Table 1 Grading scheme for IRMA morphology

4

Regression of IRMA

IRMA branches become incorporated into the surrounding capillary bed and convoluted IRMA branches assume a more normal branching pattern.

This improvement may be partial (Fig. 1a,e) or nearly total (Fig. 1c, g) and is associated with improvement in perfusion of surrounding area.

3

Stable IRMA

IRMA remains relatively unchanged, with the same number of branches.

Vessel caliber and surrounding area of non-perfusion remain constant

(Fig. 2e, Fk).

2

Progression of IRMA

Increase in IRMA vascular branching (Fig. 2b, h), and/or appearance of newly formed IRMA (Fig. 2a, g).

Associated with enlargement of the surrounding region of non-perfusion with loss of previously visualized capillary bed.

1

Obliteration of IRMA

Disappearance of IRMA with progression of capillary non-perfusion.

End-stage progression with nearly total or complete disappearance of IRMA (IRMA drop-out) (Fig. 2c, i) and advancement of surrounding capillary drop-out.