Effect of laser treatment for dry age related macular degeneration on foveolar choroidal haemodynamics

Abstract

Aim: Previous studies have suggested that laser photocoagulation therapy is associated with the resolution of drusen in some age related macular degeneration (AMD) patients. The main aim of the study was to determine whether low intensity laser treatment applied according to the Complications of AMD Prevention Trial (CAPT) protocol produces changes in the choroidal circulation that may help explain the mechanism leading to the resolution of drusen material.

Methods: This ancillary study included 30 CAPT patients with bilateral drusen that were treated and followed at the University of Pennsylvania. Laser Doppler flowmetry was used to measure relative choroidal blood velocity (Ch(vel)), volume (Ch(vol)), and flow (Ch(flow)) in the centre of the fovea. Measurements were obtained through a dilated pupil in both eyes of each patient at the initial CAPT visit before laser treatment was applied in one eye. Measurements were repeated in both eyes of each subject three months later. Analysis of laser Doppler measurements was performed in a masked fashion.

Results: In comparison to baseline, no significant differences in Ch(vel), Ch(vol), or Ch(flow) were observed three months following the application of low intensity laser according to the CAPT protocol in the untreated and treated eyes. In comparison to the untreated eyes, no significant differences were detected in the treated eyes. Based on the variability of flow measurements in the untreated eyes, the authors estimated an 85% power to detect a 15% change in relative blood flow.

Conclusions: The results suggest that large alterations in choroidal blood flow do not occur at three months after low intensity laser therapy following the CAPT protocol.

Figure 1

Choroidal blood velocity (Ch_vel) in arbitrary units at baseline and 3 months after laser photocoagulation in untreated and treated eyes. There is no significant change in relative Ch_vel in untreated and treated eyes (paired, two tailed Student’s t test; p = 0.5, p = 0.4, respectively).

Figure 2

Choroidal blood volume (Ch_vol) in arbitrary units at baseline and 3 months after laser photocoagulation in untreated and treated eyes. There is no significant change in relative Ch_vol in untreated and treated eyes (paired, two tailed Student’s t test; p = 1.0, p = 0.4, respectively).

Figure 3

Choroidal blood flow (Ch_flow) in arbitrary units (AU) at baseline and 3 months after laser photocoagulation in untreated and treated eyes. There is no significant change in relative Ch_flow in untreated and treated eyes (paired, two tailed Student’s t test; p = 0.8, p = 0.5, respectively).

Figure 4

For each subject, a comparison of the change in Ch_flow in arbitrary units at 3 months between the untreated and the treated eye. No significant difference in Ch_flow was observed between the untreated and treated eyes (paired, two tailed Student’s t test; p = 0.6).