In clinical practice, sometimes an optometrist or an ophthalmologist will give a prism prescription. At this time, it is necessary to check whether the prism degree and prism bottom direction of the matching glasses are consistent with the prescription. For glasses without a prism prescription, it is also necessary to check whether the prism error is within the acceptable range. For more about

what is a prism in eyeglasses, please check this article.

(1) Telephoto focal meter measurement

1. Choose a focimeter that has passed the inspection and make preparations.
2. Put the assembled glasses on the lens stand, adjust them left and right, front and back, so that the prism measurement point of the glasses is at the center of the lens support ring, and then fix it after adjustment.
3. Adjust the focusing handwheel so that the moving reticle is clearly imaged on the fixed reticle, and then the measurement can be carried out. At this time, the angle and distance between the center of the moving reticle image and the reticle scale of the telescope are the base directions of the lens prism and its prism.

(2) Automatic focal meter measurement
1. Choose a focimeter that has passed the inspection and make preparations.
2. Put the assembled glasses on the lens stand, adjust them left and right, front and back, so that the prism measurement point of the glasses is at the center of the lens support ring, and then fix it after adjustment.
3. At this time, the prism degree and angle displayed on the screen are the prism degree and base direction of the lens.