Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Patent
1997-06-13
1999-02-23
Mai, Huy
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
351215, 351221, A61B 310
Patent
active
058750193
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a system for the determination, the evaluation and the voluntary control of the refractive and accommodative status of the eye. The system includes a scanner, completely or partially consisting of material having the capacity of polarizing the optical radiations, and a target consisting completely or partially of material having the same polarizing capacities. The uneasiness sometimes linked to the accommodation, i.e. to the power increase of the optic eye system, mainly due to the shape variation of the crystalline lens, is well known, as well as the need of evaluating the exerted accommodation and its entity.
Also the need of evaluating the kind and the entity of the refractive error or ametropia is known, i.e. the surplus or lack of power of the eye, such as not to allow--in conditions of not exerted accommodation--the correct focusing on the retina of the image of a target placed at the optical infinity.
A power surplus determines the formation of the image before the retina (myopia), a lack of power determines the formation of the image beyond the retina (hypermetropia), a difference of power between the two meridians of the optic system causes the formation of two images in the shape of segments perpendicular to each other (astigmatism).
The main aim of the present invention is allowing the evaluation of the kind and entity of refractive error of the eye, the measuring of the exerted accommodation, the voluntary control of the accommodation and of the reduction or the solution of psychophysical uneasiness and the consequences thereof connected to accommodation.
The aim set forth is reached by means of the system for the determination and control of the refractive and accommodative status of the eye according to the present invention, consisting of: corrected or not, and completely or partially consisting of material polarizing the optical radiation, and divided into two parts with polarization axis perpendicular or nearly perpendicular to each other. The visual axis of the eye to be examined passes near the separation line between the two polarized half-fields or through the same; polarizing the optical radiation, having the polarizing axis parallel or nearly parallel, perpendicular or nearly perpendicular to each other, possibly including means for moving the parts and possibly means for rotating all or a part of the target onto the longitudinal axis, so that as the scanner and the target lie on front-parallel planes or on nearly front-parallel planes, and as the scanner is placed, with respect to the target, in such a way that the polarizing axis of the polarized parts of the target is as parallel and/or perpendicular as possible to the polarization axis of each of the polarized parts of the scanner, only the optical radiation, coming from the non-polarized parts and from the parts of the target polarized parallel to the polarization axis of the part of the scanner, passes from one of the polarized parts of the scanner; while the optical radiation coming from those parts of the target polarized perpendicularly to the axis, does not pass or passes in a negligible quantity. Furthermore, the target may be projected onto appropriated screens, like virtual or real screen(s), by means of appropriate means.
For what concerns the image seen through the scanner, there are two alternatives in which the polarized parts of the target are seen by contrast with the background: that the background and the polarized part(s) of the target with polarization axis perpendicular to one of the polarized parts of the scanner, seen from the part of the scanner, have a similar luminance, such as to be not, or nearly not, distinguished due to lack or shortage of contrast between target and background, while the part(s) of the target with the polarization axis parallel to that of the part of the scanner are seen, through the part, light, i.e. bright, on a dark background, and may be distinguished from same. A similar process is deserved for the other part of the scanner; luminance, sufficient f
REFERENCES:
patent: 3880501 (1975-04-01), Munnerlyn
patent: 5258791 (1993-11-01), Penney et al.
patent: 5787890 (1998-08-01), Reiter et al.
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