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To the Editor:
—May I make a few comments on the review of some of my papers which Dr. Rand contributed to the October 1947 issue of the Archives, page 529? She refers to Granit's work on animals with the microelectrode and to my attempts to investigate the properties of the human retina, using an optical instrument called the retinal microstimulator. She states, ``Hartridge utilized `tenuous beams of light' sufficiently narrow to subtend at the eye an angle of only 8 seconds of arc and to form on the retina, he claims, geometric images equal to onefifth cone unit. (One `cone unit,' according to Hartridge, subtends an angle at the observer's eye of 41.236 seconds of arc)." This is quite true, but I have pointed out with great care that the diffraction of light and the residual aberration of the human eye must cause the light of which the retinal
Hartridge H. COMMENTS ON DR. RAND'S LETTER ON HARTRIDGE'S ARTICLE ON PHYSIOLOGY OF VISION. Arch Ophthalmol. 1949;42(2):193-197. doi:10.1001/archopht.1949.00900050198013