In the most refractive eyes the peak sensitivity of retinal rods and cones pigment is?
260 and 500 respectively
460 and 480 respectively
398 and 550 respectively
498 and 555 respectively
Ans. d (498 and 555 respectively). (Adler's Physiology of the Eye 11th/Pg.529)# Peak sensitivity for cones = 555 nm, but combination of R, B, and G cones (cones short wavelength - 420, cones middle wavelength - 534, and cones long wavelength 564).# Peak sensitivity for rods = 498 nm.FUNCTIONALLY THERE ARE TWO SEPARATE RETINAS:Night retinaDay retinaRodsConesNo colorComplete colorLow acuity (fovea blind)High acuityScotopic or mesopic with luminance < 3 cd/m2Photopic# Photoreceptor density - Because rods and cones have different spectral sensitivities and different absolute sensitivities to light, the visual response is not the same over the retina.- Rods -130,000,000.- Cones - 7,000,000.# Cones are concentrated in the fovea and receptive fields are small in this region.# Rods are absent in macula leutea (Yellow pigment).Adaptation# Cones adapt more rapidly than rods.# Cones regain complete sensitivity in 10-12 minutes.# Rods regain complete sensitivity in 30-60 minutes
Retina