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To the Editor:
—Dr. Pascal's effort to clarify what he claims is a minor but significant point in the physiology of vision seems to me to confuse it more than ever. When one speaks of a retinal image, one means only the distinct image on the retina. Dr. Pascal confuses a diffusion image with a distinct image. It is not correct to measure the size of a retinal image formed between the two secondary axes that pass from the extremities of an object through the nodal point. The nodal points need not be taken into consideration at all in measuring the size of the retinal image. Gullstrand disregarded them entirely. All images formed by an optical system are optical images. The only important image is the distinct one, and that is the image under consideration. The statements made in my book seem to me to be perfectly clear and concise
Cowan A. ACCOMMODATION AND RELATIVE IMAGE SIZE. Arch Ophthalmol. 1950;43(1):143-144. doi:10.1001/archopht.1950.00910010147010