The term refraction means to bend light. Your optometrist will use several methods to bend or change the direction of light coming from a distant object, to focus accurately on the retina by introducing different lenses before your eyes. When this is achieved, vision will be clearest. This results in the prescription for your spectacles or contact lenses. Refraction can only be accurate if the letter chart is at least 6 meters or 20 feet away from the patient. Any shorter, and the accuracy drops. To save space, most practitioners will use a mirror to double the distance.

Methods of Refraction

Retinoscopy

Retinoscopy is used as an objective method to determine the refraction without your interaction, that is without asking you “Which is better, 1 or 2?”

Autorefraction

An Autorefractor is a computerised instrument used to determine the refraction of your eyes. Again, this is an objective method that does not require the interaction of the subject. This method may not be sufficiently accurate and should not be used to dispense prescription spectacles unless the subject is unable to respond to other methods.

Manifest refraction

This is the traditional method used to determine the prescription for spectacle and contact lenses. Lenses are placed before your eyes until the best vision is achieved. Several methods based in science is used to determine when the end point is achieved.

Jackson Cross Cylinder

This method is used to determine the Astigmatism and its Axis.