PRISM LENSES

Fig:- Prism

Prism lenses are triangular or wedge-shaped piece of glass or plastic that displaces the bundle of light towards the base. When they are placed in front of the eyes, an object viewed through them will appear to be displaced towards its apex. During the clinical refraction, they are employed to measure the presence

and amount of any tropia or phoria. A standard trial lens set contains the following prism lens measured in diopter –0.5Δ, 1Δ, 2 Δ, 3Δ, 4Δ, 5Δ, 6Δ, 8Δ.10Δ,12Δ (Fig. 2.2).