Night-driving glare can turn road lights into a distracting blur.
Photo by Laima
Sirmā on Unsplash.
Oncoming headlights can turn an ordinary night drive into a wall of
glare. For some people, each light stretches into a halo or starburst,
road markings become harder to separate from the darkness and confidence
behind the wheel disappears.
A familiar drug in a new form may offer another option. Researchers
testing daily eye drops containing 0.75% phentolamine have reported
better low-light vision and fewer visual disturbances in late-stage
clinical trials. The idea is elegantly simple: make the pupil moderately
smaller so that less stray light enters around the edges of the eye.
This is promising human research—not a cure for poor night vision,
not a product people can buy for this purpose, and not proof that the
drops will help every driver.
What the Phase III trial
found
The first randomized Phase III study enrolled roughly 145 adults who
had reduced visual acuity in dim conditions as well as problems such as
glare, halos or starbursts. Participants received either phentolamine
drops or placebo drops once daily.
After eight days, 13% of people receiving phentolamine improved by at
least three lines, or 15 letters, on a low-light eye chart. That
compared with 3% in the placebo group. By day 15, the proportion
reaching that threshold had risen to 21% with phentolamine, while the
placebo result remained at 3%.
Participants also rated their overall night-vision difficulty on a
seven-point scale. The average score in the treatment group fell to 3.3
after 15 days, compared with 4.3 for placebo. People using phentolamine
reported fewer problems with glare, halos and starbursts as well. The
findings were published in The American Journal of
Ophthalmology and summarised by Reuters
on 11 September 2026.
That difference is meaningful, but it needs context. Most treated
participants did not gain three complete lines on the
eye chart. A useful treatment does not have to work for everybody, yet
the headline number should not be mistaken for a universal
transformation.
The developer, Opus Genetics, has also announced positive initial
findings from a second Phase III study focused on people with problems
after corneal reshaping procedures. It reported improvements in
difficulty seeing the road around oncoming headlights and glare at dawn
or dusk. Detailed results will matter more than a company summary,
however, because they allow doctors and independent researchers to judge
the size of the benefit, consistency and safety.
How making
the pupil smaller can sharpen the view
Pupil size changes how light enters the eye. Photo by v2osk
on Unsplash.
The pupil is the eye’s adjustable opening. It widens in darkness to
admit more light, but a large opening can also let in peripheral rays
that pass through less optically perfect parts of the cornea. Those rays
can create blur, halos and starbursts—especially when the cornea has
irregularities or has been reshaped by procedures such as LASIK.
Phentolamine blocks alpha-adrenergic signals to the iris dilator
muscle. In plain language, it relaxes the muscle that helps pull the
pupil open. The resulting constriction is moderate and can last for at
least 20 hours, according to the Phase III report.
It works rather like narrowing a camera aperture. A smaller opening
can filter out troublesome peripheral light and improve focus, although
it also admits less light. The balance between those two effects is one
reason the drops must be tested in specific groups rather than assumed
to improve night vision for everyone.
Earlier evidence supports the mechanism. In a randomized Phase II
trial involving just 24 adults, a single 1% dose reduced average pupil
diameter by 1.3 millimetres and improved several measures of contrast
sensitivity and visual acuity. The study reported no adverse events,
although investigators observed a mild increase in conjunctival redness.
Those results were published in BMC
Ophthalmology in 2022.
The biggest
limitation is who was studied
Many participants in the late-stage research experienced symptoms
after corneal refractive surgery, including LASIK. That makes the
results especially relevant to people whose night vision worsened after
their cornea was reshaped.
It also limits how widely the findings can be applied. Night-driving
difficulty can have many causes, including uncorrected short-sightedness
or astigmatism, cataracts, dry eye, retinal disease and normal
age-related changes. A drop that reduces optical aberrations from a wide
pupil will not necessarily address those other problems.
The trial was also short: the main published comparison ran for only
eight to 15 days. Longer follow-up is needed to establish whether the
benefit persists, whether daily use remains tolerable and whether
uncommon side effects emerge.
Fast Track is not approval
The US Food and Drug Administration has granted the programme Fast
Track designation for significant chronic night-driving impairment. That
label allows closer communication with the agency and can make parts of
the review process move more efficiently. It does not
mean the FDA has approved the drops or confirmed that their benefits
outweigh their risks.
The FDA
describes Fast Track as a process for facilitating development and
review of treatments aimed at serious conditions or unmet medical needs.
A developer still has to submit a complete application, and regulators
still have to assess manufacturing, efficacy and safety.
What happens next
The most important next steps are full publication of the second
Phase III trial, longer safety data and clarity on the regulatory plan.
Researchers will also need to identify which type of night-vision
problem is most likely to respond.
If those pieces hold up, phentolamine could become a targeted
treatment for a frustrating problem that currently has no FDA-approved
drug. For now, the science is best described as encouraging rather than
settled.
People who struggle to see while driving at night should not
experiment with pupil-altering drops on their own. New or worsening
night vision can have several causes and deserves a proper eye
examination.
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