As the art of medicine expands, a constant need for new means of expressing ophthalmic conditions is inevitable and essential.
As the art of medicine expands, it is determining such vast changes in our thinking that a constant need for new means of expression is inevitable."1
At one time, without readily available methods to measure the size of the globe, a large eye was considered "myopic" and a small one "hyperopic." Those terms date to the beginnings of scientific visual physiology with Helmholtz and are still in use today. When one speaks, for instance, of "myopic disc" or "myopic degeneration" being a risk factor for angle-closure glaucoma, what is meant is that the conditions are actually due to the elongated, enlarged globe. In addition, "small eyes are not necessarily hypermetropic and hypermetropic eyes are not necessarily small."2 Since my mid 40s, I have become progressively hyperopic. Does that mean my eyeballs are shrinking?
The obstacle to clarity seems to lie in the mixing of two totally different systems and units of measurement. Refractive errors such as myopia and hyperopia are measured by a refractometer (or retinoscope) in optical units of diopters. The length of the globe is measured with compasses, or ultrasound and radiographs, in units of length (mm). There may or may not be any correlation between the two. The same is true for weight (pounds or kilograms) and height (inches or centimeters). A short person may be called "light" and a tall one "heavy." A tall person may indeed be obese, but not necessarily so. Therefore, one's susceptibility to diabetes or hypertension cannot be determined rationally by height.
In order to designate a globe abnormally long or short, it is first necessary to establish the norm using statistics. In our studies of 513 globes in adults,4 the average length of the globe in males, measured by A-scan, was 24.9 mm, and in females 23.9 mm. To determine normal lengths at different age groups, as well as the standard deviations that define abnormality, one may rely on the consensus of the national and international bodies that are in charge of ophthalmic terminology, or on meta-analysis of the data.
Finally, abnormalities of the globe's length may be assigned a number in the International Classification of Diseases (say 743.51 for an abnormally short globe, and 753.52 for a long one). Once this is accomplished, a CPT number may be assigned to the corresponding procedure for measuring axial length (for ultrasound, such as 765.11 and 765.12).
When that is done, the practitioner may legitimately claim reimbursement, because he or she is not likely to be paid when coupling the axial length procedure solely to the diagnosis of, say, esotropia, narrow-angle glaucoma, or retinal detachment-no matter how scientifically justified the association.
Harry H. Mark, MD, is in private practice in New Haven, CT. He can be reached at 203/234-2212 or by e-mail at IIMD@aol.com
1. Crooke CP. Communication in ophthalmology. Trans Ophthalmol Soc UK. 1981;102:409-421.
2. Smith P. The pathology and treatment of glaucoma. London: J & A Churchill; 1891:122.
3. Mark HH. Myopia and glaucoma. Acta Ophthalmol Scand. 2002;80:230-231.
4. Mark HH, Robins KP, Mark TL. Axial length in applanation tonometry. J Cataract Refract Surg. 2002; 28:504-506.