Dry Eye Article

As an emerging diagnostic tool, ocular surface analyzer provides important support for the clinical diagnosis and evaluation of dry eye.
This expert consensus on clinical application compares traditional examination methods with ocular surface comprehensive analyzers, and presents the development and prospect of future technologies.

Examination Methods:

1. Examination procedure: The principle of gradual examination with less perturbation of the ocular surface followed by a more interfering examination of the ocular surface
2. Tears river height: Schirmer test examination will stimulate the ocular surface which makes the results are more variable. But it has not correlation with TMH. Both TMH and Schirmer experiments have diagnostic significance for aqueous hyposeptic dry eye, which should not be substituted for each other but should be complemented by each other.
3. Tear film break-up time：Fluorescein-stained tear film break-up time is the traditional method for measuring tear film stability.FBUT is an invasive test, and fluorescein alters the state of the tear film. The variability of FBUT and NIBUT is still controversial, and the correlation between FBUT and NIBUT is not strong and cannot be substituted for each other. When the results of NIBUT test are quite different from the clinical signs, it is recommended to combine FBUT test for further evaluation.

Discussion of diagnostic methods

1. Tear film break-up time：Quantitative parameters of the lipid layer of the tear film are significant for diagnostic of meibomian gland dysfunction. It has been reported in the literature that if the thickness of the lipid layer of the tear film is ≤ 60nm as the diagnostic criterion for meibomian gland dysfunction, the sensitivity is 47.9% and the specificity is 90.2%.
2. Examination of tear river height: Lower tear river height>0.20mm, tear river height is normal; lower tear river height ≤0.2mm, tear river height is lower than normal, and this is one of diagnostic criterion for dry eye. Tear river height is moderate abnormal if lower tear river height ≤0.1mm; if there is no way to get the lower tear river height, it is diagnosed to be severe abnormal.
3. Blink inspection：The spontaneous blink frequency of normal adults is about 10~20 times/min, that is, 3~7 times/20s. Abnormal blinkers include blink frequency abnormalities and blink integrity abnormalities.
4. Meibomian gland analysis:The number of upper meibomian glands in normal people is 20~40, with an average of 31; The number of lower meibomian glands is 20~30, with an average of 26. The proportion of meibomian gland deletion < 1/3 is mild; The proportion of meibomian gland loss 1/3~2/3 is the moderate loss, and the proportion of meibomian gland loss > 2/3  is severe loss.

Functional items

1. AI analysis and its functional trend: At present, there have been studies using AI technology to automatically analyze the examination images obtained by ocular surface analyzer, and AI methods have also been used for quantitative and objective analysis of meibomian gland morphology. It is a new trend to load AI on ocular surface analyzer to calculate grading, as well as the establishment of diagnostic prediction models.
2. The significance of blink inspection ：Blink plays an important role in maintaining the normal ocular surface, and most of the blink movements in normal people are spontaneous blinking. Blink examination mainly observes the frequency and integrity of spontaneous blink in patients. According to whether the upper and lower eyelids are in contact during a single blink movement, the blink can be identified as complete blink and incomplete blink to comprehensively evaluate the ocular surface condition of the examinee.