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Acute immunogenic uveitis was modeled in rabbits via the subcutaneous and intravitreal injections of normal horse serum. We studied the effect of instillations of 0.1% melatonin solution on the clinical course of uveitis and biochemical parameters of tear fluid and aqueous humor: antioxi-dant activity, protein concentration and α(2)-macroglobulin level. Melatonin instillations decreased clinical manifestations of uveitis. We found that the antioxidant activity in tears of the rabbits treated with melatonin was substantially higher and the α(2)-macroglobulin level lower than in untreated animals. Antioxidant activity in aqueous humor taken on day 10 of uveitis was also twice higher while protein and α(2)-macroglobulin levels were 1.5-2 times lower than in untreated animals. These data indicate that instillations of melatonin increase the local antioxidant activity and decrease the acuity of inflammation and permeability of hematoophthalmic barrier in uveitis.

A considerable tear endothelin-1 increase (2-3 times) has been found in patients with primary open-angle glaucoma and proliferative diabetic retinopathy. Patients with proliferative retinopathy also showed an increase of plasminogen level in tear fluid and a tendency of a similar increase in blood serum. No correlation between endothelin-1 and plasminogen levels in these pathologies was established. Tear endothelin-1 and plasminogen measurement could be used as an informative and non-invasive method to help prognosis making, condition severity evaluation and control the effectiveness of treatment of ocular local microcirculatory disturbances.

The pattern of functional impairments and the antioxidative and antiproteolytic status of tear were studied, by experimentally simulating retinal ischemia in rabbits and during treatment with Selecarten. Simulated retinal ischemia resulted in the development of persistent (up to 3 weeks) retinal electrogenetic disorder. Selecarten instillations produced a moderate neuroprotective effect, by positively affecting retinal function early after ischemia stimulation and accelerated the recovery of retinal electrogenesis late after laser coagulation of retinal vessels. The altered metabolic processes were characterized by an increase in the tear antiproteolytic potential. The antioxidative activity and the activity of a2-macroglobulin proteolysis inhibitor increased in the tears of Selecarten-treated rabbits.

The nitric oxide (NO) donors Na nitroprusside and L-arginine were tested for their effects on the course of experimental immunogenic uveitis, antiproteolytic and antioxidative activities in the rabbit tear and blood. With the use of the NO donors, the course of uveitis was shown to be more severe and prolonged. In uveitis, there was a change in the activity of the antiproteinases--alpha1-antitrypsin and alpha2-macroglobulin and the antioxidative enzymes superoxide dismutase in both tear and blood. The magnitude of changes in the biochemical parameters under study suggested that the course of uveitis was more severe in the rabbits given the NO donors. Thus, the inclusion of the NO donors in the active phase enhances an inflammatory reaction in immunogenic uveitis.

The present paper deals with the study of the efficiency of oral use of the antioxidative drug Immugen (a complex of alpha-tocopherol, oubichinone, selenium aspartate, methionine, and soyabean phospholipids) on a rabbit model of severe alkaline-induced corneal burn. The investigations have indicated that addition of Immugen to the rabbit feed exerts a significant positive effect on the parameters of the local antioxidative system of the eye and causes an increase in the activity of superoxide dismutase and catalase, and, on day 14, in antioxidative activity. The early experimental periods were marked by a slight rise in the frequency of deep corneal ulcerations. Moreover, the long-term clinical effect of use of Immugen appears as a significant increase in the area of the transparency-preserving affected cornea. The findings suggest that the antioxidants can show their optimal effect in the complex therapy for burn processes, including the use of proteinase inhibitors.

Proteinase-inhibitor balance in the lacrimal fluid in eye burns was studied in rabbits with modified and intact immune status. Stimulation of the immune system was induced by complete Freund's adjuvant. Clinical picture of the disease was studied in parallel. Immunization accelerated the local adaptive and defense reaction of the proteolytic enzymes and their inhibitors, which was paralleled by a more benign course of burn disease of the eyes, in comparison with that in non-immunized animals.

Chemical burns of the eye of different location (cornea, corneal fragment with adjacent conjunctiva, and limbus) were studied in experiments. Clinical picture and changes in the lacrimal proteinase inhibitor balance were analyzed. Burn disease is less severe and the number of complications is less if a fragment of the cornea with adjacent conjunctiva and a fragment of the limbus are injured than in case of a corneal burn of the same depth and area. Burn of the total limbus area is a severe injury involving essential shifts in the proteinase inhibitor balance, leading to deep organic changes in the cornea and inner structures of the eye, eventuating in its subatrophy.

The content of potassium ions in the lacrimal fluid was evaluated before and in various periods after laser specialized keratomileusis (LASIK) in order to determine the scope and terms of therapeutic measures. Seventeen patients with myopia were examined before and after LASIK. Lacrimal production before the operation was evaluated by Schirmer's and Norn's tests. The concentration of K+ ions in the lacrimal fluid was measured on a Reflotron IV biochemical analyzer. Before operation the concentrations of potassium ions were 1.5 times higher than normally in the patients complaining of discomfort. Lacrimal concentration of K+ ions and results of Norn's and Schirmer's tests were in high correlation. After LASIK potassium ion concentrations were increased in all patients and returned to the initial level almost completely within 1 week postoperation. Treatment with artificial tear preparations containing no potassium ions during the early postoperative period is physiological.