Time course of thymoxamine reversal of phenylephrine-induced mydriasis

Reversal of Pharmacologically Induced Mydriasis with Phentolamine Ophthalmic Solution

PURPOSE

To evaluate the safety and efficacy of 0.75% phentolamine ophthalmic solution (POS), an α-adrenergic antagonist, in reversal of pharmacologically induced mydriasis.

DESIGN

Two phase 3, multicenter, placebo-controlled, randomized, double-masked clinical trials in healthy participants.

PARTICIPANTS

Five hundred fifty-three healthy 12- to 80-year-old participants were randomized 1:1 (MIRA 2) and 2:1 (MIRA 3) to receive either POS or placebo eye drops in both eyes.

METHODS

Participants received POS or placebo administered 1 hour after mydriasis, induced by instillation of either 2.5% phenylephrine, 1% tropicamide, or 1% hydroxyamphetamine / 0.25% tropicamide.

MAIN OUTCOME MEASURES

Percent of participants returning to within 0.2 mm of baseline pupil diameter in study eye 90 minutes after POS administration. Safety measures included treatment-emergent adverse events and tolerability measures, including conjunctival hyperemia.

RESULTS

A total of 553 participants were randomized to treatment with placebo (n = 215) or POS (n = 338). A statistically significant greater percentage of participants treated with POS showed reversal of mydriasis at 90 minutes compared to placebo (MIRA 2: 48.9% vs. 6.6% [P < 0.0001]; MIRA 3: 58% vs. 6% [P < 0.0001]) and as early as 60 minutes (MIRA 2: 27.7% vs. 2.2% [P < 0.0001]; MIRA 3: 42% vs. 2% [P < 0.0001]). Between 28% and 34% of participants receiving placebo did not returned to baseline PD at 24 hours after pharmacologic dilation compared with 8% to 11% of patients treated with POS (P < 0.0001).

CONCLUSIONS

Treatment with POS reduced PD within 60 to 90 minutes, with a statistically significant time savings of 5 to 6 hours to return to baseline PD compared with placebo. One or 2 drops of POS rapidly reversed mydriasis in all participants regardless of mydriatic agent or iris color. More participants receiving POS reported a benefit in the resolution of visual symptoms caused by pharmacologically induced mydriasis compared with placebo, with statistically significant differences noted as early as 1 hour. The safety profile was favorable, with the most common adverse effects being mild transient conjunctival hyperemia (11.2%), instillation site discomfort (10.9%), and dysgeusia (3.6%).

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Phentolamine Eye Drops Reverse Pharmacologically Induced Mydriasis in a Randomized Phase 2b Trial

SIGNIFICANCE

After a dilated eye examination, many patients experience symptoms of prolonged light sensitivity, blurred vision, and cycloplegia associated with pharmacological mydriasis. Phentolamine mesylate ophthalmic solution (PMOS) may expedite the reversal of mydriasis in patients, potentially facilitating return to functional vision and reducing barriers to obtaining dilated eye examinations.

PURPOSE

The protracted reversal time after pharmacologically induced pupil dilation impairs vision. We tested the hypothesis that PMOS rapidly reduces pupil diameter in this acute indication.

METHODS

In this double-masked placebo-controlled, randomized, two-arm crossover phase 2b trial, we evaluated the effects of one drop of 1% PMOS applied bilaterally in subjects who had their pupils dilated by one of two common mydriatic agents: 2.5% phenylephrine or 1% tropicamide. End points included change in pupil diameter, percent of subjects returning to baseline pupil diameter, and accommodative function at multiple time points.

RESULTS

Thirty-one subjects completed the study (15 dilated with phenylephrine and 16 with tropicamide). Change in pupil diameter from baseline at 2 hours after maximal dilation with 1% PMOS was -1.69 mm and was significantly greater in magnitude compared with placebo for every time point beyond 30 minutes (P < .05). At 2 hours, a greater percentage of study eyes given 1% PMOS returned to baseline pupil diameter compared with placebo (29 vs. 13%, P = .03), which was this also seen at 4 hours (P < .001). More subjects treated with PMOS in the tropicamide subgroup had at least one eye returning to baseline accommodative amplitude at 2 hours (63 vs. 38%, P = .01). There were no severe adverse events, with only mild to moderate conjunctival hyperemia that resolved in most patients by 6 hours.

CONCLUSIONS

Phentolamine mesylate ophthalmic solution at 1% reversed medically induced pupil dilation more rapidly than placebo treatment regardless of which mydriatic was used (adrenergic agonists and cholinergic blockers) with a tolerable safety profile.

Korean patients taking α1-adrenergic receptor antagonists show lower incidence of intraoperative floppy iris syndrome than western patients

PURPOSE

To evaluate the incidence and clinical manifestations of intraoperative floppy iris syndrome (IFIS) according to iris alterations in Korean patients taking α1-adrenergic receptor antagonists (α1-ARAs).

METHODS

This is a prospective observational study. Two surgeons performed cataract surgery in 758 eyes of 596 patients over a period of 12 months. Past medical history was reviewed, especially whether patients had been taking systemic α1-ARAs. Ultrasound biomicroscopy was performed to measure the iris thickness of the dilator muscle region (DMR) at half the distance between the scleral spur and the pupillary margin. Pupil diameter was measured and the occurrence of IFIS was recorded. Measurements of the α1-ARA group were compared with those of a control group matched for age and sex.

RESULTS

IFIS occurred only in six eyes of four patients on systemic α1-ARA medications (0.8%). Pupil diameter in the α1-ARA medication group and the control group was not significantly different. The difference in mean DMR thickness in patients taking an α1-ARA and in the control group was also not statistically significant (p=0.641). However, within the α1-ARA population, the DMR thickness of IFIS cases was significantly lower than that of non-IFIS cases (p=0.013) CONCLUSIONS: The overall incidence of IFIS was far lower in Korean patients than that reported for western patients. IFIS patients taking α1-ARAs showed significantly greater iris DMR thinning than non-IFIS patients taking α1-ARAs. Our findings indicate that the interaction between α1-ARAs and melanin, which results in iris DMR atrophy and IFIS, is less strong in Korean patients (with dark irises) than western patients.

Comparative pupil dilation using phenylephrine alone or in combination with tropicamide

OBJECTIVE

A prevalence survey of actinic and other eye diseases was conducted in Nambour, Queensland, Australia, in 1992. Pupils were dilated with phenylephrine alone for cataract identification because there were concerns that patient discomfort, due to cycloplegia occurring with the usual dilating agents of tropicamide and phenylephrine, may influence future compliance in an associated intervention study. This validation study was undertaken to measure the possible underestimation of cataract prevalence in this community study, which may have occurred because of inadequate dilation from phenylephrine alone.

DESIGN

The study design was a repeated measures experimental design.

PARTICIPANTS

Forty-seven normal subjects participated in the study. Both eyes were tested.

INTERVENTION

Pupil diameter after dilation with three drops of 10% phenylephrine alone was compared with pupil diameter after dilation with three drops of 10% phenylephrine together with three drops of 1% tropicamide. The two regimens were given to the same subjects 1 week apart. Reversal was attempted with thymoxamine hydrochloride 0.5%.

MAIN OUTCOME MEASURES

Pupil diameter was assessed using a Neitz cataract camera, and accommodation reserve also was measured. Subjects' subjective appreciation of return of ocular function was assessed by a questionnaire. Repeated measures analysis of variance, paired t test, McNemar's test, and Wilcoxon signed rank test were used to analyze outcomes.

RESULTS

Mean maximum pupil size with 10% phenylephrine and 1% tropicamide was significantly larger than pupil size after the use of 10% phenylephrine alone (F1,19 = 18.99, P = 0.0003). However, there was no significant difference between the two dilation regimens when comparing the proportion of subjects who dilated to 6 mm or more (McNemar's X(2)1 = 2.7, P > 0.1). Compared with 10% phenylephrine and 1% tropicamide, pupil diameters were significantly smaller (t46 = 16.77, P = 0.0001), and accommodation reserve greater (t46 = 4.14, P = 0.0001), 40 minutes after reversal with thymoxamine in the group dilated with 10% phenylephrine alone.

CONCLUSION

Pupil dilation with 10% phenylephrine alone, if allowed at least 40 minutes to act, will be as satisfactory for the identification of cataracts in a normal population as 10% phenylephrine and 1% tropicamide and is more acceptable because of reduced problems with glare and accommodation.

Unilateral mydriasis after induction of anaesthesia

Unilateral mydriasis is a disturbing finding during anaesthesia and may indicate serious neurological injury. In addition, the assessment of abnormal neurological findings is limited during general anaesthesia, and therefore requires special consideration. I report finding a dilated right pupil (7 mm, nonreactive to light) after bronchoscopic tracheal intubation and induction of general anaesthesia in a frail, 74-yr-old woman with cervical subluxations and spinal cord impingement. The possible aetiology of the unilateral mydriasis includes the effects of anaesthetic agents, stellate ganglion block, impaired venous return from the head and neck, acute intracranial mass lesion or an haemorrhagic event, direct eye trauma, pre-existing medical or surgical conditions, and inadvertent direct deposition of alpha-adrenergic or anticholinergic agents in the eye. Consideration of these factors, the autonomic innervation of the eye, and an intraoperative "wake-up" test allowed satisfactory neurological assessment in this patient and surgery to proceed. Unilateral mydriasis, while unusual, may be seen during general anaesthesia and requires thorough knowledge of autonomic nerve pathways and pharmacology of the eye for correct diagnosis. In this case, mydriasis was considered to result from phenylephrine/lidocaine spray which was used to provide topical anaesthesia to the airway.