Preferred Retinal Locus Location Research Articles

Binocularity Principles of PRL Development in Patients With Macular Disease.

PurposeWe tested the hypothesis that binocularity requirements for correspondence play a role in establishing the preferred retinal locus (PRL) in macular degeneration.MethodsMonocular PRL locations in 202 eyes of 101 patients with macular degeneration (79 ± 10 years) were recorded with the MP1 microperimeter. Corresponding PRLs were those with similar polar angle and distance from former fovea in the better eye (BE) and the worse eye (WE).ResultsOn average, the PRL in the BE was in the foveal proximity at 1.1 ± 0.99 degrees for 55 patients (foveal-driven PRL) and eccentrically at 6.9 ± 3.4 degrees for 46 patients with central lesions involving the fovea (peripheral-driven PRL). For the foveal-driven PRL group, the PRL in the BE was not affected by the status of the WE. In 100% of cases, the monocular PRL in the WE was in a corresponding location either on functioning retina or onto the lesion, or would fall onto the lesion during binocular viewing. For the peripheral-driven PRL group, the PRL location depended on the lesion size in both eyes to maximize correspondence and/or the function of peripheral vision during binocular viewing. In this group, PRL correspondence status was different for those with equal, unequal, or extensive lesions in both eyes.ConclusionsBinocularity requirements for correspondence play an important role in determining the PRL location. We formulated two principles based on whether the BE has foveal sparing (foveal-driven PRL) or central lesions affecting the fovea (peripheral-driven PRL). The PRL should be evaluated in the framework of binocular viewing.

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.

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

ABSTRACT 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.

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

ABSTRACT 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.

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

PurposeTo 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.MethodsFifty-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.ResultsScotoma 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.ConclusionsDisease 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 RelevanceThese findings are important for deciding the course of treatment and/or for developing rehabilitation techniques focusing on PRL relocation.

Changes in the Properties of the Preferred Retinal Locus with Eccentric Viewing Training.

This study explores whether eccentric viewing training (EVT) changes the properties of the retinal area used for fixation in subjects with bilateral macular disease. The data presented demonstrate the feasibility of conducting a randomized controlled trial on EVT. Patients with bilateral central scotomas adopt other retinal area(s) called preferred retinal locus to substitute the blind fovea. EVT is offered with the goal to improve functional vision by learning how to identify and use a more useful retinal area for fixation-a trained retinal locus-and/or to improve fixation stability with their existing preferred retinal locus. An observational study was conducted to determine whether patients change and adopt a new trained retinal locus location and/or if fixation stability improves after EVT. Seventy-six patients with bilateral central scotomas received EVT from an experienced rehabilitation therapist. Retinal locations for repeated fixations and sizes of central scotomas of the better eye were recorded before and after EVT with a scanning laser ophthalmoscope. The position and area of the 95% confidence bivariate ellipse that defines the retinal area in which 95% of fixations occur were analyzed. We observed no significant difference between the size of the area of the fitted ellipses before (mean [SD], 26.4° [19.7°]) and after (mean [SD], 24.8° [20.9°]) EVT (P = .54). However, we observed a shift in the preferred retinal locus location after EVT (P < .0001). The mean (SD) shift in the position of the center of fixation after EVT was 7.5° (5.2°; range, 0.45 to 23°). This mean difference was larger than would be expected from average within-subject fixation stability. The location of the retinal area used for fixation changes after EVT. Fixation stability does not change after EVT. These preliminary data are yet to be confirmed with the use of a control group.

PREFERRED RETINAL LOCUS LOCATIONS IN AGE-RELATED MACULAR DEGENERATION.

An evaluation of the preferred retinal locus (PRL) in patients with age-related macular degeneration and a central scotoma is becoming a standard of care in the practice of low-vision rehabilitation. This is a retrospective study of PRL specifications and whether they have a correlation with the best-corrected visual acuities of patients with age-related macular degeneration. Seventy-two patients with macular degeneration (144 eyes) were included in the study. The PRLs were evaluated monocularly with a scanning laser ophthalmoscope. Each PRL's location, the fovea-PRL distance, the PRL edge of the lesion distance, and PRL stability were measured with the built-in caliper of the ophthalmoscope. The most frequent location of a PRL was nasal (29.2%). The PRL was located in the left visual field of 34.0% of the patients. The best-corrected visual acuity values were positively correlated with the lesion's vertical and horizontal dimensions, as well as its surface area, the PRL-fovea distance, the PRL border of the lesion distance, and PRL stability. The clinical PRL evaluation methodology that we describe can be used to facilitate making decisions on how to provide best visual rehabilitation to patients with a central scotoma.

Visual Acuity Is Not the Best at the Preferred Retinal Locus in People with Macular Disease.

Little is known about how the preferred retinal locus (PRL) develops in patients with macular disease. We found that acuity is worse at the PRL than at other retinal locations around the scotoma, suggesting that the selection of the PRL location is unlikely to be based on optimizing acuity. Following the onset of bilateral macular disease, most patients adopt a retinal location outside the central scotoma, the PRL, as their new retinal location for visual tasks. Very little information is known about how the location of a PRL is chosen. In this study, we tested the hypothesis that the selection of the location for a PRL is based on optimizing visual acuity, which predicts that acuity is the best at the PRL, compared with other retinal locations. Using a scanning laser ophthalmoscope that allowed us to position visual targets at precise retinal locations, we measured acuity psychophysically using a four-orientation Tumbling-E presented at the PRL and at multiple (ranged between 23 and 36 across observers) locations around the scotoma for five observers with bilateral macular disease. For all five observers, the acuity at the PRL was never the best among all testing locations. Instead, acuities were better at 15 to 86% of the testing locations other than the PRL, with the best acuity being 17 to 58% better than that at the PRL. The locations with better acuities did not cluster around the PRL and did not necessarily lie at the same distance from the fovea or the PRL. Our finding that acuity is worse at the PRL than at other locations around the scotoma implies that the selection of the PRL location is unlikely to be based on optimizing acuity.

Mechanisms of Image Stabilization in Central Vision Loss: Smooth Pursuit.

In addition to understanding the adaptive mechanisms of eccentric viewing during smooth pursuit, the ocular motor adaptations of patients with central vision loss give us a better understanding of the basic mechanisms of smooth pursuit in the healthy visual system. For patients with age-related macular degeneration and controls with normal vision, we examined the closed-loop gain of horizontal and vertical smooth pursuit eye movements as a function of stimulus speed and direction. We hypothesized that pursuit gain functions would be affected by stimulus speed and the location of the preferred retinal locus (PRL) in relation to the scotoma as determined by a fixation stability task using a microperimeter. Specifically, that a PRL on the left of the scotoma in the visual field would decrease the rightward gain relative to the leftward gain and a PRL below the scotoma in the visual field would decrease the upward gain. Ten patients and 15 controls were tested in a step-ramp procedure with direction (left/right for horizontal motion; up/down for vertical motion), speed (5, 10, 15, 20, and 30 deg/s), and five replication conditions randomized and blocked by orientation (horizontal vs. vertical). Horizontal pursuit had a higher gain than vertical pursuit. The two eyes of the patients moved conjugately with similar smooth pursuit gains. For horizontal pursuit, all patients, regardless of PRL location, showed significantly better pursuit of leftward motion. For vertical pursuit, downward pursuit had a higher gain than upward pursuit for most patients. PRL location was not predictive of the directional preponderance of pursuit performance. These results imply that patients may not use the PRL that was initially found during a static fixation task; they may adapt to the task by using a PRL that appears more suitable.

Can positions in the visual field with high attentional capabilities be good candidates for a new preferred retinal locus?

The sustained component of visual attention lowers the perceptual threshold of stimuli located at the attended region. Attentional performance is not equal for all eccentric positions, leading to variations in perception. The location of the preferred retinal locus (PRL) for fixation might be influenced by these attentional variations. This study investigated the relation between the placement of sustained attention and the location of a developed PRL using simulations of central scotoma. Thirteen normally sighted subjects participated in the study. Monocular sustained attention was measured in discrete eccentric locations of the visual field using the dominant eye. Subsequently, a six degrees macular scotoma was simulated and PRL training was performed during eight ten-minutes blocks of trials. After training, every subject developed a PRL. Subjects with high attentional capabilities in the lower hemifield generally developed PRLs in the lower hemifield (n=10), subjects with high attentional capabilities in the upper hemifield developed PRLs in the upper hemifield (n=2) and one subject with similar attentional capabilities in the upper and lower hemifield developed the PRL on the upper hemifield. Analyzed individually, the results showed that 70% of the subjects had a PRL location in the hemifield where high attentional performance was achieved. These results suggest that attentional capabilities can be used as a predictor for the development of the PRL and are of significance for low vision rehabilitation and for the development of new PRL training procedures, with the option for a preventive attentional training in early macular disease to develop a favorable PRL.

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.

Preferred retinal locus profile during prolonged fixation attempts

ObjectiveThe retinal area or location used during any fixation attempt defines the preferred retinal locus (PRL). It is presumed that during prolonged fixation attempts there may be various representative reference points within the PRL area. This study aims to clarify this presumption. DesignProspective, nonrandomized, observational case series. ParticipantsSixty-five eyes of 41 patients from the University of Nottingham, Queen’s Medical Centre Retina and Low Vision Clinics. MethodsA total of 65 eyes of 41 patients from the University of Nottingham, Queen’s Medical Centre Retina and Low Vision Clinics were assessed for PRL using the Macular Integrity Assessment (MAIA) microperimetry equipment (CenterVue, Padova, Italy). The MAIA allows automatic calculation for 2 points named PRL_initial (PRLi), which is calculated after the first 10 seconds of fixation, and PRL_final (PRLf), which is calculated after the completion of all fixation attempts during the microperimetry test. ResultsEstimates of PRLi and PRLf were produced for all patients. Forty-six (71%) eyes were classified as having stable fixation; 40 of the 46 eyes (87%) had both PRLs location over the fovea centralis. Nineteen of 65 eyes (29%) were classified as having unstable or relatively unstable fixation; different PRLi and PRLf locations were found in 18 (95%) of the 19 eyes, including 13 (68%) with central geographic atrophy secondary to dry age-related macular degeneration. The mean rate of change was 5.3 units in fixation per unit change in distance in both PRLi and PRLf. ConclusionsThe representative points during prolonged fixation attempts may vary at different stages of fixation. This is reflected in the characteristics of fixation stability of the patients and presents a possible association with main pathology responsible for low vision.

Fixation Control before and after Treatment for Neovascular Age-Related Macular Degeneration

We studied changes in visual acuity (VA), fixation stability, and location of the preferred retinal locus (PRL) after treatment for unilateral neovascular age-related macular degeneration (AMD) for previously untreated eyes. Concomitant changes in fixation stability, PRL, and VA in the untreated fellow eye were also analyzed. Pre- and posttreatment tests of visual acuity, fixation stability, and PRL location in both the treated and the untreated eyes were performed on 13 patients undergoing three monthly intravitreal injections of ranibizumab in one eye. For the treated eyes there were improvements in VA and fixation stability but no changes in the location of the PRL. No significant changes in any of the three variables were found in the untreated eye. For previously untreated eyes, the improvement in visual acuity after intravitreal ranibizumab injections was accompanied by improvement in fixation stability.

La mise en place de zone rétinienne préférentielle. Partie II : Quand ? Où ? Pourquoi s’installe-t-elle ?

The mechanisms underlying the localization of the preferred retinal locus (PRL) for visually impaired people has brought raised a number of hypotheses. In Part 1 we dissociated localizing the PRL from reading and writing tasks. Part 2 presents new hypotheses. and methods: This study was conducted on 100 partially sighted people consulting at our low-vision rehabilitation center. The technique used compares angiofluorographies with images recorded with the scanning laser ophthalmoscope during fixation tasks. It localizes the PRL with respect to the fovea. The PRL position was related to the size of the scotoma and the patient's visual damage. When there was only slight damage, the PRL was located on the left side or possibly in the superior position. When it worsened, the right position was significantly dominant; when it was severe, the PRL was generally located in the superior position or on the right. These positions were nearly always available for a given person. The new visual message must be integrated into the most suitable cerebral locations for low spatial frequencies, damaged forms, messages transmitted by retinal rods, and finally global visual perception. It must favor the peri-personal space and near vision. These elements correspond to the new visual surroundings of the visually impaired. We believe that these data are better processed if they are transmitted by the lower and left visual fields. The rehabilitation program must take into account the above considerations. If the vision therapist orients the PRL location using eccentric view training or by having the patient wear a prism, he must keep in mind that the partially sighted's activities of daily life are the most important. At first, the superior side position, which leaves the field open to a maximum of visual tasks, must be trained, followed by the right position. Of course, when this localization has already been achieved, it must be respected.

Can retinal eccentricity predict visual acuity and contrast sensitivity at the PRL in AMD patients?

Most patients with age-related macular degeneration (AMD) and bilateral central scotomas adopt a preferred retinal locus (PRL) for eccentric viewing. It is postulated that the optimal PRL position is inferior visual space as it provides a larger uninterrupted visual span for reading and mobility. However, the majority of patients place their PRL to the left of their scotoma in visual field space. The purpose of this study was to investigate which factors determine PRL location and specifically, whether the PRL develops in the area of peripheral retina with best visual acuity (VA) and contrast sensitivity (CS). 24 patients were recruited. They were tested on a scanning laser ophthalmoscope to identify the PRL in their better eye. An eyetracker was used to assess peripheral VA and CS. In 19 patients, the PRL was located near the area of best VA. In only 11 patients, the PRL was located near the area of best CS. Patients had worse VA and CS at their PRLs compared to normal vision subjects. VA was best near the PRL, but this was not the case for CS. We cannot distinguish whether the PRL develops at the area of best VA or if it improves at the PRL through practice.

Preferred Retinal Locus Development in Patients with Macular Disease

To observe the development of the preferred retinal locus (PRL) in a group of patients with central scotomas caused by recent onset macular disease (MD). Prospective observational case series. Twenty-five individuals with bilateral central scotomas caused by MD. All patients had experienced visual loss in their better eye in the 2 weeks before recruitment. Patients were assessed at baseline and at 4 further visits for up to 12 months. At each visit, the retinal area used for fixation was assessed using a scanning laser ophthalmoscope, the infrared Gazetracker was used to determine the number of discrete retinal areas used for fixation in 5 positions of gaze, and reading speed was measured using MN-Read-style sentences. All 25 patients developed a PRL within 6 months. Sixteen patients (64%) made an adaptation whereby they were unaware of using an eccentric retinal area for fixation. Multiple fixation loci were exhibited by 11 patients at the end of the study. Nineteen patients used a consistent number of PRLs under all positions of gaze. Reading speed was not associated with PRL location or the presence of multiple PRLs. All of the patients in this study developed a repeatable preferred retinal locus within 6 months of visual loss in their second affected eye. Reading performance was better in patients who were not aware of using eccentric viewing strategies and who used a repeatable number of PRLs under all positions of gaze. These findings are relevant for counseling patients with MD and for the design of rehabilitation programs for patients with central vision loss.

Preferred retinal locus and reading rate with four dynamic text presentation formats.

Electronic display devices hold the potential to improve access to written material by people with low vision. For those with central field loss, the optimal form of electronic text presentation may vary according to the location of the preferred retinal locus, but this has never been investigated. In this study, we examined the relationship between preferred retinal locus location and reading rate for four electronic display formats (rapid serial visual presentation, horizontal scroll, vertical scroll, and page). Short sentences were presented in each format to 35 low-vision (most with central field loss) and 14 age-matched control subjects. Subjects read aloud to determine maximum oral reading rate and read silently to determine preferred silent reading rate. With the exception of page format, maximum oral reading rates were faster than silent preferred reading rates for both groups of subjects. For the low-vision group, there was no significant difference in maximum oral reading rates between the four display formats; and when reading at a preferred silent rate, page format was faster than the other three formats. Though page format was read more quickly, half of the low-vision subjects preferred the horizontal-scroll format. Contrary to our predictions, there was no significant effect of preferred retinal locus location (vertical vs. lateral) on reading rate and no significant interaction between preferred retinal locus location and display format. The differences between maximum oral and preferred silent reading rates and the lack of a relationship between reading rates and preferred display format reinforce the importance of patient preference in the evaluation and selection of a device or display format during rehabilitation.

Preferred Retinal Loci Relationship to Macular Scotomas in a Low-vision Population

The authors identified patterns in preferred retinal locus (PRL) ability and location relative to macular scotomas in a low-vision patient population. Scanning laser ophthalmoscope macular perimetry and PRL testing were performed on 825 patients with low vision. The PRL location was determined, and a PRL scoring system was devised and used to measure the pursuit ability, fixation stability, and saccadic ability of the PRL. The characteristics of dense scotomas within 2.5 degrees of the PRL were noted. Eighty-four percent (1130 of 1339 eyes) of the eyes had an established PRL. Preferred retinal loci varied across the full range of ability scores and varied in size for fixation stability from 1.0 degrees to 9.0 degrees in diameter. There was a central dense scotoma in 82.5% of the eyes, whereas 8.4% had a paracentral dense scotoma. In 14.8% of the eyes, the PRL had no dense scotomas on any of its borders; one, two, three, or four (a ring) borders had a dense scotoma in 39.7%, 19.0%, 9.0%, and 17.4% of eyes, respectively. When the PRL had only one scotomatous border, the resulting field defect was located superior in 39.0%, right in 33.7%, left in 19.9%, and inferior in 7.5% of eyes. The majority of patients with low vision, as many as four of five patients, have dense scotomas encumbering the PRL for visual tasks. Approximately one of six patients with low vision have the PRL completely surrounded by dense scotomas. The visual system shows a strong tendency not to place a PRL anatomically above a scotoma (field defect below fixation) and a weaker tendency not to place the PRL anatomically to the right of a scotoma (field defect to the left of fixation). Macular perimetry and PRL evaluations can provide considerable information on the functional status of the macula, which may be useful to rehabilitation professionals.