Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Carbohydrate doai
Patent
1985-12-03
1987-12-29
Brown, J. R.
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Carbohydrate doai
A61K 3170
Patent
active
047161540
DESCRIPTION:
BRIEF SUMMARY
This invention is concerned with a substitute for vitreous humor to be used in ophthalmology, consisting of a gel of crosslinked hyaluronic acid, and a method at retinal surgery and after vitrectomy when the vitreous humor completely or partially is exchanged for such a gel.
The vitreous humor of the eye, also known as "vitreous body", is a transparent gel-type material occupying an intraocular space which extends forward from the retina to the lens and ciliary body, these latter two formning (normally) the frontal boundary of said space while the retina forms the rear boundary. The retina comprises two layers which are not organically connected with each other over their entire area. The layer immediately adjacent to the vitreous humor, i.e. the receptor layer, contains photosensitive cells while the layer adjacent to the choroid consists of pigment epithelial cells. If fluid penetrates through the receptor layer this may result in a separation of the two layers, that is, in detachment of the retina. Usually this will occur when a hole has been torn in the retina and morbid changes have occurred in the vitreous humor.
Treatments in cases of retinal detachment imply closing the rupture by means of for example a coagulation method such as e.g. cryopexy and contacting the detached retina with the pigment epithelial layer and the choroid. This latter step may be carried out by means of an inward buckle impressed from the outside on the sclera and choroid, or by means of injection of some substance that will increase the volume of the vitreous humor and thereby increase the pressure exerted by the vitreous humor on the retina.
For this last-mentioned method, a number of substances have been tried as substitutes for vitreous humor in cases where recourse has been had to vitrectomy (complete or partial removal of the vitreous humor by surgery) as e.g. after hemorrhages that have not been resorbed satisfactorily or after membrane ingrowth with concomitant retinal detachment due to traction. Examples of such substances are: Gases, salt solutions, silicone oil, polyvinyl pyrrolidone, hyaluronic acid, and hydrogels of the polyacrylamide type as well as polyglyceryl methacrylate.
An ideal vitreous humor substitute will have to possess a high degree of transparency and about the same refractive index as the vitreous humor. The substitute has to be a non-toxic, non-inflammatory, non-immunogenic substance. Moreover, it must be a substance that can be applied easily, for example by injecion through a fine needle tip, without undergoing any deterioration of its properties while being thus applied; and in some cases a further requirement is that this substance should be capable of controllable swelling. This substance may be required to act as a support during a prolonged period of time and should therefore be a material--preferably gel material--that is not easily degraded or decomposed. In cases of retinal detachment, a complication occurring fairly often is that secondary reactions show up in the form of cellular growth, concomitant membrane formation and traction forces exerted on the retina. It is therefore a highly important requirement that the substitute material introduced should not be a cell growth substrate.
The aforesaid vitreous humor substitutes of the prior art have serious drawbacks in one or more respects. Thus for instance, silicone oil while being an efficient substance for promoting attachment of the retina has a high frequency of side effects in the form of cataract formation, glaucoma and toxic effects on the tissues of the eye. Among the gaseous substitutes, the one that has been employed most commonly and for many years is air--which however, like several other low molecular substances tested, has the disadvantage of being eliminated too quickly so that consequently the retina is not held in a fixed position long enough for effective healing. Hyaluronic acid is a substance normally present in the eye; therefore injection of hyaluronic acid will not give rise to any toxicological or immunological re
REFERENCES:
patent: 4141973 (1979-02-01), Balazs
patent: 4152170 (1979-05-01), Nagase et al.
Laurent et al, Acta Chemica Scandinavica, vol. 18, p. 279, 1964.
Lindqvist Bengt L.
Malson Tomas
Brown J. R.
Peselev Elli
Pharmacia AB
Philpitt Fred
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