peripheral acuity for dynamic targets. Acuity was measured using a single interval orientation discrimination task at 10° eccentricity. Two types of image motion were investigated along with two different forms of temporal manipulation. Smooth object motion was generated by translating targets along an isoeccentric path at a constant speed (0-20°/s). Ocular motion was simulated by jittering target location using previously recorded fixational eye movement data, amplified by a variable gain factor (0-8). In one stimulus manipulation, the sequence was temporally subsampled by displaying the target on an evenly spaced subset of video frames. In the other, the contrast polarity of the stimulus was reversed at a variable rate. We found that threshold under object motion was improved at all speeds by reversing contrast polarity, while temporal subsampling improved resolution at high speeds but impaired performance at low speeds. With simulated ocular motion, thresholds were consistently improved by contrast polarity reversal, but impaired by temporal subsampling. We find that contrast polarity reversal and temporal subsampling produce differential effects on peripheral acuity. Applying contrast polarity reversal may offer a relatively simple image manipulation that could enhance visual performance in individuals with central vision loss.

The Sound of Scotoma: Audio Space Representation Reorganization in Individuals With Macular Degeneration

Blindness is an ideal condition to study the role of visual input on the development of spatial representation, as studies have shown how audio space representation reorganizes in blindness. However, how spatial reorganization works is still unclear. A limitation of the study on blindness is that it is a "stable" system and it does not allow for studying the mechanisms that subtend the progress of this reorganization. To overcome this problem here we study, for the first time, audio spatial reorganization in 18 adults with macular degeneration (MD) for which the loss of vision due to scotoma is an ongoing progressive process. Our results show that the loss of vision produces immediate changes in the processing of spatial audio signals. In individuals with MD, the lateral sounds are "attracted" toward the central scotoma position resulting in a strong bias in the spatial auditory percept. This result suggests that the reorganization of audio space representation is a fast and plastic process occurring also later in life, after vision loss.

Contextual influences in the peripheral retina of patients with macular degeneration

Macular degeneration (MD) is the leading cause of low vision in the elderly population worldwide. In case of complete bilateral loss of central vision, MD patients start to show a preferred retinal region for fixation (PRL). Previous literature has reported functional changes that are connected with the emergence of the PRL. In this paper, we question whether the PRL undergoes a use-dependent cortical reorganization that alters the range of spatial lateral interactions between low-level filters. We asked whether there is a modulation of the excitatory/inhibitory lateral interactions or whether contextual influences are well accounted for by the same law that describes the integration response in normal viewers. In a group of 13 MD patients and 7 age-matched controls, we probed contextual influences by measuring the contrast threshold for a vertical target Gabor, flanked by two collinear high-contrast Gabors. Contextual influences of the collinear flankers were indicated by the changes in contrast threshold obtained at different target-to-flanker distances (λs) relative to the baseline orthogonal condition. Results showed that MDs had higher thresholds in the baseline condition and functional impairment in the identification tasks. Moreover, at the shortest λ, we found facilitatory rather than inhibitory contextual influence. No difference was found between the PRL and a symmetrical retinal position (non-PRL). By pulling together data from MD and controls we showed that in the periphery this inversion occurs when the target threshold approach the flankers’ contrast (about 1:3 ratio) and that for patients it does occur in both the PRL and a symmetrical retinal position (non-PRL). We conclude that contrary to previous interpretations, this modulation doesn’t seem to reflect use-dependent cortical reorganization but rather, it might result from a reduction of contrast gain for the target that promotes target-flankers grouping.

Fixation behavior in macular dystrophy assessed by microperimetry

Purpose

To investigate the fixation behavior in macular dystrophy using microperimetry.

Methods

This retrospective study included patients with macular dystrophy and unilateral macular pucker. Macular dystrophic eyes were compared based on fixation within or outside of the atrophic region. The normal fellow eyes in patients with unilateral macular pucker formed the control group. Clinical and demographic characteristics of age, sex, best-corrected visual acuity, spherical equivalent, and fixation behavior (which included foveal mean sensitivity (MS), fixation MS, MS improvement, stability, centrality, and eccentric distance of fixation) were analyzed. A total of 58 patients were recruited, comprising 29 eyes of 29 patients in the macular dystrophy group and 29 eyes of 29 patients in the control group.

Results

Compared to the control group, patients with macular dystrophy had significantly poorer visual acuity, foveal MS, fixation MS, stability, and centrality, and more eccentric preferred retinal locations (PRLs). In macular dystrophy, the PRLs were most common on the superior side (48.3%). Compared to fixation in the atrophic region, PRLs out of the atrophic lesion gained more MS (7.41 vs. 0.89 dB, p = 0.001), although with less stable fixation (10.0 vs. 47.4%, p = 0.044). By multivariate linear regression, eccentric distance was found to be significantly associated with MS improvement (p = 0.023).

Conclusions

The commonest location of PRLs in macular dystrophy is anatomically superior to the lesion. The dystrophic eye can gain better sensitivity by using PRLs outside the atrophic area.

Simulation of a central scotoma using contact lenses with an opaque centre

PURPOSE

This study evaluated the feasibility of using soft contact lenses (CLs) with an opaque centre to induce absolute central scotomas that move with the eye. We examined the geometrical optics prediction that scotoma size will vary with the size of the CL's opaque centre and with ocular pupil size. We also tested the hypothesis that high environmental light levels will ensure that the ocular pupil will remain small enough, even with opaque centre CLs, to generate absolute scotomas representative of those experienced by patients with age-related macular disease.

METHODS

Using an Octopus 900 Perimeter ( www.Haag-Streit.com), kinetic visual fields (VFs) were measured in five normally-sighted subjects using a V4e Goldmann target with CLs that had central opaque areas with diameters of 2.8, 3.0, and 3.2 mm. To control pupil size, VFs were measured with background perimeter bowl luminances of 10, 585, and 1155 cd m^-2 . Subjects attempted to (i) fixate the bowl centre; and (ii) place the scotoma edge at the bowl fixation target (eccentric viewing).

RESULTS

As predicted, there was a direct relationship between scotoma size and both luminance level and diameter of the opacity. Mean scotoma diameters were 0°, 17.6° and 22°, for the low, medium and high bowl luminances, respectively. Scotoma size was determined primarily by the difference between the diameters of CL opacity and the entrance pupil of the eye and the axial separation between them, and between-subject differences in pupil diameters contributed most to the between-subject variability in scotoma diameter at each light level (SD: 6.01°). Scotoma displacement during eccentric fixation confirmed the gaze-contingent characteristics of this experimental model.

CONCLUSION

It is possible to induce a gaze-contingent absolute scotoma and hence mimic central vision loss using centrally-opaque CLs provided that the CL opacity is larger than the entrance pupil of the eye. This simulation tool will, therefore, be ineffective at low environmental light levels (as shown previously) if the entrance pupil of the eye is larger than the CL opacity.

Morphologic and Postoperative Fixation Characteristics of the Macular Epiretinal Membrane in Young Patients Undergoing Surgery

BACKGROUND AND OBJECTIVE

To describe morphologic characteristics, surgical outcomes, postoperative preferred retinal loci (PRL), and fixation stability of epiretinal membranes (ERMs) in young patients.

PATIENTS AND METHODS

This retrospective study analyzed 43 eyes of 41 young patients (age range: 0.8 years to 28 years) with ERMs, which were divided into two groups: secondary ERMs (SERMs; n = 28) and idiopathic ERMs (IERMs; n = 13). All 43 eyes underwent 25-gauge vitrectomy and membrane peeling. Spectral-domain optical coherence tomography scans and microperimetry were used to analyze morphologic and fixation characteristics, respectively.

RESULTS

Premacular fibrosis was more common in SERMs group (P = .006). SERMs were also associated with less external limiting membrane (ELM) (P = .008) and ellipsoid zone visibility (P = .008) compared with IERMs. Best-corrected visual acuity (BCVA) improved in 20 eyes (69%) with SERMs (P = .005) and in 12 eyes (86%) with IERMs (P = .13). From the analysis of the postoperative fixation characteristics, there was a linear correlation between visual acuity and fixation stability (R² = 0.495).

CONCLUSION

BCVA improved significantly in young patients with ERM, even in cases with a severely disrupted ELM and ellipsoid zone. More attention should be paid to the postoperative fixation location and stability. [Ophthalmic Surg Lasers Imaging Retina. 2017;48:655-662.].

The Pattern of Visual Fixation Eccentricity and Instability in Optic Neuropathy and Its Spatial Relationship to Retinal Ganglion Cell Layer Thickness

Purpose

The purpose of this study was to assess whether clinically useful measures of fixation instability and eccentricity can be derived from retinal tracking data obtained during optical coherence tomography (OCT) in patients with optic neuropathy (ON) and to develop a method for relating fixation to the retinal ganglion cell complex (GCC) thickness.

Methods

Twenty-nine patients with ON underwent macular volume OCT with 30 seconds of confocal scanning laser ophthalmoscope (cSLO)-based eye tracking during fixation. Kernel density estimation quantified fixation instability and fixation eccentricity from the distribution of fixation points on the retina. Preferred ganglion cell layer loci (PGCL) and their relationship to the GCC thickness map were derived, accounting for radial displacement of retinal ganglion cell soma from their corresponding cones.

Results

Fixation instability was increased in ON eyes (0.21 deg²) compared with normal eyes (0.06982 deg²; P < 0.001), and fixation eccentricity was increased in ON eyes (0.48°) compared with normal eyes (0.24°; P = 0.03). Fixation instability and eccentricity each correlated moderately with logMAR acuity and were highly predictive of central visual field loss. Twenty-six of 35 ON eyes had PGCL skewed toward local maxima of the GCC thickness map. Patients with bilateral dense central scotomas had PGCL in homonymous retinal locations with respect to the fovea.

Conclusions

Fixation instability and eccentricity measures obtained during cSLO-OCT assess the function of perifoveal retinal elements and predict central visual field loss in patients with ON. A model relating fixation to the GCC thickness map offers a method to assess the structure–function relationship between fixation and areas of preserved GCC in patients with ON.

Multimodal analysis of the Preferred Retinal Location and the Transition Zone in patients with Stargardt Disease

PURPOSE

The purpose of our study was to investigate morpho-functional features of the preferred retinal location (PRL) and the transition zone (TZ) in a series of patients with recessive Stargardt disease (STGD1).

METHODS

Fifty-two STGD1 patients with at least one ABCA4 mutation, atrophy of the central macula (MA) and an eccentric PRL were recruited for the study. Microperimetry, fundus autofluorescence (FAF), spectral-domain optical coherence tomography (SD-OCT) were performed. The location and stability of the PRL along with the associated FAF pattern and visual sensitivities were determined and compared to the underlying retinal structure.

RESULTS

The mean visual sensitivity of the PRLs for the 52 eyes was 10.76 +/- 3.70 dB. For the majority of eyes, PRLs were associated with intact ellipsoid zone (EZ) bands and qualitatively normal FAF patterns. In 17 eyes (32.7%) the eccentric PRL was located at the edge of the MA. In 35 eyes (67.3%) it was located at varying distances from the border of the MA with a TZ between the PRL and the MA. The TZ was associated with decreased sensitivity values (5.92 +/- 4.69 dB) compared to PRLs (p<0.05), with absence/disruption of the EZ band and abnormal FAF patterns (hyper or hypo-autofluorescence).

CONCLUSIONS

In STGD1 eccentric PRLs are located away from the border of MA and associated with intact EZ bands and normal FAF. The TZ is characterized by structural and functional abnormalities. The results of multimodal imaging of the PRL and TZ suggest a possible sequence of retinal and functional changes with disease progression that may help in the planning of future therapies; RPE dysfunction appears to be the primary event leading to photoreceptor degeneration and then to RPE loss.

Peripheral oculomotor training in individuals with healthy visual systems: Effects of training and training transfer

Individuals with pathological or simulated central visual field loss can be trained to use a preferred retinal locus (PRL) as a substitute for their non-functioning fovea. The functional benefits of a stable PRL are well documented, but little is known about oculomotor adaptations during PRL acquisition or transfer of training to another location in response to real or simulated disease progression. In this study, eight normally-sighted observers were trained to use a pseudo-PRL (pPRL) at one of two locations by guiding an eccentrically placed, gaze-contingent ring over a fixation target. The pPRL location was 6.4 degrees in either inferior or right visual field, balanced across observers. Training was completed in two sessions of 200 hundred trials separated by a week. Between sessions, the pPRL position was switched. Task performance was quantified both in terms of gaze stability around the fixation target and gaze accuracy in terms of distance between the target and ring centers. The latter was used to provide feedback by covarying the diameter of the ring to make the task easier or harder on the basis of subject performance. Accuracy and stability significantly increased with training and was comparable at each trained location. Performance gains were retained over a week and transferred from the first to the second pPRL location. Thus, pPRL training with feedback can provide sustained, generalizable improvements in oculomotor control following simulated foveal vision loss. These results suggest that low vision rehabilitation specialists may prioritize PRL training locations based on sensory function alone, since oculomotor gains are relatively uniform; and that training early in the disease process may benefit later adaptations should eye disease progress.

Microperimetry biofeedback training in a patient with bilateral myopic macular degeneration with central scotoma

Microperimetry-1 (MP-1) evaluation and MP-1 biofeedback training were done in a case of bilateral myopic macular degeneration with a central scotoma. Fixation behavior, location and stability of preferred retinal locus, eye movement speed, and mean sensitivity were assessed. The mean retinal sensitivities before, after and at 1-year after training in the right eye were 2.9 dB, 2.9 dB and 3.7 dB and in the left eye were 3.5 dB, 3.7 dB and 1.8 dB. The fixation point in the 2° gravitation circle, improved from 40% to 50% in the right eye and from 43% to 67% in the left eye. The average eye speed before, after and at 1-year after training in right eye were 0.19°/s, 0.26°/s and 0.25°/s and in left eye were 0.36°/s, 0.25°/s and 0.27°/s. Thus, biofeedback training using MP-1 can improve the visual function in patients with macular diseases and central scotoma.

MULTIMODAL IMAGING FINDINGS AND MULTIMODAL VISION TESTING IN NEOVASCULAR AGE-RELATED MACULAR DEGENERATION

PURPOSE

To investigate the interactions among multimodal imaging findings and multimodal vision testing in neovascular age-related macular degeneration.

METHODS

Patients enrolled in a prospective study of neovascular age-related macular degeneration with at least 3 previous intravitreal anti-vascular endothelial growth factor injections. Each patient underwent multimodal fundus imaging including spectral domain optical coherence tomography and fundus autofluorescence, and multimodal vision testing, including visual acuity, contrast sensitivity, reading speed, and microperimetry.

RESULTS

There were 73 eyes of 49 consecutive patients enrolled. Generalized estimating equations' modelling showed that the significant independent predictors of visual acuity were the area of confluent hypoautofluorescence and involvement of the foveal center with either granular or confluent hypoautofluorescence (P < 0.001). Contrast sensitivity was negatively correlated with the area of confluent hypoautofluorescence (P < 0.001), involvement of the foveal center with granular hypoautofluorescence (P = 0.017), and subfoveal choroidal thickness (P = 0.042). The only significant predictor of reading speed was the size of confluent hypoautofluorescence (P < 0.001). The size of the defect in the ellipsoid zone (P < 0.001) and the presence of intraretinal fluid (P = 0.045) were correlated with microperimetry score.

CONCLUSION

Confluent absence of autofluorescence was a highly significant predictor of vision testing and serves as an easy parameter to obtain in patients with neovascular age-related macular degeneration.

Comparing the fixational and functional preferred retinal location in a pointing task

Patients with central vision loss (CVL) typically adopt eccentric viewing strategies using a preferred retinal locus (PRL) in peripheral retina. Clinically, the PRL is defined monocularly as the area of peripheral retina used to fixate small stimuli. It is not clear if this fixational PRL describes the same portion of peripheral retina used during dynamic binocular eye-hand coordination tasks. We studied this question with four participants each with a unique CVL history. Using a scanning laser ophthalmoscope, we measured participants' monocular visual fields and the location and stability of their fixational PRLs. Participants' monocular and binocular visual fields were also evaluated using a computer monitor and eye tracker. Lastly, eye-hand coordination was tested over several trials where participants pointed to and touched a small target on a touchscreen monitor. Trials were blocked and carried out monocularly and binocularly, with a target appearing at 5° or 15° from screen center, in one of 8 locations. During pointing, our participants often exhibited long movement durations, an increased number of eye movements and impaired accuracy, especially in monocular conditions. However, these compensatory changes in behavior did not consistently worsen when loci beyond the fixational PRL were used. While fixational PRL size, location and fixation stability provide a necessary description of behavior, they are not sufficient to capture the pointing PRL used in this task. Generally, patients use a larger portion of peripheral retina than one might expect from measures of the fixational PRL alone, when pointing to a salient target without time constraints. While the fixational and pointing PRLs often overlap, the fixational PRL does not predict the large area of peripheral retina that can be used.

A new perspective on how humans assess their surroundings; derivation of head orientation and its role in 'framing' the environment

Understanding the way humans inform themselves about their environment is pivotal in helping explain our susceptibility to stimuli and how this modulates behaviour and movement patterns. We present a new device, the Human Interfaced Personal Observation Platform (HIPOP), which is a head-mounted (typically on a hat) unit that logs magnetometry and accelerometry data at high rates and, following appropriate calibration, can be used to determine the heading and pitch of the wearer’s head. We used this device on participants visiting a botanical garden and noted that although head pitch ranged between −80° and 60°, 25% confidence limits were restricted to an arc of about 25° with a tendency for the head to be pitched down (mean head pitch ranged between −43° and 0°). Mean rates of change of head pitch varied between −0.00187°/0.1 s and 0.00187°/0.1 s, markedly slower than rates of change of head heading which varied between −0.3141°/0.1 s and 0.01263°/0.1 s although frequency distributions of both parameters showed them to be symmetrical and monomodal. Overall, there was considerable variation in both head pitch and head heading, which highlighted the role that head orientation might play in exposing people to certain features of the environment. Thus, when used in tandem with accurate position-determining systems, the HIPOP can be used to determine how the head is orientated relative to gravity and geographic North and in relation to geographic position, presenting data on how the environment is being ‘framed’ by people in relation to environmental content.

Reliability and Intersession Agreement of Microperimetric and Fixation Measurements Obtained with a New Microperimeter in Normal Eyes

PURPOSE

To evaluate the reliability and intersession agreement of measurements of retinal sensitivity as well as of the fixation pattern obtained in healthy eyes with a microperimeter integrating the mechanism of the scanning laser ophthalmoscope (SLO) with the static perimetry.

METHODS

This study included a sample of 44 healthy eyes of 44 subjects of a mean age of 27.0 ± 8.5 years. In all cases, microperimetric exams with the MAIA system (Centervue, Padova, Italy) were performed in three different sessions to evaluate the intersession repeatability. The consistency of measurements was analyzed by using the Friedman test and by analyzing the correlation between consecutive measurements. Agreement between the first and third sessions was assessed by using the Passing-Bablok regression analysis. The following parameters were analyzed: average threshold (AT), macular integrity (MI) index, fixation indexes P1 and P2, bivariate contour ellipse area (BCEA), major and minor axes of the ellipse and high preferred retinal locus position (PRLh).

RESULTS

Not statistically significant differences were found in the evaluated parameters between the three sessions (p ≥ 0.193). The correlation between consecutive measurements was moderate to strong for all parameters evaluated (r ≥ 0.49, p < 0.01), except for the MI and the position of the PRLh (r ≤ 0.305, p ≥ 0.05). The Passing-Bablok regression analysis showed a good agreement between the first and third measurement for all parameters, except for the MI and the position of the PRLh.

CONCLUSION

MAIA MP system is able to provide consistent measurements of AT and fixation in normal subjects. MI and the position of PRLh seem to be the least reliable parameters in this group of patients.

Space representation in age-related macular degeneration

PURPOSE

To investigate the effect of age-related macular degeneration (AMD) on memory for spatial representations in realistic environments.

METHODS

Participants were 19 patients with AMD and 13 age-matched observers. In a short-term spatial memory task, observers were first presented with one view of a scene (the prime view), and their task was to change the viewpoint forward or backward to match the prime view. Memory performance was measured as the number of snapshots between the selected view and the prime view.

RESULTS

When selecting a match to the prime view, both people with AMD and those in the control group showed systematic biases toward the middle view of the range of snapshots. People with AMD exhibited a stronger middle bias after presentation of close and far prime views while navigating accurately after a middle prime view. No relation was found between visual acuity, visual field defect, or lesion size and the memory performance.

CONCLUSIONS

Memory tasks using indoor scenes can be accomplished when central vision is impoverished, as with AMD. Stronger center bias for a scene location suggests that people with AMD rely more on their memory of a canonical view.

Applying theories and interventions from behavioral medicine to understand and reduce visual field variability in patients with vision loss

Visual field (VF) test results are often unreliable in visually impaired patients, but continue to be a cornerstone of clinical trials and play a vital role in clinical decision making since they are the primary method to determine patients' functional vision loss or progression. Currently, patients are typically asked to perform VF tasks with minimal instruction or consideration of their psychological experience during the test. The gradual loss of vision due to retinal diseases, such as retinitis pigmentosa (RP), age-related macular degeneration (AMD), or glaucoma can contribute to the experience of negative psychosocial states, such as anxiety, stress, and depression, as well as diminished quality of life. We hypothesize that VF testing elicits test performance anxiety and perception of functional losses of vision, which induces distracting negative thoughts that result in increased VF test variability. Resources for processing and responding to vision-related information may be diverted from task-relevant VF stimuli to task-irrelevant ones, such as internal worry and test anxiety, thereby resulting in VF test performance decrements. We present a theoretical model to support the hypothesis that VF variability is linked to patients' negative thoughts during VF testing. This conceptual framework provides a basis for the development of coping strategies and mindfulness-based interventions to be evaluated in future research aimed at improving psychosocial states and VF reliability in visually-impaired patients. It would be highly significant to intervene by modifying negative thoughts during VF testing to reduce test variability in glaucoma patients who are progressively losing vision to a blinding eye disease, but whose vision loss has not been accurately identified and treated early enough due to variable VF results. In clinical trials of potential interventions for RP and non-neovascular AMD, reducing VF variability would effectively increase the precision for detecting treatment effects and allow a reduction in the number of VF tests needed to estimate the treatment responses, thus reducing burden on investigators and patients, as well as saving time and money.

Biofeedback stimulation in patients with age-related macular degeneration: comparison between 2 different methods

OBJECTIVE

To evaluate changes in patient's visual performance after rehabilitation training with 2 different biofeedback training programs offered by the MP-1 microperimeter. Spontaneous retinal location of preferred retinal loci (PRLs) and fixation stability are not always optimal for best visual performances. MP-1 microperimeter biofeedback techniques have been suggested as modalities for training for better fixation stability and to find a better location of the new PRL in a more useful area of the retina in nonoptimal cases. The MP-1 microperimeter offers different biofeedback strategies, such as acoustic biofeedback and structured light stimulus plus acoustic biofeedback.

DESIGN

Retrospective study.

PARTICIPANTS

Thirty subjects affected by age-related macular degeneration with absolute central scotoma.

METHODS

A standard protocol of examination before and after visual rehabilitation training was performed on all study subjects. Assessment included demographics data, visual acuity, fixation stability, retinal sensitivity, and reading speed. Rehabilitation training was performed with standard and structured stimulus biofeedback. The whole sample was divided into 2 groups of 15 patients attending the 2 different stimulation training biofeedback.

RESULTS

Mean reading speed was found to be significantly increased for both groups (p < 0.05 and p < 0.01). Also, a statistically significant improvement of fixation stability was registered for both groups (p < 0.01). Only patients trained with the flickering pattern biofeedback stimulation increased retinal sensitivity (p < 0.01).

CONCLUSIONS

Both regular biofeedback and flickering pattern biofeedback training seem to improve visual functions. More benefits seem to be accrued, however, with flickering pattern biofeedback training.

The Glenn A. Fry Award Lecture 2012: Plasticity of the visual system following central vision loss

Following the onset of central vision loss, most patients develop an eccentric retinal location outside the affected macular region, the preferred retinal locus (PRL), as their new reference for visual tasks. The first goal of this article is to present behavioral evidence showing the presence of experience-dependent plasticity in people with central vision loss. The evidence includes the presence of oculomotor re-referencing of fixational saccades to the PRL; the characteristics of the shape of the crowding zone (spatial region within which the presence of other objects affects the recognition of a target) at the PRL are more "foveal-like" instead of resembling those of the normal periphery; and the change in the shape of the crowding zone at a para-PRL location that includes a component referenced to the PRL. These findings suggest that there is a shift in the referencing locus of the oculomotor and the sensory visual system from the fovea to the PRL for people with central vision loss, implying that the visual system for these individuals is still plastic and can be modified through experiences. The second goal of the article is to demonstrate the feasibility of applying perceptual learning, which capitalizes on the presence of plasticity, as a tool to improve functional vision for people with central vision loss. Our finding that visual function could improve with perceptual learning presents an exciting possibility for the development of an alternative rehabilitative strategy for people with central vision loss.

Characterization of field loss based on microperimetry is predictive of face recognition difficulties

PURPOSE

To determine how visual field loss as assessed by microperimetry is correlated with deficits in face recognition.

METHODS

Twelve patients (age range, 26-70 years) with impaired visual sensitivity in the central visual field caused by a variety of pathologies and 12 normally sighted controls (control subject [CS] group; age range, 20-68 years) performed a face recognition task for blurred and unblurred faces. For patients, we assessed central visual field loss using microperimetry, fixation stability, Pelli-Robson contrast sensitivity, and letter acuity.

RESULTS

Patients were divided into two groups by microperimetry: a low vision (LV) group (n = 8) had impaired sensitivity at the anatomical fovea and/or poor fixation stability, whereas a low vision that excluded the fovea (LV:F) group (n = 4) was characterized by at least some residual foveal sensitivity but insensitivity in other retinal regions. The LV group performed worse than the other groups at all blur levels, whereas the performance of the LV:F group was not credibly different from that of the CS group. The performance of the CS and LV:F groups deteriorated as blur increased, whereas the LV group showed consistently poor performance regardless of blur. Visual acuity and fixation stability were correlated with face recognition performance.

CONCLUSIONS

Persons diagnosed as having disease affecting the central visual field can recognize faces as well as persons with no visual disease provided that they have residual sensitivity in the anatomical fovea and show stable fixation patterns. Performance in this task is limited by the upper resolution of nonfoveal vision or image blur, whichever is worse.

Rapid and persistent adaptability of human oculomotor control in response to simulated central vision loss

The central region of the human retina, the fovea, provides high-acuity vision. The oculomotor system continually brings targets of interest into the fovea via ballistic eye movements (saccades). Thus, the fovea serves both as the locus for fixations and as the oculomotor reference for saccades. This highly automated process of foveation is functionally critical to vision and is observed from infancy. How would the oculomotor system adjust to a loss of foveal vision (central scotoma)? Clinical observations of patients with central vision loss suggest a lengthy adjustment period, but the nature and dynamics of this adjustment remain unclear. Here, we demonstrate that the oculomotor system can spontaneously and rapidly adopt a peripheral locus for fixation and can rereference saccades to this locus in normally sighted individuals whose central vision is blocked by an artificial scotoma. Once developed, the fixation locus is retained over weeks in the absence of the simulated scotoma. Our data reveal a basic guiding principle of the oculomotor system that prefers control simplicity over optimality. We demonstrate the importance of a visible scotoma on the speed of the adjustment and suggest a possible rehabilitation regimen for patients with central vision loss.