# Changes in Choriocapillaris Flow Deficits Before and After the Onset of Large Choroidal Hypertransmission Defects in AMD

## TL;DR

This study found that blood flow loss in the choriocapillaris does not occur before the formation of large choroidal defects in age-related macular degeneration, but may contribute to their growth.

## Contribution

The study is the first to show that choriocapillaris flow deficits occur after, not before, the formation of large choroidal hypertransmission defects in AMD.

## Key findings

- No significant choriocapillaris flow deficits were observed before the onset of large hyperTDs.
- A significant increase in flow deficits was detected after the formation of hyperTDs.
- Only two out of 27 targets showed marked increases in flow deficits after hyperTD formation.

## Abstract

Eyes with intermediate age-related macular degeneration (iAMD) underwent swept-source optical coherence tomography angiography (SS-OCTA) imaging and were evaluated longitudinally to determine if choriocapillaris flow deficits (CCFDs) developed before or after the formation of large choroidal hypertransmission defects (hyperTDs).

A retrospective review was performed of prospectively collected 6 × 6-mm SS-OCTA images from eyes with iAMD that developed large hyperTDs, defined on en face images from subretinal pigment epithelium (sub-RPE) slabs positioned 64 to 400 µm beneath Bruch's membrane (BM) as bright lesions with a greatest linear dimension (GLD) ≥ 250 µm. The onset of large hyperTDs was designated as baseline T = 0; additional visits were chosen at 1 year before and at two 1-year intervals after T = 0. A grid box strategy was implemented for the analysis of CCFDs at the site where hyperTDs formed. A change in the percentage of CCFDs greater than 5% was considered to be a true change outside the repeatability limits.

Twenty-seven targets from 27 eyes eligible for final analysis were followed over four visits separated by 12 ± 3 months. No targets showed a marked CCFD change above 5% prior to hyperTD onset. Only two targets showed marked increases in CCFDs after hyperTD formation. A grouped analysis of all targets showed no mean CCFD change prior to hyperTD onset, but a significant change only after the onset of hyperTD.

CCFD values did not increase prior to the onset of hyperTDs with increases in CCFDs detected after their onset. These results suggest that loss of choriocapillaris perfusion did not precede hyperTD formation but may play a role in hyperTD growth.