Efficacy of supra-choroidal, bipolar, electrical stimulation in a vision prosthesis.

The key to successful, clinical application of therapeutic neurostimulators lies primarily with the safety and efficacy of their electrode-tissue interfaces. The authors posit that for electrical stimulation of the visual system, supra-choroidal electrode placement provides a safe, stable and readily-accessible site for implantation and the provision of electrical stimulation. The present paper explores the efficacy of supra-choroidal electrical stimulation of retinal neurons. Based upon recordings made with surface electrodes placed on the primary visual cortex, areas of activation in the cortex were shown to change when different areas on the supra-choroidal space were stimulated. Finally, the threshold to elicit a response from neurons in the visual cortex, was found to be 77.55 +/- 29.85 nC.

Use of silicone oil in the treatment of complicated retinal detachment: results from 1981 to 1994.

PURPOSE: To evaluate the advantages and disadvantages of the retention and removal of silicone oil in the treatment of complicated retinal detachments. METHODS: The records of 344 patients (348 eyes) that underwent vitrectomy and silicone oil injection for complicated retinal detachments were abstracted and analysed. The anatomical and functional results, complications and influencing factors are discussed. The outcome in eyes after removal of the silicone oil was compared with the outcome in a comparable group of eyes in which the silicone oil was retained. RESULTS: The overall retinal reattachment rate was 63% (220/348). The final vision of 5/300 or better was 52% (115/220) in those eyes with totally attached retinas. The silicone oil-related complications included keratopathy (23%) and secondary glaucoma (11%). Comparing removal of silicone oil with retention of silicone oil, we found: (i) there was no statistical difference in the redetachment rate (19 vs 17%); (ii) oil-removed eyes had a better final vision (P < 0.05); and (ii) keratopathy (13 vs 23%), secondary glaucoma (11 vs 25%) and optic nerve atrophy (4 vs 18%) were significantly lower in oil-removed eyes. CONCLUSION: Silicone oil injection is useful in the treatment of complicated retinal detachments. For reducing the incidence of complications, early removal of silicone oil is recommended in those cases in which the retina is attached, all breaks adequately closed and traction relieved.

AIDS and the eye. A 10-year experience.

BACKGROUND: The AIDS database at Fairfield Hospital, Melbourne, maintains information on eye pathology as identified by the three visiting ophthalmologists. Patients underwent an eye consultation: if they had ocular symptoms; if signs were seen on direct ophthalmoscopy by physicians; or when their CD4+ve cell count fell below 50/microL. The first AIDS-associated eye signs were identified in mid-1984. In the subsequent decade, 3257 patients in Victoria tested positive for HIV, and 845 of the 1123 who developed AIDS were treated at Fairfield Hospital. METHODS: We undertook a retrospective review of the Fairfield Hospital database to identify the AIDS-associated ocular problems seen. RESULTS: Some 723 patients had an eye consultation. In the earliest stage of HIV infection, minor non-specific ophthalmic involvement may occur. As the disease progresses, microvasculopathy (cottonwool spots and haemorrhages) appears. External disease also occurs such as molluscum contagiosum and Kaposi's sarcoma of the conjunctiva. With more suppression of the immune system, opportunistic infections become common, and have a considerable visual morbidity. Cerebral toxoplasmosis (117 patients) is only rarely associated with ocular involvement (three patients), but cytomegalovirus (CMV) commonly causes retinitis [204 patients (24%)]. It has been the AIDS-defining illness in 26 patients. A majority had the disease confined to one eye. Mean CD4 cell count at onset is 15 +/- 5 microL and it has been associated with a viraemia in all but two patients. Late complications of CMV retinitis include relapse in 41 (20%), spread to the other eye in 24 (12%), and retinal detachment in 30 (15%). Visual impairment follows from retinal destruction, optic nerve involvement, and retinal detachment. CONCLUSION: The ophthalmic workload from late ocular complications of AIDS is increasing. Newer and more effective methods of treatment are being developed. Ophthalmologists are becoming more aware of the need for universal precautions to avoid risks from this and other blood-borne infections.

Microholes of the fovea centralis.

Foveal microholes are a possible cause of unilateral or bilateral small central visual defects in the absence of other macular pathology. In 18 eyes of 17 patients we noted the following features: small, dark-reddish holes in the centre of the fovea ranging from 50 to 150 micron in size; normal adjacent retinal pigment epithelium and neuroepithelium; unilateral in most cases; males and females are equally affected; mean age 40 years; insidious onset; no history of direct eye trauma or sungazing; non-progressive; relatively favourable visual outcome; no relationship with regular macular holes; aetiology unknown. These distinctive features justify reporting these patients as an important separate group.

Preventing a high rise in intraocular pressure after laser trabeculoplasty.

The high rise in pressure which sometimes follows laser trabeculoplasty is a serious and sight-threatening complication in patients with advanced glaucoma. In a previous study we found that patients undergoing laser trabeculoplasty were very unlikely to have a high rise in pressure if the initial pressure was less than 20 mmHg. In the present study a series of patients was given acetazolamide 500 mg immediately before laser trabeculoplasty if their pressures were greater than 20 mmHg. All patients were then monitored to see if this regime was effective in preventing a serious rise in intraocular pressure. Some of the patients with an initial pressure less than 20 mmHg still sustained a high rise in pressure after laser trabeculoplasty. A further series of patients was then given acetazolamide preoperatively and the postoperative rise in pressure was monitored two and 24 hours after trabeculoplasty. The acetazolamide prevented a high rise in pressure after laser trabeculoplasty in the majority of patients.