**4. Low vision aids for AMD patients**

#### **4.1 Non-optical aids**

Environmental adaptations such as adequate illumination (by the use of light flexes or lecterns) and glare reduction and light with specific wavelengths preferred by the patients (by the use of prescription filters) are two well-known beneficial strategies for improving functional outcome measures in CFL patients.

These interventions result in apparent improved contrast sensitivity and better visual acuity for AMD patients [54, 55], so ensuring these optimal conditions is a fundamental step prior to the prescription of any additional aid.

Increasing the amount of light has demonstrated to have a significant positive effect on sentence reading acuity, reading speed and critical letter size for AMD patients [50].

In addition, some authors who have investigated the effects of making light adjustments in the homes of people with visual impairment have found that higher lighting levels led to greater well-being and a significant improvement in certain instrumental ADLs [56].

The use of filters has also been shown to improve vision-related QoL in patients with AMD, with the success rate of filter placement being better for those patients with visual acuity less than 0.25 and those with advanced AMD [57]. Nevertheless, although various tests exist to determine the best color, tint, lens material or frame type for a given patient, to date no specific protocol has been developed to assist in prescribing tinted or selective transmission lenses [58].

#### **4.2 Optical aids**

Optical aids for near vision involve the use of lenses to reduce the viewing distance of an object, making it easier to see, and are primarily used to tasks requiring near resolution acuity, such as reading, writing, personal care (i.e., make-up, nail polishing) and different leisure activities, such as sewing or drawing.

These optical LVAs broadly include the use of high-plus reading lenses and different magnifiers (including clip-on, hand-held, or stand devices), which power will ultimately depend on the patient's remaining vision and on the size of the object or printed material to be seen by the patient [59, 60]. In a consecutive sample of 100 individuals with AMD, these optical LVAs was shown to improve near BCVA from 0.13 (decimal) to 0.39 [61].

When reading with a hand-held magnifier, the magnifier has to move along the line and at the same time keep a constant distance from the text to ensure a clear image [62].

Clip-on magnifiers overcome this disadvantage, but can nevertheless scratch the lenses and reduce the visual field to further distances. In this context, stand magnifiers are the choice preferred by patients, as they offer ergonomic advantages such as a comfortable viewing angle, the possibility of both reading and writing, better illumination, a wider field of view, variable power and magnification, and a greater working distance [63].

Magnification can also be achieved with the use of telescopic devices, which are used to recognize objects that are outside the near vision range. These optical aids can be used for tasks such as reading street signs, road signs, and transport timetables, making them a great ally for outdoor mobility. Furthermore, additional magnifying devices can easily be applied to these devices to improve near vision as well.

In recent years, advances in surgery have allowed intraocular implantation of these devices. Implantable miniature telescopes (IMTs) are visual prosthetic devices usually implanted monocularly depending on the eye with BCVA and, once implanted, are used to magnify objects in the patient's central visual field and focus them onto healthy areas of the retina, allowing them to recognize objects they would otherwise not be able to see [64]. In this way, the implanted eye is responsible for detailed vision, and the fellow eye will be responsible for peripheral vision tasks, including ambulation.

The safety and efficacy of these devices has been evaluated in different clinical trials that have found similar improvements in BCVA after one year of implantation (≈60% of participants gained three or more lines in either distance or near BCVA), with no serious adverse events reported [65, 66]. In addition, a follow-up study showed that substantial visual improvements achieved with the intervention were maintained at two years [67].

#### **4.3 Electronic aids**

Electronic vision enhancement systems include closed-circuit television (CCTV) systems and other systems incorporating a monitor or a liquid-crystal display (LCD) screen in which the image or the print is projected after being digitized.

These systems provide increased magnification and an enlarged field of view than traditional optical aids, with the possibility of controlling relevant parameters, such as brightness, glare or contrast, so they can be appropriate for individuals which vision is greatly reduced or in which the use of optical aids have failed in achieving their goals.

For example, in a retrospective study of 530 patients with different stages of AMD in which participants were provided with different LVAs, successful VR (reading ability in 94% of patients when only 16% could read before) was achieved with optical visual aids in 58% of patients, whereas 42% needed electronic CCTV systems [68].

A clinical trial in which 37 subjects with central field loss were randomized to receive standard VR (group A = 18 subjects) or standard VR plus electronic magnifiers (group = 19 subjects) showed that, at 1 month, group B read faster and was better at two spot reading tasks such as reading continuous print and finding a number in a phone book, but did not differ from the group A in terms of functional capacity or well-being [69].

*Evidence-Based Practice and Trends in Visual Rehabilitation for Patients with Age-Related… DOI: http://dx.doi.org/10.5772/intechopen.96817*

In another crossover study comparing the near vision activity performance of 84 experienced users of optical aids when using portable electronic vision enhancement systems plus optical magnifiers or optical magnifiers alone, it was observed that, at 2 months, the use of electronic systems allowed longer duration of reading. In addition, participants reported less difficulty performing a range of near vision activities when using these systems and were able to perform more tasks independently [70].

In addition to CCTV systems, these LVAs include the use of head-mounted displays (HMDs) [71], which enhance vision by coupling digital image processing directly to the patient's retina, and the use of portable electronic devices (such as tablets, smart-phones and electronic readers), which combine the portability of hand-held magnifiers with the high-resolution displays of electronic magnifiers (CCTV) and incorporate basic features for handling optical characteristics that can be useful to improve functional measures in patients with AMD, such as image enlargement or contrast polarity [72, 73].
