Phentolamine drops improved dim-light vision in a phase 3 trial

Design

Phase 3, multicentre, double-masked, placebo-controlled randomised trial

Population

About 145 adults with dim-light vision disturbances and mesopic pupils ≥5 mm

Primary outcome

Improvement in mesopic low-contrast best-corrected acuity

Effect

21% vs 3% at day 15 (P < 0.01)

LYNX-1, a phase 3 double-masked trial published in the American Journal of Ophthalmology on 2 September, randomised about 145 adults with dim-light vision complaints, large mesopic pupils and reduced low-contrast acuity to 0.75% phentolamine drops or placebo nightly for 14 days. The largest subgroup had previous corneal refractive surgery.

At day 15, 21% on phentolamine met the trial's threshold for improved mesopic low-contrast acuity against 3% on placebo. Glare, halos and starbursts improved. Redness and vital signs did not differ, and adverse events were mainly mild.

Phentolamine blocks the dilator muscle and narrows the pupil, which reduces aberrations in low light. For patients troubled by night-vision symptoms after refractive surgery, it is an option to watch. The trial was short, and its regulatory status in India is unknown.

• Ask patients after refractive surgery specifically about night glare and halos.
• Note that most patients in the trial did not reach the improvement threshold.
• Treat this as short-term evidence; the trial ran for two weeks.
• Check availability and regulatory status before discussing it with patients.

Why it matters

Night-vision complaints after refractive surgery have had few treatments beyond reassurance.

Don't overread it

A two-week trial; the refractive surgery result was a post hoc subgroup.

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