Retinoscopy and CVS
Use this simple technique to recheck your findings and to educate patients about computer vision syndrome.
BY LARRY K. WAN, O.D., San Jose, Calif.
Nearpoint analysis is an integral component to most comprehensive visual examinations. Similarly, nearpoint retinoscopy is important to the proper diagnosis and treatment of computer-related vision problems. When you perform nearpoint
retino-scopy, it opens an avenue for discussion with your patient on how to resolve computer vision syndrome (CVS).
Returning to the tried and true
Streak retinoscopy is the standard methodology and is the main retinoscopic technique taught in many institutions. The streak retinoscope was invented around 1920 by Jack Copelan and many of his retinoscopic techniques are still in use today. One advantage of the streak retinoscope is that you can manipulate the light source to be parallel or concave in origin. This allows you to change the light source to allow you the best view of the reflex and to refine the cylinder axis location. Retinoscopic technique has taught us that it's easier to see and judge "with" motion, versus "against" motion. (It's easier to see subtle changes using "with" motion.)
Your retinoscope is also a great tool for rechecking your final refraction results and looking for unusual corneal distortions, warping or irregular astigmatism. I have the same diagnostic toys as everyone else, but I like to use retinoscopy to verify what I want to prescribe for a patient.
ILLUSTRATION BY PATRICK GNAN
Understanding the terminology
The art of retinoscopy entails placing lenses in front of the patient's eye until you observe "no motion" or movement of the light reflex. When you achieve this, you've found the neutralization point.
Static retinoscopy is when you have the patient fixate on a target at optical infinity to relax accommodation.
By contrast, nearpoint
retinoscopy is a type of dynamic retinoscopy in which the patient fixates on a target at near. It's called dynamic because the patient's accommodation is active. This test provides information about where the patient is focusing with regard to the near fixation target. The dioptric difference between the near fixation point (working distance) and the nearpoint retinoscopy measurement (resting point of accommodation), is the lag of accommodation.
For many years and even today, the standard nearpoint retinoscopy target has been a reading card with a one-inch hole in the middle. The technique works, but it's low tech and not impressive when you make a case presentation. Prio has a nearpoint vision tester that's backlit and has various targets, including a Gaussian image display that simulates a computer screen. The device attaches to the nearpoint rod on the phoropter and is battery operated.
It's easy to perform
retinos-copy is simple. While looking through the peephole of the retinoscope, have the patient fixate and read the target symbols, letters or word silently on the target of choice (dynamic retinoscopy card or
Prio). Neutralize "with motion" by adding plus lenses or less minus power, and neutralize "against motion" using minus lenses or less plus power. Using a streak
retinoscope, you can slide the sleeve from plano to concave mode or back to
plano. This will reverse the motion to allow you to observe whatever motion is easier for you to see.
If your starting point is the distance correction, add plus until you reach neutrality or "no motion" with the retinoscope in plano mode. Or you can start with the full reading add and reduce plus until neutrality. Position the retinoscope in concave mode to obtain "with motion" if you are reducing plus or adding minus power. This dioptric measurement is the gross correction needed to correct the patient's nearpoint vision.
It's imperative to maintain the retinoscope's plane of origin with the fixation target plane. These must be at the same distance, otherwise your neutral point will be incorrect. A good technique to verify "no motion" or neutral is by moving the retinoscope closer or farther (in or out) and see the subtle change in motion. Using plano mode with the
retinoscope, you should see more "with motion" if you move closer. As you move farther out from your working distance, you should see "against motion."
Putting it to use
I like to do the computer vision testing near the end of my exam before I dilate the patient. As I flip down my Prio tester, I explain that I'm double checking how the patient focuses his eyes on a computer screen simulation. While I perform nearpoint
retinoscopy, I ask him to read the words silently and I explain that he may need a different correction because eyes focus differently using a computer and that the computer is typically at a different distance than reading material. This naturally leads to a discussion of which correction -- nearpoint variable or computer -- is best for him.
Methods of Nearpoint Testing
- Gaussian Image Testing: Incorporates the Prio vision tester and dynamic
retinoscopy. Plus power added to patient's distance correction until neutrality achieved.
- Near Binocular Fused Cross Cylinder: Plus power added until line equality achieved through a cross cylinder lens at testing distance.
- Nearpoint Range of Accommodation/Proximal Range of Accommodation Midpoint: Midpoint of blur out range of plus and minus lenses at testing distance typically using 20/20 reduced Snellen letters.
- Reduced Best Snellen Acuity: Using a reduced Snellen chart, add plus power and obtain subjective response for best acuity at testing distance.
Dr. Wan is a member of both the California Optometric Association and the American Optometric Association. Contact him at (408)
Optometric Management, Issue: March 2003