Intravitreal Ranibizumab (Lucentis®) in the Treatment of Non-leaking Macular Cysts in Retinal Dystrophy

The treatment of cystoid macular edema (CME) in retinitis pigmentosa (RP) is well established in medical literature. These treatments include topical and oral carbonic anhydrase inhibitors (CAI), intravitreal triamcinolone acetonide, and laser photocoagulation. Oral acetazolamide, a carbonic anhydrase inhibitor (CAI), was found to be effective in the treatment of RP related CME with improvement in both visual acuity and fundus fluorescein angiography (FFA). However, some patients may not benefit from the treatment, or do not tolerate it, while others may develop rebound CME with prolonged use of at least 8 to 12 weeks.

An emerging treatment modality for CME in RP is the use of intravitreal injections of anti-vascular endothelial growth factors (anti-VEGF) such as bevacizumab (Avastin®) and ranibizumab (Lucentis®). Anti-VEGF has been used successfully for treating diabetic macular edema, and macular edema secondary to retinal vein occlusion and choroidal neovascularization, with limited side effects.

A subset of patients with retinal dystrophy develop non-leaking macular cysts that can be confused with CME on ophthalmoscopy and optical coherence tomography (OCT). FFA establishes the cavitary nature of the maculopathy, with no hyperfluorescence seen on angiography compared with leakage seen in patients with CME and retinal dystrophy.

CAI may promote resolution of the non-leaking macular cysts. There are limited studies that explore the effect of anti-VEGF specifically on non-leaking macular cysts in retinal dystrophies.

Aims:

• Assess the efficacy of intravitreal ranibizumab (IVR) injection in the treatment of non-leaking macular cystic lesions in patients with retinal dystrophy that have not responded to therapy with oral or topical CAI.

Objectives:

• Delineate the entity of non-leaking macular cysts by OCT and FFA.
• Assess the efficacy of short-term oral and topical CAI treatment on non-leaking macular cysts in retinal dystrophies.
• Study the visual response and structural resolution of non-leaking macular cysts in response to IVR.

Design: Two-phase prospective, non-randomized, open-label, comparative interventional, clinical trial.

Inclusion criteria:

1. Omani patients over 18 years old
2. Retinal dystrophy and non-leaking macular cysts confirmed by fundus examination, electroretinography (ERG), OCT, FFA and genetic testing.
3. Capacity and cooperation to undergo visual function assessment (i.e. best-corrected visual acuity (BCVA), as well as the above-mentioned investigations.
4. Written, informed consent to participate in the study

Exclusion Criteria:

1. Patients with pseudo-RP
2. Patients with cystic macular lesions or progressive retinal disease due to any cause other than retinal dystrophy
3. Patients with reduced visual acuity due to media opacities (e.g. cataract).
4. Patients with any contraindication or known allergy to CAI or anti-VEGF agents
5. Patients who have undergone vitreo-retinal surgery or intravitreal injection.

Methods:

Phase 1: Patients with best corrected visual acuity (BCVA) < 0.5 will receive carbonic anhydrase inhibitors (CAI) [oral acetazolamide 500mg/day or topical brinzolamide twice daily] and followed up for three months. Baseline urea and electrolyte (U\&E) will be tested prior to receiving CAI, and monitored every month while on the treatment. Upon completion of the treatment course, the patients will be assessed for response with visual function assessment and central macular thickness (CMT) on OCT. Patients who show an adequate response (defined as > 10% reduction of CMT) and/or improvement of BCVA by two lines or more) will continue in the CAI arm.

Phase 2: Patients who do not show an adequate response with CAI or develop significant side effects from CAI treatment will stop receiving CAI and will move to Phase 2 of the study and receive three 0.5mg IVR injection at monthly intervals. Upon completion of the treatment course, the patients will be assessed for response with visual function assessment and CMT on OCT.

The purpose of the proposed procedures/treatment, as well as potential complications, will be clearly explained to participants. It will be made clear to the patient that IVR treatment is experimental and may or may not lead to improvement of vision. The patient will also be informed that the treatment will be withheld in case of allergy or complications. It will be emphasized that he/she may withdraw from the study at any stage.

Patients will be under regular and close follow-up. They will be monitored for the development of any complications during the study. Any complication will be logged and treated appropriately. Patients' personal information, clinical history, examination, investigation results and progress with treatment, will be treated confidentially.

Institutional research ethics board approval will be obtained prior to the start of the study.