Reading examples in the form of newspaper print are available at magnifications from 1.25 up to 20 times. The required magnification may be directly obtained from the charts. For this distance, older low vision patients have to have their vision corrected with a +4 D lens. Each eye has to be evaluated separately because the eye with formerly lower visual acuity may be used for reading at a later stage.

Furthermore it is important that continuous text phrases are read. Testing distance visual acuity with single optotypes provides no information concerning reading ability. If the patient can only identify single characters it is of no use to supply him with a low vision aid (LVA) meant for reading whole text passages. If only single optotypes can be detected because of the visual field, the aid will only allow reading by spelling, or it may allow recognition of numbers, e.g., during shopping.

20.4Methods of Magnification

Basically, there are three ways of magnifying:

•The simplest method of magnification is achieved by reducing the distance to the object. This is only possible if the ability of accommodation is sufficient, meaning only in children, adolescents, and myopic patients.

•The next option requires enlarging of the text itself. Large-print books are offered by many publishers. In addition, some copy machines offer progressive magnification of texts, making forms, schoolbooks, important documents as well as drug descriptions, directions for the use of appliances and recipes for cooking readable.

•The third possibility of magnification is provided by magnifying optics placed between the text and the eye, such as lenses with positive refraction, e.g., magnifiers, single or multifocal glasses, or Galilean or Kepler systems integrated into spectacles. In addition, optoelectronic systems are available.

To compare various magnifying LVAs, it is helpful

to know their nominal magnification (M), which can be calculated in a simpler way for magnifiers from their refractive power (P):

M = P(D)/ 4.

Therefore, a two times magnification can be achieved with a magnifier of 8 D or by reducing the

distance toward the object by half with regard to the reference viewing distance of 25 cm.

Vice versa, the reading distance (L) in meters can be calculated as follows:

L = 1 / P(D).

This nominal magnification only applies under the conditions mentioned above, which can rarely be maintained in practice, particularly for magnifiers. This is only possible when the back vertex of the magnifier and the anterior principal meridian of the eye coincide, and impossible when using a hand or stand magnifier. Usually, the real magnification of a low vision aid will be below the nominal magnification and mostly amount to about double the magnification [7]. This has to be considered when calculating the magnification need. A comparison between different magnifiers should therefore consider the power. In addition, the linear field of view of the magnifier will be reduced because of the magnification.

20.5Optical Magnifying Visual Aids for Distance

Galilean or Kepler-type telescopes are used for distance magnification. The Galilean telescope consists of an objective with positive and an eyepiece with negative refractive power. In this way, upright images are generated. Galilean telescopes offer distance magnification between 2 and 2.5 times (opera glasses).

In the Kepler-type telescope both the objective and the eyepiece possess positive refractive power, and the upside-down image has to be mirrored by erecting prisms. In 1970 it became possible to construct sys- tem-shortening erectors, the Kepler-type telescope became available in a handy size. The main advantage of the Kepler telescope compared to the Galilean system is its higher magnification of 3.5- to 4-fold for distant objects.

Low vision patients are mainly equipped with monocular vision aids, equipment of binocular aids is rare. The monocular system is easier to handle and can be set up faster for the visually impaired. The more complicated binocular adjustment – which is hard to accomplish for a visually impaired patient – is no longer necessary. Elderly low vision patients with advanced AMD seldom retain their binocular vision.

Monoculars are offered by numerous companies with distance magnifications of 2, 3, 4, 6, 8 up to 10 times, and offer variable adjustment from 25 cm up to infinite.

Advantages: Monoculars increase independence and support mobility. They enable visualization of traffic lights and signs, street signs, numbers on bus lines and time tables. They can be used for window shopping, following slide shows or admiring the objects of an art exhibition.

Disadvantages: Elderly visually disabled patients may often experience problems regarding adjustments; they are too impatient. This is why over-focusing occurs. In addition, many visually impaired patients are not able to shut only one eye. The central scotoma may be so large that it is impossible to find the effective center of the telescope. When the older patient finally has managed to find it, it may take quite some time to spot the object for which he or she was searching for. Another disadvantage is the onset of a slight tremor with advanced age as well as the inability to hold one’s arms still.

Recommendations include prolonged testing, using a borrowed monocular for a longer period of time and starting with a clearly defined distance adjustment for a specific visual task.

by 1.5–1.8 times when placed in front of the television set. Unfortunately, they have only been useful in a few cases over the years because of the reduction of contrast and luminance.

•Galilean systems. The Galilean telescope offers magnification for distances of between 1.8 and 2.5 times. Several of these telescopes adjusted for infinity can be tuned for distances of 3, 2 or 1 m, or the system designed for infinity can be altered for close use by means of supplementary stick-on lenses. Also a binocular option is possible.

•TV glasses. Ready-made glasses for TV magnification are commercially available and offer binocular magnification of between two and three times.

•Kepler systems. Kepler telescopes with distance magnification of 3.8 can also be manually adjusted for use at distances of 3, 2 or 1 m by means of reading caps for the desired distance. It should be carefully evaluated if the use of a binocular Kepler telescope is of advantage as it may weigh up to 88 g.

Examination of binocular vision will show if a bin-

ocular fitting is of advantage. The low vision patient suffering from AMD should be advised to measure the distance to the TV set exactly, as his optical aid will be adapted accordingly. This distance must be measured precisely with a tape measure as elderly visually disabled patients easily tend to misjudge distances.

20.5.1 Aids for Watching Television

In addition to newspapers and radio broadcasts, television presents the essential source of information for the elderly visually disabled. Most patients dearly wish to improve the quality of their television picture. Unfortunately, this is rarely discussed during consultations; therefore, it is necessary to ask the patient about this. Surprisingly, for the patients watching television is often more important than reading. Hence, couselling should also take place addressing these problems. However, nowadays it is possible to solve this problem by buying a television with a large flat-screen.

Other possibilities of enlargement:

•Reducing the viewing distance. First of all, the visually disabled elderly patient should be advised to reduce the viewing distance, e.g., moving closer to the television set to a distance of 3, 2 or even 1 m.

•Optical magnification. Large Fresnel panes have long been available. These magnify the TV image

20.6Optical Magnifiers for Short Distance

Due to the decreasing accommodation range of elderly low vision patients, it might be difficult to achieve magnification by reducing the distance towards the object. In this situation, lenses with positive refractive power such as magnifying glasses and magnifiers may compensate the lack of accommodation. (Table 20.2).

•Spectacle magnifiers. Magnifying add-ons also called spectacle magnifiers start at +4.0 D and above.

•Bifocal spectacle magnifiers. Spectacles with addons between 6 and 16.0 D (magnification of 1.5–4 times, by Zeiss) or up to +36.0 D (9 times, by Keeler) are only accepted by younger patients.

•Unifocal spectacle magnifiers. Elderly low vision patients basically prefer a larger homogenous field of view using the magnifier. This is the reason for

Table 20.2 Low vision aids for near distance

Low vision aids for near distance

•Books with large print

•Magnified copies

Optic magnifying aids

•Magnifiers

•Hand magnifiers

•Stand magnifiers

•Stand-on magnifiers

•Illuminated magnifiers

•Foldable magnifiers

•Hang around magnifiers

•Head monted magnifiers

•Clip-on magnifiers

•Illuminated stand magnifiers

Add-ons, glass-mounted magnifiers

•Unifocal spectacle magnifiers

•Hyperocular

•Half-eye magnifying spectacle

•Bifocal spectacle magnifiers

Spectacle magnifiers

•Galilean spectacle magnifiers

•Kepler spectacle magnifiers

Electronic magnifying aids

•CCTVs

•Small handheld electronic reading aids

the frequent application of unifocal spectacle magnifiers up to 16.0 D (magnification 4 times) in patients with AMD (Fig. 20.1). The advantage of these spectacle magnifiers with low-distance addons is the option of correcting astigmatism. By combining an additional astigmatic correction lens with the sphere, contrast enhancement is achieved. Unifocal lenses starting from 16.0 D are available as so-called hyperoculars (aspherical synthetic lenses) up to 48.0 D (magnification of 4 up to 12 times) (Fig. 20.1).

•Half-eye magnifying spectacles. With existing binocular vision, the add-on for near distance with up to 12.0 D (magnification 3 times, binocular) may be prescribed as a half-eye magnifying spectacle with convergence prisms, base-in. As a basic rule, the power of the convergence prism is always prescribed 2 D stronger on each side than the spherical diopters of the low-distance add-on. With double magnification (8.0 D) 10 D of the prism base of the convergence prism has to be integrated

Fig. 20.1 Low vision patient reading with hyperocular magnifying spectacles

on each side. While ready-made products are available, most of them cannot be advised. Not only must the convergence prisms be evaluated individually, but also the pupillary distance (PD) is different in each patient and has an influence on convergence.

Advantages: The linear field of view is rather wide and hands can be kept free for use. The synthetic lenses are light and the spectacles themselves are cosmetically unobtrusive. Another advantage is mobility; the spectacles can be taken anywhere. Unifocal lenses can also be offered as half-eye magnifying spectacles (smaller frame) with a unifocal lens for the reading eye and an opaque lens for the other.

Disadvantages: One certain disadvantage is the short reading distance. This may prove strenuous for the elderly low vision patient and requires concentration. A hand tremor must be absent. Unifocal lens fitting can only be performed monocularly. The lens of the other eye or at least 2/3 of it in the lower area must be opaque for far distance correction. In this way, quick orientation concerning the surroundings is possible upon upward gaze.

Fig. 20.2 Hand magnifier (with illumination)

•Magnifiers. The use of a variety of magnifiers−lenses with positive refractive power−has become very widespread. In the past, they were made from glass and had a low magnification (e.g., stamp collectors’ magnifiers). Nowadays they are only available in the form of synthetic materials, and therefore lighter and offering higher magnification. Thanks to further improvements during the past decades magnifiers can be used for numerous visual tasks. It is important for the ophthalmologist to have detailed information on the wide variety of magnifiers to be able to offer the low vision patient one with the appropriate magnification for the desired task. On offer are hand magnifiers, stand magnifiers, hang-around magnifiers,

add-ons, reading caps and illuminated magnifiers, as well as a choice between conventional and halogen lighting. Both types of illumination can be powered by batteries, accumulators or electricity. Recently, magnifiers with LEDs as a light source have been introduced; these are supposed to last longer and have a lower energy consumption (e.g., Eschenbach, Schweizer). Magnifiers with electronic controls offer individually adjustable light intensities. Magnification of between 1.2 and 20 times is possible, but one should remember that the higher the chosen magnification, the smaller the linear field of view becomes.

Counselling AMD-patients and gathering their complete medical history can be very time-consuming. Questions like: Was the low vision patient able to read in the past? Did he read regularly? How is his

Fig. 20.3 Illuminated stand magnifier

motivation? This is important information because even when supplying the best suitable LVAs, reading remains strenuous and troublesome. The patient has to be informed that fluent reading will no longer be achievable. With this information, the elderly low vision patient will often not want an aid for longer reading periods, but only for quick reading, a special visual task or, in addition, as a mobile aid supplementary to a CCTV system. The magnifier has to be selected according to these considerations. Hand-, stand-, add-on or illuminated magnifiers (Figs. 20.2 and 20.3) can be used for reading everyday mail, newspaper articles, radio and TV magazines, bank statements and even books. Add-ons, such as magnifying clips to attach to glasses (Fig. 20.4) or hang-around magnifiers can be a great support in domestic work, in the kitchen and for nail care, and they may even facilitate participation in dice, board and card games [6, 8].

Folding magnifiers and illuminated pocket magnifiers prove helpful when the patient uses switches on ovens or washing machines, or even outside the home for reading price tags, menus or door signs. For elderly visually disabled patients who require stronger magnification, aids with magnification of ten times or more can be used for a short time. Magnifying heads of illuminated magnifiers with a battery handle can be exchanged quickly, allowing the patient to easily switch between various magnifications.

Advantages: Magnifiers are easy to use at any time and rather discrete. They are fully accepted socially. As magnifiers require little space, they are easy to take along. In addition, they are not expensive, and can be prescribed in various designs and numerous magnification levels.

Disadvantages: One disadvantage of hand-held magnifiers is that the distance to the printed media is not stable. There must be no hand tremor. A disadvantage of stand and illuminated magnifiers is that they have to be moved constantly so that the hand tires rather quickly.

Specialties: Visually disabled patients with AMD and discrete opacification of the optic media may often cope better without illumination, or require illumination that can be adjusted. The majority of illuminated magnifiers offer individual adjustment of the light intensity by means of a small switch integrated into the magnifier’s handle. If overhead illumination is pre-

ferred, a low-reflective coating of the magnifier to avoid annoying light reflection is of advantage. Attention must be paid to the fact that the patient needs to practice using the magnifier. This requires time as well as patience, because using. a magnifier without training will prove to be very frustrating and offer no help at all. The visually impaired often tend to use a magnifier at too far a distance, which will in return lead to a smaller linear field of view.

If the patients themselves buy magnifiers, they are often chosen with a large diameter and low magnification. However, reading ability can only be achieved by evaluating the magnification need for each patient individually. Elderly visually disabled persons need to be informed about the extent of their central visual field defect, the importance of the magnification factor and how to read with a low vision aid. In addition, training in the use of the aid is advisable and very helpful as the patient learns to accept it and uses it more frequently.

•Galilean and Kepler telescopes. If the reading or working distances are too short, systems like Galilean and Kepler spectacle telescopes can be offered (Table 20.2). Galilean magnifiers offer distance magnification of between 1.8 and 2.5 times. These telescopes can be converted into telescope magnifying glasses by clipping on a lens with positive refractive power (Fig. 20.5). Galilean spectacle telescopes have been in service for low vision

Fig. 20.5 Galilean spectacle telescope with reading cap

rehabilitation since the beginning of the twentieth century.

Kepler telescopes offer distance magnification of 3.8 times and can be converted into Kepler near vision telescopes by attaching a reading cap with positive refractive power. Kepler systems have been on the market as visual aids for low vision patients since 1975. Since the technically successful production of mini-prisms, it is possible to offer the Kepler telescope in such a small size that it may also be integrated into a spectacle frame (Fig. 20.6).

As total magnification is calculated from the product of the magnification of the reading cap and the magnification of the telescope, the working distance lengthens proportionally so that the magnification of the telescope changes in comparison to total magnification. If the total magnification remains the same, the Galilean system with its lower distance magnification needs a higher magnification of the reading cap and this results in a lower focal length. For close distances,

magnification up to 12 times with a working distance of 8.5 cm from the eye may be reached. In contrast to this, the magnification factor of the additional reading cap of the Kepler telescopes is lower, the focal length is higher, resulting in an increased working distance. (Fig. 20.6). To achieve a longer working distance, the Kepler telescope is offered for the near range with a magnification of up to 20 times which means a working distance of 11 cm. The advantages of the Kepler telescope are the long working distance, the excellent quality of focus as well as the option of offering higher magnification factors.

Older low vision patients often struggle to keep the exact working distance. Hence, they need a stationary work or reading station. Elderly visually impaired patients often complain about not being able to capture or maintain an image. Even little sways of the head will bring the image out of focus or make the patient lose the line he was reading. Therefore, Kepler spectacle telescopes are usually only accepted by elderly visually disabled patients who are used to reading and who kept their reading habit since the onset of their loss of vision. The Galilean system is preferred by most elderly visually impaired patients, especially those suffering from the late stages of AMD, even though it cannot offer sufficient working distance and the focus is reduced toward the edges of the image (Fig. 20.5). This may be explained by the larger field of view preferred by elderly patients.

The individual refraction for the distance must be taken into account in these systems. The desired distance of use is adjusted to infinity, 3, 2 or 1 m. However, there is also the option of converting it from infinity to the required distance by the patients themselves with an add-on cap. By choosing the magnification, the working distance is fixed. But there is still a choice of several different magnifications for the near distance, either by varying single add-ons or by using double add-ons.

If present - binocular far vision should be supported e.g., for watching TV. Whether a patient still posseses binocular vision has to be carefully examined especially in AMD-patients where the extent of a central scotoma may have distroyed binocular vision.

For near vision, monocular low-vision support is adequate; the non-reading eye is covered. Exceptions

are Galilean systems constructed for the near range and hence offering a fivefold binocular magnification. Likewise, some Kepler systems offer a magnification of eight times when adapted for low-distance use.

Especially for elderly low-vision patients suffering from AMD several appointments are required for all necessary examinations and sufficient training. The low-vision patient must learn to use the system for tasks both at a distance and close by, such as reading, writing, playing music (reading music) or participating in recreational activities. It is advisable to lend the patient a low vision aid test system for a period of 2–3 weeks.

20.7Electronic Magnifiers for Low Distance Tasks

•Closed Circuit Television Systems (CCTV). If visual acuity is reduced to 0.1 (20/200), a closed circuit television system (CCTV) may well be suitable for the visually disabled wishing to read (Table 20.2). Should the patient need a magnification of eight times or more and would like to read for longer periods of time (e.g., books) then a CCTV presents the ideal visual aid.

The basic principle of a CCTV is simple: a video camera transmits the image by cable, in this case the text for reading onto a monitor. Beneath the monitor and the camera, the reading text is moved on an x-y- platform according to the individual reading speed. The letters appear on the monitor at the necessary magnification (Fig. 20.7).

Magnification can be set to from 4 up to 30 times or even higher, with simultaneous contrast enhancement. This feature makes CCTV superior to other LVAs where contrast is generally lowered because of aberration and dispersion.

In addition to freely variable magnification, every CCTV magnifier offers the option of contrast inversion. Text can be read in white on a black background instead of black on white. This inverted presentation is preferred by over 90% of low vision patients [9]. Most CCTV magnifiers have the option to display false color presentations for text and background.

Further on offer are reading sets consisting of a camera and a reading table that may be connected to a monitor or a TV set. Handling of this set-up is often difficult for older people because the monitor is standing next to the reading table.

Fig. 20.7 CCTV, inverse display with white letters on black background

The visually impaired patient with AMD usually requires a larger monitor diameter than young patients to present a larger view of the reading material.

Another advantage of an electronic CCTV is that the viewing angle can be widened by use of larger monitors or by reducing the distance to the screen. Therefore, very peripheral retinal areas can still be used for reading. A highly visually impaired patient suffering from AMD, who may legally be regarded as blind, may be able to regain reading ability with his residual vision if only a peripheral retinal area of sufficient extent remains intact. CCTV reading systems can also be applied for writing, filling in forms, completing crossword puzzles or looking at photographs.

During the last years different small hand-held readers with flat screen monitors have been invented. They offer the same advantages as magnifying glasses and can be used like these. One should take care to acquire a reasonably sized monitor for the necessary enlargement and pay attention to the ease of handling (Fig. 20.8).

The development of electronic books (e.g., Kindle, Amazon) and above all tablet PCs such as the iPad

Fig. 20.8 Mobile electronic reading system with TFT monitor

(Apple) allows reading a large number of books and magazines using an adjustable enlargement. Thus, receiving information about daily events is also possible. The iPad offers contrast inversion and therefore can be used by the visually impaired, even if operating it with the fingers is not easy. The improvement of an additional camera also permits reading of any chosen text.

Advantages: Especially elderly low vision patients suffering from AMD with a large central visual field defect may be able to read with their remaining peripheral retinal areas when using a CCTV. Frequent reading will train patients’ eyes to use their peripheral retinal areas in a more efficient way. With the use of CCTVs a comfortable position in front of the screen may be taken which is especially important for the elderly. The viewing distance does not need to be maintained exactly. Central positioning problems which often occur with optical magnifiers are not experienced.

Disadvantages: CCTV magnifiers are fixed setups requiring a secure space for use. Especially elderly low vision patients complain that every document has to be taken to the CCTV magnifier to be read there. Although several portable setups are available coordination of the hand-held camera may pose a problem to the older low vision patient, and the small screen may offer only a restricted overview (Fig. 20.8).

Elderly low vision patients unaccustomed to reading a lot are rarely satisfied with a CCTV magnifier system. Not only is there a lack of motivation in these patients, reservations concerning the handling of the equipment have to be overcome as well. This may be observed during training sessions when patients have difficulties to stick to one line, sometimes they read