CHANGES IN VISION IN OLD AGE

In the everyday work of medical doctors and clinical psychologists vision plays a central role. Numerous tests are visual, our communication is strongly visual and when we observe the behaviour of a person we depend on the visual cues more than on the use of voice. In all these areas visual impairment or improper glasses cause misunderstandings that we should learn to avoid.

Disorders may cause mild, moderate or severe loss of visual functioning in central or peripheral vision, at high or low contrast, cause loss of visual function at low luminance level or photofobia. The visual problem itself needs to be evaluated in the beginning of the assessment.

When trying to improve the services, we may tackle the common errors and misunderstandings in psychological testing that we see today:

1. Testing at improper distance where glasses do not work
2. Use of too small test pictures or too small critical details
3. Use of tests with low contrast information when the client does not see at low contrast
4. Communication problems related to glasses, field defects or eccentric fixation.

All this may lead to that the role of vision in the decrease of independence is over- or underestimated, the need for and value of rehabilitation is not understood and the client may be made more visually disabled than s/he is or is reported as intellectually deficient when the test material was not adapted to the visual needs of the client.

The ageing eye and the visual pathways
The changes typical to ageing occur in all parts of the long optical-neural path of visual information.

Presbyopia, decrease in the focusing power of the lens leads to the need of reading glasses except when the person is suitably near sighted in one or both eyes. If one eye is suitably nearsighted and the other eye slightly farsighted, no glasses are needed even by a senior person.

Spectacles of the client may correct the refractive error properly or may be under- or overcorrected because of changes in the refractive power of the eyes after the glasses were prescribed.

Quite often cataractous changes begin with change of refraction toward myopia. Then the person notices that s/he can read with the former distance glasses and later without any glasses if s/he was previously hyperopic. A previously mildly near sighted person who could read comfortably without glasses notices that s/he must hold the text closer to the eye or start using former distance correction to read, which to near sighted person may be difficult to accept after a life long habit of reading without glasses.

To be assessed:
Before using any visual tests, measure visual acuity at distance and at near using the current spectacle correction and without it. If the client sees sufficiently well at the test distance use the visual tests, if not, get the client’s vision examined to get proper correction. If vision cannot be improved with glasses modify the tests to meet the needs of the client.

Reading lenses either have one correction or they are weaker in the upper part allowing a wider range of clear vision. If the person uses progressive, bifocal or trifocal correction, s/he sees clearly at certain distances.

To be assessed:
Make sure that you know at which distance the image is clearest. Test at that distance. If the person uses single power reading glasses, remember that through those lenses s/he may not see your facial expressions clearly enough

Cataract, cloudiness of the lens or colour change of the lens toward coffee brown, becomes common in the age group >65 years. Slight cloudiness causes dispersion of light and thus photofobia and loss of image quality when light is falling on the eyes. If the person can still read comfortably and get by in the daily tasks, s/he may not be interested in cataract operation although it nowadays is an easy and short operation. Beginning cataract may decrease vision at low contrasts more than at high contrasts. This affects visual communication, because facial expressions are faint shadows, and it affects mobility because stairs and curbs are also low contrast information.

To be assessed:
Measure contrast sensitivity briefly to find how low contrast details can be seen at the test distance.

Age related macular degeneration is the most common cause of severe vision loss in the elderly population. Depending on the size of the lesion, either only the very central visual field is lost (central scotoma) or larger areas to nearly the entire field is lost. If the central scotoma is small, peripheral vision may be normal and thus mobility and every day tasks are only slightly affected although reading and other sustained near vision tasks may require strong near corrections using either magnifiers, strong reading glasses or closed circuit TV reading aid, CCTV.

When testing such a person, it is important to remember that magnifying devices decrease the area seen and thus it is difficult to get an overview. It is also important to notice how well the person uses the devices. If s/he is not yet accustomed to use them, using them in a stressful test situation may lead to frustration and anxiety.

Vascular accidents in the retina or visual pathways cause patchy, sectorial or half field defects in the visual field. These may not be diagnosed for months or years if visual functions are not decreased so much that it would disturb the daily activities.

Glaucomatous field loss also develops so symptom free that most of the visual field may be lost before the person becomes subjectively aware of it. Side vision is easy to examine with confrontation or finger perimetry. It is important not to confuse visual field defects with attentional deficits.

Inherited retinal degenerations often have lead to loss of most of the visual field, with a small tubular fields remaining. Because the change is slow these persons usually have learned blind persons’ mobility techniques and compensatory techniques in ADL and sustained near vision tasks. These persons may have nystagmus that disturbs communication if the doctor or the psychologist is not accustomed to work with the visually impaired (i.e. this is tester’s problem, not that of the client). Some of them have lost central vision and have to use eccentric or parafoveal area for looking at. Then they seem to look past you when they are looking at you. This should not be interpreted as "avoiding eye contact".

Agnosias are far more common than they are diagnosed. Facial recognition, recognition of expressions, sizes, directions etc. should be looked for. When testing perception of expressions it is important to find out whether loss of contrast sensitivity plays a role (Heidi Expressions).

Illusion caused by retinal lesions vary and should not be confused with hallucinations. Macular degeneration or diffuse retinal degeneration does not lead to loss of all cells in the scotomatous area. Function in the damaged cells causes activity in the visual pathways and the brain interprets it as visual images. These images may be simple glowing lights or they may be vivid images, pleasant or unpleasant. (A patient of mine asked me recently whether I could change his constantly visible illusion of street cars to something more fun, because his sisters see flowers). If the illusion is scary it may disturb especially a person with dementia or low intelligence because s/he may not understand the illusory nature of the phenomenon.

Coping with visual impairment varies as much as coping strategies in all problem situations. There are totally blind persons who are well adjusted and, by using specific techniques, lead a normal life. On the other hand there are rather mildly visually impaired or not at all impaired persons who experience their vision poor. Quite often the client understood the doctor’s notion of "ten percent of vision left" so that nearly all vision is lost when only the reading vision is affected. Therefore it is always important to compare the subjectively experienced disability with functional disability observed in different tasks.

Functionally, vision is important in four main areas:

• communication,
• orientation and mobility,
• activities of daily living (ADL) and
• sustained near vision tasks.

In each of these functional areas the person may use techniques of blind or those of low vision persons or those typical to fully sighted. Use of sighted techniques is no "better" than use of blind techniques. What is important, is to find out, whether the person has learned to use the techniques that s/he needs to use, how independent s/he is in the different functional areas. If there is loss of independence, then either the technique has to be trained or the function taken care of by supportive services.

If the doctor or the psychologist is not accustomed to work with visually impaired persons it is wise to consult the local low vision team and/or the client’s ophthalmologist and optometrist. When ever you notice visual disability you should remember to ask whether the client is getting vision rehabilitation services. Local rehabilitation services are a good source of additional information related to the special needs and services of visually impaired elderly persons.

Working together with the rehabilitation services you get accustomed to see the effect of impaired vision on the overall functioning and how it is compensated. Then its role in the life of the client can be correctly evaluated and its effect on testing compensated by suitable adjustment of the tests and test situations.