Once-Nightly Phentolamine Eye Drops Improve Night Vision and Reduce Glare: LYNX-1 Study
USA: A new study has revealed that a once-nightly 0.75% phentolamine ophthalmic solution significantly improved visual acuity and reduced bothersome symptoms such as glare, halos, and starbursts in patients with difficulty seeing in dim light. By day 15, more than 20% of treated patients gained three or more lines on an eye chart, compared with only 3% receiving placebo.
The Phase 3 LYNX-1 trial, published in the American Journal of Ophthalmology by Jay S. Pepose, Pepose Vision Institute, Chesterfield, Missouri, and colleagues, evaluated the effectiveness and safety of 0.75% phentolamine ophthalmic solution (POS) in individuals experiencing dim-light disturbances (DLD) and reduced mesopic low-contrast visual acuity (mLCVA).
Dim-light visual problems can occur due to several causes, including changes following keratorefractive surgery, and may involve difficulty distinguishing objects under low-light conditions along with glare, halos, and starbursts. The investigators assessed whether pharmacologically reducing pupil size could improve these symptoms.
The multicenter, double-masked, randomized, placebo-controlled study enrolled 145 participants who reported DLD symptoms, had a mesopic pupil diameter of at least 5 mm, and had mLCVA of 30 ETDRS letters or worse in the study eye. Participants were randomly assigned to receive either POS or placebo.
Participants administered one drop of the assigned treatment into each eye every night for 14 days. Researchers assessed visual acuity, pupil size, wavefront aberrometry, intraocular pressure, slit-lamp findings, and patient-reported visual symptoms.
The findings showed that POS produced a significant improvement in mLCVA compared with placebo. At Day 8, 13% of patients receiving POS achieved the specified visual acuity improvement compared with 3% in the placebo group. By Day 15, the corresponding figures increased to 21% and 3%, respectively.
- POS significantly improved mesopic low-contrast visual acuity at both Day 8 and Day 15.
- Patients receiving POS reported less severe overall dim-light visual disturbances.
- Symptoms including glare, halos and starbursts were significantly reduced at both assessment points.
- The treatment produced moderate pupil constriction that persisted for at least 20 hours.
- A post-hoc analysis of participants who had previously undergone keratorefractive surgery also showed improvements in visual acuity and patient-reported DLD symptoms.
- Treatment-related adverse events were generally mild and transient, with no significant difference between treatment groups in conjunctival hyperemia or vital signs.
According to the researchers, POS works by constricting the pupil through inhibition of the iris dilator muscle. Importantly, the treatment does not act on the ciliary muscle, potentially avoiding concerns associated with medications that affect accommodation and may carry risks related to retinal tears or detachment.
The authors concluded that once-nightly 0.75% phentolamine ophthalmic solution significantly improved mesopic low-contrast distance visual acuity and reduced photic disturbances in patients with dim-light vision problems arising from different causes. The findings support further investigation of POS as a potential pharmacological treatment for patients troubled by impaired low-light vision, glare, halos, and starbursts.
Reference:
Pepose, J. S., Montaquila, S., Wirta, D., Brigell, M., & Charizanis, K. (2026). LYNX-1: A Phase 3 Study of 0.75% Phentolamine Ophthalmic Solution in Subjects with Dim Light Vision Disturbances. American Journal of Ophthalmology. https://doi.org/10.1016/j.ajo.2026.08.045
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