Hyderabad: A new study has found significant changes in the bacteria and eyelid oil of people with a common type of dry eye. Researchers from LV Prasad Eye Institute (LVPEI) in Hyderabad compared people with meibomian gland dysfunction (MGD) — a condition in which the oil glands in the eyelids become blocked, leading to dry eyes — with healthy people. The study was published in the UK-based Experimental Eye Research journal.In MGD, the oil glands in the eyelids do not function properly. Every time a person blinks, a thin layer of tears spreads across the eye. This tear film has three components: mucus, water and an oily top layer called meibum. Meibum prevents tears from drying too fast. When the glands become blocked, tears dry quickly, causing the eyes to feel dry and sore.Meibum is also believed to fight germs. “So, any change in it may affect the bacteria living on the eye’s surface. Most of these bacteria are harmless, but some can form biofilms, which are sticky layers that help germs survive,” said Dr K Arunasri, research scientist at LVPEI and corresponding author of the paper.The team studied 20 people with MGD and 24 healthy individuals. They grew bacteria from tear samples, identified the different types by analysing their genes and examined their ability to form biofilms. In a smaller group of 12 people with MGD and eight healthy individuals, they also analysed the composition of meibum.The results revealed significant differences. People with MGD had 28 types of bacteria on their eyes, compared with just 12 among healthy individuals. Most of the bacteria identified belonged to a group called Gram-negative bacteria. Further, nearly all the bacteria isolated from people with MGD (97%) were capable of forming biofilms. In comparison, less than half (48%) of the bacteria found in healthy individuals had this ability.The composition of the eyelid oil also differed. It contained higher levels of a type of fat called polar lipids and lower levels of non-polar lipids. This imbalance may affect how the oil spreads across the eye and how long the tear film remains stable. Bacteria capable of forming biofilms were more commonly found in samples with higher levels of polar lipids.“Our study shows that higher levels of polar lipids may be associated with a greater presence of biofilm-forming bacteria. This suggests that the composition of eyelid oil and the bacteria on the eye’s surface may influence each other,” said Anupama Hela of LVPEI. Studies suggest that MGD affects about 48–55% of Indian patients, compared with around 36% of people worldwide. The findings also point to an imbalance in the eye’s bacterial population and an unstable tear film in people with MGD. However, further research is needed to understand the underlying causes. The researchers could not establish which occurs first — changes in the eyelid oil or changes in the bacterial population.
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