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| Fig:- Pinhole |
Pinhole disk is a small disk with central opening that prevents peripheral rays of light to pass through (Fig. 2.3). The optimal size of the central opening is 1.2mm. Larger size pinholes do not effectively neutralize refractive error and smaller size pinholes significantly increases diffraction and decreases the amount of
light entering the eye. Some trial lens set also contains multiple pinhole disk which also serves the same purpose. The patient finds easier to use multiple pinhole disk as he does not require Figure 2.2:
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