CLINICAL REFRACTION

Retinoscopy

Retinoscopy is used with plane mirror settings.
the patient is asked to look at distant target like largest letter on snellens chart
light is thrown into patiens pupil and examiner observes the reflex of light in patient pupil. If a with movement is observed then increasing plus lenses are placed in front of patients eyes.
if against reflex is seen, increasingly minus lenses placed infront of patients eye.
the point where no movement of reflex is observed and light fills the pupil completely is taken as neutral point.
With 2 spheres. Neutralize 1 axis with a spherical lens; then neutralize the axis 90° away. The difference between these readings is the cylinder power. For example, if the 90° axis is neutralized with a +1.50 sphere and the 180° axis is neutralized with a +2.25 sphere, the gross retinoscopy is +1.50 +0.75 × 180. The examiner’s working distance (ie, +1.50) is subtracted from the sphere to obtain the final refractive correction: plano +0.75 × 180
formula is R1/R2-R1 WITH AXIS OF R1

spheres are placed with increasing number untill patient sees clearly