Are current guidelines for categorization of visual impairment in India appropriate?

CONTEXT

Visual disability in India is categorized based on severity. Sometimes the disabled person does not fit unambiguously into any of the categories.

AIMS

To identify and quantify disability that does not fit in the current classification, and propose a new classification that includes all levels of vision.

SETTINGS AND DESIGN

Retrospective chart review of visual disability awarded in a teaching hospital.

MATERIALS AND METHODS

The last hundred records of patients who had been classified as visually disabled were screened for vision in both eyes and percentage disability awarded. Data were handled in accordance with the Helsinki Declaration.

RESULTS

Twenty-one patients had been classified as having 30% disability, seven each had 40% and 75%, and 65 had 100% disability. Eleven of them did not fall into any of the current categories, forcing the disability board to use its own judgment. There was a tendency to over-grade the disability (seven of 11; 63.6%). The classification proposed by us is based on the national program for control of blindness' definition of normal vision (20/20 to 20/60), low vision ( < 20/60 to 20/200), economic blindness ( < 20/200 to 20/400) and social blindness ( < 20/400). It ranges from the mildest disability (normal vision in one eye, low vision in the other) up to the most severe grade (social blindness in both eyes).

CONCLUSIONS

The current classification of visual disabilities does not include all combinations of vision; some disabled patients cannot be categorized. The classification proposed by us is comprehensive, progresses logically, and follows the definitions of the national program.

Pediatric and adolescent population with visual impairment: study of 385 cases

OBJECTIVE

To analyze data on the pediatric population attending the Ophthalmologic Clinic's Low Vision Service at the São Paulo University Medical School.

METHODS

Low vision ophthalmologic assessment, from April 1998 to December 2003, of 385 children and adolescents with mean age of 7 years; 51.7% males and 48.3% females. The main data analyzed were age, diagnosis, anatomic site of the ocular injury, visual acuity, and prescription of optical aids.

RESULTS

45.4% were below 6 years, and 54.6% were between 6 and 16 years. 35.5% experienced moderate visual impairment, 26% had severe visual impairment, 8.6% had profound visual impairment, 10.6% were near blind, and 1.6% were blind. The main causes of visual impairment included congenital glaucoma (30.6%), macular retinochoroiditis due to congenital toxoplasmosis (16.7%), congenital cataract (12.8%), retinal and macular inherited disorders (11.7%), and optic atrophy (9.8%). Among school-age children, 52.9% received a prescription of optical aids. The most widely used optical aids for distance were 2.8 X 26 (34.4%); 4.2 X 12 (30.3%); and 6 X 17 (26.8%) telescopic systems. The most frequently prescribed optical aid for near vision was the 2x magnifying bar (33.3%).

CONCLUSIONS

There is a need for prevention of primary (congenital infections), secondary (congenital glaucoma and retinopathy of prematurity), and tertiary (congenital cataract) visual impairment. The prescription of optical aids for school-age children will help them perform better at school and contribute to their social inclusion.

What is low vision? A re-evaluation of definitions

PURPOSE

To re-evaluate definitions of low vision, visual impairment, and disability.

METHODS

We review current definitions of legal blindness and low vision and how these definitions are variably based on disability or impairment. We argue for a definite distinction being made between criteria for visual impairment and visual disability, low vision being defined as the presence of a visual impairment that results in a disability. Visual impairment is defined according to population norms and a statistical cut-off is used. Visual disability is defined by consideration of the level of visual measures which result in measurable or reportable disability. We consider the evidence that contrast sensitivity should be a criterion for visual disability in addition to visual acuity and visual field.

CONCLUSIONS

According to the current information, we define visual impairment as best monocular or binocular visual acuity <(worse than) 6/7.5, total horizontal visual field <146 degrees (Goldmann III-4e) or <109 degrees (III-3e), and contrast sensitivity <1.5 (PelliRobson); we define visual disability as best monocular or binocular visual acuity <6/12 or contrast sensitivity <1.05.

[Borderline blindness, practical blindness and severe visual debility]

In the presented paper the author explains assessment aspect of social welfare departments as regard evaluation of complete of practical blindness with reference to generally blinding legal regulations. The author draws attention to another interpretation not consistent with these regulations, in chapter 26 of the Compendium of Ophthalmology (Grada 1997) and recommends ophthalmologists to use a procedure which will prevent imminent difficulties which could arise as a result of the interpretation in chapter 26 of the Compendium.

[The low vision cyclist: handicapped orientation and assessment with the nystagmogram]

BACKGROUND

Visually impaired individuals who are unable to obtain a driving licence may use a bicycle and feel fit for traffic as part of this "bio-physical model".

MATERIALS AND METHODS

Five nystagmic amblyopes who claimed to ride a bicycle were tested in respect to visual acuity, peripheral vision and oculomotor functions. In three of these cases visual acuity amounted to 0.3, in one to 0.6, in another one only to 1/35. Eye movements were recorded by electro-oculography. The following qualities of gaze were determined: Fixation-saccadic eye movements-pursuit eye movements-behaviour in light and dark-vestibulo-optokinetic movements-eye positioning in resting states and influence of mood.

RESULTS

In four of the cases oculomotor regularities were found. These were explained to the patients. One of the cases was affected with a form of chaotic nystagmus.

CONCLUSION

Bicycling demands on both the vestibular and the visual system. Deficiencies relevant to behaviour in traffic and the possibilities to compensate for these may be estimated based on a oculographic evaluation. This should therefore be used to advise bicyclists with a visual impairment.

Basic concepts and terms for low vision rehabilitation

As the involvement of occupational therapists in the rehabilitation of people with visual impairments increases, it is important for all professionals involved to communicate clearly by using the most accurate terminology. This article suggests the most appropriate use of terms and concepts. It recommends that the distinctions between the various aspects of vision loss be recognized and that the old dichotomy of legally blind versus legally sighted be replaced by the more detailed classification of the International Classification of Diseases, 9th revision, Clinical Modification (ICD-9-CM), which recognizes multiple levels of visual performance.

Clinical low vision resource usage prediction

In an era of increased demands and constrained budgets, it is necessary to make the best use of all available resources. This is difficult when specialized vision care, such as low vision clinical assessment, is involved because of the heterogeneity of the patient populations seen by such clinics. PURPOSE. This research attempts to discover if these diverse patient populations can be identified and clustered into groups based upon similarity of clinical resources use. Specifically, the inquiry examines the potential for a low vision patient resource utilization classification scheme at the Low Vision Clinic (LVC) in the Centre for Sight Enhancement (CSE), University of Waterloo. METHODS. From a sample of 99 patients consulting the LVC in a 3-month period, retrospective data collection involved abstracting and coding medical records containing information detailing each patient's demographic, diagnostic, therapeutic, and resource utilization characteristics. Cluster analysis using Hartigan's block clustering algorithm was then applied to the data. A replication study was completed using a sample of 99 patients visiting the LVC 1 year later. RESULTS. Patients can be classified into five iso-resource groups, hereby termed low vision patient resource groups (LVPRGs). The clusters represent a resource consistent and clinically coherent scheme for classifying low vision patients based upon resource requirements. As a measure of repeatability, the groups reemerged in the replication study. CONCLUSIONS. If the groupings demonstrate robustness in a field test, clustering algorithms in general, and LVPRGs in specific, may offer useful tools to enhance resource utilization in the LVC setting.

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.

Towards a classification of visual impairment

For the rehabilitation of people with impaired vision, it is essential to have adequate (preferably quantitative) information about their residual visual functions. Special attention is given to the extra information provided by the results of measurement of the contrast sensitivity, especially in combination with the results of other measurements, such as the visual field, the amount of intraocular straylight and the visual acuity. The value of the contrast sensitivity function as a predictor of the extent of dysfunctioning in the visual activities of everyday life, such as outdoor vision, reading and recognition of faces, will be discussed. As far as this is concerned, a comparison is made between the value of visual acuity and contrast sensitivity as measures of the extent of vision and visual dysfunctioning.