CLEAR - Contact lens optics.

The most fundamental aspect of a contact lens is its optics; the manner in which the refraction of light is managed to optimise vision to the clinical benefit of the lens wearer. This report presents contemporary information on the optical structure of the eye and the optical models employed to understand the correction of refractive error. The design, measurement and clinical assessment of spherical, aspheric, toric, multifocal and myopia control contact lenses are described. The complexity and variety of multifocal lenses is recognised and detailed information is provided for alternating, simultaneous, diffractive, annular, aspheric and extended depth of field lens designs. In terms of clinical assessment, a contemporary review is provided for the measurement of: visual acuity, contrast sensitivity, through focus curves, reading performance, peripheral refraction, toric displacement realignment and patient reported outcomes. Overall, the paper aims to serve as a resource for the prescribing clinician, who can optimise contact lens corrections for patients by building on the optical rationale of these devices; and also highlights future opportunities for research innovation.

Safety of contact lenses in patients with diabetes.

The purpose of the present study was to determine if increased complications exist among patients with diabetes as compared with individuals without diabetes who wear soft disposable contact lenses for daily wear. Complications among daily-wear contact lens wearers who have worn soft contact lenses for 1 year or more were reported from a retrospective review of records. Eyes from 254 patients with diabetes and 254 individuals without diabetes (control), one eye for each subject, from six clinical practices were compared using chi2 and exact Wilcoxon analyses as appropriate. The overall incidence of complications was 49.8% among eyes of patients with diabetes and 48.0% among controls. The respective values for occurrence of corneal abrasions were 7.9% and 5.9%, those for corneal staining were 3.2% and 5.5%, and those for pain at some time while wearing a contact lens were 17% and 19.7%. No significant difference in complications, corneal abrasions, corneal staining, or experience of pain was found between daily-wear contact lens wearers with diabetes and controls. Thus patients with diabetes showed no increased complications over patients without diabetes for daily-wear soft contact lens wear.