Biomedical subjects

R A Whitelocke

Publications and source records attributed to R A Whitelocke.

14 recordsLinked to original sources

PubMed1993

Radiation dose to the lens and cataract formation.

PURPOSE: To determine the radiation tolerance of the lens of the eye and the incidence of radiation-induced lens changes in patients treated by fractionated supervoltage radiation therapy for orbital tumors. METHODS: Forty patients treated for orbital lymphoma and pseudotumour with tumour doses of 20-40 Gy were studied. The lens was partly shielded using lead cylinders in most cases. The dose to the germinative zone of the lens was estimated by measurements in a tissue equivalent phantom using both film densitometry and thermoluminescent dosimetry. Ophthalmological examination was performed at 6 monthly intervals after treatment. RESULTS: The lead shield was found to reduce the dose to the germinative zone of the lens to between 36-50% of the tumor dose for Cobalt beam therapy, and to between 11-18% for 5 MeV x-rays. Consequently, the len doses were in the range 4.5-30 Gy in 10-20 fractions. Lens opacities first appeared from between 3 and 9 years after irradiation. Impairment of visual acuity ensued in 74% of the patients who developed lens opacities. The incidence of lens changes was strongly dose-related. None was seen after doses of 5 Gy or lower, whereas doses of 16.5 Gy or higher were all followed by lens opacities which impaired visual acuity. The largest number of patients received a maximum lens dose of 15 Gy; in this group the actuarial incidence of lens opacities at 8 years was 57% with visual impairment in 38%. CONCLUSION: The adult lens can tolerate a total dose of 5 Gy during a fractionated course of supervoltage radiation therapy without showing any changes. Doses of 16.5 Gy or higher will almost invariably lead to visual impairment. The dose which causes a 50% probability of visual impairment is approximately 15 Gy.

Adult↗

PubMed1990

Solitary choroidal metastasis in bronchial carcinoma.

Choroidal metastases, although uncommon, are a well-recognized complication of malignant disease and their development is usually associated with other soft tissue metastases and a poor prognosis. About one-third of choroidal metastases arise from carcinoma of the bronchus. They are rarely solitary. Histologically confirmed solitary choroidal metastasis from squamous carcinoma of the bronchus has not been previously reported in the literature. We describe such a case.

Aged↗

PubMed1989

Cataracts and cigarette smoking. The City Eye Study.

The City Eye Study is a nine year longitudinal prospective epidemiological study. During the first three year phase the study recruited 1029 volunteers, aged between 54 and 65 years, primarily from companies and organisations working in or around the City of London. The analysis of the first cohort data shows a significant association between nuclear lens opacities and moderate to heavy cigarette smoking. The Relative Risk for nuclear lens opacity and cigarette smoking ranges from 1.0 for past light-smokers through 2.6 for past heavy-smokers, to 2.9 for present heavy smokers.

Aged↗

PubMed1988

Orbital and conjunctival lymphoma treatment and prognosis.

115 patients with lymphoid tumours presenting in the orbit were seen between 1970 and 1984. The histological types were high-grade malignant lymphoma--18, low-grade malignant lymphoma--43, and indeterminate lymphocytic lesions--54. Eighteen patients were found to have disseminated lymphoma at presentation. The majority of the patients received radiotherapy to the orbit; local control was achieved in all cases and the ocular morbidity from radiotherapy was low with 11 patients developing lens opacities and 5 a dry eye. Survival of patients with stage I low-grade lymphoma and indeterminate lymphocytic lesions was similar to that of a normal population of the same age distribution. The clinic features and dissemination pattern of the low-grade malignant lymphomata and the indeterminate lymphocytic lesions were identical, suggesting that most, if not all, lymphoid masses presenting in the orbit are neoplastic rather than reactive in nature.

Adult↗

PubMed1987

Ocular morbidity after radiotherapy of orbital and conjunctival lymphoma.

One hundred and fifteen patients were treated for lymphoma of the conjunctiva and orbit between 1970 and 1984. One hundred and twelve patients received radiotherapy to the orbit, of whom 73 (65 per cent) had at least one year of follow-up by an ophthalmic surgeon. Patients with low-grade lymphomas (97) mostly received 30 Gy in 15 fractions to the orbit over a period of 3 weeks. Those with high-grade lymphomas (18) mostly received 40 Gy in 20 fractions over 4 weeks. Most were treated using anterior and lateral radiation fields to the orbit with shielding of the cornea and lens. This technique delivered a mean lens dose of 15 Gy. The early and late ocular and orbital morbidity in these patients was low. Eight radiation-induced cataracts developed of which only six interfered with vision. None has needed cataract surgery. No patients developed radiation retinopathy and only 5 had disorders of ocular lubrication.

Adolescent↗

PubMed1985

Recurrent visual loss in homozygous sickle cell disease.

In sickle cell retinopathy vascular involvement is most frequently recognised at the retinal periphery, but obstruction of perimacular arterioles and of major retinal vessels may also occur. This report describes a patient with homozygous sickle cell (SS) disease with recurrent occlusion of major retinal vessels associated with recurring transient impairment of visual function.

Adult↗

PubMed1982

Diabetic retinopathy and its relation to type of diabetes: review of a retinal clinic population.

A detailed survey was performed of 100 consecutive diabetic patients with severe retinopathy referred to a retinal clinic. They were classified as having either type 1 (insulin-dependent) or type 2 (noninsulin-dependent) diabetes. There were significant associations between an initial diagnosis of maculopathy. There was a significant association between male sex and proliferative retinopathy. Referral patterns to this clinic and the medical supervision of the patients are discussed.

Adult↗

PubMed1981