Development of A calibrated leakage measurement device for ocular tonometry
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Transcript of Development of A calibrated leakage measurement device for ocular tonometry
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Jonathan Cox
21st Annual Arizona Space Grant Consortium Symposium
April 21, 2012
DEVELOPMENT OF A CALIBRATED LEAKAGE MEASUREMENT DEVICE FOR
OCULAR TONOMETRY
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• 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
MOTIVATION
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TONOMETRY
Goldmann Applanation Tonometry
Air Puff TonometryNovel Tonometer Concept
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• Aqueous humor is housed in the anterior chamber
• Maintains intraocular pressure
• Aqueous humor exits anterior chamber at a rate of 2-3 μL/min
ANATOMY OF THE EYE
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MEASURING OUTFLOW WITH FLUORESCENCE
Droplet forming on eye
Fluorescence
MATLAB Interpretation
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i = imread(‘***.jpg');
g = rgb2gray(i);
gadjust = imadjust(g);
c = roicolor(gadjust,0,100);
cNC = bwareaopen(c,1000)
cNC = ~cNC;%reverse
cfinal = bwareaopen(cNC,1000);
imshow(cfinal);
se = strel('disk',3,8);
bwc = imclose(cfinal,se);
bwfinal = imopen(bwc,se);
L = bwlabel(cfinal);
stats = regionprops(L,'Area');
Area = [stats.Area];
Area = Area/1000;
Volume = .0297*Area^2+.177*Area-.0402
METHODOLOGY
0 5 10 15 20 25-5
0
5
10
15
20
25
30Calibration Curve
Projected Area (pixels*103)V
olum
e (m
icro
liter
s)
Courtesy of X. Chen Volume Calibration Curve
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EXPERIMENTAL RESULTS
0 0.5 1 1.5 2 2.50
0.5
1
1.5
2
2.5
3
3.5
4
4.5Droplet Volume v. Time
Time (minutes)
Dro
plet
Vol
ume
(mic
rolit
ers)
15 mmHg
20 mmHg
25 mmHg30 mmHg
35 mmHg
Droplet Volume v. Time
0 0.5 1 1.5 2 2.50
0.5
1
1.5
2
2.5Flow Rate v. Time
Time (minutes)
Flo
w R
ate
(mic
rolit
ers/
min
)
15 mmHg
20 mmHg
25 mmHg
30 mmHg
35 mmHg
V Flow Rate v. Time
𝑄=𝑑𝑉𝑑𝑡
=𝑎0+𝑎1𝑎2𝑒−𝑎2𝑡
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Experiment (mmHg)
(minutes)
15 3.5
20 2
25 1.8
30 1.8
35 3.9
INTERPRETATION
• τ, the time constant, is a parameter that describes the transient response of a system
Polyvas et al., 2012
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• 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
CONCLUSIONS
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ACKNOWLEDGEMENTS
• NASA Arizona Space Grant Consortium
• Mentor
• Dr. Eniko Enikov
• Students
• Peter Polyvas
• Marcel Madarasz
• Xiao Chen
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THANK YOU FOR YOUR ATTENTION