This is a great question!
I feel I may be able to answer this to an extent.
My psychedelic partner and I fit the description, he the 20 20 vision and me the poorer 14 14 vision. I feel it vital to mention that he is an advanced musician (plays drums, guitar, bass, synth, keys, flute, vocals), so there is something to account for in his information processing speed, sound and visual. I am too a musician although less advanced (flute, drums and vocals, minimum bass). He reports to have perfect, clear vision, can see far and near, with great acuity and color. I, on the other hand cannot see far ahead of me, I can see fine with out my glasses while reading and within 10 feet, but other than that it's all blurry for me.
From my experience, my close eyed visuals have been anywhere from super potent (dmt oriented while on mushrooms) to simple bursts out of a black background. I should also note that while on psilocin, after the coming up period (before I step out of my womb of a blanket and adventure outside to discover nature's secrets) I greet the outside world with noticeably different color vision, it is extremely enhanced, I seem to believe its a permanent effect, open-eyed.
Most of my experiences are with psilocin extract goo.
To give you an important time frame: I first experimented with psilocin summer 2010 perhaps june. The first few excursions weren't mediated by many visuals.
On one occasion, the potency of the psilocin was very strong and I began having a very intense close eyed visual, it was very psilocybian but very colorful and real, it was a full-on painted scenic imagination.
On other occasions I would drift off into a type of matrix and meet with this being (amongst others) above the stars and matrix and then view some omnipotent being/force opposing another invisible force. To say the least, the visual was very vague, in that there was more darkness than clear up-close personal scenic imagery, it was like a blurb of grey/white "color" being surrounded by space. So, in comparing to the experience first listed, it would have been less "clear"
Other excursions led me to very vague visuals (on less than 1 gram of extract, more than 1 gram always gave me great visual results). These visuals can be described as follows: Thinking of love, seeing the word love close-eyed and the word lights up with red vibrance and forms a heart around. Clearly, this isn't too much of an expanded visuals.
Coming from a "poor" sighted person, I believe that my visuals are different from those with better vision. I believe there is an association with processing speed by the afferent and efferent neurons/ganglia, if you are physically impaired somehow within the eye/muscle/nerve then you will more slowly send incoming information to the brain to be processed. If you think faster than you receive visual information it is likely you will miss important received points by anticipating. In turn, your attention is at a deficit. Once the actual information is received and processed, the output visual information that you actually "see" is very different from what a 20 20 person will see.
In all, it is a disorder within the brain/mind that needs to be fixed. I believe the answer lies within sounds oscillations, and the problem can be synced up by learning and utilizing creative centers in the brain. There is something that is causing you (me) to process light slowly, after seeing this other "guy" experience high frequency/intensity glossolalia and extremely detailed visuals, I am personally convinced that his visuals are extremely different than mine.
Sound/music is very important.
Regarding the "clearness", I guess the word to use would be "more developed", I have a feeling those with better vision and better brain organization and communication---by genes, environment who knows. My psychedelic partner is very musically creative, the more creative with reality you are the more you will see.
I still have yet to try ayahuasca and get the feeling that it might clear up my vision, any comments?