Impression Cytology in Different Types of Contact Lens Users

This study compared tear function tests and cytologic changes on the conjunctival surface in asymptomatic patients wearing contact lens of different materials. Included in this study were 40 eyes wearing daily wear 4 week replacement hydrogel (H) lenses, 32 eyes wearing silicone hydrogel (SiH) lenses, 18 eyes wearing rigid gas-permeable (RGP) lenses, and 21 healthy eyes (no lenses) as the control group. Epithelial morphology of the conjunctival surface was evaluated, based on Nelson classification with conjunctival impression cytology (CIC), after the tear break-up time (TBUT) and Schirmer test were performed. The mean values of the Schirmer and TBUT tests were significantly higher in the control group than in the other lens groups (p < 0.001). Grade 0 was the most frequent CIC in the control group (66.7%) and least frequent in the SiH lens group (40.6%); grade I was least frequent in the control and RGP groups (33.3%) and most frequent in the SiH lens group (40.6%). Moreover, grade 2 was most frequent in the SiH lens group (18.8%). There was no statistically significant difference in goblet cell densities between the groups (p = 0.462). In addition to the different Schirmer and TBUT test results between contact lens wearers and healthy non-wearers, some cytologic changes may occur on the ocular surface with direct mechanical effects of contact lenses. This simple and noninvasive technique may be used to evaluate the ocular surface with regard to intolerance to contact lenses

4-{2-Meth­oxy-6-[(4-methyl­phen­yl)imino­meth­yl]phen­oxy}phthalonitrile

In the mol­ecule of the title compound, C23H17N3O2, the methoxy­phenyl ring is oriented at dihedral angles of 13.34 (12) and 88.83 (12)° with respect to the methyl­phenyl and phthalonitrile rings, respectively; the dihedral angle between methyl­phenyl and phthalonitrile rings is 89.67 (10)°. In the crystal structure, weak inter­molecular C—H⋯N inter­actions link mol­ecules into chains. A weak C—H⋯π inter­action is also found.

Changes in corneal structure with continuous wear of High-Dk Soft contact lenses : a pilot study

Despite numerous studies that have considered the effects of extended wear of high-Dk soft contact lenses on ocular physiology, little attention has been paid to the impact of such lenses on central or peripheral corneal thickness and curvature. The present study aims to report the time course of changes in corneal thickness and curvature that accompanies the 30-night continuous wear of new silicone hydrogel soft contact lenses in a neophyte population in a longitudinal study. Methods. Six subjects wore high-Dk lotrafilcon (Dk = 140) on a 30-night replacement schedule for 12 months. Only measurements from the right eye were considered for analysis. Topographical measurements of corneal thickness and curvature were taken. The same parameters were monitored for an additional period of 3 months after lens removal. Results. An almost homogenous increase in corneal radius of curvature was detected for all the locations studied, being statistically significant for the 4-mm cord diameter area. This effect was associated with a progressive thinning effect for the central cornea, whereas midperipheral and peripheral areas did not display such a thinning effect during continuous wear. These effects were still evident for the central cornea 3 months after contact lens wear discontinuation. Conclusions. Continuous wear of high-Dk silicone hydrogel contact lenses is associated with clinically appreciable changes in topographical corneal curvature, whereas only a reduction in corneal thickness is appreciated in the central area. This effect seems to be a result of mechanical pressure induced by these hybrid hyperpermeable materials, characterized by a higher modulus of elasticity. The small sample size compromises the conclusions addressed from this study, and further work will be necessary to confirm the present results.Supported, in part, by MEC (Spain) - PGC under contract PM98-0225