To document cellular thickness changes in the cornea
using the confocal microscope on a group of neophytes wearing
the PureVision lens in one eye and the Acuvue 2 lens on
the contralateral eye.
|In-vivo slit-scanning real-time
confocal microscopy and ultrasound pachometry were performed
on both eyes of 23 subjects (11 M, 12 F, age 23 ± 3
years) at the initial visit (baseline), after three and six
months of lens wear, and after one week during which no contact
lens were worn. Data were analysed using Super ANOVA 1.11
(Abacus Concepts Inc).
|Anterior keratocyte density
did not change between the four visits (F=0.9, p=0.46) and
was no different for the two lenses (F=1.6, p=0.21). Posterior
keratocyte density was similar for the two lenses at the different
visits (F=0.1, p=0.82), but there were differences between
the visits (F=18.44, p=0.0001). Cell counts at the three month,
six-month and final visit were found to be lower than at the
initial visit (Post hoc analysis). No differences were found
between the two lenses (F=0.1, p=0.81) or the four study visits
(F=1.4, p=0.26) for the endothelial cell density. Corneal
thickness was similar for the two lenses at the initial and
final visits, but was greater for the Acuvue 2 lens at the
six month visit (F=4.3, p=0.02).
Corneal thickness changes
were consistent with the relative oxygen performances of
the two lens types. This study demonstrates a reduction
in posterior stromal keratocyte density with extended wear
contact lenses. This reduction does not seem to be related
to the oxygen performance of the lens, and may instead be
related to other factors such as the mechanical presence
of the lens.
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