Epiretinal Membrane and Cystoid Macular Oedema Post-cataract Surgery

Cataract surgery is the most frequently performed surgery in the NHS. Cystoid macular oedema (CMO, inflammation and fluid accumulation in the central retina) is the most common visually significant complication following cataract surgery occurring in 1-2% of cases. Many cases resolve with topical anti-inflammatory eye drops. However some cases do not respond and require more invasive treatment modalities eg injections into the eye. If CMO remains persistent this can lead to permanent visual loss. There is little current knowledge on what factors lead to persistence in some cases compared to others. Epiretinal membrane (ERM, a fibrocellular membrane that can form on the inner retina) can be associated with a similar cystoid macular oedema that often does not resolve until the ERM is removed surgically. This study aims to look at whether the presence of an ERM affects how long it takes for cystoid macular oedema to resolve following cataract surgery and the requirement for non-topical treatment modalities.

A prospective, non-interventional, observational study design is proposed. Eligible participants would be identified at one of several participating NHS hospitals in the Wessex Deanery. Subjects with evidence of CMO post-cataract surgery and commenced on treatment would be included. Treatment choice is at the discretion of the reviewing clinician and independent of the study protocol. Investigations performed would be only those conducted as part of standard care. Presence of epiretinal membrane would be determined from review of the medical records. Case- records of eligible participants would be reviewed over a 12-month period to assess response to treatment and type of treatment(s) used. Based on current surgical data recruitment would be estimated to take 18 months to achieve the 165 eligible participants to achieve statistical power.

Inclusion criteria

• Male or Female, aged 18 years or above.
• Clinical diagnosis of visually significant pseudophakic CMO in ipsilateral eye within 12 weeks of cataract surgery.

• The clinical diagnosis needs to be made by an ophthalmologist of Grade ST3 or higher.
• Visually significant is defined as best recorded visual acuity 6/9 Snellen or worse (or LogMAR equivalent)
• An OCT has to have been undertaken and needs to show the presence of intra-retinal cysts and OCT thickness (central subfield CSF) outside normal parameters as defined by Grover et al [12] and Wolf-Schnurrbusch at al [13] (For clarity the OCT examination does not need to be undertaken on the same day as the clinical diagnosis of pseudophakic CMO. Any OCT examination undertaken after cataract surgery to the ipsilateral eye within the treatment period showing these characteristics will be acceptable to substantiate the clinical diagnosis of pseudophakic CMO.
• Started on treatment for cystoid macular oedema
• Participant is willing and able to give informed consent for participation in the study

Exclusion criteria

The participant may not enter the study if there is evidence that macular oedema may have been present pre-operatively. This will include ANY of the following:

• Evidence of pre-existing macular fluid/oedema
• Active proliferative diabetic retinopathy
• Diabetic macular oedema requiring treatment in the last 2 years
• Active uveitis at the time of cataract surgery
• Neovascular age-related macular degeneration
• Active retinal vein occlusion (branch or central) as evidenced by the presence of retinal haemorrhages at the time of cataract surgery or at time of diagnosis of CMO