Light and Electron Microscopic Analysis of Excised Human Descemet's Membrane Following Descemetorhexis with Endokeratoplasty

E. B. Price1, T. John1, K.R. Kenyon2,3 1Loyola University Medical Center, Maywood, Illinois; 2Harvard Medical School, Boston, Massachusetts

Introduction

References

Methods

Results

Conclusion

Descemetorhexis with endokeratoplasty (DXEK, Descemet’s stripping automated endothelial keratoplasty, DSAEK) has mostly become the treatment of choice for corneal endothelial diseases with endothelial decompensation. A better understanding of the plane at which tissue separation occurs will promote the advancement of the best possible posterior lamellar keratoplasty technique.

To measure the thickness of the DM, five photos were taken of each sample at 40x magnification and 10 thickness measurements were made on each photo using Scion Image software (Scion Corp., Frederick, MD).

Visual excrescences scores were assigned as follows:

1 = smooth surface2 = mild variability in sample

thickness (1-3 excrescences per high-power-field [hpf])

3 = moderate variability in sample thickness (4-6 excrescences per

hpf)4 = severe variability in sample

thickness (>6 excrescences per hpf)

Light and electron microscopic examination of all samples revealed no residual corneal stroma. The mean (SD) thickness of the DM was 18.09 (6.99) µm in the patient group and 11.27 (2.90) µm in the normal controls, with no statistical difference between groups (P = 0.19). Patient samples with smooth DM had a mean (SD) thickness of 14.27 (2.70) µm, while those with DM excrescences averaged 21.40 (7.93) µm thick. This difference was statistically significant (P < 0.01). When the level of excrescences on the visual rating scale was compared between the two groups,

Photo of all excised samples on light microscopy

Mean thickness of Descemet’s membrane (DM) in excised posterior lamellar tissue in patients (n = 28) and controls (n = 2). Bars indicate standard deviation.

Melles GRJ, Eggink FAGJ, Lander F, et al. A surgical technique for posterior lamellar keratoplasty. Cornea 1998;17:618.26.Melles GRJ, Wijdh RHJ, Nieuwendaal CP. A technique to excise the Descemet membrane from a recipient cornea

(descemetorhexis). Cornea 2004;23:286.288.Melles GRJ, San Ong T, Ververs B, et al. Descemet membrane endothelial keratoplasty (DMEK). Cornea 2006;25:987.990.Tappin M. A method for true endothelial cell (Tencell) transplantation using a custom made cannula for the treatment of endothelial

cell failure. Eye 2007;21:775.779.Melles GRJ, San Ong T, Ververs B, et al. Preliminary clinical results of Descemet membrane endothelial keratoplasty. Am J

Ophthalmol 2008;145:222.227.Shimmura S, Miyashita H, Konomi K, et al. Transplantation of corneal endothelium with Descemet's membrane using a hyroxyethyl

methacrylate polymer as a carrier. Br J Ophthalmol 2005;89:134.137.Ignacio TS, Nguyen TTB, Sarayba MA, et al. A technique to harvest Descemet's membrane with viable endothelial cells for selective

transplantation. Am J Ophthalmol 2005;139:325.330.Terry MA, Hoar KL, Wall J, et al. Histology of dislocations in endothelial keratoplasty (DSEK and DLEK): a laboratory based, surgical

solution to dislocation in 100 consecutive DSEK cases. 2006;25:926.932.Heindl LM, Hofmann-Rummelt C, Schlötzer-Schrehardt et al. Histologic analysis of Descemet stripping in posterior lamellar

keratoplasty. Arch Ophthalmol. 2008;126:461.464.Tillet CW. Posterior lamellar keratoplasty. Am J Ophthalmol. 1956;41:530.533.

Twenty-eight posterior lamellar recipient corneal samples were obtained from 27 DXEK patients through descemetorhexis and Descemet’s stripping with the John dexatome. Two samples from normal human donor eyes were also obtained as controls. All samples were examined using light microscopy and a representative sample was examined with transmission electron microscopy. All samples were evaluated for the presence of residual corneal stroma and the thickness of Descemet’s membrane (DM). Patient samples were also scored for the number of DM excrescences (guttata) per high power field.

Descemetorhexis and Descemet’s stripping, performed in the present study with the John dexatome, produce a smooth separation of DM from the posterior stroma. As there was no recipient stromal loss, we presume the posterior stromal surface to be smooth. This information is encouraging because it reinforces that tissue separation occurs at the plane that we intend it to be for DXEK.

To evaluate the efficacy of descemetorhexis and Descemet’s stripping at producing a smooth recipient stromal surface in the context of descemetorhexis with endokeratoplasty.

Table 1. Tissue characteristics

Figure 2. DM thickness in patients and controls

Figure 3. DM thickness in smooth and excrescences samples

the ranked mean (SD) of the excrescences samples (n = 15) was 3.33 (0.82), versus 1 (0) for the smooth samples (n = 13). This difference was also statistically significant (P < 0.01).

758M (Control #1) 9.22 1.06758N (Control #2) 13.32 1.00758P 53 F 11.53 1.02758V 74 F 11.67 1.04758O 41 M 11.95 1.44758Z 77 M 12.27 1.18758T 85 F 12.37 0.71758U 81 F 12.94 1.61758AA 78 M 13.20 0.78758I 86 F 13.42 1.33758L 90 M 13.47 2.96758G 77 F 13.78 1.10758CC 83 F 14.43 1.06758S 91 F 15.38 1.89758Y 73 M 16.88 2.32758J 77 M 17.57 1.17758H 79 M 17.61 3.77758W 77 M 17.79 4.55758X 77 F 17.90 4.52758D 98 F 18.84 1.97758R 58 F 19.06 2.42758B 84 F 19.38 0.76758C 70 M 19.87 1.37758K 80 F 20.18 4.77758BB 77 F 20.31 3.61758F 67 F 20.80 5.37758E 76 F 23.72 2.57758DD 73 F 24.15 5.22758Q 88 F 30.62 5.94758A 64 F 45.46 4.38

Experimental ID Number

Patient Age

Patient Sex

Descemet's Membrane, mean (μm) SD (μm)

      

Research supported by the Richard A. Perritt Charitable Foundation

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SmoothMean thickness of Descemet’s membrane (DM)

in excised posterior lamellar tissue in smooth DM patient samples (n = 13) and excrescences DM patient samples (n = 15). Bars indicate standard deviation.

Figure 4. Visual excrescences score in smooth and excrescences samples

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Mean visual excrescences score in excised posterior lamellar tissue in smooth DM patient samples (n = 13) and excrescences DM patient samples (n = 15). Bars indicate standard deviation.

Excrescences

SmoothObjective