Reading performance with various lamps in age-related macular degeneration

The purpose of this study was to determine if there was an objective difference in reading between four commonly available lamps, of varying spectral radiance, for 13 subjects with age-related maculopathy (ARM) or non-exudative age-related macular degeneration (AMD)--logMAR visual acuity between 0.04 and 0.68. At a constant illuminance of 2000 lux, there was no interaction between ARM and AMD subgroups and no statistically significant difference between the lamps: standard (clear envelope) incandescent, daylight simulation (blue tint envelope) incandescent, compact fluorescent and halogen incandescent, for any reading outcome measure (threshold print size p = 0.67, critical print size p = 0.74, acuity reserve p = 0.84 and mean reading rate p = 0.78). For lamps typically used in low-vision rehabilitation, a clinically significant effect of spectral radiance on reading for people with ARM or non-exudative AMD is unlikely.     

Determining magnification for reading with low vision

Background : In the past, practitioners have used distance and/or near visual acuity (VA) to calculate required magnification for low vision aids. Magnification was usually under‐estimated when compared with the final magnification prescribed. Recent studies have emphasised the importance of acuity reserve in determining the required magnification for optimum reading rate. Two different approaches have been proposed for the appropriate acuity reserve to use in calculating magnification. These are a fixed acuity reserve of 0.3 log unit or an individual determination of optimum acuity reserve. The aim of this study was to investigate the magnification and reading rates with low vision aids selected by the two methods. Methods : Nineteen low vision subjects with age‐related macular degeneration (AMD) who were experienced magnifier‐users were recruited. Reading rates and near VA with low vision aids determined by the fixed and individual acuity reserve methods were compared with the same measures made with the subjects' own magnifiers. Results : There were no significant differences in reading rate and near VA measured with low vision aids selected by either the fixed or individual acuity reserve methods or the subjects' own magnifiers. Reading rate with low vision aids was not significantly different from reading rate for large print with conventional near additions. Thus, for experienced users, magnifiers do not cause reduced reading rate. Conclusions : The fixed acuity reserve method is simple to apply as only near VA and print size of the target reading task are required. For the individual acuity reserve method, reading rates at different print sizes need to be measured. We recommend the use of a fixed acuity reserve (0.3 log unit) for the calculation of required magnification for low vision patients. If near VA or reading rate are not satisfactory with the magnification calculated by this method, individual assessment of required acuity reserve is necessary.     

Effect of light-emitting diode colour temperature on magnifier reading performance of the visually impaired

Background: As light‐emitting diodes become more common as the light source for low vision aids, the effect of illumination colour temperature on magnifier reading performance was investigated. Methods: Reading ability (maximum reading speed, critical print size, threshold near visual acuity) using Radner charts and subjective preference was assessed for 107 participants with visual impairment using three stand magnifiers with light emitting diode illumination colour temperatures of 2,700 K, 4,500 K and 6,000 K. The results were compared with distance visual acuity, prescribed magnification, age and the primary cause of visual impairment. Results: Reading speed, critical print size and near visual acuity were unaffected by illumination colour temperature (p > 0.05). Reading metrics decreased with worsening acuity and higher levels of prescribed magnification but acuity was unaffected by age. Each colour temperature was preferred and disliked by a similar number of patients and was unrelated to distance visual acuity, prescribed magnification and age (p > 0.05). Patients had better near acuity (p = 0.002), critical print size (p = 0.034) and maximum reading speed (p < 0.001), and the improvement in near from distance acuity was greater (p = 0.004) with their preferred rather than least‐liked colour temperature illumination. Conclusion: A range of colour temperature illuminations should be offered to all visually impaired individuals prescribed with an optical magnifier for near tasks to optimise subjective and objective benefits.     

The Role of Eye Movements During Reading in Patients with Age-Related Macular Degeneration (AMD)

AMD patients often have particular difficulty reading, even when the text is magnified to compensate for reduced visual acuity. This study explores whether reading performance can be explained by eye movement factors. Forty patients with advanced AMD were tested with a high-speed video eye tracker to evaluate fixation stability and saccadic eye movements. Reading speed was measured for standardized texts viewed at the critical print size. Visual acuity and contrast sensitivity were unrelated to reading speed, but fixation stability, proportion of regressive saccades and size of forward saccades were all significantly associated with reading performance, accounting for 74% of the variance. The implications of these findings for low-vision training programmes are discussed.     

Reading performance in the scar stage of age-related macular degeneration

PURPOSE: To evaluate reading performance in patients with age-related macular degeneration (AMD). SUBJECTS AND METHODS: Six normal subjects over 50 years of age and 40 patients with AMD were evaluated. Near visual acuity, critical print size, and maximum reading speed were tested to compare the data from normal subjects with those from AMD patients. Scanning laser ophthalmoscope (SLO) microperimetry was performed to observe fixation in AMD patients. RESULTS: The mean critical print size for normal subjects was 0.15 logarithm of the minimum angle of resolution (log MAR) and the mean maximum reading speed was 307 characters/min. There was a plateau area in reading function where reading speed did not rise and stayed constant even though print size increased. The mean critical print size for AMD patients was 0.97 log MAR, and the mean maximum reading speed was 140 characters/min. The critical print size and maximum reading speed differed significantly between normal and AMD subjects. Eleven of the 40 patients with AMD did not have the character size and reading speed relationship, which means they manifested a plateau as seen in normal subjects. Eight of the 11 patients did not show stable fixation with SLO microperimetry. CONCLUSIONS: The reading performance of AMD patients was remarkably impaired, especially in those with poorer visual function and no fixation.     

The effect of dioptric blur on reading performance

Little is known about the systematic impact of blur on reading performance. The purpose of this study was to quantify the effect of dioptric blur on reading performance in a group of normally sighted young adults. We measured monocular reading performance and visual acuity for 19 observers with normal vision, for five levels of optical blur (no-blur, 0.5, 1, 2, and 3D). Dioptric blur was induced using convex trial lenses placed in front of the testing eye, with the pupil dilated and in the presence of a 3 mm artificial pupil. Reading performance was assessed using eight versions of the MNREAD Acuity Chart. For each level of dioptric blur, observers read aloud sentences on one of these charts, from large to small print. Reading time for each sentence and the number of errors made were recorded and converted to reading speed in words per minute. Visual acuity was measured using 4-orientation Landolt C stimuli. For all levels of dioptric blur, reading speed increased with print size up to a certain print size and then remained constant at the maximum reading speed. By fitting nonlinear mixed-effects models, we found that the maximum reading speed was minimally affected by blur up to 2D, but was ∼23% slower for 3D of blur. When the amount of blur increased from 0 (no-blur) to 3D, the threshold print size (print size corresponded to 80% of the maximum reading speed) increased from 0.01 to 0.88 logMAR, reading acuity worsened from −0.16 to 0.58 logMAR, and visual acuity worsened from −0.19 to 0.64 logMAR. The similar rates of change with blur for threshold print size, reading acuity and visual acuity implicates that visual acuity is a good predictor of threshold print size and reading acuity. Like visual acuity, reading performance is susceptible to the degrading effect of optical blur. For increasing amount of blur, larger print sizes are required to attain the maximum reading speed.     

Benefits of electronic vision enhancement systems (EVES) for the visually impaired

PURPOSE: To examine whether objective performance of near tasks is improved with various electronic vision enhancement systems (EVES) compared with the subject's own optical magnifier. DESIGN: Experimental study, randomized, within-patient design. METHODS: This was a prospective study, conducted in a hospital ophthalmology low-vision clinic. The patient population comprised 70 sequential visually impaired subjects. The magnifying devices examined were: patient's optimum optical magnifier; magnification and field-of-view matched mouse EVES with monitor or head-mounted display (HMD) viewing; and stand EVES with monitor viewing. The tasks performed were: reading speed and acuity; time taken to track from one column of print to the next; follow a route map, and locate a specific feature; and identification of specific information from a medicine label. RESULTS: Mouse EVES with HMD viewing caused lower reading speeds than stand EVES with monitor viewing (F = 38.7, P <.001). Reading with the optical magnifier was slower than with the mouse or stand EVES with monitor viewing at smaller print sizes (P <.05). The column location task was faster with the optical magnifier than with any of the EVES (F = 10.3, P <.001). The map tracking and medicine label identification task was slower with the mouse EVES with HMD viewing than with the other magnifiers (P <.01). Previous EVES experience had no effect on task performance (P >.05), but subjects with previous optical magnifier experience were significantly slower at performing the medicine label identification task with all of the EVES (P <.05). CONCLUSIONS: Although EVES provide objective benefits to the visually impaired in reading speed and acuity, together with some specific near tasks, some can be performed just as fast using optical magnification.     

Optimal illumination for reading in patients with age-related maculopathy.

This study was designed to determine optimal levels of illumination for reading for patients with age-related maculopathy. These patients comprise a large percentage of the low vision population, and illumination has a great impact on their reading ability. For many patients in this study, increased illumination levels improved their performance. Eleven of the 18 patients preferred illumination levels as high as 5920 to 7534 lux (550 to 770 ft-c). This information suggests that illumination levels higher than previously recommended will improve reading speed in most patients with age-related macular degeneration (ARMD).     

Reading performance in children with low vision

Purpose: While educators and optometrists are concerned with reading efficiency in children with low vision, in most low vision assessments, children's reading performance is assessed only by a brief evaluation of reading fluency. We examined the relationships between clinical vision measures and reading performance in children with low vision. Methods: Subjects were 71 students with low vision, aged seven to 18 years. The vision and reading performance measures were: high contrast distance visual acuity, contrast sensitivity using both the Pelli‐Robson and LH symbol charts, near text visual acuity and reading rates on a range of print sizes. Results: Most children achieved maximum reading rate at print sizes between 2.5 and seven times larger than threshold print size. Maximum reading rate increased significantly with age and near visual acuity. There was no significant relationship between reading rate and contrast sensitivity. Conclusions: The majority of children with low vision can achieve near normal reading rates with magnification. Age is the strongest predictor of reading rate in children with low vision. They need print sizes well above threshold to achieve maximum reading rate. Routine contrast sensitivity testing of visually impaired students is not indicated for reading assessment.     

Visual function and subjective quality of life compared in subjects with acquired macular disease

PURPOSE: To determine the objective measures of visual function that are most relevant to subjective quality of vision and perceived reading ability in patients with acquired macular disease. METHODS: Twenty-eight patients with macular disease underwent a comprehensive assessment of visual function. The patients also completed a vision-related quality-of-life questionnaire that included a section of general questions about perceived visual performance and a section with specific questions on reading. RESULTS: Results of all tests of vision correlated highly with reported vision-related quality-of-life impairment. Low-contrast tests explained most of the variance in self-reported problems with reading. Text-reading speed correlated highly with overall concern about vision. CONCLUSIONS: Reading performance is strongly associated with vision-related quality of life. High-contrast distance acuity is not the only relevant measure of visual function in relation to the perceived visual performance of a patient with macular disease. The results suggest the importance of print contrast, even over print size, in reading performance in patients with acquired macular disease.     

Face recognition in age related macular degeneration: perceived disability,measured disability,and performance with a bioptic device

AIMS: (1) To explore the relation between performance on tasks of familiar face recognition (FFR) and face expression difference discrimination (FED) with both perceived disability in face recognition and clinical measures of visual function in subjects with age related macular degeneration (AMD). (2) To quantify the gain in performance for face recognition tasks when subjects use a bioptic telescopic low vision device. METHODS: 30 subjects with AMD (age range 66-90 years; visual acuity 0.4-1.4 logMAR) were recruited for the study. Perceived (self rated) disability in face recognition was assessed by an eight item questionnaire covering a range of issues relating to face recognition. Visual functions measured were distance visual acuity (ETDRS logMAR charts), continuous text reading acuity (MNRead charts), contrast sensitivity (Pelli-Robson chart), and colour vision (large panel D-15). In the FFR task, images of famous people had to be identified. FED was assessed by a forced choice test where subjects had to decide which one of four images showed a different facial expression. These tasks were repeated with subjects using a bioptic device. RESULTS: Overall perceived disability in face recognition did not correlate with performance on either task, although a specific item on difficulty recognising familiar faces did correlate with FFR (r = 0.49, p<0.05). FFR performance was most closely related to distance acuity (r = -0.69, p<0.001), while FED performance was most closely related to continuous text reading acuity (r = -0.79, p<0.001). In multiple regression, neither contrast sensitivity nor colour vision significantly increased the explained variance. When using a bioptic telescope, FFR performance improved in 86% of subjects (median gain = 49%; p<0.001), while FED performance increased in 79% of subjects (median gain = 50%; p<0.01). CONCLUSION: Distance and reading visual acuity are closely associated with measured task performance in FFR and FED. A bioptic low vision device can offer a significant improvement in performance for face recognition tasks, and may be useful in reducing the handicap associated with this disability. There is, however, little evidence for a correlation between self rated difficulty in face recognition and measured performance for either task. Further work is needed to explore the complex relation between the perception of disability and measured performance.     

Reading with central scotomas: is there a binocular gain?

PURPOSE: The purpose of this study was to compare reading performance under binocular versus monocular viewing conditions in patients with bilateral age-related macular degeneration (AMD). METHODS: Twenty-two patients with AMD participated. Distance acuity, reading acuity, and contrast sensitivity were recorded binocularly and monocularly with the better eye. An infrared eye tracker recorded eye movements during reading. Reading speed and reading eye movement parameters, including number of fixations and regressions, fixation duration, and number of saccades to find the next line, were calculated for both viewing conditions. The difference between binocular and monocular performance (binocular gain) was computed. Regression analysis was used to determine whether intraocular differences in distance and reading acuity and contrast sensitivity were predictive of binocular gain. RESULTS: Reading speed when using both eyes was highly correlated with the reading speed for the better eye. There was a small, but not significant, advantage of binocular viewing (6.9 words/minute, p = 0.33). No significant difference was detected in any eye movement parameters when comparing both eyes with the better eye. Although some patients showed either positive or negative binocular gain, the amount of gain was not predicted by intraocular differences in acuity or contrast sensitivity. CONCLUSIONS: Overall, there was no significant difference between binocular and monocular reading performance in patients with AMD.     

Reliability testing of the Dutch version of the Radner Reading Charts.

PURPOSE: To statistically analyze the test-retest and inter-chart reliability of the newly developed actual logarithmically scaled Dutch Radner Reading Charts in an older population affected by macular disease. These Dutch Radner Reading Charts are developed according to the strict principles of sentence construction of the originally German language Radner Reading Charts. METHODS: Thirty-six subjects aged 50 years or older and affected with a macular disease monocularly read the three charts of the Radner Reading Charts in a randomized order twice with 1 month in between. The subjects were divided into three groups according to their distance logMAR visual acuity (group 1, > or =0.1; group 2, 0.12 to 0.4; and group 3, 0.42 to 0.8). Reading acuity (logRAD, the reading equivalent of logMAR), logRAD score, maximum reading speed, critical print size, and logRAD/logMAR ratio were measured. Variance component analysis was used to determine the sources of variability. RESULTS: The test-retest and inter-chart reliability was high for all visual acuity groups and variables. For all groups together the chart accounted for maximal 5% of the total variability for all measurements. The individual subject did have the largest influence on the measurements (88 to 98% of the variability). CONCLUSIONS: The Dutch version of the Radner Reading Charts provided high reliable test-retest and inter-chart measurements of reading performance in a heterogeneous group of subjects with subnormal to low vision. This study also showed that the strict principles of sentence construction of the originally German Radner Reading Charts may also be successfully used for other languages.     

Optimal reading speed in simulated cataract: development of a potential vision test

Previous studies suggest that optimal reading speed is unaffected by cataract, yet is significantly reduced in age-related macular disease. This raises the question of whether a reading speed test could be developed to assess potential vision after cataract surgery. In this study, 20 young subjects, with and without a simulation of dense cataract, read aloud Bailey-Lovie word charts. From the results, critical print size, optimal reading speed and word acuity were calculated. The simulated cataract reduced word acuity and increased the critical print size, yet optimal reading speed remained unchanged. Measurements were also taken with the charts in reversed contrast polarity. Reversing the contrast polarity of the charts improved the word acuity and optimal reading speed with the cataract simulation. The results suggest that optimal reading speed could be used as a potential vision test. Further investigations using patients with cataract and ARMD are required.     

Reading with a head-mounted video magnifier.

PURPOSE: This study compared the effectiveness of a head-mounted video magnifier, low-vision enhancement system (LVES), with closed-circuit TV (CCTV) and large print as a device or means of improving reading performance in people with low vision. METHODS: The reading performance of ten low-vision participants was assessed in two ways: (1) By measuring reading speed as a function of print size with LVES and without LVES, and (2) by comparing reading speed and comprehension of news articles using the LVES vs. a popular non-head-mounted video magnifier, the CCTV. RESULTS: Maximum reading speeds with LVES matched the maximum reading speeds with unaided vision attained by enlarging print. The critical print size (the smallest print size that could be read at maximum reading speed) improved significantly for all participants using LVES compared with unaided vision. When comparing reading performance using LVES and CCTV, we found that reading speed and comprehension for the two conditions were equivalent. The two low-vision participants with lowest acuities (20/640 and 20/960) could not read the 10-point newspaper articles with LVES, even with an 8 D auxiliary reading lens that permitted a very close reading distance. CONCLUSIONS: Head-mounted video magnifiers, such as LVES, can support good low-vision reading performance, but the restricted range of magnification may limit the usefulness of the device as a reading magnifier for people with very low acuity.     

老年黄斑变性低视力患者的视觉康复

应用光学助视器,对14例(25眼)老年黄斑变性低视力患者作了视觉康复.经用远用助视器,25眼中的24眼(95%)远视力有改善,其中12眼(48%)远视力≥0.4;经用近用助视器,全部眼(100%)的近视力有改善,13眼(52%)近视力达≥0.5,10例患者可阅读5号中文印刷体,阅读成功率达71.4%.结果表明助视器的应用对改善老年黄斑变性低视力患者的远、近视力是一种有效方法.     

Reading ability after photodynamic therapy (PDT) for age-related macular degeneration (AMD) and for high myopia

BACKGROUND: A prospective uncontrolled follow-up of changes in reading ability after PDT with Verteporfin in patients with predominantly classic subfoveal choroidal neovascularization (CNV) due to AMD or high myopia was carried out. PATIENTS AND METHODS: A follow-up time of at least 6 months is documented for 48 patients with AMD and for 22 patients with high myopia. In addition to the usual clinical parameters the need for magnification was measured using standardized reading charts provided by the SZB.A need for magnification higher than 3.2-fold was defined as a severe loss in reading ability.PDT's were repeated every 3 months according to the usual guidelines. RESULTS: Before treatment, the mean reading acuity for patients with AMD was between 20/200 and 20/100.The average need for magnification was between 2.5-fold and 3.2-fold.Reading acuity, need for magnification and the percentage of patients with a need for magnification of 3.2-fold or less remained stable over a 6-12 months follow-up period.High myopic patients initially had a mean reading acuity of 20/200 and a need for magnification of 2.5-fold.After 9 months follow-up, reading acuity showed a mean improvement from 0.2 up to 0.3 ( p<0.05). There was also a trend towards improvement in the need for magnification and the percentage of patients with a need for magnification of 3.2-fold or less improved significantly from 68% to 78% ( p<0.05). CONCLUSION: Reading ability could be stabilized with PDT for predominantly classic subfoveal CNV in patients with high myopia or AMD for at least 9-12 months.The risk of developing a severe loss in reading ability (need for magnification >3.2-fold) was significantly reduced in high myopia and was stable over time in AMD.     

The impact of light source on discrimination ability in subjects with age‐related macular degeneration

Purpose: To examine the influence of light source on letter contrast sensitivity in subjects with age‐related macular degeneration (AMD). Methods: Halogen incandescent bulbs and low‐energy fluorescent tubes were tested with 70 subjects with AMD. The subjects’ contrast sensitivity was determined in a randomized single‐blind crossover study for each light source using photopically illuminated Pelli Robson contrast sensitivity charts. The test subjects’ subjective light source preference was also determined. Results: The mean contrast sensitivity for the incandescent light source was 1.28 ± 0.29 (mean ± SD), and for the fluorescent light source 1.17 ± 0.29, p < 0.001. The illuminance was 338 lux (±9) for the incandescent light, and 339 lux (±11) for the fluorescent light. Forty‐nine subjects preferred the incandescent light source, while none preferred the fluorescent light source for maximum detail and clarity. Nineteen had no preference. This finding is statistically significant. Fifteen of the 19 subjects without a preference had no difference in contrast sensitivity, which supports their lack of preference. There was no significant difference with regard to sex or order of exposure to light source. Subjects with AMD had significantly reduced contrast sensitivity compared with expected normal values. We found no relationship between visual acuity and contrast sensitivity. Conclusion: We are only able to recommend photopic full spectral radiance incandescent light sources to visually impaired subjects for their domestic surroundings. Furthermore, we recommend the use of full spectral radiance light sources for the illumination of Pelli‐Robson contrast sensitivity charts. Given equal illuminance, as in our study, the findings show that contrast sensitivity was better by illumination with incandescent light with full spectral radiance compared with fluorescent light with interrupted spectral radiance.     

Assessment of age‐related maculopathy using subjective vision tests

This paper reviews non‐standard, clinical vision tests that may be used to detect the earliest visual loss in age‐related maculopathy (ARM), before fundus changes are detected. We recommend a clinical test battery for all patients aged 60 years and older, comprising low luminance/low contrast (SKILL) VA or low contrast VA, desaturated D‐15 colour vision assessment, flicker perimetry, glare recovery and dark adaptation if possible, together with conventional assessments of case history, ophthalmoscopy and high contrast visual acuity (VA) for the detection and diagnosis of ARM. Reading rate is also discussed as a potential indicator of early visual loss. For monitoring the progressive visual loss in age‐related macular degeneration (AMD) and determining the requirements for optometric vision rehabilitation, we recommend more conventional clinical vision tests of distance and near visual acuity, reading rate, the effects of varying illumination and a functional central visual field assessment.