Tear production after unilateral removal of the main lacrimal gland in squirrel monkeys.

OBJECTIVE: To study the effects of lacrimal gland removal on basal and reflex tear production and on the ocular surface in the squirrel monkey. METHODS: Unilateral main lacrimal gland removal in 6 squirrel monkeys was followed by Schirmer testing, slit-lamp examination with fluorescein, and collection of basal and reflex (stimulated) tears for analysis of tear protein spectra between 0 and 20 kd, as well as histological evaluation. RESULTS: Schirmer test results showed an 80% decrease in basal tears and a 90% decrease in reflex tears during week 1, and a 32.2% and 33.3% decrease, respectively, at week 20 after surgery, compared with the contralateral control side. However, no gross abnormalities or fluorescein staining were seen in 5 of the 6 monkeys, and the conjunctival surfaces remained normal. The main and accessory lacrimal glands appeared to secrete similar types of proteins. No histological changes were seen in corneal, conjunctival, or eyelid tissues 20 weeks after surgery. CONCLUSIONS: Tears from accessory lacrimal glands were sufficient to maintain a stable tear layer on the cornea, suggesting that so-called basal tear flow is made up of fluid from both main and accessory lacrimal glands and that decreased tear production by the main lacrimal gland is not a causative factor in keratoconjunctivitis sicca. CLINICAL RELEVANCE: This study shows that total removal of the main lacrimal gland does not in itself lead to keratoconjunctivitis sicca. However, the nature of neural control of the accessory glands is not yet clear.

Interface inflammation after laser in situ keratomileusis. Sands of the Sahara syndrome.

PURPOSE: To determine the source of the interface debris that causes the interface inflammation known as "sands of the Sahara" after laser in situ keratomileusis (LASIK). SETTING: Department of Ophthalmology, LSU Eye Center, Louisiana State University Medical Center School of Medicine, New Orleans, USA. METHODS: A microkeratome (Automated Corneal Shaper) was used to make a LASIK flap in 8 eyes of 4 rabbits. In 4 eyes, the blade was used directly from the sterile pack; in the contralateral 4 eyes, the blade was cleaned prior to use. In vivo confocal microscopy of the corneas was performed 1 day after surgery. An unused, cleaned blade and an unused, uncleaned blade, as well as blades used in the rabbit eyes, were examined by scanning electron microscopy. RESULTS: Confocal microscopy revealed numerous fragments of debris surrounded by inflammatory cells in the LASIK flap interfaces created by blades taken directly from the sterile package. Interfaces created by the cleaned blades showed only rare, scattered bits of debris. Scanning electron microscopy of the unused blades showed debris on the uncleaned blade removed directly from the sterile package. CONCLUSION: Post-LASIK interface inflammation may be caused by debris on the microkeratome blade, although other sources are possible. The interface debris and inflammation can be reduced or eliminated by cleaning the microkeratome blade before use.

Characterization of fibrous retrocorneal membrane by confocal microscopy.

PURPOSE: To study the appearance of a fibrous retrocorneal membrane as seen by confocal microscopy. METHODS: A 67-year-old white woman with a history of multiple ocular surgeries, including repeated penetrating keratoplasties for aphakic bullous keratopathy, developed a retrocorneal membrane in the right eye. The membrane was first noticed 3 years after the last corneal transplant and remained stable subsequently. The patient was examined by in vivo white light tandem-scanning confocal microscopy. RESULTS: At the level of the retrocorneal membrane, confocal microscopy disclosed the presence of a hyperreflective fibrous-appearing layer. Normal endothelial cells could not be found. Anterior to the hyperreflective layer, activated keratocytes were identified. CONCLUSION: Confocal microscopy may allow noninvasive diagnosis of fibrous retrocorneal membrane. Additionally, our data suggest that the posterior keratocytes might play a role in the production and deposition of fibrous tissue.

Detection of substance P in human tears by laser desorption mass spectrometry and immunoassay.

PURPOSE: To determine whether substance P is present in human tears. METHODS: Tear samples (1-2 microliters) were collected from one eye of each of 12 subjects. Two of the eyes had dry eye syndrome, two wore contact lenses and had dry eye syndrome, and eight were normal. Five of the eight normal eyes were scheduled to undergo excimer laser refractive surgery, and tears were collected from these eyes before and after surgery. Tear samples were analyzed by laser desorption mass spectrometry. Pooled samples from one individual were subjected to enzyme-linked immunoabsorbent assay. RESULTS: Laser desorption mass spectra of the 18 tear samples displayed well defined peaks with mass to charge (m/z) ratios ranging from 1343.7 to 1355.9 and/or 1356.9 to 1364.7, corresponding to an average m/z of 1349.8 +/- 1.13 for protonated substance P and 1361.2 +/- 0.54 for oxidized substance P obtained from 14 mass spectra of standards formulated with substance P concentrations ranging from 10(-4) M to 10(-12) M. As confirmation, an enzyme-linked immunoabsorbent assay performed twice on pooled tears from one eye detected substance P in both replicates at a concentration of 125 pg/ml (9.26 x 10(-11) M). CONCLUSIONS: These findings demonstrate that substance P is a component of tears obtained from normal eyes of men and women ranging in age from 26 to 60 years, from eyes fitted with contact lenses, from eyes with dry eye syndrome, and from eyes 1 and 2 days after excimer laser refractive surgery. Whether the concentration of substance P in tears varies with sex, age, or eye condition, the source of substance P in tears, and its role in tears remains to be discovered.