LOW VISION REHABILITATION (LVR) IS A NEW subspecialty emerged from the traditional fields of ophthalmology, optometry, occupational therapy, and sociology, with an ever-increasing impact on our usual concepts of services for visually impaired patients, research, and education.¹

Ophthalmology medical and surgical treatments aim first and foremost to preserve and/or restore organ structures threatened or damaged by disease. The final goal of eye care, however, is to preserve and/or restore quality of life (QOL) and function previously enjoyed by the individual, preferably ad optimum.² Evidence-based data show that patients gain better visual functions such as visual acuity, fields of vision, contrast sensitivity, and oculomotor functions as a result of medical and surgical treatments, and better visual skills such as reading and mobility as a result of LVR training, together rendering better QOL.

LVR retraining is part of a multidisciplinary effort and essential for the optimal restoration of skills and QOL. It is generally agreed that LVR includes low vision assessments together with prescribing and provision of low vision devices as well as low vision rehabilitation therapy and training. It includes the treatment and education process that enables individuals who are blind or visually impaired to attain maximum function, a sense of well-being, a personally satisfying level of independence, and optimum QOL, which are critical to their safety and mobility. Function is maximized by evaluation, diagnosis, and treatment including, but not limited to, the prescription and dispensing of optical, non-optical, electronic, training, and environmental modifications and/or other treatments.

Permanent loss of vision is devastating and its impact on QOL and well-being of the individual is beyond levels of visual acuity measured in the office. Functional vision is the yardstick by which patients assess our interventions and not levels of visual acuity. Cataract surgery that restores vision to 20/200 may not be viewed as a success by the surgeon; however, it would be viewed as a 100% success by the patient who can again read newspaper print with visual aids.³

Background

Low vision (LV), blindness, and low vision rehabilitation (LVR) were recognized as health entities centuries ago. During his travels to China in the thirteenth century, Marco Polo discovered, quite surprisingly, that elderly people use magnifying glasses for reading, a practice that was swiftly adopted in Europe (Fig. 89–1). The advances in medical sciences witnessed during the eighteenth and nineteenth century brought new attention to eye diseases, blindness, and LVR. One could talk about LVR per se only starting with the beginning of the twentieth century. Roughly, we will talk about two historical periods before we detail the state of the art today.

Before World War II, from a demographic perspective, most of the visually impaired individuals were children. Infections affecting the eye either after birth (gonorrhea) or in early childhood (smallpox) were responsible for ocular damage and vision impairment in many cases. Life expectancy was under 65 years of age and few adults lived long enough to develop age-related visual impairments. This is the time when blindness was recognized as a diagnosis and a major health care issue. Low vision was not considered useful by vision specialists of the day and at the same time when detected, strong advice was issued to save the residual vision by simply not using the eyes.

This is also the time when the first institutional facilities for the visually impaired were set up, mostly for children. It started from concern for their safety, education, and well-being. The aim of educational programs for the visually impaired was to teach an employable skill and thus to provide some measure of economic rehabilitation to the visually impaired individual.

The four decades following World War II were quite different. The demographic picture changed drastically. Life expectancy grew to an average of 74 years. This allowed more people to grow older and develop age-related chronic ailments.

The first specialty low vision clinics were opened in the United States and the first dedicated practitioners of LVR, such as Gerald Fonda and Eleanor Faye, left their trailblazing and lasting marks on the entire LVR field. This is also the time when it was becoming evident that involvement with LVR is multidisciplinary including not only the professions of ophthalmology and optometry but also occupation therapy, opticianry, social work, and the many teaching disciplines addressing various rehabilitation needs.

The first manuals and textbooks were produced by ophthalmology and optometry (Faye, 1957).³³ Vision therapy training methods were detailed in manuals published by Quillman (1980).³⁴ The first training courses for professionals were established in 1975 at the Lighthouse in New York City. Finally, this is the time when many of the optical devices we still use today in clinical practice are designed and mass produced (Fig. 89–2).

One can really talk about modern LVR only after 1986, when the American Foundation for the Blind sponsored the first international conference in LVR, which took place in Asilomar, California.

Today, it is recognized by all that modern LVR indeed is a multidisciplinary professional service that provides methods and means for optimal use of residual visual functions, training of residual vision-related skills, and reintegration in society. Comprehensive vision rehabilitation (CVR) is recognized as entailing aassessment of current residual visual functions, assessment of patient’s ability to perform vision-dependent tasks, formulation of a vision rehabilitation plan, prescribing and dispensing of assistive devices and providing orientation and training in their use, referral as needed for additional post-vision loss rehabilitation therapy, and providing information on other resources required to address patient needs post-vision loss.^1,4

Yet, LVR is still a “work in progress.” This chapter will detail the achievements, the challenges, and the hope that characterize this new branch of clinical rehabilitation.

Recent data shows that in 2010, worldwide, there were about 383 million visually impaired people. Their number will reach about 500 million by the year 2020.⁵ In the United States, (population 313 million) it is calculated that 8 million people are visually impaired. For Canada (population 35 million), the numbers are proportionally similar at 1 million.

Many studies published worldwide in the last two decades showed and confirmed the prevalence and causes of visual impairments leading to blindness and low vision.^6–9 In terms of numbers, most low vision and blindness cases (about 90%) reside in developing nations. Yet, in term of conditions responsible for low vision and blindness, the worldwide picture is quite similar in developed as it is in developing countries. The most outstanding prevalent causes for low vision and blindness in the world today are refractive errors, cataracts, diabetic retinopathy, age-related macular degeneration, and glaucoma.¹⁰

Visual impairment as a result of uncorrected refractive errors is as common in developed nations as in developing countries.¹¹ Any observer would agree that there is no surprise in the fact that this is a worldwide health care issue. Elimination of refractive errors as a cause for vision impairment is dependent on availability of trained professionals who can prescribe correction for refractive errors, affordable eyewear, and universal access to such services. Hence, refractive errors elimination as a cause for vision impairment is well-managed in developed countries, whereas in developing countries, this is still a major issue of public health care management.

Cataracts are by far a worldwide leading cause for visual impairment. Elimination of cataracts as a cause for visual impairment is mostly managed today with surgical technological advances aimed at removing the cataractous lenses and their substitution with artificial implants. Access to technological advances and to financial means in developed countries rendered cataracts to be a condition managed easily and efficiently. Not so in developing countries where many barriers still exist to provide proper care to those who have cataracts.

Diabetes mellitus became a leading cause for visual impairment in the last 50 years as longevity became more prevalent in general and insulin treatments more widespread worldwide. Significant reduction of vision loss from diabetes mellitus is achieved today with efficient medical treatments and with efficient screening and monitoring of retinal health with periodic eye examination. The prevalence of diabetic retinopathy in developed and in some developing countries is somewhere between 5% and 10%.¹² In spite of availability of effective treatments, 2% and 5% of those affected will still lose vision.

Many studies described the exponential prevalence of low vision and blindness associated with age increase.⁹ The main etiology for loss of vision in the aged population is age-related macular degeneration. Age-related macular degeneration is still unmanageable in most cases, yet in those with the “wet” variant, the new anti-vascular endothelial growth factor (anti-VEGF) agents have made a dramatic impact. Anti-VEGF agents not only stop vision loss but also restore lines of vision after successful treatments.¹³

Glaucoma is a significant and prevalent cause of vision loss worldwide. It is estimated that 10% of the population may develop glaucoma during their lifetime with much higher prevalence in those with a glaucoma family history.¹⁴ In spite of us living in the twenty-first century, the only treatment that was shown to delay the advancement of glaucoma is reduction of intraocular pressure. There is no sign in sight of treatments to cure glaucoma. Hence, the only other major approach in management of glaucoma is early detection. Due to the fact that glaucoma as an entity is still poorly defined, early diagnosis is still intricate. Microperimetry, a new technology for structural and psychophysical analysis of visual functions, may provide in the future a better tool for early glaucoma diagnosis.¹⁵

LV is defined as a level of visual impairment that cannot be corrected by conventional glasses or by medical or surgical interventions and that causes a disability/activity limitation. For all practical purposes, LV is perceived as reduced visual functions not acceptable to an individual or to the significant other in the life of the individual.¹

Although a variety of worldwide definitions exist, recently, in Ontario, Canada, the Ontario Health Insurance Plan adopted new progressive definitions for visual impairments to be used for administration of public health services for the visually impaired. Today, in Ontario, LV is defined either as best corrected visual acuity of 20/50 or less in the better eye, or significant oculomotor dysfunction such as nerve palsy or nystagmus resulting in low visual acuity, or visual field defects such as splitting of fixation, scotomata, or quadranopic or hemianopic field defects, all not amenable to further medical and/or surgical treatment. In terms of visual acuity (VA), this is similar to the North American definition, that is, best corrected VA of <20/40.¹⁶

Low Vision Rehabilitation Assessment

LVR as a distinct and separate subspecialty of ophthalmology is still evolving, as are practice templates, which are still unfamiliar to the few practitioners in this field or to the ones joining into practice. Assessment methods and testing instruments are relatively new and unknown, as are the interventions contemplated and the devices prescribed. Furthermore, the practice environment is diverse from locale to locale and a practice template for one jurisdiction or one profession may not suit another. Practice templates were offered in the past by ophthalmology, optometry, occupational therapy, and others, mostly in Europe and in the United States.

The following paragraphs describe details on modern assessment methods and diagnostic instruments to be used in LVR.

True to the nature of Rehabilitation Medicine, usage of an initial “Intake” questionnaire and testing protocol allows gathering of data on a patient’s background as well as on cognitive abilities, detection of depression, and on vision-related functional abilities. Among other assessment elements, it is important at this stage to also assess overlooked structural defects that may benefit from surgery, attention deficits, visual neglect, and Charles Bonnet symptomatology.

The next stage in the assessment process is to gather data on residual visual functions such as visual acuity, contrast sensitivity, residual fields, and scotomata, as well as on residual oculomotor functions and eccentric viewing. The assessment of residual visual functions offers a unique opportunity to measure, evaluate, and document accurately the extent of functional loss the patient sustained from disease. Assessment methods used in routine ophthalmologic clinical practice are usually inadequate for LVR and special LVR tests must be used. Specific methods and outcome measures used in LVR assessments also include such measures as face recognition, potential visual acuity, residual native vision, macular microperimetry, and chromatic contrast sensitivity.^1,15

Assessment of residual functional vision is the core of the LVR assessment process providing the basis for specific interventions aimed at restoration of functional skills and QOL. It includes testing for outcome measures on preferred retinal locus (PRL) fixation patterns, residual binocularity and stereopsis, ocular dominance, oculomotor characteristics such as fixation stability, and also glare control. In addition, it always includes assessment of reading skills. Specialized assessments for writing, orientation and mobility, and driving are also used in certain circumstances.^1,17

Interventions to Improve Visual Functions

The purpose of an LVR assessment is ultimately to provide recommendations for interventions that will lead eventually to restoration of QOL. The outcome from assessing residual visual functions is detection of visual functions that can be improved with the use of LV devices; whereas, the outcome from assessing residual functional vision is detection of functional vision that can be improved with the use of vision rehabilitation therapy (VRT) training.

A sequential approach, as detailed below, is recommended for prescribing devices aimed at improving residual visual functions. Such prescribing should start with correction of refractive errors (taking notice of eye dominance) followed by stabilization of oculomotor functions with image relocation, then prescription of best lighting conditions to reduce glare and improve contrast, and ending with prescription of adequate magnification and field restitution devices.¹

Interventions are prioritized to reflect outcomes aimed at improving performance of tasks at near, intermediate, and far distances as desired by the patient. Traditional modalities used for LVR include plus lenses in glasses and handheld magnifiers in order to create various levels of magnification as needed by the patients. Today, common types of equipment used include telescopic devices, monoculars and binoculars, handheld, and head-borne. Prisms are utilized for image relocation and stabilization of images on the retina and selective transmission lenses for modulating light perception.¹⁸ Additionally, modern tools for LVR are also employed.

Ideally, any protocol for LVR interventions should include elements of modern LVR. The modern goals for LVR include assessment and recovery of potential visual acuity available at the PRL, restoration of binocularity, PRL rehabilitation, and perceptual training.¹⁹ Modern devices used today for LVR also include a variety of closed-circuit TVs (CCTV), computer systems with specialized software, and GPS technology for orientation and mobility.