Strabismus or squint is tested by cover test or redglass test
Red Glass Test
To identify the defective eye in diplopia
Patient is asked to look at an object placed in the direction of diplopia
Red glass is placed over one eye
A Red image is false if the eye over which the glass is placed is defective
A white image is false- the other eye is defective .
Principles
The outer image is the false image
The separation of the images is maximum in the direction of action of the paretic muscle
Cover test
Instruct to fix the eyes on an object in front
Suddenly cover the apparently fixing eye, so that the other eye fixes
A deviation of the uncovered eye is called primary deviation
A deviation of the covered eye is called secondary deviation
Concomitant squint -primary deviation secondary deviation
Paralytic squint primary -deviation less than secondary deviation
Red Glass Test
To identify the defective eye in diplopia
Patient is asked to look at an object placed in the direction of diplopia
Red glass is placed over one eye
A Red image is false if the eye over which the glass is placed is defective
A white image is false- the other eye is defective .
Principles
The outer image is the false image
The separation of the images is maximum in the direction of action of the paretic muscle
Cover test
Instruct to fix the eyes on an object in front
Suddenly cover the apparently fixing eye, so that the other eye fixes
A deviation of the uncovered eye is called primary deviation
A deviation of the covered eye is called secondary deviation
Concomitant squint -primary deviation secondary deviation
Paralytic squint primary -deviation less than secondary deviation