LETTERS TO THE JOURNAL Photographic Slides for Teaching Laser Photocoagulation Marc M. Whitacre, M.D. and Martin A. Mainster, M.D. Department of Ophthalmology, University of Kansas Medical Center. Inquiries to Marc M. Whitacre, M.D., Department of Ophthalmology, University of Kansas Medical Center, 39th ami Rainbow Blvd., Kansas City, KS 66103. One obstacle in teaching laser panretinal photocoagulation to residents is the lack of a simple model to duplicate the response of liv- ing retinal tissue to photocoagulation. An ordi- nary 35-mm color fundus slide provides a use- ful alternative. A 35-mm Ektachrome slide of a normal or diseased fundus is mounted on the slit lamp of an argon laser. A sheet of white paper or cardboard is mounted behind the slide at an oblique angle and an incandescent lamp direct- ed on this surface to provide retroillumination of the slide. This arrangement is illustrated in the Figure. The laser should be adjusted to produce a blue-green or green-only beam with a spot size of 500 u.m, an exposure time of 0.2 seconds, and a beam power of approximately 40 mW. This setting should produce a yellow discoloration in the slide similar to a grade II to grade III laser burn of the fundus. 1 The focus- ing and power setting of the laser are critical. Even a slight defocusing of the beam will re- duce the power density of the beam sufficiently to prevent any color change from occurring. Any inadvertent increase in power density, as might occur when the operator over-accom- modates and brings the laser beam into a tight- er focus than when the power was initially adjusted, will produce a clear bubble in the slide. This can be considered the equivalent of a perforation in Bruch's membrane with a cho- rioretinal hemorrhage. Kodak Ektachrome SE duplicating film has been tried and also gives satisfactory results. Kodachrome slides are not acceptable because the treated areas are yellow-brown in color and are difficult to distinguish from the background fundus. Regardless of the film, identical results are achieved when the front (protective) or back (acetate) surfaces of the slide are exposed. If mock panretinal photocoagulation is per- formed on a wide-angle fundus slide more than 1,000 burns can be applied, closely approximat- ing panretinal photocoagulation and providing ample operator practice. It is actually more difficult to produce consistent burns in the slides than it is in a human fundus. The prac- tice sessions are not constrained by the availa- bility of experimental animals, patients, or staff supervision. The response of the slides pro- vides immediate feedback of the operator's per- formance and is a permanent record document- ing his performance. We provide each resident with three stand- ardized slides late in the first year of their residency. The first slide is that of a normal fundus, so the residents can perform the photocoagulation free of the distractions of fundus pathology. The second slide is of pre- proliferative diabetic retinopathy, with cotton- wool spots and background hemorrhages. The third slide is one of proliferative diabetic reti- nopathy. The residents must demonstrate that they are capable of consistently placing burns of the correct intensity and spacing in regions of each of the slides that should be treated, and sparing those regions that should not be treat- THE JOURNAL welcomes letters that describe unusual clinical or pathologic findings, experimental results, and new instruments or techniques. The title and the names of all authors appear in the Table of Contents and are retrievable through the Index Medicus and other standard indexing services. Letters must not duplicate data previously published or submitted for publication. Each letter must be accompanied by a signed disclosure statement and copyright transfer agreement published in each issue of THE JOURNAL. Letters must be typewritten, double-spaced, on 8 1/2 x 11-inch bond paper with 1 1/2-inch margins on all four sides. (See Instructions to Authors.) They should not exceed 500 words of text. A maximum of two black-and-white figures may be used; they should be cropped to a width of 3 inches (one column). Color figures cannot be used. References should be limited to five. Letters may be referred to outside editorial referees for evaluation or may be reviewed by members of the Editorial Board. All letters are published promptly after acceptance. Authors do not receive galley proofs but if the editorial changes are extensive, the corrected typescript is submitted to them for approval. These instructions markedly limit the opportunity for an extended discussion or review. Therefore, THE JOURNAL does not publish correspondence concerning previously published letters. 590