Abstract • The tip diameter of the standard Goldmann applanating prism was reduced from 7.0 mm to 4.0 or 4.5 mm, but the endpoint of intraocular pressure measurement—applanation of a circle of cornea having a diameter of 3.06 mm—was not changed. The "minified" tonometers exhibited standard mechanical calibration characteristics in three standard configurations. The 4.5-mm tonometer was calibrated for cynomolgus monkey eyes in vivo by open and closed stopcock manometry. By open stopcock manometry, between pressures of 4 and 70 mm Hg, IOP(tonometer) = 1.01 IOP(manometer) – 0.72, with very little scatter or curvature. During closed stopcock manometry, between pressures of 5 and 55 mm Hg, IOP(tonometer) = 1.07 IOP(manometer)– 1.32, again with very little scatter or curvature. The tonometer elevated manometric IOP by an average of about 7.5%; the percentage pressure elevation decreased slightly as pressure increased. The 4.0-mm tonometer was calibrated against a standard tonometer in living human eyes. Over the pressure range from 0 to 75 mm Hg, IOP(minitonometer) = 0.98 IOP(standard tonometer)+ 0.82, with very little scatter or curvature. Similar comparison of two standard tonometers showed a virtually identical relationship and scatter. We conclude that minified Goldmann tonometers provide accurate and reproducible measurements of IOP in cynomolgus monkey and human eyes. References 1. Bechrakis E: Ueber den spontanen Druckabfall bei Applanations-tonometrie . Ophthalmologica 151:604-614, 1966.Crossref 2. Moses RA, Ching-Hung L: Repeated applanation tonometry . Am J Ophthalmol 66:89-97, 1968. 3. Wilke K: Effects of repeated tonometry: Genuine and sham measurements . Acta Ophthalmol 50:574-582, 1972.Crossref 4. Hahnenberger RW: Applanation tonometry in the conscious cynomolgus monkey (Macaca fascicularis) . Acta Ophthalmol 54:311-319, 1976.Crossref 5. Draeger J: Simple hand applanation tonometer for use on the seated, as well as on the supine patient . Am J Ophthalmol 62:1208-1210, 1966. 6. McMillan F, Forster RK: Comparison of MacKay-Marg, Goldmann, and Perkins tonometers in abnormal corneas . Arch Ophthalmol 93:420-424, 1975.Crossref 7. Perkins ES: Hand-held applanation tonometer . Br J Ophthalmol 49:591-593, 1965.Crossref 8. Mims JL III, Holland MG: Applanation and Schiøtz tonometer standardizations for the owl monkey eye with a new technique for measuring episcleral venous pressure . Invest Ophthalmol 10:190-197, 1971. 9. Schmidt TFA: On applanation tonometry . Trans Am Acad Ophthalmol Otolaryngol 65:171-177, 1961. 10. Moses RA: The Goldmann applanation tonometer . Am J Ophthalmol 46:865-869, 1958. 11. Moses RA, Marg E, Oechsli R: Evaluation of the basic validity and clinical usefulness of the MacKay-Marg tonometer . Invest Ophthalmol 1:78-85, 1962. 12. Moses RA: The MacKay-Marg tonometer . Trans Am Acad Ophthalmol Otolaryngol 66:88-95, 1962. 13. Hilton GF, Shaffer RN: Electronic applanation tonometry . Am J Ophthalmol 62:838-843, 1966. 14. Tierney JP, Rubin ML: A clinical evaluation of the electronic applanation tonometer . Am J Ophthalmol 62:263-272, 1966. 15. Irvine AR, Kaufman HE: Intraocular pressure following penetrating keratoplasty . Am J Ophthalmol 68:835-844, 1969. 16. Kaufman HE: Pressure measurement: Which tonometer? Invest Ophthalmol 11:80-85, 1972.
Archives of Ophthalmology – American Medical Association
Published: Mar 1, 1980