Article Date: 6/1/2005

the contact lens exam
Using Video Documentation to Improve GP Lens Fitting

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.

Figure 1. Place camcorder with close-up lens and yellow filter six inches from patient.

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.

Figure 2. Use Velcro tape to attach the close-up lens and yellow filter to the camera.

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