Clinical Effectiveness of Low Vision Rehabilitation in Glaucoma Patients With Moderate or Severe Vision Loss
Clinical Effectiveness of Low Vision Rehabilitation in Glaucoma Patients With Moderate or Severe Vision Loss
Our team is interested in what can be done to improve the functioning of patients who suffer from glaucoma, a chronic and irreversible eye disease. Patients with vision loss as a result of this disease may feel like they have been 'given up on', or lost to our medical system when no further interventions can be offered to treat their eye disease. It is our intent to investigate what alternatives we can provide our patients, instead of simply saying, 'nothing more can be done'. We have learned from studies done on other chronic eye diseases, like age related macular degeneration, that low vision rehabilitation can improve visual function.
What exactly is low vision? It can involve a loss of visual acuity, making activities such as reading or writing a challenge; it can involve loss of contrast sensitivity, making shapes and edges hard to discern, like those of a stair edge, or person's face. It could also involve a loss of peripheral, or side vision which is a symptom common to most glaucoma patients. Whatever the cause of low vision, doing day-to-day activities can become increasingly difficult, and many suffer from a loss of their independence and may even become depressed. Low vision rehabilitation involves helping patients to use their remaining vision in optimal, and sometimes even new, ways. This involves an assessment of a person's baseline vision, and an idea of what their needs are. Patients are then given low vision aids (such as magnifiers, telescopes, video screens which magnify images, and other tools) as well as instructions and support for adapting to living and functioning with altered vision.
Although there currently exists no cure for glaucoma, and we are certainly not promising a reversal of the damage done to the eyes from this chronic disease, we do believe that these types of rehabilitation services may offer some hope and potential visual benefit to patients living with vision loss. Our hypothesis is that the use of state-of-the-art low vision aids in patients with advanced glaucomatous visual loss will provide an improvement in visual tasks and thereby an improvement in quality of life.
Visual impairment, including both low vision and blindness, ranks among the ten most prevalent causes of disability in North America (1). Leading causes of low vision are diseases also associated with an aging population, including age related macular degeneration (ARMD), glaucoma, diabetic retinopathy and optic neuropathies (1). Of these, irreversible vision loss is most commonly caused by ARMD and glaucoma, diseases for which there exists no cure (2). Quality of life and functional ability are negatively impacted by vision loss and blindness (2). Loss of visual ability impairs both mental and physical functioning, limiting activities of daily living (ADL) (eating, dressing, reading, writing, mobilizing, interpersonal communication etc.) (3). Impedance on basic functioning secondary to visual impairment can lead to loss of independence, low self-esteem or depression (3). When pharmacological or surgical interventions prove futile in advanced vision loss, low vision rehabilitation may be the only option for regaining lost function in patients. The goal of low vision rehabilitation is to not restore lost vision but rather utilize the remaining vision to its fullest potential thus enabling patients to reclaim their ADL and thereby their independence.
Our study is based on the Veterans Affairs Low Vision Intervention Trial (LOVIT), a randomized controlled trial conducted by Stelmack et al (4-6). Their goal was to evaluate the efficacy of an outpatient low vision rehabilitation program for patients with moderate to severe vision loss secondary to age related macular degeneration (ARMD). Their intervention was effective in improving all aspects of visual function when compared with the control group. There is very little evidence to support the use of low vision rehabilitation in patients with chronic, irreversible visual loss secondary to glaucoma, and currently no randomized trials have been done. Because the pattern of visual loss is different in ARMD and glaucoma, it is not possible to extrapolate the ARMD data beyond the ARMD cohort. Yet, the ARMD experience has established a proof of principal that can be used in the glaucoma protocol design In patients with advanced glaucomatous optic neuropathy, functional loss often begins with mobility and difficulty ambulating (7). In one study, patients with visual field loss secondary to their glaucoma showed a diminished traffic gap judgement when crossing the street, which lead to an increased risk of harm. As a whole, the group made 23% more errors in identifying a gap as crossable when it was too short to be made safely (7). Another researcher found that 25% of patients with visual field loss in both eyes reported a moderate to severe restriction in their mobility activities overall. In another study, field loss secondary to glaucoma lead to a lower vision-related quality of life score. When examined collectively, these reports and others suggest that those with reduced visual fields and glaucoma experience more falls, more motor vehicle accidents, greater overall difficulty with mobility activities and an overall decreased quality of living (7). Visual acuity can vary over a wide range among patients with moderate to severe glaucoma, but overall, central vision reduction occurs late in the disease. Some studies do show mild central and diffuse reduction in fields in the early stages of glaucoma. As the visual fields and visual acuity decline, patients often note difficulty with glare sensitivity, leaving response times to light and dark adaptations hindered. In summary, the problems most often experienced by patients with advanced glaucoma are related to ambulation, reading, distance spotting and glare. Low vision rehabilitation aims to maximize independence in patients' daily lives by addressing these difficulties.
It would be difficult to argue that low vision aids and rehabilitation in patients with visual loss do not have a positive impact on both patients and their families; however there exists little in the way of randomized controlled clinical trials which evaluate efficacy of outpatient low vision rehabilitation and interdisciplinary strategies to deliver such services. Given the existing shortage of inpatient resources and the staff required to manage such patients, an outpatient program could deemed more cost effective and practical in our limited health care system. Moreover, most available data on the subject focuses on rehabilitation in patients with ARMD. There is very little to support the use of low vision rehabilitation in patients with chronic, irreversible visual loss secondary to glaucoma. As our population ages, we can expect with certainty an increase in the prevalence of visual loss secondary to glaucoma, beginning in the next ten years (12). An evaluation of the efficacy of strategies to address 'untreatable' vision loss, such as those patients with 'end of the line' glaucoma, would be of great significance as we see glaucoma and its devastating effects on vision and subsequently on quality of life increase greatly in the near future. Evidence based models of outpatient low vision rehabilitation programs are needed to support the implementation and delivery of such services for patients suffering from moderate to severe glaucoma, and its devastating impact on daily functioning.
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