Purpose:
The central cornea has five to six times as many nerve fibers as the peripheral cornea. Consequently, corneal sensitivity is higher in the central cornea compared to the periphery. It may be suggested that symptoms of dry eye are more prevalent in patients who exhibit greater ocular surface damage of the central cornea. This study examined the relationship between ocular discomfort and central corneal fluorescein staining after exposure to a Controlled Adverse Environment (CAE) in patients diagnosed with dry eye.
Methods:
Two–hundred and twenty–two patients diagnosed with dry eye underwent baseline examinations including visual acuity, tear film break–up time, corneal and conjunctival staining, and injection. Patients were exposed to the CAE which regulates humidity (<10%), temperature (76 ± 6), airflow (constant, non–turbulent), and visual tasking (watching a movie) for 90 minutes. Ocular discomfort was evaluated upon entering the CAE and every 5 minutes thereafter. After the CAE exposure, all ophthalmic examinations were re–evaluated. Outcome measures were graded according to standardized 0–4 point scales (0 = none, 4 = worst). Two categories of central staining were defined: values below and above the 75th percentile (≤0.5, >0.5, respectively).
Results:
The following table shows mean ocular discomfort in patients with central staining ≤0.5 and >0.5 after CAE exposure.
Ocular discomfort was significantly worse in patients with more central corneal staining. This correlation was not observed with any other region of the cornea or conjunctiva.
Conclusions:
The data demonstrates that ocular surface damage in the central cornea exacerbates symptoms of dry eye. This finding highlights the anatomical, physiological, and pathological differences between the central and peripheral cornea. It also provides an improved understanding of the relationship between the signs and symptoms of dry eye.
Keywords: cornea: tears/tear film/dry eye • cornea: clinical science • clinical (human) or epidemiologic studies: outcomes/complications