Preferred Retinal Loci Location Research Articles

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.

Rehabilitation with biofeedback training in age-related macular degeneration for improving distance vision

Biofeedback training (BT) is a modern method for enhancing the use of preferred retinal loci (PRL) retraining for new retinal loci (TRL), hence improving far and near vision. This article attempts to clarify the optimal methodology for BT and the types of patients who can benefit most from BT. This is a retrospective review of cases who received BT with the macular integrity assessment (MAIA) microperimetre. Outcome measures selected for analysis were visual acuity, PRL location, fixation stability, fixation pattern orientation, reading acuity, critical print size, and reading speed. Out of 30 cases who received BT, only those with age-related macular degeneration and visual acuity of logMAR 0.8 (20/126) or poorer showed a visual acuity gain (statistically significant of 12 letters) after BT. Those with other diagnoses and those with residual Early Treatment Diabetic Retinopathy Study best-corrected visual acuity of logMAR of 0.7 (20/100) or better showed only positive trends for visual acuity and a negative trend for fixation stability. All subjects showed a shift in PRL location toward the superior quadrant of the retina (p < 0.02) in those who received BT. BT seems to offer patients a unique and efficient modality to improve distance vision outside of using optical devices.

Characteristics of the preferred retinal loci of better and worse seeing eyes of patients with a central scotoma

ObjectivePatients with central vision loss develop preferred retinal loci (PRLs) in the eccentric retina. The characteristics of the PRLs for the better eye (BE) are well studied, but not those of the worse eye (WE). We examined the distribution of monocular PRLs in the visual field (VF), as well as visual acuity, fixation stability, and PRL eccentricity for the BE and WE of patients with central vision loss. DesignRetrospective consecutive case series. ParticipantsA total of 87 BE and 50 WE of patients with central vision loss. MethodsVisual acuity, fixation stability, PRL location, and PRL eccentricity measures were retrieved from our database. PRL location was categorized into 5 VF segments: central, superior, inferior, left, and right. ResultsFor BE, PRL frequency distribution was significantly different for the 5 VF segments, χ2(4) = 19.9, p = 0.001. Most PRLs occurred in inferior (31%) and left (31%) VF segments. Visual acuity, fixation stability, and PRL eccentricity depended on the VF segment. Visual acuity correlated with fixation stability and PRL eccentricity. For WE, PRL frequency distribution was not different for the 5 VF segments and visual acuity was not dependent on the VF segment. No relationships between visual acuity and PRL eccentricity or fixation stability were found. ConclusionsDifferent patterns of PRL characteristics were found for BEs and for WEs. These findings are important to consider when factors such as PRL eccentricity, visual acuity, fixation stability, and PRL location are used as outcome measures after treatment or rehabilitation and when monitoring disease progression.

Similar Sensitivity to Ladder Contours in Macular Degeneration Patients and Controls.

PurposeTo determine whether people with central field loss (CFL) from macular degeneration have improved ability to recognize a particularly difficult spatial configuration embedded in noise, the peripherally-viewed ‘ladder contour’. The visibility of these configuration has been linked to general contour integration ability and crowding limitations in peripheral vision.MethodsWe used a trial-based yes-no task. CFL patients and normally-sighted controls performed the task, looking for ladder contours embedded in a field of randomly oriented Gabor patches, at a range of stimulus presentation times (varying stimulus difficulty). Viewing eccentricity in CFL patients was set by their preferred retinal loci (PRLs) and matched artificially in the control group. The contours were presented so as to be tangent to the CFL region, given a patient’s PRL location.ResultsCFL and normally-sighted groups performed similarly on the task. The only significant determinant of performance was the viewing eccentricity.ConclusionsCFL patients do not seem to develop any improved ability to recognize ladder contours with their parafoveal retina, which suggests that there is no underlying improvement in contour integration or reduction in crowding limitations in the region of the PRL despite extended daily use.

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

ObjectiveTo 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. DesignRetrospective study. ParticipantsThirty subjects affected by age-related macular degeneration with absolute central scotoma. MethodsA 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. ResultsMean 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). ConclusionsBoth regular biofeedback and flickering pattern biofeedback training seem to improve visual functions. More benefits seem to be accrued, however, with flickering pattern biofeedback training.

Preferred Retinal Loci Relationship to Macular Scotomas: A10-Year Comparison

Age-related maculopathy is the leading cause of vision loss among adults in developed countries, and its prevalence is expected to double over the next decade (Congdon et al., 2004; Friedman et al., 2004). The two forms of age-related maculopathy--exudative and nonexudative--are capable of affecting the macula, with potential symptoms including decreased contrast sensitivity, decreased visual acuity, abnormal adaptation to the dark, and central or pericentral scotomas (Jager, Mieler, & Miller, 2008). When a central scotoma impairs the ability of the fovea to distinguish detail, one or more preferred retinal loci (PRL) (Schuchard & Raasch, 1992; von Noorden & Mackensen, 1962; White & Bedell, 1990), also known as pseudo-foveas (Guez, Le Gargasson, Rigaudiere, & O'Regan, 1993), naturally develop at eccentric retinal locations and become the new points of fixation. The location of the PRL varies from person to person, as does the ability to maintain steady fixation with the PRL and to use it for reading and activities of daily living (Dalgleish & Naylor, 1963; Fletcher, Schuchard, & Watson, 1999; Timberlake et al., 1986; Whittaker, Budd, & Cummings, 1988). Fletcher and Schuchard (1997) reported the results of a study examining patterns of PRL ability and location relative to macular scotomas. They mapped dense scotomas and determined the location of the PRL in 1,339 eyes in 825 persons with a scanning laser ophthalmoscope during a standard low vision rehabilitation evaluation. Fletcher and Schuchard created a scoring system to measure the pursuit ability, fixation stability, and saccadic ability of the PRL. They determined the characteristics of dense scotomas within 2.5 degrees of the PRL or fovea. Of the 1,339 eyes, 84% (1,130) demonstrated an established PRL, ranging in size from 1.0 degrees to 9.0 degrees in diameter, and 82.5% had a central dense scotoma. The PRL had no dense scotomas on any border in 14.8% of the eyes. It had one, two, or three borders with a dense scotoma in 39.7%, 19.0%, and 9.0% of the eyes, respectively. Ring scotomas, bordering the PRL on four borders, were present in 17.4% of the eyes. Of the eyes with one scotomatous border, most had a field defect located either superior (39.0%) or to the right (33.7%). It was less common for the eyes to have field defects to the left or inferior, with 19.9% and 7.5% of the eyes, respectively. This report presents a 10-year comparison of these previous findings. It examines whether the PRL characteristics of persons with low vision remained steady over the ensuing decade. Changes in PRL and visual field characteristics among persons with low vision over time could have implications for the approaches of low vision rehabilitation professionals to training in eccentric viewing and other rehabilitation techniques. METHODS The study used 271 persons who were referred to the Frank Stein and Paul S. May Center for Low Vision Rehabilitation at California Pacific Medical Center (CPMC) in San Francisco between 2005 and 2007. All consecutive patients with low vision were included in the study, regardless of age, gender, race, and other demographic variables. Participants were excluded only if they lacked the cognitive or physical ability to complete a macular perimetry examination, as determined by the clinical impression of the ophthalmologist. Approval from the institutional review board was obtained from CPMC for the retrospective analyses of charts. As part of the standard low vision rehabilitation evaluation, an ophthalmologist measured visual acuity with the Early Treatment of Diabetic Retinopathy System chart (Ferris, Kassoff, Bresnick, & Bailey, 1982). The characteristics of the scotoma and PRL were measured with a Scanning Laser Ophthalmoscope (SLO; SLO-101, Rodenstock, Dusseldorf, Germany). The SLO was outfitted with a smart microperimetry (MacKeben & Gofen, 2007) program with a gaze-contingent display that automatically monitors eye movements, blinks, and other factors. …

Scotoma displacement in the macular mapping test as a tool for identification of preferred retinal loci

ObjectiveTo clarify the efficacy of the macular mapping test (MMT) to identify eccentric fixation with preferred retinal loci (PRL). DesignRetrospective observational case series from archived data. ParticipantsCases with age-related macular degeneration with low vision in both eyes and best corrected visual activity (BCVA) of 20/50 to 20/400 in the better eye. MethodsIdentification of preferred retinal loci with the Nidek MP-1 microperimeter and correlation with scotoma displacement on perimetry records as recorded with the MMT. ResultsWe recruited data on 43 patients (12 males and 31 females), aged 57–96 years (mean 84.05 years ± SD 8.00). Mean BCVA was 0.9 ± 0.32 SD logMar units (20/160). PRL location matched the direction of scotoma displacement in 32 study subjects (74.41%, p < 0.002). ConclusionsScotoma displacement recorded with the MMT offers reasonable indirect estimates on PRL location.

The relationship between scotoma displacement and preferred retinal loci in low-vision patients with age-related macular degeneration

Objective: Adaptive strategies in low-vision patients with age-related macular degeneration use preferred retinal loci (PRLs) for the purpose of achieving better visual function. In the process of redirecting the eye toward the PRL, central scotomata are displaced eccentrically. The consequential effect of the first on the second may offer an indirect method for PRL identification. The purpose of this study was to clarify the relationship between scotoma displacement and PRL location. Design: Prospective, nonrandomized, observational case series. Participants: Forty-one adults with a confirmed diagnosis of age-related macular degeneration. Methods: Scotoma characteristics were obtained with automated perimetry. PRL topography was obtained with the Nidek MP-1 instrument. Outcome measures selected for this study were scotoma displacement and PRL eccentricities estimates. Results: We tested 16 males and 25 females aged 70–98 years (mean 82.5 [SD 6.71] years) with best-corrected visual acuity of 0.81 (SD 0.24) logMar units (20/128). PRL location logically matched scotoma displacement in 30 study subjects (73.17%, p < 0.00432). In this subgroup ( n = 30), PRL eccentricity (5.55 [SD 3.35]°) was almost identical to scotoma displacement eccentricity (5.22 [SD l.98]°) ( p < 0.65). Conclusions: Scotoma displacement recorded with macular perimetry methods offers reasonable indirect estimates of PRL location.

Concept of a functional retinal locus in age-related macular degeneration

Purpose: Preferred retinal loci used for eccentric fixation in patients with age-related macular degeneration (AMD) may be different from the eccentric neighbouring loci of highest retinal sensitivity. This study was designed to highlight the conceptual difference between the 2 and the concept of a functional retinal locus encompassing both the preferred retinal locus and the locus with highest retinal sensitivity. Design: Prospective, nonrandomized, observational case series. Participants: We recruited 15 adults with documented AMD, low vision, and best-corrected visual acuity of 20/50–20/400 in the better eye. Methods: Automated microperimetry methods were used to assess topographic retinal sensitivity and location of preferred retinal loci. Results: Mean (SD) age for the group was 85.1 (6.5) years. Mean (SD) best-corrected visual acuity measured was 0.88 (0.25) logMar units (20/150). The mean (SD) eccentricity of the preferred retinal locus used forfixation was different from the eccentricity of the area with highest retinal sensitivity in the same eye (7.53° [2.47°] vs 9.30° [2.93°], respectively; p < 0.0003). The oculomotor efficiency score measured 82%. The mean (SD) retinal sensitivity at the preferred retinal loci was inferior to that of loci with highest retinal sensitivity (5.83 [4.26] vs 8.60 [3.06] dB, respectively; p < 0.0007). The highest correlation was measured between potential visual acuity estimates and estimates of retinal sensitivity at the highest retinal sensitivity loci ( p < 0.0048). Conclusions: Preferred retinal loci and highest retinal sensitivity loci are not identical in AMD cases. A new concept of functional retinal locus is proposed to define their relation. A new concept of an oculomotor efficiency score is proposed to define oculomotor abilities when macular function is lost.

Plasticity of fixation in patients with central vision loss

The aim of this study was to explore the plasticity of fixation in patients with central vision loss. Most of these patients use preferred retinal loci (PRLs) in the healthy eccentric part of the retina to fixate, but fixation stability and retinal location are not always optimal for best visual performance. This study examined whether fixation stability and a new PRL location can be trained and whether these changes in ocular motor control transfer into better reading performance. Six patients with age-related macular degeneration participated in the study. Fixation stability measurements, microperimetry, and auditory biofeedback training were performed with the MP-1 microperimeter. The auditory biofeedback was used during five 1-h long training sessions to improve fixation and relocate the PRL. Fixation location and stability were recorded while viewing four different targets: a cross, a letter, a word, and a nine-cycle radial grating. Visual acuity was assessed with the Early Treatment Diabetic Retinopathy Study (ETDRS) chart and reading performance with the MNRead test. The results showed that all patients developed a new PRL in an optimal location for reading, and they were able to use it consistently while viewing different targets. Fixation stability improved 53% after training. Learning transferred to the old PRL even though fixation stability at this location was not trained. All these improvements in ocular motor control translated into better reading performance: reading speed improved 38% and reading acuity and critical print size gained two lines. We conclude that the ability of the ocular motor system to fixate is flexible in patients with central vision loss: a new PRL can be trained, fixation stability can be improved, and learning transfers to an untrained location. These gains in ocular motor control result in better visual performance. This property can be successfully used to optimize the residual vision of patients with central vision loss.

Fixation in Patients with Juvenile Macular Disease

The instability of fixation with central scotoma has been mainly studied in patients with age-related macular diseases (MDs). However, early macular lesions can lead to different characteristics of fixation. The aim of this work was to study fixation in patients with juvenile MD. Eye movements of 10 patients and 10 controls were monitored during fixation. Visual fields were assessed by static perimetry to determine the extent of the field defects. Eye movements were separated into saccades and drifts, with fixation stability assessed by bivariate contour ellipse area (BCEA). To quantify the number and location of preferred retinal loci (PRL), the kernel density estimator and expectation maximization for mixtures of gaussians were used. Patients have worse fixation stability than controls and large BCEAs resulted in more than one PRL. It was found that central field defects (10 degrees) have negative correlation with the size of BCEA. In addition, the meridian of saccades during fixation was correlated with the meridian inter-PRL. Patients with juvenile MDs have large BCEAs, frequently associated with two PRL. Similar results had been found for patients with age-related MDs. Also, the meridian of involuntary saccades during fixation was found to be correlated with the location of PRLs, suggesting a useful role of these movements in alternating between them.