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human malignant melanomas. Semin. Oneol. 2:83,1975.

Reply

Editor:Dr. Rodriguez-Sains brings up an in­

teresting point, one that was discussedeven further by Professor Alfred W. Kopfin the Parker Heath Memorial Lectureat the recent meeting of the Ameri­can Academy of Ophthalmology. Dr.Rodriguez-Sains points out that the pre­malignant (preinvasive) stage of manycutaneous melanomas lasts five to ten ormore years but, in addition, according tothe recent studies described by Dr.Kopf, long periods also elapse betweeninvasion of the superficial dermis, inva­sion of the deep dermis, and invasion ofthe subcutis; thus, just as changes in ourconception of uveal melanomas havetaken place during recent years, so alsoare we beginning to appreciate thatcutaneous malanomas are not as rapidlygrowing or as highly malignant as oncethought. By comparison, however, thereare still reasons for continuing to havegreater concern about cutaneous thanabout uveal melanomas: (1) mitotic activ­ity is typically much greater in cutaneousthan in uveal melanomas, (2) low-gradespindle cell melanomas are common inthe uvea but rare in the skin, and (3)metastatic disease is observed muchmore frequently at the time of initialmanifestation among patients with cuta­neous melanomas. Dr. Rodriguez-Sainshas focused attention mainly on the longperiod of time that elapses betweenseveral premalignant conditions and thetruly malignant, invasive stages of cuta­neous melanomas, and suggests thatperhaps there may be similar "growthpatterns" that precede the developmentof uveal melanomas. Uveal melanomasare more likely to arise in congenitalocular melanocytosis, in the nevus ofOta, in neurofibromatosis, and in large

nevi of the uveal tract than in completelynormal eyes; but to date, we are notaware of any significant variations inclinical behavior or metastasizing poten­tial that can be correlated with thesehistogenetically different types of uvealmelanomas.

LORENZ E. ZIMMERMAN, M. D.IAN W. McLEAN, M.D.

Washington, D.C.

Applanation TonometryWithout Fluorescein

Editor:I am writing to reply to the question

raised by Raymond Smith regardingapplanation tonometry without fluores­cein in the Correspondence section (Am.J. Ophthalmol. 87:583, 1979).

I wish to emphasize that applanationtonometry without fluorescein will resultin marked underestimation of the intra­ocular pressure. This occurs because oneis observing the edge of the meniscus ofthe tear film rather than the true edge ofthe applanation prism. As is pointed outin standard textbooks of ophthalmology,for the applanation principle to be cor­rect one must apply force to an area of3.06 mm! in size.

On a series of 100 consecutive eyes Iperformed applanation tonometry with­out fluorescein and then with fluoresceinand the blue exciting filter. In every casethe true intraocular pressure was under­estimated by a significant amount. Thepressure was lower by a range of 3 to 10mm Hg and this probably represents theamount of tearing the patient experi­enced after use of the topical anesthetic.

The use of fluorescein is important sothat serious errors in judgement will notbe made in the management of patientswith glaucoma.

MICHAEL B. RUMELT, M.D.Creve Coeur, Missouri