Distribution of S‐ and M‐cones in normal and experimentally detached cat retina

The lectin peanut agglutinin (PNA) and antibodies to short (S)‐ and medium to long wavelength (M/L)‐sensitive cones were utilized in order to define the relative distributions of the two spectral types of cone across the domestic cat's retina. These values, in turn, were compared to those from retinas that had been experimentally detached from the retinal pigment epithelium. The pattern of cone distribution in the normal cat's retina is established by the preponderance of M‐cones that constitute between 80% and 90% of all cones. Their peak density of over 26,000 cells/mm 2 resides at the area centralis . Though M‐cone density decreases smoothly to the ora serrata where they have densities as low as 2,200 cells/mm 2 , the density decrease along the nasotemporal axis is slower,creating a horizontal region of higher cone density. S‐cones constitute between 10% and 20% of all cones, the number being quite variable even between individual animals of similar age. The highest S‐cone densities are found in three distinct locations: at the superior far periphery near the ora serrata, immediately at the area centralis itself, and in a broad zone comprising the central and lower half of the inferior hemiretina. S‐cones in the cat retina do not form a regular geometrical array at any eccentricity. As for the detached cat retina, the density of labeled S‐cone outer segments (OS) decreases rapidly as early as 1 day postdetachment and continues decreasing to day 28 when the density of cones labeling with anti‐S opsin has dropped to less than 10% of normal. This response points to a profound difference between rods and cones; essentially all rods, including those without OS, continue to express their opsin even in long‐term detachments. The implications of these results for visual recovery after retinal reattachment are discussed. J. Comp. Neurol. 430:343–356, 2001. © 2001 Wiley‐Liss, Inc.