Colder air was linked to higher eye pressure in people with glaucoma
What happened
A study published in the British Journal of Ophthalmology has linked colder air temperatures to higher fluid pressure inside the eye in people with glaucoma. The paper came out on 29 September 2026, and BMJ Group publicised the findings the following day. It is titled 'Effects of ambient temperature on intraocular pressure in patients with stable primary open-angle glaucoma under medical treatment'. The researchers looked back at the records of 77 patients with primary open-angle glaucoma treated at a university hospital in Japan between January 2012 and December 2023. That gave them 154 eyes and 2,655 separate pressure readings. The patients were aged over 40, with an average age of 65, and were followed for around five years. The team chose a deliberately stable group. Everyone was over 40, nobody had had eye surgery, everyone attended at least three appointments a year for at least three years, and everyone used between one and four glaucoma eye drops daily in both eyes without a change of treatment during the study. The analysis found that air temperature was significantly and independently linked to eye pressure readings. Lower air temperature went with higher pressure. The size of the link, as reported, was about 1 mmHg of extra pressure for a 35°C fall in air temperature, so the effect per degree is small. The link was clearest in people with more severe glaucoma, and in those using several different eye drops.
Why this matters
Glaucoma is a group of eye conditions where the optic nerve is damaged, usually over many years. Pressure inside the eye is the main thing doctors can treat, which is why almost all glaucoma care is built around lowering it and keeping it low. The damage is gradual and painless. Most people lose side vision long before they notice anything, which is why glaucoma is often picked up at a routine eye test rather than because someone felt unwell. Sight already lost cannot be restored, so the whole point of treatment is protecting what is there. If the pressure a clinic measures drifts up and down with the weather, two practical things follow. A reading taken on a cold January morning may not mean quite the same as one taken in July. And across a British winter, someone whose pressure is only just under control might spend months a little higher than their notes suggest. This is not a reason to be alarmed. It is a reason to keep appointments through the winter rather than letting them slide, and to keep using drops exactly as prescribed when it is cold, dark and easy to forget.
What the evidence actually says
This study is a careful look back at records, not an experiment, and the authors are upfront about what that allows. Because it is observational, it can show a link but cannot prove that cold air causes the rise in pressure. Something else that moves with the seasons could be involved. The group was small: 77 patients at a single hospital in Japan. The strength of the study is the number of readings, 2,655 of them over roughly five years, which is a lot of data per patient. The weakness is that a single-centre group of this size may not represent everyone with glaucoma. The researchers also note that they did not account for lifestyle factors such as exercise and body weight, both of which can affect eye pressure. And they deliberately excluded people whose pressure was poorly controlled, so the findings may not transfer to that group. Importantly, the temperature link was only statistically significant in patients with severe glaucoma or those on multiple eye drops. Whether it holds for people with mild glaucoma is not clear from this work. The authors' own conclusion is measured: the relationship between eye pressure and air temperature in stable, treated glaucoma 'should be considered in a comprehensive treatment strategy'. In plain terms, this is something for clinicians to bear in mind, and a prompt for larger studies, rather than a change to treatment today. It is also worth noting this fits with a wider body of earlier research on temperature and eye pressure, so it is not a lone finding.
Qurexa perspective
Glaucoma treatment is almost entirely about using drops, every day, for years. There is no reward you can feel for getting it right, which is exactly what makes it easy to let slip. In our work delivering prescriptions and supporting medication adherence, running out is one of the most common reasons people miss doses. It is rarely carelessness. It is usually a repeat prescription that was not ordered in time, a pharmacy trip that clashed with something else, or a cold, dark week in which a round trip felt like too much. If winter weather really does nudge eye pressure up, then winter is the worst time for a gap in treatment. That is the honest connection here. Whether you use a delivery service, a reminder app, a pill box or a note on the fridge, the aim is the same: never be in a position where the bottle is empty and the next one has not been ordered.
Practical advice
If you or someone in your family has glaucoma, these steps are worth taking now rather than in February. Use your drops exactly as prescribed, at the same times each day. Linking them to something you already do, such as brushing your teeth, helps more than willpower. Order your repeat prescription before you are down to the last few days. Eye drops often run out sooner than people expect, especially if a drop or two misses the eye. Keep your clinic and optician appointments through the winter. If the weather makes travel difficult, ring and say so rather than quietly missing the slot. Ask your optometrist or eye clinic what your usual pressure range is, and ask what number would worry them. Knowing your own figures makes appointments more useful. If you find drops hard to aim, ask your pharmacist about devices that help position the bottle, or ask to be shown the technique again. Many people have never been taught properly. Have a routine eye test even if your sight seems fine. Glaucoma is usually found this way, and early treatment protects vision. Seek urgent help for sudden eye pain, redness, blurred vision, haloes around lights or vomiting with eye pain. That combination can mean a different and far more urgent type of glaucoma.
What to know
A study of 77 glaucoma patients in Japan, using 2,655 eye pressure readings taken over about five years, found that lower air temperatures were significantly and independently linked to higher pressure inside the eye. The effect per degree was small, and it was clearest in people with more severe glaucoma or on several eye drops. The study cannot prove cause and effect, was carried out at a single hospital, and did not include people whose pressure was poorly controlled. Nothing about your treatment needs to change because of it. What it does strengthen is an old piece of advice: use your drops every day, order repeats early, and keep your winter appointments. Sources: BMJ Group, 'Colder air temperatures may significantly increase fluid pressure inside the eye in people with glaucoma', 30 September 2026, https://bmjgroup.com/colder-air-temperatures-may-significantly-increase-fluid-pressure-inside-the-eye-in-people-with-glaucoma/; British Journal of Ophthalmology, 'Effects of ambient temperature on intraocular pressure in patients with stable primary open-angle glaucoma under medical treatment', 29 September 2026, https://doi.org/10.1136/bjo-2026-330361; News-Medical, 'Cold temperatures may raise eye pressure in glaucoma patients', 29 September 2026, https://www.news-medical.net/news/20260929/Cold-temperatures-may-raise-eye-pressure-in-glaucoma-patients.aspx. This article is for general information and does not replace advice from a doctor, pharmacist, health visitor or other qualified healthcare professional.
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