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Biomedical subjects

I J Constable

Publications and source records attributed to I J Constable.

At least 181 records · Page 10Linked to original sources
PubMed1980

Retinal degeneration in Greyhounds.

Retinal degeneration in 10 Greyhounds with clinical and ophthalmoscopic features is described, including results of electroretinography and fluorescein angiography for one affected dog. Clinical and histologic features differed from other kinds of retinal degeneration in dogs.

Animals↗
PubMed1980

Late complications of pterygium treatment.

Long-term complications of pterygium excision and beta irradiation in 63 eyes of 57 patients are described. The age of the patients at treatment ranged from 27 to 69 years (mean 48 +/- 11), and complications were assessed 3 to 20 years later (mean 12 +/- 3). The pterygia were excised, leaving bare sclera, and beta irradiation of total dose 750 to 5200 rads (mean 3475 +/- 916) was given, except in 7 patients who had repeated courses or overlapping fields of beta irradiation. Scleral ulceration was present in 51 eyes and sectorial lens opacities with normal visual acuity (VA) in 19 eyes. Radiation induced cataract occurred in 3 eyes, with reduced vision. Ptosis, symblepharon, and iris atrophy were also seen. Pseudomonas endophthalmitis occurred in 4 patients with scleral ulceration. Beta irradiation to prevent recurrence of pterygia is a significant cause of iatrogenic ocular disease. There is a need to modify the beta irradiation dosimetry at present in use.

Adult↗
PubMed1980

Pseudomonas endophthalmitis associated with scleral necrosis.

Three cases of pseudomonas endophthalmitis associated with scleral necrosis 3 to 10 years after pterygium excision and beta irradiation are described. The value of prophylactic repair of radiation-induced scleral necrosis and early aggressive management of pseudomonas endophthalmitis are emphasized.

Aged↗
PubMed1980

Medical correlates and diabetic retinopathy screening.

A systematic ophthalmological, medical, and biochemical screening of a rural population of diabetics in Western Australia is being carried out. A team of ophthalmologists, physicians, and paramedical personnel establish regional screening centres on a voluntary basis at weekends. Every attempt is made to locate and examine all known diabetics. All patients are given a thorough ophthalmic examination including standard multiple field colour fundus photography. Thorough physical examination includes assessment of cardiovascular and neurological status. Biochemical parameters include random blood sugar, urine analysis, serum creatinine, glycosylated haemoglobin, cholesterol, and high density lipoprotein. A detailed questionnaire and interview is carried out to assess the historical degree of control and the patient's knowledge of the control and management of diabetes. The sample now comprises an unselected population of 400 diabetics living in rural areas and allows comparison of areas which have scarce medical services with centres that are well supplied with medical practitioners. Incidence of retinopathy varies from 25 to 36 per cent of the diabetic population. Positive correlations of retinopathy have been found with duration, age, hypertension, level of control assessed biochemically at the time of examination, presence of ischaemic heart disease, peripheral neuropathy, and renal disease. Smoking also correlates positively. The data provide a baseline by which attempts to alter diabetic knowledge, management, and control may be measured in follow-up studies.

Adolescent↗
PubMed1980

Chorioretinal biopsy in dogs.

A simplified practical technique for biopsy of retina and choroid has been developed in dogs. A 270 degree circular scleral flap of 3 mm diameter is raised. The risks of chorioretinal bleeding and vitreous loss are greatly reduced by intravenous mannitol and controlled hyperventilation, with hyperoxygenation and transient, systemic hypotension under general anesthesia. Rreasonable ultrastructural detail was preserved in chorioretinal specimens of 1 mm diameter. Repeat biopsies in the same eye are feasible without significant complications.

Animals↗
PubMed1979

Long-term observations of proton-irradiated monkey eyes.

Fifteen owl monkeys (30 eyes) that received proton irradiation of discrete areas of the retina and choroid have been observed for 3 1/2 years or more after irradiation. The dose delivered to the retina varied from a single dose of 1,600 to 4,750 proton rads and from 10,250 to 18,250 rads delivered in five fractions over a period of one month. Fundus examination, fluorescein angiography, and light and electron microscopy revealed chorioretinal changes at the area of irradiation. The part of the retina adjacent to the chorioretinal scar showed preservation of normal retinal vascular architecture on trypsin digest studies of the retina and on electron microscopic examination, even 1 mm from the edge of the scar. The results of this study suggest that proton beam irradiation may markedly reduce delayed ocular complications, especially radiation retinopathy, which is common to other forms of radiotherapy in the treatment of intraocular tumors.

Animals↗
PubMed1979

Passive radiotelemetry of intraocular pressure in vivo: calibration and validation of continual scleral guard-ring applanation transensors in the dog and rabbit.

Continual monitoring of intraocular pressure (IOP) by passive radiotelemetry, with a miniature scleral applanating device, mounted in a haptic contact lens (applanating transensor) is reported in the rabbit and dog. Several prototype transensors were calibrated in vivo in the rabbit and dog; a consistent linear output was obtained for each eye, although reproducibility of the slope between eyes over a period of time was less than ideal. Accuracy of determination of IOP was found to be better for the rabbit and will have to be improved before the instrument can be applied to the human. Multiple regression analysis of calibration studies in six rabbits established that the transensor output was not significantly affected by the small changes in body temperature and atmospheric pressure encountered during the study. Continual scleral tonometry with a standard Mackay-Marg tonometer showed that ocular rigidity has a significant effect on calibration curves, in contradistinction to standard Mackay-Marg corneal tonometry. A time-dependent decay in tonometer readings was more evident in canine eyes with low ocular rigidity. Since the transensor is also a guard-ring applanating device, calibration may be necessary for individual eyes and species.

Animals↗
PubMed1978

Proton irradiation of choroidal melanomas. Preliminary results.

Choroidal malignant melanomas in nine patients were treated with proton beam irradiation at the Harvard Cyclotron Laboratory, Cambridge, Mass. Each patient received five proton beam treatments in eight to ten days, totalling 4,730 to 8,570 rads at the tumor. No complications occurred during the treatment or follow-up period, which, at the time of this writing, ranges from one to 24 months, with an average of 12 months. No further growth of the tumor has been observed in any patient. Different signs of tumor regression have been noted. Resolution of the serous retinal detachments that accompanied some tumors is the earliest finding. Pigment changes over the surface of the tumor and adjacent pigment epithelium is a usual initial tumor response. Fluorescein angiography initially showed decreased leakage of dye; later, destruction of the tumor's vasculature and elimination of fluorescein leakage became evident. Only large choroidal vessels remained patient. Ultrasonography revealed decreased height of the tumors postirradiation, and the radioactive phosphorus (32P) uptake test, repeated in one patient, turned negative on postirradiation measurements.

Aged↗
PubMed1977

Proton irradiation of small choroidal malignant melanomas.

Five patients with choroidal malignant melanomas were treated with proton irradiation with a cyclotron. We developed an accurate method of aiming the proton beam within the eye. Four to five tantalum rings, 2 mm in diameter, were sutured to the sclera at the edges of the tumor, which is localized by indirect ophthalmoscopy and transillumination. The rings were used as markers for stereotactic radiography to align precisely the tumors with the proton beam. The patients were given a total tumor dose of 4,730 to 6,670 rads, delivered in five equal fractions, over a period of eight to nine days. All patients tolerated the treatments well without any adverse effects. The tumor response to therapy could not be evaluated at the completion of treatment since there was no immediate observable reaction of the tumor or of the surrounding retina. Although there has been no definite regression in any patient, we observed a change in the "color" of the tumor in the first two patients and resolution of two serous retinal detachments.

Choroid Neoplasms↗
PubMed1977

Infective keratitis in soft contact lens wearers.

Eight cases of infective keratitis are reported in wearers of soft contact lenses. Four of them had normal eyes and were wearing lenses on a continual basis. One was wearing a lens continually for therapeutic reasons. Three others were wearing lenses daily or intermittently. The four latter cases were using contaminated lens solutions. Two of the continual lens wearers lost vision to the point of blindness. A significant factor in their bad outcome was the fact that both lived in areas remote from adequate ophthalmic services. Serratia liquefaciens was implicated in one case. This is thought to be the only reported case of corneal abscess due to this organism in the past 16 years. S. marcescens was grown in another case from the lens solutions and carrying case.

Adult↗
PubMed1975

Vitreous substitution with gases.

The effects of vitreous substitution with air, a sulfur hexafluoride-air mixture, an octafluorocyclobutane-air mixture, and physiological saline were compared in owl monkeys. Each gas caused an increase in ocular vascular permeability greater than that caused by saline, as measured by vitreous inflow of serum protein labeled with iodine I 131 and discgel electrophoresis. The duration of increased vascular permeability closely paralleled the time each gas remained in the vitreous cavity.

Adsorption↗