LENS AND LOUPE
Ophthalmic procedure and instrument help to diagnose disease and detailed examination of with the help of ophthalmic instrument.
This is a very handy instrument used to examine structures of anterior segment of eyeball.
It consists of a condensing lens of +13D and a corneal loupe of power +41D (consisting of two plano-convex lenses of power +20.5D each) with 10X magnification.
It is based on the principle that when an object is placed between a convex lens and its focus, the image formed is erect, magnified, virtual and on the same side of the lens
Technique
Patient is seated on a stool with a light source coming from front and lateral side from a distance of two feet.
Condensing lens is held in one hand and used to focus light on structure to be examined.
Loupe is held in other hand between thumb and index finger.
Little finger and ring fingers are rested on forehead for stability of hand and upper eyelid is lifted with middle finger.
Loupe is brought close to the eye so that the cornea comes into focus.
By changing the position of condensing lens, corneal loupe and position of eyes of observer; different structures of anterior segment can be examined one by one.
Lens and Loupe has fallen into disrepute with more and more use of binocular loupe and slit lamp.
Binocular loupe has the added advantage of binocularity but magnification is lesser as compared to uniocular loupe.
It is fixed to the examiner’s head hence lesser maneuver is required.
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OPHTHALMIC PROCEDURES