The tear breakup time or BUT is the method used in ophthalmology to study the stability of the tear film.
This test is performed to analyze the degree of evaporation of the tear and its quality. Among the conditions that this test helps diagnose, the Dry eye syndrome.
En Área Oftalmológica Avanzada We explain below what the tear breakup time is and what the normal BUT values are.
What is tear rupture time?
The tear rupture time or BUT is the diagnostic instrument that allows knowing the time it takes for the tear to break since the last blink.
Through this test the doctor can evaluate the tear film, know its stability and degree of evaporation to determine the quality of it.
People who have poor quality tears or suffer from syndrome of Dry Eye have a shorter than normal tear break-up time, that is, the tear film breaks up sooner exposing the cornea to environmental factors.
Dry eye syndrome is a condition that occurs when tear production is deficient or of poor quality. Lack of ocular hydration causes serious discomfort such as burning, itching, tearing and the sensation of having a foreign body or grit inside the eye.
As measured?
Traditionally, to study tear stability, the Schimer test is performed and/or the tear breakup time is analyzed by instilling fluorescein into the eye.
To calculate the tear breakup time, fluorescein was instilled on the ocular surface so that the ophthalmologist can correctly observe the tear film and thus measure the time it takes to break up from the last blink.
To visualize the tear film using this method, the slit lamp.
We currently have much more advanced technology that makes this measurement easier and gives us much more reliable and secure values than the traditional method.
In our center we have an advanced technological device that allows us to analyze, in high resolution and digitally, the tear breakup time. After the test, the values that this technology yields is a map that tells us where and when the tear film breaks, as well as making a video of the eyelid dynamics to be able to visualize and analyze this process in slow motion.
The technology to measure the tear breakup time that we use in our ophthalmology center is the Keratograph of the Oculus house (the image is the one that corresponds to the beginning of this article).
What are the normal BUT values?
We consider normal values of tear breakup time if the tear film breaks 10 seconds after the last blink.
If the test shows that the cut-off point of the tear is 10 seconds, its sensitivity is considered to be 77,8%. The greater the time that the tear film remains without breaking, we will consider that it is of better quality.
The action of blinking is vital in regulating the integrity of the tear film. By having the BUT values and the blink rate, the Eye Protection Index (OPI) can be defined.
When the BUT is greater than the blink rate, the ocular structure It is protected.
What instrument is used to measure tear breakup time?
To measure the tear breakup time in a traditional way, the slit lamp is used.
This equipment is a binocular microscope that contains a very powerful light that allows the ophthalmologist to observe structures of the eye in three dimensions.
The slit lamp has an important power ampThe oscillator between 6 and 40 increases. This function helps the ophthalmologist examine in detail parts of the anterior eye area as Eyelids, conjunctivacornea iris, anterior chamber and crystalline.
In the most advanced ophthalmological centers for the diagnosis of dry eye we use new technological platforms such as the Oculus Keratograph or the SBM Sistemi, specific to study this pathology. You can find both in our ophthalmology center.
Do you need more information about tear break-up time? In Área Oftalmológica Avanzada We will solve all your doubts, come and see us!
