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Case
Cracked by Corneal Topography
By Thomas G. Quinn, OD, MS, FAAO
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Figure 1. JB suffered from severe bilateral ptosis. |
Corneal
topography is widely recognized as an invaluable tool in managing patients who have
keratoconus and pellucid marginal degeneration as well as those undergoing refractive
surgery and corneal molding. But it can also uncover other causes of visual problems
that might otherwise go undetected. Here are two cases to illustrate this point.
Multiple Images for Many Years
Patient JB is a 53-year-old university professor who presented
to the office sharing a history of perceiving multiple images in each eye since
age 9. He also suffered from severe bilateral ptosis (Figure 1) and a right intermittent
exotropia.
JB had seen numerous specialists over the years and no one had
determined the cause of or provided relief from his visual disturbances. JB drew
what he saw when viewing a spot of light from a laser pointer (Figure 2).
Best
corrected visual acuity was 20/20 in each eye at 6M with a refraction of OD –1.75
–1.00 x140 and OS –1.00 –1.25 x066. Slit lamp examination of the
anterior segment revealed no apparent abnormalities of the cornea or crystalline
lens of either eye. The retina in each eye appeared quiet. Covering either eye didn't
diminish the perceived multiple images. We then obtained corneal topographic maps
(Figure 3).
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Figure 2.
JB drew what he saw when viewing a spot of light. |
Observing
the topographic changes and their similarity to the images drawn by JB, we thought
the visual disturbances might be associated with subtle topographic changes near
the line of sight. We applied spherical GP lenses of the following parameters: OD
7.87mm base curve, 9.8mm/8.0mm overall diameter/optic zone, –2.00D; OS 7.80mm
BC, 9.8mm/8.0mm OAD/OZ, –2.00D.
After
allowing 10 minutes for settling, we assessed vision with GP lenses in place. Acuity
of 20/20 was obtained with each eye. JB exclaimed,"This is quite remarkable! This
is the first time I haven't seen multiple images in 44 years!"
JB indicated to me that, in addition to the visual improvement
the contact lenses provided, the peace of mind he has gained from knowing why he
has experienced the multiple images over these many years has been an even greater
gift.
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Figure
3. JB's corneal topographic maps.
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Breaking Open the Case
We had a suspicion that the observed topographical changes in
this case were induced by pressure from the upper eyelids. Regardless, topography
provided valuable information in uncovering the source of JB's visual difficulties
and ultimately improving his visual well-being.
Dr. Quinn is in group practice
in Athens, Ohio, is a diplomate of the Cornea and Contact Lens Section of the American
Academy of Optometry and advisor to the GP Lens Institute.
Contact Lens Spectrum, Issue: May 2006