Euclid's Optics presents the visual cone with the apex at the eye as a geometric model for the appearance of things. In Optics various results are deduced about the appearance of flat surfaces below the eye and above the eye. See Figure 10 on page 359 in Burton’s translation, referenced below for a possible evidence that the visual cone might be intersected by a vertical plane in order to explain certain visual phenomena . Propositions 38-40 on pages 365-367 in Optics show how the circular base of a visual cone appears under certain circumstances. Although not expressed as "conic sections" the visual effects are described for acute and right and obtuse angle cones which correspond to whether the circle at the base of the visual cone is being viewed from a point on the hemisphere above the circle (right angle cone) , a point above the hemisphere (acute cone), or a point within the hemisphere (obtuse cone).
The first four books of Apollonius' Conics are generally believed to have drawn heavily from an earlier lost work by Euclid, also called Conics. It is believed that like Euclid, Apollonious also studied astronomy and optics. Geometrical optics, and the model of the visual cone, was used to study relationships between the apparent size, position, or motion of an object and its actual size, position, or motion.

Sources: http://philomatica.org/wp-content/uploads/2013/01/Optics-of-Euclid.pdf

Euclid's Optics presents the visual cone with the apex at the eye as a geometric model for the appearance of things. In Optics various results are deduced about the appearance of flat surfaces below the eye and above the eye. See Figure 10 on page 359 in Burton’s translation, referenced below for a possible evidence that the visual cone might be intersected by a vertical plane in order to explain certain visual phenomena . Propositions 38-40 on pages 365-367 in Optics show how the circular base of a visual cone appears under certain circumstances. Although not expressed as "conic sections" the visual effects are described for acute and right and obtuse angle cones which correspond to whether the circle at the base of the visual cone is being viewed from a point on the hemisphere above the circle (right angle cone) , a point above the hemisphere (acute cone), or a point within the hemisphere (obtuse cone).
The first four books of Apollonius' Conics are generally believed to have drawn heavily from an earlier lost work by Euclid, also called Conics. It is believed that like Euclid, Apollonious also studied astronomy and optics. Geometrical optics, and the model of the visual cone, was used to study relationships between the apparent size, position, or motion of an object and its actual size, position, or motion.

Sources: http://philomatica.org/wp-content/uploads/2013/01/Optics-of-Euclid.pdf