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Biomedical subjects

C V Clark

Publications and source records attributed to C V Clark.

At least 37 records · Page 2Linked to original sources
PubMed1988

Retinal circulation responses to systemic autonomic nerve stimulation.

The retinal vessel calibre responses to controlled stimulation of the autonomic nervous system were studied in 10 healthy subjects, using sustained isometric muscle contraction as stimulus. Each subject was studied twice using different mydriatic agents, (1) g.tropicamide 1% a parasympatholytic agent and (2) g. phenylephrine 10% a sympathetic agonist. In the tropicamide study, there was a mean arteriolar constriction of 8.1% (SEM 1.67, p less than 0.001) and venule constriction of 3.7% (SEM 0.85, p less than 0.001) with a mean rise in diastolic blood pressure of 27.4 mmHg (SEM 2.95, range: 13-45 mmHg). When g. phenylephrine 10% was used, there was a mean arteriolar constriction of 8.6% (SEM 1.68, p less than 0.001) and venule constriction of 4.8% (SEM 1.22, p less than 0.001) with a mean rise in diastolic blood pressure of 29.2 mmHg (SEM 2.56, range: 17-44 mmHg). There was no significant difference in retinal vessel calibre in the recovery phase compared to baseline phase (p greater than 0.05) or between the two mydriatic agents on vessel responses (p greater than 0.05). There was no correlation between the rise in diastolic blood pressure and the degree of retinal vessel constriction, during handgrip contraction in either study. This study has demonstrated a significant association between retinal vessel calibre and systemic autonomic nerve stimulation. The possible mechanisms for the retinal vessel constriction observed in this study are discussed.

Adult↗
PubMed1987

Autonomic neuropathy in proliferative diabetic retinopathy.

Autonomic nerve function was assessed in 28 diabetic patients with proliferative retinopathy and 61 age- and sex-matched control subjects, using a series of tests based upon cardiovascular reflex responses to standardised stimuli. Autonomic neuropathy was present in 75 per cent of diabetics with proliferative retinopathy, compared with 5.2 per cent of the control group. The implications of a significant association between cardiovascular autonomic neuropathy and proliferative diabetic retinopathy are discussed.

Adult↗
PubMed1987

Posterior synechiae after glaucoma operations: aggravation by shallow anterior chamber and pilocarpine.

Posterior pupillary synechiae affect a proportion of eyes subjected to iridectomy with or without drainage operation because (1) aqueous humour bypasses the pupil; (2) traumatic iridocyclitis occurs; (3) there is immobility of the iris in the iridectomy sector; (4) in eyes with angle closure glaucoma closer apposition of the iris to the anterior lens capsule increases the tendency; (5) pilocarpine aggravates (4) both in angle closure glaucoma and open angle glaucoma and produces a small immobile pupil facilitating pupillary membrane formation (occlusio pupillae). Pilocarpine should be avoided if possible as medical treatment at any time after a drainage operation. A beta blocker is the drug of choice. To eliminate posterior synechiae over a fair number of degrees of pupil (say 30 degrees) sector iridectomy can be done.

Aged↗
PubMed1987

Parasympathetic denervation hypersensitivity of the iris in ocular hypertension.

Seventy-eight ocular hypertensive patients and 47 age-and sex-matched control subjects were assessed for parasympathetic denervation hypersensitivity of the iris using topical application of 2.5% methacholine chloride solution. Constriction of the pupil in response to methacholine stimulation of the sphincter pupillae was significantly greater in the ocular hypertensive patients than the control group (P less than 0.001). The implications are discussed, with particular reference to the association between autonomic neuropathy and the primary glaucomas.

Administration, Topical↗
PubMed1986

The prevalence of diabetes mellitus in the family history of patients with primary glaucoma.

The prevalence of diabetes mellitus in the family history of 371 patients with primary glaucoma--closed-angle glaucoma, ocular hypertension and open-angle glaucoma--and 85 age- and sex-matched control subjects was determined. There was a significantly-increased prevalence of familial type 2 diabetes mellitus (non-insulin dependent diabetes mellitus) in patients with closed-angle glaucoma (p = 0.004) and ocular hypertension (p = 0.02). Primary glaucoma was not associated with familial type 1 diabetes mellitus (insulin dependent diabetes mellitus). The implications are discussed.

Aged↗
PubMed1986

Systemic autonomic neuropathy in open-angle glaucoma.

Systemic autonomic nerve function was assessed in 67 patients with open-angle glaucoma and 76 age- and sex-matched control subjects, using a series of well-established tests based upon cardiovascular reflex responses to standardised stimuli. Parasympathetic neuropathy was present in 37.3% of open-angle glaucoma patients compared with 2.6% of the control group. Demonstration of a significant association between autonomic neuropathy and primary glaucoma may provide a logical rationale for the efficacy of autonomic medication in glaucoma therapeutics; the prognostic implications are discussed.

Aged↗
PubMed1986

Anterior segment autonomic dysfunction in ocular hypertension.

Autonomic nerve function in the anterior segment of the eye was assessed by measurement of the pupil cycle time in 189 patients with ocular hypertension and 70 age- and sex-matched control subjects. Parasympathetic dysfunction was significantly present in ocular hypertensive patients with narrow irido-corneal angles, though not in wide-angle subjects. The results are discussed, with particular reference to the accumulating evidence implicating autonomic dysfunction as a significant factor in the pathogenesis of the primary glaucomas.

Adult↗
PubMed1986

Age-adjusted normal tolerance limits for cardiovascular autonomic function assessment in the elderly.

Autonomic nerve function was assessed in 85 normal subjects (mean age 66.1 +/- 10.2 years) by a series of standard tests based upon cardiovascular reflexes. Age-adjusted normal tolerance intervals were established for each test. The clinical application of autonomic function assessment in the elderly is discussed, with particular reference to patients with diabetes mellitus, ocular hypertension, and primary glaucoma, which represent a significant proportion of the aged population.

Adult↗
PubMed1986

Progression of impaired glucose tolerance to diabetes mellitus in patients with primary glaucoma and ocular hypertension.

In 375 patients aged 68.5 +/- 9.4 years (mean +/- 1 SD) with primary glaucoma subdivided by irido-corneal angle configuration into closed-angle glaucoma (123 cases), ocular hypertension (186 cases), and open-angle glaucoma (66 cases), diabetic status was determined by standard 75 g oral glucose tolerance tests. In 63 patients with impaired glucose tolerance who were retested one year later, 16% had progressed to diabetes mellitus. The results confirm a significant association between non-insulin dependent diabetes mellitus and primary glaucoma which may result from autonomic dysfunction in parasympathetic tone causing anterior chamber angle closure.

Aged↗
PubMed1986

Pupil cycle time in primary closed-angle glaucoma.

Pupil cycle time was measured in fellow eyes of 118 patients with closed-angle glaucoma and 70 age- and sex-matched control subjects. Results indicate that the duration of pupil cycle time was significantly prolonged in patients with closed-angle glaucoma as compared to the control group (p less than 0.001); in addition, the prevalence of absent pupillary oscillation was significantly increased in closed-angle glaucoma patients (p less than 0.001). The implications are discussed, with particular reference to the association between closed-angle glaucoma and systemic parasympathetic neuropathy.

Aged↗
PubMed1985

Autonomic neuropathy in ocular hypertension.

By means of a series of cardiovascular autonomic function tests, systemic parasympathetic neuropathy was demonstrated in 41.8% of 189 patients with ocular hypertension and in 2.6% of 76 controls. Parasympathetic neuropathy was significantly more common in patients with narrow-angle hypertension than in those with wide-angle hypertension. Raised intraocular pressure may be a manifestation of systemic disease rather than an exclusively ocular phenomenon.

Aged↗
PubMed1985

Prevalence of diabetes in glaucoma.

Oral glucose 75 g was given to 352 patients with chronic glaucoma, acute glaucoma, or ocular hypertension and 73 patients without glaucoma. The proportion of patients with shallow anterior chambers who showed an abnormal response was significantly greater than that in patients with deep anterior chambers and in the control group (p less than 0.005). The probability of developing an abnormal response to oral glucose tests increased as the depth of the anterior chamber decreased; these two variables showed a significant negative linear correlation (r = -0.79, p less than 0.001). The high prevalence of autonomic dysfunction in patients with shallow anterior chambers and glaucoma may explain this association. Because of this, acute glaucoma should be regarded as a symptom of diabetes.

Aged↗
PubMed1985

Diurnal variation in the dimensions of the anterior chamber.

Anterior chamber depth and volume were measured photogrammetrically on a diurnal basis in 38 eyes from 21 normal subjects. Significant diurnal variation in anterior chamber dimensions was demonstrated. Anterior chamber depth and volume measurements were significantly lower in the evening than in the morning, with particular emphasis on the periphery of the anterior chamber. Axial depth decreased by 2.1%; peripheral depth, by 21.1%; and anterior chamber volume, by 5.7%.

Aged↗