Chapter 3 Priorities and objectives - What do we want to achieve?
3.5.4 Low vision
The following two definitions for low vision are used:
- (WHO) Low vision is visual acuity less than 6/18 and equal to or better than 3/60 in the better eye with best correction.
- (Low Vision Services or Care) a person with low vision is one who has impairment of visual functioning even after treatment and/or standard refractive correction, and has a visual acuity of less than 6/18 to light perception, or a visual field less than 10 degrees from the point of fixation, but who uses, or is potentially able to use, vision for the planning and/or execution of a task for which vision is essential.
Data from the 1994 update of Available data on blindness suggest that the prevalence of low vision is about three times the prevalence of blindness. In 2000, WHO estimated that approximately 135 million people had low vision (VA<6/18 - 3/60 with best correction). This figure is expected to double by the year 2020, due to the rapid growth of the elderly population. An estimated 75% of these people may be helped with cataract surgery and/or correction of refractive errors. The remaining 25-35 million people have eye conditions or diseases that are either incurable (e.g. age-related macular degeneration, albinism), or diseases that - even after treatment - may leave vision reduced (e.g. congenital cataracts, diabetic retinopathy). These constitute the ‘true’ low-vision cases that need low-vision care.
Low-vision services meet the needs of a person with low vision in many
different situations, and may be delivered by personnel with varying professional
backgrounds. Low-vision care cannot be offered in isolation, and should
be part of comprehensive eye services. Another important function of these
services is to act as a bridge between medical, rehabilitative, and educational
programmes.
Low-vision services can be offered at primary, secondary, and tertiary
care levels.
At the primary level, these services involve screening of vision, assessment of functional vision, referral to eye care, and simple advice on environmental modification and non-optical interventions. At the secondary level, these services are offered as part of refractive services and involve assessment of vision, correction of refractive errors, and prescription of optical and non-optical devices. Trained ophthalmic technicians, ophthalmic medical assistants, ophthalmic clinical officers and refractionists offer these services. At the tertiary level, services include specialized low-vision care and involve assessment of visual functions, refraction, prescription of optical, non-optical and electronic devices, training in visual skills, and use of devices.
It is estimated that 30% of people with low vision can be assisted at the primary level, 50% of the need can be met at the secondary level, while 20% will need tertiary-level care. Standard lists of equipment for each level of services are available.
The need for low-vision care in an area can be assessed from blindness surveys, surveys of schools for the blind, blind registries, and estimates of childhood blindness. The following approach is suggested: conduct a situation analysis of the available human resources and infrastructure, as well as the local legislation on rights of and services for disabled persons; identify the gaps between needs and current services; and develop an action plan to bridge those gaps.
Where local expertise is limited, technical assistance could be requested to help with the development of a low-vision service. Low-vision devices can be produced locally at low cost, using appropriate technology and local materials. Such devices could also be acquired at low cost from partner Low Vision Resource Centres. It is equally important to increase awareness and to develop a good network of referrals, so that people in need of low-vision care can access and benefit from available services.
Documents
Asia
Pacific regional low vision workshop
Consultation
and management of low vision in children in Bangkok
Low
vision care for the elderly - report of a workshop
Assessment
of low vision in developing countries - book 2
Articles
The
role of optometry in VISION 2020
Guidelines
for setting up an low vision programme for children
Community
based rehabilitation: an introduction
How
can blind children be helped? (JCEH issue 27)
Low
Vision Care (JCEH issue 49)
Low
Vision Resource Centre, Hong Kong