Cataract is one of the most expensive diseases in the farming of Atlantic salmon (Salmo salar L.). In addition to the economic implications, the production of fish with visual disturbance raises ethical questions. Lens changes vary from small opacities, mainly at the anterior pole to complete cataracts. Rapidly developing cataracts frequently lead to increased water uptake, swelling of the lens fibres and occasional rupture of the posterior lens capsule. The cause of cataracts in farmed salmon may be considered multifactorial, with both dietary factors as well as environmental factors involved in cataractogenesis.
In wild migrating postsmolt salmon, osmotic cataracts have been diagnosed in a substantial number of fish during the last years. The changes vary from a hazy opacity in the anterior lens to cataracts causing blindness. Severely affected lenses appear swollen, and large vacuoles can be found in the opaque areas. Defective osmoregulation is the most likely explanation for the lens changes.

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Clinical ocular examinations include a wide spectrum of visual tests that cover a brief gross observation and a detail check using specifically designed instruments. Amongst the examinations, the retina is qualitatively monitored for any absence of the nerve fiber layer with a funduscopy using a filter that cuts red light. In recent years, a Nerve Fiber Analyzer has become available and has been frequently applied to the retinal examination in a field of human ophthalmology. The Nerve Fiber Analyzer determines the thickness of the nerve layer of the retina, and thereby enables us to quantitatively evaluate the layer^1-3). Glaucoma is one of the primary ocular diseases where the nerve fiber layer should be carefully examined^1-3). Yet, in a field of veterinary medicine, glaucoma is commonly evaluated for the progression and therapeutic index by intraocular pressure and a funduscopic observation. Thus, it would be highly recommended that the Nerve Fiber Analyzer be applied to the field of veterinary medicine in order to better ascertain the clinical stage of glaucoma. Questions may be raised for the possible application, however, because the Nerve Fiber Analyzer is designed for use in human ophthalmology and because there are anatomical dissimilarities in the dog eye from the humans such as presence of tapetum and the larger posterior segment of the eyeball in dogs. This communication details practical aspects and strengthens the usefulness of the Nerve Fiber Analyzer in the field of veterinary medicine.

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We examined the acute inflammatory response of five the Japanese White rabbits following paracentesis by investigating the breakdown of the blood-aqueous barrier (BAB). Nitrite, prostaglandin E₂, and protein accumulations in the aqueous humor were measured after paracentesis. Thirty minutes after collecting the rabbit's primary aqueous humor, the secondary aqueous humor was collected. Nitrite, prostaglandin E₂, and protein concentrations in the secondary aqueous humor had significantly increased compared with those of the primary aqueous humor; the average concentrations in the former being 6.55 ± 1.05 μmol/l, 274.42 ± 10.37 pg/ml, and 22.70 ± 5.70 mg/ml, respectively, while those in the latter were 4.11 ± 0.54 μmol/l, 3.34 ± 0.11 pg/ml and 3.69 ± 0.20 mg/ml, respectively. These findings indicated the possibility that the change of NO in the aqueous humor following paracentesis plays an important role in the breakdown of BAB in connection with prostaglandin E₂ and protein.

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