Curettage for Copious Conjunctival Concretions

Management of multiple exposed eyelid concretions can be performed successfully in an anesthetized eyelid with gentle curettage of the concretions using a small chalazion curette. It has the advantage of managing the patient supine, providing better eyelid stability and visibility, and minimizing risk in the event of patient movement. This curettage technique was used to facilitate the successful resolution of a patient's ocular surface irritative symptomatology due to multiple exposed concretions

Light-induced Amaurosis: A Rare Manifestation of Internal Carotid Artery Stenosis

Light-induced amaurosis (LIA) is a rare presentation of internal carotid artery (ICA) stenosis. This report documents a 74-year-old Caucasian male who presented with profound right monocular vision loss, occurring on every occasion upon entering brightly lit environments. This was managed successfully with a right carotid endarterectomy. This case is presented to highlight the recognition and understanding of LIA and its importance for preservation of vision and prevention of ICA-related stroke

Visual cortex and extraocular retinal stimulation with surface electrode arrays

200

Surface stimulation of the brain with a prototype array for a visual cortex prosthesis

We are developing a neural prosthesis to electrically stimulate the visual cortex to restore basic visual perceptions to blind patients. The effects on cortical excitation of different stimulus configurations using a prototype electrode array are presented. Cats underwent a bilateral craniotomy to expose the cortex. An array for brain stimulation was placed on the surface of the right hemisphere. Cortical stimulation was undertaken in a variety of configurations while measuring the evoked responses that propagated through transcallosal pathways, at a homologous region on the contralateral hemisphere. Cortical excitation elicited by stimulation with a particular paradigm could be assessed by measuring the spatial spread and amplitudes of evoked responses in the contralateral hemisphere. Results from this transcallosal model have allowed us to examine the spatial and amplitude effects of cortical stimulation with our prototype electrode array and will aid in developing a neuroprosthesis for blind patients

Development of an extraocular retinal prosthesis : evaluation of stimulation parameters in the cat

Electrical stimulation of the retina with extraocular electrodes is a new approach to developing a retinal prosthesis for blind patients. We have evaluated stimulus and electrode configurations for an extraocular retinal prosthesis (ERP). In anesthetized cats, ERP disc electrodes of 1 mm, 2 mm and 3 mm diameter were sutured to the sclera over the lateral globe. Electrically evoked potentials (EEPs) were recorded over the ipsilateral visual cortex, which resulted from the retinal stimulation of the ERP electrodes with a return electrode placed at the medial canthus. Square pulses, triangular pulses and the effects of dark adaptation and electrode size on the amplitude and thresholds for a cortical response were investigated. Square pulses were more effective than triangular pulses for stimulating the retina. Dark adaptation leads to a large increase in the threshold for retinal stimulation. There was no difference in the threshold for stimulation between electrodes of 1 mm and 3 mm diameter. Stimulation of the retina with extraocular electrodes elicits an EEP that is similar to that generated by retinal stimulation with intraocular electrodes. The use of square pulses is preferred to triangular pulses to minimize the peak current density at the electrode-tissue interface. As there is little difference in the threshold current for retinal stimulation with 1 mm or 3 mm electrodes, 3 mm electrodes are preferred as this will decrease the charge density at the active surface of the electrode

D (2007) The role of substance P in the pathogenesis of pterygia. Invest Ophthalmol Vis Sci 48

PURPOSE. Pterygium is a prevalent ocular surface disorder thought to be triggered by chronic ultraviolet damage to the limbus. One of the enigmatic features of pterygium is its winglike shape, and the mechanism(s) supporting its centripetal growth remain to be elucidated. Because the growth pattern of pterygia mirrors the radial arrangement of corneal nerves, the authors propose that neuropeptides may facilitate its directional growth. This hypothesis prompted an investigation of the role of the sensory neuropeptide substance P (SP) and its receptor (NK 1 receptor) in directing cell migration in pterygia that may explain the characteristic growth pattern. METHODS. Immunohistochemical analysis for SP and the NK 1 receptor was performed on five pterygium specimens with corresponding autologous conjunctiva and limbus. Migration of pterygium epithelium, fibroblasts, and vascular endothelial cells toward SP was assessed by using a modified Boyden chamber. RESULTS. SP and NK 1 receptors were localized to infiltrating fibroblasts, mononuclear cells and the epithelia of pterygium, conjunctiva, and limbus, with elevated NK 1 receptor staining observed in pterygia. SP at nanomolar concentrations induced cell migration in pterygium fibroblasts and vascular endothelium in a dose-dependent fashion, which was inhibited by an NK 1 receptor antagonist. Pterygium epithelial cells were not migratory in these experiments. CONCLUSIONS. For the first time, this study showed the presence of NK 1 receptor in pterygia and that SP is a potent chemoattractant for pterygium fibroblasts and vascular endothelial cells, implying that SP may contribute to the shape of pterygia through its profibrogenic and angiogenic action. (Invest Ophthalmol Vis Sci. 2007;48:4482-4489

Toxicology of the retina : advances in understanding the defence mechanisms and pathogenesis of drug- and light-induced retinopathy

The neurosensory retina is a highly specialized sense organ that is subjected to constant exposure of systemic toxins, oxidative stress and focused light rays. Important advances have been made in recent decades in unravelling a myriad of defence mechanisms against such insults and consequently in improving the understanding of the principles underlying various drug- and light-induced disease processes. To defend against circulating toxins, the retina possesses a specialized blood-retinal barrier (BRB) that tightly regulates the transport of substances across the functional boundaries of the retina at the retinal capillaries and the retinal pigmented epithelium. An endogenous cytochrome p450 system is strategically located within the retina to neutralize agents that can diffuse through the BRB. The biooxidation effect of light is prevented by a wide array of unique antioxidant mechanisms in the retina. Nonetheless, pathological processes may evolve when these different lines of defence are overwhelmed by various xenobiotics, environmental agents such as cigarette smoke and excessive light exposure, particularly of short wavelength high frequency blue light and ultraviolet light. Latest research using transgenic models has revealed novel apoptotic pathways implicated in acute phototoxicity, in particular blue light damage, and provides important clues for further understanding the risks of high-frequency light exposure to human retinopathy. This review article summarizes the basic scientific principles of these different defence mechanisms and discuss the implications in pathophysiology and treatment