Corneal imaging for undergraduate
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This document discusses the evolution of corneal imaging technologies from Maddox rod to Pentacam and various corneal topography devices. It provides details on Placido disc, IOL Master, Orbscan, topography, and Pentacam technologies. The document also examines the reliability of posterior corneal elevation topography measurements from Orbscan and Pentacam devices. Various corneal topography maps are explored including sagittal curvature, elevation, pachymetry, keratoconus, and Belin/Ambrosio enhanced ectasia displays. Guidelines for refractive surgery based on topography findings are provided along with case studies of keratoconus, abnormal cornea, and post-LASIK ectasia.
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Corneal imaging for undergraduate
- 1. By/Mohamed Ahmed El –Shafie Assistant lecturer in ophthalmology department Kafr ELShiekh University Corneal Imaging
- 2. EVOLUTION IN CORNEAL EVALUATION • MADDOX ROD • PLACIDO DISC • MANUAL KERATOMETER • VIDEO KERATOSCOPY • TOPOGRAPHY • ORBSCAN • PENTACAM • IOL MASTER
- 3. PLACIDO DISC
- 4. IOL MASTER
- 5. ORBSCAN
- 6. TOPOGRAPHY
- 7. 10/20/2019
- 8. Deptm. of Ophthalmology Ruprecht-Karls-University Heidelberg Chair: Prof. Dr. med. H.E.Völcker Reliability of Posterior Corneal Elevation Topography for Orbscan II and a Rotating Scheimpflug Camera M.S. Reuland, MD A.J. Reuland, MD T.M. Rabsilber, MD I.J. Limberger, MD G.U. Auffarth, MD Prof. Heidelberg IOL & refractive surgery research group www.lasik-hd.de mirjam.reuland@med.uni-heidelberg.de The authors have no financial interests in any of the products mentioned.
- 9. Results No difference in shape:61/63 (97%) 2 different shapes: 1/63 (2%) 3 different shapes: 1/63 (2%) No difference in shape:45/62 (73%) 2 different shapes: 15/62 (24%) 3 different shapes: 2/62 (3%) No difference in shape:29/62 (47%) Different shapes: 33/62 (53%) Comparison of shapes. When comparing the overall forms, again, a better repeatability was found for Pentacam (fig. 8) than for Orbscan (fig. 9). 27% of Orbscan measurements showed sometimes quite distinct differences in shape for repeated measurements. In direct comparison of Pentacam with Orbscan maps (fig. 10), only half the maps showed the same shape for both devices. Fig. 8: Patient 1 (OS): 3 repeated Pentacam measurements Fig. 9: Patient 2 (OS): 3 repeated Orbscan measurements Fig. 10: Patient 3 (OS): Pentacam (l) vs. Orbscan (r)
- 10. Common mistakes • Inadequate calibration • Technique – Unfocused eye piece – Distorted mires – Head tilt • Cornea problems – Lid/ lash interference – Dry eye – Excessive lacrimation – Eye ointments – Surface irregularities / scars
- 11. **Four-map composite report which includes sagittal curvature maps anterior elevation (front) posterior elevation (back) pachymetry or corneal thickness **Keratoconus Map **Belin /Ambrosio Enhanced Ectasia Display Rotating Scheimpflug Camera
- 12. 10/20/2019 ► Steep cornea:thin, irregular or buttonhole flaps **Ending with more than 48 cornea became very steep (prolate) negative spherical aberrations ►Flat cornea < 42 D : Free cap • In myopic ablation, look at flat K. Correction of –1 D reduces flat K by 0.80 D. • The final flat K should be > 34 D. **Ending with less than 34 dpt means that the cornea became very flat (oblate) positive spherical aberrations -In hyperopic ablation, look at steep K. Correction of +1 D increases steep K by 1.2 D. -The final steep K should be <49 D.
- 17. 10/20/2019 -Be careful when any value of the central 4 mm of the elevation maps is more than +15 μ for the anterior surface, and more than +20 μ for the posterior surface. - Be careful when the “back-front” difference is more than +5 μ at the same point. -Be careful when there is an isolated island on either surface.
- 18. Role of Cone on BFS In the case of keratoconus or ectasia, the cone or apical protrusion will have the effect of steepening the BFS. This stepened BFS will actually minimize the elevation difference between the apex of the cone and the BFS
- 19. Best Fit Sphere vs Toric Ellipse
- 21. 10/20/2019 ►Studying the Maps ►Corneal Thickness Map .
- 22. 10/20/2019 ►Topometric Map -Q-value shows the average vertical and horizontal values -The most important values are the vertical in general and the inferior in particular -The normal value is < -0.5 It is border line when it falls between -0.5 and -0.55. If the value is > -0.5 we should hesitate a lot before proceeding to the standard Lasik treatment The most important sector is the 6 mm or 20° sector.
- 23. 10/20/2019 ►Studying the Maps ►Keratoconus Indices Page -.
- 24. Belin /Ambrosio Enhanced Ectasia Display The goal of the Belin / Ambrósio Enhanced Ectasia Display is to combine elevation based and pachymetric corneal evaluation in an all inclusive display Elevation Subtraction Map
- 26. DECISION PRK NO RISK DO PRK OR LASIK
- 27. 10/20/2019
- 28. 10/20/2019 ►Cases study Case 1 The patient is 21-year-old male complaining of progressive reduction of visual acuity in both eyes. On doing corneal topography:
- 29. 10/20/2019 ►Cases study: Case 1 -.
- 37. 10/20/2019 ►Cases study Case 2 The female patient who is a chronic user of contact lenses and she stopped using the CL for more than one month. On doing corneal topography:
- 40. 10/20/2019 ►Cases study Case 2 1-very steep symmetric bow tie on the sagittal curvature map.
- 41. 10/20/2019 ►Cases study Case 2 2-Conic thickness map and much displaced thinnest location
- 42. 10/20/2019 ►Cases study Case 2 3-The elevation maps seem to be normal.
- 43. 10/20/2019 ►Cases study Case 2 3-The elevation maps seem to be normal.
- 47. 10/20/2019 ►Cases study Case 3 A 28-year-old female complaining of progressive reduction in her visual acuity (more severe in the left eye) since 3 years. Her history revealed Lasik treatment for myopia (6 years ago) for both eyes. Her exam was as follows:
- 56. 10/20/2019 • Discussion 1-The right eye of the patient is slightly ectatic; there is small amount of astigmatism, the best management in this case is to crosslink. Or at least, we have to observe the topography within 3 months. 2-The left eye is highly ectatic. So, is it better to do DALK, or to put rings and then do cross linking? the second decision will improve the irregularity of the cornea and will raise the cone towards the center of the cornea causing iatrogenic myopia and hence the need formore procedures such as phakic IOL.The first choice (DALK) is better.
- 57. 10/20/2019 Summary ►4 main maps give us an overview of the case, ►We should not end up with less than 34 dpt after treating myopia and not more than 48 dpt after treating hyperopia ►K readings should not be more than 47D ►Corneal astigmatism on either surface should not be higher than 6D. ►we must not ablate more than 20% of the original CT,and we must keep at least 55% of the CT as a residual stromal bed (RSB). ►After careful study of the topography, it is very important to score the case in order to exclude the risky cases
- 58. Mini Guideline 1- Thickness rules : - Don’t do any refractive surgery if less than 470 µm. - Don’t elevate corneal flap if less than 500≈495 µm. ( may do PRK or SMILE ) - Be carful if the cornea more than 600 µm. ( Fuchs dystrophy) - in LASIK follow PTA rule ( must be less than 40%)
- 59. Special thanks for Prof. dr. Mazen sinjab
- 60. 10/20/2019