Comparing Low-cost Handheld Autorefractors - a Practical Approach to Measuring Refraction in Low Resource Settings

Non-communicable diseases (NCDs) are a large and increasingly costly problem for India. Recent research estimates that NCDs could cost the Indian economy US$6.2 trillion from 2012-2030 if left unaddressed. For some NCDs, new solutions will need to be developed for diagnosis and treatment, while, for others, the necessary interventions exist but are not readily available to all who need them. Visual impairment is one area of health in which limited access to diagnostic and treatment technologies jeopardizes the health and economic well-being of the population. This is particularly true in India, where the population is rapidly aging and, despite the presence of some high-quality medical facilities, there remains a large burden of unaddressed visual impairment.

Loss of visual acuity can negatively impact individual and household income by reducing productivity or hours worked among the visually impaired; it can also affect economic wellbeing via the need for caretakers. There are two key tests that determine visual acuity and measure vision loss:

1. Basic visual acuity (BVA), which is assessed using the naked eye or, when applicable, eyeglasses, and
2. Best-corrected visual acuity (BCVA), which uses refraction to determine eyeglass/contact lens prescription.

In addition, diagnosing vision-hindering eye conditions requires specific medications or surgical procedures. Diagnosis of glaucoma, cataracts, or diabetic retinopathy typically requires a physician to examine a patient's retinas, corneas, and/or pupils at close range using specialized equipment, in conjunction with the visual acuity tests described above.

BCVA tests typically require heavy, cumbersome, and expensive equipment such as phoropters (instruments that measure the refractive state of the eye). Likewise, eye diseases typically require the use of specialized equipment such as slit lamp microscopes, ophthalmoscopes, and tonometers.

However, the recent and anticipated availability of affordable and lightweight portable technologies which can be used both by medical professionals and by trained laypeople has made eye testing easier and faster. This study will validate a number of new handheld devices developed for visual acuity measurement and retinal imaging.

This study explores testing for visual acuity and other impairments like diabetic retinopathy, glaucoma, age-related macular degeneration (AMD), and cataract without the use of traditional stationery and expensive instruments such as phoropters and conventional autorefractors and at a comparatively low cost. If the devices are proven able to accurately evaluate visual acuity and produce high-quality retinal images that can be used to aid diagnosis, it will be a breakthrough in reducing barriers of access to eye care facilities encountered by the majority of the rural population in India and other developing countries.

Also, since these devices are convenient and relatively easy to use, they can be easily used in household/community surveys involving vision measurement; the investigators are proposing to perform data collection for this study in India partially in order to investigate the potential for use of one or more of handheld devices in upcoming waves of the Longitudinal Aging Study in India (Protocol Number 16715), a nationally-representative aging and retirement study that collects data on multiple dimensions of aging, including socioeconomic, cognitive, and health indicators with the aim of informing national policy and practice relating to older adults. Specifically, the study involves an extensive biomarkers module which includes direct measurement of multiple medical and anthropometric indicators, such as blood pressure, grip strength, lung function, height, and weight. The current version of the biomarkers module calls for the use of a traditional eye chart to measure BVA; however, future versions of the study would greatly benefit from the use, if feasible, of portable and inexpensive devices which would allow researchers to collect richer and more accurate data on visual acuity and/or eye conditions and therefore provide a more detailed picture on older adults' eye health, as well as the predictors and correlates of eye health, on a national level.

Through the data gained from this study, the investigators hope to be able to develop useful recommendations for researchers, community health organizations, and health care professionals whose studies and patients would benefit from access to relatively low-cost portable vision measurement and retinal imaging devices. In particular, Indian consumers will have access to all devices pending market approval.