Year : 1985 | Volume
: 33 | Issue : 4 | Page : 213--216
Tear film break up time (B.U.T.) in non-contact lens wearers and contact lens wearers in normal Indian population
SK Chopra, Saramma George, R Daniel
Christian Medical College and Hospital, Ludhiana, India
S K Chopra
Professor and Head of contact lens department, C.M.C. Ludhiana-141008
|How to cite this article:|
Chopra S K, George S, Daniel R. Tear film break up time (B.U.T.) in non-contact lens wearers and contact lens wearers in normal Indian population.Indian J Ophthalmol 1985;33:213-216
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Chopra S K, George S, Daniel R. Tear film break up time (B.U.T.) in non-contact lens wearers and contact lens wearers in normal Indian population. Indian J Ophthalmol [serial online] 1985 [cited 2021 Sep 22 ];33:213-216
Available from: https://www.ijo.in/text.asp?1985/33/4/213/30793
The precorneal tear film is essential for the maintenance of vision as well as the health of the cornea. The stability of the precorneal tear film is reflected in tear film break up time (B.U.T.) which is the elapsed time from the latest blink until the occurence of the first dry spot in the precorneal tear film. The role of tear film B.U.T. as a reliable clinical tool in diagnosing mucin deficient dry eyes is not yet established.
This present study is designed to find out the average tear film B.U.T. in normal Indian subjects and its relationship to age, sex, palpebral fissure width and blink rate. This study also aims at determining the effect, if any, of contact lens on tear film B.U.T.
MATERIAL AND METHODS
Hundred non-contact lens wearers (200 eyes) and fifty asymptomatic, regular contact lens wearers (100 eyes) of Indian origin, residing in Punjab were included in this study. Subjects with systemic diseases e.g. rheumatoid arthritis, sarcoidosis, scleroderma etc. or ocular diseases e.g. entropion, ectropion, trichiasis etc. which are known to affect the tear film B.U.T. were excluded from the study. Subjects who had been on topical ophthalmic medications or systemic medications such as oral antihistamines, belladonna derivatives, tranquilizers were discarded from the study.
The tear film B.U.T. was studied by Lemp's method. Small quantity of fluorescein was introduced into the conjunctival sac from a moist sterile fluorescein strip and the precorneal tear film was scanned using the cobalt blue filter on a slit lamp bio-microscope until the first break or dry spot appearred. The interval between a complete blink and the appearance of the first break in the precorneal tear film was noted with the help of a stop watch. Test was repeated three times in succession for each eye to determine the average tear film B.U.T. Tear film B.U.T. was performed by the same method on contact lens wearers, 30 minutes after removal of the contact lens.
Palpebral fissure width at the junction of medial one third and lateral two third of the lids was measured while the subject's eyes were in the primary position. Spontaneous blink rate was counted while the subject's attention was deviated through conversation.
In the non-contact lens wearers group (200 eyes) the tear film B.U.T. ranged from 1.67 to 40.33 seconds, with a mean of 7.81± 6.63 seconds [Table 1]. The mean tear film B.U.T. in males was 8.90 seconds and in females was 6.98 seconds. The tear film B.U.T. in males and females is not statistically significant (P>0.5) [Table 1]. Subjects were divided into four age groups. The age tear film B.U.T. correlation was analysed. No significant age related variation in tear film was detected in this study (r=0.14) [Table 2]. Relatioship between tear film ween tear film B.U.T. and blink rate. Relationship between tear film B.U.T. and palpebral fissure width [Table 4] was statistically analysed and no correlation was found between the two.
The age of contact lens wearers ranged from 10-40 years [Table 5]. The tear film B.U.T. in this group varied from 1.3 to 20 seconds with a mean of 7.26±3.83 seconds. No statistically significant difference in tear film B.U.T. was found between noncontact lens wearers and contact lens wearers (P>.05) [Table 6]. Mean tear film B.U.T. in hard and gas permeable contact lens wearers was found to be 7.76 seconds and 6,28 seconds respectively, and this difference was not of any statistical significance (P>0.05) [Table 7]). The relationship between tear film B.U.T. and duration of contact lens wearer is shown in [Table 8]. The difference in values did not reach statistical significance (P>0.05).
Tear film B.U.T. has been studied by various authors to assess the clinical usefulness of this test, but with conflicting results. Norn from his study concluded that the tear film B.U.T. is of no clinical importance in Ophthalmic practice. Lemp and Hamill from their study recommended tear film B.U.T. to be an excellent diagnostic technique in detecting mucin deficient dry eyes.
As per his criteria tear film B.U.T. less than 10 seconds is abnormal and suggests mucir deficient dry eye state. Sukul et al in their study on normal Indian subjects (202 eyes) found the mean tear film B.U.T. to be 9.67 seconds which is much less than the mean alue reported from the western countries.
In this present study the tear film B.U.T. was found to be varying from 1.67 to 40.33 seconds with a mean of 7.81 seconds. Tear film B.U.T. less than 10 seconds was found in 77% of our normal subjects. According to Shapiro and Merin it is possible that wide fluctuation in temperature and humidity may influence the tear film B.U.T. The lower humidity, higher temperature and old healed Trachoma in Punjab might be responsible for the lower tear film B.U.T. in our study.
In our study the mean tear film B.U.T. was found to be 8.90 seconds and 6.98 seconds in males and females respectively. The difference in values is not statistically significant. There was no correlation between tear film B.U.T. and blink rate. On statistical analysis, it was found that palpebral fissure width did not influence the tear film B.U.T.
Hamano reported the tear film B.U.T. to be reduced in contact lens wearers. In our study the mean tear film B.U.T. in contact lens wearers group was found to be 7.26 + 3.83 seconds. No statistically significant difference in tear film B.U.T. was found between non-contact lens wearers and contact lens wearers.
Difference in tear film B.U.T. in hard and gas permeable contact lens wearers was not statistically significant. Even though it appears that the tear film B.U.T. shortens with prolonged contact lens wear, the difference in value did not reach statistical significance probably due to the small number of subjects in the groups with longer duration of contact lens wear.
Tear film B.U.T. was performed by Lemp's method in 200 eyes of 100 normal non-contact lens wearers and 100 eyes of 50 normal contact lens wearers of Indian origin, residing in Punjab. Age, sex, palpebral fissure width and blink rate did not influence the tear film B.U.T. The difference in rear film B.U.T. in non-contact lens wearers and contact lens wearers were not statistically significant. The type and duration of contact lens wear also did not influence the tear film B.U.T.
In view of the large standard deviation and the wide range of normal values, great restriction must be placed on the interpretation of this test. Tear film B.U.T. may be of supportive value in the diagnosis of dry eyes. However, it is not, in itself, of any conclusive value in this condition.
|1||Norn, M.S , 1969, Acta Ophthalmol., 47. 865.|
|2||Lemp, M.A., and Hamill, J.R., 1973, Arch. Ophthalmol., 89: 103,|
|3||Sukul, R.R., Shukla, M. and Nagpal, G. 1983, Ind. J. Ophthalmol., 31 : 325.|
|4||Shapiro, A, and Merin, S., 1979, Amer, J. Ophthalmol., 88:752.|
|5||Hamano, H., 1981, Contact intraocular lens Med. J. 7 : 205.|