Users' subjective evaluation of electronic vision enhancement systems.

The aims of this study were (1) to elicit the users' responses to four electronic head-mounted devices (Jordy, Flipperport, Maxport and NuVision) and (2) to correlate users' opinion with performance. Ten patients with early onset macular disease (EOMD) and 10 with age-related macular disease (AMD) used these electronic vision enhancement systems (EVESs) for a variety of visual tasks. A questionnaire designed in-house and a modified VF-14 were used to evaluate the responses. Following initial experience of the devices in the laboratory, every patient took home two of the four devices for 1 week each. Responses were re-evaluated after this period of home loan. No single EVES stood out as the strong preference for all aspects evaluated. In the laboratory-based appraisal, Flipperport typically received the best overall ratings and highest score for image quality and ability to magnify, but after home loan there was no significant difference between devices. Comfort of device, although important, was not predictive of rating once magnification had been taken into account. For actual performance, a threshold effect was seen whereby ratings increased as reading speed improved up to 60 words per minute. Newly diagnosed patients responded most positively to EVESs, but otherwise users' opinion could not be predicted by age, gender, diagnosis or previous CCTV experience. User feedback is essential in our quest to understand the benefits and shortcoming of EVESs. Such information should help guide both prescribing and future development of low vision devices.

Gaze changes with binocular versus monocular viewing in age-related macular degeneration.

PURPOSE: To determine and explain gaze changes during binocular versus monocular viewing in patients with age-related macular degeneration (AMD). DESIGN: Cross-sectional study. PARTICIPANTS: Twenty-nine patients with bilateral late-stage AMD. METHODS: Distance acuity and fundus pathologic features were evaluated. Eye position was recorded while viewing a circular fixation target under monocular and binocular viewing conditions using an infrared eye tracker (SMI Gazetracker, SensoMotoric, Germany; Eyelink Software 2.04). Gaze changes were quantified by calculating the mean x-coordinate and y-coordinate eye position of the center of the bivariate contour ellipse area for a 30-second fixation task under both viewing conditions. Retinal loci used for monocular fixation for each eye were determined using the scanning laser ophthalmoscope (SLO; SLO 101, Rodenstock, Munich, Germany). MAIN OUTCOME MEASURE: Gaze position. RESULTS: Nine patients showed no shift in gaze position from monocular to binocular viewing. Three patients demonstrated a shift in both eyes, and 17 patients demonstrated a shift in only 1 eye. The mean shift was 4.7+/-5 degrees (standard deviation). The shift in gaze position in the worse eye was predictive of the distance between the 2 monocular preferred retinal loci (PRLs; better and worse eye; r(2) = 0.59; P<0.0001), whereas there was no association between the shift in gaze position in the better eye and distance (r(2) = 0.00; P = 0.91). CONCLUSIONS: Most AMD patients shift gaze position in 1 or both eyes when viewing binocularly compared with monocularly. These changes suggest that different retinal locations are used for fixation under the 2 viewing conditions. The SLO data showed that these patients are likely to demonstrate monocular PRLs that fall on noncorresponding areas. These results may have implications for the effective development of eccentric viewing and binocular behavior of AMD patients.

Preferred retinal locus development in patients with macular disease.

OBJECTIVE: 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). DESIGN: Prospective observational case series. PARTICIPANTS: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Predicting reading fluency in patients with macular disease.

PURPOSE: Difficulty in reading is the most frequent complaint of patients with macular disease (MD). This article assesses whether clinical variables measured at the onset of MD can be used to predict patients' future reading ability. METHODS: Twenty-five patients with MD were recruited within 4 weeks of the onset of symptoms in their second affected eye. Clinical and demographic features were recorded at baseline and at the exit point of the study 3 to 12 months later. Odds ratios (OR's) were constructed to assess the predictive value of these variables in terms of reading fluency and any change in reading speed at the exit point of the study. RESULTS: Baseline contrast sensitivity was associated with future fluent reading (OR, 2.40; interval size, 0.15; 95% confidence interval, 1.13 to 5.07). Age, sex, scotoma size, disease type, visual acuity, and reading speed were not statistically significant predictors of future fluent reading. It was not possible to predict fully in which patients reading speed improved or deteriorated. CONCLUSIONS: Contrast sensitivity can predict the likelihood of future fluent reading in patients with MD. Baseline reading speed, visual acuity, age, disease type, and scotoma size are poor predictors of future reading performance.

Clinical performance of electronic, head-mounted, low-vision devices.

This study compared four electronic head-mounted devices (HMDs) (Jordy, Flipperport, Maxport and NuVision) with conventional optical low-vision aids (LVAs). The aim was to determine any performance differences for laboratory-based clinical measurements and practical visual tasks for patients with macular disease. Possible factors influencing success were explored. Ten patients with early onset macular disease (EOMD) and 10 with age-related macular disease (AMD) used the four HMDs, habitual spectacles and previously prescribed optical LVAs to complete a range of clinical measurements and everyday visual tasks. The clinical measurements were distance, intermediate and near acuities, and contrast sensitivity. The visual tasks were to read text of three sizes, to write a cheque and to identify grocery items on a shelf. Following the initial evaluation, each subject took home two randomly selected HMD devices for 2 weeks, after which performance measures were repeated. No single HMD stood out as being superior overall. Flipperport and Jordy provided significantly better distance and intermediate acuity than the previously prescribed optical LVAs but near acuity and contrast sensitivity were not consistently better with any of the HMDs. Practice at home provided some improvement in performance with HMDs, nevertheless, optical aids remained the best devices for optimum functioning for the majority of tasks. Younger patients and those with better distance acuity were more likely to benefit from HMDs, particularly when reading small print. In low vision clinics, practitioners should continue to show patients conventional optical aids and demonstrate these electronic HMDs only when appropriate for the individual patient.

Fixation stability and reading speed in patients with newly developed macular disease.

BACKGROUND: Patients with macular disease and central scotomas must use a peripheral, preferred retinal locus (PRL) in place of their damaged fovea. This paper investigates the development of the PRL, with particular reference to the stability of fixation. METHODS: Twenty-five patients with age-related and juvenile macular disease were recruited. All patients had developed a scotoma in their better eye within the previous 2 weeks. Patients were assessed using a scanning laser ophthalmoscope and an infra-red gazetracker on four further occasions over the next 12 months. RESULTS: A linear relationship exists between reading speed and fixation stability for patients and control subjects. Fixation stability was not related to scotoma size, visual acuity or contrast sensitivity. Changes in fixation stability account for 54% of the variance in change in reading speed over the course of this study. CONCLUSIONS: The deficit in reading speed in patients with macular disease can be partially attributed to impairments in fixation stability.