and are disposed in three meridian directions which intersect one another at 60 u00b0 about a point on the optic axis a projection index mark 18 for measurement is in the form of a circular slit and may be projected onto the eye e to be examined by the illuminating light of a ring fluorescent lamp 19 for observation or of a ring strobo 20 for measurement so as to form a mire image m virtual image by the corneal reflection on the front eye part of the eye e to be examined a light intercepting plate 22 operated by a solenoid 21 is removably disposed in the optical path of the illuminating light as is well known the surface shape of the cornea can be measured by detecting the shape of the mire image m the mire image m is reflected by the beam splitter 6 and passes through the imaging lens 12 of the measuring system whereafter it is optically divided by the two half mirrors 13 and 14 and imaged on the light receiving surfaces of the first second and third ccd elements 15 16 and 17 the shape of the mire image m is detected by the coordinates of points of intersection a x 1 y 1 b x 2 y 2 c x 3 y 3 d x 4 y 4 e x 5 y 5 f x 6 y 6 with the three ccd elements 15 16 and 17 by substituting the coordinates of these six points into the general equation of a quadratic curve and thereby finding each coefficient and effecting operation processing such as coordinates conversion.