contact lens
case reports
Correcting Higher-order
Aberrations
BY
PATRICK J. CAROLINE, FAAO, & MARK P. ANDRé,
FAAO
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Figure
1. Difference display map of the patient's left eye pre and post corneal reshaping. |
Patient MH underwent routine contact lens corneal
reshaping using Paragon CRT lenses to correct –1.75D OU of myopia. Within
seven days his uncorrected visual acuities were 20/20 OU and
were stable from morning to evening. After one month, MH's only complaint was flare
and glare at nighttime.
Common Ortho-k Issue
Scotopic viewing symptoms are common in orthokeratology, especially
within the first month of the procedure. The reasons for the nighttime symptoms
are multifactorial, but a major contributor may be the common 5mm treatment zone.
In many patients, scotopic symptoms dramatically lessen with time, probably because
of treatment zone stabilization and visual adaptation.
Figure
1 shows the difference display map OS with a –1.87D change in apical power.
The map outlines the margins of the pupil and clearly illustrates a slight temporal
displacement of the 5mm treatment zone.
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Figure 2. Pupil miosis following the use of
Alphagan P. |
An Uncommon Solution
Our CL team decided that MH might benefit from a trial of
the anti-glaucoma drop, Alphagan P (Allergan). McDonald et al (2001) found that
a single drop of Alphagan decreased pupil size approximately 2mm within 30 minutes
and that the miosis lasted approximately six hours (Figure 2).
Figure 3 shows the change in MH's post ortho-k higher-order aberrations
before the instillation of Alphagan P (top display) and 30 minutes after (lower
display). It's clear that a dramatic reduction in spherical aberration as well as
most other higher-order aberrations has occurred. Subsequently, MH reported a dramatic
reduction in nighttime symptoms.
Looking Toward the Future
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Figure 3.
Higher-order aberrations
following corneal reshaping (5.6mm pupil) and 30 minutes
post Alphagan (3.4mm pupil). |
We're currently investigating new corneal reshaping lenses designed
to increase the typical treatment zone diameter to 6mm. Preliminary results have
shown that these designs do indeed lessen symptoms of nighttime glare and flare.
Additionally, a number of our contact lens patients have successfully
used Alphagan P off label to modulate their pupil size (for improved nighttime viewing)
following RK and LASIK procedures, post HSV and in certain cases of keratoconus.
Patrick Caroline is an associate
professor of optometry at Pacific University and is an assistant professor of ophthalmology
at the Oregon Health Sciences University. He is also a consultant to Paragon Vision
Sciences and SynergEyes, Inc.
Mark André is director of contact lens services
at the Oregon Health Sciences University and serves as an assistant professor of
optometry at Pacific University. He is also a consultant for Alcon Labs, CooperVision
and SynergEyes, Inc.
Contact Lens Spectrum, Issue: November 2005