Indian Journal of Pathology and Microbiology

ORIGINAL ARTICLE
Year
: 2010  |  Volume : 53  |  Issue : 4  |  Page : 692--695

Ocular surface disorder in pterygium: Role of conjunctival impression cytology


Ranjana Bandyopadhyay1, Dipanwita Nag1, Santosh K Mondal1, Susmita Gangopadhyay2, Ketaki Bagchi2, Gautam Bhaduri2,  
1 Department of Pathology, Medical College, Kolkata-700 073, India
2 Regional Institute of Ophthalmology, Medical College, Kolkata-700073, India

Correspondence Address:
Ranjana Bandyopadhyay
1B/3, Uttarpara Housing Estate, 88 B, G T Road, PO- Bhadrakali, Dist- Hooghly - 712 232, West Bengal
India

Abstract

Objective: To study ocular surface abnormalities in patients with pterygium, conjunctival impression cytology was explored as a tool for the assessment of the cytological changes. Materials and Methods: A comparative case control study was undertaken to evaluate the ocular surface disorders in pterygium. Fifty cases of pterygium and 50 age and sex-matched controls were analyzed for the presence of local tear film abnormalities as assessed by the tear film break up time and Schirmer test. The spectrum of changes in cytomorphology was studied in detail using conjunctival imprint cytology. Results: Tear film break-up time and Schirmer«SQ»s strip wetting were found to be significantly different in study and control groups. Studying the cytomorphology of the conjunctival imprint smears, reduced cellularity and squamous metaplasia of different grades was observed more frequently in patients compared to controls. On overall grading of cytological changes, statistically significant difference was noted between the study and control groups (P value 0.00172). Conclusion: From the present study we can suggest that aqueous tear film deficiency leading to ocular surface disorder brings about a change at the cytological level, and ocular surface disorders found in pterygium can be interpreted by conjunctival impression cytology.



How to cite this article:
Bandyopadhyay R, Nag D, Mondal SK, Gangopadhyay S, Bagchi K, Bhaduri G. Ocular surface disorder in pterygium: Role of conjunctival impression cytology.Indian J Pathol Microbiol 2010;53:692-695


How to cite this URL:
Bandyopadhyay R, Nag D, Mondal SK, Gangopadhyay S, Bagchi K, Bhaduri G. Ocular surface disorder in pterygium: Role of conjunctival impression cytology. Indian J Pathol Microbiol [serial online] 2010 [cited 2019 Nov 21 ];53:692-695
Available from: http://www.ijpmonline.org/text.asp?2010/53/4/692/72036


Full Text

 Introduction



Pterygium is a common external ocular disease in the tropics. The prevalence of pterygium increases with age and is also higher in people living in equatorial areas. In severe cases, visual loss may occur due to astigmatism and visual axis obstruction. Although environmental factors including exposure to sunlight and in particular broad band ultraviolet radiation is thought to be most important, local tear film abnormalities are also included among the theories of etiopathogeneis of pterygium. Evidence of clinical correlation of dry eye conditions with pterygium has been accumulating in the recent years. [1],[2]

Conjunctival impression cytology provides information of cell morphology, cell types, topographic cell to cell relationship and thus is useful in detection of cellular alteration particularly in dry eye condition. It has been widely used in the study of ocular surface disorder including dry eye states. [3]

On the basis of this postulation and accumulating information in this field, the following comparative case-control study was undertaken using Schirmer's test; tear break-up time and conjunctival impression cytology to determine the association between ocular surface disorder and pterygium.

 Materials and Methods



Fifty (50) patients with primary pterygium, both unilateral and bilateral, were included in this study and compared with 50 normal controls. Patients already diagnosed as having Sjorgen's syndrome were excluded. Schirmer's test was performed using no. 41 Whatman filter paper (35 X 5 mm). The test was performed both without (Schirmer's I) and with (Schirmer's II) topical anesthesia. Assessment of precorneal tear film stability was done on the basis of tear film break-up time (BUT).

Conjunctival impression cytology was taken using cellulose acetate filter paper (milipore filter paper, 0.22 μm pore size). The filter paper was cut into asymmetric shapes and aligned on the bulbar conjunctiva in a specific orientation. The paper was applied to two sites: unexposed - upper bulbar conjunctiva and exposed- lower bulbar conjunctiva. A longer piece of cellulose acetate paper was used in the pterygium to straddle the area above and below it [Figure 1]. In case of controls the medial side of interpalpebral part of bulbar conjunctive was selected as the exposed site. The strips were placed in a fixative solution containing glacial acetic acid, 37% formaldehyde and 70% ethyl alcohol in a sample holder [3] [Figure 2]. They were stained using periodic acid Schiff (PAS) and Gill's modified Papanicolaou stain. The results were plotted in relation to age and gender. During the examination of the slides the following features were taken into account and findings plotted accordingly: i) Staining characteristics and N / C ratio, ii) Goblet cell density, iii) squamous metaplasia, and iv) Mucin aggregates.{Figure 1}{Figure 2}

 Results



The study was conducted on 50 patients of pterygium and 50 age- and sex-matched controls. Of the total 100 cases analyzed, 44 (44%) patients were males and 66 (66%) females. In patients with pterygium, 35 (70%) of 50 patients had a normal value of tear film BUT of more than 10 seconds and 15 (30%) had abnormal value of less than 10 seconds. In the control group 44 persons (88%) had normal values and 6 persons (12%) had abnormal values. This was found to be statistically significant [Table 1].{Table 1}

Studying the results of Schirmer's test in the patients of pterygium, 30 patients (60%) showed more than 15 mm of Schirmer's strip wetting which is graded as normal, 16 patients (32%) low normal value (i.e. 10-15 mm of Schirmer's strip wetting), 4 patients (8%) had 6-10 mm wetting which is graded as borderline while no patients had abnormal value (less than 6 mm). in the control group 44 persons (88%) had normal value, 6 (12%) had low normal value, and one person (2%) had borderline results while no person had abnormal value. This was found to be statistically significant [Table 2].{Table 2}

The cytomorphology of the conjunctival imprint smears were studied in detail. In the present study group, cellularity was significantly lower in the pterygium group compared to controls. Low cellular yield was obtained in 42/50 patients (84%) and 2/50 (4%) controls. Squamous metaplasia of different grades was observed more frequently in 36/50(72%) patients compared to 3/50(6%) in normal controls. The metaplastic cells were enlarged with pyknotic nuclei and abundant cytoplasm. The number of goblet cells was reduced.

On overall grading, eight patients (16%) had normal grade of CIC. Twenty four (48%) had borderline normal CIC grade. Twelve (24%) had borderline abnormal grading, while six patients (12%) had abnormal grade. In the control group, 39 persons (78%) had normal grade, eight persons (16%) had borderline normal grade, two persons (4%) had borderline abnormal and 1 person (2%) had abnormal grade of CIC. This difference was also statistically significant [Table 3].{Table 3}

 Discussion



According to Youngson, pterygium is a disease of corneal epithelium, basement membrane, Bowman's membrane, superficial stroma and conjunctiva. [4] But even today there is no consensus regarding the exact pathophysiological mechanism underlying pterygium formation although environmental factors, limbal stem cell deficiency, abnormal proliferation of conjunctival epithelium have all been suggested. The present study was a comparative one aimed to find out if there is any ocular surface disorder associated with pterygium.

Mittal et al. reported in 1991 that both BUT and Schirmer's test values were significantly reduced in cases of pterygium indicating the inadequacy of tear film in these patients. [1] Tear BUT has been shown to be shortened significantly in pterygium. [2] Schirmer's test with anesthesia is also decreased in eyes with pterygium with marginal significance. [2] Similar studies have further shown that Schirmer's test values with anesthesia are decreased significantly in the eye with unilateral pterygium when compared with the healthy eye. [5] Our study results also corroborated with these findings.

Impression cytology is a fast, cost-effective and non-invasive tool for the diagnosis and follow-up of ocular surface disorders. The cells collected from the conjunctiva can be subjected to both light and electron microscopic study of individual cellular characters and two-dimensional ocular surface changes can be evaluated as well. Impression cytology usually removes one to three cell layers and is thus ideal for studying surface epithelium rather than basal epithelium or the basement membrane. [6] Egbert first used this method to determine the density of goblet cells in different areas of conjunctiva. [7] The most widespread use of this procedure is detection and grading of squamous metaplasia. Wittpen JR et al. reported in 1989 that the conjunctival imprint cytology is abnormal in children with vitamin A level less than 20 ΅g/dl. [8] In the present study, CIC specimems were examined and staged according to the degree of squamous metaplasia as described by Wittpen. In the normal group, the predominant cells were small epithelial cells found in sheets together with presence of goblet cells and mucin spots. The goblet cells showed a tendency to aggregate into groups; those having abnormal cytology, the predominant cells were large, discrete epithelial cells with rare or no goblet cells. The borderline abnormal showed cytology similar to abnormal, except that few goblet cells were seen. In borderline normal, only some epithelial cells showed abnormal cytology. In another study to evaluate cytological changes in dry eye states, the main feature of impression cytology was squamous metaplasia of epithelial cells and altered goblet cell density in the conjunctiva. [9] Other authors have also tried to stage the conjunctival impression cytology specimens according to squamous metaplasia as was primarily described by Wittpen. [10] Chan et al. have evaluated CIC technique to study ocular surface changes in pterygium. [3] They have found significant squamous metaplasia along with altered goblet cell density in these patients. Sqamous metaplasia of conjunctival epithelium refers to pathologic transition of conjunctival epithelium involving increasing stratification of epithelial cells, together with a loss of goblet cells. Changes in the epithelial cells include enlargement, flattening and pyknotic changes in the nuclei with decreased nucleo-cytoplasmic ratio.

In the present study, squamous metaplasia of different grades was observed in 72% of patients and was considered as most important epithelial feature in describing epithelial changes in pterygium. Grading of squamous metaplasia was done both by Tseng and Wittpen, both of which follows the same criteria of loss of goblet cells and epithelial morphological changes.[11] In the present study, the Wittpen grading system was used as it is simple and easy to work with. This grading system was also followed by Singh et al. while evaluating the status of conjunctival epithelium in xerophthalmia in rural children. [10] Our study found that in patients with pterygium, 48% patients had borderline normal cytology, 24% had borderline abnormal, 12% showed abnormal cytology, while 16% had normal cytology. This proved to be statistically significant when compared to the control group (p = 0.00172). These values suggest that some degree of surface epithelial change, however small, is expected in majority of cases of pterygium. The goblet cells over the surface of pterygium were found to be reduced in comparison to control. These results were similar to those found by previous workers. Tseng et al. studied the possible mechanisms of loss of goblet cells in mucin-deficient disorders of human conjunctiva. They found loss of vascularization and intense inflammation can be correlated with loss of goblet cells. [12]

The use of impression cytology has been suggested in varied fields of ocular pathology including demonstration of squamous metaplasia and documentation of limbal stem cell deficiency. [13] Cells obtained from cornea by impression cytology have been used for investigation of deoxyribonucleic acid (DNA) polymorphisms using polymerase chain reaction. [14] Impression cytology has also been used in detecting ocular surface squamous neoplasia. [15] In spite of extensive research in this field, impression cytology has not yet become a routine diagnostic tool because of its relatively cumbersome and time consuming procedure. However it is said to be an ideal method for investigation ocular surface disorder when the clinical diagnosis needs to be substantiated. Further research in improvement in the technique is required to make this procedure available in routine practice.

 Conclusion



From the present study, we can suggest that uns table tear film is found to a greater extent in patients with pterygium than in control group. Conjunctival squamous metaplasia as evidenced by decreased goblet cell density and altered epithelial cell morphology is found more commonly in patients with pterygium than in control group. So it can be concluded that that aqueous tear film deficiency leading to ocular surface disorder brings about a change at the cytological level, and ocular surface disorders found in pterygium can be interpreted by conjunctival impression cytology.

 Acknowledgment



Dr. Rakhi Banerjee, MS, Assistant Professor, Regional Institute of Ophthalmology, Medical College, Kolkata- 700073, India.

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