|Year : 1980 | Volume
| Issue : 4 | Page : 183-187
Clinical evaluation of methylcellulose as tear substitute
AT Rangwala, V Kalevar
M & J Institute of Ophthalmology, Civil Hospital Campus, Ahmedabad, India
A T Rangwala
C/o. Gujarat Optical Co. Opp. Central Cinema, Fuvara Ahmedabad-380001
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Rangwala A T, Kalevar V. Clinical evaluation of methylcellulose as tear substitute. Indian J Ophthalmol 1980;28:183-7
The tear substitutes are needed when there is a deficiency of normal tear film. Although the word `dry eye' could literally denote an eye totally devoid of any tear fluid, in its clinical usage it has assumed a far more related meaning. Any eye exhibiting even the minimal of the typical symptoms of dry eye either in presence or absence of any ocular pathology but demonstrating a defective tear film break-up time (TFBT) can be safely designated as dry eye in its wider sense. According to Norn and Lemp et al average TFBT is about 25 to 30 seconds. A break-up time under 15 seconds is considered abnormal.
As an attempt in this direction, various artificial tear substitutes have been tried and are being tried by various workers to supplement defective tear fluid. Rubin tried egg-white in treatment of keratoconjunctivitis sicca. Search for better substitutes then led to use of methylcellulose. Linn found 0.5% concentration of methylcellulose optimum and better than polyvinyl alcohol. However Lemp found methylcellulose a poor match compared to other tear substitutes. Bloomfield and his colleagues tried to use a depot preparation collagen in form of water in lower fornix and obtained good results.
Recently in U.S.A. new water soluble mucokinetic macromolecular polymers with good adsorptive affinity for corneal surface have been found very promising.
Two such products are adsorbobase (Adsorbotear) and duasorb (Tears Naturale). They not only have adsorptive property but also strengthen and stabilize the tear film. Lemp, Goldberg and Rodely while comparing different artificial tear solutions found adsorbobase as most beneficial and on an average it enhanced TFBT by as much as 90 seconds.
Since in India we do not yet have these latest polymer tear substitutes, we have tried to evaluate the clinical efficacy of 0.5% methylcellulose on eye drops.
| Materials and methods|| |
Two groups of patients were selected for this project. First one comprised of 28 patients who consistently had symptoms of watering, irritation, burning, etc. and were observed to have defective TFBT and thus could be labeled as `dry eye. Schirmer's test readings were also taken. These persons were subjected to regular home-use of 0.5% methylcellulose at least three times/day and were evaluated every 15 days for progress.
Second group included 60 patients chosen at random from OPD. After measuring their TFBT and Schirmer's wetting, two drops of 0.5% methylcellulose were put in each eye. TFBT was measured in each case every 15, 30 and 60 minutes and any change, if present, was noted.
| Observations and discussion|| |
It was observed that dry eyes with normal Schirmer's reading had many more chances of improvement in their TFBT. 74.41 % eyes with normal Schirmer's wetting demonstrated favourable response to methylcellulose artificial tear therapy, whereas only 23.08% eyes with abnormal Schirmer's reading could show any improvement [Table - 1]. This observation drawn from actual dry eye patients is quite consistent with the one seen in second group of patients where immediate effect of methylcellulose drops was assessed [Table - 2]. It can be seen that 82.89% eyes with normal Schirmer's test had immediate improvement in their TFBT but only 27.27°o eyes with subnormal wetting of Schirmer's strip could increase their break-up time.
This observation that methylcellulose is by and large efficient in eyes with normal Schirmer's test conclusively proves that aqueous deficient dry eyes are relatively far less benefitted by use of methylcellulose locally. As discussed previously, an eye with defective TFBT along with good Schirmer's wetting is usually a mucous deficient dry eye. Here the innermost adsorbent layer of tear film is deficient resulting in premature breaking up of tear film accompanied by a host of uncomfortable symptoms. Improvement in stability of tear film in these cases should be essentially due to supporting ("Cushioning") or supplementary action of methylcellulose on mucous layer of tear film. In one way or another, methylcellulose appears to enhance the adsorption power of mucin and thus helps in `holding' the aqueous layer with an overall effect of making tear film more stable and less liable to premature breaking.
It was noted that subjective improvement in dry eye patients as judged by their reported comfort from the symptoms was seen in a relatively lesser number of eyes (55.35%) as compared to 62.5% eyes showing demonstrable improvement in their TFBT [Table - 3]. Among the eyes with normal Schirmer's test, only 25 eyes (58.13%) felt subjective relief while in the same group of patients 32 eyes (74.41%) had registered an increase in TFBT [Table - 1]. This discrepancy was obviously on account of the fact that though regular instillation of methylcellulose drops increased TFBT of few very fragile tear films, the new break-up times were still subnormal and relief from the symptoms could not be obtained. Methylcellulose could not make these films stable enough to bring them within the range of normalcy. Almost half the number of patients (46.15% eyes) with abnormal Schirmer's reading used methylcellulose drops very frequently and thus felt symptomatically better. However when objectively assessed, all of them did rot have normal TFBT.
It is seen that almost all the eyes (95.65%) with initial normal TFBT improved their TFBT after instillation of methylcellulose drops [Table - 4]. However only a little more than half the number of eyes (54.63%) demonstrated an increase in TFBT when initial TFBT was abnormal. It is interesting to asses these figures from a different angle i.e. from their Schirmer's test readings.
The 97 eyes in Group - II persons with a defective TFBT initially who were subjected to assessment of effect of methylcellulose, had their Schirmer's test wetting time evaluated and the improvement in TFBT studied from this angle The data in the table below asserts the previous observation that eyes with normal Schirmer's reading stand a better chance of improving their TFBT when methylcellulose drops are used.
It was also found that average increase in TFBT from the basic reading in Group - I patients was 8.08 seconds. The corresponding figures in group-11 patients are presented in [Table - 5]. An average increase in TFBT under different conditions of Schirmer's test and TFBT. It was seen that eyes with normal initial TFBT had shown highest rate of improvement [Table - 4]. The same set of eyes has also showed highest increase in their TFBT i.e. 7.4 seconds, 15 minutes after instillation of methylcellulose drops and gradually decreasing but still maintaining the pace after 60 minutes. Similarly eyes with normal Schirmer's test have shown higher increase in TFBT.
It is also a significant observation that effect of methylcellulose was not very long lasting in group - II patients. After initial instillation of 2 drops in eyes. effect on TFBT gradually started waning and at the end of an hour influence was meagre. This nay necessitate frequent use of drops.
| Summary|| |
Assessment of effectivity of 0.5% methylcellulose eye drops is done by giving it for regular home-use to 28 dry e) e patients and also by noting immediate effect on TFBT after its instillation in 60 patients. Chances of increase in TFBT and thereby making tear-film more stable are 75 to 80% when Schirmer's test readings are normal. However when Schirmer's test is abnormal, improvement in TFBT is seen only in about 25% eyes. Thus methylcellulose is much more effective in mucous deficient dry eye. Subjective relief from symptoms was however seen in lesser number of eyes and was perhaps because tear-film could not be made stable enough to reduce symptoms.
Average improvement in TFBT in dry eye patients was 8 OS seconds. Similarly immediate average improvement seen 15 minutes after instillation ranged between 5 to 7.4 seconds, depending on initial TFBT and Schirmer's test. The beneficial effect became lesser at the end of an hour.
| Acknowledgement|| |
Authors are very thankful to Cadila Laboratories. Ahmedabad for preparing 0.5% methylcellulose drops and supplying the same for this clinical study.
| References|| |
Norn. M.S., 1969, Acta Ophthalmol, 47:865.
Lemp, M.A., 1973, Int. Ophthalmol. Clinic. 13: 185.
Dohlman, C.H., Lemp. M.A, and English, F.P. 1970, Vol. 10, No.2, I.O,C., Little Brown & Co. Boston.
Robin, M.R., 1955, Eye Ear Nose Throat Mon. 34 : 50
Lin, Merit L. and Jones, Lester T., 1968, Amer. J. Ophthalmol., 65: 76.
Lemp, M.A., Dohlman, C.H., and Holly F.J. 1971, Trans. Amer. Acad. Ophthalmol, & Otolaryngol. 75:1223.
Bloomfield, S.E., Dum, M & Miyata, T : 1977, Arch. Ophthalmol. 95:247.
Jones, D.B. : 1977, Transaction of Am. Acad. of Ophthalmol, & Otlarying. 83:693.
Lemp, M.A.,Goldberg M and Reddy M.R.: 1975, Invest. Ophthalmol. 14/3:255.
[Table - 1], [Table - 2], [Table - 3], [Table - 4], [Table - 5]