Well, cataract quite literally means there's a wall of water that exists in the length of our eye and that basically decreases the transparency of the lens and so we essentially become blind so we can't see very well. Now how does an increase in galactose actually lead to the building of a cataract? Well, inside the lens we essentially have cells and when the cells when there's an increase in the galactose concentration inside the cell the galactose begins to slowly convert into the galactitol as a result of the activity of the Aldos reductase. And so there's a build up in the concentration of this alcohol inside the cells of the lens and inside the lens itself. Now if there's a build up of this metabolite inside the cell that will create a hypertonic environment, an environment in which will essentially have a high concentration of solute molecules and that will cause the flow of water into the lens of the eye. And if water flows into the lens of the eye that is precisely what will cause a cataract to form because a cataract bites.