Abstract
Purpose: :
The clinical effects of Thyroid-Associated Ophthalmopathy (TAO) on the ocular surface are well-recognised. Numerous factors may be involved, including increased ocular surface exposure, poor nocturnal ocular protection and decreased tear film stability. The aim of this study was to determine leukocyte profiles in the conjunctival epithelium in TAO as compared to healthy controls.
Methods: :
Consecutive patients with TAO presenting to a tertiary referral orbital diseases clinic over a 3-month period were identified. All patients were characterized according to standard TAO and ocular surface clinical activity scores. Conjunctival cells were collected from the superior bulbar conjunctiva using impression cytology with sterile Supor filters, following instillation of 0.4% Oxybuprocaine. Cells were recovered by gentle agitation, stained with fluorochrome-conjugated antibodies and analysed by flow cytometry. Comparisons were made with a cohort of healthy, age-matched individuals (n=15).
Results: :
10 TAO patients (9 female) of median age 51 (range 31-65) years participated. Median TAO duration was 31 (range 12-72) months, with a median Clinical Activity Score of 1 and median exophthalmometry 22.8 mm (range 20-25 mm). Of these, 5 (50%) were systemically immunosuppressed, 5 (50%) described ocular surface symptoms and 6 (60%) had objective signs of ocular surface inflammation. 4 (40%) had reduced tear break-up time and 4 (40%) had evidence of lagophthalmos. There was no change in the total number of conjunctival epithelial leukocytes between TAO and healthy subjects. However, CD3+ T cells (CD4+ and CD8+) were reduced in total number and as a percentage of leukocytes (92 vs. 436 cells, p=0.006; 25% vs. 50%, p=0.001). There was a corresponding increase in monocytes (30% vs. 5%, p=0.004), but no increase in neutrophils. Although there were decreases in other lymphocyte populations (CD4-CD8- T cells, NK, NKT and B cells), these did not reach statistical significance. There was no correlation between the conjunctival cellular profile and any clinical parameter.
Conclusions: :
These data on subjects with long-standing, clinically inactive TAO show a decreased population of CD3+ lymphocytes as compared with healthy controls. This loss of lymphocytes may be related to structural changes in the conjunctiva as a result of increased ocular surface exposure.
Keywords: conjunctiva • autoimmune disease • flow cytometry