the
contact lens exam
Using
Video Documentation to Improve GP Lens Fitting
BY STEPHEN P. BYRNES,
OD, FAAO, & MICHAEL BERZANSKY, OD
If a picture is worth 1,000 words,
then a video clip can speak volumes. Simultaneous video evaluation of different
GP fitting parameters is a great way to perfect your fitting skills. Following
is an inexpensive method to modify a digital video camcorder to aid in the evaluation
of the anterior segment and contact lens fits.
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Figure
1. Place camcorder with close-up lens and yellow filter six inches from patient.
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Getting Started
To move a camera's "Infinity"
focal point closer (about six inches from the patient), attach a +7.00D close-up
lens ($15) to the camcorder's objective lens using Velcro tape ($3) (Figures 1 and
2). For fluorescein patterns, attach a Wratten #12 yellow filter ($10) to the close-up
lens using Velcro; set the slit lamp's cobalt-blue light to full intensity and move
the housing to the
side.
Video Camera Tips
Set the camera to "Manual
Focus," with the focus set for "Infinity." Set the exposure to "Manual," and adjust
accordingly to maximize the video color and resolution (darker eyes require higher
exposure). With the +7.00D close-up lens attached, the wide-angle/tele-photo feature
of the video camera becomes a zoom magnification system. Using the "Wide Angle"
setting, you can fully view the lid/lens relationship of both eyes simultaneously.
By using the "Full Zoom" magnification, you can see details such as the individual
red blood cells flowing through the limbal capillary vessels.
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Figure
2. Use Velcro tape to attach the close-up lens and yellow filter to the camera.
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Capturing Video
We use a Panasonic SV-AV100
camcorder and record in standard resolution MPEG 4 video format. The video clips
appear as
video file "Thumbnails" on the 512 MB memory card. To create a new "Thumbnail,"
pause the camera or turn it off.
You can move thumbnails to your
computer's hard drive by cutting and pasting them from the memory card. The advantage
of thumbnails is that they're much easier to access and find what you need than
scanning through an entire video looking for a particular scene.
Steps to Improved GP Fitting
Using Microsoft PowerPoint,
you can import multiple video clips per slide to simultaneously evaluate several
fitting parameters at once. Follow these steps to run multiple video clips: Open
"Control Panel," click on "Display," choose "Settings," then "Advanced," then "Troubleshoot."
Adjust the "Hardware Acceleration" to a slower setting, save, then close the
window. (Return the setting to "Full" to view a DVD).
Dr. Byrnes maintains
a primary care private practice with specialization in contact lenses in Londonderry,
NH. Dr. Berzansky is a 2005 graduate of the Pennsylvania College of Optometry.
Contact Lens Spectrum, Issue: June 2005