PubMed · 17189772
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Bruno Zuberbuhler, Andrew J Morrell. 2007. Errata in printed Hoffer Q formula.. https://doi.org/10.1016/j.jcrs.2006.08.054
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PURPOSE: To present a model of pulsatile-flow of aqueous humor from posterior (PC) to anterior chamber (AC) and to analyze the sensitivity of this novel model in detecting typical high risk conditions predisposing to pupillary block. METHODS: The model assumes noncontinuous flow of aqueous through the iris-lens canal. Aqueous that fills the canal will be ejected toward the AC-side of the canal at certain time intervals, and between 2 events of aqueous ejection there is no actual flow through this canal. Pupillary pumping rate (PPR) was calculated from the aqueous flow rate and the calculated volume of iris-lens canal. RESULTS: PPR values were generated by incorporating pupillary diameter (1 to 8 mm), aqueous flow rate (1 to 2.5 microL/min), and iris-lens canal width (0.5 to 2 mm) and height (3-9 microm) in numerical experimentation with the present model. PPR showed inverse dependence on iris-lens canal height and pupillary diameter and was directly proportional to aqueous flow rate, in agreement with the steady-flow model. However, contrary to the steady-flow model, PPR showed inverse dependence on iris-lens canal width and predicted the anticipated PC-AC pressure gradient changes at simulated light-dark transition in eyes of patients with clinically narrow angles and ultrasound biomicroscopy evidenced pupillary block. CONCLUSIONS: Upon the incorporation of real ultrasound biomicroscopy measurements in numerical experimentations with both models, the present pulsatile-flow model, contrary to the steady-flow model, showed good predictability of PC-AC pressure gradient changes in a typical condition predisposing to pupillary block.
PURPOSE: To compare measurements of anterior chamber depth (ACD) and corneal curvature obtained with the Pentacam to other commonly used devices. DESIGN: Prospective, nonrandomized clinical trial. METHODS: Measurements of ACD and keratometry were prospectively obtained in 22 eyes of 11 subjects with the Pentacam compared with measurements of the ultrasound (US) A-scan and IOLMaster (ACD), and with those of automated keratometry (AK) and IOLMaster (keratometry) at the Assaf Harofeh Medical Center. RESULTS: The mean interdevice differences in keratometry for Pentacam vs AK, Pentacam vs IOLMaster, and AK vs IOLMaster were -0.046 diopters, -0.471 diopters, and -0.424 diopters, respectively. Measurements of keratometry by the IOLMaster differed statistically significantly from those of Pentacam (P < .01) and AK (P < .01). For measurement of keratometry, 95% limits of agreement were -1.321 to 1.229 diopters for the Pentacam and AK, -1.478 to 0.536 diopters for the Pentacam and IOLMaster, and -1.026 to 0.178 diopters for the AK and IOLMaster. The mean interdevice differences in ACD for the Pentacam vs US, Pentacam vs IOLMaster, and US vs IOLMaster were 0.103, 0.099, and -0.004 mm, respectively. Measurements of ACD by the Pentacam differed statistically significantly from those of US (P < .05) and IOLMaster (P < .01). For measurement of ACD, 95% limits of agreement were -0.197 to 0.404 mm for the Pentacam and US, -0.169 to 0.367 mm for the Pentacam and IOLMaster, and -0.332 to 0.324 mm for the US and IOLMaster. CONCLUSIONS: For some clinical applications, measurements of ACD and corneal curvature with the tested machines may differ greatly and therefore may not be interchangeable.