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. Author manuscript; available in PMC: 2022 Sep 21.
Published in final edited form as: Cornea. 2019 Apr;38(4):426–432. doi: 10.1097/ICO.0000000000001846

Comparison of Donor Cornea Endothelial Cell Density Determined by Eye Banks and by a Central Reading Center in the Cornea Preservation Time Study

Beth Ann Benetz *,†, Christopher G Stoeger ‡, Sanjay V Patel §, Robert C O’Brien , Loretta B Szczotka-Flynn *, Allison R Ayala , Maureen G Maguire ‖, Harry J Menegay *,†, Peter Bedard **, Jameson M Clover ‡, Pankaj C Gupta *,††, Kristen E McCoy ‡‡, Jonathan C Song §§, Jonathan H Lass *,††, on behalf of the Cornea Preservation Time Study Group
PMCID: PMC9490486  NIHMSID: NIHMS1834893  PMID: 30664048

Abstract

Purpose:

To evaluate agreement between eye banks (EBs) and a reading center on endothelial cell density (ECD) determinations in the Cornea Preservation Time Study.

Methods:

The Cornea Image Analysis Reading Center (CIARC) performed variable frame image analysis on EB-obtained–preoperative central endothelial images (after lamellar dissection for Descemet stripping automated endothelial keratoplasty by the EBs or before shipping, if surgeon prepared) to determine ECD. The EBs performed their usual method of ECD determination. The CIARC and EBs also provided ECD determinations from screening central endothelial images taken by the EBs during donor evaluation. Two independent masked CIARC readers determined ECD with measurements averaged.

Results:

The mean preoperative ECD was 15 cells/mm2 greater by the EBs than by CIARC (N = 1286, P < 0.001) with 95% limits of agreement of (−644, 675 cells/mm2). The limits of agreement in preoperative ECD were wider in the After-Lamellar-Dissection Group (−687, 683 cells/mm2) than in the Before Shipping Group [(−505, 633 cells/mm2); P = 0.03]. The EBs-determined preoperative ECD was within 10% of the CIARC-determined ECD for 886 (69%) image sets, with 236 (18%) higher by >10% and 164 (13%) lower by >10%. Excellent agreement appeared between the EBs and CIARC when 100–300 cells could be analyzed in contrast to <100 cells (SD = 308 cells/mm2 vs. SD = 603 cells/mm2; P < 0.001).

Conclusions:

The mean ECD by the EBs and CIARC were similar, but there was considerable variability between determinations for individual corneas. Agreement improved between the 2 measurements when more than 100 cells were able to be analyzed.

Keywords: specular microscopy, endothelial keratoplasty, reading center

Corneal endothelial cell density (ECD), as determined from specular microscopic images, has been recognized as an indirect measure of corneal donor health for more than 40 years1 and has been one of the factors that has been used to predict the outcome of penetrating2–7 and endothelial keratoplasty.8–10 Previous studies have shown the variability of image quality and other factors affecting accurate ECD determination,11–21 which could be accentuated in a large multi-eye bank and clinical sites trial. To minimize errors, the value of a central image analysis reading center to ensure standardized assessment of ECD has been previously demonstrated in the Specular Microscopy Ancillary Study (SMAS).2–4,22–24 To validate the ECD of the donor central endothelium determined by the eye bank (EB) for entry into the study (≥2300 cells/mm2), the SMAS conducted a comparative study of this screening ECD determined by the EBs versus the central image analysis reading center, the Cornea Image Analysis Reading Center (CIARC, Cleveland, OH) and how accuracy was influenced by image quality.22 In the SMAS, the mean EBs-determined screening ECD was 100 cells/mm2 higher than that of the CIARC with less agreement as the image quality worsened.

The Cornea Preservation Time Study (CPTS) was a randomized clinical trial on the effects of preservation time (PT) on graft success and endothelial cell loss after Descemet stripping automated endothelial keratoplasty (DSAEK) involving 1330 donor corneas from 23 EBs.25–27 Influenced by the SMAS findings,22 CIARC developed a detailed imaging protocol and designed training and certification procedures to improve endothelial image quality across all EBs.25 This article examines the performance of the CPTS EBs compared with that of the CIARC in the determination of preoperative ECD after lamellar dissection for eye bank-prepared lenticules and before shipping for surgeon-prepared lenticules. Also, to examine the effect of PT on ECD, the preoperative ECDs were compared with the ECD at the time of screening of the donor.

MATERIALS AND METHODS

Details of the CPTS protocol have been previously reported.25 The protocol was approved by institutional review boards governing each investigational site, and individual participants gave written informed consent to participate in the study. Study oversight was provided by an independent data and safety monitoring committee. The research adhered to the tenets of the Declaration of Helsinki. The protocol was registered and is publicly available at https://clinicaltrials.gov/ct2/show/NCT01537393.

Participants were enrolled at 40 clinical sites and donor corneas were provided by 23 EBs.25 Eyes undergoing DSAEK were randomly assigned to receive a donor cornea with PT of 0 to 7 days or 8 to 14 days. The 1330 eyes completing surgery with a CPTS-assigned cornea were considered the “study eyes.” Assigned corneas were from donors 12 to 75 years old (median age 61 years) with a central ECD measured by each study EB at the time of screening of at least 2300 cells/mm2. Surgeons either received the lenticule after EB-prepared lamellar dissection or had donor tissue shipped for surgeon preparation at the time of DSAEK.

Donor Endothelial Imaging and Image Analysis

The CIARC served as the central image analysis reading center to determine ECD and was also responsible for quality control measures at the EBs and clinical sites. Each specular microscope [HAI Laboratories Inc, Boston, MA (n = 7); Konan Medical Inc, Irvine, CA (n = 32)] at each study EB underwent a prestudy calibration process; at sites with multiple instruments, each was calibrated. In addition, any replacement microscope during the study was certified before use in the study. All personnel at each EB capturing preoperative images also were trained and certified to obtain good to excellent image quality by the CIARC.

The EB obtained 1 to 3 specular image(s) of the central donor corneal endothelium on screening after their usual procedure of warming the donor tissue to room temperature and then determined the ECD by their usual image analysis method.24 These technicians were not required to be CPTS certified, but had undergone specular microscopy training by their EB. This assessment was not standardized, because it was performed at a time when the EB did not yet know that the donor cornea would be assigned to a CPTS recipient. If a donor cornea was assigned to the CPTS, the EB also obtained 3 “preoperative” study images of the central endothelium performed by only CPTS-certified technicians either after lamellar dissection (“After-Lamellar-Dissection Group”), or, if the donor cornea was to be prepared by the surgeon, before shipment (“Before Shipping Group”). Before preoperative images were obtained, the donor cornea was again allowed to warm to room temperature so that the best quality images could be obtained.28,29 The EBs determined ECD on these preoperative images with the center method on 1111 (84%) image sets, with the variable frame method on 165 (12%) image sets, and with the fixed frame method on 54 (4%) image sets.24

ECD Determination

Preoperative and screening donor images were evaluated for quality and ECD by the CIARC. Details of CIARC procedures have been previously described, including reader training and certification, image quality grading, image calibration, variable frame analysis for ECD determination, and adjudication procedures for image quality and ECD determination.2,22,23,25,26 Briefly, the image quality was assessed as analyzable or nonanalyzable by 2 independent readers and determined by a third adjudicator when either reader found the quality to be nonanalyzable. The ECD of all analyzable images was independently determined by 2 readers using the variable frame analysis method where the reader counts cells within an outlined area of a group of cells,24 as in the SMAS.23 This method was selected for the CPTS so that the maximal number of available cells with clear centers and borders could be analyzed. If the ECDs determined by the 2 readers differed by ≥5.0%, a third independent determination of ECD was made by an adjudicator. Final ECD was the average of all ECDs that were within 5% of each other. Readers were masked to all information about the donor corneas and study participants. Throughout the study, the CPTS Data Management and Analysis Center (Jaeb Center for Health Research, Tampa, FL) selected preoperative EB images and other postoperative time points for repeat, masked image quality grading and ECD determination to assess both intraobserver and interobserver variability (see Supplemental Table 1, Supplemental Digital Content 1, http://links.lww.com/ICO/A733). From these quality image sets, the 2 readers were <5% apart in their preoperative ECD determination 80% of the time.

Statistical Methods

Difference plots for the CIARC- and EBs-determined ECD values were constructed according to the method of Bland and Altman, where the limits of agreement are defined as mean (EBs ECD–CIARC ECD) ± 2 SD (EBs ECD–CIARC ECD). Nonparametric Wilcoxon signed-rank tests were used to compare ECD determinations of the same donor cornea because of outliers in the data. The association between change from screening to preoperative ECD and PT subgroups (ie, 0–4, 5–7, 8–11, and 12–14 days) was evaluated by the Kruskal–Wallis test. Equality of the variances of differences in ECD values between groups of corneas based on type of readers, number of cells per image set, or timing of preoperative evaluation was assessed using the Levene test.30,31 P values were 2-tailed and variables with P ≥ 0.05 were not considered statistically significant. Statistical analyses were conducted using SAS software (version 9.4; SAS Inc, Cary, NC) and R version 3.4.

RESULTS

Of the 1330 donors, 1313 preoperative image sets were submitted to the CIARC, whereas 17 (1.0%) were not available for analysis (see Supplemental Figure 1, Supplemental Digital Content 2, http://links.lww.com/ICO/A734). Only 27 of the 1313 preoperative image sets (2%) were deemed unanalyzable by the CIARC. Because the EBs were not required to save their screening images for subsequent analysis by the CIARC, 999 of the 1330 screening image sets (75%) were available for ECD determination by both EB and CIARC. The donor baseline characteristics of the 25% of screening image sets for which CIARC values could not be determined were similar to the characteristics of those with CIARC-determined values (data not shown). Only 15 of these 999 screening image sets (2%) were deemed unanalyzable by the CIARC. When the determinations of the first and second CIARC readers of 1276 preoperative images were compared, the mean difference in ECD was 40 cells/mm2 (SD = 180) with 95% limits of agreement of [−320, 400]. ECD for the 2 readers was within <5% for 862 (66%) of the preoperative image sets (see Supplemental Figure 1, Supplemental Digital Content 2, http://links.lww.com/ICO/A734), and thus these image sets were not adjudicated.

Preoperative ECD Comparison

The means and SDs for preoperative ECD as determined by the EBs and CIARC, and also their difference, are shown in Table 1. Among 1286 corneas with both EBs- and CIARC-determined preoperative ECD, the mean (SD) ECD was 2773 cells/mm2 (±300 cells/mm2) by the EBs and 2758 cells/mm2 (±388 cells/mm2) by the CIARC. Bland–Altman analysis (Figure 1) showed that the mean difference between the EBs and CIARC ECD was 15 cells/mm2 with 95% limits of agreement of [−644, 675 cells/mm2] (EBs mean > CIARC mean; P <0.001). Variability of differences from the same cornea between the EB (using their standard methods) and CIARC (calculated average from 3 images dual graded and adjudicated) (SD = 330 cells/mm2) was higher than the variability of differences between CIARC readers (SD = 180 cells/mm2; P < 0.001). The variability among the preoperative image sets where an average of 100 to 300 individual cells per image set were analyzed (N = 699) was significantly lower than the variability of the image sets where <100 individual cells were analyzed (N = 92) (SD = 308 cells/mm2 vs. SD = 603 cells/mm2; P < 0.001), and the variability where >300 individual cells were analyzed (N = 495) was lowest of all (SD = 260 cells/mm2 vs. SD = 308 cells/mm2; P = 0.04). Because lower variability leads to tighter limits of agreement, it follows that there was much greater agreement between the EBs and CIARC when at least 100 cells could be analyzed (see Supplemental Figures 2A, 2B, and 2C, Supplemental Digital Contents 3–5, http://links.lww.com/ICO/A735, http://links.lww.com/ICO/A736, and http://links.lww.com/ICO/A737). Finally, the EBs-determined ECD was within 10% of the CIARC-determined ECD for 886 (69%) of the preoperative image sets (Table 1). The EBs ECD was >10% higher than the CIARC ECD in 236 (18%) determinations and was >10% lower in 164 (13%). The EBs-determined preoperative ECD was within 5% of the CIARC-determined ECD (the difference beyond which CIARC would adjudicate ECD between readers) for 571 (44%) of the preoperative image sets. The EBs ECD was >5% higher than the CIARC ECD in 412 (32%) determinations and was >5% lower in 303 (24%).

TABLE 1.

EB and CIARC Screening and Preoperative ECD Among Corneas With Determinations From Both EB and CIARC

Screening—All Donor Corneas, N = 984 Preoperative—All Donor Corneas, N = 1286 Preoperative—After Dissection, N = 952 Preoperative—Before Shipping, N = 334
ECD (Cells/mm2) Mean (SD) Mean (SD) Mean (SD) Mean (SD)
EB-determined 2744 (303) 2773 (300) 2767 (304) 2792 (288)
CIARC-determined 2636 (323) 2758 (388) 2769 (407) 2728 (329)
Difference limits of agreement 108 (259)
[−410, 626]		 15 (330)
[−644, 675]		 −2 (343)
[−687, 683]		 64 (285)
[−505, 633]
Screening—All Donor Corneas, N = 984 Preoperative—All Donor Corneas, N = 1286 Preoperative—After Dissection, N = 952 Preoperative—Before Shipping, N = 334
Image Sets, n (%)* Mean (SD) Mean (SD) Mean (SD) Mean (SD)
EB > 10% lower 56 (6%) 164 (13%) 141 (15%) 23 (7%)
EB > 10% higher 237 (24%) 236 (18%) 168 (18%) 68 (20%)
Within 10% 691 (70%) 886 (69%) 643 (68%) 243 (73%)
EB > 5% lower 136 (14%) 303 (24%) 246 (26%) 57 (17%)
EB > 5% higher 395 (40%) 412 (32%) 299 (31%) 113 (34%)
Within 5% 453 (46%) 571 (44%) 407 (43%) 164 (49%)
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*

May not add up to exactly 100% because of rounding.

FIGURE 1.

FIGURE 1.

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Bland–Altman plot of EB versus CIARC preoperative ECD (N = 1286). Bland–Altman plot of central ECDs (cells/mm2) determined by study EBs versus the ECDs determined by the CIARC. The difference in ECDs is plotted against their average value.

After-Lamellar-Dissection and Before Shipping Comparison

Among the 952 corneas in the After-Lamellar-Dissection Group, the mean difference between EBs- and CIARC-determined ECD was −2 cells/mm2 with 95% limits of agreement of [−687, 683 cells/mm2] [EBs mean ≈ CIARC mean; P = 0.14] (Table 1; see Supplemental Figure 3A, Supplemental Digital Content 6, http://links.lww.com/ICO/A738). Among the 334 corneas in the Before Shipping Group, the mean difference between EBs- and CIARC-determined ECD was 64 cells/mm2 with 95% limits of agreement of [−505, 633 cells/mm2] [EBs mean > CIARC mean; P <0.001] (see Supplemental Figure 3B, Supplemental Digital Content 7, http://links.lww.com/ICO/A739). The variability of the differences in preoperative ECD was greater in the After-Lamellar-Dissection Group (SD = 343 cells/mm2) than in the Before Shipping Group (SD = 285 cells/mm2) (P = 0.03).

Screening ECD Comparison

Among 984 corneas with both EBs- and CIARC-determined screening ECD, the mean (±SD) ECD was 2744 cells/mm2 (±303 cells/mm2) by the EBs and 2636 cells/mm2 (±323 cells/mm2) by the CIARC. Bland–Altman analysis (Figure 2) showed that the mean difference between the EBs and CIARC ECD was 108 cells/mm2 with 95% limits of agreement of [−410, 626 cells/mm2] (EB mean > CIARC mean; P <0.001). The EBs-determined ECD was within 10% of the CIARC-determined ECD for 691 (70%) of the screening image sets. The EBs ECD was >10% higher than the CIARC ECD in 237 (24%) determinations and >10% lower in 56 (6%).

FIGURE 2.

FIGURE 2.

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Bland–Altman plot of EB versus CIARC screening ECD (N = 984). Bland–Altman plot of central ECDs (cells/mm2) determined by study EBs versus the ECDs determined by the CIARC. The difference in ECDs is plotted against their average value. Only donor corneas with EB screening ECD ≥2300 cells/mm2 were included in the CPTS. This constraint on the EB screening ECD implies that the Y ≥ 4600–2X, where Y is the difference (EB–CIARC) and X is the average of EB and CIARC ECD.

Comparison of Screening to Preoperative ECD

Table 2 lists the change in ECD from the screening to the preoperative image. There was an increase from screening to preoperative ECD for both EBs (34 cells/mm2) and CIARC (124 cells/mm2) (P < 0.001 for both). The mean difference in ECD between screening and preoperative images increased with PT using either the EBs- (P < 0.001) or CIARC-determined (P = 0.03) values.

TABLE 2.

Change in ECD From Screening to Preoperative Image

Preservation Time (Days) N Mean (SD) P
Eye-bank- determined
 0–14 1329 34 (219) <0.001*
 0–4 173 6 (192) <0.001†
 5–7 502 14 (212)
 8–11 408 35 (220)
 12–14 246 91 (237)
CIARC- determined
 0–14 965 124 (282) <0.001*
 0–4 131 97 (240) 0.03†
 5–7 376 110 (311)
 8–11 283 137 (267)
 12–14 175 155 (269)
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*

Test whether the change from screening to preoperative ECD is significantly different from zero.

†

Kruskal–Wallis test whether the change from screening to preoperative ECD is significantly different for at least 2 preservation time subgroups.

DISCUSSION

This report compares ECD agreement between a group of EBs and a central image analysis reading center, as previously conducted for the SMAS.22 Although the mean difference between the EBs- and CIARC-determined preoperative ECD was only 15 cells/mm,2 there was notable individual variability to more than 600 cells/mm2 between the EBs and CIARC. The higher mean ECD by the EBs was mainly attributable to the 334 donor corneas in the Before Shipping Group perhaps as a result of decreased image quality because of insufficient warming artifact. Nevertheless, even with preoperative images that may be of lesser image quality after lamellar dissection to analyze in the CPTS, agreement between the EBs and CIARC was comparable to the SMAS with 69% of the CPTS preoperative ECD determinations within 10% of each other compared with 65% in the SMAS from screening images.22 In addition, agreement within 10% on the screening ECD determinations between the EBs and CIARC was comparable in the CPTS (70%) and the SMAS (65%). Applying the stricter <5% difference in ECD between the 2 readers, which governs the CIARC’s standard for adjudication,23 the CIARC’s interobserver agreement for 2 readers was 66% (see Supplemental Figure 1, Supplemental Digital Content 2, http://links.lww.com/ICO/A734) compared with 46% between the EBs and CIARC. Together, these data suggest that the agreement between EBs-determined and CIARC-determined ECD has remained the same over the past 10 years from the SMAS22 to the CPTS.

The CPTS addressed the impact of image quality on accuracy by accounting for the number of cells analyzed, compared with the image quality grading system used in the SMAS.22,23 Similar to the SMAS, in which ECD agreement improved between the EBs and CIARC as image quality improved,22 the CPTS found that agreement in ECD determined between the EBs and CIARC significantly improved when more than an average of 100 cells were analyzed. This is consistent with other investigators’ studies on accuracy based on potential sampling error.11–13

As in the SMAS, when the EBs ECD differed by more than 10% from the CIARC ECD, the difference was more commonly higher (18% of images) than lower (13% of images). In the SMAS, the EBs were more frequently higher than CIARC (28% vs. 7%, respectively).22 This trend toward counting higher or lower ECD has also been noted in a large retrospective study of more than 35,000 donors analyzed by multiple EB technicians.14 The most likely cause of the bias in this retrospective study, in the SMAS22 and now in the CPTS, is cell selection by the technician in an image where the highest number of visible cells can be analyzed, as opposed to analyzing as many of the visible cells in each submitted image and achieving an average of at least 100 cells analyzed.

The questionable value and even risk of specular microscopy after lenticule preparation for DSAEK by the EB has been raised in the past few years. Although the CPTS has reported that EB-prepared DSAEK lenticules did not have a higher chance of positive fungal cultures compared with surgeon prepared tissue,32 before this report there has been increasing interest to diminish the time the donor tissue is at room temperature or warmer including donor evaluation at screening and after lenticule preparation. However, the best endothelial image quality is very much temperature dependent.28,29 With these conflicting priorities, EBs have concentrated on getting their best endothelial images at screening with a warming approach.29 At least for Descemet membrane endothelial keratoplasty, the elimination of specular microscopy has been supported by insignificant change in ECD between screening and after stripping.33 The CPTS interestingly found an increase in the ECD from screening to preoperative evaluation whether determined by the EB or CIARC, and this effect was PT-dependent. This artifactual increase is most likely due to cell selection in areas of highest ECD and compromised image quality after lamellar dissection. Further study is suggested as to the value of determining the ECD after lenticule preparation versus utilizing other methods to evaluate endothelial damage including slit lamp examination after processing and trypan blue staining.34

The strength of this study is that it was a prospective, multi-EB study of current practices by technicians determining ECD from preoperative specular endothelial images that had been certified on image quality. Screening ECDs were also obtained from EB technicians using their usual ECD determination techniques. All of these estimates of ECD were compared with those of a highly experienced image analysis reading center using a dual grading and adjudication process; thus, yielding an excellent opportunity to assess change in accuracy from the SMAS a decade previously.22 The main limitation of the study was that the CIARC did not have the opportunity to study all 1330 screening images, because submission of screening images was not protocol required. Nevertheless, the baseline characteristics of the 25% of the donors that did not have available images did not differ from the 75% of the donors that did, supporting the validity of our comparison of the preoperative ECDs to the screening ECDs, and 97% of the preoperative image sets were available for CIARC analysis. Finally, the ideal comparison of ECD agreement between the EBs and CIARC would be analyzing the same images with the same analysis technique. However, we conducted a real-world comparison that may have been influenced by differing analysis methods and sampling of different areas of cells.

This study has shown that the EBs have maintained or slightly improved in their agreement of ECD determination from screening images with 70% of the ECD determinations within 10% of the CIARC’s and from the larger set of more challenging preoperative images (69%), as compared with the SMAS (65%).22 However, there remains significant variability in determinations between the EBs and a reading center for individual corneas, supporting the importance of analyzing as many visible cells in the field as possible and ideally well over 100 cells.

Supplementary Material

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ACKNOWLEDGMENTS

The authors wish to acknowledge the participating CPTS clinical sites, investigators, and coordinators; eye bank investigators; members of the Operations, Executive, Eye Bank Advisory, Data and Safety Monitoring Committee; Coordinating Center, Cornea Image Analysis Reading Center (CIARC), and Data Management and Analysis Center Staff; and the National Eye Institute staff listed in previous publications (Cornea 2015;34:601–608; JAMA Ophthalmology 2017;135:1401–1409).

Supported by cooperative agreements with the National Eye Institute, National Institutes of Health, Department of Health and Human Services EY20797 and EY20798.

The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Eye Institute or the National Institutes of Health. Additional support provided by: Eye Bank Association of America, The Cornea Society, Vision Share, Inc., Alabama Eye Bank, Cleveland Eye Bank Foundation, Eversight, Eye Bank for Sight Restoration, Iowa Lions Eye Bank, Lions Eye Bank of Albany, San Diego Eye Bank, and SightLife.

Footnotes

The following authors have financial disclosures with companies that manufacture corneal storage solutions (considered relevant to this work): M. Terry (Bausch & Lomb), and W.B. Lee (Bausch & Lomb) (part of CPTS Study Group but not authors on this paper). These authors are employed by eye banks: C. G. Stoeger and J. M. Clover (Lions VisionGift), P. Bedard (Lions Gift of Sight), and K. E. McCoy (Eversight). J. H. Lass is a voluntary board member of Eversight and the Cleveland Eye Bank Foundation. The remaining authors have no conflicts of interest to disclose.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.corneajrnl.com).

REFERENCES

  • 1.Bourne WM, O’Fallon WM. Endothelial cell loss during penetrating keratoplasty. Am J Ophthalmol. 1978;85:760–766. [DOI] [PubMed] [Google Scholar]
  • 2.Lass JH, Gal RL, Dontchev M, et al. Donor age and corneal endothelial cell loss 5 years after successful corneal transplantation. Specular Microscopy Ancillary Study results. Ophthalmology. 2008;115:627–632. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3.Lass JH, Sugar A, Benetz BA, et al. Endothelial cell density to predict endothelial graft failure after penetrating keratoplasty. Arch Ophthalmol. 2010;128:63–69. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4.Lass JH, Benetz BA, Gal RL, et al. Donor age and factors related to endothelial cell loss 10 years after penetrating keratoplasty: specular Microscopy Ancillary Study. Ophthalmology. 2013;120:2428–2435. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 5.Armitage JW, Dick AD, Bourne WM. Predicting endothelial cell loss and long-term corneal graft survival. IOVS. 2003;44:3326–3331. [DOI] [PubMed] [Google Scholar]
  • 6.Ing JJ, Ing HH, Nelson LR, et al. Ten-year postoperative results of penetrating keratoplasty. Ophthalmology. 1998;105:1855–1865. [DOI] [PubMed] [Google Scholar]
  • 7.Patel SV, Diehl NN, Hodge DO, et al. Donor risk factors for graft failure in a 20-year study of penetrating keratoplasty. Arch Ophthalmol. 2010; 128:418–425. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 8.Price MO, Calhoun P, Kollman C, et al. Descemet stripping endothelial keratoplasty: ten-year endothelial cell loss compared with penetrating keratoplasty. Ophthalmology. 2016;123:1421–1427. [DOI] [PubMed] [Google Scholar]
  • 9.Price DA, Kelley M, Price FW Jr, et al. Five-year graft survival of Descemet membrane endothelial keratoplasty (EK) versus Descemet stripping EK and the effect of donor sex matching. Ophthalmology. 2018;125:1508–1514. [DOI] [PubMed] [Google Scholar]
  • 10.Terry MA, Shamie N, Chen ES, et al. Endothelial keratoplasty: the influence of preoperative donor endothelial cell densities on dislocation, primary graft failure, and 1-year cell counts. Cornea. 2008;27:1131–1137. [DOI] [PubMed] [Google Scholar]
  • 11.Hirst LW, Auer C, Abbey H, et al. Quantitative analysis of wide-field endothelial specular photomicrographs. Am J Ophthalmol. 1984;97:488–495. [DOI] [PubMed] [Google Scholar]
  • 12.Hirst LW, Yamauchi K, Enger C, et al. Quantitative analysis of wide-field specular microscopy. II. Precision of sampling from the central corneal endothelium. IOVS. 1989;30:1972–1979. [PubMed] [Google Scholar]
  • 13.Doughty MJ, Muller A, Zaman ML. Assessment of the reliability of human corneal endothelial cell-density estimates using a noncontact specular microscope. Cornea. 2000;19:148–158. [DOI] [PubMed] [Google Scholar]
  • 14.Rand GM, Kwon JW, Gore PK, et al. Technician consistency in specular microscopy measurements: a “Real-World” retrospective analysis of a United States eye bank. Cornea. 2017;36:1172–1177. [DOI] [PubMed] [Google Scholar]
  • 15.Tran KD, Clover J, Odell K, et al. Comparison of endothelial cell measurements by two eye bank specular microscopes. Int J Eye Banking. 2016;4:1–8. [Google Scholar]
  • 16.Doughty MJ. Further analysis of the predictability of corneal endothelial cell density estimates when polymegethism is present. Cornea. 2017;36: 973–979. [DOI] [PubMed] [Google Scholar]
  • 17.Campolmi N, Acquart S, He Z, et al. Inherent errors of the fixed-frame counting method for corneal endothelial cell density in eye banks. Cell Tissue Bank. 2014;15:451–459. [DOI] [PubMed] [Google Scholar]
  • 18.Bohringer D, Hettich L, Maier PC, et al. Data quality of unsupervised endothelial cell counting vs. reading centre analysis in multicentric clinical trials [in German]. Klin Monbl Augenheilkd. 2012;229: 628–631. [DOI] [PubMed] [Google Scholar]
  • 19.Deb-Joardar N, Thuret G, Zhao M, et al. Comparison of two semi-automated methods for evaluating endothelial cells of eye bank corneas. IOVS. 2007;48:3077–3082. [DOI] [PubMed] [Google Scholar]
  • 20.Thuret G, Manissolle C, Acquart S, et al. Is manual counting of corneal endothelial cell density in eye banks still acceptable? The French experience. Br J Ophthalmol. 2003;87:1481–1486. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 21.van Schaick W, van Dooren BT, Mulder PG, et al. Validity of endothelial cell analysis methods and recommendations for calibration in Topcon SP-2000P specular microscopy. Cornea. 2005;24: 538–544. [DOI] [PubMed] [Google Scholar]
  • 22.Lass JH, Gal RL, Ruedy KJ, et al. An evaluation of image quality and accuracy of eye bank measurement of donor cornea endothelial cell density in the Specular Microscopy Ancillary Study. Ophthalmology. 2005;112:431–440. [DOI] [PubMed] [Google Scholar]
  • 23.Benetz BA, Gal RL, Ruedy KJ, et al. Specular Microscopy Ancillary Study methods for donor endothelial cell density determination of Cornea Donor Study images. Curr Eye Res. 2006;31:319–327. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 24.Sayegh RR, Benetz BA, Lass JH. Specular microscopy. In: Mannis MJ, Holland EJ, eds. Cornea: Fundamentals, Diagnosis, Management. Vol 1: Elsevier, London; 2016:160–179. [Google Scholar]
  • 25.Lass JH, Szczotka-Flynn LB, Ayala AR, et al. Cornea Preservation Time Study: methods and potential impact on the cornea donor pool in the United States. Cornea. 2015;34:601–608. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 26.Lass JH, Benetz BA, Verdier DD, et al. Corneal endothelial cell loss 3 years after successful Descemet stripping automated endothelial keratoplasty in the cornea preservation time study: a randomized clinical trial. JAMA Ophthalmol. 2017;135:1394–1400. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 27.Rosenwasser GO, Szczotka-Flynn LB, Ayala AR, et al. Effect of cornea preservation time on success of Descemet stripping automated endothelial keratoplasty: a randomized clinical trial. JAMA Ophthalmol. 2017; 135:1401–1409. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 28.Pham C, Hellier E, Vo M, et al. Donor endothelial image quality in Optisol GS and Life 4°C. Int J Eye Banking. 2013;1:1–8. [Google Scholar]
  • 29.Tran KD, Clover J, Ansin A, et al. Rapid warming of donor corneas is safe and improves specular image quality. Cornea. 2017;36:581–587. [DOI] [PubMed] [Google Scholar]
  • 30.Levene H Robust tests for equality of variances. In: Olkin I, ed. Contributions to Probability and Statistics. Palo Alto, CA: Stanford University Press; 1960:278–292. [Google Scholar]
  • 31.Solomon SR, Sawilowsky SS. Impact of rank-based normalizing transformations on the accuracy of test scores. J Mod Appl Stat Methods. 2009;8:448–462. [Google Scholar]
  • 32.Mian SI, Aldave AJ, Tu EY, et al. Incidence and outcomes of positive donor rim cultures and infections in the Cornea Preservation Time Study. Cornea. 2018;37:1102–1109. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 33.Mayko ZM, Benetz BA, Menegay H, et al. Donor endothelial cell density measurements do not change immediately after DMEK preparation. Cornea. 2016;35:1556–1561. [DOI] [PubMed] [Google Scholar]
  • 34.Eye Bank Association of America. Medical Standards. 2017. Available at: https://restoresight.org/wp-content/uploads/2017/12/Med-Standards-November-9-2017.pdf. Accessed August 26, 2018. [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

E-table 1
NIHMS1834893-supplement-E-table_1.pdf (60.1KB, pdf)
efigure1
NIHMS1834893-supplement-efigure1.pdf (58.6KB, pdf)
efig2A
NIHMS1834893-supplement-efig2A.xcf (110.2KB, xcf)
efig2b
NIHMS1834893-supplement-efig2b.xcf (125.1KB, xcf)
efig2C
NIHMS1834893-supplement-efig2C.xcf (121.5KB, xcf)
efig3A
NIHMS1834893-supplement-efig3A.xcf (128.9KB, xcf)
efig3B
NIHMS1834893-supplement-efig3B.xcf (117.9KB, xcf)

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