Kestenbaum's number as an indicator of pupillomotor input asymmetry

Mei Qi Jiang, H. Stanley Thompson, Byron L. Lam

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


We compared the direct light response of both eyes in 90 patients who had anterior visual pathway disease using two different testing methods. We measured Kestenbaum's number in millimeters of pupillary diameter. Kestenbaum's number (K) is the difference in the pupil size attained in each eye under direct illumination while the other eye is occluded. We then measured the relative afferent pupillary defect (RAPD) in log units using neutral density filters. The two tests gave similar results (K = 0.88 × RAPD). Kestenbaum's number is the less precise measure, but it can be quickly and cheaply estimated even in dark brown eyes. The filter test requires a set of filters and at least one well-innervated iris sphincter. Kestenbaum's number can be measured without filters, but the iris sphincter and dilator muscles in both eyes must be normally innervated.

Original languageEnglish (US)
Pages (from-to)528-530
Number of pages3
JournalAmerican journal of ophthalmology
Issue number5
StatePublished - May 15 1989
Externally publishedYes

ASJC Scopus subject areas

  • Ophthalmology


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