Projection-simulated ametropia. A model for teaching subjective refraction.

Teaching subjective refraction techniques ("refractometry") is enhanced by having the student experience the effect of each lens change "through the eyes of the patient." A projector, positioned behind the phoropter, projects a visual acuity chart through the phoropter onto the far wall. "Unknown" refractive errors are simulated by attaching trial lenses to the lens barrel of the projector, and the student progressively clears the projected image as he learns the standard steps of subjective refractometry. The focus sensitivity of each lens change can be varied, if desired, by stopping down the projection system. This simulation, which uses equipment readily available in most ophthalmology offices, has proven useful for both demonstration and practice.