Development of calibrated leakage measurement device for ...

Development of calibrated leakage measurement device for ...

DEVELOPMENT OF A CALIBRATED LEAKAGE MEASUREMENT DEVICE FOR OCULAR TONOMETRY Jonathan Cox 21st Annual Arizona Space Grant Consortium Symposium April 21, 2012 MOTIVATION Glaucoma is a disease that leads to damage of the nerve that carries visual information to the brain Elevated intraocular pressure is a significant risk factor for developing glaucoma TONOMETRY Goldmann Applanation Tonometry Novel Tonometer Concept

Air Puff Tonometry ANATOMY OF THE EYE Aqueous humor is housed in the anterior chamber Maintains intraocular pressure Aqueous humor exits anterior chamber at a rate of 2-3 L/minL/min MEASURING OUTFLOW WITH FLUORESCENCE Fluorescence Droplet forming on eye MATLAB Interpretation

METHODOLOGY i = imread(***.jpg'); stats = regionprops(L,'Area'); g = rgb2gray(i); Area = [stats.Area]; gadjust = imadjust(g); Area = Area/1000; c = roicolor(gadjust,0,100); Volume = .0297*Area^2+.177*Area-.0402 cNC = bwareaopen(c,1000) Calibration Curve 30 cfinal = bwareaopen(cNC,1000); 25 imshow(cfinal);

20 se = strel('disk',3,8); bwc = imclose(cfinal,se); Volume (microliters) cNC = ~cNC;%reverse 15 10 5 bwfinal = imopen(bwc,se); 0 L = bwlabel(cfinal); -5 0 5

10 15 20 Projected Area (pixels*103) Courtesy of X. Chen Volume Calibration Curve 25 EXPERIMENTAL RESULTS Flow Rate v. Time Droplet Volume v. Time 2.5 4.5 15 mmHg 20 mmHg 25 mmHg

30 mmHg 35 mmHg Droplet Volume (microliters) 3.5 3 15 mmHg 20 mmHg 25 mmHg 30 mmHg 35 mmHg 2 Flow Rate (microliters/min) 4 2.5 2 1.5 1.5 1

0.5 1 0.5 0 0 0 0.5 1 1.5 Time (minutes) 2 Droplet Volume v. Time V 2.5 0

0.5 1 1.5 Time (minutes) 2 2.5 Flow Rate v. Time = =0 + 1 2 2 INTERPRETATION , the time constant, is a

parameter that describes the transient response of a system Experiment (mmHg) (minutes) 15 3.5 20 25 25 2 1.8 1.8 30 30 35 35 1.8

1.8 3.9 3.9 Polyvas et al., 2012 CONCLUSIONS Leakage, while important to maintenance of intraocular pressure, is not a significant factor when taking pressure measurements The primary pressure relaxation mechanism of the eye is the viscoelastic behavior of the corneo-scleral shell ACKNOWLEDGEMENTS NASA Arizona Space Grant Consortium

Mentor Dr. Eniko Enikov Students Peter Polyvas Marcel Madarasz Xiao Chen THANK YOU FOR YOUR ATTENTION

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