by Michelle Ntlakana, College of Orientation and Mobility, SA Guide-dogs Association
What is low vision?
Low vision is the loss of sight that cannot be corrected with the assistance of prescription eyeglasses, contact lenses, or surgery. It is often termed “partial vision” as there is some usable vision available although it may be blurred. There may be blind spots or only a small tunnel of vision. Depth perception is often limited, and judging distances is difficult. The amount of vision available for use may vary widely for each person and it can change depending on factors such as health or stress levels. Low vision can affect anyone, from babies to the elderly.
How is low vision different from being blind?
A person who is blind, is without sight. He or she might have some light perception to differentiate day and night. Low vision implies that there is still vision, but it is limited in some way. Very often the visual field is limited. An example of this can be where a person is able to see objects that are to his or her side whilst seeing what is straight ahead might be limited. The vision remaining may also be limited to seeing items really close up, meaning their visual acuity is limited. Acuity refers to seeing the shapes and details of items clearly at a specific distance.
What causes low vision?
The most common causes of low vision are related to disease or eye conditions. These can be genetic, caused by trauma, lifestyle, aging or hereditary. Some conditions are degenerative and will result in complete blindness. The most common causes of low vision include:
- Glaucoma (causes loss of peripheral vision)
- Diabetic Retinopathy (causes patchy vision which can result in blindness)
- Age Related Macular Degeneration (initially causes loss in central vision)
- Retinitis Pigmentosa (causes loss of peripheral vision, creating tunnel vision)
- Hemianopsia (caused by stroke, trauma and brain tumours. Leads to loss of vision on one side of the eye)
How is low vision tested?
A low vision eye examination is different to a normal eye examination and is carried out by an optometrist who specialises in low vision. Although the optometrist may use refraction testing to see if a prescription is needed, the focus is on how the visual impairment affects daily life. A variety of tests are used to determine the extent of usable sight available, but questions relating to how the person sees in certain situations (going from light to dark, the ability to see faces, travelling at night and driving) are important. Questions also relate to managing everyday tasks like dressing, cooking and shopping. The optometrist will prescribe tools to enhance the use of the remaining vision, such as magnifiers and lighting. The patient might also be referred to an Orientation and Mobility Practitioner for additional training and assistance.
How does an Orientation and Mobility Practitioner assist a person with low vision?
Practitioners can:
- educate the client and the family/caregiver to better understand the client’s eye condition.
- identify areas in the home which can be modified to improve safety. This includes the use of coloured tape to mark changes in surface level.
- enhance the client’s ability to perform daily tasks such as cooking by marking stove knobs with tactile markings or teaching alternative methods of cleaning that don’t depend on sight.
- teach the client a variety of visual skills to enable him or her to make the best use of the remaining vision. These include using scanning to read and watch television.
- teach orientation and enhance mobility skills by using visual skills and by teaching the client how to use a long cane.
- provide a symbol cane if one is required. This is an outwards symbol to tell others that the person has a visual impairment.
- assist by evaluating the task and general lighting in the home and make suggestions for improvement.
- explain and demonstrate the effectiveness of contrast, such as placing a using a coloured bathmat on a white tiled bathroom floor to see the edge of the bath.
- refer clients to low vision clinics, and indicate where to purchase assistive devises and optical aids
- demonstrate how to use magnifiers or other optical aids correctly in the client’s own environment.
How do we train our Orientation and Mobility students to assist low vision clients?
Our Orientation and Mobility students are trained to work with low vision clients of all ages. These students undergo theoretical training where they learn about the different eye conditions that cause low vision. They are taught how to do a low vision assessment (using a low vision kit) as well as how to assess the client’s environment. Low vision simulators are used to understand how different eye conditions affect the performance of daily tasks and these are then used to learn the low vision skills. This experience helps them to understand that the low vision skills do work and to problem solve when they do their practical training in the community.
How can you assist a person with low vision?
Deteriorating vision can be very scary and many people will deny that they have any problems until they have a serious fall, burn themselves or are involved in a car accident. Speak to the person in a kind and caring way to express your concern for their safety and well-being. It may take many months of talking before the person eventually agrees to receive assistance.
The first step is to have the person’s vision assessed by an optometrist specialising in low vision. The next step will be to contact our Support Team of Orientation and Mobility Practitioners. A Practitioner will do a home visit and assessment. Our services are free of charge and take place in the client’s home environment.
RESOURCE
Friends in Harness, Number 2, 2020