Device for testing by applanation

Claim 1

In a device for testing intraocular pressure by applanation, a testing body of a precise predetermined weight having a central axis in the region of which said body is transparent, said body terminating in a flat bottom end surface which is optically planar and which is adapted to rest upon the eye of a patient, holding means for holding and guiding said testing body and having with respect to said body a clearance sufficiently great to remain entirely out of engagement with said body when its axis is vertical and if inadvertently touching said body, engaging the latter only at a localized spot with a force of friction which is so small that it is negligible when compared with the force resulting from the weight of the testing body, said body having an upper end surface opposed to said bottom, optically planar end surface thereof, illuminating means for illuminating through the upper end surface of said testing body and through the testing body in the transparent region adjacent its axis the area of engagement between the bottom optically planar surface and the front cornea surface of the eye which is being tested, so that with said illuminating means it is possible to observe the peripheral configuration of the planed area resulting from resting of said testing body at said bottom, optically planar end surface thereof on the cornea, said area of engagement between said testing body and cornea being visible through said testing body when viewed along a given line of sight, magnifying means located along said line of sight for providing an enlarged image of the area of engagement between said testing body and cornea, and indicating means also located along said line of sight for indicating at least approximately the extent to which said plane area of engagement between said testing Body and cornea deviates from a given value, said indicating means comprising, at said bottom end surface of said testing body, an inner circular area of a given radius and an outer surrounding annular area surrounding said circular area and having a color different therefrom, said testing body including a tubular casing having opposed open ends, nonmetallic transparent optical elements closing said opposed ends of said tubular casing and defining the bottom and upper end surface of said testing body, and a ring surrounding and fixed to said tubular casing to provide the testing body with a precisely predetermined total weight, said ring having an outer peripheral surface directed toward said holding means, and said holding means having a guide surface surrounding said outer surface of said ring with said clearance, said latter surfaces being smooth and polished to achieve a minimal friction if they should touch, said holding means terminating at its bottom end in an inwardly directed shoulder extending beneath said ring and said testing body having along its entire length between said ring and said bottom end surface a diameter which is less than the diameter of said shoulder and the outer surface of said body between said ring and bottom end surface thereof being free of any projections so that there are no obstructions between said ring and said bottom end of said testing body providing for free movement of said shoulder downwardly away from said ring without the possibility of engaging any obstructions.