Triterpenoid saponin-mediated recovery of visual deficits in age-related macular degeneration (AMD): Double-blind, placebo-controlled, randomised clinical trial

Purpose: Recovery rate of rod photoreceptor sensitivity (S2 gradient) following a bleach is reduced in age-related macular degeneration (AMD) due to diminished delivery of retinol across a grossly altered Bruch's membrane. Since triterpenoid saponins are known to improve transport across Bruch's, we have assessed their possible use for reversing the visual deficits in AMD.

Design: Double-blind, placebo controlled randomised clinical trial.

Methods: Altogether 11 AMD patients and seven age-matched control subjects were recruited to undertake a small proof-of-principle study. Dark adaptation curves were obtained and S2 gradients evaluated using a Humphrey Field Analyser. Following basal determination of S2 gradients, oral supplementation of saponins (200 mg/day) or placebo regime was instigated for a period of 4 months. S2 gradients were re-evaluated at two and four months.

Results: Basal S2 gradients of the AMD cohort were determined as 0.41 ± 0.24 dB/min and those of the control subjects as 1.44 ± 0.1 dB/min. After two months of the saponin treatment, AMD subjects showed improved S2 gradients of 0.92 ± 0.23 dB/min (P < 0.005) with a further increase to 1.35 ± 0.19 dB/min at four months (P < 0.01), the latter not being significantly different from control subjects. S2 gradients in placebo subjects were unaltered.

Conclusions: Oral supplementation with saponins results in reversing the reduced S2 gradients in AMD. This improvement in the transport properties of Bruch's is expected to slow, halt or reverse the progression of AMD.