ACUTE MYOPIA DUE TO TOPIRAMATE TREATMENT – CASE REPORT AND REVIEW OF THE LITERATURE

The purpose of this communication is to make a review of the literature about two of the possible ocular effects of topiramate: acute myopia and angle closure glaucoma (ACG). We will do it from a case seen in our hospital. 

Topiramate is a sulfamate-substituted monosaccharide used as anticonvulsivant and migraine prophylaxis. Many adverse effects have been described due to this drug; however, we will focus in two of them: acute myopia and ACG. Both are thought to have the same pathogenesis. The underlying mechanism is a ciliochoroidal effusion, which causes a ciliar body edema, resulting in the zonular fibers relaxation and lens thickening, which explains an acute myopia. This leads to an anterior prolapse of the lens which results in an occlusion of the acuous humor drainage, causing an ACG.

A case from our urgencies was selected. This presents a 23-year-old woman who claimed binocular vision loss in the last 24 hours. She referred far vision loss, but normal close vision. She related it to a change in her anxiety and migraine medication: topiramate. She changed from 25mg to 50mg a day. No other symptoms were referred. A general ophthalmologic exploration was made, which included: visual acuity (VA), intraocular pression (IOP), autorefractometer, intraocular and extraocular movements, cover test, biomicroscopic, funduscopy and OCT.

 

The VA was R 0,03 / 0,1 and L finger counting 1m / 0,2. IOP was 21mmHg in both eyes. AR showed -5,75 and -4 diopters (dp) in the right (R) and left (L) eye respectively before cycloplegic and R -5dp and L -4dp after cycloplegic. Extraocular movements were normal, except for refixation movements in the lateral eye movements. The anterior OCT showed narrowed angles in both eyes. The rest of the exploration, including funduscopy, showed no alterations. Therefore, topiramate induced myopia was diagnosed, and topiramate was suspended.

One week later, VA was 1 in both eyes. IOP was 15/17mmHg. AR showed -0,25 R and +0,5dp L. In the OCT wider angles were shown in both eyes.

Acute myopia is a well-known adverse effect of topiramate. It usually resolves after abandoning topiramate treatment. This case highlights the importance of a good clinical history and broadens the possible causes of vision loss. This could apply to ACG; even though this patient didn't suffer it, IOP elevation and iridocorneal angle narrowing were noted.