1. CORNEAL EPITHELIAL IMAGING
Correlating Epithelial Mapping to Topography
Aleksandar Stojanovic, MD
SynsLaser Clinic, Oslo/Tromsø; University Hospital North Norway, Tromsø, Norway

2. Financial Disclosure
I have no financial interests or relationships to disclose.

3. Corneal Epithelium Features rapid cell-turnover
Highly reactive to irregularities in the underlying stroma
Always attempting to smoothen the ocular surface
Corneal Epithelium
-- Epithelial remodeling

4. Epithelial Remodeling
Anterior elevation map
(Impression after use of diamond burr)
Epithelial thickness
map
Anterior elevation map
(Cone)
Epithelial thickness
map
The presence of irregular anterior corneal surface implies an uneven epithelial thickness profile, so as to compensate for the even more irregular stromal surface.

5. Epithelial thickness distribution in keartoconus
Reinstein DZ et al. Corneal epithelial thickness profile in the diagnosis of keratoconus. J Refract Surg Jul;25(7):
Rocha KM et al. SD-OCT analysis of regional epithelial thickness profiles in keratoconus, postoperative corneal ectasia, and normal eyes. J Refract Surg Mar;29(3): doi: / X
Kanellopoulos AJ et al. Correlation between epithelial thickness in normal corneas, untreated ectatic corneas, and ectatic corneas previously treated with CXL; is overall epithelial thickness a very early ectasia prognostic factor? Clin Ophthalmol. 2012;6: doi: /OPTH.S Epub 2012 May 23.
Reinstein DZ et al. Epithelial, stromal, and total corneal thickness in keratoconus: three-dimensional display with artemis very-high frequency digital ultrasound. J Refract Surg Apr;26(4): doi: / X Epub 2010 Apr 7.

6. ? KC vs. Astigmatism Posterior elevation Anterior elevation
Anterior curvature
Epithelial map
Keratoconus ?
Astigmatism

7. Epithelial Thickness Distribution
-- Keratoconic Eyes vs. Healthy Eyes with Corneal Astigmatism ≥2 D

8. Patients and Methods Keratoconic eye group:
20 keratoconic eyes of 15 previously diagnosed patients
10 men and 5 women
Age: 28.5±6.5 years
Anterior corneal cylinder: 3.3±2.2 D
Krumeich scale stage I: 9 eyes; stage II: 7 eyes; stage III: 4 eyes
Healthy eye group:
20 healthy eyes of 15 patients with corneal astigmatism ≥2 D
8 men and 7 women
Age: 29.4±9.5 years (p= 0.54)
Anterior corneal cylinder: 3.6±1.2 D (p= 0.74)

9. SD-OCT Linear Scan Topography OCT image Keratoconic Eyes Healthy Eyes
The linear scans were performed on along the steepest and flattest meridians defined by corneal topography. The measurements were made at the corneal vertex, 1.5 mm and 2.5 mm away from the vertex along the steepest and flattest meridians. In the keratoconic eyes, the thinnest and thicknes epithelial thickness along the steepest meridian was measured as well.

10. Results: Epithelial thickness distribution
Location of the steepest meridian
Keratoconic eyes: 67.8±14.7°
Healthy eyes: 90.3±5.5°
Keratoconic eyes
Along the steepest meridian
Epithelial thinning inferotemporally (1.2 mm from the vertex) and thickening superanasally (1.4mm from the vertex)
Along the flattest meridian
Only small epithelial thickening centrifugally
Healthy astigmatic eyes
Only small deviations in the distribution along both the steepest and the flattest meridian

11. Results: Epi thickness distribution difference
Along the flattest meridian
No significant difference in epithelial thickness, except at the corneal vertex (thinner in KC-eyes).
Along the steepest meridian
Epithelium in KC-eyes was thinner inferiorly and at centrum and thicker superiorly with significant difference at all measurement points except 2.5 mm away from vertex

12. Results: Stromal thickness distribution
Keratoconic eye
Healthy eye
Along the steepest meridian
Along the flattest meridian
Stromal thinning over the cone in keratoconic eyes.
Generally thinner stroma in keratoconic eyes (more so temporally and inferiorly) compared to healthy eyes

13. Epithelial remodeling- Implications
Can compensate for the part of the irregularities caused by protrusion of the corneal stroma in keratoconic eyes
May make detection of mild keratoconus based on anterior corneal topography difficult
Forms a “concave epithelial lens” over the cone, adding negative refractive power to the cornea (refractive index is different in epithelium and stroma)
Should be taken into consideration in topography-guided surface ablation combined with CXL in treatment of keratoconus
The difference between stromal surface and epithelial surface

14. Conclusions
Both epithelium and stroma demonstrated thinning along the inferior part of the steepest meridian in keratoconic eyes, but not in healthy eyes with high corneal astigmatism.
Epithelium but not stroma demonstrated thickening along the superior part of the steepest meridian in keratoconic eyes, but not in healthy eyes with high corneal astigmatism.
Keratoconic eyes demonstrated more deviation in epithelial thickness distribution than healthy eyes with high corneal astigmatism.
Epithelial mapping by SD-OCT has the potential of becoming a part of the routine examination in diagnosis of early keratoconus.

15. Thank you!