There probably are studies, and someone here will point you to them.  
I'd say he is definitely at risk.  Did they measure his corneal
thickness (pachymetry)? If not, why not?  I mean it will define how
accurate the tonometry readings are, and I don't care what the
professions say, pressures are a factor in glaucoma.  It's good that his
optic nerves are good, but that should be documented photographically,
for a pixel by pixel comparison next year. Early detection is where it's
at, and the earlier the better. And no better way than digital
photography, in his case, STEREO photography.

w.stacy, o.d.