Cones contain light-sensitive molecules which derived from vitamin A and are contained in the disc membranes of the photoreceptor outer segments. The discs are attached to a cilium, which is rooted through neurotubules in the ellipsoid and myoid of the inner segment. The ellipsoid, which is adjacent to the cilium, contains mitochondria and is responsible for the cone shape.
The myoid, which is closer to the photoreceptor nucleus, contains endoplasmic reticulum. The mitochondria, cilia, and inner discs together form the IS/OS junction . So, we chose color vision as parameter to assess IS/OS integrity.Gualtieri et al. 18 reviewed that early diabetic color vision abnormalities tested by color vision test and full-field electroretinogram are more likely attributable to generalized neural-glial retinal dysfunction rather than specific dysfunction of S-cones or the lens as reported in some previous studies.