What Is Visual Ability? A New Study Looks at Low Vision Rehabilitation

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Researchers associated with the Low Vision Research Network Study Group have identified a number of non-visual factors that can affect “visual ability” [i.e., a person’s ability to perform everyday tasks that are dependent on vision] in a group of older adults participating in outpatient low vision rehabilitation.

The study concludes that visual ability is an individualized “multidimensional construct” that includes a number of interrelated visual and non-visual factors, such as visual acuity, mobility, physical ability, depression measures, and cognition (thinking, understanding, learning, and remembering).

In addition, the researchers note that the limitations these non-visual factors may impose on the process of low vision rehabilitation are important considerations when measuring rehabilitation outcomes.

From JAMA Ophthalmology

The research, entitled Visual Ability of Patients Seeking Outpatient Low Vision Services in the United States, was published “online first” in the June 19, 2014 edition of JAMA Ophthalmology (formerly Archives of Ophthalmology). JAMA Ophthalmology is an international peer-reviewed journal published monthly by the American Medical Association.

The authors are Judith E. Goldstein, OD; Melissa W. Chun, OD; Donald C. Fletcher, MD; James T. Deremeik, MA, CLVT; and Robert W. Massof, PhD, who represent the following organizations and institutions: the Low Vision Research Network Study Group; Johns Hopkins University School of Medicine; David Geffen School of Medicine at UCLA; California Pacific Medical Center; and the University of Kansas.

What Is Low Vision?

  • Low vision is uncorrectable vision loss that interferes with daily activities. It is better defined in terms of function, rather than [numerical] test results. (Massof and Lidoff)
  • In other words, low vision is “not enough vision to do whatever it is you need to do,” which can vary from person to person.
  • Most eye care professionals use the term “low vision” to describe permanently reduced vision that cannot be corrected with regular glasses, contact lenses, medicine, or surgery.

You can learn more about low vision at Low Vision and Legal Blindness Terms and Descriptions and What is a Low Vision Examination? on the VisionAware website.

About the Research

From Non-visual Factors Affect Visual Ability in Elderly Patients via Medscape (registration required):

“Visual ability” is affected by a number of non-visual factors in elderly patients seeking outpatient low vision rehabilitation. Walking ability, using a computer, depression, and cognitive function play an important role in setting up a low vision rehabilitation plan for individual patients, write Judith E. Goldstein, OD and colleagues. The researchers analyzed the records of patients from 28 clinics throughout the United States.

The researchers recruited 779 patients between April 25, 2008, and May 2, 2011, as part of the Low Vision Rehabilitation Outcomes Study (LVROS). The study population was 67% women and had a mean age of 76.4 years.

The researchers assessed low vision rehabilitation outcomes through an Activity Inventory (AI) tool, a questionnaire administered at baseline by computer-assisted patient interview. During the interview, patients rated activities in terms of (a) importance of personal goals and (b) personal difficulty in achieving the goals.

After low vision rehabilitation, researchers assessed patients’ (a) visual ability [i.e., a person’s ability to perform tasks dependent on vision] and (b) functional ability [i.e., a person’s ability to perform tasks with ease].

Among the 779 patients, visual acuity was the strongest predictor of visual ability and reading ability and had a significant independent effect on the other functional [activities].

The researchers also found that (a) physical ability was independently associated with overall visual ability, mobility, and visual motor function and (b) depression consistently and independently affected overall visual ability and all functional areas.

“Our findings indicate that the number of comorbidities [i.e., simultaneous medical conditions] is not a good predictor of visual ability,” they write. “Rather, measures of the patients’ ability to perform activities, such as walking and climbing steps, is a significant predictor of visual ability …”

What Is Vision Rehabilitation?

The term “vision rehabilitation” includes a wide range of professional services that can restore functioning after vision loss, just as physical therapy restores function after a stroke or other injury. Vision rehabilitation services allow people who are blind or have low vision to continue to live independently and maintain quality of life.

Vision rehabilitation services for adults who are blind or have low vision are provided by a team of specially trained professionals, including low vision therapists, vision rehabilitation therapists, and orientation and mobility specialists.

Low Vision Therapists

Certified Low Vision Therapists (CLVTs) instruct individuals in the use of remaining vision with optical devices, non-optical devices, and assistive technology.

Vision Rehabilitation Therapists

Certified Vision Rehabilitation Therapists (CVRTs) teach adaptive independent living skills, enabling adults who are blind or have low vision to confidently carry out a range of daily activities.

Orientation and Mobility Specialists

Certified Orientation and Mobility Specialists (COMS or O&Ms) teach safe and independent indoor and outdoor travel skills, including the use of a long cane, electronic travel devices, public transportation, and sighted guide, human guide, and pre-cane skills.

More about the Study from JAMA Ophthalmology

From the article abstract:

Objective: To identify factors that contribute to visual ability measures in patients who present for outpatient low vision rehabilitation (LVR) services.

Design, Setting, and Participants: As part of a prospective, observational study of new patients seeking outpatient LVR, 779 patients from 28 clinical centers in the United States were enrolled in the Low Vision Rehabilitation Outcomes Study (LVROS) from April 25, 2008, through May 2, 2011.

[Note: A prospective study measures a group of individuals over time and follows up with the study subjects in the future.]

The Activity Inventory (AI), an adaptive visual function questionnaire, was administered to measure overall visual ability and visual ability in four functional domains (reading, mobility, visual motor function, and visual information processing) at baseline before LVR.

The Geriatric Depression Scale, Telephone Interview for Cognitive Status, and Medical Outcomes Study 36-Item Short-Form Health Survey physical functioning questionnaires were also administered to measure patients’ psychological, cognitive, and physical health states.

Conclusions and Relevance: Visual ability is a multidimensional construct, with visual acuity, depression, physical ability, and cognition explaining more than one-third of the variance in visual ability as measured by the AI. The significant contributions of the non-visual factors to visual ability measures and the [limitations non-visual factors may impose on LVR] are important considerations when measuring … LVR outcomes in ongoing clinical research.

VisionAware will continue to report on significant low vision research projects as they become available.