Al

Participants: This study included 100 patients, who had symptoms associated with dry eye recruited from the out patient department of the Al-Shifa Trust Eye Hospital, Rawalpindi, by convenient sampling.

Outcome measures: The sensitivity of three diagnostic tests; Tear film break-up time, Schirmer test and Rose Bengal staining in correctly diagnosing patients with dry eye.

Results: The mean sensitivity of these tests in diagnosis of dry eyes was 51.5 % for Rose Bengal staining, 50.3% for TBUT and 47.5% for Schirmer’s.

Conclusions: There is no single test that is absolutely diagnostic of dry eyes and performing all three tests in all patients is not cost effective. Depending upon the sensitivity of each test in different groups of patients it is recommended that Rose Bengal stain should be preformed on patients with chemical burns Steven Johnson and Sjogren syndrome. Schirmer test should be performed on patients with trachomatous scarring and postmenopausal females. TBUT should be performed on contact lens wearers and patients with ocular allergic diseases. Al-Shifa Journal of Ophthalmology 2005; 1: 25-29 © Al-Shifa Trust Eye Hospital, Rawalpindi, Pakistan.

Dry eye syndrome or Keratoconjunctivitis sicca is one of the most misdiagnosed ocular conditions. Complaints of patients range from burning, redness, foreign body sensations and photophobia, to stringy mucus, sandy or gritty sensations and tearing. All these complaints are also characteristic of other ocular ailments, so raising doubts about the diagnosis. Tear film stability can be threatened by many eye disorders that disturb tear volume, composition, and hydrodynamic factors.

Originally received: May 15, 2004
Accepted: October 11, 2004
Correspondence to Madiha Durrani, Consultant Ophthalmologist, PO Box 61385 Dubai, UAE

Patients with mild tear film instability complain of annoying eye irritation. Those with severe tear film instability may experience constant and disabling eye irritation and develop ocular surface epitheliopathy and sight threatening sterile or microbial corneal ulceration. A number of diagnostic tests are available to establish a diagnosis of dry eye syndrome. Among these the most commonly available ones are Schirmer test, Rose Bengal staining and tear film breakup time.

Purpose of the study
Patients of dry eye report with a variety of symptoms. Description of the complaints by the patients is at times misleading. The purpose of this study was to identify the appropriate and sensitive methods of diagnosis.

Participants and methods

Study Design: This was a cross sectional prevalence study starting from July 2002 till Dec. 2002.

Subjects: This study included 100 patients, who had symptoms associated with dry eye recruited from the out patient department of the Al-Shifa Trust Eye Hospital, Rawalpindi, by convenient sampling. On the basis of presenting complaints and provisional diagnosis the patients were divided into the following nine groups:

Group 1: Patients with lid-anomalies e.g. blepharitis, history of lid surgery (Ptosis surgery)

Group 2: History of systemic diseases e.g. Sjogren’s or Steven-Johnson Syndrome.

Group 3: Patients with corneal and conjunctival conditions like epithelial defects and pterygium.

Group 4: Patients on drugs like systemic anti-hypertensives and topical Timolol maleate.

Group 5: Patients with trachomatous scarring.

Group 6: Post-menopausal females.

Group 7: Patients using contact lenses.

Group 8: Patients with allergic diseases.

Group 9: Patients with chemical burns.

Diagnostic tests

· Tear film break-up time: fluorescein strip was installed in the lower fornix to stain the tear film. The tear film was examined with Cobalt Blue filter. The time taken till the appearance of first dry spot was noted. The test was repeated three times and the average time taken was noted down. It was taken as positive if the TBUT was less than 9 seconds.

· Schirmer test with out topical anesthesia, using strips of Whatman filter paper in the inferior fornix, at the junction of lateral one third and medial two thirds was performed. Patients were instructed to blink normally. It was taken as positive if wetting was less than 10mm in five minutes

Rose Bengal staining was carried out using Rose Bengal impregnated strips. It was done after Schirmer test to avoid false results. The degree of staining was recorded in each zone on a scale of 0 to 3. It was taken as positive when more than 3 zones were stained. These three zones are, nasal and temporal bulbar conjunctiva and cornea, whereas inferior fornix staining was ignored.

Results
The sensitivity of the three diagnostic tests in different groups of patients is summarized in table below.

Table: Percentage Sensitivity of diagnostic tests used in evaluation of clinical groups

Clinical Groups	I	II	III	IV	V	VI	VII	VIII	IX
No of Patients	20	11	13	16	10	10	6	10	4
No of Patients	20	11	13	16	10	10	6	10	4
Schirmer test
< 10mm / 5min	6	9	2	9	7	6	1	2	3
> 10mm / 5min	14	2	11	7	3	4	5	8	1
% Sensitivity	30%	82%	18%	56%	70%	60%	17%	20%	75%
Tear Film Break Up Time
< 9 Secs	12	8	6	7	7	1	3	5	2
> 9 Secs	8	3	7	9	3	9	3	5	2
% Sensitivity	60%	73%	46%	44%	70%	10%	50%	50%	50%
Rose Bengal
< 3	14	9	7	4	6	0	2	4	4
>3	6	2	6	12	4	10	4	6	0
% Sensitivity	70%	82%	54%	25%	60%	0%	33%	40%	100%

Discussion

In this hospital- based study an attempt was made to find out the sensitivity of various tests performed, in each etiological group of patients.

In the available literature, there is controversy regarding the criteria for diagnosis of dry eyes based on clinical diagnostic tests¹. A number of diagnostic tests have been described in the literature for evaluation of dry eyes. All clinical tests have limited diagnostic value if performed individually or in the absence of severe symptoms. It is not uncommon to find an abnormality of a single tear function test². Thus for diagnosis of dry eyes more then one test should be abnormal.

In this study three tests were performed on the patients. These included Schirmer testing, tear film break up time and Rose Bengal staining of ocular surface. The mean sensitivity of these tests in diagnosis of dry eyes was 51.5 % for Rose Bengal staining, 50.3% for TBUT and 47.5% for Schirmer’s.

Conflicting information commonly results from the Schirmer’s test .It has been reported in the past that Schirmer’s test has a low sensitivity but high specificity³. In my study, the Schirmer test was having an overall sensitivity of 47.5% but it was a highly sensitive test in patients group II of systemic illness i.e. RA, SJ Syndrome and Sjogren (82%), group IX chemical burns (75%), 70% in patients group V of trachoma and 60% in post-menopausal females (group VI). Schirmer test proved to be the most sensitive test in the postmenopausal females indicating a possible relationship with hormonal change. Schirmer Test was performed with out installation of topical anesthesia as the cornea and conjunctiva was preserved from the damaging effects of topical anesthesia and more reliable results for Rose Bengal staining later on.

Tear film breakup time is the only direct evidence of stability of tear film. But the test has its own limitations. The test was therefore conducted carefully, taking average of three readings under same clinical conditions. The study results showed the test to have more than 50% sensitivity for dry eye patients, with highest sensitivity in patient groups of trachomatous complications (group V 70%), contact lens wearers (group XII 50%) and allergic conditions (group VIII 50%).

Previous studies have shown the Rose Bengal test to have high sensitivity and specificity⁴. The results of Rose Bengal, however, can be fallacious in Schirmer and BUT are done before hand, as the contact of filter paper and fluorescein strip respectively, with the conjunctiva and cornea can cause staining of those sites⁵. When interpreting the results of Rose Bengal testing, staining in the lower fornix was ignored for these reasons and only the staining in the inter-palpabral area was considered

The study showed Rose Bengal staining, in spite of its limitations, to be the most sensitive test in-patient with dry eyes (51.5%). It was most sensitive in patients with epithelial defects due to chemical burns (group IX 100%), systemic disorders (group II 82%) lid diseases (group I 70%) and corneal and conjunctival diseases (group III 54%).

In short, this study shows that though Rose Bengal testing is the most sensitive test for KCS, no single test is sensitive enough to predict the disease on its own and more than one test must be performed to confirm the diagnosis.

Conclusion
Diagnosis of dry eye is basically clinical. A detail ocular and medical history, careful ocular examination, a precise Schirmer test, TBUT and Rose Bengal staining of conjunctiva comprise the basic work up for each patient having symptoms suggestive of dry eye. There is no single test that is absolutely diagnostic of dry eyes and performing all three tests in all patients is not cost effective. Depending upon the sensitivity of each test in different groups of patients it is recommended that:

· Rose Bengal stain should be preformed on patients with chemical burns Steven Johnson and Sjogren syndrome.

· Schirmer test should be performed on patients with trachomatous scarring and postmenopausal females.

· TBUT should be performed on contact lens wearers and patients with ocular allergic diseases.

As these tests are highly sensitive for the disease conditions, they can be performed singly to reach a diagnosis.

References

1. Taylor HR, Louis WJ. Significance of tear film test abnormalities. Ann Ophthalmol 1980; 12: 531-5

2. Taylor HR, Louis WJ. Significance of tear film test abnormalities. Ann Ophthalmol 1980; 12: 531-5

3. Farris Rl, Gilbard JP, Mandel ID. Diagnostic tests in KCS. CLAO J 1983; 9: 23-8

4. Goren Mb, Goren SB. Diagnostic tests in -patients with symptoms of dry eye. Am J Ophthalmol 1988; 106: 570-4

5. Bron JA. Duke-Elder Lecture. Prospects for the dry eye. Trans Ophthalmol Soc UK 1985; 104: 801-26