Clinical Study of Focus NIGHT &DAY® contact lenses

Objectives: To investigate the visual and ocular implications of continuous wearing a silicon hydrogel contact lens for up to 3 weeks , in a dry semi-arid climate environment. Methods: Clinical examination of eye conditions (visual acuity, Schirmer test, corneal thickness and endothelial cells counts) for 9 healthy voluntary students was carried out between September and November of 2004 in Riyadh\'s King Saud University clinical facilities, using Ciba Vision\'s ocus Day & Night® lotrafilcon lenses. Which is measured weekly for 3 weeks. Results: Visual acuity testing revealed no significant changes after three weeks of continuous wear of the Focus lens. An average minimum angle of resolution (MAR) of 1.045 min arc was maintained throughout the 3 weeks. No significant drop had been recorded (p>0.05). The Schirmer test for eye lubrication showed an overall decrease in the wetting of the strip from about 36 mm to around 27 mm. Corneal thickness for the 9 subjects perior to CL wearing was 0.529 ± 0.050 mm, slightly increased to 0.533 ± 0.044 mm at the end of the study. The mean cell area value was 359 ± 67 Um2 at first visit, becoming only marginally higher at 361 ± 71 Um2 after three weeks of contact lens wear. Conclusion: The Focus NIGHT & DAY® lenses can be worn safely as extended-wear contact lenses for up to 3 weeks without ocular complications. Visual acuity, tear functions or corneal structure are not altered. Keywords: optometry, silicone hydrogel materials, resolution, ocular.Sudan Journal of Medical Sciences Vol. 3 (2) 2008: pp. 115-12

The pattern electroretinogram (PERG) with contralateral corneal reference

The pattern electroretinogram (PERG) is a sensitive test for investigation of the proximal retina. For monocular recording, the contralateral corneal reference (CCR) electrode position has been suggested as a possible alternative to the conventional ipsilateral temporal reference (ITR). We therefore compared the effect of these electrode positions on 26 subjects (median age 45.5 years, IQR 24.5-61.5). The signals were recorded monocularly with DTL nylon fibre electrodes. The visual stimuli were high contrast 19' black-white checkerboard patterns, reversing 4 times/s. PERG responses obtained from the CCR gave larger amplitudes and the increase in amplitude was statistically significant (P < 0.001). Because the CCR signal is larger, new normative ranges must be established to avoid false negative results