Efficacy assessment of a combined anticholinergic and oxime treatment against topical sarin-induced miosis and visual impairment in rats

Pilocarpine mediated excessive calcium accumulation leads to ciliary muscle cell senescence and apoptosis

The ciliary muscle constitutes a crucial element in refractive regulation. Investigating the pathophysiological mechanisms within the ciliary muscle during excessive contraction holds significance in treating ciliary muscle dysfunction. A guinea pig model of excessive contraction of the ciliary muscle induced by drops pilocarpine was employed, alongside the primary ciliary muscle cells was employed in in vitro experiments. The results of the ophthalmic examination showed that pilocarpine did not significantly change refraction and axial length during the experiment, but had adverse effects on the regulatory power of the ciliary muscle. The current data reveal notable alterations in the expression profiles of hypoxia inducible factor 1 (HIF-1α), ATP2A2, P53, α-SMA, Caspase-3, and BAX within the ciliary muscle of animals subjected to pilocarpine exposure, alongside corresponding changes observed in cultured cells treated with pilocarpine. Augmented levels of ROS were detected in both tissue specimens and cells, culminating in a significant increase in cell apoptosis in in vivo and in vitro experiments. Further examination revealed that pilocarpine induced an increase in intracellular Ca2+ levels and disrupted MMP, as evidenced by mitochondrial swelling and diminished cristae density compared to control conditions, concomitant with a noteworthy decline in antioxidant enzyme activity. However, subsequent blockade of Ca2+ channels in cells resulted in downregulation of HIF-1α, ATP2A2, P53, α-SMA, Caspase-3, and BAX expression, alongside ameliorated mitochondrial function and morphology. The inhibition of Ca2+ channels presents a viable approach to mitigate ciliary cells damage and sustain proper ciliary muscle function by curtailing the mitochondrial damage induced by excessive contractions.

Broad Spectrum Treatment for Ocular Insult Induced by Organophosphate Chemical Warfare Agents

Warfare organophosphates nerve agents constitute one of the prime threats to mankind on the battlefield and in the scenario of civilian terror. Exposure to organophosphate (OP) nerve agents dose-dependently result in incapacitation. They affect multiple organs, but the eye is one of the first and most frequently affected. Ocular OP insult may result in long-term miosis, impaired visual function, and ocular pain thus inducing functional incapacitation. The currently recommended military medical doctrine of using 1% atropine eye drops is far from being the optimal treatment. Although effective in reducing ocular pain and the miotic response, this treatment induces long-term mydriasis and cycloplegia promoting photophobia and restricted accommodation, which may result in further impairment in visual function. An optimal treatment must ameliorate the long-term ocular insult enabling rapid return of normal visual function, while avoiding the induction of mydriasis and cycloplegia side effects, which could possibly worsen the visual performance. Optimal treatment should also keep effects of misuse to a minimum. Work done in recent years examined treatments with various anticholinergic drugs alone or used in combination with oxime treatments and may offer improved efficacy in ameliorating the ocular insult. This review is a summary of the applied research in animals and will discuss clinical implications and possible alterations in treatment protocols following OP exposure. Taken together the data points toward the use of topical low concentrations of potent anticholinergic ophthalmic drops such as atropine or homatropine, which rapidly ameliorate the long-term OP-induced ocular insult.

Ocular surface histopathological insult following sarin and VX exposure and potential treatments in the rat model

Eye exposure to organophosphate (OP) chemical warfare irreversible acetylcholinesterase inhibitors, results in long-term miosis and impaired visual function. In contrast to the well-documented miotic and ciliary muscle spasm observed following chemical warfare, OP ocular exposure, little is known regarding the ocular surface histopathological insult. The aim of the present study was to determine the degree of the ocular surface insult following sarin or VX ocular exposure and to evaluate potential anti-cholinergic treatments in counteracting this insult. Rats that were whole body exposed to various sarin concentrations (0.049-43 μg/L; 5 min exposure), showed a dose-dependent miotic response and light reflex impairment. Following whole body sarin exposure, a dose dependent ocular surface histopathological insult was developed. A week following exposure to a low concentration of 0.05 μg/L, conjunctival pathology was observed, while corneal insult was noticed only following exposure to a concentration of 0.5 μg/L and above. Both tissues presented poorer outcomes when exposed to higher sarin concentrations. In contrast, eyes topically exposed to 1 μg sarin demonstrated no ocular insult a week following exposure. On the contrary, topical exposure to 1 μg VX resulted in a significant corneal insult. Anticholinergic treatments such as 0.1% atropine or 2% homatropine, given shortly following VX exposure, counteracted this insult. The results of this study show that not only do anti-cholinergic treatments counteract the miotic response, but also prevent the histopathological insult observed when given shortly following OP exposure.

Eyeing up the Future of the Pupillary Light Reflex in Neurodiagnostics

The pupillary light reflex (PLR) describes the constriction and subsequent dilation of the pupil in response to light as a result of the antagonistic actions of the iris sphincter and dilator muscles. Since these muscles are innervated by the parasympathetic and sympathetic nervous systems, respectively, different parameters of the PLR can be used as indicators for either sympathetic or parasympathetic modulation. Thus, the PLR provides an important metric of autonomic nervous system function that has been exploited for a wide range of clinical applications. Measurement of the PLR using dynamic pupillometry is now an established quantitative, non-invasive tool in assessment of traumatic head injuries. This review examines the more recent application of dynamic pupillometry as a diagnostic tool for a wide range of clinical conditions, varying from neurodegenerative disease to exposure to toxic chemicals, as well as its potential in the non-invasive diagnosis of infectious disease.