Spherical aberration of crystalline lens in the roach,Rutilus rutilus L.

Summary

• 1. The lowest optimal value of the relative focal length for paraxial rays (=f ₀/R, R= radius of crystalline lens) known in fish was found which equalled to 2.192 at 546 nm wave-length.

• 2. The value of the radius of effective entrance area of crystalline lens, amounting to 0.910R, was the lowest of those obtained in fish, too.

• 3. The longitudinal spherical aberration, expressed as the spherical aberration area,S _LA, depends parabolically upon the relative focal length for paraxial rays.

• 4. Similarly to pike and rainbow trout in which species the spherical aberration was studied recently, the distribution of data of the relative focal length for paraxial rays about their optimal value is asymmetric, and therefore the regression curve which represents a relationship betweenf ₀/R andS _LA is only a halfparabola (Fig. 3).

• 5. A comparison to pike and rainbow trout yields that, although the degree of spherical aberration removal in all the species seems to be nearly the same, the differences between various species are remarkable due to a role which is played by the irregularities of both the external shape of crystalline lens and the internal distribution of refractive indices of lenticular tissue. Hence it is assumed that the quality of a monochromatic image formed on the retina of roach is poorer than it might be expected in pike and rainbow trout.

• 6. A continuing the investigations on spherical aberration of crystalline lens in fish promises good prospects for solving the problem of refractive index distribution and that of resolution angle.