Clinical Effectiveness of Low Vision Rehabilitation in Glaucoma Patients

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. References 1. US Department of Health and Human Services. Vision research a national plan: 1999-2003; NIH Publication No. 98-4120. National Eye Institute, Bethesda MD, 1998: 117-30 2. Evans K, Law S, Walt J, Buchholz P, Hansen J. The quality of life impact of peripheral versus central vision loss with a focus on glaucoma versus age-related macular degeneration. Clinical Ophthalmology 2009:3 433-445 3. Department of Veterans Affairs. Veterans Health Administration, Blind Rehabilitation Service. Coordinated Services for Blinded Veterans IB 11-59 (revised) P87250. Department of Veterans Affairs, Washington DC, 1996. 4. Stelmack JA, Tang XC, Reda DJ, Moran D, Rinne S, Mancil RM, Cummings R, Mancil G, Stroupe K, Ellis N, Massof RW. The Veterans Affairs Low Vision Intervention Trial (LOVIT): design and methodology. Clin Trials. 2007;4(6):650-60. 5. Stelmack JA, Tang XC, Reda DJ, Rinne S, Mancil RM, Massof RW. Outcomes of the Veteran Affairs Low Vision Intervention Trial (LOVIT) 6. Stelmack JA, Moran D, Dean D, Massof RW. Short and long-term effects of an intensive inpatient vision rehabilitation program. Arch Phys Med Rehabil 2007; 88:691-5. 7. Robinson, S. (2010). Chapter 31: Advanced Glaucoma and Low Vision: Evaluation and Treatment. In Schacknow, P.N. and Samples, J.R. (Eds.), The Glaucoma Book: A Practical, Evidence-Based Approach to Patient Care. (pp. 351-353). New York: Springer. 8. Stelmack J, Szlyk J, Stelmack T, et al. Use of Rasch person item map in exploratory data analysis: a clinical perspective. J Rehabil Res Dev 2004; 41: 233-42. 9. Szlyk JP, Stelmack J, Massof RW, et al. Performance of the Veterans Affairs Low Vision Visual Functioning Questionnaire. J Vis Impair Blind 2004; 98: 261-75. 10. Stelmack JA, Szlyk JP, Stelmack TR, et al. Psychometric properties of the Veterans Affairs Low-Vision Visual Functioning Questionnaire. Invest Ophthalmol Vis Sci 2004; 45: 3919-28. 11. Stelmack JA, Szlyk JP, Stelmack TR, et al. Measuring outcomes of low vision rehabilitation with the Veterans Affairs Low Vision Visual Functioning Questionnaire (VALV VFQ-48). Invest Ophthalmol Vis Sci 2006; 47: 3253-61. 12. Quigley HA, Broman AT. The number of people with glaucoma worldwide in 2010 and 2020. Br J Ophthalmol. 2006 Mar;90(3):262-7.