Alteration in disc diameter after DSAEK

Takefumi YAMAGUCHI, Yoshiyuki SATAKE, Seika DEN, Kenji KONOMI, Jun SHIMAZAKI Tokyo Dental College, Ichikawa General Hospital, Chiba, Japan The authors have no financial interest.

Introduction

Descemet’s stripping and automated endothelial keratoplasty (DSAEK) is treatment of first choice for bullous keratopathy. Total number of endothelial cells transplanted is important in maintaining sufficient number of endothelial cells after DSAEK. However, whether larger disc preferable remains unknown. If so, how large a disc can be safely transplanted? Herein we conducted the study on the disc structure after DSAEK.

Purpose

To evaluate alteration in disc diameter and structure after DSAEK.

Patients

This study comprised 15 eyes in 15 patients who underwent DSAEK at Tokyo Dental College Women: 12 eyes; Men: 3 eyes Age +/- SD: 69.3 +/-12.6 years Causes of bullous keratopathy (no.of eyes) Laser iridotomy: 7 Cataract surgery: 5 Fuchs’endothelial dystrophy: 2 Pseudoexfoliation syndrome: 1 Surgical technique (no. of eyes) DSAEK: 9 DSAEK+PEA+IOL: 5 DSAEK+TS IOL suturing: 1 (TS: transscleral) Disc diameter 8 mm: 14 (no. of eyes) 7.75 mm: 1

Graft preparation

All grafts were imported from Sight Life Eye Bank (Northwest) and prepared using Barron’s corneal punch during surgery.

Methods

  Data on disc diameter, central graft anterior chamber depth Tomey, Japan) at 1 and 3 months after DSAEK. #1 and central and peripheral graft thickness were obtained using anterior segment optical coherence tomography (AS-OCT, CASIA, SS-1000, Measurements were performed manually under refractive correction in 4 directions: horizontal, vertical, 45 and 135 degrees.

GD G-ACD #1 Graft anterior chamber depth (G-ACD) was defined as distance between apex of posterior surface of graft and line connecting inner graft edges.

Where large decentration of graft position was observed, data were excluded from study.

GD: Graft diameter, G-ACD: graft anterior chamber

Results

Visual acuity Endothelial cell count

2 3500 3000 1,5 2500 2000 1 1500 1000 0,5 500 0 0 Preop 1m 3m Preop 1m Graft anterior chamber(G-ACD)=1.50

± 0.19 μ m, Central graft thickness (CGT)=121 ± 30.1 μ m Peripheral graft thickness(PGT)=235 ± 101 μ m, Angle to angle distance (AD)=11.7

± 0.58 mm 3m

Average disc diameter

(mm) 8 7,8 7,6 7,4

Disc diameter shrank in all 4 directions (mm: no. of eyes out of 11 eyes

#1

): 0.10 < : 9 (81%) 0.25 < : 7 (64%) 0.40 < : 5 (46%)

#1 Number of patients on whom accurate data obtained in all 4 directions with no obstruction by lid or cilia.

Preop 1m Horizon tal Vertical 3m GD: Graft diameter

(135)

Effect of graft decentration

D

(horizontal)

B

(vertical)

A C θ oo’ = x (mm) B’

O:Measurement center

Possible measurement error caused by decentration from center of graft during measurement.

Distance between O and O’: x (mm) Largest amount of graft shrinkage in 4 directions: S (mm)

θ =

∠ O’OA S is maxim value if

θ

is 22.5

° If S is below 0.10 mm, x >0.12614 mm If S is below 0.25 mm, x > 0.3013 mm If S is below 0.40 mm, x > 0.462751mm (45)

C’ A’ D’

In measuring length and width, there is a high possibility that decentration will cause the graft to appear smaller than it actually is.

Taking measurements in all four directions lowers the margin of error.

1,8 2

Relation between GD and G-ACD

y = 0,2693x - 0,5641 R² = 0,1826 P=0.0012

1,6 1,4 1,2 1 6,5 7 7,5 GD 8 8,5 GD: Graft diameter, G-ACD: graft anterior chamber GD was significantly correlated with G-ACD. (Pearson’s correlation analysis).

This result indicates that G-ACD /GD ratio did not change in various eyes after DSAEK, which suggests the posterior surface curvature (flat or steep) did not influence the GD.

Is larger disc preferable?

Advantage

・ More endothelial cells can be transplanted.

Disadvantage

・ Possible decrease in endothelial cells due to manipulation of large disc during surgery.

However, there are two important PREMISES

① Graft size does not change after DSAEK. ⇒ Slightly shrinks ② Endothelial cells will distribute equally throughout host and graft surface.

Discussion

Endothelial cell loss after DSAEK has been reported to be 20-50%.

Area calculated from parameters of model eye

Posterior corneal surface(ACD2.8 mm): approx.110 mm 2 Posterior surface of disc of 8 mm: approx.55 mm 2 120 100 80 60 40 20 0 7 7,5 8 8,5 9 9,5 10 11 Disc diameter (2c) Area of posterior corneal surface S=π(c2+h2), c: radius, h: height, h=r-√r 2 -c surface, r = 6.8 mm 2 , r: curvature of posterior corneal

Discussion

If disc shrinks by around 0.25 mm after DSAEK, it might be possible to transplant larger disc or customize disc diameter using preoperative values of AS-OCT such as angle-to-angle distance or anterior chamber depth in each patient.

(We call this AS OCT-assisted DSAEK) If endothelial cells distribute equally on host and graft cornea after DSAEK, endothelial cell loss in previous studies can not be explained based on calculation of posterior surface area. It is possible that endothelial cell “privilege” in DSAEK graft prevents equal redistribution of endothelial cells after DSAEK. More comprehensive and long-term evaluation, including central and peripheral endothelial cell counts, graft edge configuration and chromosome assessment in graft and host cornea, will yield invaluable information on this issue.

Conclusion

 Disc diameter tended to shrink from 1 month after DSAEK, stabilizing at 3 months.

 In some patients, large alteration in disc diameter observed, suggesting larger disc is preferable in some cases. However, postoperative endothelial cell redistribution on host and graft cornea must be evaluated in future.