Optics: eye examining – vision testing and correcting – Eye examining or testing instrument
Reexamination Certificate
2000-02-16
2001-10-09
Manuel, George (Department: 3737)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
C600S307000, C604S294000
Reexamination Certificate
active
06299305
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ophthalmic apparatus, and more particularly to an ophthalmic apparatus for measuring dryness of a cornea or a conjunctiva of an eye to be examined.
2. Description of Related Art
Right after blinking, a cornea of an eye is covered with a tear film of almost even thickness. This tear film, however, gradually breaks up (drys out), as the eye remains open. It is important to measure the time taken for the breakup (hereinafter, referred to as BUT (Breakup Time)) in order to detect a defect in the tear film. Besides an aqueous layer, the tear film consists of an oil layer on the outermost surface and a mucin layer on the side of the cornea. The aqueous layer is sandwiched between the two layers. The oil layer has a function of protecting moisture from evaporating and the mucin layer has a function of moisten the corneal surface uniformly. To examine a dry eye caused by reduction of moisture (tear deficiency such as Sjogren's syndrome) or by reduction of the mucin layer (Stevens-Johnson syndrome and the like), the BUT measurement is considered to be extremely important.
Conventionally, diagnosis of such a dry eye has been carried out as follows: first fluorescein, which is a fluorescent material, is applied to an eye to be examined, and then the eye is visually observed under a slit lump until it reaches predetermined dryness thereby measuring the BUT mentioned above.
However, in the BUT measurement as described above, dryness of a corneal surface is measured through observing development of dry spots on the corneal surface by an examiner based on his subjective judgement. Naturally, a different examiner leads to a different measurement result and the accuracy of the measurement depends on the examiner's experience. In addition there are other problems. One example is that it is extremely difficult to judge the dryness in the case where dry spots appear non uniformly.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide an ophthalmic apparatus for measuring dryness of a cornea or of a conjunctiva objectively so that highly reliable measurement results can be obtained easily without depending on an examiner's experience.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purpose of the present invention, as embodied and broadly described herein, an ophthalmic apparatus for measuring dryness of a cornea of an eye to be examined, the apparatus comprises a projecting optical system including a light source for projecting measurement light onto the cornea, a detecting optical system including a photodetector for detecting reflected light from a tear film by projecting the measurement light, arithmetic means for measuring time-varying changes in the dryness of a predetermined measurement region based on a result detected by the photodetector, and output means for outputting a measurement result obtained by the arithmetic means.
REFERENCES:
patent: 4747683 (1988-05-01), Doane
patent: 5807273 (1998-09-01), Suzuki
patent: 6159189 (2000-12-01), Finnemore et al.
patent: 0 232 986 (1987-08-01), None
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patent: 7-136120 (1995-05-01), None
patent: 9-201334 (1997-08-01), None
patent: WO 88/10089 (1988-12-01), None
Benedetto, D.A., et al., “The instilled fluid dynamics and surface chemistry of polymers in the preocular tear film,” XP-002136393, p. 887, Mar. 13, 1975.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Manuel George
Nidek Co. Ltd.
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