Low Vision and Vision Rehabilitation
Core concepts
Understand the goals of low vision rehabilitation: maximize remaining vision for daily activities. Know the types of magnification (relative distance, relative size, angular), and the devices used: magnifiers, telescopes, electronic magnification, and prisms. Understand the role of contrast enhancement, lighting, and non-optical aids. Be familiar with the assessment of visual acuity, contrast sensitivity, and visual fields in low vision patients.
Traps
Questions often confuse the types of magnification. Relative distance magnification increases with closer viewing; relative size magnification increases the object size. Telescopes are for distance; magnifiers for near. Do not recommend a device without considering the patient's task and field of view.
Worked rule of thumb
Calculate required magnification as the ratio of desired acuity to present acuity. For a patient with 20/200 who wants to read 20/40 print, the required magnification is 5×. Choose a device that provides that magnification at the working distance the patient can tolerate.