Cystoid macular edema

The central part of the retina is the macula. It is the part of the eye responsible for the central sharp and detailed vision. When fluid accumulates in the macular region, it forms cystic spaces which disrupt its normal function. The deeper retinal layers are mostly affected as photoreceptor cells cannot process light signals properly resulting in decreased quality of central vision. Patients with CMO experience blurry, wavy vision. Sometimes colours may appear altered as well.

Causes

There are several different reasons why an eye may develop CMO. The most important ones include:

• Diabetic retinopathy / maculopathy : long term uncontrolled diabetes may cause leaking blood vessels within the eye. These defective vessels contribute to the abnormal accumulation of excess fluid which results in impaired vision.
• Age Related Macular Degeneration : as a result of age related changes , leaking blood vessels (associated with wet ARMD) can lead to CMO
• Following cataract surgery : sometimes, CMO can happen after routine cataract surgery. An eye that underwent cataract surgery is called ‘pseudophakic eye’ because it has an artificial lens. In this case the condition is called ‘pseudophakic macular oedema’.
• Retinal Vein Occlusion : as a result of a blocked vein which causes blood stasis and impaired circulation.
• Intermediate Uveitis (inflammation in the eye) : long term inflammation within the eye can cause blood vessels to leak fluid resulting in CMO
• Some drops or drugs : latanoprost drops used for glaucoma have been associated with an increased risk of CMO and a group of drugs used for diabetes type II (thiazolididediones or glitazones)
• Rare ocular diseases : retinitis pigmentosa which is a rare disorder associated with loss of peripheral vision

Diagnosis

Diagnosis can be made with detailed ocular exam and use of special lenses to examine the retina and determine whether fluid is present in the macula. Optical coherence tomography (OCT) can help the clinician determine the extent of the fluid and make objective measurements. In some cases, fundus fluorescein angiogram (FFA) with use of a dye (fluorescein) is also helpful in making the diagnosis.

Treatment

Treatment depends on the underlying cause of the condition. Steroid and non steroidal anti inflammatory (NSAIDs) drops or steroid ocular injections may be necessary to treat CMO and improve vision. AntiVEGF injections can be used in cases of diabetic CMO or retinal  vein occlusion associated CMO. Discontinuation of drops or related drugs is also important (i.e latanoprost etc).