Handheld Magnifiers Research Articles

Efficacy of low-vision devices in elderly population with age-related macular degeneration.

Age-related macular degeneration (AMD) is a common cause of blindness, residual damage to macular area in spite of treatment necessitates visual rehabilitation by means of low-vision aids (LVAs). Thirty patients suffering from different stages of AMD requiring LVAs were included in this prospective study. Patients with nonprogressive, adequately treated AMD were enrolled over a 12-month period, prescribed requisite LVAs and followed-up for a minimum 1-month period. Before and after provision of LVAs, near work efficiencies were evaluated by calculating reading speed as words per minute (wpm) under both photopic and mesopic light conditions, and impact of poor vision on activities of daily living (ADL) was quantified by modified standard questionnaire based on Nhung X et al. questionnaire. Of the 30 patients mean studied with mean age of 68 ± 10 years, 20 patients (66.7%) had dry AMD in better eye and 10 (33.3%) had wet AMD. Post-LVA, near visual acuity improved significantly and all cases were able to read some letters on near vision chart with an average improvement of 2.4 ± 0.96 lines. The different LVAs prescribed were high plus reading spectacles (up to 10 D) in 23.3%, hand-held magnifiers in 53.3%, base in prisms in 10%, stand held magnifiers in 6.7%, and bar and dome magnifiers in 3.3%. LVAs are effective in visual rehabilitation in patients with AMD. Self-reported reduction in visual dependency and improvement in vision-related quality of life post use of aids corroborated perceived benefit.

What are the reasons for abandonment of low vision devices prescribed in a large tertiary eye care centre?

To investigate abandonment rates of near-vision low vision devices (LVDs) and factors that influence abandonment among patients attending a tertiary low vision rehabilitation centre in South India. Two hundred and eighty-six adults with low vision completed the modified device abandonment survey 1 year following device prescription. The survey included six questions: possession of device, timing of last use, reasons for abandonment, tasks for which the device was used, payment type and change in quality of life (QoL) from device use. The primary outcome measure was abandonment. Multivariate logistic regression analysis was used to investigate factors for abandonment. Three hundred and twelve near-vision devices were prescribed (mean, 1.09 device per patient.) Stand magnifiers (35%) followed by hand-held magnifiers (24%) were most frequently prescribed. Mean logMAR visual acuity (Snellen) in the better-seeing eye was 0.80 (6/38). Of the prescribed near-vision devices, 22% (95% CI, 17 to 27) were abandoned. Patients who abandoned the device were significantly older than those who did not (49.3 ± 17.2 vs. 43.5 ± 18.1 years; p=0.03). In multivariable analysis, patients reporting no change in their QoL from device use had higher odds of abandoning the device (OR: 63.97; 95% CI, 23.77 to 172.12). Device-related (31%) and psychological (30%) factors were the most frequent reasons for abandonment. Among device-related issues, the most frequent reason was that patients felt the device was too complex to use (50%) followed by being too cumbersome to use (25%). The abandonment rate for near-vision LVDs in South India was comparable with that reported in high-income countries. Patients reporting no change in their QoL had a higher likelihood of abandoning the device compared with those who reported some change. Device-related and psychological factors were the most frequent reasons for abandonment. These results can be used to develop strategies to improve compliance with use of devices.

Еlectronic video magnifiers as a low-vision aid for patients with Stargardt disease

Electronic video magnifiers outperform optical systems in terms of convenience and image quality. However, visually impaired patients and ophthalmologists in Russian Federation mostly lack knowledge of these useful technical rehabilitation devises. As shown by a survey of patients (n=141) with inherited retinal dystrophy, conducted by the public organization Look To See! 13% of patients use video magnifiers for writing, and 25% are satisfied with their devices. This article compensates for the gap in knowledge about electronic video magnifiers.
 Video magnifiers come in three main types: handheld, desktop, and portable. Wearable video magnifiers are the recent addition to these types. Each type has its own advantages and disadvantages, which determine their main functionality. Handheld video magnifiers are suitable for reading, desktop ones are used to equip a workplace; portable ones are ideal for schoolchildren because they can be used in reading and writing and easily carried to classes. Wearable video magnifiers are a promising class, but a well-established view on their use is still lacking.
 Ophthalmologists must have not only knowledge about the technical component but also the mechanism of operation of video magnifiers and how to draw up the necessary documents for their acquisition after establishing a disability and for their legitimate use in a general education school.

Possession of Low Vision Reading Devices Among Residents Living in a Retirement Facility

Introduction: The purpose of this cross-sectional survey was to examine the possession of low vision reading devices and factors associated with possession of these devices among residents living in a continuing care retirement community. Low vision reading devices are devices other than eyeglasses that aid in reading at near distances. Methods: One hundred and two usable questionnaires were received from residents, ages 65–97 years old, living in the independent and assisted living units of a retirement community. Results: Data indicated that 47% the participants reported having an eye disease, and 53% of the participants owned at least one low vision reading device. The two most common types of devices were handheld magnifiers (40%) and gooseneck lamps with or without a magnifier (26%). Of the 48 participants reported to have eye disease diagnoses, 65% owned a reading device. Forty-six percent of the participants reported having trouble with reading when performing one of the six daily activities even with their reading eyeglasses. The final multivariable logistic regression model indicated that participants who reported having trouble with reading in near distance were significantly more likely to own one of the reading devices. Discussion: This study identified a discrepancy between the high prevalence of visual impairment (i.e., blindness and low vision) among residents living in a retirement community setting and a relatively low number of residents owning low vision reading devices. Findings suggested the key factor contributing to residents’ decision to own reading devices is their level of visual impairment. Implications for Practitioners: Knowing the factors to owning low vision reading devices, occupational therapists may assist residents in continuing care retirement facilities to obtain the appropriate devices.

Bluetooth Low Energy Beacon Sensors to Document Handheld Magnifier Use at Home by People with Low Vision.

We explored the feasibility of using Bluetooth low energy (BLE) beacon sensors to determine when individuals with low vision (LV) use handheld magnifiers at home. Knowing the frequency and duration of magnifier use would be helpful to document increased magnifier use after successful rehabilitation training, or conversely, to know when someone has abandoned a magnifier and requires assistance. Estimote Sticker BLE beacon sensors were attached to the handles of optical handheld magnifiers and dispensed to eight LV subjects to use at home. Temperature and motion data from the BLE beacon sensors were collected every second by a custom mobile application on a nearby smartphone and transmitted to a secure database server. Subjects noted the date and start/end times of their magnifier use in a diary log. Each of the 99 diary-logged self-reports of magnifier use across subjects was associated with BLE beacon sensor recordings of motion (mean 407 instances; SD 365) and increased temperature (mean 0.20 °C per minute; SD 0.16 °C) (mean total magnitude 5.4 °C; SD 2.6 °C). Diary-logged duration of magnifier use (mean 42 min; SD 24) was significantly correlated with instances of motion (p < 0.001) and rate of temperature increase (p < 0.001) recorded by the BLE beacon sensors. The BLE beacon sensors reliably detected meaningfully increased temperature, coupled with numerous instances of motion, when magnifiers were used for typical reading tasks at home by people with LV.

Effectiveness of Low Vision Aids in patients with low vision attending a medical college hospital

Introduction: Low vision is defined as visual impairment despite treatment, surgery, or standard refractive correction, but with the potential to use the residual vision. The aim of the study was to explore the clinical profile of patients requiring Low Vision Aids (LVA) and assess the effectiveness, of LVA among patients with low vision. Material and Methods: Fifty patients fulfilling the criteria of low vision were recruited after obtaining informed written consent and detailed ocular evaluation was done to detect the cause of low vision. A trial of LVAs was done for near using hand-held magnifiers (+6D, +14D, +20D), stand magnifiers (+8D, +14D, +20D) and spectacle magnifiers (+6D, +10D, +14D, +20D) and visual improvement was noted. Similarly, LVAs were tried for distance using telescope 2.5X and clip-on telescope 3X. Results: The majority of the participants (72%) belonged to the upper lower class. The most common causes of low vision were heritable conditions like retinitis pigmentosa (24%), bilateral primary optic atrophy (18%), and macular dystrophies (16%). The most effective low vision aids were handheld and stand magnifiers which improved vision by one to four lines. The magnifiers were most effective in eyes with macular dystrophy, retinitis pigmentosa, and age-related macular degeneration. Conclusion: Low vision aids are potential methods of improving the residual vision in low vision patients. In the background of the high and increasing prevalence of low vision and poor awareness about low vision aids among them, efforts are necessary to rehabilitate them with affordable and accessible low vision services.

Feasibility of Using Bluetooth Low Energy Beacon Sensors to Detect Magnifier Usage by Low Vision Patients.

We demonstrated proof of concept for the potential for Bluetooth low energy beacons to reliably collect data to serve as an indicator that low vision patients are using handheld magnifiers for reading, which might be used in the future to prevent the abandonment of magnification or other assistive devices. Bluetooth low energy beacons are an emerging novel technology involving tiny sensors that collect real-time, continuous, objective data, which might help to ascertain the abandonment of low vision devices in a timely manner, thus prompting a follow-up evaluation to attempt to resolve issues. We evaluated whether Bluetooth beacon data could indicate when low vision patients used handheld optical magnifiers for reading. We recorded temperature and/or relative humidity data from Estimote sticker and BlueMaestro Tempo Disc beacons attached to handles of optical magnifiers used for reading by low vision patients in clinic (n = 16) and at home (n = 3). In the clinic, patients whose hand/fingers made direct versus indirect contact with Estimote beacons had greater temperature increases on average from baseline after 30 seconds (0.73°C vs. 0.28°C), 60 seconds (1.04°C vs. 0.40°C), 90 seconds (1.39°C vs. 0.60°C), 105 to 120 seconds (1.59°C vs. 0.62°C), and 135 to 150 seconds (2.07°C vs. 0.97°C). During magnifier usage at home, BlueMaestro beacons measured rapidly increased temperature (5.6°C per minute on average; range 2.7 to 7.3°C) and relative humidity (19.4% per minute on average; range 8.7 to 34%). Humidity tended to reach its maximum increase and return back to baseline significantly more quickly than temperature (P = .007). All increases during magnifier usage were much greater than the maximum room fluctuations without use (clinic, 0.2°C over 120 seconds; home, 0.6°C and 2.4% over 1 minute). The beacons were nonintrusive and acceptable by patients. Estimote and BlueMaestro beacons can reliably detect temperature and/or humidity increases when held by low vision patients while reading with a magnifier.

Functions and uses of metallic axe-heads and arrowheads from Safah, Oman: An analysis of metalwork wear and weapon design

This paper seeks to identify possible functions and uses of the Early Iron Age copper-alloy axe-heads and arrowheads which were found in the Safah metal workshop. In order to achieve this objective, metalwork wear analysis of twenty-four arrowheads and fifteen axe-heads are discussed in respect of design, use, typological resemblances and rock art representations of these weapons. Metalwork wear on each specimen is recorded with the help of handheld magnifiers. The recorded traces are compared with the published findings of the experiments which were conducted with copper-alloy weapon reproductions. The metalwork wear analysis of axe-heads and arrowheads is presented in line with the preliminary typological groupings which were categorised by the Safah excavation team. This article should be viewed as a preliminary analysis of axe-heads and arrowheads from Safah, not a full-scale study of metalwork wear, because of two factors: (1) the absence of experiments which are done with precise reproductions of these weapons and (2) thick corrosion on the samples. In view of these biases, technological and typological considerations are augmented by the examination of macro deformations. In the case of arrowheads, notches and breakages are the most common marks and they are mostly spotted on the lateral edges of the blades. Some edge deformations were also recorded on the lower half and the tang of the arrowheads. Pertaining to experimental studies, the former is associated with backwards movement and technological treatments and the latter is usually linked with the shaft's backlash with the point. Asymmetrical cutting edges, casting flows, micro-folds and breakages were observed on the axe-heads. Micro folds and breakages could not be associated with a certain activity, inarguably. Only one axe-head displays possible marks of combat. Casting flows illustrate the casting activity taking place in Safah. Asymmetrical cutting edges of one axe-head exhibit a relatively long span of use and sharpening. Most of the axe-heads in Safah were not deformed intensively. This point suggests that if these were brought to Safah for recycling they were not gathered there due to loss of function.

Low-vision aids improve the visual performance of children with bilateral chorioretinal coloboma

To quantify the improvements in visual performance for both distance and near tasks attained by children with bilateral chorioretinal coloboma (CRC) with use of low-vision aids (LVAs). This was a hospital-based, cross-sectional, interventional case series of children with bilateral CRC. Demographic data were collected through a structured questionnaire and review of medical records. Distance and near best-corrected visual acuity, contrast sensitivity, and reading speed were evaluated with refractive correction alone and with the use of LVAs (Keplerian telescopes for distance; handheld magnifiers and a tinted lens [400nm filter] for near). Effects are presented as medians of differences with 95% binomial-exact confidence intervals. Six children were included (median age, 11.5years; range, 7-17years), of whom 5 were already using LVAs on a daily basis. The use of a Keplerian telescope achieved a significant median improvement in distance best-corrected visual acuity of 0.75 logMAR (95% CI, 0.20-1.20). Contrast sensitivity was also improved across all tested spatial frequencies. Use of near LVAs resulted in a significant median improvement in near reading acuity of 0.47 logRAD (95% CI, 0.28-0.90). Critical print size and reading speed at N10 were also improved. LVAs enable meaningful improvements in the visual performance of children with bilateral CRC, allowing noteworthy increases in distance and near visual acuities as well as good reading speeds at small print sizes.

LOW VISION AIDS IN OPTIC ATROPHY

Purpose: To analyze utilization of prescribed Low Vision devices in cases of Optic Atrophy. &#x0D; Methods: Prospective, Cross Sectional Study was performed in tertiary eye care centers within the period of 3 years. Screening was done and subjects were taken to tertiary centers for further evaluation. Visual functions along with slit lamp and fundus evaluation was performed and treatment was provided accordingly. Subjects who were in the criteria of low vision was enrolled in the study and given low vision aids as per the need. Training of usage of devices was given for 15 days and follow up was taken after 3 months to know utilization of prescribed low vision devices. Data was collected and analyzed using SPSS software version 20. &#x0D; Results: 97% of subjects were enrolled into the study. Out of them, 61% were males. Spectacle Refraction was best achieved by Stenopaeic Slit refraction and given full prescription where required. For distance, Monocular Hand Held Telescopes, Clip on Telescopes or Spectacle Mounted Telescopes were prescribed. For near, Aspherics, Hand Held Magnifiers, Stand Magnifiers And Or Reading Stand were prescribed. Photochromatics or Dark Sunglasses were prescribed for reduction of glare. On 3 month follow up, it showed that Monocular Hand Held Telescopes of variable power (69%) was accepted maximum for distance. Photochromatics (96%) was maximally accepted for reduction of glare. For near, Non Optical Device – Reading Stand (78%) was accepted by most of the subjects. It shows that optical devices help much more for distance while non optical devices should be preferred for near work. &#x0D; Conclusions: In cases of optic atrophy, Monocular Hand Held Telescope of variable power as per the need, Photochromatics for glare reduction and Reading Stand for near work should be prescribed

Visual profile of students in integrated schools in Malawi

BackgroundBlindness and visual impairment are very common in African countries and are often loosely linked to inadequate resources. We designed this study to assess clinical visual and ocular characteristics of children in three integrated schools in Malawi, so that students needing low vision services or those with correctable refractive error will be identified.MethodsWe included 95 students, who underwent a detailed optometric examination. The assessment included distance visual acuity measurement in logMAR notation, near visual acuity, oculo‐motor assessment, pupillary assessment and anterior as well as posterior segment evaluation. Non‐cycloplegic refraction was done in all the participants.ResultsMean age of students was 13.84 ±4.61 years. Almost 90 per cent of students had presenting visual acuity worse than logMAR 0.54. Visual acuity improved significantly after refractive correction by more than two logMAR lines in 31.8 per cent (p < 0.0001). Refractive error was very common (36.5 per cent) and the most common causes of visual impairment were lenticular (21.2 per cent), corneal (20.0 per cent) and albinism (15.3 per cent). One‐tenth (10.5 per cent) of the students were wrongly enrolled in the schools, even though they did not have visual impairment. The compliance to spectacles wear was very poor (37 per cent). An adequate refractive correction improved visual acuity in more than a third (36.5 per cent) of the students. Students benefited from spectacle magnifiers (18.8 per cent), handheld magnifiers (4.7 per cent) and telescopes (5.9 per cent). Mobility canes were advised for 36.5 per cent of the students.ConclusionNine out of ten students in three integrated schools in Malawi had visual impairment and 41 per cent had low vision. Inappropriate placement in the integrated schools and poor spectacle compliance are very common. Well accepted optical and non‐optical devices could improve visual performance in visually disabled children, for which public awareness and parental education is important.

Requirements for low vision magnification aids in age-related macular degeneration: Data from the Tübingen low vision clinic (comparison of 2007-2011 with 1999-2005)

The purpose of this study was to investigate if there has been a change in requirements for low vision magnification aids in recent years. The collective data from age-related macular degeneration (AMD) patients from the Tübingen low vision clinic from the years 2007-2011 were compared with the patient collective from the years 1999-2005. Magnification needs and the prescribed magnifying aids for reading in the categories magnifying spectacles, hand-held magnifiers, monocular telescopes, electronic magnifiers and electronic reading devices were evaluated. In addition patients from 2010 and 2011 were divided into dry and neovascular AMD and the prescribed magnification aids were compared for these AMD forms. There was no significant change in in the prescribed magnification reading aids for AMD patients between the years 1999-2005 and 2007-2011. An electronic magnifier was prescribed most often (both collectives 43 %), followed by hand-held magnifiers (32 and 29.5 %, respectively) and magnifying spectacles (17 and 18.8 %, respectively). Also the magnifying needs and mean age of the AMD patients did not change significantly between the two periods (2007-2011 versus 1999-2005). The detailed analysis for dry and neovascular AMD for the years 2010 and 2011 showed no significant differences for the most commonly prescribed low vision aids. The prescription of low vision aids is not influenced by the AMD classification (dry or neovascular), only by the magnification needs. There is an unchanged and still high demand for rehabilitation aids of AMD patients, for dry as well as for neovascular AMD even after the introduction of anti-vascular endothelial growth factor (anti-VEGF) therapy.

Point of care cutaneous imaging technology in melanoma screening and mole mapping.

Melanoma is a malignancy of melanocytes or pigment-producing cells located predominantly in the skin. It is less common than other skin cancers but causes the greatest number of skin cancer-related deaths worldwide. The incidence of melanoma continues to increase and early detection is the most promising means of decreasing morbidity and mortality. Currently, physicians perform routine skin cancer screenings for melanoma without the benefit of imaging devices more advanced than handheld magnifiers or dermatoscopes. However, it is possible that the diagnosis of melanoma may be improved with technology that provides diagnostic discrimination beyond what is possible on routine inspection. This article reviews current and emerging technologies to aid in the diagnosis of melanoma. Ultimately, these advances may enhance the early diagnosis of melanoma.

Reading aids for adults with low vision.

The purpose of low-vision rehabilitation is to allow people to resume or to continue to perform daily living tasks, with reading being one of the most important. This is achieved by providing appropriate optical devices and special training in the use of residual-vision and low-vision aids, which range from simple optical magnifiers to high-magnification video magnifiers. To assess the effects of reading aids for adults with low vision. We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2013, Issue 1), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE, (January 1950 to January 2013), EMBASE (January 1980 to January 2013), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to January 2013), OpenGrey (System for Information on Grey Literature in Europe) (www.opengrey.eu/), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov/) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 31 January 2013. We searched the reference lists of relevant articles and used the Science Citation Index to find articles that cited the included studies and contacted investigators and manufacturers of low-vision aids. We handsearched the British Journal of Visual Impairment from 1983 to 1999 and the Journal of Visual Impairment and Blindness from 1976 to 1991. This review includes randomised and quasi-randomised trials in which any device or aid used for reading had been compared to another device or aid in people aged 16 or over with low vision as defined by the study investigators. At least two authors independently assessed trial quality and extracted data. We included nine small studies with a cross-over-like design (181 people overall) and one study with three parallel arms (243 participants) in the review. All studies reported the primary outcome, results for reading speed.Two studies including 92 participants found moderate- or low-quality evidence suggesting that reading speed is higher with stand-mounted electronic devices or electronic devices with the camera mounted in a 'mouse' than with optical magnifiers, which in these trials were generally stand-mounted or, less frequently, hand-held magnifiers or microscopic lenses. In another study of 20 participants there was moderate-quality evidence that optical devices are better than head-mounted electronic devices (four types).There was low-quality evidence from three studies (93 participants) that reading using head-mounted electronic devices is slower than with stand-based electronic devices. The technology of electronic devices may have changed and improved since these studies were conducted.One study suggested no difference between a diffractive spectacle-mounted magnifier and either refractive (15 participants) or aplanatic (15 participants) magnifiers.One study of 10 people suggested that several overlay coloured filters were no better and possibly worse than a clear filter.A parallel-arm study including 243 participants with age-related macular degeneration found that custom or standard prism spectacles were no different from conventional reading spectacles, although the data did not allow precise estimates of performance to be made. There is insufficient evidence on the effect of different types of low-vision aids on reading performance. It would be necessary to investigate which patient characteristics predict performance with different devices, including costly electronic devices. Better-quality research should also focus on assessing sustained long-term use of each device. Authors of studies testing several devices on the same person should consider design and reporting issues related to their sequential presentation and to the cross-over-like study design.

Establishing the Service Potential of Secondary Level Low Vision Clinics

To determine the proportion of people with low vision who can be adequately managed at a secondary level low vision clinic where only low to moderate magnification low vision devices (LVDs) and basic rehabilitation services are provided. A retrospective study of clinical records of participants who attended low vision rehabilitation services (Vision Australia) for the first time between 2000 and 2002 was conducted. Information regarding main cause of vision loss, goals of vision rehabilitation, types of LVDs purchased, and type of services received was examined. Of the 192 participants studied, 65% were female and the mean age was 76 years (range, 19 to 100 years). Most participants had mild (35%) to moderate (49%) vision impairment. Seventy percent (134) of participants purchased some type of LVDs. Near adds of low magnification (1 to 2×) were the most common aid preferred by participants (n=54) followed by handheld magnifiers of moderate magnification (2.5 to 5×; (n=52). Only 10 of the 134 LVDs (8%) purchased were of high magnification (>5×). In addition, only 46 of the 192 participants (24%) attended tertiary level rehabilitation with orientation and mobility (O&M) instructors and/or occupational therapists. Along with the six participants who required high magnification LVDs but no O&M or OT services, in total, 27% (52/192) required tertiary level low vision care. A secondary level low vision clinic is likely to meet the needs of >70% of people with vision impairment. It would play an important role in vision rehabilitation especially in countries where a wide range of services are available.

Reabilitação visual em pacientes com retinose pigmentária

To determine which low-vision aids could be useful to patients with retinitis pigmentosa and also the benefits that the rehabilitation program could provide based on visual acuity and/or daily visual tasks. A group of 30 patients with retinitis pigmentosa aged from 7 to 73 years were enrolled in this study. Visual acuity and visual function tests (visual field, full-field electroretinogram) was performed and low-vision aids tested. Information about the use of the remaining vision was obtained. After choosing the best optical or electronic devices and before their prescription, a low-vision training program was carried out. The best corrected visual acuity varied from HM (hand movements) to 20/40 for distance and visual acuity better than 16M to 0.5M for near. 90% of the patients had optical devices prescribed: 13 for near, 9 for distance, 2 electronic devices and 3 filters. Three patients with extremely narrow visual field and very low visual acuity were referred to orientation and mobility. The low-vision aids were useful for the retinitis pigmentosa patients: telescopes, hand-held magnifiers, stand magnifiers, half-eye base-in prism lenses, electronic devices and illumination control were beneficial to enhance visual acuity and visual efficiency. The prescription of low-vision aids was helpful in daily-life activities and a high level of satisfaction with the implemented visual rehabilitation program was reported.

Risk assessment of optically aided viewing

The definition and measurement of Class 1 and Class 3A accessible emission limits relates very much to one simple question: “How much energy will be collected by magnifying optics?” To simulate the increased risk of optically aided viewing by telescopes and binoculars, a 50 mm aperture (at one time 80 mm) has been used in ANSI, CDRH, and IEC standards. The current measurement criterion found in IEC 60825-1 was a compromise, and makes use of a 50 mm aperture at a distance of 100 mm to define a geometrical collection efficiency to simulate not only that of telescopes and binoculars, but also that of highly diverging laser and light emitting diode emission patterns as well. It was later recognized that this was a rather arbitrary mathematical construct designed to mimic both a high-power eye loupe at a very close distance (14 mm) and a 7×50 binocular at a much greater viewing distance. This approach is not followed in the U.S. standards, and the two types of sources are treated differently. While the IEC approach appears at a first glance to have the advantage of simplicity and requires little laboratory space for measurements, it fails to accurately describe the real hazard for both conditions of optically aided viewing. Hand-held magnifiers and eye loupes increase the retinal or corneal hazard by effectively collimating the divergent beam and directing more energy into the true limiting aperture: the eye’s pupil (simulated by the 7 mm aperture for dark-adapted viewing). By contrast, telescopes and binoculars which can produce a sharp image only at distances beyond at least 2 m, collect more radiant energy. A better simulation of risk is afforded by a 50 mm aperture at 2 m and a 7 mm aperture at about 10 cm.

Low vision magnifiers--their optical parameters and methods for prescribing.

Information provided by manufacturers of low vision magnifiers is usually insufficient to allow the clinician to predict accurately the resolution improvement that patients may be expected to achieve. We have measured and tabulated the key optical parameters of 92 stand magnifiers and 53 hand-held magnifiers. For the fixed focus stand magnifiers, the image location and the equivalent power of the lens system have been determined and the enlargement ratio has been derived. For each magnifier, 3 different eye-to-lens distances (2.5, 10, and 25 cm) have been considered and, for each of these, the Equivalent Viewing Distance (EVD), the eye-to-image distance, and the theoretically predicted field width have been computed. The EVD is useful in predicting resolution performance because, for a given patient, the visual resolution limit will be directly proportional to the EVD. The eye-to-image distances allow the clinician to consider whether the patient will be in satisfactory focus or whether adjustments need to be made to the power of any reading addition. The stand magnifiers are listed in order of the EVD they give when the eye is a moderate (10 cm) distance from the magnifier. For the hand-held magnifiers, the equivalent powers have been measured. The EVD for a hand-held magnifier will be the same as the equivalent focal length of the magnifier if the lens is used so that the image is at or close to infinity. The tables include supplementary information on the size of the magnifier lenses and whether the magnifiers incorporate battery, electric, incandescent, or halogen lighting systems. Examples are presented to illustrate how the tables might be used in the selection of magnifiers to meet the resolution and other needs of individual patients.

Optical Treatment of Residual Vision in Diabetic Retinopathy

The purposes of this study of diabetic retinopathy are to classify degree of vision impairment, determine the percentage of patients for whom vision can be improved by an accurate refraction, identify the most useful magnifying devices, and arrive at the success rate for the magnifiers. Study of 101 consecutive subjects. Visual acuity was 20/200 (6/60) or better in 71% of subjects. Spectacle correction improved vision for 29%. High-add bifocal magnifiers improved vision for 30% of patients; half-eye spectacle magnifiers improved vision for 45%; and hand-held magnifiers improved vision for 11% of patients. Visolett magnifiers improved vision for 44%, and combination spectacle magnifiers and Visolett improved vision for 24% of patients. Multiple optical aids for 63% of patients resulted in a success rate of 68%. The ophthalmologist is obligated to ensure that eyes are refracted and appropriate magnifying devices are provided as part of treatment for diabetic retinopathy.

On the use of hand-held magnifiers during reading.

Little is known about the actual use of magnifiers (or loupes) during reading. In studying the influence of the use of magnifiers on the reading process the reading field is a relevant factor. Four reading fields are distinguished: three horizontal reading fields and the vertical reading field. We examined the influence of a variation in the widths of these fields on the reading behavior of subjects. This was done by measuring two-dimensional loupe movements while subjects read text under conditions that provided a variety of reading field widths. It was found that individual subjects use different reading-field widths depending on loupe dimensions. Most difficulties in reading with a magnifier, especially finding the beginning of a new line, appear to result from the need to move the loupes horizontally in order to read the complete line of text.