Regarding “Assessment of ocular perfusion after carotid endarterectomy with color-flow duplex scanning”
Article Outline
To the Editors:
In the recent report by E. Jerry Cohn, Jr, and colleagues (J Vasc Surg 1999;29:665-71), the discussion contains an error in the sentence, “The use of the OPG has been largely abandoned…because concern existed about the nonphysiologic pressures that were applied to the globe….” The maximum intraocular pressure generated with the ocular pneumoplethysmograph (OPG-Gee) is 145 mm Hg. This is a physiologic intraocular pressure. It has been shown that vigorous contraction of the muscles involved in eyelid closure elevates the intraocular pressure to 90 mm Hg.1 Other investigators demonstrated that simple rubbing of the eye elevates the intraocular pressure to the 150 to 250 mm Hg range.2 Most individuals perform this act several times a day, every day of their lives, and it is instinctive. One need only witness the tired child with both fists boring into the respective orbits as relief is sought as a result of a few mm Hg decrease of the intraocular pressure. Less remote is the medical student preparing for the first examination in gross anatomy, who leans back, after hours of studying, and vigorously rubs the eyes. The effect is simple, elevation of the intraocular pressure above ophthalmic systolic pressure, interruption of arterial inflow and increase of fluid outflow, resulting in a reduction of the intraocular pressure by several mm Hg, which feels good and is most physiologic! The intraocular pressure is elevated by increasing the tension in the corneoscleral shell, and the two methods of increasing the tension, scleral indentation and scleral vacuum, are identical in their effect on the globe. The instrument and its application have been defended in the ophthalmic literature.3, 4, 5, 6
Oculo-oscillodynamography (OODG-Ulrich), mentioned by the authors, was developed by an ophthalmologist.7 This instrument closely parallels the OPG-Gee in design and function. Recent papers attest to the value of this device.8, 9
One wonders why, in their series of 29 patients, the authors excluded the data from the eyes contralateral to the side of operation. A recent report contains the bilateral ocular volume change per minute, before and after carotid endarterectomy, in 1737 patients.10 Of particular interest, in the latter report, is the considerable difference in ocular hemodynamics that exists between male and female patients.
24/41/100905
References
- . Direct-recorded intraocular pressure variations in a human subject. Arch Ophthalmol. 1969;82:637–640
- . No-touch technique for intraocular malignant melanomas. Arch Ophthalmol. 1977;95:1616–1620
- . Anterior ischemic optic neuropathy following ocular pneumoplethysmography [letter]. J Clin Neuro-ophthalmol. 1987;7:58
- . Editorial comment. J Clin Neuro-ophthalmol. 1987;7:59
- . Ocular pneumoplethysmography after lens implantation. J Cataract Refract Surg. 1988;14:417–420
- . Ocular pneumoplethysmography after lens implantation [letter]. J Cataract Refract Surg. 1989;15:115–116
- . Oculo-oscillo-dynamography: a diagnostic procedure for recording ocular pulses and measuring retinal and ciliary arterial blood pressures. Ophthalmic Res. 1985;17:308–317
- . Detection of disturbed autoregulation of the peripapillary choroid in primary open angle glaucoma. Ophthalmic Surg Lasers. 1996;27:746–757
- . Influence of panretinal photocoagulation on the ocular pulse curve. Am J Ophthalmol. 1997;123:748–752
- . Ocular volume change per minute with ocular pneumoplethysmography. Ophthalmic Res. 1999;31:351–357
PII: S0741-5214(99)70026-1
© 1999 Mosby, Inc. All rights reserved.
