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PubMed2003

[Hereditary foveal hypoplasia - clinical differentiation].

BACKGROUND: In a family cataract, esotropia and foveal hypoplasia is dominantly transmitted. PATIENTS AND METHOD: Besides the physical examination visual evoked potentials and PAX6 mutation analysis were performed on five of six affected persons and on two who were not. RESULTS: A man of the first generation, deceased before this study, was known to have low vision. His two daughters and their children and grandchildren suffer from cataract, esotropia and foveal hypoplasia. In two cases accompanied by aniridia and atypical iris coloboma respectively. The best visual acuity is 0.5. The VEPs taken of three of the affected people were normal. The PAX6 mutation analysis demonstrated a T to A translocation in the Intron 8 at the position + 2 (= IVS8 + 2T --> A). CONCLUSION: 1) This study confirms that foveal hypoplasia in the so-called isolated form have a similar origin as in aniridia namely PAX6 mutation and that it is a symptom in all cases while the iris anomaly may be variable. 2) In contrast to this foveal hypoplasia in albinism may occur variably in a family while the asymmetry of VEP is a constant finding. 3) Therefore the VEP alone is helpful to differentiate clinically wether a foveal hypoplasia belongs to the albino or to the aniridia group.

Adolescent↗
PubMed2004

[Epidemiology of blindness in Baden, Germany].

BACKGROUND: There is no exact knowledge concerning blinding diseases in Germany. Purpose of this study was to investigate the changes of diseases leading to new blindness in Baden (Southern Germany). METHODS: We evaluated the ophthalmological diseases leading to blindness in Baden from the applications presented to the eye doctor for blind and low vision people in Baden, Germany from 1980 to 1999. RESULTS: 1511 applications for blindness (991 women and 520 men) aged 1-107 (mean age: 68 +/- 22 years) were evaluated. 62.5% of persons who had recently become blind, concerned patients aged 70 years or older, 4.6% under 10 years of age. Age-related macular degeneration (23.1%), glaucoma (22.0%), optic atrophy (19.1%), diabetic retinopathy (13.3%) and tapetoretinal degeneration (8.1%) were the main causes of blindness. There were only minimal changes over time. DISCUSSION: There were only marginal changes of the frequency of the eye diseases causing blindness for the time interval from 1980 to 1999. Age-related macular degeneration is the major cause especially in the higher age group. There are enormous deficits in the prevention of causes of visual impairment and blindness.

Adolescent↗
PubMed2002

The haptic Müller-Lyer illusion in sighted and blind people.

We examined the effect of visual experience on the haptic Müller-Lyer illusion. Subjects made size estimates of raised lines by using a sliding haptic ruler. Independent groups of blind-folded-sighted, late-blind, congenitally blind, and low-vision subjects judged the sizes of wings-in and wings-out stimuli, plain lines, and lines with short vertical ends. An illusion was found, since the wings-in stimuli were judged as shorter than the wings-out patterns and all of the other stimuli. Subjects generally underestimated the lengths of lines. In a second experiment we found a nonsignificant difference between length judgments of raised lines as opposed to smooth wooden dowels. The strength of the haptic illusion depends upon the angles of the wings, with a much stronger illusion for more acute angles. The effect of visual status was nonsignificant, suggesting that spatial distortion in the haptic Müller-Lyer illusion does not depend upon visual imagery or visual experience.

Adult↗
PubMed1996

Reading with magnifiers.

The design of low vision aids for partially sighted people, such as magnifiers, is evaluated theoretically in order to identify meaningful directions of research for improving these aids. Both reading with and without a magnifier involves alternating sequences of locating and recognizing textual information. Little is known, however, about these processes in magnifier reading. On the basis of an extensive review of the literature, two topics are identified that stand out as being in need of experimental investigation: (1) the relationship between the (typo)graphical characteristics of printed text and the location and recognition of textual information, and (2) the interplay of location and recognition processes in magnifier reading, including the role of non-visual factors, such as movements of the hand, trunk, head and eyes in this interplay. With regard to the first topic, it is expected that the visibility and, hence, the recognition of textual information by partially sighted people can be improved by matching the fundamental spatial frequencies of graphical structures with the spatial contrast sensitivity of partially sighted people. With regard to the second topic, it is argued that persistent problems in the design of the magnifiers, such as the optimal window size, can only be resolved by studying reading with a magnifier as a (multimodal) perceptual-motor activity.

Data Display↗
PubMed2005

The Pakistan national blindness and visual impairment survey--research design, eye examination methodology and results of the pilot study.

PURPOSE: To establish age- and sex-specific prevalence rates and causes of blindness and low vision in children aged 10 to 15 years and adults aged 30 years and older in Pakistan. METHODS: Multi-stage, stratified (rural/urban), cluster random sampling, with probability proportional-to-size procedures, was utilised to select a cross-sectional, nationally representative sample of adults (16,600 subjects) and children (6,000 subjects). Each subject underwent: interview, visual acuity (logMAR), autorefraction and optic disc examination. Those that saw < 6/12 in either eye underwent corrected visual acuity and dilated posterior segment examination. RESULTS: The results of a pilot survey are reported in this paper. In the two rural pilot sites, 159 subjects (including 47 children) were examined; 50% were male. Thirty seven adults (23.3%) but no children saw worse than 6/12 in either eye. Two subjects were blind (corrected visual acuity) in the better eye, and 11 were visually impaired. Refractive error was the main cause (in 22 eyes (39% of the total of 56 eyes)) of < 6/12 visual acuity, followed by cataract (12 eyes), uncorrected aphakia (6 eyes) and age-related macular disease (3 eyes). CONCLUSIONS: The pilot survey demonstrated that the proposed examination process for the main survey is feasible. Particular strengths of this survey include the use of logMAR visual acuity testing and autorefraction of all subjects, a dilated posterior segment examination, and the use of a 'less than 6/12' threshold for further examination. This lower threshold addresses the burden of refractive error, which, with cataract, are two of the diseases specifically targeted by Vision 2020.

Adolescent↗
PubMed1992

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).

Aged↗
PubMed1994

Congenital optic nerve hypoplasia.

Congenital optic nerve hypoplasia (CONH) is an increasingly recognized cause of low vision in children. The spectrum of ophthalmoscopic and clinical presentations of CONH is described here with illustrative cases. Some children with unilateral CONH develop a secondary, functional amblyopia that may respond to patching during visual development. Children with bilateral CONH, poor vision and nystagmus usually present early and have a high risk of exhibiting central nervous system (CNS) malformations and treatable endocrine deficiencies.

Adolescent↗
PubMed1999

Study of luminance effects on pinhole test results for visually impaired patients.

PURPOSE: The visual acuity of visually impaired patients has been reported to improve after a refraction, despite pinhole test results that show a decline or no change in acuity. Our aim was to investigate whether the pinhole-induced reduction in retinal illuminance accounted for these unreliable predictions of best-corrected acuity. METHODS: Participants were 64 adult patients referred for low-vision rehabilitation. Neutral density filters reproduced the pinhole-induced luminance loss, allowing pinhole test and postrefraction acuities to be measured at essentially equivalent levels of retinal illuminance. The following data were collected in random order from each subject's better eye: (1) habitual visual acuity, (2) habitual visual acuity with filter, (3) habitual visual acuity with pinhole, (4) best-corrected/postrefraction visual acuity, (5) postrefraction visual acuity with filter. RESULTS: On average, the pinhole test under-estimated postrefraction visual acuity by six letters (95% confidence limits = +/- 20). The pinhole test underestimated postrefraction visual acuity with the filter by two letters (95% confidence limits = +/- 16). Among subjects whose acuity improved with the pinhole test (N = 24), 83% experienced better postrefraction visual acuity. Among subjects whose acuity declined or remained unchanged with the pinhole test (N = 40), 50% achieved better postrefraction visual acuity. CONCLUSIONS: The pinhole-induced luminance loss contributed to inadequate predictions of postrefraction visual acuity. Pinhole test results were enormously variable, underestimating and overestimating postrefraction visual acuity. The pinhole test was less reliable when improvements in postrefraction visual acuity were small. Visually impaired patients deserve periodic refractions, and the pinhole test result should not be used as a dichotomizer for clinical decisions regarding the need for a refraction.

Adult↗
PubMed2005

An abbreviated reading speed test.

PURPOSE: The Minnesota Low-Vision Reading Test (MNREAD) has been developed to measure reading speed. An abbreviated version of the MNREAD test was developed that presented only three large paragraphs and would be easier for children to complete. METHODS: Fifty children ages 8 to 18 years, with normal eye examinations or refractive error alone, underwent testing of reading speed using the MNREAD test. All the children read the standard MNREAD paragraphs starting at the 1.0 logarithm of the minimum angle of resolution (logMAR) level until they could no longer read the subsequent paragraph. Each eye was tested separately, using the second MNREAD card for the left eye. The standard MNREAD reading speed was calculated by plotting the speed for each paragraph, determining the critical print size, then taking the median value of all the paragraphs above the cutoff paragraph. The proposed abbreviated test reading speed was calculated from the median of three large paragraphs (logMAR, 1.0, 0.9, and 0.8). At a second site, 25 children with a variety of ocular conditions were similarly tested using an alternative abbreviated test (logMAR, 1.3, 1.2, and 1.1). The standard and abbreviated reading speeds were then compared between tests and between eyes using generalized estimating equation and intraclass correlation coefficients. RESULTS: The mean reading method speeds with the standard and abbreviated tests were almost identical [177 words per minute (wpm) +/- 46 wpm vs. 178 +/- 46 wpm, p = 0.43 for normal children and 140 +/- 29 wpm vs. 141 +/- 33 wpm, p = 0.35 in children with a variety of ocular conditions]. CONCLUSION.: The new abbreviated version of the MNREAD reading speed test yields similar results to the standard MNREAD test in children. The new abbreviated MNREAD test is faster to administer and appears to be particularly useful for children.

Adolescent↗
PubMed2005

Screening compliance and visual outcome in diabetes.

PURPOSE: To study the relationship between screening compliance and visual outcome in a screening programme for diabetic eye disease. METHODS: A retrospective case control study. The screening compliance of all the diabetes patients (n = 22) listed at the Icelandic National Registry for the Blind (visual acuity <0.3) was compared to a matched group of 44 non-blind diabetes patients (visual acuity > or =0.3) who participated in the same screening programme for diabetic retinopathy. Glycaemic control (HbA1c), office blood pressure and cholesterol levels were assessed. RESULTS: The study group had a significantly lower level of compliance with the screening programme (27% +/- 38% [mean +/- SD] versus 77% +/- 26% [mean +/- SD]; p < 0.0001). Macular oedema or proliferative diabetic retinopathy was found in 60% (13/22) of the study group when entering the screening programme, compared to 7% (3/44) in the control group. Blood pressure (except diastolic BP among type 1 diabetes mellitus), blood glucose and cholesterol levels were identical. The prevalence of blindness and low vision amongst diabetes patients in Iceland is about 0.5%. CONCLUSIONS: There was a significant relationship between screening compliance and visual outcome in diabetes patients in our screening programme.

Adult↗
PubMed1992

Visual impairment in Nordic children. II. Aetiological factors.

Careful clinical-aetiological assessment of visually impaired children is one of the prerequisites for prevention of future, 'unavoidable' cases of visual impairment of children in the industrialized part of the world. In a collaborative study (NORDSYN) between four Nordic national registers of visual impairment, we analysed and classified some of the factors considered to be essential components for the development of low vision or blindness in children. We discuss the conceptual basis for aetiological classification of eye disorders and visual impairment. An aetiological classification system, based on the type and debut of an essential causal factor is introduced. We present data on 2527 visually impaired children from the Nordic countries. In accordance with several other reports from the last twenty years it is demonstrated that prenatal factors, including genetic aetiologies, were involved in a large proportion (66%) of the cases. In children without additional impairments the corresponding fraction was 74%. Genetic factors accounted for a little over half of the prenatal cases, and in a substantial number of children (40%) with visual impairments of prenatal origin, the causes were obscure. In 1/5 of the material some peri-neonatal causal or modifying factor was identified. In 7% only, the presumed aetiological factor was introduced in the infantile-juvenile period of life. Further prevention of visual impairment among children of the industrialized countries would benefit most from a more comprehensive understanding of prenatal, nongenetic causal factors, further knowledge about regulating mechanisms responsible for gene expression, and additional improvements in perinatal care.

Adolescent↗
PubMed2001

Causes of severe visual impairment and blindness in children attending schools for the visually handicapped in the Czech Republic.

AIMS: To describe the causes of severe visual impairment and blindness in children in schools for the visually handicapped in the Czech Republic in 1998. METHODS: Pupils attending all 10 primary schools for the visually handicapped were examined. A modified WHO/PBL eye examination record for children with blindness and low vision was used. RESULTS: 229 children (146 males and 83 females) aged 6-15 years were included in the study: 47 children had severe visual impairment (20.5%) (visual acuity in their better eye less than 6/60), and 159 were blind (69.5%) (visual acuity in their better eye less than 3/60). Anatomically, the most affected parts of the eye were the retina (124, 54.2%), optic nerve (35, 15.3%), whole globe (25, 10.9%), lens (20, 8.7%), and uvea (12, 5.2%). Aetiologically (timing of insult leading to visual loss), the major cause of visual impairment was retinopathy of prematurity (ROP) (96, 41.9 %), followed by abnormalities of unknown timing of insult (97, 42.4%), and hereditary disease (21, 9.2%). In 90 children (40%), additional disabilities were present: mental disability (36, 16%), physical handicap (16, 7%), and/or a combination of both (19, 8%). It was estimated that 127 children (56%) suffer from visual impairment caused by potentially preventable and/or treatable conditions (for example, ROP, cataract, glaucoma). CONCLUSIONS: Establishing a study group for comprehensive evaluation of causes of visual handicap in children in the Czech Republic, as well as for detailed analysis of present practice of screening for ROP was recommended.

Adolescent↗
PubMed2003

Causes and temporal trends of blindness and severe visual impairment in children in schools for the blind in North India.

AIMS: To describe the causes of severe visual impairment and blindness (SVI/BL) in children in schools for the blind in north India, and explore temporal trends in the major causes. METHODS: A total of 703 children were examined in 13 blind schools in Delhi. A modified WHO/PBL eye examination record for children with blindness and low vision which included sections on visual acuity, additional non-ocular disabilities, onset of visual loss, the most affected anatomical part of the eye concerning visual impairment, and the aetiological category of the child's disorder based on the timing of insult leading to visual loss was administered in all children. RESULTS: With best correction, 22 (3.1%) were severely visually impaired (visual acuity in the better eye of <6/60) and 628 (89.3%) children were blind (visual acuity in the better eye of <3/60). Anatomical sites of SVI/BL were whole globe in 27.4% children, cornea 21.7%, retina 15.1%, and lens 10.9%. The underlying cause of visual loss was undetermined in 56.5% children (mainly abnormality since birth 42.3% and cataract 8.3%), childhood disorders were responsible in 28.0% (mainly vitamin A deficiency/measles 20.5%), and hereditary factors were identified in 13.4%. Study of temporal trends of SVI/BL by comparing causes in children in three different age groups-5-8 years, 9-12 years, and 13-16 years-suggests that retinal disorders have become more important while childhood onset disorders (particularly vitamin A deficiency) have declined. CONCLUSIONS: Almost half of the children suffered from potentially preventable and/or treatable conditions, with vitamin A deficiency/measles and cataract the leading causes. Retinal disorders seem to be increasing in importance while childhood disorders have declined over a period of 10 years.

Adolescent↗
PubMed2006

Image relocation with prisms in patients with age-related macular degeneration.

BACKGROUND: To determine the benefits of image relocation (IR) with prisms in patients with age-related macular degeneration (AMD). METHODS: This was a retrospective comparative interventional case series of 100 patients with AMD and 5 years of available follow-up records. Participants underwent complete low vision (LV) assessments, including identification of preferred retinal locus (PRL). Prisms were added to prescription glasses to produce IR to the presumed PRL. Main outcome measures were best-corrected visual acuity (BCVA), location of the PRL preferred by the patient for rehabilitation, use of glasses prescribed, and number of prism diopters prescribed. RESULTS: Patients wearing prescribed glasses for distance with prisms for IR showed improved BCVA (t(63) = 9.5, p = 0.001) as did those patients wearing prescribed glasses for distance without prisms for IR (t(14) = 2.25, p = 0.04). Patients wearing prescribed glasses for distance with prisms for IR achieved better BCVA than those patients wearing prescribed glasses for distance without prisms for IR (t(77) = 2.0, p = 0.05). Patients reported using distance glasses with prisms for 3 to 48 months (mean [SD], 8.4 [11.7] mo). Number of prism diopters used (mean [SD], 5.8 [1.9] D) was well tolerated by all patients. PRL preferred by patients was on the upper retina in 98.5% of cases. INTERPRETATION: IR with prisms to PRL in patients with AMD results in a significant and sizable improvement in BCVA. This effect is probably created by facilitation of oculomotor functions resulting from direct reduction of fixation instability.

Aged↗
PubMed2006

Functional field score: the effect of using a Goldmann V-4e isopter instead of a Goldmann III-4e isopter.

PURPOSE: To investigate the underestimation of field loss in functional field score (FFS) between the Goldmann isopters III-4e and V-4e in visually impaired patients, in order to develop a predictive model for the FFS(III-4e) based on FFS(v-4e) that adjusts for possible confounders. Although the visual field is generally evaluated using Goldmann isopter III-4e, it has the disadvantage that not all low-vision patients are able to see the stimulus corresponding to this isopter. METHODS: Goldmann visual fields were obtained from 58 patients with a variety of eye diseases. Eligibility criteria were age of 18 years or older and valid results of a Goldmann III-4e and V-4e visual field test in at least one eye. Linear regression was used to develop the model, setting FFS(III-4e) as the dependent variable and FFS(V-4e) as the independent one. RESULTS: The FFS(V-4e) was higher than the FFS(III-4e), the mean difference being 14.56 points (95% CI, 12.48 -16.64). Multiple linear regression analysis showed that age, functional acuity score, primary eye disease, and central-peripheral loss were not confounders for the prediction of FFS(III-4e). FFS(III-4e) was estimated with the following equation: FFS(III-4e) = -19.25 + 1.063 x FFS(V-4e). CONCLUSIONS: The relationship between FFS(III-4e) and FFS(V-4e) is linear, and the FFS(V-4e) can be used to estimate the FFS(III-4e). In practice, just subtracting 19.25 points of the value of FFS(V-4e) will be sufficient to estimate the value of FFS(III-4e). This model should give confidence about using the bigger isopter for determining the visual impairment of a person by the FFS.

Adult↗
PubMed2006

Visual acuities "hand motion" and "counting fingers" can be quantified with the freiburg visual acuity test.

PURPOSE: The visual acuity (VA) of patients with very low vision is classified using the semiquantitative scale "counting fingers" (CF), "hand motion" (HM), "light perception" (LP), and "no light perception." More quantitative measures would be desirable, especially for clinical studies. The results of clinical VA measurements, Early Treatment Diabetic Retinopathy Study (ETDRS) charts, and the Freiburg Visual Acuity Test (FrACT) were compared. The FrACT is a computerized visual acuity test that can present very large Landolt C optotypes when necessary. METHODS: Examined were 100 eyes of 100 patients with various eye diseases (e.g., diabetic retinopathy, ARMD), covering a range of VAs from LP to decimal 0.32. The FrACT optotypes were presented on a 17-inch LCD monitor with random orientation. After extensive training, two ETDRS and FrACT measurements were obtained. The testing distance was 50 or 100 cm. RESULTS: ETDRS and FrACT coincided closely for VA > or = 0.02 (n = 80). ETDRS measures were successfully obtainable down to CF (at 30 cm; test-retest averaged over all patients, coefficient of variation [CV](ETDRS) = 9% +/- 8%), and FrACT provided reproducible measurements down to HM (test-retest CV(FrACT) =12% +/- 11%). For CF (n = 6), both ETDRS and FrACT resulted in a mean VA of 0.014 +/- 0.003 (range, 0.01-0.02). The VA results of FrACT for HM (n = 12) were 0.005 +/- 0.002 (range, 0.003-0.009); the individual values were highly reproducible. No results were obtainable for LP (n = 2). CONCLUSIONS: The three acuity procedures concur above a VA of 0.02. The results suggest that the category CF at 30 cm can be replaced by 0.014, using ETDRS or FrACT. Using FrACT, one can even reproducibly quantify VA in the HM-range, yielding a mean VA of 0.005.

Adult↗
PubMed1994

Image enhancement for the visually impaired: the effects of enhancement on face recognition.

Image enhancement has been shown to improve face recognition by visually impaired observers. We conducted three experiments in an effort to refine our understanding of the parameters leading to this effect. In experiment 1 we found that the band of spatial frequencies between 4 and 8 cycles/face is critical for face recognition. In experiment 2 we found that enhancement of these frequencies and the resulting image distortion actually reduced recognition performance for normal observers. Since the degradation of performance by low vision is larger than the effect of distortion, the enhancement that reduces performance for normal observers may still be beneficial for the visually impaired observer. Experiment 3 found that patients tend to prefer images enhanced at frequencies higher than the critical frequencies found in experiment 1. Such individually selected enhancement did not improve recognition in comparison with uniformly applied enhancement. The lack of an enhancement effect may be due to the small variability in enhancement frequencies selected by our subject population.

Adult↗
PubMed1995

Fiber-optic reading magnifiers for the visually impaired.

We describe fiber-optic stand magnifiers specifically designed for use as low-vision reading aids. Application of this technology results in better optical and ergonomic properties. The fiber-optic magnifiers (tapers) provide bright, uniformly illuminated, distortion-free images. The reading material can be scanned without the user's having to bend directly over the magnifier. One can further increase the scanning field by slanting the taper to tilt the image toward the observer. Tilting the upper face of the taper by cutting the smaller lower face on a bias is shown to increase the scanning range substantially and to provide better control of illumination. The scanning range of such tilted tapers is approximately double that of the equivalent lens magnifiers. To increase the contrast transfer through the magnifiers, we have developed lower-resolution tapers with an increased core-to-cladding ratio. The increase in contrast transfer is reported for representative tapers. The lower-resolution design is also helpful in reducing the manufacturing cost of taper magnifiers.

Contrast Sensitivity↗