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Posters
June 2002
REFRACTIVE AND KERATOMETRIC CHANGES
FOLLOWING EXTENDED WEAR
Kathy Dumbleton, MCOptom, MSc, Doris Richter, OD, MASc, Desmond
Fonn,
DipOptom MOptom, Centre for Contact Lens Research, UW;
Robin Chalmers, OD, CIBA Vision, Atlanta, GA
Purpose:
A small but significant increase in
myopia following extended wear of low DK hydrogel lenses
has been previously reported, however the specific impact
of hypoxia on refractive status and corneal curvature with
extended wear are not well documented. The purpose of this
study was to compare that over a period of 6 months extended
wear with experimental high DK (HDK, 140) and lower DK (LDK,
28) hydrogel lenses.
Method:
Ninety-one contact lens wearers
were enrolled in the study and randomly assigned to one of
two groups. The LDK group wore etafilcon A (DK=28) for up
to 7 days and 6 nights (n=32) and the HDK group wore lotrafilcon
A (DK=140) for up to 30 days and 29 nights (n=59). Refractive
error and corneal curvature (Nikon AutoRef Keratometer) and
corneal topography (Alcon eyemap) were measured at 3 monthly
intervals over 6 months of extended wear.
Results:
The LDK group demonstrated
an average increase in myopic correction of 0.50D over the
6 month period (p=0.000). No increase was measured in the
HDK group (p=0.200). The cylindrical component was unchanged
in both groups. A stratified analysis revealed no difference
in degree of myopic change for low (less than -3.00, n=53)
to moderate (-3.00 to -6.00, n=23) myopes in either group
(LDK p=0.071, HDK p=0.204). Keratometric analysis revealed
an average central corneal flattening in both major meridians
of 0.40D in the HDK group (p=0.000, 0.000), but no change
in the LDK group (p=0.426, 0.516)
Conclusions:
Hypoxia from 6 months
of extended wear of lower DK lenses is associated with myopic
progression in adult myopes. Wearing lenses of high DK had
no impact on refractive error and may be associated with
a small degree of central corneal flattening. Supported
by a grant from CIBA Vision, Atlanta, GA
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