Mindblown: a blog about philosophy.

Vision which cannot be corrected with ordinary ophthalmic lenses well enough so the person can perform every-day visual tasks, but which is not so poor as to qualify the person as legally blind; usually considered to be in the range from about 20/50 to 20/200. A person is considered legally blind if the corrected visual…

The difference in stimulus effectiveness (brightness) of two pencils of light incident on the same retinal point, one passing through the center of the pupil and the other passing through an eccentric part of the pupil, the central pencil producing a more intense response.    

Method of determining the topography of the cornea by means of a stereoscopic photographic technique, similar to the technique used in making contour maps.  

Method of making optical computations in which vergence of light is calculated separately for each surface impinged upon by the light, rather than by making use of a formula.  

Refraction of the eye referred to the primary focal point of the eye and corrected by a lens placed at the eye’s primary focal plane.  

A method of illumination used in slit lamp biomicroscopy, in which the source and the microscope are placed at equal angles from the normal to the corneal surface, so that the surface observed will be illuminated by the image of the source. The reflection of sound waves from the surface of an internal structure, which…

Blurred vision occurring after contact lenses have been removed and replaced with spectacle lenses, due to temporary deformation of the corneal surface.  

Solution in which contact lenses are placed when not being worn, in order to maintain hydration of the lenses and to resterilize them.  

A back surface curve of a contact lens which is just peripheral to the base curve, is a certain number of millimeters (or diopters) flatter than the base curve, and averages 1.0 mm. or more in width.