Microcystic Macular Edema in Optic Neuropathy

Microcystic macular edema is a pattern of small cysts in the inner nuclear layer that appears in several optic neuropathies.

It does not leak on fluorescein angiography, so it differs from cystoid macular edema.

Recognizing it prevents unnecessary treatment and points toward an optic nerve cause.

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What Microcystic Macular Edema Looks Like

OCT shows small round or oval hyporeflective spaces in the inner nuclear layer, often in a ring around the fovea.

The inner retinal layers around the cysts are usually thin, because retinal ganglion cell loss has occurred.

The cysts do not enlarge like cystoid edema, and the fovea often looks normal (see cystoid macular edema).

Causes of Microcystic Macular Edema

• Multiple sclerosis and optic neuritis
• Neuromyelitis optica spectrum disorder
• Glaucoma and other chronic optic neuropathies
• Leber hereditary optic neuropathy and dominant optic atrophy

Gelfand and colleagues found that it is more frequent in multiple sclerosis patients with severe optic nerve disease.

Balk and colleagues noted that it also occurs in neuromyelitis optica and is not specific to that disease.

Mechanism of Microcystic Macular Edema

Abegg and colleagues proposed that it reflects retrograde degeneration after optic nerve damage.

Loss of ganglion cell axons may disturb Müller cells and fluid regulation in the inner nuclear layer.

Therefore, it signals damage to the afferent visual pathway, not leakage from vessels.

Differentiating From Other Macular Edema

Fluorescein angiography shows no leakage, and the cysts remain after anti-VEGF or steroid treatment.

Vascular edema usually shows a larger, central cystic pattern with thickening.

Check the optic disc, the visual fields, and the history to find the optic nerve cause (see demyelinating optic neuropathy).

Clinical Significance of Microcystic Macular Edema

The finding suggests more severe optic nerve damage, and it may reflect disease activity.

In multiple sclerosis, it correlates with worse visual function and with more brain atrophy in some studies.

It may also appear in eyes with long-standing glaucoma, where it signals advanced loss.

Management of Microcystic Macular Edema

Treat the underlying optic neuropathy, and avoid treating the cysts with injections.

Follow the cysts with OCT, since they may shrink or disappear over time.

Refer patients with unexplained optic neuropathy for neuro-ophthalmic evaluation.

An Example Case

A 34-year-old woman with multiple sclerosis and prior optic neuritis has reduced vision in her left eye.

OCT shows thin retinal nerve fibers and small cysts in the inner nuclear layer around the fovea.

Fluorescein angiography shows no leakage, so the team does not give injections.

Instead, her neurologist reviews her disease control, and the cysts remain stable on follow-up.

Questions Patients Ask

Patients ask whether the cysts cause the vision loss, and the answer is that they reflect optic nerve damage.

They also ask whether the cysts will go away, and some shrink while others stay.

Because the finding points to the optic nerve, explain that treatment aims at the underlying disease.

Pitfalls to Avoid

• Treating the cysts with anti-VEGF drugs or steroids
• Overlooking the optic disc, which may look pale
• Forgetting to ask about neurologic symptoms
• Assuming that normal acuity excludes optic neuropathy

Looking Ahead

Researchers study microcystic edema as a marker of disease activity in multiple sclerosis.

Also, OCT angiography may show changes in the capillaries near the cysts.

Therefore, the sign may help in monitoring and in trials.

Practical Points

Check the visual field, the color vision, and the pupils.

Then review the retinal nerve fiber layer thickness and the ganglion cell layer.

Also refer to a neuro-ophthalmologist when the cause is unclear.

Differential Diagnosis in Detail

Cystoid macular edema from vein occlusion, diabetes, or uveitis leaks on angiography.

Vitreomacular traction and retinoschisis can also create cystic spaces.

Because these conditions need different treatment, review the fluorescein images and the optic nerve.

Also consider X-linked retinoschisis in young males and nicotinic acid maculopathy with a spoke pattern.

Role of OCT Angiography

OCT angiography shows normal flow in the macular capillaries around the cysts.

Therefore, the cysts do not reflect vascular leakage.

Also, thinning of the ganglion cell layer supports an optic neuropathy.

Follow the thickness over time, because cysts may fade as the disease stabilizes.

Reporting the Finding

Describe the location, the extent, and the layer of the cysts in the report.

Then state that the angiogram showed no leakage when available.

Because clear language prevents unnecessary treatment, avoid the term cystoid edema for this pattern.

Also recommend neurologic evaluation when the cause is unknown.

For the latest studies, see the PubMed results for microcystic macular edema.

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References

1. Gelfand JM, Nolan R, Schwartz DM, et al. Microcystic macular oedema in multiple sclerosis is associated with disease severity. Brain. 2012;135:1786-1793.
2. Abegg M, Dysli M, Wolf S, et al. Microcystic macular edema: retrograde maculopathy caused by optic neuropathy. Ophthalmology. 2014;121:142-149.
3. Balk LJ, Killestein J, Polman CH, et al. Microcystic macular oedema confirmed, but not specific for neuromyelitis optica. Mult Scler. 2012;18:1766-1768.
4. American Academy of Ophthalmology. Basic and Clinical Science Course, Section 12: Retina and Vitreous. AAO; current edition.