Clinical Research On Full Bed Deep Lamellar Keratoplasty And Postoperative Changes Of The Cryopreserved Donor Cornea

Full Bed Deep Lamellar Keratoplasty (FB-DLK) is a new technique of deep lamellar keratoplasty (DLK) reported by us previously. It can expose Desecemet's membrane in the entire bed by the technique of "Stromal hooking", "Pocketing exposure" and "Viscoelastic detaching". Compared to other DLK methods, FBDLK has its advantages over them with less stromal remains and it being smoother between interfaces.The cryopreserved (-20℃) donor corneal button, edematous and acellular, was grafted in FLDLK. The postoperative visual acuity, refractive results and complication rates became the maior concerns of those ophthalmologists. Meanwhile, quite a few questions were waited to be answered. How did the thickness of the donor change after FBDLK? Were recipient's endothelial cells lost in surgical procedure and did they still keep invariable or continue to be lost after FBDLK? How could the epithelium and keratocyte be repopulated from recipient's cornea into donor cornea? It is important to investigate the rules of these changes, however, no relative researches have been reported so far.This study was developed in two aspects: 1. to compare the procedure of operations and the therapeutic outcomes after full bed deep lamellar keratoplasty (FBDLK) and penetrating keratoplasty (PKP). 2. to observe the changes of donor thickness, corneal epithelial basal cells, recipient's endothelial cells, keratocyte and haze in the first postoperative year.Part 1: Comparison of Full Bed Deep lamellar keratoplasty Vs Penetrating keratoplastyObjective: To compare the therapeutic outcomes after full bed deep lamellar keratoplasty (FBDLK) and penetrating keratoplasty (PKP). Methods: Case-control study. We reviewed the clinical notes of 97 eyes of 95 patients who had received FBDLK (48 eyes of 47 patients) or PKP (49 eyes of 48 patients) from Apr. 2002 to Nov. 2004. Full bed deep lamellar keratoplasty was performed with the technique described by Yao. Penetrating keratoplasty was performed with a standard technique using a hand-holding trephine. A single continuous 16-bite 10-0 nylon suture was placed in both groups. The procedure of operations, best corrected visual acuity (BCVA), refractive results and complication were analyzed. Results: The 48 eyes of 47 patients who underwent FBDLK had a mean age of 34.8 years and a median follow-up of 19.7 months. The mean age of the 49 eyes of 48 patients who underwent PKP was 32.8 years and a median follow-up of 25.2 months. The patients in the two groups were matched for preoperaiive visual acuity, gender, age, donor diameter and disease. The average operative time for PKP was 42 minutes, compared with 74 minutes for FBDLK (/= 12.271 p=0.000). Microperforation of Descemet's membrane occurred in 5 eyes (10.4%) of FBDLK series. The median final BCVA of patients was 0.59 in FBDLK and 0.55 in PKP groups (no statistical significance). The mean result for the final spherical equivalent power in both groups was mild myopia (-2.39 + 3.92 DS in PKP group and -1.57 + 3.45 DS in FBDLK group), and the median astigmatism was 4.16 + 2.04 and 3.82+ 1.73 diopters cylinder for PKP and FBDLK group respectively (no statistical significance).The rates of postoperative ocular hypertension, glaucoma, rejection and failure was 51% (25eyes) , 12.2%(6 eyes), 28.6%(14 eyes) and 12.2%( 6 eyes) in PKP group respectively. Postoperative ocular hypertension only occurred in 4.2% (2 eye) of the FBDLK group, and no glaucoma, rejection and donor failure. The difference of the rate of postoperative ocular hypertension, glaucoma, rejection and donor failure between two groups was statistically significant.Conclusions: Best-corrected visual acuity, refractive results are similar after FBDLK and PKP. Less risk for postoperative complications in FBDLK group than in PKP group. However, FBDLK is a more time-consuming and technically difficult procedure than PKP.Part 2: The observation of cornea after Full Bed Deep Lamellar Keratoplasty Objective: to investigate the changes of corneal thickness, epithelium, endothelial cells, keratocyte and haze after FBDLK with — 20°C cryopreserved donor cornea. Methods: the cases were collected after FBDLK with —20°C cryopreserved donor cornea from Apr. 2002 to Nov. 2004, and patients were asked to be examined with ultrasonic pachymetry and corneal confocal microscope at half-month, one month, three months, six months, nine months and twelve months after the surgery. The images of confocal microscope were analyzed by software of NAVIS. The density of corneal epithelial basal cell and recipient endothelial cell was obtained. The cornea! stroma was divided into three sublayers: anterior stroma, mid-stroma and posterior stroma. The density of keratocyte and grade of corneal haze were measured in different sublayers. Results: 33 eyes of 32 patients with regular follow up during the first postoperative year were researched. Corneal thickness averaged about 645±59um at half month, 584±63um at one month, 554±59u.m at three months, 536±51u.m at six months, 524±47um at nine months and 521±49um at twelve months. There was no obvious difference among the thickness at the third postoperative month and that at the sixth, ninth and twelfth month respectively. No exact correlation between the change of thickness and preoperative diseases and time of cryopreservation was found. The re-epithelialization of the donor was almost completed 3-4 days after the FBDLK. The density of the corneal basal cell at the half-month after the operation was 5142 + 688/mm2, quite similar to that of the controlled group and remained stable till 12 months after the operation. Mean endothelial cells were 2003 + 459/mm2 at one month, 1718±400/mm2at six months and 1621 ±364/mm2 at twelve months. There were 14.1% less at the first postoperative month than those at the preoperative time, with asignificant difference (P=0.012 one-way ANOVA). The patients were divided into four groups according to different status in operation. The endothelial cells were 11.4% less in group of no Descemet membrane microperforation without filled air into anterior chamber (11 eyes), 17.9% in group of no Descemet membrane microperforation with filled air into anterior chamber (4 eyes), 13.0% in group of Descemet membrane microperforation without filled air into anterior chamber (3 eyes), 22.7% in group of Descemet membrane microperforation with filled air into anterior chamber (2 eyes). General Factorial showed factor of microperforation had no significant correlation with endothelial cell loss (ir=1.468 ,P=0.243), factor of filled air into anterior chamber had significant correlation with endothelial cell loss (F=9.099 P=0.008) . Mean endothelial cell loss were 5.3% vs 17.9% in FBDLK group vs PKP group during the first postoperative year, that was with statistical significance (f=7.229 P=0.000). The images of corneal stroma showed uniform, gloom and no cellular structure could be seen before the first postoperative month. After that, the keratocyte appeared and increased gradually, especially in mid-stroma. The mean density of keratocyte were 6237 + 3774 cell/mm" in the anterior stroma, 7565 + 4832 cell/mm2 in the mid-stroma and 2149 + 2557 cell/mm2 in the posterior stroma at 12 months after FBDLK, which were approximately 19.2%, 29.8% and 8.7% of substroma of the normal group, respectively. The density of keratocyte of the patients group who less than 35 ages were larger than that of the patients group who more than 35 ages. The difference of the density of keratocyte in anterioe and mid stroma between two groups was statistically significant. The haze of stroma, especially of anterior stroma, changed significant. The grade of haze in the anterior stroma were about 0.1±0.1 at half month, 0.2±0.5 at one month, 1.9±1.6 at three months, 2.3±1.3 at six months, 1.6±1.0 at nine months and l.l±0.9 at twelve months. It was negative correlation between haze grade and keratocyte density from postoperative six months to twelve months. Conclusion: The thickness of -20°C cryopreserved donor cornea decreased gradually and became normally at the third month after FBDLK.Re-epithelialization of the donors was completed rapidly and the densities of the corneal epithelial basal cell were normal at the half-month after the operation and remain stable. The recipient's endothelial cells were lost durng the process of FBDLK but kept invariable during the first postoperative year. Filling air into anterior chamber might mainly lead to the endothelium loss besides manipulation in FBDLK. The keratocyte was repopulated gradually. The density of keratocyte at one year after FBDLK was corrrlate with age. Meanwhile, the haze of cornea changed after FBDLK especially in anterior stroma and reached its peak value at the six postoperative months then decreased gradually. The haze grade and keratocyte density was negative correlation in anterior stroma from postoperative six months to twelve months.