Postural studies in pulsatile ocular blood flow: I. Ocular hypertension and normotension.

Measurements of pulsatile ocular blood flow (POBF) have been recorded in a group of healthy, ocular normotensive volunteers and ocular hypertensive patients recruited from outpatients. Use of a pneumotonometric probe linked to a Langham ocular blood flow system enabled readings of intraocular pressure and its variation with heart rate (ocular pulse) to be taken in erect and supine positions. Pulsatile ocular blood flow was calculated from these values by means of the pressure-volume relationship previously described for living human eyes. Assumption of the supine posture was accompanied by a significant rise in intraocular pressure; in normal eyes (mean, with SEM) (3.1 (0.4) mmHg, p less than 0.0001) and to a greater extent in ocular hypertensive eyes (4.7 (0.6) mmHg, p less than 0.0001). The POBF did not differ significantly between normotensive and ocular hypertensive groups in either the erect or supine postures. In both groups, however, assumption of the supine posture was accompanied by a significant fall in POBF (normals: -121 (21) microliters/min, p less than 0.0001; ocular hypertensives: -75 (16) microliters/min, p less than 0.0002). These reductions in POBF represent decrements of 27.5 (3.0)% and 17.1 (3.8)% respectively. Pulsatile ocular blood flow is reduced in the supine posture, and this may result in tissue hypoxia in subjects at risk of developing glaucoma. A companion paper describes the measurement of POBF in a group of patients with chronic open angle glaucoma treated with topical timolol 0.25%.

Postural studies in pulsatile ocular blood flow: II. Chronic open angle glaucoma.

The pulsatile ocular blood flow (POBF) has been recorded in 15 patients with chronic open angle glaucoma. Measurements were performed during regular treatment with timolol 0.25% eyedrops, two weeks after withdrawal of this treatment, and then a further two weeks after its reinstitution. Readings were taken with subjects in both the erect and supine positions by means of a pneumotonometric probe to measure intraocular pressure (IOP), linked to a Langham ocular blood flow system. Assumption of the supine posture was associated with a significant increase in IOP in all phases of the study. Treatment with timolol lowered the mean IOP in comparison with the untreated phase (-4.4 (SEM 0.6) mmHg, p less than 0.001) but had no effect on the postural change. A significant reduction in POBF was recorded on assumption of the supine posture (-66 (SEM 18) microliters/min, p less than 0.001), representing a mean decrement of 19%. However, there were no significant differences in POBF between treated and untreated phases of the study. Comparison of the values obtained in patients with glaucoma (COAG) after withdrawal of treatment with those in subjects with ocular hypertension revealed that there was no significant difference in intraocular pressure between the two groups. However, both POBF (-68 (SEM 29) microliters/min) and the pulse amplitude of the intraocular pressure (ocular pulse: -0.45 (SEM) 0.14 mmHg) were significantly lower in the COAG patients. Pulsatile ocular blood flow is significantly lower in patients with chronic open angle glaucoma. Furthermore, the POBF and the postural response of these patients is not improved by the use of topical timolol therapy.

Ocular responses in healthy subjects to topical bunazosin 0.3%--an alpha 1-adrenoceptor antagonist.

The ocular effects of the alpha-adrenoceptor blocking drug bunazosin, administered as eyedrops, have been measured in a placebo-controlled double-blind single-dose study in 15 healthy volunteers. The drug significantly reduced intraocular pressure over 10 hours, and there was no associated change in pulsatile ocular blood flow. Characteristic effects of alpha-adrenoceptor blockade were observed--miosis, ptosis, and conjunctival hyperaemia. The miosis alone persisted for more than 24 hours in nine out of 15 subjects.

Occlusion of the central retinal artery and ocular neovascularisation: an indirect association?

Ocular neovascularisation is recognised as an uncommon complication of central retinal artery occlusion (CRAO) but has been associated most frequently in those patients suffering from carotid artery occlusive disease. We report the finding of neovascularisation after CRAO in a group of 8 patients, who have presented over the previous 6 years. Four showed no evidence of atherosclerotic carotid disease and only 2 were diabetic. Although the group numbers are necessarily small, it is suggested that these cases support the assertion that ocular neovascularisation may occur following CRAO in the absence of any underlying and predisposing ischaemic or inflammatory condition.

The maintenance of per-operative mydriasis in phacoemulsification with topical diclofenac sodium.

PURPOSE: To determine whether the use of topical diclofenac sodium (diclofenac) pre-operatively improves the maintenance of per-operative mydriasis, in conjunction with irrigating solutions containing adrenaline. METHODS: Sixty-four consecutive patients undergoing phacoemulsification were randomised to receive either diclofenac or no diclofenac in conjunction with cyclopentolate 1% and phenylephrine 10% pre-operatively. They subsequently underwent routine phacoemulsification by one consultant surgeon. Irrigating solutions of balanced salt solution contained adrenaline 1:10(6). Pupil diameters were measured pre-sclerostomy, post-phacoemulsification, post-irrigation/aspiration and on day 1 post-operatively. These were then compared by Student's t-test. RESULTS: The two groups were statistically similar in age and sex. The mean pre-sclerostomy pupillary diameters were 8.1 mm in both groups. The mean post-phacoemulsification diameters were 7.6 mm in those receiving diclofenac and 7.2 mm in those not (p = 0.03). The mean diameters after infusion/aspiration were 7.7 mm in those receiving diclofenac and 7.1 mm in those not (p = 0.008). The mean pupillary diameters on day 1 were 5.3 mm in those receiving diclofenac and 4.6 mm in those not (p = 0.003). CONCLUSION: Diclofenac improves the maintenance of per-operative mydriasis, in the presence of irrigating solutions containing adrenaline.

Otrivine-antistin-pupil, corneal and conjunctival responses to topical administration.

The ocular effects of Otrivine-Antistin eyedrops have been measured in a placebo controlled single-blind study in sixteen healthy volunteers. The drops produced mild sympathomimetic responses in the eye but had no effect on corneal sensitivity or on intraocular pressure. The evidence indicates that use of Otrivine-Antistin imposes no risk to the subject.

Factors influencing the ocular pulse--the heart rate.

Using pneumotonometry combined with a Langham ocular blood-flow system, measurements of pulsatile ocular blood flow (POBF) were performed in eight ocular normotensive patients with implanted cardiac pacemakers, with the subjects assuming both the erect and the supine postures. Sequential measurements of POBF were made at pre-set values of heart rate over the physiological range between 60 and 120 beats/min at intervals of 10 beats/min. With patients in the supine position, measurements of cardiac output and stroke volume indices were also recorded by impedance cardiography. The mean pulse amplitude of the intraocular pressure (the ocular pulse) decreased as heart rate increased, and this change was statistically significant in both postures according to repeated-measures analysis of variance (erect: f = 18.7, P less than 0.0001; supine: f = 18.8, P less than 0.0001). As measured in supine patients following an increase in heart rate, the pulse amplitude decreased in parallel with a decline in stroke volume index (f = 18.8, P less than 0.0001). Up to a level of 90 beats/min, the mean POBF increased with heart rate, but it declined above this rate in both erect and supine postures. At all heart rates, intraocular pressure was higher when subjects were supine than when they stood erect (f = 4.3, P less than 0.001). At lower heart rates of 70 and 80 beats/min, ocular pulse volume and POBF were significantly lower in supine patients than in erect subjects (70 beats/min: t = 3.89, P less than 0.01 vs; t = 3.87, P less than 0.01; 80 beats/min: t = 2.85, P less than 0.05 vs; t = 2.87, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Factors influencing the ocular pulse--axial length.

The amplitude of the intraocular pressure pulse and pulsatile ocular blood flow (POBF) were correlated with the axial length and refraction of 68 eyes of healthy subjects. Measurements were obtained with subjects in the sitting position using an ophthalmic A-scan and a pneumotonometer linked to a Langham ocular blood-flow system. The amplitude of the ocular pulse and the magnitude of POBF were found to decrease with increasing axial length (r = -0.61, P less than 0.001 and r = -0.74, P less than 0.001, respectively). A similar close relationship was found between the ocular pulse amplitude and POBF and the refractive state of the eye (r = 0.63, P less than 0.001 and r = 0.7, P less than 0.001, respectively). The reasons for the association are discussed and the importance of the observations in the construction of studies in which ocular pulse amplitude or POBF are to be measured in different groups of subjects is emphasised.

Do non-steroidal anti-inflammatory drugs increase colonic permeability?

Urinary excretion of orally administered lactulose and 51 chromium labelled ethylenediamine tetra-acetate (51Cr-EDTA) was measured in 12 healthy adult subjects and in six patients with ileostomies to assess intestinal permeability. In normal subjects, 24 hour urinary recovery of 51Cr-EDTA was significantly greater than that of lactulose (mean (SEM) 2.27 (0.15) v 0.50 (0.08)% oral dose; p less than 0.001), but in ileostomy patients recovery of the two markers was the same. In normal subjects, therefore, the difference between the two markers may arise from bacterial break-down of lactulose but not of 51Cr-EDTA in the distal bowel, urinary excretion of lactulose representing small intestinal permeation and that of 51Cr-EDTA representing both small and large intestinal permeation. The markers were then given simultaneously to nine patients receiving non-steroidal anti-inflammatory drugs (NSAIDs) for rheumatoid arthritis and osteoarthritis. The 24 hour urinary recovery of 51Cr-EDTA in the patients was significantly greater than normal (4.64 (1.20) v 2.27 (0.15)% oral dose; p less than 0.01), but that of lactulose was not significantly affected. Moreover, the increase in 51Cr-EDTA recovery was most noticeable in the later urine collections. Both of these findings suggest that NSAIDs may increase colonic permeability.