Decreased endothelial cell survival after transplantation of corneas preserved by three modifications of corneal organ culture technique

We placed human donor corneas in M-K medium at 4 degrees C for 24 hours, cultured them in minimal essential medium at 34 degrees C for two to five weeks, and then either (1) placed the corneas in M-K medium at 4 degrees C for 48 hours before transplantation (Group 1, 47 eyes); (2) placed the corneas in M-K medium at 4 degrees C for 16 hours before transplantation (Group 2, 17 eyes); or (3) transplanted the corneas without postculture cooling to 4 degrees C (Group 3, 11 eyes). We compared the corneas preserved by organ culture with an equal number of corneas transplanted during the same period, but preserved only in M-K medium at 4 degrees C for one to four days. The central endothelial cell losses noted two months after keratoplasty were significantly greater in the organ-cultured corneas than in the M-K-preserved corneas in each of the three groups. The mean endothelial cell loss in the 11 organ-cultured corneas in Group 3 was significantly less than that in the 64 organ-cultured corneas in Groups 1 and 2. The corneas in Group 1 were also examined one year after keratoplasty, and the cell losses in the organ-cultured grafts remained significantly greater than those in the M-K-preserved grafts.(ABSTRACT TRUNCATED AT 250 WORDS)     

干燥保存角膜在感染性角膜溃疡治疗中的应用

目的:评价应用干燥保存角膜片对554例严重感染性角膜溃疡行治疗性角膜移植手术的效果。方法:选自我院角膜病组1976-08/2000-12期间应用干燥保存角膜片对严重感染性角膜溃疡行治疗性角膜移植手术共计554例,本组病例统计分类为真菌性(238例)、单疱病毒性(170例)、细菌性(70例)及混合感染性(76例角膜溃疡4种,分析临床应用效果。结果:本组手术治疗严重感染性角膜溃疡平均有效率88.8%,其中真菌性角膜溃疡81.5%,单疱病毒性角膜溃疡98.2%,细菌性角膜溃疡97.1%,混合感染性角膜溃疡82.9%。结论:无水氯化钙-硅胶干燥长期保存的角膜片为临床随时提供角膜材料,是一项简单易行、便于推广应用的方法;在临床治疗过程中尽快、尽早查明感染病原体,可避免盲目性;对严重感染性角膜溃疡,治疗性角膜移植可直接清除病灶、较快地控制炎症、缩短治疗过程,达到保存眼球及恢复部分有用视力,为下一步光学性角膜移植创造条件。     

Clinical application of a shape-preserving rapid corneal donor dehydrater

AIM: To describe the design and clinical application of a corneal donor dehydrator which can quickly dehydrate corneas and keep its original shape. METHODS: The corneal donor material is placed on stainless steel beads with different diameters in the dehydrating box to make the cornea the same shape as the steel ball. Then, the cornea is placed inside the dehydrater for rapid dehydrating using the internal cleaning and ventilation system. Totally 83 eyes underwent deep anterior lamellar keratoplasty (DALK) using corneal donor tissue preserved with corneal dehydrater, and 60 patients (60 eyes) received DALK by the same surgeon using corneal donor tissue preserved with glycerol were included in the control group. The best corrected visual acuity (BCVA), the thickness and transparency of the corneal buttons were recorded. RESULTS: After the completion of dehydrating, all the donor corneas maintained a normal shape without any shrinkage or distortion, and the average intraoperative rehydration time was 43.3±12.1s during operation. The mean BCVA of the dehydrater group was 0.30±0.18 at 1wk and 0.32±0.16 at 1mo, which were statistically better than that of the control group (P<0.001). The score of corneal buttons transparency were lower than that of the control group with statistical difference (P<0.001). The thickness of corneal buttons at 1wk and at 1mo in the dehydrater group was significantly better than that of the control group respectively (P<0.001). One week after operation, no corneal button turbidity or edema was observed in both groups. CONCLUSION: The dehydrater can quickly dehydrate the corneal material in a clean and airtight environment and maintain the original shape of the corneal donor during the dehydrating process. This dehydrater is recommended for long-term high-quality preservation in areas where corneal materials cannot be used within a reasonable time period.     

Effect of donor cornea preservation in tissue culture and in McCarey-Kaufmann medium on corneal graft rejection and visual acuity

In a retrospective study the rate of rejection and clouding of the donor cornea for other reasons was investigated in 230 penetrating keratoplasties performed between 1984–1986. Donor corneas were stored in McCarey-Kaufmann Medium (MK) at 4 °C or in a modified Minimal Essential Medium (MEM) at 31 °C. No statistical differences in rejection rate, cloudiness due to other causes or visual acuity was found between MEM- and MK-stored donor corneas.     

Evaluation of various preservation media for storage of donor corneas

Purpose:To compare the physical and microbiological characteristics of McCarey-Kaufman (MK), Cornisol, and Optisol-GS media and evaluate the outcomes of keratoplasty performed using corneas stored in these three media.Methods:The study involved 60 donor corneas which were distributed in 3 groups: MK, Cornisol, and Optisol-GS. Corneas in these groups were further analyzed based on the type of keratoplasty performed (full thickness versus endothelial keratoplasty). At baseline, the endothelial cell density and death to preservation time of donor corneas were recorded. Following keratoplasty, patients were evaluated on day 1, at 1 month, 3 months, and 6 months follow-up. Outcomes were assessed in terms of corrected distance visual acuity (CDVA), endothelial cell density, percentage endothelial cell loss, and corneal thickness. The storage media were also assessed for their physical quality and their microbiological characteristics.Results:Physical characteristics of all three media were found to be within normal limits. Mean CDVA was comparable among the 3 groups at 6-month follow-up. The absolute endothelial cell count values were significantly lower for corneas stored in MK medium (1873.7 ± 261.1 cells/mm²) compared to the Cornisol (2085.0 ± 230.3 cells/mm²) and Optisol-GS media [(2180.3 ± 217.2 cells/mm²) (P = <0.001)]. Corneas stored in Optisol-GS medium were significantly thinner at 1-month follow-up with no significant difference at 6 months (P = 0.66).Conclusion:Optisol-GS and Cornisol media were found to preserve endothelial cell density better and stabilize corneal thickness earlier as compared to the MK medium. However, the functional outcomes were comparable among the three groups.     

Effect of corneal graft diameter on therapeutic penetrating keratoplasty for fungal keratitis

AIM: To evaluate the effect of corneal graft diameter on therapeutic penetrating keratoplasty (PKP) for fungal keratitis. METHODS: A total of 116 patients (116 eyes) suffered from fungal keratitis underwent PKP at the Affiliated Hospital of Medical College Qingdao University from May 2006 to May 2010. They were divided into two groups according to the corneal graft diameter. 64 eyes’ corneal graft diameter was 8.00mm or larger and 52 eyes’ graft diameter was smaller than 8.00mm. The follow-up time was 2 years. The postoperative visual acuity and complications were documented and compared. RESULTS: Sixty-two (96.88%) eyes and fifty (96.15%) eyes preserved eyeballs respectively in two groups. There was no statistical difference in postoperative visual acuity (P=0.961), corneal graft clear rate (P=0.132) or the incidence of recurred fungal infection (P=0.770) between two groups. But there was a higher incidence of graft rejection (P=0.020) and secondary glaucoma (P=0.039) in group with corneal graft diameter 8.00mm or larger. CONCLUSION: PKP is an effective treatment approach for fungal keratitis. There is a higher incidence of complications in large-diameter PKP for fungal keratitis. Effective, preventive and therapeutic measures can improve the prognosis.     

Trends in the distribution of donor corneal tissue and indications for corneal transplantation: the New Zealand National Eye Bank Study 2000-2009

Background: To investigate the indications for corneal transplantation and the distribution of donor corneal tissue in New Zealand. Design: Analysis of the prospective database of the New Zealand National Eye Bank. Participants: A total of 2205 corneal transplants were assessed. Methods: New Zealand National Eye Bank records were analysed for the decade 2000–2009. Main Outcome Measures: Variables analysed included donor corneal tissue distribution (including public and private sectors), indications for transplantation, donor corneal tissue recipient demographics (age and gender) and corneal transplantation type. Results: An average of 220 corneal transplants were performed each year over the 10‐year period (n = 2205). The median recipient age was 45 years (range 3 to 102 years) and 54.0% of recipients were male. In total 71.8% of transplants were performed in the public health sector. Surgeons in the Auckland metropolitan area performed 47.2% of all corneal transplants. The most common indications for corneal transplantation were: keratoconus (41.1%), repeat transplant (17.0%), aphakic/pseudophakic bullous keratopathy (13.9%), corneal dystrophy (10.7%), keratitis (7.9%) and trauma (3.7%). Overall, penetrating keratoplasty accounted for 90.7% of all corneal transplants, however, during the latter half of the study there was a progressive shift in transplantation type, with deep anterior lamellar keratoplasty and Descemet's stripping endothelial keratoplasty combined accounting for 32.3% of all transplants in the final year of the study period. Conclusions: This New Zealand National Eye Bank study provides valuable data regarding the indications for corneal transplantation, transplant recipient demographics and changes in transplantation type in New Zealand over the past decade.     

Standardized ‘no‐touch’ donor tissue preparation for DALK and DMEK: harvesting undamaged anterior and posterior transplants from the same donor cornea

Purpose: To describe a standardized ‘no‐touch’ harvesting technique of anterior and Descemet membrane (DM) grafts for use in deep anterior lamellar keratoplasty (DALK) and Descemet membrane endothelial keratoplasty (DMEK), which provides undamaged anterior and posterior corneal grafts. Methods: A retrospective evaluation was performed of our standard method for harvesting DM grafts and DALK grafts (Technique I; n = 31) versus a newly designed ‘no‐touch’ technique (Technique II; n = 31), in which a peripheral ring of trabecular meshwork tissue is left in‐situ, and the DM graft is trephined on an underlying soft contact lens. Endothelial cell density (ECD) before and immediately after DM stripping was used as the main outcome parameter. Results: Endothelial cell density did not differ within Techniques I and II (before versus after DM stripping) (p = 0.75 and p = 0.54, respectively) or among Techniques I and II (p = 0.61). With the latter technique, anterior corneal grafts and posterior DM grafts could be harvested with negligible damage to the endothelial cell layer or the posterior stromal bed. All 93 grafts (62 DM grafts) were eligible for transplantation, and six months post‐operatively all transplants used were functional. Conclusion: The new technique offers the following advantages: (i) production of ‘undamaged’ grafts for DALK and DMEK, (ii) better controlled tissue handling of the thin DM graft during DM stripping and (iii) an increase in availability of corneal grafts obtained from the same donor tissue pool.     

急诊使用角巩膜缘联合残留物覆盖大型角膜穿孔1例

目的:探讨联合两个经保存的同源角巩膜修补片紧急修复伴有晶状体受挤压和玻璃体暴露的角膜穿孔,在成形性穿透性角膜移植术后的应用。方法:一位49岁的患者患广泛性真菌性角膜溃疡并发后弹力层膨出和微小穿孔。患者在接受了暨成形性穿透性角膜移植术后暴发了自发性大规模角膜穿孔伴晶状体驱逐和玻璃体暴露。鉴于覆盖破损处的迫切需要,供体角膜又无法立即获得,采用联合两个经保存的角巩膜修补片的双移植片。结果:手术成功不仅恢复了眼球的完整性,也免于眼内容物剜除。在接下来的几周内,移植片开始愈合,除了补片的巩膜部分,其它部位有良好的再上皮化,没有感染的迹象,并且能够保持手动视力。鉴于上皮缺损,患者配戴了绷带式角膜接触镜,同时被建议重复穿透性角膜移植术。结论:在缺乏角膜移植片的情况下,可采用一个或多个经保存的同源角巩膜修补片覆盖大范围的角膜缺损。     

Rate of change in central corneal thickness: a viability indicator for conventional drainage tissues in organ culture

Organ culture of human anterior segments is a powerful tool for understanding trabecular meshwork biology. However, data from a significant percentage of cultured anterior segments are unusable because tissues fail to meet quality control requirements, such as having adequate trabecular meshwork histology. The purpose of the present study was to evaluate a novel, real time method for assessing the viability of conventional drainage tissues in the human anterior segment perfusion model. Twenty-two human anterior segments were perfusion cultured using standard techniques for one week while measuring outflow facility and central corneal thickness (CCT). After perfusion-fixation, toludine blue-stained histological sections of drainage tissues from all four quadrants of each anterior segment were graded and endothelial cell nuclei from cornea centers were stained with 4',6-diamidino-2-phenylindole and counted. We found that most anterior segments with a stable outflow facility had a CCT that decreased over time, while anterior segments with an unstable outflow facility had CCT measurements that failed to decrease over time (P<0.01). When comparing CCT measurements to histological appearance of outflow tissues, we found that in 11/11 cases, anterior segments with an acceptable histological score had a negative CCT slope (P<0.01). Conversely in 3/4 instances, anterior segments with an unacceptable histological score had a positive CCT slope. Lastly, we observed a significant relationship between CCT measurements and corneal endothelial density (P<0.01). Thus, the simple procedure of measuring CCT during anterior segment perfusion provides a second useful measure to assess the viability of the anterior segment during the perfusion process.     

Reverse graft suturing to avoid Descemet’s membrane detachment of glycerol-preserved donor cornea used for therapeutic penetrating keratoplasty during COVID-19 to overcome the tissue shortage – A novel surgical technique

To overcome tissue shortage during pandemic, we switched to 100% glycerol preservation of the donor cornea, which is economical and provides longer duration of storage than the short and intermediate storage mediums we normally use like McCAREY Kaufman (MK) or cornisol. During our initial few cases of therapeutic penetrating keratoplasty using glycerol preserved donor cornea, we faced spontaneous Descemet’s detachments resistant to air tamponade. We tried reverse graft suturing and successfully reinforced Descemet’s attachment along with air tamponade, in one of the cases after multiple failed air injections. In the subsequent two cases of infective keratitis needing therapeutic penetrating Keratoplasty, we took eight reverse sutures in between the eight cardinals, to anchor the Descemet’s membrane of the graft. Both the grafts showed attached Descemet’s and maintained good graft clarity. The reverse corneal suturing technique has not been described to the best of our knowledge and hope this helps our corneal fraternity.