Nomogram to Predict Graft Thickness in Descemet Stripping Automated Endothelial Keratoplasty: An Eye Bank Study

The predictability of graft thickness for Descemet's stripping automated endothelial keratoplasty using a mechanical microkeratome system

Descemet's stripping automated endothelial keratoplasty (DSAEK) is used for treating corneal endothelial dysfunction, and the postoperative visual acuity outcome depends on the thickness of the graft. We created a simple nomogram using factors affecting the cutting thickness during graft preparation via a mechanical microkeratome system for DSAEK. This retrospective study was conducted from May 2018 through October 2022 and included donor eyes cut by automatic methods. We measured the graft thickness, cutting accuracy, and assessed ten variables with donor/cornea-related factors potentially affecting the cutting thickness. Subsequently, we created a simple nomogram. We analyzed 81 donor tissues, and the donor median age was 76 years. The mean central graft thickness was 122.2 μm, with 62% of the grafts that could be cut within the target central graft thickness range. Comparatively, donor corneas from those with cardiac diseases were cut deeper (P = 0.007). The developed nomogram provided a 83% probability of estimating the post-cutting graft thickness within 25 µm. Our nomogram, which considers cause of death, enables reproducible production of graft of a desired thickness. A detailed analysis of donor tissues, including the cause of donor death and the characteristics from pressurization to cutting, will enable more precise DSAEK graft preparation.

Nomogram for single-pass automated microkeratome graft preparation for ultrathin Descemet stripping automated endothelial keratoplasty

PURPOSE

To create a nomogram including the translational speed of the microkeratome blade, microkeratome head size and precut tissue thickness to predict the postcut thickness for Descemet stripping automated endothelial keratoplasty to obtain the thinnest possible graft.

METHODS

This prospective study incorporated 48 grafts for DSAEK from March 2017 to June 2020. Corneal tissue for DSAEK was prepared by 3 experienced physicians using the Moria Evolution 3E (Moria Inc, Antony, France) microkeratome with 400, 450 and 500 μm head sizes. Precut central corneal thickness was measured with a DGH 550 handheld pachymeter (Pachette 2), taking an average of 3 readings. The microkeratome head was selected according to precut tissue thickness. The selected microkeratome head size was 150 μm less than the donor cornea thickness. Two translational speeds were used for the microkeratome cuts. One month after surgery, the central lenticular thickness was measured with a Visante® Optical Coherence Tomography caliper (Carl Zeiss Meditec Inc, Germany). A descriptive analysis was performed.

RESULTS

Forty-eight donor grafts were prepared. Mean graft thickness was 97.58 ± 29.84 μm (range 39-176 μm). Of the 48 samples, central graft thickness was < 120 µm (81.3%) in 39, < 100 µm (58.3%) in 28 and < 80 µm (37.5%) in 18 at 1-month follow-up. There were no statically significant differences between translational speeds.

CONCLUSIONS

A nomogram with an automated microkeratome to obtain thin grafts for DSAEK provided good graft thickness results without donor waste.

Development of a Nomogram to Predict Graft Survival After Penetrating Keratoplasty

PURPOSE

To develop a nomogram to predict the 3- and 5-year likelihood of graft survival after penetrating keratoplasty (PK) based on preoperative assessment and intraoperative plan.

DESIGN

Retrospective clinical case-control study.

METHODS

Data from 1,029 consecutive PKs in 903 eyes of 835 patients performed at a single tertiary center from May 2007 to September 2018 were extracted from electronic medical records and evaluated for corneal graft failure, defined as irreversible and visually significant graft edema, haze, or scarring. Thirty-seven variables were assessed by multivariable Cox models. A nomogram to predict the probability of graft survival was created.

RESULTS

Mean recipient age was 57.1 ± 22.0 years and mean follow-up was 4.22 ± 3.05 years. Overall, 37.4% of grafts failed during follow-up. Eleven variables were significantly associated with graft failure, including active microbial infection at the time of PK (hazard ratio [HR] = 5.10, 95% confidence interval [CI] 3.53-7.37), intraocular silicone oil at the conclusion of the PK (HR = 4.28, 95% CI 2.38-7.71), history of systemic autoimmune disease (HR = 2.83, 95% CI 1.63-4.90), 4 quadrants of corneal neovascularization (HR = 2.76, 95% CI 1.56-4.86), any prior anterior segment surgery (HR = 2.41, 95% CI 1.55-3.75), and lens status as anterior chamber intraocular lens at the conclusion of surgery (HR = 2.35, 95% CI 1.30-4.26). The nomogram exhibited a concordance index of 0.76 (95% CI 0.74-0.78); internal calibration plots depicted strong correlation between prediction and observation of graft survival.

CONCLUSIONS

PK graft prognosis may be predicted relatively accurately based on 11 variables. Although established from retrospective data, this nomogram would be valuable for data-driven patient counseling prior to corneal transplantation.