Sometimes it's more the beard/muffs being the problem. High, fluffy "muffs" on sides of the head can really obscure vision bad especially if they rise to meet the bottom part of the crest. Some silkies have those puffs in front of crest that hang down.. those can obscure vision especially if combined with beard.
Mr Peeps might be good example of this- his crest isn't big at all so if he has a hard time seeing, it's the muffs part of the beard plus his comb seems to be pushing sideways and down some of the frontal part of crest.
With those cases all that's really necessary is to trim the muffs(beard trimming not necessary at all) down to the skin and trim off the "frontal puffs" and they can see much better.
Use as small scissors as you can find.. sewing scissors or personal toiletry scissors for fingernails/trimming eyebrows etc.
One solution to this would be breeding for bearded/crested birds with good separation of beard from the crest.