Mydriasis and glaucoma: exploding the myth. A systematic review

AIMS

To investigate the risk of inducing acute glaucoma following mydriasis.

METHODS

Systematic review of published research 1933-1999.

RESULTS

The risk of inducing acute glaucoma following mydriasis with tropicamide alone is close to zero, no case being identified. The risk with long-acting or combined agents is between 1 in 3,380 and 1 in 20,000. The presence of chronic glaucoma constitutes no additional risk.

CONCLUSIONS

Mydriasis with tropicamide alone is safe even in people with chronic glaucoma. It should be advised in all patients when thorough retinal examination is indicated.

Effect of phenylephrine on aqueous humor flow

The effect of topical 2.5% phenylephrine hydrochloride, an alpha adrenergic agonist, on the rate of aqueous humor flow was studied in the eyes of 22 normal human subjects. The drug and a placebo were administered by random assignment from coded containers with the fellow eye serving as the control. Intraocular pressure, anterior chamber volume, corneal thickness and the rate of clearance of topically applied fluorescein from the anterior chamber were measured. Four of the 22 subjects underwent a study of the effect of phenylephrine on the permeability to fluorescein of the blood-aqueous barrier. No statistically significant effect of the drug was found on the rate of aqueous humor flow, intraocular pressure, anterior chamber volume, corneal thickness or permeability of the blood-aqueous barrier.

Pigment release

Guttae phenylephrine 10% produced a significant decrease in intraocular pressure and increase in facility of outflow in eyes with untreated ocular hypertension. If at the same time pigment was released into the aqueous, the pressure and outflow effect was nullified. Guttae pilocarpine 2% also reduced pressure and increased outflow, but if phenylephrine was added to the pilocarpine 2 responses appeared. If no pigment was released, pressure decreased and outflow increased; if pigment was released, there was no significant change in either. An identical response was shown by eyes with treated open-angle glaucoma. In eyes with treated exfoliation glaucoma pilocarpine and phenylephrine combined produced a significant increase in pressure and decrease in outflow because of pigment release. Finally, 18 eyes are described in which pigment release produced a mean increase in intraocular pressure of 14 mmHg. An acute release of pigment has an outflow-blocking effect that can be readily demonstrated. It provides an explanation for some of the paradoxical responses that occur after the instillation of autonomic drugs. It also provides a sufficient explanation for glaucoma associated with pigment dispersion.

Guanethidine - adrenaline eye drops in glaucoma simplex. Pupil behaviour and response of intraocular pressure

In the study reported here, the relation between the dilatation of the pupil and the course of intraocular pressure (IOP) is examined in open angle glaucoma patients and in glaucoma suspects after topical administration of the combination of guanethidine 3% and adrenaline 0.5% in one eye drop (GA). By treating one eye with GA and leaving the fellow eye untreated on the same day, there was a symmetrical response of IOP, independent of the mydriasis in the treated eyes. It leads to the conclusion that the mydriatic response has no influence on the course of IOP. The physiological explantation for the symmetrical course of IOP in both treated and untreated fellow eyes seems to be a mediation by the bloodstream of GA to the eye which was left untreated.

3. Phenylephrine hydrochloride

Phenylephrine hydrochloride is a potent, effective, relatively safe drug with few ocular side effects. Side effects from topical instillation are uncommon but include severe systemic cardiovascular effects with elevated blood pressure and stroke. Ten percent phenylephrine should be used with caution in patients with known cardiac disease, hypertension, aneurysms, long-standing insulin-dependent diabetes, or advanced arteriosclerosis. A 2.5% concentration is generally indicated for ophthalmic examination as well as for use in infants and in the elderly. Phenylephrine should not be used in patients with narrow-angle glaucoma, and it is also contraindicated in patients taking monoamine oxidase inhibitors or tricyclic antidepressants.

Phenylephrine provocative testing in the pigmentary dispersion syndrome

Forty-nine patients with bilateral pigmentary dispersion syndrome (abnormal accumulation of pigment in the anterior chamber, principally from the posterior layers of the iris), including 31 patients with pigmentary glaucoma, underwent 10% phenylephrine testing in one eye for evaluation of liberation of pigment floaters into the anterior chamber and the influence of phenylephrine on the intraocular pressure. Ten patients with pigmentary glaucoma developed a 3+ to 4+ pigment response, but only two demonstrated a pressure rise greater than 2 mm Hg. The highest pressure rise observed was 7 mm Hg. Nine patients with pigmentary dispersion syndrome but without glaucoma also developed a 3+ to 4+ pigment response, but none of these had a pressure rise. The incidence of pigment liberation was higher in older patients and in pigmentary glaucoma patients receiving topical antiglaucoma therapy at the time of testing. The extent of iris transillumination did not correlate with the grade of phenylephrine-induced pigment liberation. Two pigmentary glaucoma patients, who did not liberate pigment or have a pressure rise when tested with phenylephrine, did exhibit spontaneous or exercise-induced liberations of pigment into the anterior chamber, with marked rises of intraocular pressure and obstruction of aqueous outflow.

Dilating dangerous pupils

Altogether 85 eyes from patients at risk to the development of closed-angle glaucoma were dilated with either parasympatholytic or sympathomimetic drugs. Of 21 eyes dilated with cyclopentolate 1/2%, 9 developed angle closure and a significantly raised pressure at some stage during dilatation and subsequent miosis. Of 58 eyes dilated with tropicamide 1/2%, 19 developed angle closure and a significantly raised pressure during dilatation. Treatment with intravenous acetazolamide and pilocarpine rapidly returned pressure to normal levels. Six eyes that had previously had a positive provocative test with simultaneous pilocarpine and phenylephrine were safely dilated with phenylephrine alone. Subsequent miosis with pilocarpine produced closed-angle glaucoma in all eyes. The significance of these observations is explained and discussed, and it is suggested that high-risk eyes should never be dilated with cyclopentolate. Tropicamide is safe if elementary precautions are observed. Safest of all, however, is phenylephrine-induced mydriasis and subsequent miosis with thymoxamine drops 1/2%.

The cyclopentolate provocative test in suspected or untreated open-angle glaucoma. I. Effect on intraocular pressure

The mydriasis provocative test with 1% cyclopentolate (CPT) was performed on 218 patients with suspected or untreated open-angle glaucoma, on 431 eyes in all. Gonioscopy was performed before and during the test to ensure that te chamber angles were open throughout. The effect of cyclopentolate on intraocular pressure (10P) in these eyes is reported in the present paper. The mean change in IOP (+/-SD) During CPT was +2.5 +/- 3.1 mmHg in the glaucoma group (196 eyes), +0.4 +/- 2.5 mmHg in the group with suspicion of open-angle glaucoma (235 eyes), and +1.4 +/- 2.9 mmHg in the total series. The difference in IOP change between the groups with glaucoma and suspected glaucoma is statistically highly significant. The incidence of positive responses (IOP rise larger than or equal to 8 mmHg) in the glaucoma group (8.7%: 17 eyes) was significantly higher than in the suspicion group (1.7%: 4 eyes). Significant IOP elevations in the total series were demonstrated in 21 eyes of 18 patients (4.9%). Including the borderline cases, IOP elevations larger than or equal to 5 mmHg were also significantly more frequent in eyes with glaucoma (24.0%: 47 eyes) than in eyes with suspected glaucoma (11.9%: 28 eyes). The occurrence and magnitude of positive responses were not dependent on the initial IOP level. Further analysis of the responder group and clinical studies of the mechanism of IOP elevation on the same patients are presented in parts II and III.