Before using pH paper check the expiration date and that it has been stored properly. Tear off a small piece and gently touch it to the fornix of the patient's eye, between the palpebral and bulbar conjunctiva. You can touch it directly to the bulbar conjunctiva if the patient's eye is numb. Topical anesthetic drops are acidic and can alter the pH test. Wait several minutes before checking pH if topical anesthetic drops were used. Compare the pH paper to the reference on the packaging. Normal pH is 7.0, which is neutral.