A randomized, prospective, double-masked clinical trial of Optisol vs DexSol corneal storage media

Overview of Short-Term and Intermediate-Term Corneal Storage Solution: Comparison of Clinical Outcomes and Need For Future Research

ABSTRACT

Corneal donor tissue preservation techniques have incrementally improved since the introduction of McCarey-Kaufman storage solution from short-term storage to intermediate duration of storage with the advent of organ culture and Optisol GS storage solutions. Improved understanding of the corneal endothelial cell physiology has helped in designing newer storage solutions, such as the Life 4C and Cornea Cold. The incorporation of antibiotics, ATP precursors, minerals, and vitamins has improved the viability of tissues. In addition, these modifications to the newer storage solutions have increased the endothelial longevity and metabolic activity. Despite these advances, the duration of tissue storage has largely been restricted to 2 weeks in Optisol GS and 4 weeks in organ culture. The role and cost-effectiveness of antifungal supplementation and the need for improved epithelial preservation are additional areas that need to be explored. This review intends to summarize the efficacy and viability of donor corneas in different tissue storage solution and compare clinical outcomes while providing an insight into the challenges in developing newer methods of corneal preservation.

Effect of Cornea Preservation Time on Success of Descemet Stripping Automated Endothelial Keratoplasty: A Randomized Clinical Trial

Importance

Demonstrating that success of Descemet stripping automated endothelial keratoplasty is similar across donor cornea preservation times (PTs) could increase the donor pool.

Objective

To determine whether the 3-year rate of graft success using corneal donor tissue preserved 8 to 14 days is noninferior to that of donor tissue preserved 7 days or less.

Design, Setting, and Participants

A multicenter, double-masked, randomized noninferiority clinical trial was conducted from April 16, 2012, to June 5, 2017, at 40 clinical sites (70 surgeons) in the United States, with donor corneas provided by 23 US eye banks. A total of 1090 individuals (1330 study eyes) underwent Descemet stripping automated endothelial keratoplasty (1255 eyes [94.4%] for Fuchs endothelial corneal dystrophy).

Interventions

Descemet stripping automated endothelial keratoplasty with random assignment of a donor cornea with a PT of 7 days or less (0-7d PT) or 8 to 14 days (8-14d PT).

Main Outcomes and Measures

Graft success at 3 years.

Results

Of the 1090 participants (1330 study eyes; 60.2% women and 39.8% men; median age at enrollment, 70 years [range, 42-90 years]), the 3-year cumulative probability of graft success was 95.3% (95% CI, 93.6%-96.9%) in the 0-7d PT group and 92.1% (95% CI, 89.9%-94.2%) in the 8-14d PT group (difference, 3.2%). The upper limit of the 1-sided 95% CI on the difference was 5.4%, exceeding the prespecified noninferiority limit of 4%. The difference was mostly owing to more primary donor failures in the 8-14d PT group, with the conditional probability of failure after the first month being 2.4% in the 0-7d PT group and 3.1% in the 8-14d PT group. In preplanned secondary analyses, longer PT was associated with a lower rate of graft success (unadjusted hazard ratio for graft failure per additional day of PT, 1.10; 95% CI, 1.03-1.18; P = .008 [PT analyzed as days]), with success rates of 96.5% (95% CI, 92.3%-98.4%) for PT of 4 days or less, 94.9% (95% CI, 92.5%-96.6%) for PT of 5 to 7 days, 93.8% (95% CI, 91.0%-95.8%) for PT of 8 to 11 days, and 89.3% (95% CI, 84.4%-92.7%) for PT of 12 to 14 days (P = .01 [PT analyzed as categorical variable]).

Conclusions and Relevance

The 3-year success rate in eyes undergoing Descemet stripping automated endothelial keratoplasty was high irrespective of PT. However, the study was unable to conclude that the success rate with donor corneas preserved 8 to 14 days was similar to that of corneas preserved 7 days or less with respect to the prespecified noninferiority limit. Although longer PT was associated with a lower success rate, the difference in rates was small when PT was less than 12 days.

Effect of transfer of donor corneal tissue from McCarey-Kaufmann medium to Optisol-GS on corneal endothelium

Purpose:

The purpose of this study is to evaluate the effect of transfer of donor corneal tissue from McCarey–Kaufmann (MK) medium to Optisol-GS on corneal endothelium.

Methods:

This was a prospective, randomized comparative study. Twenty paired human donor corneal tissues of optical quality were retrieved. One tissue of the pair was preserved in Optisol-GS preservative medium (Group A) and other tissue of the pair in MK medium (Group B) at the time of corneoscleral disc excision. Within 12 h of retrieval, each cornea was evaluated using slit-lamp biomicroscopic examination and specular microscopic analysis. Group B corneas were transferred to Optisol-GS medium within 48–53 h of retrieval. Specular analysis of the paired corneas was repeated 3 h after transferring to Optisol-GS. On day 7 of storage, specular analysis of both the tissues was repeated.

Results:

The average age of the donor at the time of death was 29 years (16–68 years). The reduction in endothelial cell count, from baseline, in Groups A and B was 5.5% and 5.8% (P = 0.938) on the 3^rd day and 8.2% and 12.6% (P = 0.025) on the 7^th day, respectively, postretrieval. The coefficient of variation (CV) increased by 36% (P = 0.021) and hexagonality reduced by 19% (P = 0.007) on day 7. All tissues retained an endothelial cell density higher than the accepted critical level for penetrating keratoplasty.

Conclusion:

Significant endothelial cell loss was noted while transferring tissues from one medium to another, necessitating the need for reevaluation of transferred tissues before utilization.

Impact of osmoregulatory agents on the recovery of collagen conformation in decellularized corneas

The process of decellularization of the cornea leads to the removal of cells and antigens. However, during decellularization the ultrastructure of the corneal matrix is usually damaged and a secondary conformation of the collagen fibrils is modulated resulting in altered transparency and physical properties. The strategy for recovering modulation in collagen conformation may help to attain the native physical properties and transparency of the cornea. Decellularized corneas were treated with varied concentrations of glycerol and dextran, and the collagen conformation was monitored by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), x-ray diffraction (XRD) and Raman spectroscopic analysis. The peak at ~4 Å in XRD established the presence of transitional conformations that decreased with the application of osmoregulatory agents, but could not be completely eliminated. This was validated by the results of ATR-FTIR and Raman analysis. Importantly, the mechanism of this loss and the regaining of transparency has been proposed on the basis of the detachment of decorin molecules from the collagen triple helices, due to the change in collagen conformation during decellularization, and the subsequent partial reversal due to the desiccation effect of the osmoregulatory agents on collagen molecules. Taken together, collagen conformational transition can be considered as an indexing tool for the development of improved decellularization techniques.

Randomized, prospective, single-masked clinical trial of endothelial keratoplasty performance with 2 donor cornea 4°C storage solutions and associated chambers

PURPOSE

The aim of this study was to compare endothelial cell loss and graft success 6 months after endothelial keratoplasty (EK) with paired donor corneas stored in Optisol GS and Life4°C solutions and their associated storage chambers.

METHODS

Donor pairs were stored, one in Optisol GS and the other in Life4°C, and prepared for Descemet stripping automated EK or Descemet membrane EK. Matched pairs of recipients with Fuchs dystrophy were randomized to 1 member of each donor pair. Clarity of recipient stroma, intraocular pressure, and complications were followed for 6 months. Central endothelial images of the donor cornea at screening and 3 and 6 months after EK were analyzed by a masked central reading center. Dual grading of endothelial cell density was performed using the center method. Differences in endothelial cell density and cell loss were examined by paired analysis.

RESULTS

Thirty-two pairs were enrolled, and 27 were analyzed (5 had improper matching or loss to follow-up). Donor age was 59 ± 14 years, median death-to-surgery time was 4 days (range, 2-9 days), 6 recipient pairs had Descemet membrane EK, and 21 had Descemet stripping automated EK. Recipient age was comparable in the Optisol GS and Life4°C groups (70 vs. 68 years, respectively, P = 0.46). Six-month central endothelial cell loss did not differ significantly between the Life4°C and Optisol GS groups (18 ± 18% vs. 20 ± 20%, respectively, P = 0.55). All recipient corneas were clear at 6 months in both groups.

CONCLUSIONS

Endothelial cell loss and graft success were comparable at 6 months for paired donor corneas stored in Optisol GS and Life4°C.Clinical Trial Registration-URL: http://www.clinicaltrials.gov. Unique identifier: NCT01657500.

Visual acuity, refractive error, and endothelial cell density 6 and 12 months after deep lamellar endothelial keratoplasty

PURPOSE

To report the visual acuity, refractive outcome, and endothelial cell density (ECD) up to 1 year after deep lamellar endothelial keratoplasty (DLEK) in a large prospective series.

METHODS

Eighty-six DLEK procedures were performed and evaluated in a prospective interventional case series. Subgroup analysis was performed to compare results from large-incision (9 mm) DLEK (n = 7), small-incision (5-8 mm) DLEK (n = 70), and penetrating keratoplasty (PKP) conversion (n = 9). Outcome measures included best-corrected visual acuity (BCVA), manifest refraction, corneal topographic astigmatism, and ECD.

RESULTS

The percentage of eyes that achieved a BCVA of 20/40 or better after DLEK was 55% at 6 months, increasing to 61% at 1 year. Topographic astigmatism and spherical equivalent were not significantly different than preoperative measurements up to 1 year after DLEK (P > 0.05). An endothelial cell loss of 40% at 6 months and 48% by 1 year was observed. The mean ECD after DLEK was 1831 +/- 472 cells per square millimeter at 6 months and 1569 +/- 601 cells per square millimeter at 12 months. When evaluated by incision size, the ECD was better at 2066 +/- 558 cells per square millimeter with a 9-mm incision compared with only 1516 +/- 585 cells per square millimeter with a smaller incision at 1 year, although this did not reach significance (P = 0.075). The endothelial cell loss after penetrating keratoplasty conversion was similar to that in the large-incision group (P > 0.05).

CONCLUSIONS

DLEK provides good visual acuity (> or =20/40) for the majority of patients at 1 year with stable refractive error compared with baseline. Refractive stability was observed with both large- and small-incision DLEKs; however, worrisome endothelial cell loss was observed, especially with a small-incision technique.

Descemet's stripping endothelial keratoplasty: safety and outcomes: a report by the American Academy of Ophthalmology

OBJECTIVE

To review the published literature on safety and outcomes of Descemet's stripping endothelial keratoplasty (DSEK) for the surgical treatment of endothelial diseases of the cornea.

DESIGN

Peer-reviewed literature searches were conducted in PubMed and the Cochrane Library with the most recent search in February 2009. The searches yielded 2118 citations in English-language journals. The abstracts of these articles were reviewed and 131 articles were selected for possible clinical relevance, of which 34 were determined to be relevant to the assessment objectives.

RESULTS

The most common complications from DSEK among reviewed reports included posterior graft dislocations (mean, 14%; range, 0%-82%), followed by endothelial graft rejection (mean, 10%; range, 0%-45%), primary graft failure (mean, 5%; range, 0%-29%), and iatrogenic glaucoma (mean, 3%; range, 0%-15%). Average endothelial cell loss as measured by specular microscopy ranged from 25% to 54%, with an average cell loss of 37% at 6 months, and from 24% to 61%, with an average cell loss of 42% at 12 months. The average best-corrected Snellen visual acuity (mean, 9 months; range, 3-21 months) ranged from 20/34 to 20/66. A review of postoperative refractive results found induced hyperopia ranging from 0.7 to 1.5 diopters (D; mean, 1.1 D), with minimal induced astigmatism ranging from -0.4 to 0.6 D and a mean refractive shift of 0.11 D. A review of graft survival found that clear grafts at 1 year ranged from 55% to 100% (mean, 94%).

CONCLUSIONS

The evidence reviewed is supportive of DSEK being a safe and effective treatment for endothelial diseases of the cornea. In terms of surgical risks, complication rates, graft survival (clarity), visual acuity, and endothelial cell loss, DSEK appears similar to penetrating keratoplasty (PK). It seems to be superior to PK in terms of earlier visual recovery, refractive stability, postoperative refractive outcomes, wound and suture-related complications, and intraoperative and late suprachoroidal hemorrhage risk. The most common complications of DSEK do not appear to be detrimental to the ultimate vision recovery in most cases. Long-term endothelial cell survival and the risk of late endothelial rejection are beyond the scope of this assessment.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Endothelial cell loss after Descemet's stripping endothelial keratoplasty in a large prospective series

PURPOSE

To report the donor endothelial cell loss in the first year after Descemet's stripping endothelial keratoplasty (DSEK) for the treatment of endothelial dysfunction.

DESIGN

Prospective noncomparative interventional case series.

PARTICIPANTS

Eighty eyes of 78 patients with corneal edema.

METHODS

Eighty eyes with endothelial failure were entered into a prospective study of endothelial keratoplasty (EK). The donor central endothelial cell density (ECD) was recorded postoperatively at 6 months (n = 80) and 12 months (n = 80) and then compared with the preoperative eye bank measurements. The subsets of eyes with the donor prepared manually (DSEK; n = 19) and the donor prepared with a microkeratome (Descemet's stripping automated EK [DSAEK]; n = 61) were also evaluated and compared.

MAIN OUTCOME MEASURES

Preoperative and postoperative central ECDs were prospectively evaluated and the cell loss calculated for each postoperative time point.

RESULTS

The average and standard deviation ECD at 6 months was 1908+/-354 cells/mm(2), representing a mean cell loss from preoperative donor cell measurements of 34+/-12%. At 12 months, ECD was 1856+/-371 cells/mm(2) (35+/-13% cell loss). The 1% additional cell loss from 6 to 12 months was not significant (P = 0.233). In the subset of DSEK eyes (n = 19), the cell loss from preoperatively to 6 months was 34%, and at 12 months it was 39%. In the subset of DSAEK eyes (n = 61), the cell loss from preoperatively to 6 months was 34%, and at 12 months it was 34%. There was no statistical difference between the cell loss from DSEK and that from DSAEK at 6 months (P = 0.884) or at 12 months (P = 0.224).

CONCLUSIONS

Descemet's stripping EK using our surgical technique has a mean donor endothelial cell loss of 34% at the 6-month postoperative examination, and this average cell loss remains relatively stable up to at least 1 year. We found no difference in cell loss between the DSEK and DSAEK techniques over this 1-year postoperative period.

Endothelial cell loss after descemet stripping with endothelial keratoplasty influencing factors and 2-year trend

PURPOSE

To identify factors correlated with early endothelial cell loss after Descemet stripping with endothelial keratoplasty (DSEK) and to document cell loss over a 2-year period.

DESIGN

Cross-sectional and longitudinal retrospective analyses.

PARTICIPANTS

A series of 263 eyes in 216 patients who were treated with DSEK and were examined at the same center after surgery.

METHODS

Six-month endothelial cell density (ECD) measurements were analyzed by multivariate analysis of variance to identify preoperative, operative, and postoperative factors that significantly influenced early cell loss. In addition, ECD measurements were compared longitudinally at 6, 12, and 24 months after grafting.

MAIN OUTCOME MEASURES

Central ECD after transplantation.

RESULTS

Mean ECD was 2000+/-550 cells/mm(2) 6 months after DSEK, representing cell loss of 34+/-18%. Factors associated with lower 6-month cell loss were use of single-point fixation forceps that compressed the donor tissue only at the tip during graft insertion (P = 0.025) and absence of any secondary donor reattachment procedure (P = 0.035). Six-month cell loss also was significantly less when DSEK was performed as a combined procedure; in combined cases, the graft was inserted through a clear corneal incision, whereas in standard cases, it was inserted through a scleral tunnel incision, which likely exerted more compression. Cell loss was comparable with manual and microkeratome donor dissection techniques (P = 0.91). Postoperative ECD was correlated positively with donor ECD (P<0.0001) and was correlated inversely with donor age (P<0.0001), although these donor characteristics explained only 10% of the total variance in 6-month ECD. Factors not significantly correlated with 6-month ECD or cell loss included donor death-to-preservation time (range, 1-22 hours; P = 0.45), donor death-to-use time (range, 2-8 days; P = 0.86), and recipient demographics. In 34 DSEK eyes analyzed longitudinally, mean ECD was 3100+/-250 cells/mm(2) before surgery, 2000+/-540 cells/mm(2) at 6 months, 1900+/-480 cells/mm(2) at 1 year, and 1800+/-490 cells/mm(2) at 2 years.

CONCLUSIONS

Cell loss 6 months and 1 year after DSEK was higher than in a recent penetrating keratoplasty series performed at the same center, consistent with more donor tissue manipulation in DSEK. Cell loss was reduced with certain variations in surgical technique.

Five-Millimeter-Incision Deep Lamellar Endothelial Keratoplasty

PURPOSE

To evaluate visual acuity, topography, and endothelial cell density 1 year after deep lamellar endothelial keratoplasty (DLEK) for endothelial dysfunction.

METHODS

This is a prospective, comparative, interventional case series. Thirty-five eyes of 35 patients who had undergone DLEK with a 5-mm incision and had a minimum of 1-year follow-up were included. Main outcome measures were best spectacle-corrected visual acuity (BSCVA), uncorrected visual acuity (UCVA), astigmatism, topographic regularity and symmetry, and endothelial cell density.

RESULTS

: One year postoperatively, BSCVA was 0.33 +/- 0.12 (mean, 20/60; range, 20/40-20/400) compared with 0.15 +/- 0.15 preoperatively (mean, 20/200; range, 20/70-20/800). Six patients did not reach an acceptable visual acuity and were not included in the mean BSCVA, 2 had a primary failure, and the others had preexisting glaucoma or macular disease. Spherical equivalent was -0.04 +/- 1.2 D, refractive astigmatism was 1.76 +/- 1.69 D, surface regularity index was 0.97 +/- 0.54, and surface asymmetry index was 1.25 +/- 0.78 1 year after surgery. Mean endothelial cell count from the donor was 2904 +/- 559 (range, 4694-2111) and 1 year after surgery was 1595 +/- 662 (range, 702-3040), equating to 45% cell loss (range, 15%-77%).

CONCLUSIONS

DLEK is a newer method to replace the endothelium in patients with Fuchs dystrophy. Results showed minimal astigmatism, good topographic parameters, and acceptable visual acuity. Endothelial cell loss at 1 year was significant.

A Prospective Study of Endothelial Cell Loss during the 2 Years after Deep Lamellar Endothelial Keratoplasty

PURPOSE

To report the endothelial survival over a 2-year period after 2 techniques of deep lamellar endothelial keratoplasty (DLEK) in the treatment of endothelial dysfunction.

DESIGN

Prospective, noncomparative, interventional case series.

PARTICIPANTS

One hundred eyes of 88 patients with corneal edema.

METHODS

One hundred consecutive eyes with endothelial failure were entered into a prospective study of endothelial keratoplasty, and the donor central endothelial cell density (ECD) was recorded postoperatively at 6 months (n = 98), 12 months (n = 96), and 24 months (n = 85) and then compared with the preoperative eye bank measurements. The subsets of eyes with large-incision DLEK (n = 36) and small-incision DLEK (n = 62) were also evaluated and compared.

MAIN OUTCOME MEASURES

Preoperative and postoperative central ECDs were prospectively evaluated and the cell loss calculated for each postoperative time point.

RESULTS

The average (and standard deviation) ECD at 6 months was 2140+/-426 cells/mm(2), representing a mean cell loss from preoperative donor cell measurements of 25+/-15%. At 12 months, ECD was 2090+/-448 cells/mm2 (26+/-16% cell loss), and at 24 months, it was 1794+/-588 cells/mm2 (37+/-27% cell loss). The additional cell loss from 1 to 2 years was significant (P<0.001). In the subset of large-incision DLEK eyes (n = 36), the cell loss from preoperatively to 6 months was 23%; 12 months, 22%; and 24 months, 27%. In the subset of small-incision DLEK eyes (n = 62), the cell loss from preoperatively to 6 months was 25%; 12 months, 28%; and 24 months, 43%. The cell loss from small-incision DLEK surgery was significantly greater than that from large-incision DLEK surgery at the 12-month (P = 0.013) and 24-month (P<0.001) postoperative measurements.

CONCLUSIONS

Although the initial cell loss from DLEK surgery is minimally changed from 6 to 12 months postoperatively, there is an acceleration of cell loss from 1 year to 2 years postoperatively. The small-incision DLEK technique, which involves folding of the donor tissue, results in a significantly higher endothelial cell loss at 1 and 2 years than that found after large-incision DLEK surgery, wherein the tissue is not folded.

Specular microscopy ancillary study methods for donor endothelial cell density determination of Cornea Donor Study images

PURPOSE

To describe reliable methods for determining central corneal endothelial cell density (ECD) in a multicenter eye bank study.

METHODS

The Specular Microscopy Reading Center utilized a dual-grading procedure and adjudication process to classify image quality and determine ECD for a subset of donor endothelial images obtained in the Specular Microscopy Ancillary Study, which is part of the Cornea Donor Study. Two certified readers classified images as analyzable (excellent, good, fair) or unanalyzable and determined the ECD using a variable frame technique. An adjudicator also evaluated the images if quality classifications by the two readers differed by one grade, if any reader found the image unanalyzable, and/or if the ECD determination between the two readers was >or= 5%.

RESULTS

Image quality categorization by the two readers was identical for 441 (64%) of 688 donor images. The ECD differed by < 5% for 442 (69%) of the 645 analyzable images. The ECD determined by the adjudicator was < 5% different than the ECD determined by at least one reader for 193 (95%) of the 203 remaining images.

CONCLUSIONS

The dual-grading and adjudication procedures produce reliable, reproducible assessments of image quality and ECD. The importance of two independent readings is evident in that image quality ratings differed between the two readers by one grade in 36% of all images and ECD counts differed by >or=5% for 31% of analyzable images.

Corneal graft survival after prolonged storage in Optisol-GS

PURPOSE

To evaluate the outcome of corneal transplants performed with donor corneas that had been stored for prolonged (>168 hours) periods of time in Optisol-GS storage media.

METHODS

A retrospective review was performed of the medical records of every patient who underwent corneal transplantation between January 1, 1999 and December 31, 1999 utilizing donor tissue that had been in Optisol-GS storage medium for more than 168 hours.

RESULTS

Two hundred thirty-four corneal transplants met the inclusion criteria. The mean duration of follow-up was 33.7 +/- 14.7 months (range 2 to 56 months). The mean Optisol-GS storage time was 237.1 +/- 41.6 hours (range 168 to 348 hours). The overall graft survival rate was 78.6%, ranging from a high of 100% for keratoconus to a low of 42.9% for therapeutic grafts. The likelihood of graft survival, of achieving a visual outcome of 20/40 or better, or of suffering a visual outcome of 20/200 or worse, was not statistically significantly affected by progressively longer periods of donor storage time for the entire study population or for any recipient diagnosis. There were no cases of primary graft failure or early (<3 months) microbial keratitis. An epithelial defect was present on the first postoperative day in every eye. Increased donor storage time was associated with a statistically significant increased risk of persistence of the postoperative epithelial defect for more than 7 days (P = 0.01) as well as for more than 14 days (P = 0.008), although the presence of a postoperative persistent epithelial defect did not have a statistically significant adverse impact on graft survival or visual outcome.

CONCLUSION

Satisfactory surgical outcomes can be achieved utilizing donor corneas that have been stored in Optisol-GS media for more than 7 days. Ophthalmologists utilizing such tissue should be cognizant of the inevitability of postoperative epithelial defects in these cases as well as increased likelihood of development of persistent epithelial defects.

An evaluation of image quality and accuracy of eye bank measurement of donor cornea endothelial cell density in the Specular Microscopy Ancillary Study

PURPOSE

The Specular Microscopy Ancillary Study was designed to examine donor corneal endothelial specular image quality, compare the central endothelial cell density determined by eye banks with the endothelial cell density determined by a central specular microscopy reading center, and evaluate donor factors that may have an impact on specular image quality and endothelial cell density accuracy.

DESIGN

Nonrandomized comparative trial.

PARTICIPANTS

Endothelial specular images of donor corneas assigned in the Cornea Donor Study.

METHODS

Certified readers assessed donor image quality (analyzable from fair to excellent vs. unanalyzable) and determined the central endothelial cell density. Independent adjudication was performed if there was a difference in the quality of grading or if the endothelial cell density varied by > or =5.0% between readers. Average reading center-determined endothelial cell density was compared with the endothelial cell density determined by each eye bank.

MAIN OUTCOME MEASURES

Evaluation of image quality and accuracy of endothelial cell density.

RESULTS

Of 688 donor endothelial images submitted by 23 eye banks, 663 (96%) were analyzable (excellent, 40 [6%]; good, 302 [44%]; fair, 321 [47%]), and 25 (4%) were unanalyzable by reading center standards. In situ retrieval and greater epithelial exposure correlated with a higher image quality grading. The eye bank-determined endothelial cell density of 434 of the 663 (65%) analyzable images were within 10% of the endothelial cell density determined by the reading center, whereas 185 (28%) were more than 10% higher and 44 (7%) were more than 10% lower. Greater variation in endothelial cell density between the eye banks and the reading center was observed with shorter time of death to preservation, presence of an epithelial defect, folds in Descemet's membrane, lower image quality, and the use of fixed-frame or center method endothelial cell density analysis.

CONCLUSIONS

Overall, donor endothelial specular image quality and accuracy of endothelial cell density determination were good. However, the data suggest that factors that may affect image quality and contribute to variation in interpretation of the endothelial cell density should be addressed, because the donor endothelial cell density is an important parameter for assessing long-term corneal graft survival.

Konfokale In-vivo-Hornhautmikroskopie nach Keratoplastik

BACKGROUND

Seven eyes with clear grafts after penetrating keratoplasty were examined with in vivo confocal corneal microscopy in 1999. Our aim was the confocal microscopic investigation of the subclinical changes in clear grafts after long-term follow-up.

METHODS

The preoperative diagnoses were keratoconus (two), granular corneal dystrophy (two), pseudophakic bullous keratopathy due to ACL (two), and corneal ulcer (one). The epithelium, corneal nerves, keratocytes of the anterior and posterior stroma, and endothelium were evaluated with confocal microscopy.

RESULTS

Mean density of basal epithelial cells was 3928+/-378 cells/mm(2) at 15 months and 3284+/-565 cells/mm(2) at 66 months postoperatively. At 15 months the keratocyte density was 750+/-113 cells/mm(2) in the anterior stroma and 601+/-98 cells/mm(2) in the posterior stroma, at 66 months 383+/-53 cells/mm(2) in the anterior stroma and 411+/-98 cells/mm(2) in the posterior stroma. Endothelial cell density decreased from 1719+/-576 cells/mm(2) (15 months) to 965+/-272 cells/mm(2) (66 months).

CONCLUSIONS

In the follow-up period a significant decrease of keratocyte and endothelial cell density was detectable with confocal microscopy. The clinical importance of our findings must be clarified with further examinations on more patients.

Optisol vs Dexsol as storage media for preservation of human corneal epithelium

PURPOSE

To compare the efficacy of two storage media, Optisol GS and Dexsol, in preservation of donor corneal epithelium.

METHODS

A total of 12 pairs of corneas not suitable for transplantation, all with intact epithelium, were used in this study, with one cornea of the pair stored in Optisol GS and its other counterpart in Dexsol. At each of three durations of storage--1, 2, and 4 days--four of these paired corneas were prepared for light microscopy and scanning and transmission electron microscopy. Another four pairs of control cornea were prepared in the same way and placed in universal fixative.

MAIN OUTCOME MEASURES

Evaluation of the corneas was made by two observers masked as to the identity of the storage medium and length of storage. Loss of epithelial cells was evaluated by light microscopy. The attachment of the epithelium to the basement membrane,cellular integrity, intercellular junctions, and intracellular organelles were evaluated and compared by electron microscopy.

RESULTS

The magnitude of epithelial loss correlated with the length of storage time. Control corneas maintained normal epithelium with preservation of all epithelial cell layers. Corneas stored for 1 day had minimal damage of the epithelium. Corneas stored for 2 days had a slight increase in epithelial damage, and corneas stored for up to 4 days showed a marked increase in epithelial damage. There were no significant differences between the two storage media. The basal cell layer was maintained in both the media at all time points, usually in good condition with mild-to-moderate damage in some cases.

CONCLUSIONS

Loss of donor epithelium is related mainly to the length of storage and is similar in both Optisol GS and Dexsol. The storage time should be less than 4 days,especially when performing penetrating keratoplasty on patients with ocular surface disorders.

Fibroblast growth factor-2 protects endothelial cells from damage after corneal storage at 4 degrees C

BACKGROUND

Since the introduction of cold corneoscleral segment storage prior to keratoplasty there have been continuous efforts to ameliorate the preservation media in order to better maintain the quality of the corneal epi- and endothelium. Recent studies have shown that basic fibroblast growth factor (FGF-2) preserves the viability of, for example, retinal ganglion cells and pigment epithelium cells. Therefore, we investigated the effect of different concentrations of FGF-2 added to a modified Optisol storage medium on endothelial damage after corneal storage at 4 degrees C.

METHODS

. Bovine corneas were stored at 4 degrees C for 14 days and for another 24 h at 34 degrees C. Various FGF-2 concentrations (4, 20 and 40 ng/ml) were added to the medium either at day (D) 1, D14, or both D1 and D14. Quantitative evaluation of corneal damage after 14+1 days of storage was conducted by means of the Janus green photometry assay. Histological and ultrastructural investigations of the preserved endothelium were also performed. Bovine cell culture experiments using the TUNEL assay aimed to elucidate the role of FGF-2 on prevention of endothelial apoptosis.

RESULTS

The mean endothelial damage in control corneas increased from 4.9 +/- 1.8% (fresh corneas) to 13.4 +/- 2.4% after 14+1 days of storage. FGF-2 at 20 ng/ml or 40 ng/ml added at any of the indicated time points significantly reduced the overall endothelial damage by 5.1-7.3%, corresponding to 38-54% less endothelial damage than in control corneas (P<0.001). Light- and electron microscopic investigations confirmed this protective effect of FGF-2 on corneal endothelial cells. The TUNEL assay revealed a true anti-apoptotic effect of FGF-2 on endothelial cells in culture.

CONCLUSION

Our study clearly demonstrates the effectiveness of FGF-2 to enhance cell survival of the corneal endothelium after storage at 4 degrees C. A clinical interest could be seen in the potential future application of FGF-2 as an adjuvant to corneal preservation media in order to better maintain endothelial viability during corneal storage.

Nitric oxide generated by corneas in corneal storage media

PURPOSE

The purpose of the study was to quantify nitric oxide release by human corneal buttons in storage media over time.

METHODS

Group 1 consisted of six chambers of Optisol GS corneal storage media, each containing a viable human corneal button with an attached scleral rim (unsuitable for transplantation), sampled at 1-day intervals for at least 17 days (range, 17-28 days). Group 2 consisted of 34 chambers of Optisol GS media, each used to store a corneal button for penetrating keratoplasty, sampled immediately after each surgery. An unused vial of Optisol GS storage medium was sampled daily for 17 days to serve as a background medium control. The total amount of nitrite and nitrate in each sample was determined by a spectrophotometric method based on the Griess reaction.

RESULTS

Data from the daily sampling in group 1 showed that nitrite and nitrate concentrations in storage media containing human corneas increase from a baseline level (beginning at the time the corneas are placed in the media) to an equilibrium concentration of 2.77 microM in a mean time of 6.15 days. Seventy-six percent of the data points from group 2 fell within the 80% predictive interval derived from group 1. No nitrite or nitrate was detected in background medium control samples.

CONCLUSION

The progressive increase in nitrite and nitrate in corneal storage media over time suggests that nitric oxide is continuously released by corneas during storage before transplantation. Given the toxic free radical properties of nitric oxide, corneas in storage media may be subjected to the cumulative toxic effects of nitric oxide.

Transplantation of cryopreserved human corneas in a xenograft model

An ideal model to test methods of corneal storage for transplantation would simulate the environment of the grafted human cornea and predict the success of clinical corneal transplants (human to human). In this study, we tested such a model, the corneal xenograft (human to cat). Nine pairs of human corneas were transplanted into both eyes of nine recipient cats. One cornea of each pair was cryopreserved at -196 degrees C in 2.5 M dimethyl sulfoxide while the other was stored in preservative medium at 4 degrees C (control) for 6 +/- 2 (mean +/- SD) days before transplantation. One week after transplantation, the cats were euthanized and the eyes were examined. Three of the grafts (all cryopreserved) were clinical failures and showed no survival of donor corneal endothelial cells on scanning electron microscopy. The remaining six pairs of grafts were examined with a specular microscope and showed endothelial cell losses of 48 +/- 16% in cryopreserved and 8 +/- 16% in control corneas (p < 0.05). This survival is similar to survival in an earlier corneal perfusion model. The nine cryopreserved grafts were thicker than the control grafts, had fewer surviving keratocytes in the central stroma, and had more apoptotic central keratocytes (TUNEL assay). This failure rate in cryopreserved corneas clearly shows that this technique of cryopreservation was not adequate for clinical use. The corneal xenograft model can be used to study cellular survival and apoptosis in vivo after preservation as well as to test new methods of corneal preservation before initiating clinical trials.

Corneoscleral rim cultures: lack of utility and implications for clinical decision-making and infection prevention in the care of patients undergoing corneal transplantation

PURPOSE

To assess the utility of donor corneoscleral rim cultures.

METHODS

A retrospective review of the culture results of 774 corneoscleral rims that remained after trephination of corneas for transplantation into patients at our academic medical center between January 1992 and November 1997.

RESULTS

Forty-one (5.3%) corneoscleral rim cultures yielded microorganisms, mostly coagulase-negative staphylococci. Two patients developed endophthalmitis (one with Staphylococcus aureus and one with Pseudomonas aeruginosa) within 3 months after transplantation; each had a negative corneoscleral rim culture and neither patient's infection was temporally related to the transplant procedure.

CONCLUSIONS

Preoperative donor corneoscleral rim cultures are unreliable predictors of endophthalmitis complicating corneal transplantation and, therefore, are not useful in the clinical management of patients having corneal transplants. Moreover, the discrepancy between the results of corneoscleral rim cultures and subsequent endophthalmitis renders them invalid as a quality assurance procedure. Instead, for patients with suspected endophthalmitis after corneal transplantation, we recommend that corneal surgeons select antimicrobial therapy based on current guidelines and the results of directed sampling. Furthermore, eye banks should prospectively track recipients who develop clinical endophthalmitis, immediately notify the corneal surgeon who transplanted the matched cornea of that used for the index case, and, in selected situations, attempt to identify a possible source of contamination.

Comparison of Optisol-GS and neomycin-polymyxin B-gramicidin ophthalmic solution for corneal storage in the dog

The objective of the research was to compare the efficacy of Optisol-GS (OGS, Bausch & Lomb Surgical, Irvine, CA, USA) with triple antibiotic ophthalmic solution (neomycin-polymyxin B-gramicidin, NPG; Bausch & Lomb, Tampa, FL, USA) in preserving the viability of corneal endothelial cells. The study subjects were thirty young to middle-aged dogs with no gross corneal pathology that had been euthanized by pentobarbital overdose for reasons unrelated to this project. Corneal tissues were harvested, analyzed, and randomly assigned to treatment groups: one of two media (OGS or NPG), and one of five storage times (1, 7, 14, 21, or 35 days). Six corneas were stored in each medium for each time period. Corneal endothelial cell viability was evaluated pre- and poststorage by vital staining (trypan blue and alizarin red S), and endothelial cell morphology was evaluated with scanning electron microscopy. Storage in NPG caused significant loss (100%) of endothelial cells after all storage times. OGS storage maintained a high level of endothelial cell viability up to 21 days (98.9% +/- 1.3% viability). A significant decrease in percentage viability was also found for OGS-stored corneas between 21 and 35 days, when endothelial cell viability decreased to 61.4% +/- 45.9%. The conclusions are that NPG storage at -20 degrees C is a very poor choice of media for corneal tissue banking if graft clarity is the goal. Storage in Optisol-GS at 4 degrees C for up to 21 days resulted in significantly higher percentages of viable endothelial cells. Optisol-GS storage should facilitate corneal preservation for canine keratoplasty patients.

In vitro comparison of Chen medium and Optisol-GS medium for human corneal storage

PURPOSE

To compare paired human corneas after storage at 4 degrees C in Chen medium (CM) and Optisol-GS medium (OM) for 7, 10, 14, and 21 days.

METHODS

One cornea of each pair from nine human donors was randomly stored in either CM or OM, with its mate cornea stored in the other medium. Three pairs of corneas were stored for 7 days and two pairs each were stored for 10, 14, and 21 days at 4 degrees C. Baseline corneal thickness measurements and endothelial photographs were obtained with a specular microscope. Corneal thickness measurements were also taken on days 7, 10, 14, and 21 of storage. At the end of storage, the corneas were warmed 2 hours before endothelial photographs were taken and were then placed in fixative. A corneal endothelial analysis system was used to compare changes in endothelial size and shape after storage. After fixation, the corneal endothelium was examined by scanning electron microscopy (SEM), and TdT-dUTP terminal nick-end labeling (TUNEL) assays with 4'6-diamidino-2-phenylindole (DAPI) counterstaining were performed on tissue sections of each cornea. A laser scanning confocal microscope and an automated digital analysis system were used to detect the presence of TUNEL-positive apoptotic cells in each cell layer and to determine keratocyte densities.

RESULTS

Mean corneal thickness at 0, 7, 10, 14, 21 days of storage was 0.69 +/- 0.05 mm, 0.69 +/- 0.06 mm, 0.73 +/- 0.08 mm, 0.87 +/- 0.04 mm, and 0.87 +/- 0.03 mm, respectively, for CM and 0.65 +/- 0.06 mm, 0.59 +/- 0.07 mm, 0.63 +/- 0.03 mm, 0.60 +/- 0.03 mm, and 0.69 +/- 0.02 mm, respectively, for OM (p < 0.0001). The mean decrease in endothelial cell density at the end of the 7-, 10-, and 14-day storage periods was 11 +/- 10% for the CM corneas and 5 +/- 5% for the OM corneas (p = 0.18). SEM showed an intact endothelial monolayer in all corneas. The mean percentages of TUNEL-positive cells in epithelium, stroma, and endothelium of CM-stored corneas were 4 +/- 4%, 2 +/- 3%, and 0.1 +/- 0.3%, respectively, and did not differ from the OM-stored corneal values of 4 +/- 3%, 2 +/- 4%, and 0.9 +/- 1.5%. The percentage of TUNEL-positive cells did not increase with storage time. Keratocyte density was 368 +/- 130 cells/mm2 for CM-stored corneas and 447 +/- 96 cells/mm2 for OM-stored corneas (p = 0.13).

CONCLUSIONS

Corneas stored in CM were thicker during storage than those stored in OM. The two storage media did not differ with respect to endothelial cell loss during storage or to the percentage of TUNEL-positive cells or keratocyte density at the end of the storage period.

The past twenty-five years in eye banking

PURPOSE

This review of milestones and challenges in eye banking describes efforts made by dedicated eye bankers to ensure the quality and quantity of corneal tissue for corneal blind patients over the last 25 years.

METHODS

This account is the result of the recollection of the author, discussions with eye bankers, and a review of the literature, public documents, and Eye Bank Association of America (EBAA) records.

RESULTS

A measure of the success of eye banking is the fact that corneal transplant surgery is now scheduled as an elective procedure. Corneal tissue has also enjoyed a stellar safety record. This is due in part to the establishment of comprehensive medical standards by the EBAA, the accreditation of eye banks, and the training and certification of eye bank technicians.

CONCLUSION

Advancements in eye banking over the last 25 years have improved the quality of life of several hundred thousand corneal blind persons in this country. More efforts must be made in the future to eliminate corneal blindness internationally.

Human corneal thickness and its impact on intraocular pressure measures: a review and meta-analysis approach

We determined the "normal" central corneal thickness (CCT) value in human corneas based on reported literature values for within-study average CCT values, and used this as a reference to assess the reported impact of physiological variables (especially age and diurnal effects), contact lens wear, pharmaceuticals, ocular disease, and ophthalmic surgery on CCT. With the expected CCT and its variance defined, it should be possible to determine the potential impact of differences in CCT in intraocular pressure (IOP) assessments, especially by applanation tonometry, using a meta-analysis approach. Some 600 sets of CCT data were identified from the worldwide literature over the period of 1968 through mid-1999, of which 134 included IOP measures as well. The within-study average CCT values and reported variance (SD) was noted along with the number of eyes and any special characteristics, including probable ethnic origin of the study subjects. Various sets of data were subjected to statistical analyses. From 300 data sets from eyes designated as normal, the group-averaged CCT was 0.534 mm. From 230 data sets where interindividual variance was reported, the group-averaged CCT was 0.536 mm (median 0.536 mm; average SD of 0. 031 mm, average coefficient of variation = 5.8%). Overall, studies using slit-lamp-based pachometry have reported marginally lower CCT values (average 0.530 mm, average SD 0.029 mm) compared to ultrasound-based studies (average 0.544, average SD 0.034 mm), which perhaps reflects the type of individual studied (non-surgical vs. pre-surgical patients) rather than the technique itself. A slight chronological increase in reported average CCT values (approximately 0.006 mm/decade) was evident, but a substantial chronological increase was evident for ultrasound pachometry studies (approximately 0.015 mm/decade). Within the meta-analysis-generated average and variance, age had no obvious impact on CCT measures for *whites, although an age-related decline in CCT is evident for non-whites. Any diurnal effects are likely concealed within the expected variance in CCT. Contact lens wear and pharmaceuticals generally produced changes in CCT that were well within the expected variance in CCT. Of the ocular diseases, only those associated with collagen disorders (including keratoconus) or endothelial-based corneal dystrophies (e.g., Fuchs) were likely to result in decreases or increases, respectively, of CCT beyond the normal variance. Routine contact lens wear and diseases such as diabetes seem unlikely to produce changes in CCT of a magnitude that would justify pachometry as a monitoring method beyond routine slit-lamp evaluation. Increases in CCT beyond the expected variance were reported after a range of intraocular surgeries (cataract operations, penetrating keratoplasty), whereas photorefractive surgery produces a measurable decrease in CCT. A meta-analysis of possible association between CCT and IOP measures of 133 data sets, regardless of the type of eyes assessed, revealed a statistically significant correlation; a 10% difference in CCT would result in a 3. 4 +/- 0.9 mm Hg difference in IOP (P </= 0.001, r = 0.419). The observed phenomenon was much smaller for eyes designated as healthy (1.1 +/- 0.6 mm Hg for a 10% difference in CCT, P = 0.023, r = 0. 331). For eyes with chronic diseases, the change was 2.5 +/- 1.1 mm Hg for a 10% difference in CCT (P = 0.005, r = 0.450), whereas a substantial but highly variable association was seen for eyes with acute onset disease (approximately 10.0 +/- 3.1 mm Hg for a 10% difference in CCT, P = 0.004, r = 0.623). Based on the meta-analysis, normal CCT in white adults would be expected to be within +/-11.6% (+/-2 SD) of 0.535 mm, i.e., 0.473-0.597 mm (95% CI, 0.474-0.596). The impact of CCT on applanation tonometry of healthy eyes is unlikely to achieve clinical significance, but for corneas of eyes with chronic disease, pachometry should be performed if the tonometry reveals IOP readi

Efficacy of media enriched with nonlactate-generating substrate for organ preservation: in vitro and clinical studies using the cornea model

BACKGROUND

Using a rabbit cornea model, our recent study demonstrated that Chen Medium (CM), an isotonic media enriched with nonlactate-generating high-energy substrates, is very effective for organ preservation. In the present study, the efficacy of CM is further evaluated with human corneas

METHODS

The effectiveness of CM and Optisol for preserving the endothelial integrity of human corneas in vitro was evaluated by scanning electron microscopy. Clinical efficacy was evaluated in a total of 83 patients: 10 patients with keratoconus grafted randomly with either CM- or Optisol-stored cornea of the same donor, and 73 patients with various conditions grafted with CM-stored corneas. After surgery, visual acuity and quality of the graft were monitored for up to 4.6 years.

RESULTS

The scanning electron microscopic study revealed that after 11-day storage at 4 degrees C, the CM-stored cornea had only marginal disruptive changes, 9.4+/-1.1%, in endothelial cells, as opposed to 42.4+/-4.6% of the Optisol-stored cornea. All 78 CM-stored corneas, including 67 with 12.2- to 17.7-hr death-to-storage time, 3-7.6 days of storage time, and initial marginal quality before storage, were successfully transplanted. These grafts were thin and clear, with an excellent epithelial integrity and without significant changes in endothelial cell density. Five Optisol-stored corneas were also successfully grafted; one of them, however, was edematous for about 4 weeks, and all the grafts were slightly thicker with substantial endothelial cell loss.

CONCLUSION

Using a cornea model, present and recent studies show that CM is very effective for preserving tissue viability and endothelial integrity. Previous study revealed that CM-stored tissues maintained high levels of ATP and metabolic function, with suppression of lactate formation and accumulation. Thus, these findings support the concept that preservation of tissue viability is closely associated with the ability of the tissues to retain metabolic activity, to generate ATP efficiently, and to prevent acidosis effectively during storage.

Epidermal growth factor and insulin use in corneal preservation. Results of a multi-center trial. The Corneal Preservation Study Group

PURPOSE

The ability of DexSol medium, supplemented with two growth factors, human epidermal growth factor (hEGF) and human insulin, to improve long-term endothelial survival after penetrating keratoplasty was evaluated in a multi-center, randomized, prospective, double-masked clinical trial.

METHODS

Donor cornea pairs, one stored in DexSol and the other in DexSol with hEGF (10 ng/ml) and human insulin (10 micrograms/ml) (ProCell), were transplanted into 105 pairs of recipients matched by diagnosis and procedure and followed postoperatively for graft and endothelial survival.

RESULTS

No primary donor failures occurred in either group. Graft clarity did not differ between the ProCell and DexSol groups at all postoperative periods: 3 months (98% versus 99%), 6 months (94% versus 98%), and 1 year (95% versus 97%), respectively. Postoperative complications (e.g., glaucoma, rejection) occurred with comparable frequencies in both groups. Mean endothelial cell loss did not significantly differ between the ProCell and DexSol groups at 3 months (5.7% versus 5.1%), 6 months (8.1% versus 10.1%), and 1 year (12.3% versus 15.6%), respectively. Similarly, there were no clinically and statistically significant differences in other endothelial morphometric parameters.

CONCLUSIONS

The use of corneas stored in DexSol medium with added hEGF and insulin in corneal transplantation resulted in a safety and efficacy profile comparable with that observed in patients receiving DexSol-stored corneas; however, there were no clinically and statistically significant differences in postoperative endothelial morphometric parameters.