Publications
News
The FAT1 device was cleared by the Food and Drug Administration on 01/15/2016 for market introduction with the following indications for use: Tonometry, Ocular Pulse Amplitude, Tonography and Ophthalmodynamometry.
Publications
Association for Research and Vision in Ophthalmology April 2nd, 2010.
Abstract Title: The Effects of Intravitreal Anti-VEGF Injections in Ocular Perfusion Pressure
Authors: Elias Reichel, Heeral Shah, Tufts University New England Eye Center
Citation: Reichel E, Shah H. The Effects of Intravitreal Anti-VEGF Injections on Ocular Perfusion Pressure. Invest Ophthalmol Vis Sci. 2010;51:5032.
Keywords: Age Related Macular Degeneration, anti-VEGF, Ocular Perfusion Pressure, Intraocular Pressure.
Purpose: Blood flow into the eye is determined by the ocular perfusion pressure (OPP). OPP is the difference between the mean central artery pressure (MCRAP) and the intraocular pressure (IOP),(OPP = MCRAP – IOP).1 Intraocular anti-VEGF injections can raise intraocular pressure and decrease retinal blood flow.2 The aim of this study was to investigate the effect that intraocular anti-VEGF injections have on ocular perfusion pressure.
Methods: The OPP, MCRAP, IOP and Ocular Pulse Amplitude (OPA) was measured using the Falck Medical Multifunction Applanation Tonometer (FAT1) in twenty eyes of twenty patients immediately pre and post anti-VEGF injection. The mean upright ipsilateral brachial blood pressure (MBBP) was also recorded. The independent-samples t-test was used to analyze the pre and post injection differences. Twelve eyes received Avastin and eight eyes Lucentis. All eyes received 0.5mg.
Results: The cohort mean age and MBBP was 75.1+/- 19 years and 93.45 +/-11 mmHg. The mean decrease in MCRAP post-injection was 10.3 mmHg, p = 0.03 (45–34.7). The mean increase in IOP post-injection was 10.8 mmHg, p = 0.0002 (28.5–17.7). The mean decrease in OPP post-injection was 11.9 mmHg, p = 0.003 (27.3-15.4). The mean decrease in OPA post-injection was 0.5 mmHg, p = 0.03 (2.3-1.8). In twelve eyes the post-injection OPP decreased due to both an increase in IOP and a decrease in MCRAP. In two eyes the post injection OPP decreased to zero from both an increase in IOP and a decrease in MCRAP.
1 Kaufman PL, Alm A. Adlers Physiology of the Eye. Tenth Edition 2003;764-67.
2 Papadopoulou DN, Medrinos E, Mangioris G, et al. Intravitreal ranibizumab may induce retinal arteriolar vasoconstriction in patients with neovascular age-related macular degeneration. Ophthalmology.2009;116:1755-61.
Clinical and Manometric Comparison of The Falck Autotonometer and The Goldmann Tonometer. Association for Research in Vision and Ophthalmology, April 27th, 2008. F. Y. Falck, R. Falck.; University of Connecticut School of Medicine, Farmington, CT.
Purpose: In recent clinical studies the Goldmann tonometer has been found to lack accuracy where the corneal thickness varies from the calibration standard of 0.5 mm (1). If the corneal thickness is less then 0.5 mm the intraocular pressure will be underestimated possibly leading to a false negative diagnostic impression and if the corneal thickness is greater then 0.5 mm the intraocular pressure will be overestimated possibly leading to a false positive diagnostic interpretation. The greater the deviation of thickness from the mean the greater the over or underestimation of intraocular pressure (2). Corneal curvature may also effect the accuracy of the Goldmann. The smaller the corneal radius the greater the resistance to flattening. Thus, steeper corneas may lead to an overestimation of intraocular pressure with the Goldmann and flatter corneas may lead to an underestimation (3).
Additionally, there are also concerns about transmission of infectious agents with reusable applanation tonometry prisms or tips (4).
The Autotonometer is an automated electro-optical microprocessor driven tonometer that performs multiple applanations in an average measurement time of 0.5 seconds. The eye pressure is digitally displayed and retained in memory for recall. The device compensates for corneal thickness and curvature and can be used portably or on the slit-lamp microscope. A small plastic disposable applanation prism prevents spread of infection. Fluorescein is not required.
This study was undertaken to determine the accuracy of the Autotonometer manometrically and clinically as compared to the Goldmannn tonometer.
Methods: Eye bank eyes were pressurized using saline to a known value in a range of 5 to 60 mmHg with a digital manometer (Bio-Tek Instruments, INC., Winooski, VT.). Calibration of the digital manometer was verified with a u-tube mercury manometer. The Autotonometer applanation force was then recorded at 5 mmHg intervals from 5 to 45 mmHg. Multiple readings at each point were obtained.
In the clinical comparison trials 95 eyes were enrolled. The intraocular pressure was measured in an alternating sequence of the Goldmann followed by recording the Autotonometer applanation force and then in reverse for the next study eye.
Linear regression analysis was performed.
Results: In the manometric eye bank studies a perfect correlation (r = 0.99, y = – 0.51 + 0.3 x) was found with the Autotonometer over an intraocular pressure range of 5 to 45 mmHg (Figure 1). In the comparison clinical trials the correlation between the
Autotonometer and the Goldmann tonometer was 0.88 (y = – 6.79 + 0.73 x) over a range of 8 to 62 mmHg (Figure 2).
Figure 1: Autotonometer Manometric Eye Bank Experiment
Figure 2: Clinical Comparison of Autotonometer and The Goldmann Tonometer
Conclusions: The Autotonometer produced accurate and repeatable applanation force measurements that correlated in a perfect linear relationship with manometric intraocular pressure. Additionally, a strong correlation was found with Goldmann estimates of eye pressure. Some of the variability found between the Goldmann and the Autotonometer is most likely related to the subjective measurement error associated with the Goldmann. The Autotonometer is objective and requires minimal operator skill. Other probable sources of variability would be variations in corneal thickness and curvature in the clinical study eyes. The Autotonometer compensates for the effect of corneal thickness and curvature while the Goldmann tonometer does not. Additional clinical and laboratory studies are ongoing.
References:
Goldmann H, Schmidt T. Uber Applanationstonometrie.
Ophthalmologie 1957;134:221-42.
Shah S, Chatterjee A, Mathai M, et al. Relationship between Corneal Thickness and Measured Intraocular Pressure in a General Ophthalmology Clinic. Ophthalmology 1999;106:2154-2160.
Woo S, Kobayashi A, Lawrence C, et al. Mathematical Model of the
Corneo-Scleral Shell As Applied to Intraocular Pressure-Volume Relations and Applanation Tonometry. Ann Biomed Eng 1972;1:87-98.
CDC. Recommendations for Preventing Possible Transmission of Human T-Lymphotrophic Virus Type 3/Lymphadenopathy- Associated Virus from Tears. MMWR 1985;34:533-534.
CR:P
Agency for Healthcare Research and Quality: Comparative Effectiveness of Screening for Glaucoma. January 10, 2011.
Clinical Comparison of FAT1 and Goldmann Applanation Tonometer.
Introduction:
The Falck Medical Multifunction Device (FAT1) measures intraocular pressure (IOP) using the same method of applanation (Imbert-Fick Law) as the Goldmann Applanation Tonometer (GAT). The GAT IOP measurement does not correct for the variation in corneal biomechanics or for the variation of IOP with the cardiac cycle. The pulsating mires of the GAT are evidence of the increase in IOP during systole.1 The FAT1 measurement corrects for the variation in corneal biomechanics and measures the variation of IOP with the cardiac cycle.
The GAT takes only one subjective user dependent measurement. So, it is not possible to know the accuracy and precision of the measurement.1 The FAT1 captures a measurement every 7 milliseconds over multiple cardiac cycles. The measurement is objective, no mire alignment and user independent. Measurement data captured by the FAT1 is statistically analyzed for precision and accuracy. The Mean IOP, % Variation, the IOP Variation with the Cardiac Cycle (OPA) and the Number of IOP Measurements Captured (N) are displayed. The data is saved to a secure electronic file.2
The GAT prism cannot be sterilized and therefore there is a risk of transmission of infectious disease agents that are present in the tears.1 The FAT1 has a fixed used disposable prism that blocks infectious disease transmission.2
The FAT1 Device also measures Conventional Outflow Facility (Tonography).2 Impaired outflow is the primary cause of glaucoma.3
The FAT1 also measures Mean Central Retinal Artery Pressure (MCRAP) (Ophthalmodynamometry).2 MCRAP and IOP is used to calculate Ocular Perfusion Pressure (OPP) (OPP = MCRAP – IOP). OPP is the net force that drives blood flow into the eye.4
The purpose of the FDA Clinical Study was to evaluate the precision and accuracy of the FAT1 IOP measurement as compared to the GAT.
Methods:
The FAT1 device clinical study was a single site investigator study with external auditing oversight by the United States Food and Drug Administration (FDA) and an Independent Contract Review Organization (CRO). Data analysis was provided by the CRO and the FDA. One hundred twenty-five subjects and 209 eyes were coded by numeric ID and entered into a secure electronic data base for final analysis. The FAT1 was connected directly to the electronic data base. Measurement data from the FAT1 electronically went directly into each subject file. Data from the GAT, pachymetry and keratometry measurements were manually entered. Sixty-one eyes underwent pachymetry and keratometry measurements.
The measurement sequence was randomized with the first ten eyes measured by the FAT1 first and the next ten eyes measured by the GAT first. This randomization sequence was maintained throughout the study. Two FAT1 devices (FAT1A and FAT1B) were used in the study. All study data went directly into an electronic study file. Once entered the data was secure and could not be changed.
The FAT1 device automatically calibrates before any measurement. The GAT was manually calibrated before each measurement.
The study subject age range was 24 to 94 years. One-third of study eyes were either ocular hypertensive or had glaucoma. The study was carried out in accordance with the FDA Guidance for Tonometers, as published March 27th, 2006.
Subjects were screened for established inclusion and exclusion criteria. If found eligible, each study subject signed an informed consent document prior to participation. The study was designed as a one-time exposure to the FAT1 and GAT. All measurements were taken by two ophthalmic technicians who were trained in the use of the FAT1 and the GAT. The clinical study was conducted in accordance with the abbreviated rules for investigational device exemptions within the meaning of 21 CFR Part 812.2(b) and for the rights and protections of investigational subjects in accordance with 21 CFR Part 50 – Informed Consent; and 21 CFR Part 56 – Institutional Review Board Regulations. Full approval to conduct the study was awarded on November 1, 2006.
Study Subject Characteristics:
One hundred twenty-five subjects (209 eyes) were enrolled. Overall accountability at the end of the study was 100%. There were no withdrawals. One hundred forty-eight eyes were considered normal, and 61 eyes were considered ocular hypertensive or glaucomatous. In normal subjects the range of IOP was 9 to 21 mmHg. In glaucoma subjects the range of IOP was 10 to 56 mmHg. The overall age range was 24 to 94 years. There were 71 males and 54 males enrolled in the study.
Adverse Events:
No adverse events were reported during the course of the clinical study.
Safety:
The results of all study subjects were considered for the safety evaluation. No complications were reported during the clinical study.
Incident Report:
During the clinical study, one subject was found to have a large disparity of Mean Central Retinal Artery Pressure (MCRAP) between the two eyes. MCRAP was reduced in the left eye. The disparity led the principal investigator to refer the subject for emergency admission to the local medical facility. Diagnostic imaging confirmed the presence of an internal carotid artery aneurysm on the left side. The subject was treated and is doing well. This is not considered an adverse event. Enrollment in the study likely saved the subjects life. The subject was excluded from the data analysis.
Results:
See Scatter Plot Figure 1A. The FAT1 measured IOP value is plotted on the x-axis and the GAT IOP on the y-axis. The regression line, the equation and the r-squared value is displayed. The maximum r-squared value is 1. The higher the number, the greater the strength of the relationship. The r-squared value is 0.925.
See Bland – Altmann Plot Figure 2A. The paired difference between the reference GAT and the FAT1 is plotted on the y-axis and the mean of the GAT and FAT1 is plotted on the x-axis. The mean and + / – 1.96 standard deviation is displayed. The average mean difference is 0.7 mmHg.
See Table 1 – Number and Percent of Paired Differences That Exceed Tolerance by each Pressure range
A tabulation of the number of eyes and percent of paired differences (GAT – FAT) that exceeds the tolerance limit of 5 mmHg for each pressure range as described in ANSI Z80.10 – 2003 is provided. In this comparison zero % of the paired differences exceeded the tolerance limit for an IOP range of 7 to 16 mmHg, 2.9 % for an IOP range of >16 to 23 mm Hg, and 5.41% for an IOP greater than 23 mmHg.
In the IOP range > than 23 mmHg, eight of these eyes had a corneal thickness of 595 to 625 microns. The GAT reading in these eyes was on average 7.4 + / – 1.2 mm Hg higher than the FAT1 reading. It is well established in the literature that the GAT will overestimate the IOP when the corneal thickness is greater than 500 microns.5
Correcting the GAT reading using a published nomogram of delta IOP = (-0.0423 x CCT) + 23.38 decreased the number of eyes above the tolerance limit in the > 23 mmHg group of eyes.
See Figure 3 and 4. Regression of FAT1 Readings and Corneal Thickness and Curvature. The FAT1 readings are plotted on the y-axis and corneal thickness and curvature are plotted on the x-axis. The r-squared value for FAT1 versus Corneal Thickness is 0.06. The r-squared value for Corneal Curvature is 0.04. The low correlation coefficients confirm that the FAT1 readings are independent of corneal thickness and curvature.
See Distribution and Randomness Test, T-Test and Wilcoxon Rank Sum Test. Study Bias Evaluation. The output from the FAT1 device is independent of the user. During the study the data went directly into an electronic secure file. GAT data was manually put into each file. The testing sequence was randomized. The first ten eyes were tested with the FAT1 first. The next ten eyes with the GAT first. If the FAT1 was first, the FAT1 data went into the file first. If the GAT was first the data was entered into the file first and the FAT1 data electronically went into the file second. Once the data is in the file it cannot be changed. One hundred seven eyes were tested with the FAT1 first and 98 eyes were tested with the GAT first. There was no statistically significant difference between the measurement results and the testing sequence. No user, study or measurement bias was found.
Conclusion:
The accuracy, precision, repeatability and safety of the FAT1 device is confirmed. The FAT1 device measurements are user independent and independent of corneal biomechanics. The FAT1 device measures the variation of IOP with the cardiac cycle and incorporates this data into the displayed IOP. All data is statistically analyzed for precision and accuracy. Data capture is rapid at 0.7 milliseconds. The fixed use disposable prism is an absolute barrier to infectious disease transmission which is a risk with existing tonometer technology.
References:
Goldmann H, Schmidt T. Uber Applanationstonometric Ophthalmologic. 1957;134:221-242.
FDA510k141591
Chandler and Grant’s Glaucoma. David Epstein, Rand Allingham, Joel Schuman. Fourth Edition. 1997. Practical Aqueous Humor Dynamics, pp19-20. Tonometry and Tonography, pp 43-44.
Adler’s Physiology of the Eye. Clinical Application. Paul Kaufman, Albert Alm. Tenth Edition. 2003. Circulation, pp 764-767.
Ehlers N, et al. Applanation Tonometry and Central Corneal Thickness. ACTA Ophthalmologica. Vol 53. 1953.
Kohlhaas M, et al. Arch Ophthal. Vol 24. April 2006.
Agency for Healthcare Research and Quality. Comparative Effectiveness of Screening for Glaucoma. January 10, 2011.
Clinical Comparison of FAT1 to Calibrated Weight Indentation Tonography.
Introduction:
The Falck Medical, Inc. FAT1 device measures intraocular pressure (IOP), ocular pulsatile amplitude (OPA), the force required for pulsation of the central retinal artery (ophthalmodynamometry-OPH) and aqueous outflow (tonography – TON). The device was cleared for these Indications of Use under FDA510k151491. The primary cause of glaucoma is impaired outflow of aqueous humor 1. All current standard of care pharmacological and surgical treatments of glaucoma are designed to increase aqueous humor outflow. Thus, it is important to be able to measure outflow facility to determine therapeutic efficacy. Measuring IOP is not an accurate assessment of therapeutic response2. Aqueous humor production and IOP vary diurnally3. In glaucomatous and normal eyes, there is no scientific evidence that aqueous humor outflow (Tonography) varies diurnally1,2.
The FAT1 device uses the method of tonography to measure conventional outflow facility. During tonography, the force applied, corneal indentation and applanation area are monitored and recorded by the microprocessor and the optical system. Actively recording and monitoring force application, corneal indentation and applanation area is a significant improvement over existing indentation tonographers. The FAT1 device also monitors central corneal contact. The only skill required by the technician or doctor is to initially place the
prism in central contact with the cornea. The measurement process is initiated with central cornea contact. The measurement is automated and independent of the user.
Three individual IOP measurements consisting of multiple samples obtained every 7 milliseconds are used to calculate an average IOP measurement. For example, an individual average IOP reading of 16 mmHg consists of approximately 60 samples. Within each individual IOP measurement, the samples are analyzed for repeatability and accuracy (Step 1 analysis). If acceptable an average IOP is calculated. In Step 2 analysis each individual average IOP measurement is analyzed for repeatability and accuracy. The maximum allowable variation for Step 1 and 2 analyses is 10%. Step 1 and Step 2 analysis criteria must be met, otherwise the FAT1 device will prompt for a repeat measurement. The same process is used to evaluate applanation area, force application and corneal indentation. Acceptable measurements are displayed on the CDU with percent variation. Using this process, measurement is user independent.
The FAT1 device uses a fixed use disposable prism that is an absolute barrier to the transmission of infectious disease which is an issue with other devices.
Methods:
The FDA 510k FAT1 Indentation Tonography clinical study was a single site, single investigator, blinded prospective Institutional Review Board approved study. Study oversight and monitoring was provided by an external Contract Review Organization (CRO) and the FDA. Study data analysis was done by the FDA and an independent CRO. The CRO statistical group was blinded to which participant was in the glaucoma group versus the normal group. Ninety-one subjects and ninety-one eyes were enrolled into the study. The ninety-one subjects (eyes) were coded by a numeric ID and entered into a secure electronic data base. All measurement output went into this secure electronic database. All measurements were performed by two trained ophthalmic technicians. Two different FAT1 (FAT1A, FAT1B) devices were used in the study for comparison to the Model 30. Before each measurement the FAT1 device performs a calibration routine. All FAT1 devices calibrate to the same internal standards. The Model 30 was calibrated before each use according to the user instruction manual. None of the devices used in the study failed calibration at any time.
Two groups of eyes were enrolled for the study. In Group A, sixty-one eyes with a diagnosis of glaucoma (open angle or closed angle) or ocular hypertension were enrolled. The criteria for the diagnosis of glaucoma was glaucomatous nerve fiber layer defects documented by computerized tomography (Heidelberg Retinal Tomograph, HRT2), glaucomatous visual field defects documented by computerized visual field testing (Zeiss Humphrey 30-2 Program) and a history of elevated IOP (>24 mmHg). Additionally, for the diagnosis of closed angle glaucoma, on direct gonioscopy the drainage angle was closed. For the diagnosis of ocular hypertension, the eye enrolled had an IOP greater than 24 mmHg without any glaucomatous findings. Thirty eyes had open angle glaucoma, eight eyes had angle closure glaucoma and twenty-three eyes had ocular hypertension.
The average age of Group A subjects was 65.7 +/- 13.0 years and the average age of Group B subjects was 64.3 +/- 8.7 years which was not statistically significantly different, p = 0.60. In Group A there were 38 females and 23 males. In Group B there were 24 females and 6 males.
The measurement sequence FAT1 versus Model 30 changed every five eyes. Intra-visit FAT1 variability, inter-visit FAT1 variability and FAT1A and FAT1B intra-visit variability analysis was performed. Operator effect was also analyzed. External independent statistical analysis was provided by Synectechs, Inc., who was blinded as to which was the normal group and which was the glaucoma group. All eyes were used in the analysis. There were no screen failures, no loss to follow-up and no adverse events.
The clinical study was conducted in accordance with the abbreviated rules for investigational device exemptions within the meaning of 21 CFR Part 812.2(b), with the rights and protections of investigational subjects in accordance with 21 CFR Part 50-Informed Consent and 21 CFR Part 56-Instituitional Review Board
Regulations. Instituitional Review Board approval was granted on February 16th, 2010. For further protocol details see Section 14.4.
Results:
In Group A, on computerized visual field testing the average pattern standard
deviation defect was 3.67 +/- 4.1 db, range 1.1 to 20 db and the average mean defect was – 3.0 +/- 3.6 db, range –15.4 to 1.2 db. The average IOP (Po) was
20.02 +/- 5.5 mmHg with a range of 12.9 to 42 mmHg. The average outflow facility (C) was 0.09 +/- 0.05 ul/minute with a range of 0.01 to 0.22 ul/minute.
In Group B the documented IOP was consistently less than or equal to 24 mmHg and none of the thirty eyes enrolled had no examination findings consistent with the diagnosis of glaucoma. Additionally, none of the subjects had any known glaucoma risk factors. Thirty eyes were enrolled in Group B. The average IOP (Po)
was 18.7 +/- 2.4 mmHg with a range of 14.6 to 24 mmHg. The average outflow facility (C) was 0.31 +/- 0.12 ul/minute with a range of 0.16 to 0.6 ul/minute.
Two repeat measurements on each of the ninety-one subject eyes were taken with the FAT1 device for a total of 182 outflow facility measurements. Sixty measurements were in the low outflow range of 0.01 to 0.095, sixty-one in the
middle range of 0.10 to 0.17 and sixty-one in the high range of 0.18 to 0.6 ul/minute.
The difference in IOP and outflow facility between Group A and Group B was statistically significant, 20.02 +/- 5.5 vs. 18.7 +/- 2.4 mmHg, p=0.0221 and 0.09 +/ – 0.05 vs. 0.31 +/- 0.12 ul/minute, p < 0.0001.
Intra-visit Variability Analysis:
Two separate repeat IOP (Po) and outflow facility (C) measurements were obtained with the FAT1 device during the same visit. There was no statistically significant difference between the first measurement versus the second measurement for IOP and outflow facility, 18.65 +/- 2.46 vs. 18.62 +/- 2.40 mmHg, p = 0.95; 0.31 +/- 0.12 vs. 0.31 +/- 0.12 ul/minute, p=0.99, n=60.
Inter-visit Variability Analysis:
At the initial visit and at the follow-up visit within six weeks, the IOP (Po) and
outflow facility (C) was measured with the FAT1 device. The operator was blinded to the first visit results. There was no statistically significant difference between the first visit measurement versus the second visit measurement of IOP and outflow facility, 18.66 +/- 2.40 vs. 18.60 +/- 2.46 mmHg, p=0.90;0.31 +/- 0.12 vs. 0.30 +/- 0.12 ul/min, p=0.64, n=60.
Testing Sequence Analysis, FAT1 and Model 30:
The testing sequence, FAT1 versus the Model 30 changed every five eyes. Distribution and randomness testing of the IOP (Po) and outflow facility(C) measurement difference between the FAT1 and the Model 30 and the testing sequence was carried out using the Wilcoxon test. The mean difference between the FAT1 and the Model 30 and the testing sequence for IOP was 0.0009 mm Hg and for outflow facility was 0.0007 ul/min-mmHg. The difference between the IOP and outflow facility measurement obtained with the FAT1 device versus the Model 30 and the testing sequence was not statistically significantly different, p = 0.61 and 0.86 for the Wilcoxon two-sided test (n=182).
Mean Measurement Difference between the Two Devices:
The mean measurement difference between the Model 30-IT and the FAT1 for IOP (Po) was -0.21 mmHg and for outflow facility (C) was -0.006 ul/minute for Group A (n=122), and 0.005 mmHg and -0.001 ul/minute for Group B (n=60).
Ninety-three % and 96% of the Group A paired differences for IOP and outflow facility respectively, are within +/- 1.96 standard deviations of the mean difference. For Group B, 97% and 93% of the paired differences for IOP and outflow facility respectively, are within +/- 1.96 standard deviations of the mean difference. Please see the Bland –Altman data plots (Figures 2a) in Section 14.3.
Mean Measurement Difference between Group A and Group B:
The mean measurement difference for IOP (Po) and outflow facility (C) was compared for Group A versus Group B using the FAT1 and Model 30. For the FAT1 device, the measurement difference for IOP (Po) and outflow facility (C) was statistically significantly different between Group A and Group B. Group A IOP was 20.02 +/- 5.5 mmHg and Group B IOP was 18.6 +/- 2.4 mmHg, p =0.0221 (unequal variance). Group A IOP range was 12.9 to 42 mmHg. Group B IOP range was 14.6 to 24 mmHg. Group A outflow facility was 0.09 +/-0.05 ul/minute and Group B outflow facility was 0.31 +/- 0.12 ul/minute, p < 0.0001. Group A outflow facility range was 0.01 to 0.22 ul/minute. Group B outflow facility range was 0.16 to 0.6 ul/minute.
For the Model 30 device, the measurement difference for IOP (Po) and outflow facility (C) was statistically significantly different between Group A and Group B. Group A IOP was 19.8 +/- 5.7 mmHg and Group B IOP was 18.7 +/- 1.9, p = 0.047 (unequal variance). Group A IOP range was 14 to 46 mmHg. Group B IOP range was 15 to 22 mmHg. Group A outflow facility was 0.08 +/- 0.04 ul/minute and Group B outflow facility was 0.31 +/- 0.12 ul/minute, p < 0.0001. Group A outflow facility range was 0 to 0.21 ul/minute. Group B outflow facility range was 0.16 to 0.6 ul/minute.
Correlation:
The correlation between IOP (Po) and outflow facility (C) measurements obtained with the FAT1 versus the Model 30 was studied using linear regression analysis. For Group A the linear correlation coefficient was 0.88 for IOP and 0.77 for outflow facility. The null hypothesis that the slope was zero is rejected, p < 0.0001. For Group B the linear correlation coefficient was 0.69 for IOP and 0.97 for outflow facility. The null hypothesis that the slope is zero is rejected, p< 0.0001. See Figures 1a in Section 14.3.
Precision Analysis:
1. Operator plus the Device
The effect of different operators (operator 1 vs. 2) with the same FAT1 device with the same eye was evaluated for IOP (Po) and outflow facility (C) using ANOVA. No significant operator effect was found for IOP (p= 1.0) or outflow facility (p= 0.99).
2. Same Operator with Different Devices
The effect of different devices, FAT1A versus FAT1B, with the same operator and the same eye was examined for the measurement of IOP (Po) and outflow facility (C) using ANOVA. No significant device effect was found for IOP (p=0.96) or outflow facility (p=0.94).
3. Replicate Analysis, Same Operator, Same Device
The repeat measurement difference for IOP (Po) and outflow facility (C) with the same operator, same FAT1 device and same eye was examined using ANOVA. No significant repeat measurement difference was found for IOP (p=0.95) or outflow facility (p=0.99).
Conclusion:
The clinical study results demonstrate the safety, precision, accuracy and repeatability of the FAT1 device. The ability of the FAT1 device to discriminate between glaucomatous and non-glaucomatous eyes is also demonstrated. The clinical study confirms the relationship between the severity of glaucoma and impaired outflow facility. Eyes with advanced glaucoma had Outflow Values of less than 0.09 ul/mmHg and eyes with moderate glaucoma had outflow values of 0.10 to 0.17 ul/mmHg.
References:
Becker-Shaffers Diagnosis and Therapy of the Glaucomas. H. Dunbar Hoskins, Michael Kass. Sixth Edition. 1989. Aqueous Humor Dynamics, pp 52-53.
Chandler and Grant’s Glaucoma. David L. Epstein, Rand Allingham, Joel S. Schuman. Fourth Edition. 1997. Aqueous Humor Dynamics, pp19. Tonometry and Tonography , pp 43-44.
Adler’s Physiology of the Eye. Clinical Application. Paul Kaufman, Albert Alm. Tenth Edition. 2003. Aqueous Humor Hydrodynamics, pp 237-289.
Presentations
Falck FY, Falck R. Clinical and Manometric Comparison of The Falck Autotonometer and The
Goldmann Tonometer. Annual Meeting of the Association for Research in Vision and
Ophthalmology (ARVO). 2008 Apr 27; Fort Lauderdale, Florida.
Falck FY, Falck R. Clinical Comparison of FAT1 to Calibrated Weight Indentation Tonography.
Annual Meeting of the Association for Research in Vision and Ophthalmology (ARVO). 2011 Jan
10; Fort Lauderdale, Florida.