Ankylosing spondylitis (AS) is an inflammatory condition that can affect eyes by contributing to anterior uveitis (in 25% to 40% of patients). However, AS patients can also develop mechanical ptosis, superficial keratitis, episcleritis, scleritis and even corneal ulcers. It usually begins in the second or third decade of life, and its pathogenesis remains unknown. However, a recently published Eye & Contact Lens article suggests its development can be observed via testing used for dry eye evaluation, before more damaging effects set in.

Dry eye, as it turns out, is more common among AS patients due to their higher-than-average tear film instability. The study suggests that ocular surface changes, such as squamous metaplasia in the bulbar conjunctiva, can help identify patients with AS, potentially giving ODs the chance to diagnose them early and help them dodge some of the irreversible complications.

The study’s authors looked at 45 patients with AS and 28 healthy subjects. The right eyes of the subjects in each group were tested with slit-lamp examination, Schirmer I test, tear break-up time (TBUT), conjunctival impression cytology (CIC) and ocular surface disease index (OSDI). The team found that Schirmer I test values were significantly lower in patients with AS (12.2mm ± 8mm vs. 20.3mm ± 9.9mm). TBUT values were also significantly lower, with the AS group reading 3.8 ± 1.9 sec and the healthy group reading 10.1 ± 4.8 sec. The authors say this result suggests that both tear production and tear quality may be affected in patients with AS. The team also noted significant differences in CIC scores between the two groups, with AS patients measuring 2.12 ± 0.7 vs. healthy patients’ 0.57 ± 0.6. AS patients also showed significantly higher OSDI scores (36.5 ± 19.4) vs. the control group (9.1 ± 12.9).

The ocular surface plays a major role in the stabilization of the tear film layer, the authors explain, “primarily by the mucin secreted by goblet cells. A decrease in goblet cells and changes in conjunctival surface epithelial cells disturb the stability of the ocular tear film.” The first-of-its-kind study demonstrates that AS patients have elevated levels of goblet cell loss and more squamous metaplasia transformation of the conjunctival epithelium.