Oral and silent reading performance with macular degeneration.

Previous studies have shown that reading rate for very large print (6 degrees, 1.86 logMAR character size) is a strong predictor of oral reading rate with low vision devices (LVDs). We investigated whether this would apply using large print sizes more readily available in clinical situations (e.g. 2 degrees, 1.4 logMAR), for subjects with macular degeneration. We assessed rauding rates--reading for understanding. A combination of near word visual acuity and large print reading rate (without LVDs) provided the best prediction of oral rauding rates (with LVDs). However, near word visual acuity alone was almost as good. Similarly, silent rauding rate was predicted best by near word visual acuity alone. We give near visual acuity limits as a clinical guide to expected oral and silent reading performance with LVDs for patients with macular degeneration.     

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.     

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.     

两种对比度近阅读视力卡的研制和应用

目的 介绍对比敏感度近阅读视力卡的设计原理及使用方法。方法 按对数级数设计的视标进行视力检查，用100％和10％对比度的视力卡来检查对比敏感度。结果 和结论通过视力卡检查可评价视力损害程度，并预测在用高度数眼镜或放大镜纠正以及更好地控制眩光乖照明的情况下视功能的改善情况。对比敏感度文字阅读测试能快速检测出高对比度视力接近正常的患者有可能同时存在低对比度视力的损害，提示是否需要进行白内障手术或其他治疗。     

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 reading speed of adolescent with low vision used electronic visual aids

PURPOSE:To evaluate the reading speed of adolescents with different causes of low vision using electronic visual aids. METHODS:The screening of 10 young students from Quanzhou Blind School could read Chinese N5 print by different optical aids. After their refractive correction and ophthalmic examination, the reading speeds with Chinese N5 print were measured using various optical and electronic visual aids. RESULTS:The reading speed of (34.36±5.06) word / min by electronic visual aids performed faster than that of (18.50±6.54) word / min by optical visual aids in 10 young students with low vision (P<0.05). The reading speed of young people with low vision due to different causes had no direct linear correlation with their near visual acuity（P>0.05）. CONCLUSION:The electronic visual aids more significantly improve the reading speed of young people with low vision than the optical visual aids did. The reading speed of young people with low vision is not relevant to their near visual acuity induced by different causes.     

Illumination and reading performance in age‐related macular degeneration

Background: Previous studies have compared low vision reading performance at optimal task illuminance and consulting room illuminance (500 to 600 lux). However, it is uncertain the extent to which low vision reading performance can be improved when task illumination is increased from levels more representative of those found in the typical living room (50 lux) to levels likely to maximise performance. Methods: Reading performance of 20 subjects with age‐related macular degeneration (AMD) was assessed for a range of print sizes using sentence reading charts at six levels of task illuminance (50 to 5,000 lux). Subjects read without low vision devices. Results: Sentence reading acuity and critical print size improved by a factor of two over the 50 to 5,000 lux range, while maximum reading rate improved by a factor of 1.4. For the majority of subjects (70 per cent), the optimal task illuminance (determined objectively) was higher (median 3,500 lux) than the subjectively preferred task illuminance (median 2,450 lux). Reading performance was significantly better at the optimal illuminance than at illuminances equivalent to those found in the domestic environment (50 lux) or consulting room (600 lux). Conclusions: The majority of AMD patients will require task illumination of at least 2,000 lux to maximise reading performance. Optimal illumination should be determined individually for each patient using both objective measures of performance, such as reading acuity, and subjective assessments of visual comfort.     

The Glenn A. Fry Award Lecture 2003: Vision in elders--summary of findings of the SKI study.

PURPOSE: To assess a broad range of vision functions in a large older population, to investigate the impact of vision function loss on visual performance measures, and to determine whether low contrast vision measures can predict future loss of visual acuity. METHODS: A large battery of vision functions, including spatial vision measures, glare tests, visual fields, stereopsis, color vision, temporal sensitivity, reading performance, and face recognition, was administered to a population of 900 community-living older observers (mean age, 75.5 years; SD, 9.3 years; range, 58 to 102 years). A subsample (N = 596) was retested on average 4.4 years later (SD, 1.0 years). RESULTS: Each vision function is affected differentially by aging. Some functions show little change with age (e.g., standard clinically measured high contrast visual acuity), whereas others demonstrate drastic losses with increasing age. For the oldest age group (>90 years), vision function losses ranged from 1.2 times worse than young observers (critical flicker/fusion frequency) to 18 times worse than young observers (low contrast acuity in glare). Visual performance measures, such as reading or face recognition, are also significantly affected by aging even in those with intact visual acuity. The results demonstrate that low contrast vision functions can successfully predict subsequent loss of high contrast visual acuity. CONCLUSION: Nonstandard vision function measures show significant losses with age that cannot be predicted by standard clinical measures. Measures of low contrast vision function allow clinicians to identify and monitor those patients at high risk for future vision loss.     

The effect of print size on reading rate for adults and children

Print size is one of the numerous factors affecting reading rate. The purpose of this study was to investigate the print sizes which give maximum reading rates for adults and children. Using a forced scrolling technique to move the reading material and a constant field size of 15 characters, a print size of 0.5 logh4AR (N8 at 320 mm) produced maximum reading rate for children in Year 3 at school and for adults. These findings suggest that provided visual acuity is normal, there is no reason for Year 3 children to need larger print than that normally read by adults.     

Reading performance in patients with retinitis pigmentosa: a study using the MNREAD charts

PURPOSE: To evaluate the relationship between reading performance and severity of disease in patients with retinitis pigmentosa (RP), assessed with routine clinical psychophysical visual tests. METHODS: Seventy-six consecutive patients with RP (145 eyes), with reading acuity of at least 1.6 logMAR (logarithm of the minimum angle of resolution) in at least one eye, were examined. Each patient underwent a complete ophthalmic evaluation, including visual acuity (Early Treatment Diabetic Retinopathy Study [ETDRS] charts), contrast sensitivity (Pelli-Robson charts), visual field perimetry (Humphrey central 30-2 full-threshold program; Carl Zeiss Meditec, Dublin, CA), and a test of reading acuity, critical print size, and maximum reading speed (Minnesota Reading charts [MNREAD]). RESULTS: Reading acuity was 1.0 logMAR or more in the better eye of all but six (92%) patients. Maximum reading speed was better than 100 words per minute in the better eye of 59 (78%) subjects. Moderate to severe reading impairment, defined as reading acuity of 0.4 logMAR or worse, was observed in the better eye of 47 (62%) patients. EDTRS visual acuity of 0.3 logMAR (20/40) or worse was 89% sensitive and 66% specific when used as a criterion to define reading impairment. Contrast sensitivity and visual acuity correlated significantly with all three reading components, whereas mean light sensitivity in the central visual field (6 degrees ) demonstrated a higher correlation with maximum reading speed. The number of years elapsed since the diagnosis of RP was a strong negative predictor of reading performance when clinical visual tests were taken into account, whereas a better reading ability characterized the patients with RP who had a higher level of education. A reduced reading speed with larger print size was found in 30 eyes (21%). This correlated with central light sensitivity, as it was more common among eyes with a mean sensitivity of <10 dB. CONCLUSIONS: The reading performance of most patients with RP is only moderately impaired. It correlates with contrast sensitivity, visual acuity, and visual field. It should be assessed in all cases, as disability can ensue, even when visual acuity is preserved. In patients with RP with poor reading performance, there is little potential for high-magnification devices because visual field constriction affects the reading rate.     

Macular degeneration: do conventional measurements of impaired visual function equate with visual disability?

AIMS: To examine the relation between measures of vision and ability to perform daily living tasks in those visually impaired with macular degeneration. METHODS: A visual functioning index (daily living tasks dependent on vision: DLTV) was used to evaluate patients' perception of their ability to perform vision dependent tasks. Distance visual acuity, near visual acuity, reading speed, and contrast sensitivity were measured in all patients. In addition, a new measure of reading ability was derived, designated the reading index. This takes into account both the size of the text read and the time to read it and is equivalent to the reading speed in words per minute divided by text size in M. RESULTS: The reading index was found to show best associations with the majority of items within the DLTV. Stepwise regression identified the combination of reading index and distance visual acuity as having the best associations with DLTV items. The present study also demonstrated that specific levels of vision as measured by acuity, reading index, and contrast sensitivity corresponded with different perceived amounts of difficulty in the performance of daily living tasks. CONCLUSIONS: This study showed that reading index is valuable in predicting the ability to perform daily living tasks and therefore may be useful in the visual assessment of the visually impaired individual. In addition, this study identified specific levels of vision at which individuals reported different degrees of difficulty in performing daily living tasks.     

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.     

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.     

Low contrast vision function predicts subsequent acuity loss in an aged population: the SKI study

Can vision tests predict subsequent loss of acuity? The association between performance on several low contrast spatial vision measures, glare recovery, color discrimination, flicker sensitivity, stereopsis and ocular disease status at baseline and acuity loss 4.4 years later was examined in a large aged random sample with good initial acuity. In univariate analyses, several vision measures, retinal disease status and age were each significant predictors of subsequent acuity loss. In a multiple regression analysis, only low contrast spatial vision was a significant predictor, but the other vision measures, retinal disease status and age were not. For each doubling of low contrast spatial vision threshold at baseline, individuals were more than two times as likely to suffer subsequent significant visual acuity loss. Tests of low contrast spatial vision are strong predictors of significant subsequent visual acuity loss. These findings have implications for clinical trials, clinical management, and acceptance of these measures into clinical practice.     

The effect of relative distance enlargement on visual acuity in the visually impaired

Background : Prescribing magnification is typically based on distance or near visual acuity. This presumes a constant minimum angle of visual resolution with working distance and therefore enlargement of an object moved to a shorter working distance (relative distance enlargement). This study examines this premise in a visually impaired population. Methods : Distance letter visual acuity was measured prospectively for 380 low vision patients (distance visual acuity between 0.3 and 2.1 logMAR) over the age of 57 years, along with near word visual acuity at an appropriate distance for near lens additions from +4 D to +20 D. Demographic information, the disease causing low vision, contrast sensitivity, visual field and psychological status were also recorded. Results : Distance letter acuity was significantly related to (r = 0.84) but on average 0.1 ' 0.2 logMAR better (1 ' 2 lines on a logMAR chart) than near word acuity at 25 cm with a +4 D lens addition. In 39.8 per cent of patients, near word acuity was more than 0.1 logMAR worse than distance letter acuity. In 11.0 per cent of subjects, near visual acuity was more than 0.1 logMAR better than distance letter acuity. The group with near word acuity worse than distance letter acuity also had lower contrast sensitivity. The group with near word acuity better than distance letter aculty was less likely to have age‐related macular degeneration. Smaller print size could be read by reducing working distance (achieved by using higher near lens additions) in 86.1 per cent, although not by as much as predicted by geometric progression in 14.5 per cent. Discussion : Although distance letter and near word acuity are highly related, they are on average 1 logMAR line different and this varies significantly between individuals. Near word acuity did not increase linearly with relative distance enlargement in approximately one in seven visually impaired, suggesting that the measurement of visual resolution over a range of working distances will assist appropriate prescribing of magnification aids.     

Long term functional and structural outcomes of laser therapy for retinopathy of prematurity

AIMS: To assess the long term functional and structural outcomes of premature babies who received diode laser photocoagulation for threshold retinopathy of prematurity (ROP). METHODS: 25 patients (43 eyes) treated with laser were recalled for assessment at a mean follow up of 11 years. A further seven patients (14 eyes) with subthreshold ROP, which had regressed spontaneously without laser treatment, were also examined. All children underwent distance acuity, near acuity, contrast sensitivity (CS), and colour vision assessments followed by a dilated fundal examination and cycloplegic autorefraction. RESULTS: The laser treated eyes had a mean distance visual acuity of 0.37 logMAR, a mean near visual acuity of 0.39 logMAR, a mean contrast sensitivity of 1.49 log CS units, and a mean spherical equivalent of -2.10D. An unfavourable distance visual acuity outcome occurred in five eyes (13.5%). An unfavourable near visual acuity outcome was also noted in the five eyes (13.5%) with poor distance visual outcome. 7% had an unfavourable structural outcome. On comparison with the control group, there was no significant difference in near acuity, CS, refraction, or colour vision between the two groups. However, there was a statistically significant difference in terms of distance visual acuity (p = 0.03). CONCLUSIONS: Laser treated eyes with favourable structural outcome have a good visual outcome. The results show a long term benefit from diode laser photocoagulation in preserving distance and near vision in eyes with threshold ROP.     

Relationship between vision impairment and ability to perform activities of daily living.

PURPOSE: To determine the relationship between clinical measures of vision impairment and the ability to perform activities of daily living (ADLs). METHODS: One hundred and twenty subjects with low vision from a variety of causes participated in the study. Vision impairment was assessed under binocular conditions by measuring distance visual acuity, near word acuity, Melbourne Edge Test contrast sensitivity, Pelli-Robson Chart contrast sensitivity and visual fields. The ADL performance was assessed using the Melbourne Low Vision ADL Index (MLVAI), which is in part an observed performance assessment of instrumental ADLs and in part a self-report assessment of basic self-care ADLs. RESULTS: All vision measures had a high, statistically significant correlation with MLVAI total score. Near word acuity, had the strongest correlation (r(s) = -0.86, p < 0.001), followed by Melbourne Edge Test contrast sensitivity (r(s) = 0.80, p < 0.001). Visual field had the weakest correlation (r(s) = 0.56, p < 0.001). Together, age, near word acuity, Melbourne Edge Test contrast sensitivity and visual field accounted for 82.2% (adjusted R2, p < 0.001) of the variance in MLVAI total score. All correlations obtained were higher for the observed performance assessment of instrumental ADLs than for the self-report assessment of basic self-care ADLs. CONCLUSIONS: Clinical vision impairment measures are highly correlated with capacity to perform ADLs, as measured by the MLVAI.     

The practical near acuity chart (PNAC) and prediction of visual ability at near.

OBJECTIVE: To improve on present reading chart designs, providing a quick and accurate method to measure the near acuity threshold, of particular importance with low vision patients. DESIGN: The Practical Near Acuity Chart (PNAC) uses a single paragraph with 3 simple related words on each line (12 lower case letters). The line print size decreases in a logMAR progression (N80-N5). METHODS: The time taken to measure near acuity of 53 subjects aged 9-91 years with the PNAC and Bailey-Lovie near chart was recorded and compared to their distance acuity (Bailey-Lovie chart), contrast sensitivity (Melbourne Edge Test) and ability to read extracts of newsprint. RESULTS: There was no difference in near acuity threshold using related or un-related words. There was a high correlation (r = 0.97) between near acuity measured with the PNAC and Bailey-Lovie charts. However, the time taken to measure near acuity was significantly faster with the PNAC (32 +/- 2 s vs 76 +/- 4 s, p < 0.001). Near acuity measured with either chart was highly correlated (p < 0.001) to distance acuity (r = 0.74), contrast sensitivity (r = 0.62) and ability to read newsprint (r = 0.87). The PNAC was shown to have high test-reliable (r = 0.99). CONCLUSIONS: The PNAC offers a quick but accurate way to measure near acuity and shows a high degree of correlation with distance acuity, contrast sensitivity and the ability to read newsprint.     

Low vision aids for reading in scar stage of age-related macular degeneration

PURPOSE: To evaluate the inter-relationship among near visual acuity, eccentricity of preferred retinal locus(PRL), and choice of low vision aids for reading in patients with bilateral age-related macular degeneration(AMD). SUBJECTS AND METHODS: The preferred eye of 44 patients having bilateral disciform stage AMD was examined. The PRL was detected and its eccentricity from the fovea was measured by scanning laser ophthalmoscopic microperimetry. Magnification of a low vision aid for reading newsprint was determined by the critical print size which was calculated using the MNREAD-J. The type of preferred aid was chosen from high-plus lens glasses, magnifiers, and closed-circuit televisions. The inter-relationship among near visual acuity, eccentricity of the PRL, and magnification and type of low vision aid for reading were evaluated. RESULTS: The magnification of the aid was correlated with the eccentricity of PRL in eyes with near visual acuity of 0.2 or less although no correlation was found in eyes with near visual acuity better than 0.3. High plus lens glasses were selected by patients with near visual acuity better than 0.2 and eccentricity of 2 degrees or less. Magnifiers were selected by patients with near visual acuity better than 0.1 and eccentricity of 5 degrees or less. Closed-circuit televisions were selected by patients with near visual acuity of 0.1 or less and eccentricity of 5 degrees or more. CONCLUSION: The eccentricity of PRL should be taken into account in determining low vision aids for reading, especially in patients with near visual acuity of 0.2 or less. Choice of the type of low vision aid depends on not only near visual acuity but also on eccentricity of PRL.     

Repeatability of visual function measures in age-related macular degeneration

Purpose

To assess repeatability of visual function measures in patients with early, intermediate or late age-related macular degeneration (AMD) without active neovascular disease in the study eye, but active neovascular AMD in the fellow eye.

Methods

One hundred subjects from an ongoing trial were screened for this study in which their LogMAR acuity, contrast sensitivity and reading performance were assessed using standardised protocols by trained optometrists. The same measures were repeated one month later and repeatability of the visual functions assessed.

Results

Data from 83 subjects satisfied inclusion criteria for analysis. Coefficient of repeatability was 14.9 letters for LogMAR visual acuity , 7.2 letters for Pelli Robson contrast sensitivity, 0.72 for LogMAR reading acuity, 110.4 words/ min for reading speed and 0.67 for LogMAR critical print size. Intraclass correlation coefficients allowed comparison between measures and were found to be 0.96 for LogMAR visual acuity, 0.93 for contrast sensitivity, 0.75 for LogMAR reading acuity, 0.79 for reading speed and 0.74 for LogMAR critical print size. Coefficients of variation were 9.4 %, 10.7 %, 48.4 %, 28.4 % and 31.8 % respectively.

Conclusions

We found coefficients of repeatability that concurred with previous studies demonstrating variability of visual functions in patients with AMD. In addition, we found intraclass correlation coefficients to be better with visual acuity and contrast sensitivity than with measures of reading performance.