Evaluation of corneal graft survival in mice model

AIM:To measure central corneal thickness (CCT) and pre-corneal tear film thickness using the Galilei dual-Scheimpflug analyzer (GSA) in New Zealand white rabbits.METHODS:Ten normal New Zealand white rabbits (20 eyes) were included in this study. With the assistance of 0.1% fluorescein, the pre-corneal tear film can be well visualized. Both eyes of each rabbit were scanned once with the GSA pre- and post-instillation of 1μL 0.1% fluorescein. The difference between the two measurements of CCT (4-mm diameter) was recorded as the pachymetric values of the central tear film.RESULTS:The CCT of pre- and post-instillation was 388.8±9.5μm and 407.0±10.5μm, respectively. After a paired t-test analysis, the central pre-corneal tear film thickness of 4mm diameter was 18.2±5.31μm with a 95% confidence interval of (15.7, 20.6)μm (P<0.001).CONCLUSION:GSA can be used to measure CCT and analyze central tear film thickness of rabbits with the help of fluorescein.     

Long-term Evaluation of Endothelial Cell Changes in Fuchs Corneal Dystrophy: The Influence of Phacoemulsification and Penetrating Keratoplasty

Purpose

To evaluate the natural course of the long-term endothelial cell changes in Fuchs corneal dystrophy (FCD) patients and investigate the effects of phacoemulsification on the annual rate of change in endothelial indices in FCD patients.

Methods

Thirty-four patients diagnosed with FCD at Seoul National University Hospital from 1994 to 2010 were retrospectively reviewed. Sixteen patients who had been followed up for more than 1 year were selected and classified into 3 groups: group A, patients with no ocular surgery; group B, patients who had undergone phacoemulsification only; and group C, patients who had undergone penetrating keratoplasty with cataract surgery. Endothelial cell density, polymegethism, pleomorphism, and pachymetry were measured and the exponential rates of endothelial cell and pachymetry change were analyzed.

Results

A non-linear mixed model of non-operated FCD patients showed that only pachymetric data tended to increase with statistical significance (p = 0.001) with a mean follow-up period of 4.15 years. Using an exponential regression analysis fitting curve, the mean rates of annual endothelial cell loss were 0.82%/yr, 20.39%/yr, and 29.27%/yr in groups A, B, and C respectively, and statistical significance was seen only in group C (p < 0.05).

Conclusions

Retrospective long-term follow-up data showed that changes in endothelial density did not significantly decrease over at least 4 years in middle-aged FCD patients. The changes in pachymetric corneal thickness appeared to increase over the same period. Considering that no exponential changes were aggravated after performing cataract surgery alone, cataract surgery would be a preferable option in FCD patients compared to an approach of "wait-and-do" penetrating keratoplasty combined with cataract surgery.     

A comparison of three methods of decellularization of pig corneas to reduce immunogenicity

AIM:To investigate whether decellularization using different techniques can reduce immunogenicity of the cornea, and to explore the decellularized cornea as a scaffold for cultured corneal endothelial cells (CECs). Transplantation of decellularized porcine corneas increases graft transparency and survival for longer periods compared with fresh grafts.METHODS: Six-month-old wild-type pig corneas were cut into 100-200 μm thickness, and then decellularized by three different methods:1) 0.1% sodium dodecyl sulfate (SDS); 2) hypoxic nitrogen (N2); and 3) hypertonic NaCl. Thickness and transparency were assessed visually. Fresh and decellularized corneas were stained with hematoxylin/eosin (H&E), and for the presence of galactose-α1,3-galactose (Gal) and N-glycolylneuraminic acid (NeuGc, a nonGal antigen). Also, a human IgM/IgG binding assay was performed. Cultured porcine CECs were seeded on the surface of the decellularized cornea and examined after H&E staining.RESULTS:All three methods of decellularization reduced the number of keratocytes in the stromal tissue by >80% while the collagen structure remained preserved. No remaining nuclei stained positive for Gal or NeuGc, and expression of these oligosaccharides on collagen was also greatly decreased compared to expression on fresh corneas. Human IgM/IgG binding to decellularized corneal tissue was considerably reduced compared to fresh corneal tissue. The cultured CECs formed a confluent monolayer on the surface of decellularized tissue.CONCLUSION:Though incomplete, the significant reduction in the cellular component of the decellularized cornea should be associated with a significantly reduced in vivo immune response compared to fresh corneas.     

Macular corneal dystrophy and associated corneal thinning

Purpose

To identify the molecular genetic cause of macular corneal dystrophy (MCD) in four probands, and characterize phenotypic similarities between MCD and keratoconus.

Methods

We performed ophthalmological examination, Scheimpflug imaging (Pentacam, Oculus Inc.), histopathological examination of excised corneal buttons, and direct sequencing of the CHST6 coding region.

Results

Pentacam measurements were taken in six eyes of three probands. All showed diffuse corneal thinning with paracentral steepening of the anterior corneal surface that was graded as keratoconus by the integrated software, but without associated ectasia of the posterior corneal surface or regional thinning. Homozygous or compound heterozygous CHST6 mutations were identified in all cases, including two novel mutations, c.13C>T; p.(Arg5Cys) and c.289C>T; p.(Arg97Cys).

Discussion

Localized elevation of the anterior corneal curvature can occur in MCD in the absence of other features of keratoconus. The identification of a further two Czech probands with the compound allele c.[484C>G; 599T>G] supports the enrichment of this allele in the study population.     

Acellular porcine corneal matrix as a carrier scaffold for cultivating human corneal epithelial cells and fibroblasts in vitro

AIM: To investigate the feasibility of corneal anterior lamellar reconstruction with human corneal epithelial cells and fibroblasts, and an acellular porcine cornea matrix (APCM) in vitro. METHODS: The scaffold was prepared from fresh porcine corneas which were treated with 0.5% sodium dodecyl sulfate (SDS) solution and the complete removal of corneal cells was confirmed by hematoxylin-eosin (HE) staining and 4’, 6-diamidino-2-phenylindole (DAPI) staining. Human corneal fibroblasts and epithelial cells were cultured with leaching liquid extracted from APCM, and then cell proliferative ability was evaluated by MTT assay. To construct a human corneal anterior lamellar replacement, corneal fibroblasts were injected into the APCM and cultured for 3d, followed by culturing corneal epithelial cells on the stroma construction surface for another 10d. The corneal replacement was analyzed by HE staining, and immunofluorescence staining. RESULTS: Histological examination indicated that there were no cells in the APCM by HE staining, and DAPI staining did not detect any residual DNA. The leaching liquid from APCM had little influence on the proliferation ability of human corneal fibroblasts and epithelial cells. At 10d, a continuous 3 to 5 layers of human corneal epithelial cells covering the surface of the APCM was observed, and the injected corneal fibroblasts distributed within the scaffold. The phenotype of the construction was similar to normal human corneas, with high expression of cytokeratin 12 in the epithelial cell layer and high expression of vimentin in the stroma. CONCLUSION: Corneal anterior lamellar replacement can be reconstructed in vitro by cultivating human corneal epithelial cells and fibroblasts with an acellular porcine cornea matrix. This laid the foundation for the further transplantation in vivo.     

Changing trends in corneal graft surgery: a ten-year review

AIM: To review indications and corneal tissue use for penetrating and lamellar surgery between 2002 and 2011. METHODS: The surgical reports of corneal grafts performed during 2002-2011, using tissues supplied by the Eye Bank of Piedmont (Italy), were reviewed retrospectively. Patient demographic data, date of intervention, indication for surgery, and surgical technique used were recorded. Surgical techniques included penetrating keratoplasty (PK), deep anterior lamellar keratoplasty (DALK) and endothelial keratoplasty (EK). The χ2 test was used to compare the distribution of indications and types of surgical technique used, for corneal grafts done during 2002-2006 versus those done during 2007-2011. RESULTS: The number of corneal grafts increased by 30.7% from 2002-2006 to 2007-2011 (from 1567 to 2048). Comparing the two periods, both main indications and surgical techniques changed significantly. In 2007-2011, the proportion of interventions for aphakic/pseudophakic bullous keratopathy (from 16.8% to 21.3%), graft failure (from 16.4% to 19.1%) and Fuchs endothelial dystrophy (from 12.8% to 16.7%) all increased significantly (P<0.05), while those for keratoconus decreased significantly (from 35.6% to 27.3%; P<0.001). In 2007-2011, the proportion of PK decreased significantly (from 92.4% to 57.2%; P<0.001) while that of EK and DALK went from 0.4% to 30.2% (P<0.001) and from 7.2% to 12.6% (P<0.001) respectively. CONCLUSION: During 2002-2011 the number of interventions increased significantly for corneal endothelial diseases and graft failure. The growing demand for interventions for these diseases corresponded to the widespread adoption of EK techniques. The use of DALK also increased, but more moderately than EK procedures.     

Improvement in corneal scarring following bacterial keratitis

Aim

Bacterial keratitis results in corneal scarring and subsequent visual impairment. The long-term evolution of corneal scars has not been well described. In this case series, we identified patients who had improvement in corneal scarring and visual acuity from a clinical trial for bacterial keratitis.

Methods

We searched the records of the Steroids for Corneal Ulcers Trial (SCUT) for patients who had improvement in vision between the 3-month and 12-month visits and reviewed their clinical photographs.

Results

Of the 500 patients enrolled in SCUT, five patients with large central corneal scars due to bacterial keratitis are presented. All experienced improvement in rigid contact lens–corrected visual acuity from months 3 to 12. All patients also had marked improvement in corneal opacity during the same time period. None of the patients opted to have penetrating keratoplasty.

Conclusions

Corneal scars may continue to improve even many months after a bacterial corneal ulcer has healed. The corneal remodeling can be accompanied by considerable improvement in visual acuity, such that corneal transplantation may not be necessary.     

Evaluation of novel decellularizing corneal stroma for cornea tissue engineering applications

AIM: To develop a new decellularization method depended upon the natural corneal structure and to harvest an ideal scaffold with good biocompatibilities for corneal reconstruction. METHODS: The acellular cornea matrix (ACM) were prepared from de-epithelium fresh porcine corneas (DFPCs) by incubation with 100% fresh human sera and additional electrophoresis at 4℃. Human corneal epithelial cells (HCEs) were used for the cytotoxicity tests of ACM. ACM were implanted into the Enhanced Green Fluorecence Protein (eGFP) transgenic mouse anterior chamber for evaluation of histocompatibility. RESULTS: HE and GSIB4 results showed fresh porcine cornea matrix with 100% human sera and electrophoresis could entirely decellularize stromal cell without reducing its transparency. ACM had no cytotoxic effect ex vivo. Animal test showed there was no rejection for one month after surgery. CONCLUSION: These results provide a decellularizing approach for the study of corneal tissue engineering and had the broader implications for the field of biological tissue engineering in other engineered organ or tissue matrix.     

In vivo confocal microscopy of the corneal endothelium: comparison of three morphometry methods after corneal transplantation

Purpose

The purpose of this study was to assess the endothelium of corneal grafts by in vivoconfocal microscopy (IVCM), and to evaluate an automated endothelial software system in comparison with a manual cell count and planimetry.

Patients and methods

Overall, 40 corneal grafts (20 deep anterior lamellar keratoplasties (DALKs) and 20 penetrating keratoplasties (PKs)) were assessed by scanning-slit IVCM. The endothelial cell density (ECD) was estimated with the automated and the manual cell count method of the instrument''s Nidek Advanced Vision Information System (NAVIS) software. The results were compared with planimetry as the reference method, and the agreement was assessed.

Results

The mean (±SD) automated ECD was 2278±524 cells/mm² (range 1167–3192 cells/mm²), whereas the manual cell count method gave significantly lower ECDs with a mean of 1213±677 cells/mm² (range 218–2440 cells/mm²; P<0.001). The manual cell counts were also significantly lower than those by planimetry, with a mean ECD of 1617±813 cells/mm² (range 336–2941, P<0.001). Bland–Altman analyses indicated that the limits of agreement (LoA) between the automated and the planimetry method were −671 and +1992 cells/mm², whereas they were −1000 and +202 cells/mm² when comparing the manual cell counts with planimetry.

Conclusion

Following keratoplasty, the NAVIS automated method is likely to overestimate endothelial cell counts due to oversegmenting of the cell domains. Automated ECDs are substantially higher than those by the manual counting method or planimetry. The differences are considerably larger post-keratoplasty than for normal corneas, and the methods should not be used interchangeably.     

Corneal sensitivity and morphology of the corneal subbasal nerve plexus in primary congenital glaucoma

Background

To quantify the corneal subbasal nerve density and the total number of nerve fibers in primary congenital glaucoma (PCG) and to evaluate their impact on corneal sensitivity.

Methods

Forty eyes of 26 PCG patients were compared with 40 eyes randomly selected from 40 non-glaucoma patients who populated the control group. Central corneal sensitivity (CCS) was assessed by means of Cochet–Bonnet esthesiometry. The mean subbasal nerve density and the total number of nerve fibers were quantified by laser-scanning confocal microscopy. Normality of data was assessed by Kolmogorov–Smirnov testing. Differences in parameters were assessed with Student''s t-test, while correlations with CSS were assessed with Pearson''s correlation.

Results

Significant differences were identified in the mean subbasal nerve density (2108±692 μm in PCG, 2642±484 μm in controls, P=0.003) and in the total number of nerve fibers (12.3±4.2 in PCG, 15.4±3.1 in controls, P=0.02). Both groups presented comparable mean CCS and tortuosity. Both groups presented strong correlations between CCS and mean nerve density (r=0.57 in PCG, r=0.67 in controls, all P<0.05), and between CCS and total number of nerve fibers (r=0.55 in PCG, r=0.56 in controls, all P<0.05).

Conclusion

PCG exerts significant changes in both the mean subbasal nerve density and the total number of nerve fibers. However, these changes do not appear to affect central corneal sensitivity.     

Bilateral crystalline corneal deposits as first clinical manifestation of monoclonal gammopathy: a case report

Aims

To report the clinical and diagnostic findings of a patient with bilateral corneal deposits caused by an underlying monoclonal gammopathy.

Methods

Slit-lamp biomicroscopy, confocal microscopy and additional serological tests were performed on a 35-year-old man presenting with bilateral crystalline corneal deposits.

Results

The patient was diagnosed as having monoclonal gammopathy based on elevated levels of serum immunoglobulin G. Confocal microscopy showed highly reflective (protein) deposits throughout the entire cornea, with the highest density in the epithelium and anterior stromal keratocytes.

Conclusions

Monoclonal gammopathy, a potential sign of a life-threatening disease, can lead to dense, bilateral corneal deposits. As such changes can occur long before ocular or systemic discomforts appear, an early diagnosis is crucial. Ophthalmologists should be aware of corneal deposits as potential warning signs of monoclonal gammopathy.Key words: Bilateral corneal deposits, Monoclonal gammopathy, Diagnosis     

In vitro reconstruction and characterization of tissue-engineered human corneal epithelium with seeder cells from an untransfected human corneal epithelial cell line

AIM: To demonstrate the morphology and structure of in vitro reconstructed tissue-engineered human corneal epithelium (TE-HCEP) with seeder cells from an untransfected HCEP cell line. METHODS: The TE-HCEPs were reconstructed in vitro with seeder cells from an untransfected HCEP cell line, and scaffold carriers of denuded amniotic membrane (dAM) in air-liquid interface culture for 3, 5, 7 and 9 days, respectively. The specimens were examined with hematoxylin-eosin (HE) staining of paraffin-section, immunocytochemical staining, scanning and transmission electron microscopy. RESULTS: During in vitro reconstruction of TE-HCEP, HCEP cells formed a 3-4, 6-7 and 8-10 layers of an HCEP-like structure on dAMs in air-liquid interface culture for 3, 5 and 7 days, respectively. But the cells deceased to 5-6 layers and the structure of straified epithelium became loose at day 9. And the cells maintained positive expression of marker proteins (keratin 3 and keratin 12), cell-junction proteins (zonula occludens-1, E-cadherin, connexin 43 and integrin β1) and membrane transport protein of Na+-K+ ATPase. The HCEP cells in TE-HCEP were rich in microvilli on apical surface and established numerous cell-cell and cell-dAM junctions at day 5. CONCLUSION: The morphology and structure of the reconstructed TE-HCEP were similar to those of HCEP in vivo. The HCEP cells in the reconstructed TE-HCEP maintained the properties of HCEP cells, including abilities of forming intercellular and cell-extracellular matrix junctions and abilities of performing membrane transportation. The untransfected HCEP cells and dAMs could promisingly be used in reconstruction HCEP equivalent for clinical corneal epithelium transplantation.     

Effects of N-acetylcysteine on matrix metalloproteinase-9 secretion and cell migration of human corneal epithelial cells

Background

Matrix metalloproteinase-9 (MMP-9) secreted by corneal epithelial cells has a role in the remodelling of extracellular matrix and migration of epithelial cells. Elevated levels of MMP-9 activity in the ocular surface may be involved in the pathogenesis of corneal diseases. N-acetylcysteine (NAC) has been used to treat corneal diseases, including recurrent epithelial erosions. In this study, its effects on the MMP-9 secretion and human corneal epithelial (HCE) cell migration were evaluated in vitro.

Methods

Confluent HCE cell cultures were treated with 0–20 mM NAC, and tested for MMP-9 secretion and epithelial cell migration by gelatin zymography and scratch wound assay, respectively. Comparisons between different treatment groups were made using analysis of variance, followed by multiple pairwise comparisons.

Results

Twenty mM NAC inhibited the secretion of MMP-9 significantly. Cell migration, assessed after 24 h of wounding, showed a highly significant dose-dependent inhibitory effect.

Conclusions

This study shows that NAC reduces MMP-9 production by HCE cells and inhibits cell migration in vitro. This information helps to elucidate the mechanisms by which NAC may be beneficial therapeutically and suggests that NAC may be useful for managing corneal erosions and related conditions.     

Inhibitory effects of regorafenib, a multiple tyrosine kinase inhibitor, on corneal neovascularization

AIM:To evaluate the inhibitory effects of regorafenib (BAY 73-4506), a multikinase inhibitor, on corneal neovascularization (NV).METHODS:Thirty adult male Sprague-Dawley rats weighing 250-300 g, were used. Corneal NV was induced by NaOH in the left eyes of each rat. Following the establishment of alkali burn, the animals were randomized into five groups according to topical treatment. Group 1 (n = 6) received 0.9% NaCl, Group 2 (n = 6) received dimethyl sulfoxide, Group 3 (n = 6) received regorafenib 1 mg/mL, Group 4 (n =6) received bevacizumab 5 mg/mL and Group 5 (n = 6) received 0.1% dexamethasone phosphate. On the 7d, the corneal surface covered with neovascular vessels was measured on photographs as the percentage of the cornea’s total area using computer-imaging analysis. The corneas obtained from rats were semiquantitatively evaluated for caspase-3 and vascular endothelial growth factor by immunostaining.RESULTS:A statistically significant difference in the percent area of corneal NV was found among the groups (P <0.001). Although the Group 5 had the smallest percent area of corneal NV, there was no difference among Groups 3, 4 and 5 (P >0.005). There was a statistically significant difference among the groups in apoptotic cell density (P = 0.002). The staining intensity of vascular endothelial growth factor in the epithelial and endothelial layers of cornea was significantly different among the groups (P <0.05). The staining intensity of epithelial and endothelial vascular endothelial growth factor was significantly weaker in Groups 3, 4 and 5 than in Groups 1 and 2.CONCLUSION: Topical administration of regorafenib 1 mg/mL is partly effective for preventing alkali-induced corneal NV in rats.     

Association between corneal biomechanical properties and myopia in Chinese subjects

Purpose

To examine the relationship between corneal biomechanical properties and the degree of myopia.

Methods

Chinese subjects (n=172, age: 11−65 years) were divided into diagnostic groups with non-myopia (spherical equivalence (SE)>−0.50 D), low (−3.00≤SE≤−0.50 D), moderate (−6.00≤SE<−3.00 D), and high myopia (SE<−6.00 D). Only the right eye of each subject was analyzed. Central corneal thickness (CCT) was measured by optical coherence tomography. An ocular response analyzer was used to measure corneal hysteresis (CH), corneal resistance factor (CRF), intraocular pressure (IOP), and corneal compensated IOP (IOPcc). Refraction was measured by both automated and subjective refractometry and expressed as SE.

Results

CH was significantly lower in high myopia compared with both low and non-myopia (P≤0.002). CCT was 1.5 times more correlated to CH variation compared with refraction. Similarly, CRF was four times more dependent on CCT than refraction. CH (P<0.001) or CRF (P=0.005) was positively correlated to refraction. Both IOP and IOPcc were negatively correlated to refraction (P<0.001), respectively.

Conclusions

CH decreases only in high myopia. Refraction is positively correlated to both CH and CRF but negatively correlated to both IOP and IOPcc. These results indicate that the mechanical strength in anterior segment of the eye is compromised in high myopia. In addition, high myopia may increase the risk of glaucoma.     

Corneal collagen crosslinking for corneal ectasia of post-LASIK: one-year results

AIM: To evaluate the efficacy and safety of corneal collagen crosslinking (CXL) to prevent the progression of post-laser in situ keratomileusis (LASIK) corneal ectasia. METHODS: In a prospective, nonrandomized, single-centre study, CXL was performed in 20 eyes of 11 patients who had LASIK for myopic astigmatism and subsequently developed keratectasia.The procedure included instillation of 0.1% riboflavin-20% dextrane solution 30 minutes before UVA irradiation and every 5 minutes for an additional 30 minutes during irradiation. The eyes were evaluated preoperatively and at 1-, 3-, 6-, and 12-month intervals. The complete ophthalmologic examination comprised uncorrected visual acuity, best spectacle-corrected visual acuity, endothelial cell count, ultrasound pachymetry, corneal topography, and in vivo confocal microscopy. RESULTS: CXL appeared to stabilise or partially reverse the progression of post-LASIK corneal ectasia without apparent complication in our cohort. UCVA and BCVA improvements were statistically significant(P＜0.05) beyond 12 months after surgery (improvement of 0.07 and 0.13 logMAR at 1 year, respectively). Mean baseline flattest meridian keratometry and mean steepest meridian keratometry reduction (improvement of 2.00 and 1.50 diopters(D), respectively) were statistically significant (P＜0.05) at 12 months postoperatively. At 1 year after CXL, mean endothelial cell count did not deteriorate. Mean thinnest cornea pachymetry increased significantly. CONCLUSION: The results of the study showed a long-term stability of post-LASIK corneal ectasia after crosslinking without relevant side effects. It seems to be a safe and promising procedure to stop the progression of post-LASIK keratectasia, thereby avoiding or delaying keratoplasty.     

TGFBI and CHST6 gene analysis in Chinese stromal corneal dystrophies

AIM: To investigate whether mutations in TGFBI gene or CHST6 gene correlated with stromal corneal dystrophies (CD) in 8 Chinese probands. METHODS: Eight unrelated patients with stromal corneal dystrophies were recruited in this study; all affected members were assessed by completely ophthalmologic examinations. Genomic DNA was extracted from peripheral leukocytes, 17 exons of TGFBI gene and the exon of CHST6 gene were amplified by polymerase chain reaction (PCR), sequenced directly and compared with the reference database. RESULTS: Three heterozygous mutations in TGFBI gene were identified in six patients: c. 370C>T (p.Arg124Cys) was found in exon 4 of TGFBI gene in three members, c. 371G>A (p.Arg124His) was found in one patient; c. 1663C>T (p.Arg555Trp) was found in exon 12 in other two members. In addition,four polymorphisms with the nucleotide changes rs1442, rs1054124, rs4669, and rs35151677 were found in TGFBI gene. Mutations were not identified in the rest of 2 affected individuals in TGFBI gene or CHST6 gene. CONCLUSION: Within these patients, R124C, R124H and R555W mutations were co-segregated with the disease phenotypes and were specific mutations for lattice corneal dystrophy type I (LCD I), Avellino corneal dystrophy (ACD, GCDⅡ), granular corneal dystrophy type I (GCD I), respectively. Our study highlights the prevalence of codon 124 and codon 555 mutations in the TGFBI gene among the Chinese stromal corneal dystrophies patients.     

Posterior corneal curvature assessment after Epi-LASIK for myopia: comparison of Orbscan II and Pentacam imaging

Purpose

To compare the changes in posterior corneal curvature using scanning slit topography (Orbscan II) and Scheimpflug imaging (Pentacam) before and after Epi-laser in situ keratomileusis (LASIK) for myopia.

Methods

In a prospective observational case-series study, 20 myopic patients having undergone Epi-LASIK were examined serially with two different devices, Orbscan II and Pentacam, preoperatively and one month postoperatively. Posterior central elevation (PCE) and posterior maximal elevation (PME) were compared between the two devices, and the changes in parameters after Epi-LASIK were analyzed using a difference map.

Results

All parameters (preoperative and postoperative PCE and preoperative and postoperative PME) that were measured using the Orbscan II were significantly greater compared to those of the Pentacam (for all p < 0.001). PCE and PME were significantly increased one month postoperatively in the Orbscan II measurements (p < 0.05) but were not significantly increased in the Pentacam measurements. Also, ΔPCE and ΔPME, in the difference map obtained by each serial scanning, were significantly greater in the Orbscan II measurements than with the Pentacam (p = 0.012, p = 0.016).

Conclusions

The Pentacam measurements displayed significantly reduced values in all parameters related to posterior corneal elevation compared to those of the Orbscan II. The Pentacam showed no significant change in posterior corneal curvature after Epi-LASIK, based on the difference map.     

Assessment of a variable frame (polygonal) method to estimate corneal endothelial cell counts after corneal transplantation

Purpose

To assess the agreement of the ‘polygonal'' variable frame cell count option on a confocal microscope after keratoplasty, with planimetry as the reference method.

Methods

One hundred clear corneal grafts of 83 patients attending the cornea clinic at Gartnavel General Hospital in Glasgow underwent slit-scanning in vivoconfocal microscopy. Endothelial cell images were assessed with the Nidek Advanced Vision Information System (NAVIS), using the polygonal variable frame and the manual fixed-frame methods. Planimetry was used as the reference. The agreement between methods was assessed by Bland-Altman analysis.

Results

Planimetry provided a mean (±SD) endothelial cell density (ECD) of 1348±726 cells/mm², a value that was very similar to that found by the polygonal method (1404±784 cells/mm²). The fixed-frame method provided lower cell counts with a mean ECD of 1026±610 cells/mm² (P<0.001). When compared with the reference ECD, the polygonal method overestimated the ECD only very slightly with a mean difference of 58 cells/mm² (limits of agreement, LoA, of −222 and 339 cells/mm²). Manual counting underestimated the ECD with a mean difference of −320 cells/mm² (LoA −814 and 173 cell/mm²).

Conclusion

Following keratoplasty, endothelial cell counts with the NAVIS polygonal method are in good agreement with planimetry. The ‘polygonal'' option is proposed as the method of choice for clinical applications with this confocal microscope and a good compromise between reliability and ease of use.