Scissor reflex is seen in-

SIGNS OF KERATOCONUS:1. Window reflex is distoed. 2. Placido disc examination shows irregularity of the circles . 3. Keratometry depicts extreme malalignment of mires. 4. Photokeratoscopy reveals distoion of circles. 5. Slit lamp examination may show thinning and ectasia of central cornea, opacity at the apex and Fleischer's ring at the base of cone, folds in Descemet's and Bowman's membranes. Very fine, veical, deep stromal striae (Vogt lines) which disappear with external pressure on the globe are peculiar feature. 6. On retinoscopy a yawning reflex (scissor reflex) and high oblique or irregular astigmatism is obtained. 7. On distant direct ophthalmoscopy an annular dark shadow (due to total internal reflection of light) is seen which separates the central and peripheral areas of cornea (oil droplet reflex). 8. Munson's sign, i.e. localised bulging of lower lid when patient looks down is positive in late stages.Reference:Comprehensive ophthalmology,AK Khurana,4th edition,page no.119