Ординатура / Офтальмология / Английские материалы / Jaypee Gold Standard Mini Atlas Series CORNEALTOPOGRAPHY_Agarwal, Jacob_2009

MINI ATLAS SERIES: CORNEAL TOPOGRAPHY

FIGURE 6.26: Steep keratometry on mean power map

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CHAPTER 6: THE ORBSCAN IIZ DIAGNOSTIC SYSTEM AND SWAGE

FIGURE 6.27: Preop patient with keratoconus

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MINI ATLAS SERIES: CORNEAL TOPOGRAPHY

FIGURE 6.28: Four months postop Lasik with KC

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CHAPTER 6: THE ORBSCAN IIZ DIAGNOSTIC SYSTEM AND SWAGE

FIGURE 6.29: 17 months postoperative Lasik

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MINI ATLAS SERIES: CORNEAL TOPOGRAPHY

FIGURE 6.30: Normal Orbscan

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CHAPTER 6: THE ORBSCAN IIZ DIAGNOSTIC SYSTEM AND SWAGE

FIGURE 6.31: Orbscan after 3 minutes of desiccation

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MINI ATLAS SERIES: CORNEAL TOPOGRAPHY

FIGURE 6.32: Keratoconus with normal pachymetry

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CHAPTER 6: THE ORBSCAN IIZ DIAGNOSTIC SYSTEM AND SWAGE

map, the thinnest spot of the cornea not being central and being greater than 30 microns thinner than the central reading, and the large amounts of irregularity in the central 3 mm and 5 mm zones. The final example is of pellucid marginal Degeneration (Fig. 6.33). Note the classic large amount of against the rule astigmatism, the large posterior float difference, the well-correlated anterior elevation abnormality, and the large amounts of irregularity in the central 3 mm and 5 mm zones.

ZYOPTIX

The Zyoptix wavefront diagnostic system version 2.38 is a Hartman-Schack wavefront aberrometer developed by Bausch and Lomb. This system is combined with the information obtained from the Orbscan to form the basis for wavefront-guided ablations through the Zylink platform and Technolas 21Z excimer laser.

The first step in any aberrometer is data acquisition. In the dual workstation system patient demographics are entered into the Orbscan, including manifest refraction, and this information is simply exported into the Zywave database. The current FDA indications are myopia less than 7.00 diopters and astigmatism less than 3.00 diopters. This information can be entered in plus or minus format and there is a quick conversion button on the Zywave screen.

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MINI ATLAS SERIES: CORNEAL TOPOGRAPHY

FIGURE 6.33: Pellucid marginal degeneration

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CHAPTER 6: THE ORBSCAN IIZ DIAGNOSTIC SYSTEM AND SWAGE

The patient status (i.e. pre-op dilated or undilated, postop, etc.) is entered and then testing can begin.

It is recommended that an undilated Zywave be taken and then an anterior segment exam is performed. The Zywave will use Hartman-Schack technology and its lenslet array to capture up to 9000 data points. These are then analyzed using Zernike polynomials and the data is displayed up to 5th order Zernike terms. It is crucial that the raw data received at this stage be verified for good quality before proceeding. The Zywave will obtain five scans and the best three sets of raw data will be automatically selected for analysis. The examiner needs to verify proper centration of the scans, good quality of the scans, and good accuracy of the scans before proceeding (Fig. 6.34). Centration of the Zywave scans is verified be looking at the three sets of raw data to see that the central "x" is near pupil center, and that the outer ring around the raw data is green. If it is not centered the outer ring will be yellow and the Zywave needs to be repeated (Fig. 6.35). The Zywave system comes with an alignment aid, which greatly improves the ease of acquisition and verification of centration. This aid has color bars and rings that change in size and color until optimally centered and crisp, and then the scan can be taken. The next item is to verify that the raw data is of good quality. The examiner must look at the three sets of raw data and see that all the centroids are

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