Optical characteristics of the eye of the spiny dogfish (Squalus acanthias).

On the basis of the failure of attempts to induce refractive accommodation changes electrically and with drugs, it appears that the eye of the spiny dogfish (Squalus acanthias) lacks the capacity to accommodate. Retinoscopic measurements indicate moderate hyperopia (+6D). However, measurements made with light restricted to the short end of the visible spectrum indicate only one or two dioptres of hyperopia and it is possible that the latter measurements are more coincident with natural conditions. In contrast to the somewhat flattened lens of other elasmobranchs the lens of the spiny dogfish is nearly spherical. The fact that its refractive index is high (1.66) suggests that the static optical system of this eye is very similar to that of the teleosts.