Etching a substrate: processes – Forming or treating optical article
Patent
1995-08-15
1997-11-04
Powell, William
Etching a substrate: processes
Forming or treating optical article
216 41, 216 96, 606166, B44C 122
Patent
active
056835922
DESCRIPTION:
BRIEF SUMMARY
This invention concerns a method of fabricating a surgical cutting tool and a tool fabricated by such a method. More particularly, the tool of the invention is intended for accurate cutting of thin membranes within the human or animal body. The invention has particular application in eye surgery, and more specifically in cataract surgery, which requires cutting of the thin membrane of the eye's lens capsule.
Cataract accounts for more than half of all eye operations in western countries and the number of operations carried out is increasing with, among other things, the increase in life expectancy.
Cataract is defined as an opacity of the crystalline lens of the eye. It may be hereditary, i.e. passed on genetically from one generation to the next. It may be present due to infection of the patient's mother during pregnancy, and typically rubella can cause cataracts in this way. Certain congenital syndromes are associated with cataracts, e.g. Down's syndrome. Cataract may be acquired later in life from injury (either directly or indirectly from trauma or radiation), from disease, such as diabetes, from eye disease, such as uveitis, acute glaucoma, retinitis pigmentosa, or as a result of using certain drugs, such as steroids. Most commonly cataract is associated with the ageing process, akin to the whitening of hair or the ageing of skin. Changes occur within the lens of an otherwise perfectly healthy eye which render the lens gradually opaque. The changes include lens protein aggregation, increased amounts of insoluble lens protein and increased pigmentation of the lens nucleus.
The result of cataract is progressive deterioration in vision. The patient experiences initial blurring, glare, double or multiple images, then increasing loss of visual acuity and finally almost total blindness, although perception of light is retained. Such visual loss has a significant effect upon the development and education of neonates and children and the ability of adults to perform or continue with many functions including some, such as driving a motor car, upon which their livelihood may depend.
In later life such ability is a major factor determining whether such a person can continue to live an independent life.
At present, no satisfactory medical treatment for cataract and no effective methods of prevention have been found. The only treatment is the surgical removal of the lens, and such surgery is long-established and has a good rate of success.
The two common forms of cataract extraction are intracapsular and extracapsular extraction. In the first of these the zonule is dissolved with chymotripsin (an enzyme) and the whole lens (capsule, cortex and nucleus) is removed by means of a cryoprobe. This method was the more common until a number of years ago, but has now been replaced by that of extracapsular extraction, in which a small hole is made in the anterior lens capsule and the cortex and the nucleus are removed through this hole leaving the posterior part of the lens capsule in place.
Having had a cataract removed the eye is made long-sighted and an alternative means of focusing light on the retina must be found. The alternatives are cataract glasses, contact lenses or a perspex implant Known as an intra-ocular lens (IOL). The first two alternatives, though being very safe options from the point of view of biocompatability, suffer from major functional limitations. Spectacle lenses are located about 17 mm in front of the position of the crystalline lens which they replace. In this position a very high-magnification lens is needed resulting in a reduced field of view and an unnatural image magnification. When the latter condition exists unilaterally, stereoptic fusion, the blending of perceived images from the two eyes, becomes impossible.
Contact lenses do not present this problem since their image magnification is not required to be so high. However, their manipulation and placement presents practical disadvantages and, in the case of the elderly who make up the majority of the patients, it can be almost impossible
REFERENCES:
patent: 3926601 (1975-12-01), Hicks
patent: 4968585 (1990-11-01), Albrecht et al.
patent: 5156607 (1992-10-01), Kansas
patent: 5248383 (1993-09-01), Hanada
patent: 5302234 (1994-04-01), Grace et al.
"Micromachined silicon surgical tool", Machine Design, vol. 62, No. 23, Nov. 1990, p. 32, XP000176637.
Bartholomew Richard Shiayle
Ensell Graham John
Yang Shih Jung Eric
British Technology Group Limited
Powell William
LandOfFree
Surgical cutting tool does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Surgical cutting tool, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Surgical cutting tool will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1830357