cRORA (Retinal Atrophy on OCT): Criteria Explained

cRORA, or complete retinal pigment epithelial and outer retinal atrophy, is a consensus OCT term for established atrophy.

The Classification of Atrophy Meetings (CAM) group introduced it to standardize atrophy grading in AMD.

In addition, CAM named earlier stages that color photographs may miss.

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What cRORA Means on OCT

The term describes combined loss of the RPE and overlying photoreceptors.

Because the healthy RPE blocks much of the OCT beam, its loss brightens the signal beneath it.

The examiner therefore sees a bright choroidal band under a thinned outer retina.

However, the label describes anatomy and does not establish the cause.

The Four cRORA Criteria

CAM Report 3 requires all of the following features:

• Choroidal hypertransmission at least 250 microns wide
• RPE attenuation or disruption at least 250 microns wide
• Overlying photoreceptor degeneration, such as outer nuclear layer thinning, external limiting membrane loss, or ellipsoid zone loss
• No scrolled RPE or other sign of an RPE tear

Why 250 Microns?

The threshold is a consensus size that graders can apply on B-scans.

Therefore, treat it as a grading boundary, since biology does not change abruptly at that width.

Borderline lesions may also fall on either side between visits because of scan differences.

Reading Hypertransmission in cRORA

First, look below Bruch’s membrane for a continuous bright band.

Next, confirm that the RPE above it is attenuated or disrupted.

Media opacity and poor scan quality can weaken this signal.

A sub-RPE slab on en face OCT can also help map the lesion borders.

iRORA: The Intermediate Stage

Incomplete RPE and outer retinal atrophy (iRORA) shows hypertransmission, RPE disruption and photoreceptor degeneration.

However, these changes do not meet the full cRORA criteria.

CAM Report 4 lists supporting signs, including subsidence of the inner nuclear and outer plexiform layers.

A hyporeflective wedge within the Henle fiber layer also supports the diagnosis.

cRORA Versus Geographic Atrophy

The two terms overlap, yet they come from different imaging traditions.

Geographic atrophy began as a color photograph description (see geographic atrophy).

Fundus autofluorescence often shows these areas as sharply dark, which complements the OCT findings.

Nascent Geographic Atrophy

Wu and colleagues described subsidence and a hyporeflective wedge before drusen-associated atrophy appeared.

They called this appearance nascent geographic atrophy.

Therefore, check which definition a paper uses before comparing progression rates.

Applying cRORA in AMD Follow-Up

Dense volume scans reduce the risk of missing small lesions between B-scans.

Also, use registered follow-up so that you compare the same retinal location at each visit.

Then record the largest lesion width, the number of lesions, and foveal involvement.

Finally, comment on neovascular signs, because they change both terminology and treatment.

Foveal Sparing and Symptoms

Visual acuity can remain good when atrophy spares the fovea.

Nevertheless, patients may report reading difficulty, paracentral scotomas, or trouble in dim light.

For that reason, stable acuity does not prove stable disease.

cRORA in Neovascular AMD

However, fluid, fibrosis and pigment epithelial detachment can obscure the RPE and choroidal signal.

Therefore, judge exudative activity separately from atrophy.

As a result, atrophy alone should not end anti-VEGF treatment when active exudation persists.

Conditions That Mimic cRORA

Hypertransmission with outer retinal loss occurs outside AMD, so patient age and fundus pattern still matter.

• RPE tear, which shows scrolled RPE beside a bare area
• Stargardt disease and other inherited macular dystrophies
• Myopic chorioretinal atrophy
• Hydroxychloroquine toxicity
• Atrophy after laser or chronic central serous chorioretinopathy

Treatment Decisions and cRORA

Pegcetacoplan and avacincaptad pegol inhibit parts of the complement pathway.

Phase 3 trials showed slower geographic atrophy growth, which is an anatomical benefit.

However, neither drug restores lost tissue, and the trials did not show clear visual improvement.

Risks include injection complications, intraocular inflammation and new neovascular AMD.

Moreover, trial eligibility relied on specific lesion criteria, so a cRORA label alone does not establish candidacy.

No treatment has proven benefit for iRORA, so observation is the usual approach.

Counseling Patients About cRORA

Patients rarely need the acronym, so explain that some retinal support cells and light-sensing cells have been lost.

Then describe where the area lies relative to central vision.

Advise prompt review for new distortion or sudden vision loss, because neovascularization may develop.

When discussing injections, explain that the goal is slower growth, and vision is unlikely to improve.

Pitfalls to Avoid

• Do not diagnose cRORA from hypertransmission alone
• Never call a scrolled RPE defect atrophy
• Do not assume every lesion is due to AMD
• Do not compare visits without registered scans

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References

1. Sadda SR, Guymer R, Holz FG, et al. Consensus definition for atrophy associated with age-related macular degeneration on OCT: Classification of Atrophy report 3. Ophthalmology. 2018;125:537-548.
2. Guymer RH, Rosenfeld PJ, Curcio CA, et al. Incomplete retinal pigment epithelial and outer retinal atrophy in age-related macular degeneration: Classification of Atrophy Meeting report 4. Ophthalmology. 2020;127:394-409.
3. Wu Z, Luu CD, Ayton LN, et al. Optical coherence tomography-defined changes preceding the development of drusen-associated atrophy in age-related macular degeneration. Ophthalmology. 2014;121:2415-2422.
4. Heier JS, Lad EM, Holz FG, et al. Pegcetacoplan for the treatment of geographic atrophy secondary to age-related macular degeneration (OAKS and DERBY). Lancet. 2023;402:1434-1448.
5. Jaffe GJ, Westby K, Csaky KG, et al. C5 inhibitor avacincaptad pegol for geographic atrophy due to age-related macular degeneration. Ophthalmology. 2021;128:576-586.