Did you know that Dorzolamide can effectively treat cystoid macular edema (CME) in certain inherited retinal conditions where the choroid and RPE (retinal pigment epithelium) deteriorate over time, such as retinitis pigmentosa, choroideremia, and enhanced S-cone syndrome?

What is the mechanism of action of Dorzolamide and how does it reduce CME in patients with retinitis pigmentosa and other inherited retinal diseases? Carbonic anhydrase, an enzyme present in the retina’s cones and RPE layers, plays a crucial role. In the RPE, it regulates the pH of the membrane and influences fluid transport. Dorzolamide, acting as a carbonic anhydrase inhibitor, affects the membrane-bound form of this enzyme in the RPE, leading to an “acidification” of the area. This, in turn, promotes the transport of fluid out of the RPE.

The picture below shows a RP patient who initially presented with bilateral CME and a VA of 20/30 OD and 20/40 OS. Treatment with Dorzolamide was initiated and at the 2 months follow up VA improved to 20/20 OD and 20/25 OS with almost total resolution of intra-retinal fluid. Top image is OD, bottom is OS.

 

At 2 month follow up

The study below reviews the benefits of Dorzolamide in patients with Retinitis pigmentosa.

Cystoid macular edema (CME) is a frequent complication of retinitis pigmentosa (RP), causing  reduced visual acuity, and subsequent changes in the fovea. The study assessed the clinical effectiveness of topical dorzolamide, a medication that inhibits carbonic anhydrase, in managing CME associated with RP.

The study enrolled 16 eyes from nine patients with CME secondary to RP. Baseline evaluation  measured visual acuity, visual field (HVF 10-2), and retinal thickness using optical coherence tomography (OCT). All participants were administered 1% dorzolamide to both eyes three times daily. Follow-up examinations occurred at 1, 3, and 6 months post-treatment. Macular sensitivity was calculated based on the average of 12 central points using HFA.

Results: 13 out of 16 eyes (81.3%) displayed a notable reduction in retinal thickness after treatment. The evaluation of macular sensitivity, calculated as the average of 12 central points (excluding foveal data), demonstrated an improvement of more than 1.0 dB in nine eyes (56.3%) out of 16. Furthermore, both the mean deviation value and macular sensitivity showed significant enhancement. No severe adverse effects were observed in any of the patients during the examination.

Conclusions: The findings of this study indicates that topical dorzolamide is an effective treatment for CME in RP patients, and these positive effects lasted for up to six months.

 

The above article was written based on the following study:

Grover S, Fishman GA, Fiscella RG, Adelman AE. Efficacy of dorzolamide hydrochloride in the management of chronic cystoid macular edema in patients with retinitis pigmentosa. Retina. 1997;17(3):222-31. doi: 10.1097/00006982-199705000-00009. PMID: 9196934.