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August 1992

Larger Optic Nerve Heads Have More Nerve Fibers in Normal Monkey Eyes-Reply

Author Affiliations

Baltimore, Md
Los Angeles, Calif

Arch Ophthalmol. 1992;110(8):1043. doi:10.1001/archopht.1992.01080200022007

In Reply.  —There is considerable variation in the number of optic nerve fibers among monkey or human eyes.1 Likewise, the size of the optic disc varies among eyes.2 These two features compose the most important variables that determine the cup-disc ratio or neural rim area, the parameters by which we estimate glaucoma damage. To study the extent to which fiber number and disc area might be related to each other, we estimated the number of optic nerve fibers in 25 monkey eyes by a histologic method and measured the disc area of the same eyes from clinical photographs.These data show a significant positive slope when analyzed by the linear regression method (our Fig 1). A positive slope means that as the optic disc area increases, so does fiber number. After accounting for disc area, there is still variation in fiber number from eye to eye that may

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