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aplanatic foci A pair of conjugate object and image points for which an optical system is free of spherical aberration. Syn. aplanatic points.
dark focus See resting state of accommodation.
depth of focus See depth of focus.
principal focus The axial image point produced by an optical system of an infinitely distant object (the second principal focus or posterior principal focus), or that axial object point for which the image will be formed at infinity (the first principal focus or anterior principal focus). A converging optical system or lens has two principal foci that are real. A diverging optical system or lens has a second principal focus that is virtual. In curved mirrors the two principal foci coincide. Depending upon whether the object is at infinity or at the principal focus, this same focal point becomes either the second principal focus or the first principal focus, respectively. Syn. focal point. See focal length; equivalent power; sign convention.
real focus See focus.
sagittal focus; tangential focus See oblique astigmatism.
virtual focus See focus.
Patient discussion about focusing
Q. My mind is getting confused now and i am losing on my focus. why is this change happening in me? I am a bipolar for the past 1 year. With the help of the medicines my episodes has come down. My mood is good and stable. Even my friends say that I am well as compared to previous years. But since last week I am not able to sleep well. My disrupted and reduced sleep is making me stressed. I just get 2-3 hours of sleep at night. After my lunch my tiredness starts again. My mind is getting confused now and I am losing on my focus. Why is this change happening in me?
Q. Is there a verity of exercises i can do with my child that would be helpful for him to be more focused and relaxed and by that help him to control the ADHD effects ?