The main structures of the eye and a condition that could be diagnosed to that particular structure:
Cornea - Keratoconus
Iris - Iritis
Pupil - Bene dilitatism
Lens - Cataract
Retina - Retinal detachment
Macula - Age-related Macular Degeneration
Optic Nerve - Optic neuritis
Vitreous - Floaters