Is it time to confine Snellen charts to the annals of history?

Purpose: A paper published by the author in 1988 in this journal provided some important findings about the lack of precision of visual acuity (VA) measures made with commonly used Snellen charts and the advantages of using letter charts designed using the principles proposed by Bailey and Lovie in 1976. That 1988 paper has been cited a number of times since, mostly supporting the findings. The purpose of this review is to examine the changes that have occurred in VA measurement in research and clinical practice since that earlier study.

Visual acuity testing. From the laboratory to the clinic.

The need for precision in visual acuity assessment for low vision research led to the design of the Bailey-Lovie letter chart. This paper describes the decisions behind the design principles used and how the logarithmic progression of sizes led to the development of the logMAR designation of visual acuity and the improved sensitivity gained from letter-by-letter scoring. While the principles have since been adopted by most major clinical research studies and for use in most low vision clinics, use of charts of this design and application of letter-by-letter scoring are also important for the accurate assessment of visual acuity in any clinical setting.

Inferior field loss increases rate of falls in older adults with glaucoma.

Purpose: To examine the visual predictors of falls and injurious falls among older adults with glaucoma.

Methods: Prospective falls data were collected for 71 community-dwelling adults with primary open-angle glaucoma (mean age, 73.9 ± 5.

Inferior visual field reductions are associated with poorer functional status among older adults with glaucoma.

Purpose: To examine the relationship between visual impairment and functional status in a community-dwelling sample of older adults with glaucoma.

Methods: This study included 74 community-dwelling older adults with open-angle glaucoma (aged 74 ± 6 years). Assessment of central vision included high-contrast visual acuity and Pelli-Robson contrast sensitivity.

Visual field size criteria for mobility rehabilitation referral.

Purpose: To investigate evidence-based visual field size criteria for referral of low-vision (LV) patients for mobility rehabilitation.

Methods: One hundred and nine participants with LV and 41 age-matched participants with normal sight (NS) were recruited. The LV group was heterogeneous with diverse causes of visual impairment.

Does a line guide improve reading performance with stand magnifiers?

Purpose: When reading with a stand magnifier (SM), navigation along each line of text and retracing back to the correct position at the beginning of the next line has been suggested as a major difficulty for people with low vision. In this study, we evaluated the immediate impact of using a simple and inexpensive line guide on navigation performance.

Methods: Twenty-nine participants with age-related macular degeneration read short passages of text using their habitual SM with and without a temporary line guide attached.

Visual function, visual attention, and mobility performance in low vision.

Purpose: The aim of this study was to determine if useful field of view (UFV) measures help to predict aspects of orientation and mobility in people with visual impairment. The UFV is a composite measure of visual attention, ability to detect objects in the presence of clutter and basic visual functions such as visual field loss and contrast sensitivity.

Methods: Thirty-five participants aged 20 to 80 years with low vision due to a variety of visual disorders took part.

Visual impairment and postural sway among older adults with glaucoma.

Purpose: To investigate the effect of visual impairment on postural sway among older adults with open-angle glaucoma.

Methods: This study included 54 community-dwelling participants with open-angle glaucoma, aged 65 and older. Binocular visual field loss was estimated from merged monocular Humphrey Field Analyzer visual field results and retinal nerve fiber layer (RNFL) thickness was obtained from the Stratus Optical Coherence Tomographer.

Reading with optical magnifiers: page navigation strategies and difficulties.

Purpose: To read efficiently with a simple hand or stand magnifier, people with visual impairment have to move (navigate) the device along each line (forward phase) and back to the correct position at the start of the next line (retrace phase). Page navigation difficulties have been implicated as limiting factors when reading with hand and stand magnifiers, but have not been objectively measured.

Methods: Magnifier movements were recorded using a 3SPACE Isotrak system for 43 participants with age-related macular degeneration (AMD) who read two short stories using their habitual hand or stand magnifier.

Measuring mobility performance: experience gained in designing a mobility course.

Background: This paper reviews the most common methods of measuring and scoring orientation and mobility (O and M) and the effects of visual impairment on O and M. We discuss the difficulties inherent in designing a 'real-world' course to measure O and M and we describe the course that we finally used.

Methods: Thirty-five participants in two age groups, with low vision due to a variety of disorders, took part in mobility trials on the final version of the course.

Short-term in-office practice improves reading performance with stand magnifiers for people with AMD.

Purpose: People with low vision often use optical low vision aids to assist reading. There have been numerous training programs recommended to train people using magnifiers for reading. However, most of the programs are time consuming and labor intensive.

The development of the LV Prasad-Functional Vision Questionnaire: a measure of functional vision performance of visually impaired children.

Purpose: To develop a reliable and valid questionnaire (the LV Prasad-Functional Vision Questionnaire, LVP-FVQ) to assess self-reported functional vision problems of visually impaired school children.

Methods: The LVP-FVQ consisting of 19 items was administered verbally to 78 visually impaired Indian school children aged 8 to 18 years. Responses for each item were rated on a 5-point scale.

Prescribing near magnification for low vision patients.

Most patients with low vision request help with reading. Despite improvements in the assessment of visual functions, determining the appropriate magnification for reading still often involves a trial and error approach. Recent research has shown that with accurate and systematic assessments of vision, the required magnification can be predicted but this magnification needs to be much higher than has been previously recommended.

Preferred walking speed for assessment of mobility performance: sighted guide versus non-sighted guide techniques.

BACKGROUND: If visually impaired people had their sight fully restored, it is assumed that they would walk at their optimal speeds. Previous mobility studies have used preferred walking speed (PWS) to measure walking efficiency of visually impaired adults. Therefore, the actual speeds that visually impaired people adopt on a route can be expressed as a percentage of their preferred walking speed (PPWS).

Vision and mobility performance of subjects with age-related macular degeneration.

Purpose: To investigate the effects of age-related macular degeneration (ARMD) on mobility performance and to identify the vision determinants of mobility in subjects with ARMD.

Methods: Walking speed and the number of obstacle contacts made on a 79-m indoor mobility course were measured in 21 subjects with ARMD and 11 age-matched subjects with normal vision. The mobility measures were transformed to percentage preferred walking speed and contacts score.

Multi-disciplinary low vision care.

Case reports for three patients with low vision due to different ocular diseases are presented. In each case, a different rehabilitation professional was the main provider of the low vision care needed to meet the patient's goals. However, in all cases the patients benefited from the services of a range of professionals, agencies or groups for visually impaired people.

Reading performance in children with low vision.

PURPOSE: While educators and optometrists are concerned with reading efficiency in children with low vision, in most low vision assessments, children's reading performance is assessed only by a brief evaluation of reading fluency. We examined the relationships between clinical vision measures and reading performance in children with low vision. METHODS: Subjects were 71 students with low vision, aged seven to 18 years.

Determining magnification for reading with low vision.

Background: In the past, practitioners have used distance and/or near visual acuity (VA) to calculate required magnification for low vision aids. Magnification was usually under-estimated when compared with the final magnification prescribed. Recent studies have emphasised the importance of acuity reserve in determining the required magnification for optimum reading rate.