LAUSR

To the Editor: The main and accessory lacrimal glands contribute to the aqueous component of tear film, although their individual roles in basal or reflex tear secretion remain controversial.1–4 Many consider the main lacrimal gland essentially as a reflex secretor owing to the presence of parasympathetic innervation; however, its contribution to the basal tear supply cannot be completely ruled out.4 Tear volume reduces considerably (;40%) after topical anesthesia, but the isolated effects of anesthesia on the secretion of the main lacrimal gland have never been studied before.5 Using a technique first described by Bron in 19866 and later refined by Kim et al,7 we directly visualized the secretory activity of the main lacrimal gland by applying sodium fluorescein strips directly onto the conjunctiva overlying the palpebral lobe of the main lacrimal gland, before and after topical anesthesia. Both eyes of 10 healthy individuals (mean age 23.5 years, age range: 18–29 years; 5 men and 5 women) had the direct assessment of tear secretion performed (Fig. 1) using slit-lamp imaging (SL9900 Elite; Costruzione Strumenti Oftalmici, Italy). All volunteers had no ocular symptoms and had normal Schirmer test values (mean of 30 mm, without anesthesia), normal noninvasive tear break-up times (.10 seconds, IDRA Ocular Surface Analyzer; SBM Sistemi, Italy) with no pathology affecting Meibomian glands or tear drainage. Individuals were instructed to look inferonasally, and the upper eyelid was lifted in the superotemporal direction to expose the palpebral lobe. The washout of fluorescein stain applied onto the exposed palpebral lobes was visualized using the cobalt-blue filter and was video graphed. The images were analyzed using ImageJ software (Wayne Rasband; National Institutes of Health, Bethesda, MD), using protocols described by Kim et al.7 For topical anesthesia, 0.5% proparacaine hydrochloride eye drops (Paracaine; Sunways India Pvt Ltd) were instilled into the conjunctival cul-de-sac, and a cotton bud soaked in anesthetic drops was applied directly onto the palpebral lobe for 1 minute. The video was recaptured 5 minutes after the anesthetic application. The 20 palpebral lobes studied had a median of 4 actively secreting openings [95% confidence intervals (CIs), 3–4; Fig. 1], which markedly reduced to 2 after topical anesthesia (P , 0.0001; Table 1). The median tear flow decreased markedly from 1.05 mL/min (95% CI, 0.87–1.42 mL/min) to only 0.1 mL/min (P , 0.0001; Fig. 1). The median tear flow rate per opening also showed 81% reduction (0.49 mL/min vs. 0.09 mL/min, P, 0.0001). There was zero lag between the touch and flow in the anesthetized eyes as compared to a median lag of 9 seconds (95% CI, 1–20 seconds) in the nonanesthetized eyes (P , 0.0001). Five lobes showed absolutely no secretions after anesthesia despite repeated stimulation over 20 seconds. This study throws some light on whether the main lacrimal gland is primarily a basal or reflex secretor. There is obvious and significant reduction in the secretory activity of the main