Year : 1985 | Volume
: 33 | Issue : 3 | Page : 177--179
Precorneal tear film changes due to soft contact lens wear
Mostafa M Bahgat
Faculty of Medicine, CAIRO University, CAIRO, Egypt
Mostafa M Bahgat
Dr. Salman Fakeeh Hospital Post Box 2537 Jeddah, Saudi Arabia
|How to cite this article:|
Bahgat MM. Precorneal tear film changes due to soft contact lens wear.Indian J Ophthalmol 1985;33:177-179
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Bahgat MM. Precorneal tear film changes due to soft contact lens wear. Indian J Ophthalmol [serial online] 1985 [cited 2021 Jun 16 ];33:177-179
Available from: https://www.ijo.in/text.asp?1985/33/3/177/30816
The contact lens is a foreign body with a hydrophobic surface. When it is placed on the tear film in the eye, it will affect the normal sequence of tear film action. The rigid lens becomes the surface where the tearfilm must coat with a hydrophilic layer but this is difficult due to incomplete blinking.
MATERIAL AND METHODS
The material consisted of 123 patients with 235 soft contact lenses. Fifty four were males and 69 were females, varying in age between 10 and 60 years with the average of 28.4 year. None of these cases had been previous contact lens wearer. Most of the eyes were myopic (-0.50--17.0 diopter), some were hyperopic (+4.0- 6.50 diopters) and few were aphakic.
All the eyes were subjected to thorough examination to be sure that they are all healthy.
The contact lenses (C.Ls.) used were all soft (Bausch and Lomb and Hydron). Before fitting the C.Ls. the initial tear break up time (B.U.T.) and Schimer's test (S.T.) were performed in all the cases. Then the second and third tests were done after variable durations of C.L. use (after one week in 70 eyes, one month in 65 eyes, 3 months in 55 eyes and 6 months in 45 eyes). All the tests were made at least after 8 hours of continuous lens wear and within 15 minutes (second test) and 6 hours (third test) of lens removal from the eye. The tear B.U.T. was done at first followed within 10 minutes with the S.T.
There is a reduction of 58% in the mean tear B.U.T. following lens wear. The rate of tear B.U.T. is improved to 42.3% after 6 hours of lens removal [Table 1]
As the time interval of the lens wear increases there is a larger decrease in tear B.U.T. is noted.
There is a 19.46% drop in the mean Schirmer Test results following C.L. wear. [Table 2]
This drop showed improvement to 14.65% after 6 hours of lens removal. As the duration of lens wear increases, Schirmer values are insignificantly less.
There is a reduction in all age groups (more in old age) and all time intervals (more with longer duration of lens wear).
There is a reduction in Schirmer's values in all age groups (more in old age). This drop is not related to the duration of lens wear except in the age group of more than 40 years old as it is more marked with longer duration of lens use. Following 6 hours of lens removal, Schirmer's results are slightly improving again.
The percentage of B.U.T. decrease is larger as age increases and is more for females than males. Following 6 hours of lens removal B.U.T, values are slightly increasing.
The percentage of Schirmer's decrease is larger as age increases both for males and females, but there is no significant sex difference.
Girard and Moore stated that the use of blue light with high magnification reveals abnormalities in the precorneal tear film due to soft lens wear. The commonest finding is disruption of the tear film with the appeara要ce of dry spots while Hill and Young 3 found that the normal content of the tear film is altered by the presence of the hydro計hilic lens leading to an inadequately wetting capability of the tear film and reduced volume of tears.
Kline and Deluca noted that the precor要eal tear film is affected by contact lens wear. They reported that within few minutes of lens removal from the eye, no patient had a B.UT. more than 20 seconds. Tear B.U.T. showed drop of 54% (61 % for males and 49% for females). This drop is slightly larger with more age of the patient, but without sex difference. They did not comment on B.U.T. after long time of lens removal. They also reported 15% drop in Schirmer results immedsatly following lens removal. The decrease was more with old age. They did not comment on Schirmer values after long time of lens removal.
In our study a drop of 58 % is found in the mean tear B.U.T. immediatly following lens removal from the eye. Then it showed improvement to 42.3% after 6 hrs. The drop is noticed in all age groups and time intervals (more with old age and longer duration of lens wear). The mean tear B.U.T. is more affected in females than males.
The Schirmer values in this study showed 19.46% drop following C.L. wear then improved to 14.65%, after 6 hours of lens removal. These results are insignificantly decreased with longer duration of lens wear. The percentage of Schirmer decrease is more with old age but without significant differe要ce between males and females.
The results of our work indicate that the precorneal tear film, is affected both quanti負atively and qualitatively by soft contact lens wear. The change is noted following one week of lens fitting but is more marked with longer duration of lens wear. The effect is more appreciated in tear B.U.T. than Schirmer test. These changes are slightly improved following 6 hours of lens removal.
The cause of these changes is not well known. It is likely that, wearing a contact lens interfers with the normal wetting mechanism of the corneal surface so leading to more rapid break up of the tear film.
We advise patients who have problems due to fast B.U.T. to use artificial tear sub貞titutes to ensure proper lens hydration and help maintaining good corneal integrity. It also seems that patients who wear soft lenses and have fast B.U.T. must be especially careful to practice good prophylactic clean虹ng techniques, since it rppears that their lenses may be more susceptible to the depo貞ition of proteinaceous surface deposits. Even with careful cleaning, the life expecta要cy of their lenses may be reduced.
Morgan had noted a microgrey dot pattern in eyes wearing soft C.L. soaked in chemical storage solution. While, these may be due to nature of chemical, the exact cause is not known.
In this our, dry corneal spots were seen both with chemical and thermal disinfection techniques.
The difference in Schirmer reading with soft lens wear may be due to disruption of the lipid layer of tear film with more evapo訃ation of tears. Another possibility is the reduction of reflex tear secretion due to diminished corneal sensations following soft lens wear.
Tear break up times and tear production were studied in a series of contact lens wearers both before and following various periods of lens wear. The results showed that both are affected especially the tear break up times. The changes were more marked the longer the lenses had been worn, and with the more age of the patient. There was partial recovery with increasing time after lens removal.
|1||Holes, R.H., 1978, Contact lenses. A Clinical Approach to Fitting. The Williams and Wilkins Co. Baltimore,|
|2||Kline, L.N. and Deluca, I. J., 1975. Second Natonal Research Symp. On Soft Contact lenses. Chicago, Illionois.|
|3||Hill, R M. and Young. W.H., 1973, J. Am. Optom, Ass. 45 : 424.|
|4||Holly, F.J., 1973, Ind. Ophthalmol. Clinics 13 (1); 279|
|5||Girard, L.J. and Moore, C.D., 1969, Proc. Ist S. Africa Ophthalmol Symp. 25,|
|6||Morgan, I , 1974, Canad Ophthalmol Soc. Meeting,|
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