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01-03-2012 | General practice | Article

Visually impaired individuals should be offered range of color temperature illuminations


Free abstract

MedWire News: A range of color temperature illuminations should be offered to all visually impaired individuals prescribed an optical magnifier for near tasks to optimize their reading ability, suggest findings from a study published in Clinical and Experimental Optometry.

James Wolffsohn (Aston University, Birmingham, UK) and colleagues explain that light-emitting diode (LED) technology, which is available in many recent magnification devices, overcomes a number of drawbacks of traditional low vision aids illuminated by tungsten bulbs, such as their inefficient use of power, low brightness, and short life span.

They are also available in a range of color temperatures. However, "the optimal color temperature and the optimal method of prescribing this clinically are yet to be determined," they say.

The researchers therefore assessed the effect of varying color temperatures of LED-illuminated stand magnifiers on near visual function in the visually impaired.

A total of 107 participants were included in the study, with an age range of 37 to 96 years. The principal cause of visual impairment was age-related macular degeneration (n=91), followed by diabetic retinopathy (n=8), retinal detachment (n=2), and other ocular conditions (n=6). Visual acuities ranged from 6/9 to 0.5/60.

Eighty-five participants were experienced users of optical magnifiers, with the remainder having been prescribed magnifiers in a clinic assessment immediately before study enrollment.

Reading ability (maximum reading speed, critical print size, and threshold near visual acuity) using Radner charts was assessed in all participants using three stand magnifiers with LED illumination color temperatures of 2700, 4500, and 6000 K.

Participants were also asked to rank each of the three color temperature illuminations on ease of reading, comfort, and overall preference (best, in between, or worst performance).

Wolffsohn et al report that the preference for color temperature was evenly spread, with 36 participants preferring 2700K, 34 preferring 4500 K, and 36 preferring 6000 K.

Color preference and dislike were unrelated to distance visual acuity, prescribed magnification, and age. There was also no difference between new and experienced low vision aid users in reading ability or preference for the color temperature of the illumination.

Patients had a significant 19% improvement in near acuity, 10% improvement in critical print size, and a 9% improvement in maximum reading speed with their preferred rather than least-liked color temperature illumination. Near from distance acuity also improved by 18%.

"Thus, magnifiers that offer a range of illumination color temperatures will benefit a larger number of patients," write the authors.

They conclude: "It should be considered best practice that a range of illuminations of different color temperatures is offered to all visually impaired individuals who are prescribed an optical magnifier for near tasks to optimize their reading ability."

By Nikki Withers

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