The intraocular pressure (IOP) responses to two standard tests of autonomic nerve function were studied in 15 healthy subjects, mean age 33 years (range: 20-64). Both tests are based on cardiovascular reflexes: (1) The rise in diastolic blood pressure provoked by sustained isometric muscle contraction, a response mediated by the sympathetic nervous system and (2) The heart-rate responses to the Valsalva manoeuvre, a response mediated by the parasympathetic nervous system. During sustained isometric exercise, the mean IOP decreased significantly from baseline values of 12.60 mmHg (SEM 0.55) to 11.26 mmHg (SEM 0.32, p less than 0.05) while mean diastolic blood pressure increased by 20.80 mmHg (range: +12 to +53 mmHg). However there was no direct correlation between them (r = -0.05). Post exercise the mean IOP remained significantly lower than baseline values for five minutes (p less than 0.01). During the Valsalva manoeuvre, there was a significant increase in IOP of 7.20 mmHg from a baseline of 12.80 mmHg (SEM 0.45) to 20.00 mmHg (SEM 0.78, p less than 0.001); during the recovery period, mean IOP was significantly lower than baseline values at 12.13 mmHg (SEM 0.39, p less than 0.05). The mean Valsalva ratio was normal at 1.68 (range: 1.2-2.6). The possible mechanisms involved in these responses are discussed.
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.
between the sclera and the conjunctival flap, taking care not to expose the cut back edge of the conjunctival flap to the 5-FU soaked sponge. A typical sponge measured 6 mm (length) by 2 mm (width) by 1 mm (thickness). The sponge was removed, resoaked, and replaced every minute up to 5 minutes. The area was then rinsed with 20 ml of balanced salt solution over a period of 30-60 seconds through a Southampton irrigating cannula. Only after this was completed was a third to a half thickness rectangular scleral flap (4 mm by 3 mm) dissected and raised to the limbus. This was to minimise any intraocular penetration of 5-FU. A block of tissue measuring approximately 3 mm by 1 mm was resected and a peripheral iridectomy performed. The flap was then sutured down with four 10/0 nylon sutures. The back edge of the conjunctival incision was closed in a single layer with 10/0 nylon suture. All patients received postoperative topical dexamethasone metasulphobenzoate 0 1% eye drops four to six times a day and chloramphenicol eye drops four times a day.Eyes were examined on at least day 1, week 1, month 1, 3, 6, and 9 and intervals in between if clinically indicated. Postoperative observations and measurements included visual acuity, intraocular pressure (Goldmann applanation tonometry), slit-lamp biomicroscopy, and fundal examination. ResultsSurgery was performed on 34 eyes of 33 patients with intraocular pressure uncontrolled on maximally tolerated medical therapy. The causes of glaucoma in the eyes are listed in Table 1
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