Rhegmatogenous Retinal Detachment After Initiation of Ocusert Therapy

LETTERS TO THE JOURNAL tive error was -1.25 sph. in the right eye and -3.00 sph. in the left eye. Axial lengths were 24.0 mm in the right eye and 24.5 mm in the left eye. Indirect ophthalmoscopy without scleral depression disclosed typical lattice degeneration in both eyes without retinal breaks. Therapy was begun with Ocusert Pilo-ZO, changed every five days in each eye. The patient was seen four weeks later at which time he was again asymptomatic. Repeat examination by indirect ophthalmoscopy disclosed an inferotemporal retinal detachment in the left eye extending posterior to the equator but not to the vascular arcades. The causative break was a round hole in a lattice lesion. Retinal detachments can be considered to be potentially miotic-induced if the duration of miotic use before development of the detachment is not greater than two months.' All types of miotic eyedrops have been incriminated in this process, but many believe the stronger miotics are more likely to cause retinal detachments." Animal studies have demonstrated that administration of Ocusert results in constant low levels of pilocarpine in the ciliary body and iris, whereas in order to attain the same trough tissue levels with eye drop therapy, a peak tissue level three to five times as great is required (Ocusert, package insert). We found another published report of a retinal detachment that was discovered after the initiation of Ocusert therapy." The patient had been treated with other miotics previously and no fundus examination was performed before switching treatment to Ocusert therapy, thus casting doubt on the relationship between the

Rhegmatogenous Retinal Detachment After Initiation of Ocusert Therapy Peter Weseley, M.D., Jeffrey Liebmann, M.D., and Robert Ritch, M.D. Department of Ophthalmology, New York Eye and Ear Infirmary. Supported by the Glaucoma Foundation, New York, New York.

Inquiries to RobertRitch, M.D., Glaucoma Service, New York Eye and Ear Infirmary, 310 E. 14th Si., New York, NY 10003.

Although the existence of a causal relationship between miotic use and retinal detachment has never been unequivocally proven or universally agreed upon, there is strong anecdotal evidence to suggest such a relationship. r-s A recent survey of general ophthalmologists, retina specialists, and glaucoma specialists demonstrated that a majority of all three groups believes such a relationship does exist." It has been suggested that if miotic use is essential, "the weakest effective miotic agent, including Ocusert pilocarpine where feasible, is preferred."2 We recently encountered a patient who developed retinal detachment shortly after initiating therapy with Ocusert pilocarpine. A 36-year-old, phakic man with pigmentary glaucoma was referred for treatment of uncontrolled intraocular pressure. There was no family history of retinal detachment and he denied any visual symptoms. Previous antiglaucoma therapy consisted of timolol maleate only. He had never been treated with miotics. His refrac-

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 81/2 x H-Inch bond paper with Ilj2-inch margins on all four sides. (See Instructions to Authors.) An original and two copies of the typescript and figures must be sent. The letters should not exceed 500 words of text. A maximum of two black-and-white figures may be used; they should be cropped or reducible 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. 458

Letters to The Journal

Vol. 112, No.4

two events. Interestingly, that patient also had pigmentary glaucoma. The mechanism of miotic-induced retinal detachment has never been elucidated. There has been some controversy as to whether miotics cause new retinal breaks through anterior movement of the ciliary body or increased vitreoretinal traction, or if miotics induce retinal detachment in eyes that have pre-existing breaks." While no breaks were seen when our patient was first examined, because the causative break was an atrophic hole and not a tractional break supports the view that the abnormality was present at the time of initial examination and was not found because scleral depression was not performed. However, this cannot be proven. It has been reported that miotic treatment can induce a new retinal break after careful retinal examinations failed to find any abnormality before the institution of treatmerit.' Well-known risk factors for the development of retinal detachment in our patient include myopia and lattice degeneration. The increased risk of retinal detachment in patients with pigmentary glaucoma and the pigment dispersion syndrome is not as widely appreciated, and appears to occur with equal frequency in patients using and not using miotics." The need for careful examination of the peripheral fundus in patients with any of these risk factors before the initiation of miotic therapy cannot be overemphasized. Inasmuch as our patient developed a retinal detachment after starting Ocusert therapy in the absence of a peripheral fundus lesion that would be treated by most retinal surgeons, we recommend that careful fundus examinations be repeated shortly after the initiation of therapy, regardless of the strength of the prescribed miotic agent.

References 1. Pape, L. G., and Forbes, M.: Retinal detachment and miotic therapy. Am. J. Ophthalmol. 85:558, 1978.

2. Ackerman, A. L.: Retinal detachments and miotic therapy. In Pruett, R. L., and Regan, C. D. J. (eds.): Retina Congress. New York, Appleton-Century-Crofts, 1972, pp. 533-539. 3. Krausbar, M. F., and Steinberg, J. A.: Miotics and retinal detachment. Upgrading the community standard. Surv. Ophthalmol. 35:311, 1991. 4. Puustjarvi, T.: Retinal detachment during glaucoma therapy. Ophthalmologica 190:40, 1985.

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5. Scheie, H. G., and Cameron, J. D.: Pigment dispersion syndrome. A clinical study. Br. J. Ophthalmol. 65:264, 1981.

Mixing Fortified Antibiotic Eyedrops Robert J. Schechter, M.D.

The Jules Stein Institute, Department of Ophthalmology, UCLA School of Medicine. Inquiries to Robert J. Schechter, M.D., 1515 N. Vermont Ave., Los Angeles, CA 90027. A recent article on the stability of custommade fortified antibiotic eyedrops' illustrates several problems with this therapy. Usually these mixtures are made without the addition of any stabilizers or preservatives. Often, the pharmacist will be unsure of just what diluent in which to add the intravenous antibiotic in order to obtain the desired final concentration. Additionally, it may be desirable to be able to vary the antibiotic concentration to the clinical situation because increasing toxicities are observed with increasing concentrations." As pharmacists spend more of their time dispensing prepackaged medications, the potential problems in having them mix special formulas increase. Another potential problem, often not considered, is in the choice of an appropriate container in which to dispense a preparation intended for topical, ocular application. For fortified gentamicin (or tobramycin) eyedrops, all these problems can be resolved by specifying a distinct recipe to the pharmacist. Simply adding the intravenous antibiotic to the commercially available eyedrop has advantages. First, the mixture already coritains stabilizers and preservatives known to be compatible with and appropriate for the antibiotic. Second, the mixture will be given to the patient in a container specifically designed to store and dispense eyedrops. The calculations are straightforward. Gentamicin is available as a commercial eyedrop as 5 ml in a concentration of 3 mgjml. Thus, the mixture contains 15 mg. Intravenous gentamicin is available in a concentration of 40 mgjml. Thus, adding 1 ml of the intravenous mixture to the bottle results in 55 mg in 6 ml or 11.5 mgjml. Adding 2 ml results in 95 mg in 7 ml or 13.6 mgjml. Adding 2.5 ml results in 115 mg in 7.5 ml or 15.3 mgjml. Specifying the composition of the fortified antibiotic eyedrops in this manner has several