Visual defects associated with vigabatrin: a study of epileptic argentine patients.

OBJECTIVE: The aim of the present study was to assess visual alterations in a population of Argentine patients treated with the antiepileptic drug vigabatrin. METHODS: Twenty patients receiving vigabatrin and 15 patients receiving carbamazepine were examined with automated perimetry using a Humphrey 120-point full screening strategy. In addition, scotopic flash electroretinograms were performed. RESULTS: Of 20 patients treated with vigabatrin, two were unable to cooperate with testing. Of the remaining 18 patients, all but two showed at least one non-detected point inside the central 40 degrees of the visual field of each eye. Of the 15 carbamazepine-treated patients, three were unable to perform the study. None of the remaining 12 patients showed visual field defects. Both a- and b-wave amplitudes of the scotopic electroretinogram were significantly reduced in 12 patients receiving vigabatrin. CONCLUSIONS: Visual field defects among patients on vigabatrin therapy may occur with a higher frequency than previously recognized. The Humphrey 120-points full field screening test and electroretinography are useful tools to assess the visual dysfunction associated with vigabatrin.

Effect of hyaluronic acid on intraocular pressure in rats.

PURPOSE: To study the effect of acute or chronic intracameral injection of hyaluronic acid on intraocular pressure (IOP) in rats. METHODS: Acute or chronic injections of hyaluronic acid were performed unilaterally in the rat eye's anterior chamber, whereas the contralateral eye was injected with saline solution. IOP was assessed daily or weekly by a tonometer in conscious rats. IOP was also assessed in both experimental groups at several intervals during the light-dark cycle. RESULTS: A single injection of hyaluronic acid induced an increase of IOP that lasted for 8 days (P < 0.01), whereas its chronic administration during 9 weeks induced a significant and sustained increase in IOP, compared with the eye injected with vehicle (P < 0.01). This hyaluronic acid-induced hypertension was significantly decreased by the application of 1 drop of brimonidine (0.2%), latanoprost (0.005%), or timolol (0.5%). Significant daily variations of IOP were observed in both control and hyaluronic acid-injected eyes, peaking during the dark phase (P < 0.001, ANOVA). CONCLUSIONS: These results suggest that the intracameral administration of hyaluronic acid could be a model of ocular hypertension in rats.

Developmental changes in accommodation evidenced by an ultrabiomicroscopy procedure in patients of different ages.

We demonstrate that changes in the behaviour of the contractile ciliary muscle accompanied by augmented rigidity of the lens are the most important aspects in the loss of accommodation. With ultrabiomicroscopy (UBM), we demonstrated that the performance of the ciliary muscle is diminished and accompanied by rigidity of the lens. Both lens thickness and trabecular-ciliary process distance (TCPD) were the parameters that showed major alterations with the loss of accommodation in patients of different ages. The results indicated that the differences between these parameters in farsightedness and nearsightedness in the different groups of patients were positively correlated.

Presbyopia: a new potential pharmacological treatment.

Presbyopia occurs after 40 years of age in humans with a progressive loss of accommodation. Accommodation depends on the contraction of the ciliary muscle and iris, lens changes and convergence. The parasympathetic system regulates the degree of ciliary muscle and iris contraction necessary to modify the shape and position of the lens and its stimulation is effective through the activation of muscarinic receptors that are present in both structures. The hypothesis proposed here suggests the correction of accommodation in emmetropic presbyopic patients using a pharmacological treatment that includes a cholinergic agent combined with non-steroidal anti-inflammatory drugs (NSAIDs). This drug combination can restore near vision without affecting distance vision. It is important to note that the pharmaceutical form used was devoid of any inflammatory or other collateral effects.

A new experimental model of glaucoma in rats through intracameral injections of hyaluronic acid.

An experimental model of pressure-induced optic nerve damage would greatly facilitate the understanding of the cellular events leading to ganglion cell death, and how they are influenced by intraocular pressure and other risk factors associated to glaucoma. The aim of the present report was to study the effect of a long-term increase of intraocular pressure in rats induced by intracameral injections of hyaluronic acid with respect to electroretinographic activity and retinal and optic nerve histology. For this purpose, hyaluronic acid was injected weekly in the rat anterior chamber of one eye, whereas the contralateral eye was injected with saline solution. The results showed a significant decrease of oscillatory potentials and a- and b-wave amplitude of the scotopic electroretinogram after 3 or 6 weeks of hyaluronic acid administration, respectively. These parameters were further reduced after 10 weeks of treatment with hyaluronic acid. No significant changes in anterior chamber angle structures from hyaluronic acid- and vehicle-injected eyes were observed, whereas a significant loss of ganglion cell layer cells and of optic nerve axons were detected in animals that received hyaluronic acid for 10 weeks, as compared to eyes injected with saline solution. In summary, present results indicate that the chronic administration of hyaluronic acid induced a significant decrease in the electroretinographic activity and histological changes in the retina and optic nerve that seem consistent with some features of chronic open-angle glaucoma. Therefore, this could be an experimental model to study the cellular mechanisms by which elevated intraocular pressure damages the optic nerve and the retina.