Search PubMed⌕ Search

Biomedical subjects

G N Dutton

Publications and source records attributed to G N Dutton.

At least 109 records · Page 6Linked to original sources

Penetration of topically applied prednisolone sodium phosphate into human aqueous humour.

Gas Chromatography with Mass Spectrometry (GCMS) was utilised to determine the penetration of prednisolone sodium phosphate into the aqueous humour of human volunteers undergoing routine cataract extraction. Detectable levels of prednisolone were measured in the aqueous humour within 15 minutes. Peak concentrations occurred between 90 and 240 minutes, and the steroid could not be detected in samples taken 10 hours or more after topical administration.

Administration, Topical↗

Central visual function in patients with resolved central serous retinopathy. A long term follow-up study.

The visual acuity, central retinal sensitivity, macular thresholds, contrast sensitivity and temporal visual acuity were employed to assess the long term visual outcome in 23 patients with a history of central serous retinopathy (CSR). Twenty patients had unilateral CSR, and 3 had had bilateral disease. The unaffected eyes had significantly better visual acuities (P less than 0.014), better retinal sensitivities (P less than 0.006) and lower macular thresholds (P less than 0.008) when compared with affected eyes. The eyes with CSR whose visual acuities were mildly affected (6/9) showed lower sensitivity for the high spatial frequency (P less than 0.0072). There was no significant difference in the temporal visual acuity between eyes with CSR and the non-affected eyes.

Follow-Up Studies↗

The Pulfrich phenomenon and its alleviation with a neutral density filter.

A case is described in which a presumed vascular accident resulted in long-standing visual difficulties in both reading and the analysis of vectors of moving objects. Clinical examination revealed minimal right optic atrophy with a relative superior altitudinal visual field defect associated with a positive Pulfrich effect. A partial head turn to the right in association with paresis of saccades and pursuit eye movements to the right was also evident. Spectacles for distance which incorporated a neutral density filter before the left eye were prescribed. These practically eliminated the Pulfrich effect and alleviated the problems of vector analysis. A near correction was provided which incorporated prisms with bases to the right. This eliminated the reading difficulties. The visual problems experienced by patients suffering from a positive Pulfrich effect are described and discussed.

Eyeglasses↗

Pulsed neodymium-YAG laser trabeculotomy: energy requirements and replicability.

Short pulsed laser trabeculotomy has been shown to reduce intraocular pressure in patients with primary open angle glaucoma. This study seeks to determine the energy levels required to produce a fistula into the canal of Schlemm for four different Q-switched neodymium-YAG lasers. The laser was fired at fixed human trabecular meshwork specimens at a range of energy settings for each laser and the characteristics and replicability of the lesions produced were analysed. Energy levels between 3 and 5 mJ were sufficient to produce fistulae into the canal of Schlemm with an approximately 50% success rate for each instrument.

Humans↗

Toxoplasmic retinochoroiditis--a historical review and current concepts.

Toxoplasmic retinochoroiditis usually presents during the first three decades of life as a consequence of intra-uterine infection by Toxoplasma gondii. The ingestion of infected undercooked meat, or foodstuffs contaminated by infected cat faeces, constitute the primary sources of infection for the non-immune mother. It is thought that following congenital infection, Toxoplasma cysts remain dormant in otherwise normal retina and that acute retinochoroiditis is the result of reactivation of the parasite, perhaps by cyst rupture. Treatment is indicated for sight threatening disease and comprises anti-Toxoplasma agents. The addition of steroids may be required to diminish the inflammatory response. Photocoagulation of normal retina around focal lesions probably decreases the incidence of recurrent inflammation. Women should be advised not to eat undercooked meat and to avoid contact with cat excrement during pregnancy. These measures will decrease the incidence of both eye disease and the more severe manifestations of congenital toxoplasmosis, which include congenital abnormalities, mental retardation, hydrocephalus and blindness.

Clindamycin↗

Penetration of topically applied dexamethasone alcohol into human aqueous humor.

Gas chromatography combined with mass spectrometry was used to determine the absorption of topically applied dexamethasone alcohol into the aqueous humor of human subjects undergoing routine intraocular surgery. The dexamethasone concentration in aqueous humor was greatest in the interval between 91 and 120 minutes following instillation (mean concentration, 31 ng/mL). Dexamethasone was still detectable in the aqueous 12 hours after instillation.

Administration, Topical↗

Photocoagulation of raised new vessels by long-duration low-energy argon laser photocoagulation--a preliminary study.

Direct laser treatment of retinal neovascularisation is indicated when regression has not been brought about by retinal photocoagulation. Current treatment regimens involve multiple laser applications to the neovascular complex. Long-duration low-energy burns have the advantage of slowly heating the tissue without engendering disruption. We report the use of this treatment as a means of occluding the feeder vessels to a neovascular network. The application of argon blue-green laser treatment at 0.1 watt for 60 seconds at two adjacent points on a feeder vessel was found to give rise to permanent vascular occlusion without causing complications.

Adult↗

Short-pulsed neodymium-YAG laser trabeculotomy. An in vivo morphological study in the human eye.

The in vivo response to short-pulsed Nd-YAG laser damage to the trabecular meshwork has not been studied in the human eye. The nature of the response will determine the potential efficacy of this treatment for glaucoma. We have investigated short-pulsed laser trabeculotomy lesions created in the trabecular meshwork of four human eyes within 18 hr prior to enucleation for intraocular melanoma. Scanning electron micrographs showed irregular craters (150-300 micron diameter) in the trabecular meshwork surrounded by trabecular beams which were splayed towards the anterior chamber. The adjacent damage to trabecular and corneal tissues was characterized by denudation of endothelial cells and deposition of debris. Light and transmission electron micrographs of the edge of the trabeculotomy lesions revealed fragmentation of the endothelial cells and splitting of the trabecular beams. Preservation of normal morphology was noted in the deeper tissues within 50 micron of the edge of the crater. Neutrophils were present within 20 min of laser treatment whilst macrophages characterised the inflammatory response at later stages. Perforation of the canal of Schlemm was only obtained with lesions in the middle of the trabecular meshwork but not with lesions placed more anteriorly.

Humans↗

Conjunctival incisions for trabeculectomy and their relationship to the type of bleb formation--a preliminary study.

The bleb which develops following trabeculectomy may be diffuse or cystic in nature. Cystic blebs can be complicated by infection, leakage of aqueous, astigmatism, and problems related to contact lens wear, whereas diffuse blebs are not associated with such problems. We report a preliminary prospective photographic evaluation of bleb formation following each of three types of conjunctival incision: (a) fornix based (b) straight limbus based and (c) curved limbus based. The vascular pattern and morphology of the drainage bleb formed was dependent upon the type of conjunctival incision made. The fornix based flap was found most likely to give rise to a diffuse bleb with a normal vascular pattern.

Adult↗

Aiming criteria for neodymium-YAG laser trabeculotomy. A clinico-pathological study.

Recently reported clinical and experimental studies have shown that pulsed neodymium-YAG laser trabeculotomy may reduce intraocular pressure but not in all cases. We report a clinico-pathological study designed to delineate the aiming criteria required to produce a fistula between the anterior chamber and the canal of Schlemm. In summary, the aiming beam must be centred on the reflecting surface of the gonioscopic contact lens, and aimed at the posterior trabecular meshwork. This study also indicates that the energy levels required to produce a discrete trabeculotomy in vivo are similar to those determined by in vitro studies.

Glaucoma, Open-Angle↗

Congenital neuro-ophthalmic toxoplasmosis in the mouse.

Clinical examination of the eyes of mice with congenital toxoplasmosis provided a good indication of the extent of underlying histopathological damage in the eye, but was of little value for predicting neuropathological severity. Furthermore, the dye-test titre was not related either to the degree of ocular damage or to the severity of brain damage.

Animals↗

Parameters for neodymium-YAG laser trabeculotomy: an in-vitro study.

A Biophysic Médical Nanolas Q-Switched pulsed neodymium-YAG laser has been used to produce lesions in human trabecular meshwork in vitro. Sectors of corneoscleral tissue containing trabecular meshwork were suspended in a waterbath which had had a Trokel gonioscopic contact lens mounted into one side by means of a watertight seal. The laser was used to produce lesions in the trabecular meshwork on either side of each specimen. The energy levels delivered ranged from 0.5 to 7.0 mJ, and convergence angles of 10 degrees and 18 degrees were employed. The energy levels required to produce discrete lesions into the canal of Schlemm without perforating the underlying sclera were 3.0-5.0 mJ at the 10 degrees convergence angle and 4.0-6.0 mJ at the 18 degrees convergence angle setting. It is recommended that such data be determined for each type of laser prior to attempting short-pulsed laser internal trabeculotomy in patients with glaucoma.

Humans↗

The immunocytochemical demonstration of Toxoplasma antigen in the brains of congenitally infected mice.

The peroxidase anti-peroxidase immunocytochemical staining method was used to identify Toxoplasma antigen in paraffin embedded sections of the brains of 22 mice congenitally infected with the parasite. Intact Toxoplasma tissue cysts were readily demonstrated in the brain in all cases. In 4 of the 22 infected mice there was evidence of rupture of the cyst wall and/or presence of extra-cystic Toxoplasma antigen. Further support for the extra-cystic location of Toxoplasma antigen was obtained by electron microscopy of reprocessed tissue which revealed endozoites in the area immediately surrounding a ruptured cyst. The possible implications of these findings in relation to the pathogenesis of congenital toxoplasmic meningo-encephalitis are discussed.

Animals↗