(PDF 481 KB)
A Better Snellen
The following is something that I came upon by chance. Although I can find no reference to its use in the literature, it does work and is very accurate on repeated use.
I started my practice in general ophthalmology in 1971 and still prefer to perform my own refractions. From the beginning it was clear that patients did not like to make mistakes when their Snellen acuity was tested. Patients would often spend considerable time trying to resolve individual letters on the tested line. This added time to the refraction. Although the final result could be quantified, it was never possible to know whether the patient truly resolved a letter or only guessed. I wanted a better way to test Snellen acuity. I never found one that was satisfactory, until recently, when I decided to use the resolution of edge blur as a predictor of Snellen acuity.
Using the retinoscopy findings or last spectacle correction, I choose the first line the patient is able to fully and easily resolve on the Snellen letter chart. Since the patient can resolve all the letters on this line, I refine both the sphere and cyclinder powers and axis with regard to the clarity of the letters presented. Because some of the letters presented have curved contours, determining the astigmatic axis is accurate. I find this method most reliable when using the 20/40 line or below. If the first fully resolvable line is between 20/100 and 20/50, it is often possible for patients to read the 20/40 line after starting the refraction. I will then complete the refraction on this line.
I have found this technique to be especially useful when testing patients with early cataracts and macular degeneration. Almost all of my patients find this easy to do and are generally unequivocal in their responses. The endpoint using this method is consistent with the patient’s endpoint for best Snellen acuity. For example, if the bestcorrected Snellen acuity is 20/20 –3, the patient will achieve the same result using the technique described above. Retesting the line of best resolution almost never improves on the result achieved in refracting the first fully and easily resolvable line. The key idea is that the refraction is performed with regard to the edge clarity of the letters and not their resolution.
I have found that this technique eliminates what I call the alphabet soup method of Snellen acuity testing and gives an endpoint that is verifiable on repeated testing.
Stephen C. Milt, MD
Check out www.twitter.com/aao_ophth and get the latest news and
updates about EyeNet Magazine, the Academy, the 2010 Joint Meeting
in Chicago and more.
An Alternative Disposition
In “Our Code of Ethics: Why Do We Need It?” (Opinion, October), Dr. Richard P. Mills states, “For confidentiality reasons, the enforcement of the Code is invisible to most Academy members. The most severe sanction that can be applied is loss of Academy membership.”
Members may also wish to know that the Academy’s Code of Ethics was reviewed, and then approved, by the Federal Trade Commission in order to develop a code that could be enforced without unreasonable fear of legal action against the Academy on the basis of restraint of trade.
What is not mentioned in the commentary is that the Academy also has the option of developing “an alternative disposition,” which stipulates that the member may maintain his or her membership in the Academy on the condition that he or she agrees to certain actions— such as no longer being able to perform surgery without the approval of that particular surgery on that particular patient by a member of the Academy who has been selected by the Ethics Committee.
There have, in fact, been cases presented to the Ethics Committee that have resulted in alternative dispositions of real substance.
George L. Spaeth, MD
WRITE TO US Send your letters of 150 words or fewer to us at EyeNet Magazine, AAO, 655 Beach Street, San Francisco, CA 94109; e-mail email@example.com ; or fax 415-561-8575. (EyeNet Magazine reserves the right to edit letters.)