1. LSU Eye Center, New Orleans, LA
Robinson v. Grendahl
LASIK on keratoconus
Stephen D. Klyce, Ph.D.
LSU Eye Center, New Orleans, LA

2. ANATOMY OF THE EYE Corneal Layers Normal cornea: prolate shaped
> 20% thinner in the center than the periphery
Corneal Layers

3. OPTICS OF THE EYE
Figure 1A. Light rays from a point source an infinite distance away travel as a plane wave. This can be altered by turbulence in the atmosphere. The optics of the eye curve the wavefront to focus images on the retina. A. Diagram of an eye with excellent optics.

4. Abnormal corneal shape distorts vision
OPTICS OF THE EYE
Abnormal corneal shape distorts vision

5. ABERRATIONS REDUCE VISION
Normal
Mild KC
Moderate KC
20/16
20/25
20/32-1

6. CORNEAL TOPOGRAPHER

8. Different topographers Large target, coarse mire
Cone target, fine mire
Large target, coarse mire

9. Different topographers Large target, coarse mire
Cone target, fine mire
Large target, coarse mire

10. Different topographers, similar result

11. NORMAL CORNEAL TOPOGRAPHY
Average corneal power 40.7 – 46.5 diopters.
Uniform central corneal powers with regular contours and flattening toward the periphery.
Often a symmetrical bow tie pattern is present, an indication of natural astigmatism.

12. NORMAL

13. CORNEAL ASTIGMATISM

14. ABNORMAL CORNEAL TOPOGRAPHY
Corneal diseases produce abnormal topography and reduce vision.
Examples of pathology:
Keratoconus and Keratoconus Suspect
Pellucid Marginal Degeneration
Basement Membrane Dystrophy

15. PELLUCID MARGINAL DEGENERATION
Typical

16. KERATOCONUS
Keratoconus describes a condition of the cornea that causes thinning and protrusion.
Diagnosis is by observation of corneal steepening on corneal topography (usually inferior), corneal thinning, and certain biomicroscope findings.
Treatment: when eye glasses or contact lenses no longer provide good vision, a corneal transplant may be recommended.

17. ADVANCED KERATOCONUS

18. KERATOCONUS

19. KERATOCONUS DEVELOPMENT OVER 6 YEARS

20. KERATOCONUS SUSPECT
Keratoconus suspect describes a condition of the cornea that may lead to keratoconus with thinning and protrusion.
Identification is by observation of a subtle localized corneal steepening on corneal topography; this may be accompanied by findings on retinoscopy.
Management: repeat eye exams every 6 months to a year to watch for progression to keratoconus.

21. Keratoconus Suspect

22. Keratoconus Suspect

23. Keratoconus Suspect

24. MANUAL PRE-OPERATIVE SCREENING
VERTICAL POWER GRADIENT (I-S, RABINOWITZ, 1989)
> 1.4 D = KCS OR ABNORMAL > 1.9 D = KC OR ABNORMAL

25. + I will show you the specifications for the ARK-10000.
The ARK is unique from other conventional AR and CT’s in that we measure four zones from 2.3mm to 5.5 mm in diameter.
We measure 1440 points in less than 0.4 seconds.

26. Δ = 1.58 D possible KCS +
I will show you the specifications for the ARK
The ARK is unique from other conventional AR and CT’s in that we measure four zones from 2.3mm to 5.5 mm in diameter.
We measure 1440 points in less than 0.4 seconds.

27. REFRACTIVE SURGERY COMPLICATIONS
Kerectasia: protrusion of the cornea following refractive surgery. Associated with:
Pre-operative signs of keratoconus
Too thin a residual stromal bed thickness.
Poor vision
Irregular astigmatism from LASIK flap complications (for example: button hole, free cap, partial flap).
Dry eye.

28. LASIK ON KCS Pre-op 3 mon 18 mon
I will show you the specifications for the ARK
The ARK is unique from other conventional AR and CT’s in that we measure four zones from 2.3mm to 5.5 mm in diameter.
We measure 1440 points in less than 0.4 seconds.

29. Basement membrane dystrophy

30. DALE ROBINSON PRE-OPERATIVE SUMMARY
Normal corneal findings:
Pre-operative average corneal power was within the range for normals (40.7 – 46.5 diopters).
Central corneal thicknesses (on calibrated Orbscan II 555, 538 microns) within normal range.

31. DALE ROBINSON PRE-OPERATIVE SUMMARY
Abnormal corneal findings:
Topography:
Central corneal powers were not uniform, but exhibited a localized, inferior area of corneal steepening, a classic sign of keratoconus.
The gradient in corneal power was 8 D in the left eye and 6 D in the right eye, % greater than the Rabinowitz criterion (>1.9 D).
Pachymetry
18 Micron difference in thickness between right and left eyes.
Thin inferior corneas. %

32. ORIGINAL ORBSCAN PRINTOUT
Inferior steepening

33. ORIGINAL ORBSCAN PRINTOUT
Inferior steepening

34. THICKNESS CORRECTED ORBSCAN
The corrected Orbscan is compensated for calibration error in the pachymetry. Our LSU unit has been calibrated properly.
Inferior steepening

35. THICKNESS CORRECTED ORBSCAN
Inferior steepening

36. DALE ROBINSON SUMMARY FINDINGS
Dale Robinson was not a good candidate for LASIK surgery.
Pre-operative corneal topography revealed the presence of keratoconus in both eyes.
When LASIK is performed on eyes with keratoconus, the eyes are at risk for keratectasia which severely impairs vision and often leads to corneal transplantation.
The standard LASIK procedure is a contraindicated in patients with keratoconus.