Abstract
Keratometric behaviour is a multifaceted issue that many researchers have investigated for years. Many internal and external influences can have an effect on the cornea’s keratometric behaviour. This investigation forms a small part of a larger study that aims at determining the effects that rigid contact lenses might have on keratometric behaviour. This pilot study examined the keratometric behaviour of a single, mildly keratoconic cornea that was fitted with a polymethyl methacrylate (PMMA) contact lens. Sixty successive auto-keratometric measurements were taken immediately before and immediately after three hours of contact lens wear. The data obtained was transformed to dioptric power matrices and were analysed using multivariate statistical methods. This study showed that, at least in one keratoconic cornea, there appeared to be a statistically significant change in corneal curvature under the influence of a PMMA contact lens. The contact lens had also appeared to decrease variation in corneal curvature. There was no control study done on this eye therefore the effects of diurnal variation, if any, could not be established. (S Afr Optom 2010 69(2) 69-76)
Highlights
Keratometric behaviour can be described as the overall change in an individual’s keratometric or anterior corneal state over time which is influenced by known and unknown factors, both of which cause continuous fluctuations in the corneal curvature[1]
E Chetty and WDH Gillan - The short-term effects of polymethyl methacrylate (PMMA) contact lens wear on keratometric behaviour ... cornea curvature in the vertical meridian accompanied by a decrease in corneal curvature in the horizontal meridian)
The CLEK (Collaborative Longitudinal Evaluation of Keratoconus) study[8, 9] has monitored corneal curvature changes in keratoconic patients over an eight year period and has reported increased corneal curvatures in keratoconic corneas as well
Summary
Keratometric behaviour can be described as the overall change in an individual’s keratometric or anterior corneal state over time which is influenced by known and unknown factors, both of which cause continuous fluctuations in the corneal curvature[1]. Studies conducted in an attempt to understand the influence that a rigid contact lens has on keratometric behaviour have all concluded that there is generally an increase in corneal curvature[2,3,4,5,6]. The CLEK (Collaborative Longitudinal Evaluation of Keratoconus) study[8, 9] has monitored corneal curvature changes in keratoconic patients (who were fitted with rigid gas permeable contact lenses) over an eight year period and has reported increased corneal curvatures in keratoconic corneas as well. In our opinion, this increase in corneal curvature reported could possibly be linked to disease progression and not necessarily to rigid contact lens wear
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