Not every ophthalmologist seems to realize the extreme importance of having the anterior focus of each eye at exactly the same distance, and many who try to obtain this fail because of the improper methods used.
If the anterior focal points are not exactly at the same place the ciliary muscles in their ceaseless efforts to find a position of rest will be under a constant seesaw. Every ophthalmologist finds cases in which comfort and good vision can be obtained for each eye separately, yet when the patient looks with both eyes, he complains of discomfort and dizziness and of not being able to see clearly. The problem is how to remedy this.
Many patients with glasses have the same visual acuity in each eye. After refracting such cases, and while they view distant test-types with both eyes, I take a plus and minus sphere of .25 diopter strength and place
STEVENSON MD. HOW TO PLACE LENSES BEFORE THE EYES SO THAT DISTANCE OF THEIR RESPECTIVE ANTERIOR FOCI SHALL BE THE SAME. JAMA. 1900;XXXV(8):476–477. doi:10.1001/jama.1900.24620340012001d
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