Ida Mann Classification for Retino-Choroidal Coloboma
The Ida Mann classification serves to categorize the size and severity of posterior segment colobomas, which directly correlates with visual prognosis and helps predict clinical outcomes 1.
Classification System and Clinical Significance
The Ida Mann (IM) classification stratifies chorioretinal colobomas into seven types based on the extent of the defect 1:
- Types 1-3: Large colobomas with extensive chorioretinal involvement
- Types 4-7: Moderate-to-small colobomas with more limited defects
Eyes with large colobomas (IM types 1-3) demonstrate significantly worse visual outcomes compared to those with smaller defects (IM types 4-7), both at initial presentation and at final examination 1. This size-based stratification provides critical prognostic information for counseling patients and families about expected visual function.
Prognostic Value
The classification system enables clinicians to:
- Predict visual outcomes: Larger IM classifications (types 1-3) correlate with worse best-corrected visual acuity throughout follow-up 1
- Identify high-risk patients: Children with CHARGE syndrome have 2.5 times increased odds of presenting with large colobomas (IM types 1-3) compared to isolated coloboma cases 1
- Assess bilaterality risk: CHARGE syndrome patients have 7-fold increased odds of bilateral fundus colobomas regardless of IM type 1
Structural Understanding for Complication Management
The classification helps contextualize the anatomical features critical for managing complications:
- Retinal detachment risk: Occurs in approximately 5% of eyes and 7.3% of patients with chorioretinal coloboma 1
- Margin anatomy: The transition from normal retina to the intercalary membrane (ICM) can be abrupt or gradual, with the inner neurosensory layers continuing as the ICM while outer layers terminate 2
- Break locations: Retinal breaks occur within the coloboma (27%), outside the coloboma (33%), both locations (13%), or remain unlocalized (27%) 3
Clinical Application
When evaluating a patient with chorioretinal coloboma, the IM classification guides:
- Initial visual prognosis counseling based on coloboma size 1
- Surveillance intensity for complications like retinal detachment and choroidal neovascularization (CNV), which occurs in 13.7% of eyes along coloboma margins 3
- Genetic syndrome screening, particularly for CHARGE syndrome in cases with large or bilateral colobomas 1
The classification remains relevant because both large and small colobomas result in visual impairment, though the degree differs significantly 1.