On the lens pad of Benthalbella infans, a scopelarchid deep-sea teleost

The tubular eye of scopelarchids contains a lens pad, derived from cornea, lateral to the lens and opposite a gap in the iris. The pad, transparent in life, is formed of optically dense lamellae arranged at ca. 45 degrees to the sagittal plane of the fish. The lamellae are ca. 155 nm thick, separated by ca. 185 nm. The pad does not deviate light passing normally through the lamellae, but does deviate light at an acute angle to the lamellae unequally through ca. 40 degrees, converting a spot to a streak. Light from ca. 20 degrees to the vertical below the fish will be projected onto the accessory retina of the dorsally pointing tubular eyes. The pad also disperses white light, blue light ca. 34 degrees and red light ca. 44 degrees. The deviation of light from below may enable the fish to detect predators below, and the dispersion may play a role in breaking camouflage by spreading photophore light over an area of retina.