A leading eye expert based at Southampton's university hospitals is urging people to take a break from contact lenses while on holiday to cut the risk of developing sight-threatening infections.
Parwez Hossain, a consultant ophthalmologist at Southampton General Hospital, said attendances at his eye unit's casualty department "almost always" rose in the first week of August through to mid-September as a result of poor lens hygiene and accidents during the summer holidays.
"Although we are making progress in terms of general understanding of the importance of contact lens care, we almost always see an increase in infections when people return from holiday, particularly if they have been to very hot countries," he explained.
There are around 1,200 new cases of contact lens-related infection microbial keratitis each year in the UK's three million wearers - and the number of cases diagnosed at Southampton General tends to increase by around 15% during August and September.
The majority of incidents relate to people over-wearing their lenses or poor lens hygiene. Often, lens wearers have washed their contact lens cases with tap water or have swum or showered in lenses. This exposes them to micro-organisms which enjoy moist environments, such as pseudomonas or acanthamoeba, which infect the front surface of the eye.
Eye casualty staff also see patients who have left solution in direct sunlight or placed lenses in solution they poured out earlier in the day, both of which weaken its power to disinfect lenses. Other patients have developed ulcers as a result of grains of sand becoming trapped between a lens and the eye following a trip to a sandy or dusty country.
"People need to be aware that washing lens cases with water is a danger at any time, but it multiplies in very hot environments when bugs spread more quickly," said Mr Hossain. "Swimming pool water also carries a risk, while pouring solution out and leaving it for long periods will almost void its ability to adequately clean lenses."
"Meanwhile, although this is slightly more unfortunate, not enough people are aware of the vulnerability of lenses on the beach when sand can creep in between the cornea and the lens and begin to wear down the surface of the eye.
"If people aren't able to adhere to the strict safety standards required when wearing lenses, or don't want to be concerned about their eye health when relaxing on holiday, their best and safest option is to take a break and stick to prescription glasses and sunglasses."
Mr Hossain, who is also a senior lecturer at the University of Southampton and a member of the scientific committee of the Royal College of Ophthalmologists, added that those who do develop an infection while abroad should take extensive notes about the tests and treatment they receive to prevent complications when they return.
"For those who do wear their lenses and seek medical treatment for a suspected infection, it is imperative they take details about their care, mainly the medications they have taken, because it is extremely hard for us to track down medical notes from different countries.
"As a result, there are occasions when we're unable to find out if the treatment we start counteracts with what they've taken or, in the worst cases, exacerbates their condition before it makes it better."