Vascular Alterations in Choroid in Acute Macular Neuroretinopathy and PAMM

Overview

This study investigates choroidal vascular changes in acute macular neuroretinopathy (AMN) and paracentral acute middle maculopathy (PAMM) using OCT and AI-based analysis. Findings suggest distinct choroidal involvement in AMN compared to PAMM, with implications for understanding their ischemic pathophysiology.

Background

Acute macular neuroretinopathy (AMN) is a rare macular disorder characterized by acute photopsia and paracentral scotoma, primarily affecting young adults, especially females. Paracentral acute middle maculopathy (PAMM) is a separate clinical entity identified by OCT features involving the inner nuclear layer and associated with retinal vascular occlusions. Both conditions share ischemic origins but differ in the vascular layers affected. Recent advances in OCT angiography have highlighted the deep capillary plexus in PAMM and raised questions about choroidal involvement in AMN.

Data Highlights

The study included patients diagnosed with AMN and PAMM from two Italian ophthalmology centers. Subfoveal choroidal thickness (SFCT) and choroidal vascularity index (CVI) were measured using spectral-domain OCT and AI-based software. Measurements were taken during the acute phase and after resolution (≥3 months). The study excluded patients with other macular diseases, poor imaging quality, prior ocular surgeries (except cataract), and significant refractive errors. Healthy age-matched controls were also included for comparison.

Key Findings

• AMN patients showed increased subfoveal choroidal thickness and altered choroidal vascularity index during the acute phase compared to controls.
• These choroidal changes in AMN resolved after disease resolution, indicating transient choroidal involvement.
• PAMM patients exhibited no significant changes in choroidal thickness or vascularity, supporting a primary retinal vascular pathology.
• OCT angiography confirmed deep capillary plexus involvement in PAMM but suggested choroidal hypoperfusion as a key mechanism in AMN.
• The use of AI-based software improved accuracy and reproducibility of choroidal measurements.

Clinical Implications

Clinicians should consider choroidal vascular alterations when diagnosing and managing AMN, as these changes may be transient and reversible. Differentiating AMN from PAMM using OCT and choroidal metrics can guide prognosis and tailor monitoring strategies. Understanding the distinct vascular layers involved may influence therapeutic approaches targeting ischemic mechanisms.

Conclusion

This study supports the hypothesis that choroidal hypoperfusion plays a central role in AMN pathogenesis, contrasting with the retinal capillary involvement in PAMM. AI-assisted OCT analysis provides valuable insights into vascular alterations, enhancing diagnostic precision and understanding of these macular ischemic conditions.

References

1. Bos and Deutman 1975 -- First description of AMN
2. Hashimoto et al. -- Case report of bilateral AMN with choroidal changes
3. von der Burchard et al. -- Perfusion deficit in choroid in AMN
4. OCT angiography studies -- DCP involvement in PAMM
5. AI-based software validation for choroidal measurements