Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Patent
1999-06-03
2000-07-18
Manuel, George
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
G02C 704
Patent
active
060897120
DESCRIPTION:
BRIEF SUMMARY
This invention concerns a method and device for improving colour discrimination.
In the United Kingdom colour blindness affects about 8% of the male population and about 1/2% of the female population. There are two main types of colour blindness. Deuteranopia (green deficiency) is the most common occuring in about 75% of cases and protanopia (red deficiency) occurs in about 25% of cases. There is a third condition, monochromatism, in which no colours are seen, that occurs in a small number of cases.
Attempts have been made to overcome the effects of colour blindness by fitting patients with a coloured contact lens. U.S. Pat. No. 3,586,423 described a method and device for improving colour discrimination in persons having a substantial amount of deficiency in their ability to discriminate between red and green colours. A rigid red coloured contact lens was applied to one eye.
That contact lens had a number of drawbacks. The first was that it was only useful for some patients. Secondly, the lens was cosmetically very poor and, thirdly, being hard, exhibited poor oxygen transmission.
U.S. Pat. No. 4,998,817 also discloses a contact lens for improving colour perception of patients suffering from colour blindness. The lens has central circular red coloured section matching the pupil eye.
An object of this invention is to provide a method and apparatus for use in improving colour discrimination without the aforementioned drawbacks.
According to a first aspect of this invention there is provided a it of parts for use in testing for correction of colour discrimination in a patient comprising a plurality of plastics contact lenses each having a substantially central tinted section of a different tint to the others.
According to a second aspect of the invention there is provided a method of improving colour discrimination of a patient by applying to at least one of the patient's eyes in sequence differently tinted contact lenses to assess which tint has optimum effect, each lens having a substantially central tinted section.
The substantially central coloured section of a contact lens for the invention will usually be circular and may be sized to match the normal pupil size of the patient. The colouring may be chosen to suit the particular colour recognition deficiency of the patient. Every patient will have a differing degree of colour blindness that may be better alleviated by a different colour and/or colour density than another patient. Therefore, the hue and/or the density of the colouration may be varied from one patient to another.
Additionally, a contact lens used in the invention may also be a prescriptive lens to correct any other vision impairment suffered by the patient.
A contact lens used in the invention will usually be worn in one eye, in which case either no lens or a clear prescriptive lens is worn in the other eye. However, for some patients it may be necessary for a tinted contact lens to be worn in both eyes. Ideally the correct eye, colour, filter size and contact lens fit will be decided following a clinical consultation.
The contact lens used in the invention is preferably made of a soft, high water content plastics material, such as Filcon 4A. The colour of the lens is preferably applied as a tint to the lens. The tint may be applied in a conventional manner.
The method of the invention may involve various tests and investigations. Firstly it is desirable to establish whether the patient is suitable for wearing contact lenses i.e. those with pathologically dry eyes are most unsuitable. Secondly, colour vision will be assessed by any convenient means. Then, a patient can be assessed for the appropriate contact lens of the invention.
In order to carry out the latter assessment, it is envisaged that a selection of different contact lenses of the invention will be provided, preferably in a single container and preferably in a given order, whereby a practitioner can try each colour/density available until the optimum lens for the patient is ascertained.
The preferred selection of contact lenses f
REFERENCES:
patent: 5617154 (1997-04-01), Hoffman
patent: 5846457 (1998-12-01), Hoffman
patent: 5917573 (1999-07-01), Davis
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