April 2011
Volume 52, Issue 14
Free
ARVO Annual Meeting Abstract  |   April 2011
Dynamic Alignment for Transpalpebral Tonometry
Author Affiliations & Notes
  • Gordon A. Thomas
    Physics, New Jersey Inst Technology, Newark, New Jersey
  • Robert D. Fechtner
    Dept of Ophthalmology, UMDNJ - New Jersey Med Sch, Newark, New Jersey
  • Footnotes
    Commercial Relationships  Gordon A. Thomas, None; Robert D. Fechtner, None
  • Footnotes
    Support  Hoffman Foundation Grant
Investigative Ophthalmology & Visual Science April 2011, Vol.52, 684. doi:
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      Gordon A. Thomas, Robert D. Fechtner; Dynamic Alignment for Transpalpebral Tonometry. Invest. Ophthalmol. Vis. Sci. 2011;52(14):684.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract
 
Purpose:
 

We are fabricating and testing a tonometer that would allow a patient to measure intraocular pressure (IOP) and aid in the diagnosis and monitoring of glaucoma. For reasons of patient safety and comfort we use a transpalpebral configuration and have improved the alignment protocol.

 
Methods:
 

Our improvement is dynamic alignment, which increases reproducibility of the IOP measurement. We have carried out over 100 measurements in our laboratory using a gentle robotic palpation that operates 1st in a constant position mode with a 0.5mm depression of the palpebrum with a force of 1g, and 2nd in a moving mode toward the eye, palpating the palpebrum and cornea over a distance and force range up to that of a Goldmann aplanation tonometer. We record electronic signals with a National Instruments A/D converter feeding a computer and indicating 1st the central corneal position and 2nd the IOP.

 
Results:
 

In the 1st mode we measure a curve of the force as a function of the angle of the eye orientation using the physiological feature of the cornea as a partial sphere with its radial center offset from that of the eye. We fit this curve with a lobe of a sin function and the corneal center at the maximum. With the eye aligned at the corneal center the second mode produces a linear curve with a correlation factor of typically 0.98 or better and p=0.005 or better for distances up to 1mm and forces up to 2 g. The slope, combined with a separate measurement of the palpebrum, determines the IOP and is reproducible to typically 0.2mmHg.

 
Conclusions:
 

The dynamically aligned tonometer output shows a reproducibility that is improved over previous measurements without dynamic alignment and may provide a practical approach for personal tonometry.  

 
Keywords: clinical laboratory testing • eye movements • eyelid 
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