Optical explanation of the gradual disappearance of flying dots in posterior vitreous detachment.
It is well-known that flying dots (muscae volitantes) in posterior vitreous detachment gradually disappear. An analogy for this phenomenon is the optical effect of planets casting conic shadows as they are lighted by the sun (in this case the pupil serves as the light source) and these shadows shrink as the planets near the sun. When the opacities move forward in the vitreous cavity, their shadows are not long enough to reach the retina, so the flying dots disappear. They can also disappear when their shadows fall on the optic disk or when they are mixed with the random pattern of bright and dark areas of the retinal image in ordinary conditions. Pupil dilatation makes the conoid shadow shorter; thus, the flying dots became fainter. In advanced cataract, stray light makes the retinal image less sharp, reducing the perception of dots. Replacement of the opacified lens by an intraocular lens restores the sharpness of the retinal image, because the light entering the eye becomes less diffuse, making the flying dots more obvious. The same reasoning explains similar phenomena in aphakia and large ametropias with and without corrective spectacles, as well as opacities of any etiology in the vitreous.
Serpetopoulos
C
C
D005128:Eye Diseases / Q000175:diagnosis / Q000209:etiology; D006801:Humans; D055095:Optics and Photonics; D014822:Vitreous Body / Q000473:pathology*