Surgery – Instruments – Corneal cutter or guide for corneal cutter
Patent
1997-04-25
1999-10-12
Buiz, Michael
Surgery
Instruments
Corneal cutter or guide for corneal cutter
606167, 128898, A61F 214
Patent
active
059647752
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to refractive correction, by means of corneal tissue shaping, to compensate for deviations of the imaging system of an eye from normal focussing directly on the retina of the eye, and, in particular, to non-surgical means for effecting such correction.
BACKGROUND OF THE INVENTION
Two major methods of eye cornea reshaping, are in current use, for correction of abnormal vision, resulting from improper eye focussing (generally, the conditions of myopia, with the perceived image optimal focussing in front of the retina; hypermetropia (hyperopia), with the image optimal focussing beyond the retina; and astigmatism which combines symptoms of both myopia and hyperopia, on a localized basis). The first method, radial keratotomy, involves the surgical incision of the cornea of the eye with deep medial cuts which cause a predictable flattening of the cornea of the eye when the eye heals. The reshaped cornea of the eye, with changed curvature and concomitant changed refraction, causes light or optical rays associated with an image (the perceived image), passing through the lens of the eye, to be refocussed on the retina, with refractive compensation, such as for eye shape deviations from normal. This method is however a major surgical one, and requires considerable skill in proper utilization. Improper incisions can detrimentally permanently affect the eye, without recourse to ready correction. Scarring is not uncommon and some deaths have resulted. In addition, the correction may also vary with time.
The second major method for vision correction involves the use of the excimer laser which is on the verge of FDA approval for widespread use. The excimer laser operates by controllably ablating away portions of corneal tissue, mostly through photochemical disintegration of the tissue, to either increase or decrease the effective curvature of the front of the cornea (i.e. corneal tissue), thereby correctively refocussing images on the retina. While this procedure is less invasive and traumatic than the radial keratotomy, and has had no associated injuries in over 250,000 procedures, it is nevertheless accompanied by some heat generation and dehydration, for an extended period of time. The ablation technique leaves the surface structured on a microscopic scale, and also affects adjacent corneal surface tissue and, with the plumes, results in an inaccuracy of correction of up to one diopter or more deviation from the desired value. This compares unfavorably with corrective lenses and contact lenses which provide a more accurate correction to within 0.25 diopters deviation. In addition, some haze usually results from wound healing effects.
SUMMARY OF THE INVENTION
The present invention comprises a method and device for benign, non-surgical, external shaping of surface corneal tissue to compensate, by refractive correction, for deviations in the eye imaging system which prevent normal focussing directly on the retinal plane of the eye.
The imaging system of a human eye generally comprises the cornea, pupil, lens and retina. Image focussing is effected through the cornea, pupil and lens, and the image is normally focussed directly on the surface of the retina. Focussing power for the direct imaging on the retina, is dependent to a great extent upon the shape of the front surface of the cornea (about 70% of refractive power) and to a lesser extent (30%) on the eye crystalline lens. Accordingly, small changes in the shape and effective curvature of the front surface of the cornea will effectively correct for eye imaging system deviations, to properly refocus images on the retina. The relationship of surface corneal tissue removal to appropriate correction for eye deviations from normal, has been fully developed with respect to the excimer laser, as well as with contact lenses, which do the same thing, i.e., reshape the front surface curvature of the cornea. Contact lenses however, exhibit problems of their own with respect to their own surfaces and damage to cornea.
In accord
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Geskin Ernest S.
Gordon Eugene I.
L'Esperance, Jr. Francis A.
Buiz Michael
New Jersey Institute of Technology
Truong Kevin
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