Topographic characteristics after Descemet's membrane endothelial keratoplasty and Descemet's stripping automated endothelial keratoplasty

Abstract

Purpose: To investigate the topographic characteristics of the posterior corneal surface after Descemet's endothelial membrane keratoplasty (DMEK) and Descemet's stripping automated endothelial keratoplasty (DSAEK) and their effects on postoperative visual acuity.

Methods: Nineteen eyes of 19 patients after DMEK, 23 eyes of 23 patients after DSAEK, and 18 eyes of 18 control subjects were retrospectively analyzed. Best spectacle-corrected visual acuity (BSCVA), aberration factors (higher-order aberrations [HOAs], spherical aberrations [SAs], and coma aberrations [Comas] at 6.0 mm) were evaluated preoperatively and at 1, 3, and 6 months postoperatively. The posterior refractive pattern of the topography map was classified into 5 grades (0-5) (posterior color grade) using anterior segment optical coherence tomography. Correlations between BSCVA and some factors (abbreviation factors, posterior color grade) were analyzed.

Results: BSCVA was significantly better after DMEK than after DSAEK (P < 0.001). Posterior HOAs, SAs, and Comas after each type of endothelial keratoplasty were significantly greater compared to control (P < 0.01). Posterior HOAs, total/anterior/posterior SAs, and posterior color grade were significantly lower in the DMEK group than in the DSAEK group at 3 months (P < 0.024 [posterior HOAs], P = 0.047 [total SA], P < 0.001 [anterior SAs], P = 0.021 [posterior SAs], and P < 0.001 [posterior color grade]) and 6 months postoperatively (P = 0.034 [posterior HOAs], P < 0.001 [total SAs], P < 0.001 [anterior SAs], P = 0.013 [posterior SAs], and P = 0.004 [posterior color grade]). BSCVA was significantly correlated with HOAs, SAs, and posterior color grade (P < 0.001 for all except anterior HOAs [P = 0.004]).

Conclusions: High posterior color grades were associated with larger aberration factors and had a negative effect on visual function after endothelial keratoplasty. Rapid improvement of visual function after DMEK may be attributed to less change at the posterior surface.

Fig 1. A patient with poor visual acuity and high posterior color grade 3 months after DMEK.

(A) Slit-lamp photograph shows high transparency 3 months after DMEK. (B) Pachymetry after DMEK shows that the central corneal thickness is about 480 μm, which is considerably thinner than a healthy cornea. (C) Posterior map using AS-OCT after DMEK. Three months postoperatively, AS-OCT shows rapid improvement in corneal edema after DMEK. However, despite the clear cornea after DMEK, the visual acuity is 20/40. In this case, the posterior color grade is relatively high (grade 2). The figure demonstrates the characteristically irregular topography and increased irregular astigmatism at the posterior corneal surface in eyes with relatively poor visual acuity after DMEK. Abbreviations: AS-OCT, anterior segment optical coherence tomography; DMEK, Descemet’s endothelial membrane keratoplasty.

Fig 2. Posterior color grade after endothelial keratoplasty.

Using anterior segment optical coherence tomography (AS-OCT), the posterior classification is used to score the cornea from 0 to 5 points according to PRP.

1. (A) Grade 0: Background consists of “cool” colors (green or blue).

2. (B) Grade 1: Background is yellow.

3. (C) Grade 2: Background is orange and total area of red is < 1/4

4. (D) Grade 3: Background is orange and 1/4 < total area of red is < 1/2.

5. (E) Grade 4: Background is orange and total area of red is > 1/2.

6. (F) Grade 5: Background is red.

Fig 3. Comparison of BSCVA between DMEK and DSAEK.

A statistically significant improvement in BSCVA is obtained in each group (P < 0.001, Wilcoxon rank sum test). There is also a statistically significant difference in BSCVA between the two groups at all postoperative examinations (*P = 0.020, **P < 0.001, and **P < 0.001 at 1, 3, and 6 months, respectively; Mann–Whitney U test). Abbreviations: BSCVA, best spectacle-corrected visual acuity; DMEK, Descemet’s endothelial membrane keratoplasty; DSAEK, Descemet’s stripping automated endothelial keratoplasty.

Fig 4. Representative cases of slit-lamp microscopy and AS-OCT after endothelial keratoplasty.

(A) Slit-lamp photograph 6 months after DMEK. (B) Slit-lamp photograph 6 months after DSAEK. (C) AS-OCT section 6 months after DMEK. (D) AS-OCT section 6 months after DSAEK. (E) Posterior map using AS-OCT 6 months after DMEK. (F) Posterior map using AS-OCT 6 months after DSAEK. Postoperatively, a DMEK eye is difficult to distinguish from a normal eye after cataract surgery (A). However, we can see the scarring edge of the DSAEK graft (B). An AS-OCT section shows the natural posterior curvature in the DMEK eye (C), whereas the DSAEK eye has a meniscus-shaped posterior protrusion in the central cornea (D). The posterior color is cool in the DMEK eye (E), but red in the central cornea of the DSAEK eye (F). The arrows show the virtual peripheral edges of the DMEK and DSAEK grafts. Abbreviations: AS-OCT, anterior segment optical coherence tomography; DMEK, Descemet’s endothelial membrane keratoplasty; DSAEK, Descemet’s stripping automated endothelial keratoplasty.