treatment plan

Tamoxifen Maculopathy

BY BRUCE E. ONOFREY, RPH, OD
MARCH 1999

A recent study concluded that the use of Tamoxifen could reduce the incidence of breast cancer by as much as 45 percent. But what's the significance to the average primary optometric physician? Plenty!  The following case will illustrate the importance of this new group of patients at risk.

As I scanned Mrs. J's chart prior to her annual exam, I noticed the words "decreased vision." The patient had been examined one year earlier with a best corrected acuity of 20/25 OU. Today, with corrective lenses, her acuity had dropped to 20/60 OD and 20/40 OS. The results of my examination are as follows: BVA: 20/50 OD, 20/40 OS; Med Hx: Hypertension, Breast cancer/mastectomy five years ago; Meds: Vasotec, Tamoxifen; Allergies: Penicillin; Family Hx: Neg; slit lamp exam: Unremarkable; Pupils: 5mm, (+) 3 Rx, Rd, (-) afferent defect; IOPs: 16mm OU; DFE: C/D .3/.3 A/V 2/3; Macula: Scattered white deposits posterior pole OU; Lenses (+) 1 nuclear sclerosis OU; and Periphery: PVD OS with flat retina 360 degrees OU.

How do I explain this 68-year-old woman's dramatic decrease in acuity? It's not a cataract -- there was no change in refraction. Age-related macular degeneration wouldn't be consistent with the macular changes I observed. There has been an increase in the incidence of Tamoxifen-related maculopathy in the literature. The reason for this is that Tamoxifen, which is used for the postsurgical treatment of breast cancer, has been administered for longer periods of time to women suffering from this disorder.

Macular Degeneration

Most inaccurate diagnoses label Tamoxifen maculopathy as either age-related macular degeneration, cystoid macular edema or occasionally, diabetic maculopathy. The retinal changes clinically appear as bilateral, superficial yellow-white crystalline ring-like deposits. Fluorescein angiography occasionally reveals macular edema and hyperflourescence.

Nicholas Pavlidis, Christis Petris and Evagellos Briassoulis, et al. reported a study of 63 patients in Cancer Treatment Report (June 1992) on how retinal toxicity with Tamoxifen had occurred in approximately six percent of patients who had used moderately low doses of the drug. The paper reported on patients using only 20mg of the drug per day. The earliest report of toxicity occurred after only 10 months of therapy in these individuals. The patients total cumulative dose had been only six grams of drug. Visual acuity dropped to the 20/25 level with complete recovery after discontinuation of therapy.

Mechanism

The mechanism of Tamoxifen-induced retinal damage is not clearly understood, but has been postulated to be a result of the drug depositing in the retinal pigment epithelium (RPE). Here, Tamoxifen interferes with the normal metabolism of the RPE and the photoreceptors that are dependent upon the RPE for metabolic support. Tamoxifen shares a structural similarity to other drugs, like amiodarone and chlorpromazine in that they possess both hydrophilic and lipophilic groups. Compounds with this structure have a propensity for binding to various ocular tissues.

Evaluate patients undergoing therapy with Tamoxifen prior to treatment and regularly during treatment for signs of ocular toxicity. Be sure to perform the following tests during evaluations: BVA, threshold visual fields,
color vision and amsler grid. In consultation with the patient and their oncologist, consider discontinuing Tamoxifen therapy in
individuals who exhibit early macular changes or reduced visual function. CLS

Dr. Onofrey, editor and author of various ophthalmic texts, practices in Albuquerque, New Mexico.