Effectiveness of Magnifying Low Vision Aids in Patients with Age-Related Macular Degeneration

Abstract

The aim of the study was to evaluate the influence of magnification requirement on the effectiveness of low vision aids in patients with age-related macular degeneration (AMD). 656 AMD-patients underwent careful administration of low vision aids and were trained to read with prescribed visual aids for at least 30 minutes. Main outcome measures were: magnification requirement, prescribed low vision aids, reading speed [words per minute = wpm] before and after providing of low vision aids. Mean magnification requirement (MR) was 8.0 ± 6.2 fold, 257 patients had a MR up to 3-fold (Grade 1), 101 patients between 4 to 6-fold (Grade 2) and in 298 patients MR was more than 6-fold (Grade 3). The visual rehabilitation was sufficient with optical low-vision aids in 54%. In 44.5% electronic closed-circuit TV systems were necessary. Only 1.5% of the patients needed an electronic reading device. For the whole group, reading speed (wpm) was on average 12 ± 25 without and increased significantly up to 71 ± 33 with visual aids. There are significant differences (p < 0.0001) of reading speed in three magnification grades before (Grade 1, Grade 2, Grade 3: 27 ± 33, 7.4 ± 14, 0.3 ± 3.0) and after rehabilitation (95 ± 28, 72 ± 24, 46 ± 20, respectively). Patients with a lower magnification requirement (up to 6-fold) showed a significantly higher increase of reading speed than patients with higher magnification requirement (> 6-fold) (p < 0.0001). These results provide quantitative data concerning the success of rehabilitation for AMD-patients with regard to magnification requirement. This important option should be considered early in order to help patients maintain their reading ability, independence and mental agility.

Keywords:

• age-related macular degeneration
• magnification requirement
• magnifying low vision aids
• rehabilitation
• reading speed

INTRODUCTION

Age-related macular degeneration (AMD) is the leading cause of severe visual impairment in the developed world with a high percentage of older persons over the age of 65.¹, ², ³, ⁴ The World Health Organisation estimated that 14 million persons are visually impaired due to AMD.⁵ Due to the demographic development in most developed countries, it is inevitable that the number of age-related diseases will grow and the incidence of severe visual impairment due to AMD will rise sharply in the coming years.⁶, ⁷

AMD affects the central retina, leading to a progressive loss of central vision and reading ability and often results in an irreversible central scotoma. The loss of reading ability means loss of independence, mental agility and quality of life.⁸, ⁹, ¹⁰, ¹¹ Therefore, the preservation or restoration of reading ability is the primary goal in the care of low vision patients. Reading requires not only sufficient resolution, but also a sufficient size of the reading visual field to cover a group of letters during one fixation.¹², ¹³, ¹⁴, ¹⁵ Patients with central scotoma develop eccentric fixation at the edge of the scotoma, which can enable them to regain the ability to read. However, the resolution of this retinal area is not high enough to read book print at a normal reading distance. Therefore, the text has to be magnified.², ¹⁶, ¹⁷, ¹⁸ The combination of eccentric fixation and magnification is the basis for the effectiveness of magnifying vision aids in these patients.

There is a lively and controversial discussion about various training methods for patients with AMD, especially eccentric viewing training. However, it is of interest to examine the effect of low vision aids alone. We demonstrated in a recent study¹⁹ that reading speed can be significantly improved by optimal low vision aids. In the present study we have examined the influence of magnification requirement on the effectiveness of low vision aids.

PATIENTS AND METHOD

Patients

This study included 656 patients (mean age: 79 ± 9.5 years, range 52–98 years) with different stages of AMD, who were referred to our Low Vision Clinic between January 2005 and June 2008 to receive or update their first low vision aid, because the prescribed aid was no longer adequate for reading.

All patients underwent a standard ophthalmological examination in our Low Vision Service including best-corrected distance visual acuity, evaluation of magnification requirement, provision of low vision aids and measurement of reading speed using standardized texts with and without low vision aids. Distance visual acuity was measured using an EDTRS chart with the patients' best refractive correction for distance. Magnification requirement was tested using a 4.0-diopter add to the distance correction using a Zeiss reading chart at 25 cm distance with different print sizes and standardized illumination of 70 cd/m². The smallest print size for fluent reading results in the magnification power, which is indicated by how much newspaper print of the usual size has to be magnified in order to be read at a distance of 25 cm. The magnification requirement of the better eye was used to prescribe the low vision aids. In order to estimate the potential need for optical or electronic vision aid, magnification requirements (MR) were principally grouped into three grades: Grade 1—MR up to 3-fold; Grade 2—MR 4- to 6-fold, and Grade 3—MR of more than 6-fold. According to the MR, the appropriate low vision aid was carefully tested and administered. Patients were trained to handle the prescribed low vision aid and to read with the low vision aid for at least 30 minutes under professional supervision.

Reading speed was measured using standardized texts and was calculated as number of words per minute (wpm) by the formula:Details of our examination protocol were provided in previous studies.¹¹, ¹⁹ All measures were assessed during the routine clinical examination in the Low Vision Clinic Tübingen. The study matches the tenets of the Declaration of Helsinki.

Statistical Analysis

All data were entered in specially designed data sheets and stored in a relational data base (Microsoft Office Access). Results were indicated descriptively as mean values and standard deviation. Comparisons between reading speed before and after provision of low vision aids were performed using the Mann-Whitney U-test for dependent samples. Correlation between reading speed and magnification power was estimated by means of Spearman's rank order correlation coefficient. P-values < 0.05 were regarded as indicators of statistical significance. All statistical analyses were performed using SPSSWIN 14.0 (SPSS Inc, Chicago, IL).

RESULTS

Mean Magnification Requirement

Mean magnification requirement was 8.0 ± 6.2 fold, 257 patients (39%) needed MR up to 3-fold (Grade 1), 101 patients (15.4%) had an MR between 4- to 6-fold (Grade 2) and in 298 patients (46.6%) the MR exceeded 6-fold (Grade 3). The visual rehabilitation was sufficient with optical low-vision aids in 54%. In 44.5% electronic closed-circuit TV systems were necessary. Only 1.5% of the patients needed an electronic reading device converting printed text into synthesized speech.

Mean Reading Speed

Mean reading speed for the whole group without vision aids was on average 12 ± 25 wpm and increased up to 71 ± 33 wpm with suitable aids. There are significant differences (p < 0.0001) between reading speeds in different groups according to the three levels of magnification before (Grade 1/Grade 2/Grade 3: 27 ± 33/7.4 ± 14/0.3 ± 3.0) and after rehabilitation with vision aids (95 ± 28/72 ± 24/46 ± 20, respectively) (Figure 1). There is a significant negative correlation of magnification requirement and reading speed with vision aids (r = − 0.65, p < 0.0001).

Figure 1 Error bars represent 95% confidence intervals for mean reading speed [wpm] before and after providing low vision aids in group of patients with magnification requirement (MR) up to 3-fold (before/after: 27 ± 33/95 ± 28), in group of patients with MR of 4 to 6- fold (before/after: 7.4 ± 14/72 ± 24) and in group of patients with MR of more than 6-fold (before/after: 0.3 ± 3.0/46 ± 20). In all three groups, mean reading speed increased significantly with suitable visual aids.

Patients with a lower magnification requirement (less than 6-fold) showed a higher increase of reading speed (67 ± 28 wpm) than patients with high magnification requirement (45 ± 20 wpm) (p < 0.001) (Figure 2).

Figure 2 Bars showing means (+ SD) of the total amount of the difference of reading speed before and after providing low vision aids. Patients with a lower magnification requirement (up to 6-fold) showed a higher increase of reading speed (67 ± 28 wpm) than patients with higher magnification requirement (> 6-fold) (45 ± 20 wpm) (p < 0.0001).

DISCUSSION

Reduced reading ability severely lowers quality of life. Patients are not independent any more and furthermore, they can lose their jobs or elderly patients may have to move to a nursing home. Besides medical and/or surgical therapy, rehabilitation plays an important role to provide the patients with low vision aids for their private, social and business needs. In addition, visual impairment can lead to an inability to watch TV, to recognize faces or to do manual work requiring paramacular vision. Recent research has shown how vision impairment compromises quality of life and limits social interaction and independence.⁸ Vision impairment caused by AMD has also been shown to cause depression and that significant psychological distress is similar to that of people with other serious chronic illnesses.⁸, ⁹, ¹⁰ Despite new pharmacological treatment options, the majority of AMD patients, especially those with dry AMD, cannot be treated and develop persistent visual deficits during the course of the disease. Therefore, vision rehabilitation is important and should be considered even in earlier stages of AMD. The results of the present study indicate the great value of vision rehabilitation by carefully providing adequate low vision aids in regard to maintaining and optimizing reading ability in patients with AMD. With appropriate low vision aids our patients could increase their mean reading speed up to 71 ± 33 wpm, which indicates that most of our patients could achieve reading speeds that allow sufficient access to printed information. Whittaker and Lovie-Kitchin reported that a reading speed of 80 wpm is fluent and 40 wpm is adequate for spot reading. A previous study of our group also showed that fluent reading corresponded to > 70 wpm.¹⁸, ²⁰ The effectiveness of low vision aids has also been confirmed in previous studies based on vision-related questionnaires or on evaluation of reading speed.¹¹, ¹⁹, ²¹, ²²

One important fact is that we clearly show a significant correlation of magnification requirement and reading speed with and without vision aids (Figure 1), which indicates a decrease of reading speed with increasing magnification need. Patients with a lower magnification requirement (less than 6-fold) showed a significantly higher increase of reading speed than patients with a high magnification requirement (Figure 2). The fact that patients with lower magnification could benefit much more from low vision aids confirms the observation that magnification can compensate for reduced retinal resolution but not for the effect of the scotoma.², ²⁰

According to our previous studies assessing the magnification requirement as an indicator for reading ability in patients with visual impairment is more important than measuring distance visual acuity.²³, ²⁴ For the assessment of reading ability and the application of low vision aids, the careful measurement of magnification requirement is much more meaningful and allows examiners to optimize the appropriate vision aids for patients. In clinical practice, the simple grading of the magnification requirement into three grades allows us to estimate a priori appropriate vision aids for patients as those grades describe the potential need for an optical or electronic vision aid: for Grade 1, more powerful glasses up to 4 diopters, magnifying glasses or magnifiers up to 12 diopters; for Grade 2, free-standing/hand-held magnifiers or hyperoculars up to 24 diopters as well as telescopes and for Grade 3, mostly electronic vision aids are needed. For the final prescription of devices, a careful, individual administration is required.

Another important aspect of our present study is the use of a new standardized international reading speed text (IReST), which was developed and evaluated during a European multicenter study (AMD-READ) for assessment and optimization of macular function with special regard to reading in AMD-patients (www.amd-read.net).²⁵, ²⁶ In contrast to other reading texts such as the MNREAD-Test (in English) or Radner Test (in German),²⁷, ²⁸ our IReST consist of longer text passages with equal length and comparable linguistic complexity, therefore reading speed can be measured more accurately and comparably at different examination times. As this new standard text set is now available in six languages (English, Finnish, French, German, Arabic and Portuguese), IReST will be a valuable tool for measuring reading speed in international studies on low vision research. In our opinion, the measurement of reading speed is not time-consuming for routine use in busy eye clinics and should be performed regularly.

It should be kept in mind that our study did not deal with training of eccentric viewing or training of a preferred retinal locus. The main focus of our study was to evaluate the effectiveness of adequate, professional providing of and training in the use of low vision aids for reading. The need and the effects of eccentric viewing for improvement of reading speed in patients with AMD were reported in studies by Nilsson and co-workers.²⁹, ³⁰ However, the necessity and effectiveness of eccentric viewing training is still a matter of controversy and depends on several preliminary conditions such as scotoma characteristics, fixation stability and the agility of focal visual attention.¹⁸, ³¹, ³², ³³ Our results show the great value of low vision rehabilitation by adequate providing of and training in the use of vision aids for improvement of reading ability with a highly significant increase of reading speed in patients with low magnification requirements. It should underline that our patients were not simply instructed how to handle the low vision aid, they were trained to read with prescribed aid carefully for at least 30 minutes before the vision aid was prescribed. Our results confirm the essential need of professional and educational training in handling and using low vision aids.¹⁹, ³⁴ The prescription of the final magnifying aid should take place only after a careful individual assessment. Handling of the low vision aid and hand-eye coordination must be learned intensively in the low vision service and also at home.

In conclusion, today the possibilities and the success of ophthalmological rehabilitation for AMD patients are very high. With the care of a low vision clinic, patients benefit a lot from rehabilitation, so that their quality of life can increase. Not only low vision professionals but also the ophthalmologist should consider this important option early in order to help patients keep their independence and mental agility.

ACKNOWLEDGEMENT

This study was supported by the Herbert-Funke Foundation. The authors thank C. Gehrlich and H. Eisenstein for recruitment of patients and data collection.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.