The quality of your tears is just as important as the quantity. The Lipid Layer Thickness (LLT) test is a highly advanced, non-invasive diagnostic tool that allows our specialists at Pristine Eye Hospitals to precisely measure the protective oily layer of your tear film. This helps us understand the root cause of your dry eye symptoms for more effective, targeted treatment.
What is a Lipid Layer Thickness (LLT)?
The LLT test uses a technology called interferometry. It projects a gentle, structured light source onto the surface of your eye and captures the reflection. Similar to how oil on water creates a rainbow pattern, the light reflecting off your tear film creates a coloured pattern that the device’s software analyses. Based on the specific colours and patterns, it can calculate the exact thickness of the lipid layer in nanometers, providing a clear, objective measurement of your meibomian gland function.
Why is this test performed?
Your ophthalmologist may recommend an LLT test for several key reasons, including:
To diagnose Evaporative Dry Eye: This is the most common form of dry eye, caused by a deficient lipid layer that allows tears to evaporate too quickly.
To assess Meibomian Gland Dysfunction (MGD): The test directly evaluates the function of the meibomian glands, which are responsible for producing the lipid layer.
To guide treatment decisions: Knowing the lipid layer thickness helps your doctor choose the most appropriate treatment, from specialised eye drops to in-office procedures.
To monitor treatment effectiveness: The test provides a measurable way to track your progress and see if a specific treatment is successfully improving your tear film quality.
How to Prepare for Your Lipid Layer Thickness (LLT)
Preparation for the LLT test is simple and designed to ensure the most accurate results possible. Your tear film should be in its natural state, free from any temporary alterations.
Avoid using any artificial tears or medicated eye drops for at least 2-4 hours before your appointment.
Do not wear eye makeup, as small particles can interfere with the tear film measurement.
If you wear contact lenses, please inform our staff. You may be asked to remove them for a period before the test.
The Procedure: What to Expect Step-by-Step
The entire LLT procedure is quick, completely painless, and non-contact.
1. You will be seated comfortably in front of the diagnostic device, which looks similar to other standard eye examination equipment.
2. You will be asked to rest your chin and forehead against the supports to keep your head still.
3. The specialist will ask you to look straight ahead at a target light and blink normally.
4. The machine will capture a short video of your tear film, and the specialised software will instantly analyse the data to determine your LLT.
Understanding Your Results
The results of your LLT are given as a numerical value, typically measured in nanometers (nm). A thicker, more robust lipid layer (generally considered to be above 75-100 nm) is healthier, as it provides a better barrier against tear evaporation. A thin lipid layer (often below 60 nm) indicates a deficiency and is a key sign of Meibomian Gland Dysfunction and evaporative dry eye.
Your cornea and dry eye specialist at Pristine Eye Hospitals will not just look at the number in isolation. They will interpret your LLT score in the context of your symptoms, a physical examination of your eyelids and glands, and other diagnostic tests. This comprehensive approach allows us to create a personalised treatment plan to restore comfort and protect your vision.
Frequently Asked Questions
Is the Lipid Layer Thickness test painful?
No, the test is completely painless and non-invasive. There is no contact with your eye, no air puff, and no drops are required for the test itself.
How long does the LLT test take?
The actual measurement process is very fast, taking only a few seconds per eye. The entire appointment, including positioning and instruction, usually takes just a few minutes.
Why is this test better than just describing my dry eye symptoms?
Symptoms can be subjective, but the LLT provides an objective, repeatable measurement. It helps your doctor confirm a diagnosis and precisely track your response to treatment over time.