Visual function and biofeedback training of patients with central vision loss: a review.

Older individuals with macular diseases, such as age-related macular degeneration, experience central vision loss (CVL) due to degeneration of their photoreceptors and retinal cells. Patients with CVL may experience various vision impairments, including of visual acuity, fixation stability, contrast sensitivity, and stereoacuity. After CVL, most patients develop a preferred retinal locus outside the affected macular region, which serves as a new visual reference. In this review, we provide an overview of the visual function and impairment in individuals with CVL. In addition, the important role of biofeedback training on the visual function and activity of individuals with CVL is also reviewed. Accordingly, the location and development of the preferred retinal loci are discussed. Finally, this review discusses how to conduct biofeedback training to treat individuals with CVL.

What Is a Preferred Retinal Locus?

This review examines the concept of the preferred retinal locus (PRL) in patients with macular diseases. Considering monocular and binocular viewing, we (a) explain how to identify the PRL and discuss the pitfalls associated with its measurement, (b) review the current hypotheses for PRL development, (c) assess whether the PRL is the new reference point of the ocular motor system, and discuss (d) the functional and (e) the clinical implications of the PRL. We conclude that the current definition of the PRL is probably incomplete and should incorporate the need to evaluate the PRL in the framework of binocular viewing. We emphasize the need for more research.

Expert consensus on low vision rehabilitation for patients with macular disease in China / 中华眼底病杂志

Maculopathy caused by various fundus diseases in the late stage is a common cause of low vision. Medical technology is difficult to reverse the loss of macular function currently, so interventions that help improve the visual system, utilize residual visual function, and improve quality of life deserve attention. Damage to the fovea of the macula does not mean that the entire retinal function is impaired. There may be one or more retinal regions adjacent to the fovea that can serve as a fixation center. It is possible to form stable paracentral fixation, complete functional remodeling of the visual system, and effectively utilize residual visual function by taking appropriate training on these potential paracentral fixation points for most patients. In 2021, a clinical guideline has been published for low vision rehabilitation in China. In order to strengthen the precise management of diseases and develop a standard operating procedure for visual training specifically for patients with low vision due to macular disease, the National Clinical Research Center for Eye Diseases initiated and organized relevant domestic experts, utilizing the latest research experience at home and abroad, and through repeated discussions, this consensus (International Practice Guideline Registration Number: PREPARE-2023CN199) was formed as a reference for ophthalmologists, optometrists and rehabilitation physicians in their clinical research and practice.

In Vivo Retinal Pigment Epithelium Imaging using Transscleral Optical Imaging in Healthy Eyes.

Objective: To image healthy retinal pigment epithelial (RPE) cells in vivo using Transscleral OPtical Imaging (TOPI) and to analyze statistics of RPE cell features as a function of age, axial length (AL), and eccentricity. Design: Single-center, exploratory, prospective, and descriptive clinical study. Participants: Forty-nine eyes (AL: 24.03 ± 0.93 mm; range: 21.9-26.7 mm) from 29 participants aged 21 to 70 years (37.1 ± 13.3 years; 19 men, 10 women). Methods: Retinal images, including fundus photography and spectral-domain OCT, AL, and refractive error measurements were collected at baseline. For each eye, 6 high-resolution RPE images were acquired using TOPI at different locations, one of them being imaged 5 times to evaluate the repeatability of the method. Follow-up ophthalmic examination was repeated 1 to 3 weeks after TOPI to assess safety. Retinal pigment epithelial images were analyzed with a custom automated software to extract cell parameters. Statistical analysis of the selected high-contrast images included calculation of coefficient of variation (CoV) for each feature at each repetition and Spearman and Mann-Whitney tests to investigate the relationship between cell features and eye and subject characteristics. Main Outcome Measures: Retinal pigment epithelial cell features: density, area, center-to-center spacing, number of neighbors, circularity, elongation, solidity, and border distance CoV. Results: Macular RPE cell features were extracted from TOPI images at an eccentricity of 1.6° to 16.3° from the fovea. For each feature, the mean CoV was < 4%. Spearman test showed correlation within RPE cell features. In the perifovea, the region in which images were selected for all participants, longer AL significantly correlated with decreased RPE cell density (R Spearman, Rs = -0.746; P < 0.0001) and increased cell area (Rs = 0.668; P < 0.0001), without morphologic changes. Aging was also significantly correlated with decreased RPE density (Rs = -0.391; P = 0.036) and increased cell area (Rs = 0.454; P = 0.013). Lower circular, less symmetric, more elongated, and larger cells were observed in those > 50 years. Conclusions: The TOPI technology imaged RPE cells in vivo with a repeatability of < 4% for the CoV and was used to analyze the influence of physiologic factors on RPE cell morphometry in the perifovea of healthy volunteers. Financial Disclosures: Proprietary or commercial disclosure may be found after the references.

Fixation Stability and Preferred Retinal Locus in Advanced Age-Related Macular Degeneration

Objectives: To evaluate fixation stability and characteristics of the preferred retinal locus (PRL) in patients with advanced age-related macular degeneration (AMD). Materials and Methods: Sixty-three eyes of 63 patients with AMD who presented to the low vision unit were included in this prospective study. Sociodemographic characteristics, eye examination findings, and reading performance results with the Minnesota Low Vision Reading test were evaluated. Microperimetry was used to evaluate fixation stability and PRL characteristics. Results: There was unstable fixation in 68% of the eyes, relative stable fixation in 27%, and stable fixation in 5%. The mean PRL-foveal distance was 5.15°±3.31° (range 0.75°-14.2°). PRL-foveal distance was greater in cases with unstable fixation than cases with stable fixation (p=0.023). Distance of the PRL from the lesion margin was not associated with absolute scotoma size or fixation stability (p=0.315, p=0.095, respectively). PRLs were most frequently located in the nasal quadrant (31%), followed by the superior quadrant (26%) of the retina. There was no significant relationship between PRL location and fixation stability (p=0.088). Fixation stability was significantly associated with reading speed (p=0.003). Conclusion: In advanced AMD, PRL-foveal distance is an important factor in fixation stability. Knowing the factors that affect fixation stability may be important in determining low vision rehabilitation strategies for these patients because of the strong association between fixation stability and reading speed.

Short-Term Clinical Results of Preferred Retinal Locus Training

Objectives: This study evaluated acoustic biofeedback training using microperimetry in patients with foveal scars and an eligible retinal locus for better fixation. Materials and Methods: A total of 29 eligible patients were enrolled in the study. The acoustic biofeedback training module in the MAIA (Macular Integrity Assessment, CenterVue®, Italy) microperimeter was used for training. To determine the treatment efficacy, the following variables were compared before and after testing: best corrected visual acuity (BCVA); MAIA microperimeter full threshold 4-2 test parameters of average threshold value, fixation parameters P1 and P2, and bivariate contour ellipse area (BCEA) for 63% and 95% of fixation points; contrast sensitivity (CSV 1000E Contrast Sensitivity Test); reading speed using the Minnesota Low-Vision Reading Test (MNREAD reading chart); and quality of life (NEI-VFQ-25). In addition, fixation stability parameters were recorded during each session. Results: The study group consisted of 29 patients with a mean age of 68.72±8.34 years. Median BCVA was initially 0.8 (0.2-1.6) logMAR and was 0.8 (0.1-1.6) logMAR after 8 weeks of preferred retinal locus training (p=0.003). The fixation stability parameter P1 improved from a mean of 21.28±3.08% to 32.69±3.69% (p=0.001) while mean P2 improved from 52.79±4.53% to 68.31±3.89% (p=0.001). Mean BCEA 63% decreased from 16.11±2.27°2 to 13.34±2.26°2 (p=0.127) and mean BCEA 95% decreased from 45.87±6.72°2 to 40.01±6.78°2 (p=0.247) after training. Binocular reading speed was 38.28±6.25 words per minute (wpm) before training and 45.34±7.35 wpm after training (p<0.001). Statistically significant improvement was observed in contrast sensitivity and quality of life questionnaire scores after training. Conclusion: Beginning with the fifth session, biofeedback training for a new trained retinal locus improved average sensitivity, fixation stability, reading speed, contrast sensitivity, and quality of life in patients with macular scarring.

An Overview of Preferred Retinal Locus and Its Application in Biofeedback Training for Low-Vision Rehabilitation.

Central vision loss (CVL) caused by macular damage generally disables common daily tasks, which cannot be reversed by present treatments. Fortunately, it has been found that biofeedback training by inducing or reinforcing preferred retinal locus (PRL) as an eccentric fixation reference contributes to the improvement of visual performance in patients with CVL. However, the clinical application is still under controversy due to poor knowledge of its fundamental and inconsistent practical standards. This article aims to summarize the possible rationale for the development, location, re-location and evaluating indicators of PRL, and the general apparatus, protocol, and outcome of biofeedback PRL training.

Research advances of microperimetric biofeedback training for low-vision rehabilitation in macular diseases / 国际眼科杂志(Guoji Yanke Zazhi)

@#In clinical practice, many macular diseases in advanced stages such as age-related macular degeneration(ARMD)and Stargardt disease are manifested reduced visual acuity, unstable and even paracentral fixation resulting from the central scotoma followed by the scarring of neovascular fibres or the impairment of photoreceptors and retinal pigment epithelium, which cause great distress to patients' life, work and psychology. For a long time, there have been limited rehabilitation treatments for such patients. However, recent articles have indicated that biofeedback training by using microperimetry is expected to enhance neurosensory adaptation by achieving cortical plasticity, and makes better use of residual retinal function to help those with low vision associated with central scotoma consolidate or establish stable central or paracentral fixation, thereby improving visual function including visual acuity and reading speed. In order to improve the understanding of this rehabilitation therapy, this article will overview the mechanism and protocol of microperimetric biofeedback training(MBFT), the selection of the preferred retinal locus, the clinical application in macular diseases and its prospects.

Restitution of potential visual acuity in low vision patients with the use of yoke prisms

Purpose: To determine the efficacy of prisms when used for redirection of incoming images towards the preferred reinal loci (PRLs) for restitution of potential visual acuity (PVA) in low vision cases with age-related macular degeneration (AMD).MethodsRetrospective comparative interventional case series review. Low vision rehabilitation (LVR) protocol used included best corrected visual acuity (BCVA), PVA, topographic PRL identification and use of prisms to produce image redirection to the presumed PRL. The primary outcome measure selected for analysis was BCVA for viewing distance targets after use of yoke prisms.ResultsImage relocation with prisms in patients with AMD resulted in significantly better BCVA levels (t32 = 8.57, p < 0.0001) in the better eye. Distance BCVA levels achieved were almost identical to PVA levels (t32 = 0.415, p < 0.681) (y= -0.136 + 1.195x, r = 0.8333, p < 0.001).ConclusionsUse of yoke prisms for image redirection towards a peripheral identifiable PRL may result in PVA restitution in most cases. (AU)

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.

Characteristics of Preferred Retinal Locus in Eyes with Central Vision Loss Secondary to Different Macular Lesions.

OBJECTIVE: Preferred retinal locus (PRL) training has been applied to low-vision rehabilitation for patients with central vision loss (CVL). This study aimed to explore the characteristics of a natural PRL in eyes with different macular lesions. The data may be useful in customizing training programs. METHODS: A total of 72 eyes with CVL were included and assigned into two groups. In group A, 29 eyes diagnosed with macular holes featured relatively sharp borders and small areas of lesions. In group B, 44 eyes showed lesions characterized by irregular borders and large areas. The PRL location relative to a scotoma in the retina, fixation stability, and the average threshold surrounding the PRL were determined and compared between the two groups. RESULTS: In group A, the PRL was located above in 48.28%, below in 27.59%, left in 62.07%, right in 31.03%, and inside in 3.45% of the eyes. In group B, the PRL was located above in 39.53%, below in 4.65%, left in 44.19%, right in 6.98%, and inside in 27.91% of eyes. The amount of retinal displacement occurring within 1° from an initial reference point (P< .05) and the 95% bivariate contour ellipse area (P< .05) in group A were respectively higher and lower than those in group B. However, the average thresholds around the PRLs in the two groups showed no significant difference (P > .05). CONCLUSIONS: A PRL to the left of or above a scotoma tends to develop to avoid the right and inferior field defect, regardless of the scale and boundary of lesions. Although light sensitivity around a PRL shows no relation to lesion features, fixation stability is worse in irregular and large lesions.

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.

Restitution of potential visual acuity in low vision patients with the use of yoke prisms.

PURPOSE: To determine the efficacy of prisms when used for redirection of incoming images towards the preferred reinal loci (PRLs) for restitution of potential visual acuity (PVA) in low vision cases with age-related macular degeneration (AMD). METHODS: Retrospective comparative interventional case series review. Low vision rehabilitation (LVR) protocol used included best corrected visual acuity (BCVA), PVA, topographic PRL identification and use of prisms to produce image redirection to the presumed PRL. The primary outcome measure selected for analysis was BCVA for viewing distance targets after use of yoke prisms. RESULTS: Image relocation with prisms in patients with AMD resulted in significantly better BCVA levels (t32 = 8.57, p < 0.0001) in the better eye. Distance BCVA levels achieved were almost identical to PVA levels (t32 = 0.415, p < 0.681) (y= -0.136 + 1.195x, r = 0.8333, p < 0.001). CONCLUSIONS: Use of yoke prisms for image redirection towards a peripheral identifiable PRL may result in PVA restitution in most cases.

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.

Effect of Background Brightness on Preferred Retinal Loci in Patients With Macular Disease.

Purpose: To evaluate the effect of background brightness on the preferred retinal locus (PRL) in patients with macular disease. Methods: The study included 27 eyes (27 patients) with macular disease. Microperimetry (MP) was performed to evaluate the PRL and retinal sensitivity (RS) at 10 cd/m2. A prototypical device was used to evaluate the PRL at 650 cd/m2. Patients were divided into two groups: central fixation (CF) and eccentric fixation (EF). Results: The PRLs under different brightness levels differed significantly (P < 0.001) in 15 of 27 eyes (two of 13 eyes in the CF group and 13 of 14 eyes in the EF group). The best-corrected visual acuities (BCVAs) in eyes with different PRLs were significantly worse (P = 0.019) than in eyes with one PRL, although the foveal RS did not differ significantly. In patients with BCVAs over 0.1, the PRLs differed in four of 13 eyes in the CF group and in three of four eyes in the EF group (P > 0.05); in patients with BCVAs of 0.1 or lower, the PRLs differed in one of four eyes and 10 of 10 eyes, respectively (P = 0.011). Conclusions: In patients with macular disease, PRLs can change depending on the surrounding brightness. It may be beneficial to evaluate PRLs under brighter background conditions (e.g., in ambient light) when performing visual rehabilitation for these patients. Translational Relevance: This study provides important information for visual rehabilitation of patients with macular disease.

Effect of Disease Progression on the PRL Location in Patients With Bilateral Central Vision Loss.

Purpose: To investigate the effect of disease progression on the monocular preferred retinal locus (PRL) of the better eye (BE) and worse eye (WE) of patients with central vision loss. Methods: Fifty-one patients with bilateral macular diseases were included. The monocular PRL was recorded for each eye (N = 102 eyes) with the MP-1 microperimeter in two visits that were 458 ± 249 days apart. For each eye and visit, the PRL distance from the former fovea, polar angle, and scotoma size were measured. The change in PRL location from visit 1 to visit 2 was evaluated with the differential map analysis. Results: Scotoma size increased significantly in both eyes. The PRL distance from the former fovea increased significantly from visit 1 to visit 2 in the BE, but not in the WE. The polar angle was relatively stable in both visits for the BE. The change in PRL location in the BE was predicted only by the PRL distance from the former fovea in visits 1 and 2, but not by polar angle or scotoma size. For the WE, the change in PRL location depended on the change in PRL location in the BE, rather than on measurements made on that eye. Conclusions: Disease progression affects monocular PRL location differently in the 2 eyes. The results suggest a recalibration of the oculomotor system with its reference at the PRL from the BE. Translational Relevance: These findings are important for deciding the course of treatment and/or for developing rehabilitation techniques focusing on PRL relocation.

A new perceptual training strategy to improve vision impaired by central vision loss.

Patients with central vision loss depend on peripheral vision for everyday functions. A preferred retinal locus (PRL) on the intact retina is commonly trained as a new "fovea" to help. However, reprogramming the fovea-centered oculomotor control is difficult, so saccades often bring the defunct fovea to block the target. Aligning PRL with distant targets also requires multiple saccades and sometimes head movements. To overcome these problems, we attempted to train normal-sighted observers to form a preferred retinal annulus (PRA) around a simulated scotoma, so that they could rely on the same fovea-centered oculomotor system and make short saccades to align PRA with the target. Observers with an invisible simulated central scotoma (5° radius) practiced making saccades to see a tumbling-E target at 10° eccentricity. The otherwise blurred E target became clear when saccades brought a scotoma-abutting clear window (2° radius) to it. The location of the clear window was either fixed for PRL training, or changing among 12 locations for PRA training. Various cues aided the saccades through training. Practice quickly established a PRL or PRA. Comparing to PRL-trained observers whose first saccade persistently blocked the target with scotoma, PRA-trained observers produced more accurate first saccade. The benefits of more accurate PRA-based saccades also outweighed the costs of slower latency. PRA training may provide an efficient strategy to cope with central vision loss, especially for aging patients who have major difficulties adapting to a PRL.

Changes in eye movement parameters in the presence of an artificial central scotoma.

BACKGROUND: Central vision loss, such as in the case of age-related macular degeneration (AMD), has a a major negative impact on patients' quality of life. However, some patients have shown spontaneous adaptive strategies development, mostly relying on their peripheral vision. OBJECTIVE: This study assesses eye movement and eccentric visual function adaptive behaviors of a healthy population in the presence of simulated central vision loss. We wished to determine how central vision loss affects eye movements, specifically the foveal-target alignment. METHODS: Fifteen healthy participants (7 females, M = 21.69, SD = 2.13) discriminated the orientation of a Gabor relative to the vertical located at 12 deg of eccentricity to the right of fixation, in the presence of a gaze-contingent artificial central scotoma either visible or invisible. The artificial central scotoma was 4° diameter in order to simulate an earlier stage of degenerative disease while still impairing foveal vision. The target's orientation varied between 10° counter-clockwise and 10° clockwise. Each participant performed four blocks of 75 trials each per day over 10 days, the first day being a baseline without scotoma. RESULTS: We found changes in the endpoints of the 1st saccade over the practice days. The most common pattern was a gradual upward shift. We also observed a significant increase in discrimination performance over the 9 days of practice. We did not find any difference linked to the scotoma types. CONCLUSIONS: These findings suggest that the presence of an artificial central scotoma combined with a challenging discrimination task induces both changes in saccade planning mechanisms, resulting in a new eccentric-target alignment, and improvements in eccentric visual functions. This demonstrates the potential of this research paradigm to understand and potentially improve visual function in patients with central vision loss.

Asymmetries of reading eye movements in simulated central vision loss.

Patients with central vision loss are forced to use an eccentric retinal location as a substitute for the fovea, called a preferred retinal locus, or PRL. Clinical studies have shown that patients habitually choose a PRL located either to the left, and/or below the scotoma in the visual field. The position to the right of the scotoma is almost never chosen, even though this would be theoretically more suitable for reading, since the scotoma no longer blocks the upcoming text. In the current study, we tested whether this asymmetry may have an oculomotor basis. Six normally sighted subjects viewed page-like text with a simulated scotoma, identifying embedded numbers in "words" comprising random letters. Subjects trained and tested with three different artificial PRL ("pseudo-PRL," or pPRL) locations: inferior, to the right, or to the left of the scotoma. After several training blocks for each pPRL position, subjects were found to produce reliable oculomotor control. Both reading speed and eye movement characteristics reproduced observations from traditional paradigms such as page-mode reading and RSVP for an advantage for an inferior pPRL. While left and right positions resulted in similar reading speeds, we observed that a right pPRL caused excessively large saccades and more direction switches, exhibiting a zig-zag pattern that developed spontaneously. Thus, we propose that patients' typical avoidance of pPRL positions to the right of their scotoma could have an oculomotor component: the erratic eye motion might potentially negate the perceptual benefit that this pPRL would offer.

Smooth pursuit of amodally completed images.

In order to evaluate the effect of the parafoveal area of the retina on smooth pursuit, we compared the horizontal smooth pursuit of visible and amodally completed stimuli in people with central vision loss and controls. In the amodally completed stimuli, a black mask covered the bottom vertex of a moving diamond which is the feature whose movement participants had to track. Both the visible and the amodally completed stimuli moved along regular and irregular sinusoidal motion paths. Our results show that people with central vision loss are able to track a perceptually completed moving stimulus albeit with lower gain, larger tracking errors, and more saccadic eye movements than people with normal vision. Just as the controls, however, people with central vision do better in the no mask condition showing that visual feedback from eccentric vision can improve performance.