558

AMERICAN JOURNAL OF OPHTHALMOLOGY CORRESPONDENCE

Letters to the Editor must be typed double-spaced on 8V6 X 11-inch bond paper; with IVi-inch margins on all four sides, and limited in length to two manu­ script pages. MEDICAL WRITING

Editor: In his excellent editorial, "Toward a better understanding of medical reports" (Am. J. Ophthalmol. 79:1054, 1975), Alfred Sommer's tongue-in-cheek remark that "an in­ vestigator can automatically demonstrate that an agent is useless by using small numbers of patients and finding 'no statistically sig­ nificant difference between two groups'" contains an important lesson in clinical in­ vestigation. Absence of statistical signifi­ cance in an observed difference does not necessarily mean absence of a real difference —it may merely mean that the numbers were too small to detect such a difference. For this reason confidence limits are more informa­ tive than significance tests. For a difference to be important it needs to be both medically (or biologically) im­ portant and statistically significant. When numbers are too small they cannot produce evidence of statistical significance, and when they are large they may result in statistically significant differences that are medically un­ important. An expensive headache remedy that increases the probability of relief from 60 to 63% may not be worth the extra cost, no matter how statistically significant the difference. Medical articles containing numerical data require careful scrutiny. As Alfred Sommer says, "If we are to avoid being misled and hope to make sense of conflicting claims, we must overcome our diffidence and learn to read these works critically." FRED EDERER

Bethesda, Maryland

SEPTEMBER, 1975

BOOK R E V I E W S SYNOPSIS OF OPHTHALMOLOGY, 4th

ed.

By

William H. Havener. St. Louis, C. V. Mosby, Co., 1975. Clothbound, 594 pages, table of contents, index, 345 black and white figures. $14.50 The fourth edition of Havener's fine basic textbook for medical students continues to emphasize ophthalmoscopy with a little less than one third of its pages devoted to this subject. The synopsis is unusually readable and diagrams and photographs are used effectively. The book should not be under­ estimated as it covers a large variety of afflictions of the eye. There is adequate cov­ erage of everything from neuro-ophthalmology to surgery of the eye. The book has an excellent glossary and superb index, both of which are essential parts of a synopsis in­ tended for students. It may be that the ophthalmic synopsis written for medical students will be replaced by audiovisual materials in the future, but un­ til the value of the latter are proven, the text­ book remains the standard for comparison. This synopsis is a fine addition to the medical student's library and is more than adequate for his needs. J. TERRY ERNEST

By Karl Velhagen. Germany, VEB Georg Thieme, 1974. Clothbound, 300 pages, table of con­ tents, over 100 black and white figures, 21 color plates. $18.60

HELPER DES AUGENARZTES.

This is a concise and precise book for the ophthalmic assistant. The first few chapters deal with the structure and function of the eye emphasizing errors of refraction and their corrections. A few of the most important ocular diseases are mentioned and defined. The main part of the book concerns the functions and obligations of the assistant. This is dealt with in three main chapters: (1) The assistant in the office practice. This

Letter: Medical writing.

558 AMERICAN JOURNAL OF OPHTHALMOLOGY CORRESPONDENCE Letters to the Editor must be typed double-spaced on 8V6 X 11-inch bond paper; with IVi-inch ma...
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