How many diopters does Pin hole test neutralize?
ANSWER: (C) 3DREF: Oxford American Handbook of Ophthalmology By James Tsai Pg 7, Ophthalmology at a glance by J.Olver Ch 8The pinhole (stenopeic slit upto 1.2 mm) can neutralize upto 3 Dioptres of refractive error.It is a useful method of finding out if the patient is suffering from refractive errors. If the vision improves with a pinhole test, it means that the patient has a refractive error. See the diagram below:In emmetropia every point in an object of regard is brought to point focus on the retina and the sum of all the points yields a clear image, i.e. point-to-point correspondenceIf there is a refractive error present, a blur circle is formed on the retina, which is dependent on the size of their pupil (smaller pupil = smaller blur circle)When a pinhole aperture is placed in front of the eye, it acts as an artificial small pupil and the size of the blur circle is abolished/reduced, producing a clearer image
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Anatomy