IPL and the bacteria on your eyelids: a small trial in contact-lens wearers

There is a long-standing idea that uncomfortable contact lens wearers carry a heavier or differently balanced bacterial load on their eyelids than wearers who feel fine. A small randomised trial from the University of New South Wales, published in 2026, asked a narrow question: does intense pulsed light (IPL) change the number of bacteria on the eyelids of symptomatic lens wearers, and does that change line up with feeling better?

We have already covered what IPL is and how the wider evidence stacks up in our post on IPL for dry eye and what the trials show, so this article sticks to the bacteria question.

What the trial did

Eighteen adult lens wearers with a Contact Lens Dry Eye Questionnaire (CLDEQ-8) score of 12 or more, the usual cut-off for "symptomatic", were randomised to real IPL or sham. Ten went to the IPL group and eight to sham, and all eighteen completed the study. Both groups had two sessions three weeks apart (day 0 and day 21). IPL was delivered with a Lumenis M22 across the cheeks below the eyes, with eye shields on. The sham group had the same shields and gel, an inactive handpiece, and a torch and sound effects to mimic the real thing.

The trial was double masked: neither the participants nor the person measuring outcomes knew who had real IPL. And both groups had meibomian gland expression (the in-office oil gland squeezing we describe in our post on debridement, expression and lavage) straight after every session. So the comparison is IPL-plus-expression against expression alone.

A swab was taken from the lower eyelid margin of the right eye only, at day 0, day 42 and day 90, cultured, and the bacteria counted as colony-forming units (CFU) per swab.

What they found

The bacteria were the usual eyelid residents: coagulase-negative staphylococci (mostly Staphylococcus epidermidis), Bacillus and Corynebacterium species.

In the IPL group, counts fell between day 0 and day 42 in every major category (mean ± standard error):

• Total gram-positive cocci: 174.0 ± 11.5 to 122.0 ± 8.4, p < 0.001
• Total gram-positive rods: 174.0 ± 8.2 to 126.0 ± 8.2, p < 0.001
• Coagulase-negative staphylococci: 174.0 ± 12.2 to 122.0 ± 10.0, p < 0.001
• Bacillus spp.: 172.0 ± 8.2 to 122.0 ± 9.9, p < 0.001

A P-value is the probability of seeing a change at least this large if IPL actually did nothing. A P-value below 0.001 means chance alone is a very unlikely explanation for the day-42 drop. It says nothing about how big or how meaningful the drop is.

By day 90 the counts had climbed back part of the way (cocci 148.0 ± 10.6, rods 147.0 ± 8.8, coagulase-negative staphylococci 148.0 ± 11.3, Bacillus 168.0 ± 11.5) and were no longer statistically different from baseline. The sham group showed no statistically significant change at any visit (cocci 156.0 ± 9.3 at baseline, 140.0 ± 12.6 at day 42, 146.0 ± 16.2 at day 90).

Two other findings matter. The proportion of people carrying each organism did not differ between groups at any visit. And the ratio of cocci to rods, which earlier work suggested might be skewed in uncomfortable wearers, did not change in either group (IPL 1.00 ± 0.10 vs sham 0.93 ± 0.10 at baseline, p = 0.70; 1.02 ± 0.30 vs 1.00 ± 0.20 at day 90, p = 0.81).

Fewer bacteria, but not why you feel better

The same group had already reported, in a separate paper, that comfort and gland secretion scores improved in the IPL group at day 42. So the authors checked whether the people whose counts fell most felt best. They did not. After adjusting for age and sex, no correlation between bacterial load and either the CLDEQ-8 score or the gland secretion score reached statistical significance (cocci versus CLDEQ-8 at day 42 in the IPL group: r = 0.43, p = 0.28).

The authors' reading is that a reduction in culturable bacteria "alone may not directly explain" the improvement, and that IPL may work through several pathways at once: better oil gland function, less inflammation, changes to small blood vessels, and possibly microbiome shifts that culture cannot see. That fits how we think about dry eye: treat the cause, not the symptom.

What the studies can't tell us

• It is very small. Eighteen people, ten in the IPL arm, from one university clinic in Sydney. Each bacterial count is based only on the eyes that grew that organism: between three and six per group at each visit.
• There is no head-to-head statistic for bacterial counts. Each group's change is reported against its own baseline; no direct IPL-versus-sham comparison of CFU with a confidence interval or P-value is given. The between-group tests that were reported (isolation frequency and cocci-to-rod ratio) showed no difference.
• Both arms had gland expression, so the trial cannot say what IPL does compared with no treatment.
• The groups were not well matched. The IPL group was 90% female with a mean age of 35.3 ± 13.2 years; the sham group was 50% female and 28.9 ± 6.3 years. The authors flag this as possible confounding.
• The effect was transient. Two sessions only, and the reduction had largely faded by day 90. Whether more sessions would hold it is untested.
• One swab, one eye, one method. Right lower lid only, cultured on agar; bacteria that do not grow in culture were not counted. No adverse-event table is given.

The authors report no competing interests, and no device-company involvement is stated.

What this means for lens wearers in Hamilton

We would not recommend IPL on the strength of this trial's bacteria counts, and the authors do not either; they call it "preliminary evidence" that IPL "may transiently modulate" the eyelid bacteria. What it supports is a more modest point: when a lens wearer improves after IPL, the reason is probably a combination of things, and a swab count is not the whole story.

That is why the optometrist team at Rose Optometry (Jagrut Lallu, Jacqueline Rowe and colleagues) starts with a paid Dry Eye Evaluation rather than a treatment. Meibography, gland expression and lid margin examination help us work out whether your discomfort is mainly an oil gland problem, a lid margin problem, a lens fit problem, or a mix. IPL is one of several tools in our range of dry eye treatments, and you can read how we deliver it on our IPL therapy for dry eye page. For a full assessment, the Rose Optometry dry eye clinic in Hamilton is the place to start.

Where to get this looked at

If you live in Hamilton, the two places to start are Rose Optometry in the city, where the optometrist team (Jagrut Lallu, Jacqueline Rowe and colleagues) runs the dry eye clinic, and Visique Rototuna Optometrists on the north side of town. Both are member practices of the Dry Eye Specialist Group and work the same way: a paid Dry Eye Evaluation first, to find out what is actually driving your symptoms, and only then a treatment plan.

If you don't live in Hamilton, see your local Dry Eye Specialist Group member. The group is a network of independent practices across New Zealand that share this treat-the-cause approach: Illume Eye Care (Ponsonby, Auckland), Bay Eye Care (Tauranga), Feilding Visique Optometry, Naylor Palmer Optometrists (Palmerston North), Ashburton Eyecare and Milburn & Neill Optometrists (Dunedin), alongside the two Hamilton practices. Find your nearest one on the member practices page.

Reference

• Dumpati S, Iqbal F, Vijay AK, et al. The effect of Intense Pulsed Light therapy on eyelid bacterial load in contact lens discomfort. Cont Lens Anterior Eye. 2026;49(5):102717. PMID 42472534. https://doi.org/10.1016/j.clae.2026.102717