Corneal microcysts

What are corneal microcysts? (Description)

These are tiny cystic vesicles present on the outer (epithelial) surface of the cornea. They can arise in a number of different conditions:

• Associated with certain types of contact lens.¹

• Associated with recurrent corneal erosion syndrome.²

• In the presence of vapours of certain industrial chemicals, eg aliphatic, alicyclic and heterocyclic amines.

• Associated with certain corneal dystrophies (epithelial basement membrane dystrophy (EBMD) or Cogan's microcystic corneal dystrophy and Meesmann's dystrophy).³

• They have been more recently associated with interferon therapy and exemestane.

• There are reports of corneal microcysts developing after belantamab-mafodotin treatment for relapsed or refractory multiple myeloma.⁴

• They may be found in pre-invasive carcinoma of the cornea.

How common are corneal microcysts? (Epidemiology)

This varies with the aetiology, the most common being microcysts associated with contact lens wear.

Presentation of corneal microcysts

Some may be asymptomatic. Others may cause ocular irritation or transient blurred vision and - if they rupture - cause painful corneal erosions which show up as punctate epithelial erosions (there will be scattered pinpoints of fluorescein uptake across the corneal surface).

Management of corneal microcysts³

This depends on the underlying cause but, generally, these patients are managed in an ophthalmology clinic. The source is removed where possible (such as in the case of contact lenses) and intensive lubrication with the aim to limit cyst formation and rupture is the mainstay of treatment.

If they persist and repeatedly rupture, they may be treated as would a case of recurrent corneal erosion syndrome, ie topical chloramphenicol, lubricants and - if there is no improvement - a period wearing a bandage contact lens (a soft lens with no refractive power that sits over the cornea and protects it from the shearing forces of the blinking lids). In severe cases, focal debridement may be required.

Complications of corneal microcysts

If they fail to heal adequately, the patient may go on to develop the self-perpetuating condition of recurrent corneal erosion syndrome, whereby there is an ongoing cycle of cyst formation and rupture as the epithelium does not have the time to heal fully.

Prognosis

This depends on the cause. Microcysts associated with wearing contact lenses should settle when the lenses are removed. Microcysts associated with corneal erosion syndrome, as are found in dry eye, should settle with intensive (and ongoing prophylactic) lubrication. Cysts arising as a result of industrial chemical vapour exposure settle over a few hours after vacation of the vapour, with no long-term sequelae. Corneal dystrophies are generally progressive disorders which worsen over time.

Prevention of corneal microcysts¹

Good patient education with regards to wearing contact lenses, and lubrication.