wearing a contact lens have an effect on higher-order aberrations?
If so, is it beneficial or detrimental to vision? Does it make a
difference whether the contact lens is a GP or a hydrogel?
following studies provide some answers to these and other questions.
al (2007) evaluated ocular aberrations in 22 eyes of myopic patients
and 14 eyes of keratoconic patients. In each group, they obtained
measurements both during GP contact lens wear and without lenses on
the eye and compared the differences. The researchers noted no
significant differences in total higher-order aberrations in myopic
patients both with (0.33 �0.14) and without (0.33 �0.12) GP lens
when broken down into specific types of higher-order aberrations,
they detected no significant differences for coma, trefoil or
spherical aberrations when comparing myopic eyes with and without GP
the total higher-order aberrations were not significantly different
with and without GP lenses in the keratoconic group (p=0.056), the
researchers detected a significant difference in vertical coma.
Without a GP lens, the mean RMS for vertical coma in the keratoconic
group was -0.185 �0.228. With a GP lens, the mean RMS for vertical
coma was 0.134 �0.148 (p=0.024).
Interestingly, when they compared individuals who had initially low
ocular aberrations with those who had initially high ocular
aberrations, they found that GP contact lenses reduced higher-order
aberrations in patients who had initially high ocular aberrations.
Conversely, GP lenses increased aberrations in patients who had
initially low ocular aberrations.
et al (2007) evaluated ocular higher-order aberrations in eyes
treated with overnight orthokeratology. They tested 46 eyes of 23
myopic patients and found that treatment with overnight
orthokeratology lenses significantly increased total ocular
higher-order aberrations from an RMS of 0.085 �0.032 to an RMS of
0.297 �0.152 (p<0.0001). More specifically, they detected
significant increases in third-order and fourth-order aberrations.
et al (2005) have reported similar results with overnight
previous studies evaluated patients wearing GP contact lenses.
Roberts et al (2006) conducted a study to determine the effect of
spherical soft contact lenses on higher-order aberrations. They
obtained measurements from 30 eyes of 15 patients wearing their
habitual soft contact lenses and observed a significant increase in
total higher-order aberrations. The researchers reported a mean RMS
of 0.364 �0.129 in eyes without lenses and an RMS of 0.456 �0.175
with lenses (p=0.01). When broken down into coma, trefoil and
spherical aberrations, they detected no significant differences with
and without soft contact lenses (p=0.51, 0.06 and 0.36,
No Simple Answer
these studies it's evident that the effect of contact lenses on
higher-order ocular aberrations is a complicated issue. Several
factors are involved such as patients' higher-order aberrations
before lens wear, the design of the contact lens (spherical GP vs.
orthokeratology) and whether patients wear a soft or GP contact