1. University of Texas Southwestern Medical Center at Dallas, Texas
Corneal Interface Morphology After Descemet Stripping Endothelial Keratoplasty by In Vivo Confocal Microscopy
Pawan Prasher, MD
Orkun Muftuoglu, MD
Marvin L. Hsiao, MD
W Matthew Petroll, Ph D
R. Wayne Bowman, MD
James P. McCulley, MD
V. Vinod Mootha, MD
University of Texas Southwestern Medical Center at Dallas, Texas

2. Introduction
Descemet stripping endothelial keratoplasty (DSEK) is a novel technique that allows selective replacement of dysfunctional corneal endothelium.
Despite favorable visual outcomes, fewer patients than expected achieve best corrected visual acuity (BCVA) of 20/20.
The probable factors limiting vision include interface (IF) haze, increased corneal thickness, subepithelial scarring,1and anatomical changes in the posterior corneal surface.

3. Purpose Materials and Methods
To study interface (IF) morphology by confocal microscopy in patients undergoing DSEK for corneal edema secondary to corneal endothelial cell dysfunction
Materials and Methods
Ten eyes of 10 patients with no associated ocular morbidity were assessed at 6 months post-op after DSEK surgery
All eyes underwent clinical examination, confocal microscopy and Pentacam densitometry measurement

4. Results Mean age was 63.3+/-8.4 years
No cornea had clinically significant IF haze on slit lamp examination
BCVA ranged from 20/20 to 20/50
On confocal microscopy, IF was indiscernible in 2/10 cases
IF was characterized by highly reflective particles in other (8/10) cases
No significant keratocyte activation was seen at IF in any case
The mean density of IF particles was 30.25±25.45 particles/mm2
The mean depth of IF was ±56.82µm and mean thickness of the endothelial graft was ±30.75µm
The mean measured IF reflectivity was 90.87±52.29 confocal back scatter units (CBU) which was significantly less compared to subepithelial reflectivity of 447±350.3 CBU (p=0.005)
Significant keratocyte activation with high reflectivity was seen in subepithelium or superficial stroma in 7/10 cases

5. Representative images of IF showing highly reflective particles of varying dimensions

6. Representative images of quiescent stroma without IF peak or particles

7. Representative images of keratocyte activation and increased reflectivity in anterior stroma

8. Representative Pentacam images showing characteristic peaks and particles at the level of IF
Peak corneal density was seen in anterior stroma in all cases IF particles were observed in 6/10 cases

9. Representative Pentacam images showing homogenous stroma without peaks or particles at the level of IF
The mean corneal density at the anterior stroma (41.53±12.61) was significantly higher than that of measured at the IF(26.38±7.33) (p=0.004).

10. Discussion
In vivo confocal microscopy has been widely used for the in vivo microscopic imaging of healthy and pathologic corneas, including after refractive surgery and lamellar transplants.2
Presence of reflective particles is one of the most consistent findings in studies involving confocal microscopy of the IF.
The exact nature and clinical consequences of IF particles are largely unknown. Various speculated sources include biologic debris from the ocular surface, powder from surgical gloves, remnants from industrial processing of the blade, and metal fragments from the steel blade and small plastic fragments generated by the metal and plastic interaction inside the oscillating microkeratome.3,4
Absence of significant haze or keratocyte activation after DSEK can be attributed to smoother IFs resulting from Descemet stripping in the host and microkeratome cut in the donor.
The measurements of significantly higher reflectivity (CBU) in the anterior stroma as compared to IF is consistent with previously reported findings in other types of posterior lamellar transplants,4 and may be attributed to preoperative subepithelial fibrosis.

11. Conclusions
The corneal stroma appears quiescent at the level of DSEK IF with minimal or no keratocyte activation.
In the anterior stroma, confocal microscopy showed increased reflectivity and Pentacam showed peak corneal density likely related to pre-operative subepithelial fibrosis
References
1. Price MO, Price FW. Descemet's stripping endothelial keratoplasty. Curr Opin Ophthalmol Jul;18(4):290-4.
2. Marchini G, Mastropasqua L, Pedrotti E, Nubile M, Ciancaglini M, Sbabo A. Deep lamellar keratoplasty by intracorneal dissection: a prospective clinical and confocal microscopic study. Ophthalmology Aug;113(8):
3. Ivarsen A, Thøgersen J, Keiding SR, Hjortdal JØ, Møller-Pedersen T. Plastic particles at the LASIK interface. Ophthalmology Jan;111(1):18-23.
4. Mootha VV, Dawson D, Kumar A, Gleiser J, Qualls C, Albert DM. Slitlamp, specular, and light microscopic findings of human donor corneas after laser-assisted in situ keratomileusis. Arch Ophthalmol May;122(5):686-92
5. Silvera DA, Fabrizio MJ, Goins KM. The Characterization of Interface Haze Following DLEK. IOVS 2007;48:ARVO E-Abstract 4715.