How does Exogenous ROS Effect LHON Conversion

"Mitochondrial DNA mutations associated with Leber's hereditary optic neuropathy (LHON) are associated with endogenous reactive oxygen species (ROS) production. Research has demonstrated that exogenous ROS generators, like smoking, are associated with an earlier age of conversion from carrier to affected state. However, the exact role of exogenous ROS in LHON is ill defined. To understand the role of exogenous ROS in LHON, we hypothesize dividing LHON into two subtypes. I: conversion is predominantly genetically determined and largely independent of exogenous ROS and II: the genetic component is necessary but insufficient for conversion and exogenous ROS exposure is required."