Low Vision Aids in AMD

›Age-related macular degeneration leads to a loss of reading ability as a result of a central scotoma; however, it never results in complete blindness.

›The prescription of low vision aids is based on comprehensive measurement of visual acuity including inquiry into the needed magnification.

›Besides a huge number of optical low vision aids like magnifying glasses, spectacles and telescope systems, above all CCTVs are used for patients suffering from advanced functional impairment.

›Now also hand-held electronic low vision aids (LVAs) have become available.

›Television is important for the older visually impaired; here a shortening of the distance or a bigger television screen is often helpful.

›Complementary aids like a lectern or lighting are very important.

›Low vision rehabilitation is time consuming and requires experience. Nevertheless, in most cases the reading ability is accessible with simple LVAs and thus allows protecting independence of living.

K. Rohrschneider

Department of Ophthalmology, University of Heidelberg, Heidelberg, Germany

e-mail: kr@uni-hd.de

“Visual impairment” is the summarization of any impairment of the visual function of the eye following the best possible refractive correction by means of glasses or contact lenses. The degree of visual impairment depends on the cause and location of the eye disease. It is generally assessed by visual acuity in the distance, although consideration of other visual functions may also be important (Table 20.1) [1].

There are so many different definitions of visual impairment or even blindness in most countries that it is not possible to define a single one that can be universally adopted. The World Health Organization has provided a notation for classification of visual acuity, which is comparable to the German classification: categories 1–3 define low vision with reduction of visual acuity to less than 0.3, 0.1 and 0.05 (6/18, 6/60, 3/60), respectively (Table 20.1). Virtual blindness is present with a reduction of visual acuity to 0.05 (1/20), which is not as strong as the German legal definition of blindness with visual acuity 1/50 or less. However, a person will already be considered legally blind in countries such as the USA when his visual acuity is reduced to 20/200 in the better eye or if a visual field constriction of 10° or less in Goldmann perimetry is present. Furthermore, in Germany, patients with a visual acuity reduction to 0.3 or less are considered to be legally disabled.

Distance visual acuity is not the only criterion defining visual impairment. Other visual functions such as reading behaviour, visual field, mesopic functioning, color vision and contrast sensitivity also need to be taken into consideration and comparable gradings have to be found for them. For a successful visual rehabilitation of the elderly visually impaired, near visual acuity

Table 20.1 World Health Organization notation for classification of visual acuity

and reading ability in addition to visual field and photophobia caused by glare are most relevant.

20.2Effects of Visual Impairment in AMD

The functional damage in age-related macular degeneration (AMD) is characterized by a functional loss in the central visual field, so that the recognizing and reading ability are limited or lost. The peripheral visual field with its lower resolution is important for orientation purposes as well as for detection of movement. Patients with AMD will keep these functions for life. The remaining ability to detect movement enables these patients to move freely at home or in familiar surroundings, and after some special training also allows them to venture into the wider vicinty. Patients with AMD will never become completely blind.

The duration of the habituation phase varies. During this time it is of the utmost importance to counsel the patient with regard to his diagnosis, on the implications of his visual impairment, on how to regain his independence and on which visual aids are available for him. Thereafter, it is absolutely vital that the visually impaired familiarizes himself with his low vision aids, accepts the suggested aids and applies them frequently. This

process requires a lot of patient compliance, patience and a considerable amount of time. The elderly low vision patient will only accept being dependent on visual aids with a tremendous effort. This is mostly the case when medication as well as surgical approaches have failed. The acceptance of being visually impaired needs more time with increasing age. Fear of further increasing loss of vision should not be allowed to depress the patient or to stop him in his daily activities.

In addition to other therapeutic measures, the ophthalmologist plays an important role by alleviating the elderly visually impaired patient’s fear of becoming blind, enabling him to use his remaining visual function in a positive way and supporting his motivation to keep active and apply his low vision aids [2–4].

In patients suffering from AMD, visual acuity is reduced not only for far distances, but also for near sight. Objects at varying distances cannot be fixated on, and traffic lights, bus line numbers, street signs and faces cannot be recognized. The main handicap, however, is caused by the loss of reading ability. Headlines in the newspaper can be read, but not the articles below them. For most patients it is impossible to read their daily mail and TV journals, bills or bank account statements. Reduced near visual acuity also affects housekeeping, shopping and participation in certain hobbies.

Due to the demographic development an increasing number of elderly to very old visually impaired patients need to be provided with visual aids [5]. A certain degree of autonomy can be achieved by the use of optical and electronic visual aids. It is beneficial for the patient that there are a multitude of devices available to ensure that the visually impaired will be provided with the correct visual aid for each of the diverse and differing “visual tasks”. The wide choice of aids is an advantage, offering equipment for various visual tasks [3, 4, 6].

20.3Choosing the Required Magnification

Reading text has to be adapted to the reduced acuity as well as to the extent of the central scotoma. This means that fonts have to be enlarged accordingly. In most cases the required magnification can be easily assessed with the appropriate reading chart. Charts are available from different manufacturers, such as Keeler, Schweizer, Zeiss and others. At a defined distance of 25 cm, the magnification can be evaluated very easily.