Understanding how simple magnifiers provide image enlargement.

The simple magnifier is a positive power, usually single lens placed between the page and the eye to give an enlarged image. Its 'magnification' is typically expressed as its dioptric power divided by four but this presumes that the reader uses the magnifier in a specific way. Magnifiers rarely meet their rated specification so they often disappoint the expectations of both patients and eye-care practitioners for vision improvement.

Relationship between vision impairment and ability to perform activities of daily living.

Purpose: To determine the relationship between clinical measures of vision impairment and the ability to perform activities of daily living (ADLs).

Methods: One hundred and twenty subjects with low vision from a variety of causes participated in the study. Vision impairment was assessed under binocular conditions by measuring distance visual acuity, near word acuity, Melbourne Edge Test contrast sensitivity, Pelli-Robson Chart contrast sensitivity and visual fields.