Evaluation Of Basic Tear Secretion

    A basic tear secretion test is performed to rule out hyposecretion of the basic tear secretors. Several drops of proparacaine topical anesthetic are applied to each eye and the lower cul-de-sac. The lower cul-de-sac and lower lid palpebral conjunctiva arc blotted with a tissue paper. A Schirmer strip (SMP Division, Cooper Laboratories, San German, Puerto Rico) is bent at its notch, 5 mm from one end, and the strip is placed over the temporal palpebral conjunctiva of the lower eyelid (Fig. 3-12). The patient is instructed to look upward, and the lights are dimmed.

    After 5 minutes, the strip is removed and a measurement is made from the notch to the end of wetting. (Theoretically, it is possible to do this test for 1 minute, rather than 5 minutes, and to multiply the amount of wetting in 1 minute by 3 to obtain an appraisal of the 5-minute level.) Normally, this measurement should be between 10 and 15 mm of wetting in 5 minutes. If it is significantly less, hyposecretion of the basic tear secretors should be suspected. The basic tear secretors consist of the conjunctival goblet cells, the meibomian oil glands, and the accessory lacrimal glands of Krause and Wolfring, and they are believed to keep the eyes moist during normal conditions.


    If basic tear secretion is insufficient, symptoms of ocular irritation may develop or increase following a cosmetic blepharoplasty. In these cases, tightening the eyelid skin by excessive skin resection might lead to lagophthalmos (difficulty in completely closing the eyelids). Whereas a patient with normal tear-secreting eyes might tolerate this condition, a patient with dry eyes may not. This may be the ultimate condition that causes the asymptomatic patient to become symptomatic. If the basic tear secretion test result is low, it is important to ensure that the patient is not taking a diuretic or antihistamine because these drugs can cause a falsely low reading. If so, these drugs should be discontinued and the test repeated.

    In a patient with low basic tear secretion, a cosmetic blepharoplasty might be contraindicated; if such a procedure is done, only a very conservative skin excision should be performed. In any case, patients must be fully aware that they have this problem and that after the blepharoplasty they may have to use artificial tears or a lubricating ophthalmic ointment for the rest of their lives. Some surgeons believe that the cause of the ocular irritation in this situation is excision of too much upper eyelid skin. In my experience, however, the more common cause is lower eyelid retraction or ectropion secondary to excessive resection of lower eyelid skin.

    Repair of blepharoptosis with the possibility of secondary lagophthalmos may also be contraindicated in patients with dry eyes.


Figure 3-12 A basic tear secretion test identifies patients with potentially dry eyes. Schirmer strips are placed over the temporal lower eyelids as the patient looks upward, and the amount of wetting on the strip is measured.