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PAM( POTENTIAL ACUITY METER).

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The chart projected by PAM consist of range of snellen's acuities from 20/20 to 20/400. It Used to assessment of potential vision and it is a samall instrument mounted on a slit lamp. Which focus a single beam of light in the pupil and a letter chart on to the retina. It correctly predict post operative visual acuity in patients with moderate cataract. Procedure Dilate the pupil before examination. Tiny beam of light is directed through the pupil onto the retina through the clearareas of lens. Ask the patients to read the chart. Measure potential vision from the smallest line which the patient is able to read.

placido disc

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    It is a Corneal topographer .     Placido disc is used to evaluating anterior surface of cornea and detecting early stages of keratoconus. The principle is first purkinje image formed by reflection from black and white ring.