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Reinstein visumax
1. The Great Femtosecond Face-off: Carl Zeiss Meditec VisuMax Dan Z Reinstein MD MA(Cantab) FRCSC FRCOphth 1,2,3,4 1. London Vision Clinic, London, UK 2. St. Thomas’ Hospital - Kings College, London, UK 3. Weill Medical College of Cornell University, New York, 4. Centre Hospitalier National d’Ophtalmologie, (Pr. Laroche) , Paris, France
2. Financial Disclosure The author (DZ Reinstein) acknowledges a financial interest in Artemis™ VHF digital ultrasound ( ArcScan Inc , Morrison, CO) The author (DZ Reinstein) is a consultant for Carl Zeiss Meditec AG (Jena, Germany)
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10. Artemis B-Scan: 6 Months Post LASIK Artemis B-Scan (above) of VisuMax Flap 6 months post LASIK. Edge detection by I-scan digital signal processing (red outline, below) based on raw scan data
21. Validity of Measurement Instrument Artemis Flap Thickness Repeatability: 1.14 µm Therefore, the Artemis is capable of measuring a flap thickness reproducibility of 7.89 µm as found in this study
22. Validity of Measurement Instrument Artemis Flap Thickness Repeatability: 1.14 µm The Artemis is capable of measuring a flap thickness reproducibility as small as 3.42 µm
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25. IOP Comparison: VisuMax vs IntraLase Comparison of typical curves plotted on the same scale Ref: Grabner G. Femtosecond to fully replace microkeratome. Ophthalmology Times, 2008 0 50 100 150 200 250 300 350 0 20 40 60 80 100 time (sec) IOP (mmHg) IntraLase VisuMax
26. IOP Comparison: VisuMax vs IntraLase VisuMax flap creation time reduced to ~20 seconds with software v 2.4.0 Comparison of typical curves plotted on the same scale Ref: Grabner G. Femtosecond to fully replace microkeratome. Ophthalmology Times, 2008
55. Stability: Change in Spherical Equivalent Pre Op 1 Day 1 Month 3 Months 6 Months Avg SEQ -4.06 +0.37 -0.08 -0.15 -0.17 SD SEQ 1.85 0.36 0.43 0.42 0.41 # eyes 232 228 223 203 222
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58. The Great Femtosecond Face-off: Carl Zeiss Meditec VisuMax Dan Z Reinstein MD MA(Cantab) FRCSC FRCOphth 1,2,3,4 1. London Vision Clinic, London, UK 2. St. Thomas’ Hospital - Kings College, London, UK 3. Weill Medical College of Cornell University, New York, 4. Centre Hospitalier National d’Ophtalmologie, (Pr. Laroche) , Paris, France Thank You
I acknowledge a financial interest in the Artemis technology and am a consultant for Carl Zeiss Meditec
In order for the reproducibility results to be valid, the precision of the measuring instrument needs to be smaller than the reproducibility of the data set being measured.
For example, considering that 95% of measurements will be contained within a range of two standard deviations from the mean,
if an instrument with a precision of 1 µm were to be used to repeatedly measure the same flap, known to be exactly 110 µm in thickness, 95% of the measurements would fall between 108-112 µm (2 standard deviations from the mean).
On the other hand, if an instrument with a precision of 10 µm were to be used to repeatedly measure the same 110 micron flap, 95% of the measurements would fall between 90 and 130 µm.
Therefore, the validity of a flap thickness study is compromised if the precision of the measuring instrument is too large to be able to distinguish between two data points. And really, it’s the rule of 3 times – as 99.5% of data points are to be found within 3 standard deviations of the mean
For a claim of let’s say, a flap thickness reproducibility of 5 microns, the precision of the measuring tool needs to be at least half, …
preferably a third of 5 microns, or 1.66 microns.
So for example, the Artemis, with a 1.14 micron precision is perfectly capable of proving a flap thickness reproducibility of 7.89 microns
In fact, the Artemis, with a 1.14 micron precision, can be expected to distinguish flaps that are at least 3.42 microns different in thickness and therefore can legitimately be used to study the flap reproducibility of a system as long as the flap reproducibility is not better than 3.42 microns.
All experiments were performed in New zealand white rabbits of both sexes, anesthetized with PENTOPARBITAL. Since the laser doppler system is a sensitive motion detector the animals were paralysed with FLEXADIL to avoid measurement artefacts by movement. The rabbits were artificially respired. exspired CO2 levels were kept around 42 milimeters of mercury. body temperature was maintained by a heating pad. H ydrolic occluders were placed around the abdominal aorta and the inferior caval vein to manipulate mean arterial pressure and thereby change the perfusion pressure of the target tissue over a wide range. During the occlussion of the abdominal aorta blood flow to the lower half of the body is redirected to the upper half which increases blood pressure at the level of the ciliary body. During a caval occlusion venous return is decreased which in turn decreases blood pressure in the whole animal.
All experiments were performed in New zealand white rabbits of both sexes, anesthetized with PENTOPARBITAL. Since the laser doppler system is a sensitive motion detector the animals were paralysed with FLEXADIL to avoid measurement artefacts by movement. The rabbits were artificially respired. exspired CO2 levels were kept around 42 milimeters of mercury. body temperature was maintained by a heating pad. H ydrolic occluders were placed around the abdominal aorta and the inferior caval vein to manipulate mean arterial pressure and thereby change the perfusion pressure of the target tissue over a wide range. During the occlussion of the abdominal aorta blood flow to the lower half of the body is redirected to the upper half which increases blood pressure at the level of the ciliary body. During a caval occlusion venous return is decreased which in turn decreases blood pressure in the whole animal.
