Use of prismes in narrowing of visual field

Tunnel vision is the lost of peripheral visual field associated to a normal central visual field. It is due to glaucoma, retinitis pigmentosa, choroideremia a/or Usher syndrome. The visual field narrows up to 20°. Apical scotoma is due to prismes. Field extension is a field substitution, field expansion is an increase of the total area of visual field. Our goal is to avoid diplopia. The use of prism may be responsible of: spatial distortion, chromatic aberration, image alteration and astigmatic error. Fresnel prism is thinner and lighter but it reduces visual acuity and contrast more than CR39 conventional prism. Sectorial prismes are usual Fresnel prismes. The Author wants to stress the use of In Wave lenses, Fresnel multiple prismes, and TRI-FIELD lenses to reduce the clinical effects of the tunnel vision. The Author describes advantages and disadvantages of these lenses.