The diagnosis of the aqueous deficient dry eye, keratoconjunctivitis sicca, remains a major clinical problem. Available diagnostic tests are either erratic and inconsistent e.g. Schirmer test or measure phenomena other than tear production i.e. epithelial dessication (Rose Bengal), enzyme content of tears, Lysozyme or Lactoferrin) or tear osmolarity. Tear flow as measured by fluorescein dilution is generally considered to be the best index of aqueous tear production. Surprisingly, no extensive clinical stueies employing this modality in normals and clinically symptomatic abnormals have been published. Moreover, reports to date on other diagnostic tests have not been correlated with this reliable measure of aqueous tear production. This study will measure aqueous tear production by fluorescein dilution in normal and clinically symptomatic abnormal human subjects, to determine possible statistically significant correlations with commonly used diagnostic tests, e.g. the Schirmer test, tear osmolarity, Rose Bengal staining and tear lysozyme levels. The development of a truly extended wear contact lens awaits a lens design consistent with significant tear exchange beneath the lens. The effects of five parameters of lens design on tear exchange will be studied using high molecular weight fluorescein isothiocyanate dextran solutions. These solutions do not penetrate hydrophilic gels of high ater content or the corneal epithelium. The effects of the same five parameter of lens design on the corneal spithelium will be studied. Wide field specular microscopy of the human corneal epithelium reveals patterns of exfoliation which differ in contact lens wearers. The applications of these two techniques i.e. fluorophotometry of the tears and in vivo wide field specular microscopy of th epithelium will answer some critical questions in tear production, tear exchange beneath hydrophilic lenses, and contact lens design effects on epithelial integrity.
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