Stellate iron Lines in the Corneal Epithelium After Radial Keratotomy

Stellate iron Lines in the Corneal Epithelium After Radial Keratotomy

Vol. 99, No.2 _ _ _ _ _ _ _ Reply 219 Correspondence _ EDITOR: The argon laser treatment protocol recommended a 100-lJ.m spot size at 0.1 second...

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Vol. 99, No.2

_ _ _ _ _ _ _ Reply

219

Correspondence

_

EDITOR:

The argon laser treatment protocol recommended a 100-lJ.m spot size at 0.1 second with a power to produce a "medium" white burn at the level of the retinal pigment epithelium, in a random "grid" pattern, with spacing about one burn-width apart. Further details and modifications of treatment depend upon a great number of varying factors, such as the degree of retinal thickening from edema, the location of collaterals, and the location of flecks of residual iritraretinal hemorrhage, ali of which may require individual modifications of the treatment protocol. The treatment technique is not simple; indeed, it was with some effort that we explained the protocol at our Academy exhibit, at Academy instruction courses, and at various other continuing medical education laser courses during the past several months. Because of the variation in protocol that may be required by particular circumstances in the region of the edema, the treatment protocol expressly required that all treatments be performed by senior staff retinal specialists at the eye centers participating in the study. Visual field testing was performed before and after laser photocoagulation with the Goldmann perimeter using an 1-2 and III-4 test object. With this technique, it was our clinical impression that no significant difference existed between controls and treated patients. The "grid" pattern was applied throughout the region of leaking capillary abnormality within the retinal area drained by the occluded vein and could be applied as close to the fovea as the margin of the capillary free zone and asperipheral as the major vascular arcade (about 2.5 disk diameters from the center of the fovea), with the treatment location determined with simultaneous careful observation of a projected fluorescein angiogram of high quality. Because a single branch vein occlusion involves either the superior or inferior branch and never involves the entire posterior pole, the entire posterior pole was never treated. A reading test performed on a small sample of patients did not show that treatment worsened reading vision over that of branch vein occlusion controls (untreated) with the same final level of visual acuity.' Treatment in the papillomacular bundle was not prohibited in the protocol. However, the nature of most branch vein occlusions is such that most of the leaking abnormalities are outside the central papillomacular bundle; additionally, the laser absorption is estimated to be at the retinal pigment epithelial level and would not be expected to damage ganglion cells or their axons. There was no apparent decrease in visual acuity from those treat-

ments that included part of the papillomacular bundle. the mechanism for improvement of visual acuity by this type of laser treatment for certain cases of macular edema produced by branch vein occlusion is unknown. Our study does not address forms of macular edema other than that produced by branch vein occlusions that meet the eligibility criteria of this study. In particular the Early Treatment Diabetic Retinopathy Study sponsored by the National Eye Institute is investigating the management of diabetic macular edema in a study ongoing at this time. THE BRANCH VEIN OCCLUSIONSTUDY GROUP

Reference 1. Quillen, B., Walonker, A. F., and Diddie, K. R.: Functional vision assessment in macular disease. ARVO Abstracts. Supplement to Invest. OphthalmoI. Vis. Sci. Philadelphia, J. B. Lippincott, 1983, p. 53.

Stellate

iron Lines In the Corneal Epithelium After Radial Keratotomy

EDITOR:

The excellent article, "Stellate iron lines in the corneal epithelium after radial keratotomy" (Am. ]. Ophthalmol. 98:416, October 1984), by E. B. Steinberg, L. A. Wilson, G. O. Waririg III, M. J. Lynn, and W. H. Coles, provided a comprehensive review of all types of corneal iron lines. I had made this Observation as an independent observer when analyzing the patients of Albert Neumann, and showed a slide of the iron line at the Keratorefractive Society Symposium in 1981. This information was later published.P I was surprised that neither of these articles were referenced in this comprehensive review. ROBERT H. OSHER, M.D.

Cincinnati, Ohio

References 1. Neumann, A. c., Osher, R. H., and Fenzl, R. E.: Radial keratotomy. A clinical and statistical analysis. Cornea 2:47, 1983. 2. - - : Radial keratotomy. A comprehensive evaluation. Doc. OphthalmoI. 56:275, 1-984.