Corneal regrafting after endothelial keratoplasty

Low-Carbon Collaboration in the Supply Chain under Digital Transformation: An Evolutionary Game-Theoretic Analysis

In the face of the challenges posed by the need to drastically decrease carbon emissions, all agents in the supply chain need to strengthen low-carbon collaboration with the support of digital transformation. This study sets up a low-carbon collaboration evolutionary game model of the supply chain based on benefit sharing by introducing digital transformation. The equilibrium-point stability of the supply chain is then analyzed under two separate conditions—i.e., less and more government rewards and punishments compared to supply-chain agents’ strategic risk cost. Furthermore, based on the evolutionary game model, this study draws the system dynamics (SD) flow diagram to analyze the research problem quantitatively. The main results show that: (1) low-carbon benefit-driven effects promotes collaboration benefit sharing, thereby increasing the probability of low-carbon collaboration; (2) digital transformation is an essential regulator of low-carbon collaboration in the supply chain and can amplify the low-carbon benefit-driven effect; (3) collaboration benefit sharing can perfectly coordinate the vertical supply chain under low-carbon collaboration; and (4) government support and management are critical links in the low-carbon collaboration formation path of the supply chain. This research provides theoretical support for low-carbon collaboration in the supply chain under digital transformation.

Repeat corneal transplantation: indication, surgical technique, and early graft failures trends in France from 2004 to 2019

PURPOSE

To investigate the repeat corneal transplantation trend in France from 2004 to 2019.

METHODS

Review of the prospectively compiled French Biomedicine Agency electronic database containing all corneal transplantation records from 2004 to 2019. The surgical technique, demographic characteristics, diagnosis, and previous graft data were retrieved and analyzed using the Cochran-Armitage trend test.

RESULTS

A total of 66,584 corneal transplantations were performed, 51,260 of which were first grafts and 15,324 (23%) were regrafts. For regrafts, 77% were penetrating keratoplasties (PK) and 19.6% were lamellar keratoplasties (LK). Age, hypertonia, glaucoma, trauma, lens surgery, immune disorders, diameter > 8.5 mm, and neovessels in > 2 quadrants were associated with a higher rate of repeat keratoplasty. Keratoconus, secondary endothelial dystrophy, and Fuchs' dystrophy were the principal indications for regrafting. When a previous graft failed, it occurred earlier for patients with LK (4.6 years, median = 2, SD = 7.54) than PK (8.48 years, median = 5, SD = 9.51). Failure within a year was the reason why 28.3% of the LK regrafts and 12.5% of PK regrafts were performed, while for failure within two years these values were 49.9% and 27.8%, respectively. Graft survival decreased with the number of repeat keratoplasty, being more pronounced after a second LK regraft and after a first PK regraft.

CONCLUSION

The number of LK regrafts increased continuously, and 1/3 were performed for failure within the year. This rate increased until 2015, after which it stabilized until 2019, probably due to the better mastery of the technique.

Effect of Body Refrigeration Time on Cornea Donor Tissue

PURPOSE

To determine how early body refrigeration affects corneal donor transplant suitability and endothelial cell density.

METHODS

Donor information was obtained from the CorneaGen Eye Bank including demographics, time of death to preservation, and body refrigeration status, for donors between 2012 and 2016. The death to preservation interval was classified into 3 categories: 0 to 10, 10 to 20, and 20+ hours. Two primary logistic method models were fit using a main effects model and an interaction model to determine the association of body refrigeration on unsuitability of transplantation and endothelial cell density.

RESULTS

Analysis was from 42,929 donor eyes, with a mean (standard deviation) endothelial cell count of 2743 (415) cells/mm2. Fifty-nine percent of donor eyes were from male donors in the eye bank data set, and the mean death to preservation interval was 11.0 (5.6) hours for all eyes. Unsuitability for transplantation demonstrated a reduced adjusted odds ratio by 22% (OR = 0.78, P = 0.009) when the body was refrigerated during the death to preservation interval versus when the body was not refrigerated. Eyes that were refrigerated, however, exhibited no statistically significant difference in endothelial cell count from eyes that were not refrigerated (P = 0.12).

CONCLUSIONS

We demonstrate an appreciable effect of early body refrigeration on transplant suitability in this large cohort of eye bank eyes. There was no beneficial effect of body refrigeration on endothelial cell count.

Five Years Pathological Evaluation of Corneal Regrafts: A Study from Southern Iran

Purpose

Corneal regrafts sometimes needed to restore the transparency after graft failure. The aim of the study is five years epidemiologic and histopathological evaluation of corneal regrafts.

Methods

In this cross-sectional study, all corneal regrafts during 5 years (2012–2016) were assessed in the Khalili Ophthalmology Center at Shiraz city. Demographic data including age, area of residence, primary disease, type of graft, cause of regraft, interval between primary and subsequent grafts (IPSG), associated eye diseases or surgeries, and systemic diseases were recorded. Also, microscopic findings of corneas were reviewed.

Results

Among a total of 1190 corneal grafts, 76 of them (6.38%) were regrafts. The most common type of grafting was penetrating keratoplasty (PK). The shortest IPSG was observed in fungal keratitis. Main causes of graft failure were endothelial dysfunction, infection, immunologic rejection, technical problems, and recurrence of primary disease, respectively. The most common histopathological finding in failed grafts was severe endothelial cell loss (89.8%). Also, more than half and one-third of cases had Descemet membrane changes and stromal ingrowth, respectively.

Conclusion

Endothelial cell loss was the major cause of failure in our study. Also, recurrence rate in infective cases, especially fungal keratitis, was very high. Considerable presence of histopathological changes such as doubling of Descemet membrane and retrocorneal fibrous ingrowth need further investigations. Perhaps, modification in techniques of corneal grafting and assessment of donor tissue and recipient bed along with any need for longer medical treatment are the basis for future studies in order to increase graft survival.

Evolution and Optimization of Urban Network Spatial Structure: A Case Study of Financial Enterprise Network in Yangtze River Delta, China

The urban network is an important method of spatial optimization, and measuring the development level of the urban network is a prerequisite for spatial optimization. Combining geographic information system (GIS) spatial analysis, social network analysis, and multidimensional scaling models, we explored the evolution of the urban network spatial structure in the Yangtze River Delta from 1990 to 2017 and proposed corresponding optimization measures. The results showed that the urban network spatial structure of the Yangtze River Delta has evolved from a single-center cluster with Shanghai as its core to a multi-center network with Shanghai as its core and Nanjing, Hangzhou, and Hefei as secondary cores. The density of the urban network has gradually expanded, but the strength of the connection between edge cities such as Chizhou, Suqian, and Quzhou and the core cities needs to be further improved. We found that the evolution of the urban network spatial structure has been driven by preferential attachment, path dependence, and differences in economic and industrial development. Finally, we propose optimizing the urban network spatial structure by strengthening the driving ability of the core cities, clarifying urban functions and development directions, and establishing a unified coordination mechanism. This paper enriches and deepens our understanding of the characteristics of the city network in the Yangtze River Delta, and provides a reference for the optimization of the urban network spatial structure.

Factors Influencing Graft Endothelial Cell Density after Descemet Stripping Automated Endothelial Keratoplasty

Purpose:

To determine the factors that influence the endothelial cell density (ECD) of donor grafts after Descemet stripping automated endothelial keratoplasty (DSAEK).

Methods:

This retrospective, interventional case series comprised 77 eyes of 64 patients who underwent DSAEK. Confocal microscopy was performed at the final follow-up examination to evaluate the endothelial cell count, cell morphology, and graft thickness. Univariate and multiple linear regression analyses were used to investigate recipient-, donor-, surgical-, and postoperative related variables capable of influencing graft endothelial cell counts after DSAEK.

Results:

The mean patient age was 62.3 ± 15.6 years; patients were followed-up for 26.2 ± 20.9 months postoperatively. Forty-six eyes (59.7%) underwent stand-alone DSAEK; 31 eyes (40.3%) underwent DSAEK combined with cataract surgery. The donor trephination size was 8.0 ± 0.21 mm. The mean donor age was 30.4 ± 11.2 years, and the mean preoperative endothelial cell density was 3127.4 ± 315.1 cells/mm², which decreased to 1788.6 ± 716.5 cells/mm² postoperatively (P < 0.001). The mean postoperative central graft thickness was 102.4 ± 31.6 μm. Univariate analysis revealed that postoperative ECD was significantly associated with death to preservation time (P = 0.046), graft thickness (P = 0.016), follow-up duration (P = 0.005), and graft non-attachment (P = 0.049). Multiple regression analyses identified graft thickness (β = 10.62, P = 0.003) and follow-up duration (β = -22.09, P = 0.001) as the significant characteristics influencing postoperative ECD.

Conclusion:

The primary predictors of ECD after DSAEK were graft thickness and duration of follow-up. Surgeons’ requests for ultrathin DSAEK donor grafts to improve visual outcomes might not have the desired postoperative outcome with respect to ECD.

Descemet membrane endothelial keratoplasty and refractive surgery

PURPOSE OF REVIEW

Descemet membrane endothelial keratoplasty (DMEK) has become a first-line treatment in corneal endothelial diseases because of its exceptional clinical outcomes and low complication rates. Because of its improved refractive predictability, DMEK is now also considered for managing cases with endothelial decompensation following previous refractive procedures, or in combination with those. This article reviews the clinical outcomes in these cases and discusses the possibility of refractive interventions following DMEK.

RECENT FINDINGS

DMEK has been successfully performed in eyes after laser in-situ keratomileusis, eyes after anterior chamber intraocular lens (IOL) implantation and aphakic eyes. Often, DMEK is combined with cataract surgery (triple-DMEK). Initial reports on reducing the refractive cylinder by toric IOL implantation are available. Although there are some reports on phacoemulsification and IOL implantation after phakic DMEK, reports on laser refractive procedures following DMEK are lacking.

SUMMARY

In contrast to earlier keratoplasty techniques, DMEK induces on average only mild refractive shifts owing to the 'natural' restoration of the cornea. As such, DMEK may be ideal in managing corneal decompensation in refractive patients. However, further studies are required to assess the safety and efficacy of DMEK after refractive treatment and of refractive procedures following DMEK.

Risk Factors Predicting the Need for Graft Exchange After Descemet Stripping Automated Endothelial Keratoplasty

PURPOSE

To identify the risk factors predicting the need for graft exchange after Descemet stripping automated endothelial keratoplasty (DSAEK).

METHODS

This is a retrospective cohort study. The study group included all 117 eyes that underwent or necessitated repeat DSAEK performed between January 2005 and June 2014 at Villa Serena-Villa Igea private hospitals (Forlì, Italy). The control group consisted of 1033 eyes that underwent only primary DSAEK during the same period. Demographic details, indications for primary surgery, ocular preoperative status and comorbidities, donor endothelial cell density (ECD), and postoperative complications were compared between the groups using univariate and multivariate analyses.

RESULTS

The prevalence of graft failure necessitating graft exchange was 10.2% (117 of 1150 eyes). In univariate analysis, a diagnosis of Fuchs endothelial dystrophy was a protective factor against the risk of repeat DSAEK. Prior trabeculectomy or aqueous shunt implantation, postoperative graft detachment, lower donor ECD, and a rejection episode were all associated with a significantly higher risk of requiring repeat DSAEK. The presence of buphthalmos, anterior chamber intraocular lens, aphakia, or prior penetrating keratoplasty were not risk factors for the failure of DSAEK. Of these variables, multivariate analysis showed that only prior aqueous shunt implantation [odds ratio (OR) = 5.5, 95% confidence interval (CI), 1.4-22.2], lower donor ECD (OR = 0.99, 95% CI, 0.997-0.999), and a documented postoperative rejection episode (OR = 18.2, 95% CI, 7.9-45.0) predicted the need for repeat DSAEK.

CONCLUSIONS

DSAEK grafts have similarly good long-term survival regardless of the indication for surgery, lens status, or ocular comorbidities, with the only exception being the presence of an aqueous shunt.

Application of the femtosecond laser LASIK microkeratome in eye banking

PURPOSE OF REVIEW

To review the literature for recent advancements in the femtosecond laser technology with regard to its applications in corneal transplantation and eye banking.

RECENT FINDINGS

Advancements in corneal surgery have encouraged the use of disease-specific corneal subcomponents, utilized in procedures such as anterior-lamellar keratoplasty and endothelial keratoplasty, instead of traditional transplant procedures to minimize adverse effects of penetrating keratoplasty. Femtosecond laser microkeratomes can precisely create flaps for such transplant procedures, achieve better wound stability, and promote healing by shaped wound configurations. Laser microkeratomes have been compared to traditional mechanical microkeratomes for keratoplasty procedures from various aspects and are superior in some aspects and offer unique capabilities.

SUMMARY

Femtosecond laser applications in eye banking include preparation of donor and recipient corneas for use in penetrating keratoplasty, anterior-lamellar keratoplasty, and endothelial keratoplasty. Advantages of femtosecond laser microkeratomes include higher precision of the cut, ability to achieve thinner flaps, and wound configurations that allow greater wound stability, shorter recovery time, and less postoperative pain. However, cost and availability at the eye-bank level may hinder widespread and immediate application.

Outcomes of repeat endothelial keratoplasty in patients with failed Descemet stripping endothelial keratoplasty

PURPOSE

To report the outcomes of repeat endothelial keratoplasty (EK) in patients with failed Descemet stripping endothelial keratoplasty (DSEK).

METHODS

The clinical records of patients with failed DSEK who underwent repeat EK surgery at a single institution were reviewed.

RESULTS

A total of 20 eyes of 20 patients (8 men and 12 women) were included. The mean age at initial DSEK surgery was 69.9 ± 11.9 years (range, 41-83 years). The causes of DSEK failure included progressive endothelial failure (8 eyes; 40%), primary graft failure (8 eyes; 40%), and endothelial rejection (4 eyes; 20%). The mean duration from primary DSEK to repeat EK was 13.1 ± 10.3 months (range, 2-33 months). Removal of the failed DSEK donor disc was performed in all eyes. Mean preoperative corrected distance visual acuity (logMAR) before repeat EK surgery was 1.76, and this improved to 0.5 (P < 0.001) at the final follow-up at 27 months. Three eyes had limited corrected distance visual acuity secondary to ocular comorbidities (age-related macular degeneration and advanced glaucomatous optic neuropathy).

CONCLUSIONS

Repeat EK in patients with DSEK failure is an effective treatment modality. This is the preferred management option compared with penetrating keratoplasty because the advantages of EK surgery are maintained with repeat EK surgery.

Eye bank tissue utilization between endothelial keratoplasty and penetrating keratoplasty

PURPOSE

To determine rates of tissue use for corneal transplants via endothelial keratoplasty (EK) relative to penetrating keratoplasty (PK).

METHODS

Retrospective chart review of all cornea tissues (n = 3669) distributed from the Lions Eye Bank of Wisconsin for EK or PK from August 1, 2004 through July 31, 2009 (60 months). Rates of tissue use for EK relative to PK were determined both on a yearly basis and for the overall study period. Replacement frequency and time to subsequent surgery were established for each group. Donor tissue and recipient characteristics were compared between groups.

RESULTS

Donor characteristics did not differ between the 2 groups; 11.9% of EK tissues failed and were replaced during the study period compared with 5.1% of PK tissues (P < 0.0001). Additional tissue for the same eye came at a mean of 174 days after an EK surgery compared with 558 days after a PK (P < 0.0001). Surgeons requesting tissue for EK increased each year, whereas the number of repeat tissue requests decreased over time.

CONCLUSIONS

Additional tissues were required for recipients of EK more than twice as often as for recipients of PK, and replacement of EK grafts occurred at a mean of more than 1 year before replacement of PK grafts. This pattern of tissue utilization during the first 5 years of distribution for EK did not negatively affect the Lions Eye Bank of Wisconsin from meeting the surgeon demand for tissue in its service area. Eye banks may wish to monitor tissue utilization as part of their quality assurance program.