Mario,
   Is the word "occhiale" to "occhio" as "oculalis" would be to "oculus"
in Latin?  For some reason "oculalis" sounds wrong.  (I don't really know
Latin).  In interlingua we would think of forming an adjective from
"oculo" (eye) by adding some adjectival ending like -al, but it seems to
me in this particular case, the -ar ending is the adjectival ending used.
The "lente ocular" in interlingua would be the lens at the eye end of a
telescope.          According to the Interlingua
Grammar (which reflects similar forms in romance languages) -al is
the most general and unspecific adjectival suffix. The variant -ar is
to be preferred with nouns containing -l; e.g. bussola 'compass" >
bussolar (of the compass).  In that case "ocular" is probably analogous
to "occhiale" in Italian. But am I not correct in supposing that Italian
"occhio" comes from Latin "oculus" (Interlingua "oculo")? But the reason
one can say in Italian "occhio > "occhiale" is because "occhio" doesn't
have an "-l-" in it near the end. But if Italian had kept "oculo", it
would have had "oculare".  And then spectacles would be "oculari".

What do you think?

Stan Mulaik