Yifei Huang

Corneal Biomechanical Assessment Using Corneal Visualization Scheimpflug Technology in Keratoconic and Normal Eyes

Purpose. To compare the corneal biomechanical properties of keratoconic patients and age-matched controls using corneal visualization Scheimpflug technology (Corvis ST). Methods. Sixty keratoconic eyes from 47 keratoconus patients and 60 normal eyes from 60 controls were enrolled in this prospective study. Tomography and biomechanical parameters of all eyes were obtained with the Pentacam and Corvis ST, respectively. Intraocular pressure was measured using a Goldmann applanation tonometer. Results. The tomography and biomechanical parameters of the keratoconic corneas were significantly different from those of the normal corneas except for the anterior chamber angle, first applanation length, the highest concavity time, and peak distance. The deformation amplitude was the best predictive parameter (area under the curve: 0.882), with a sensitivity of 81.7%, although there was a significant overlap between keratoconic and normal corneas that ranged from 1.0 to 1.4 mm. In both the keratoconus and control groups, the deformation amplitude was negatively correlated with intraocular pressure, central corneal thickness, and corneal volume at 3 and 5 mm. Conclusions. Corvis ST offers an alternative method for measuring corneal biomechanical properties. The possibility of classifying keratoconus based on deformation amplitude deserves clinical attention.

Corneal biomechanical characteristics measured by the CorVis Scheimpflug technology in eyes with primary open‐angle glaucoma and normal eyes

To evaluate the biomechanical properties of the cornea using Corneal Visualization Scheimpflug Technology (CorVis ST, Oculus) in eyes with primary open‐angle glaucoma (POAG) and normal control eyes.

Moscow Eye Microsurgery Complex in Russia Keratoprosthesis in Beijing

PURPOSE To evaluate the efficacy and preliminary safety of the Moscow Eye Microsurgery Complex in Russia (MICOF) keratoprosthesis in eyes with complicated corneal opacities unsuitable for keratoplasty. DESIGN Retrospective review of consecutive clinical case series. PARTICIPANTS We analyzed 85 eyes of 85 patients who previously underwent MICOF keratoprosthesis implantation at the Chinese PLA General Hospital between April 1, 2000, and August 31, 2009. The mean follow-up after MICOF keratoprosthesis implantation (measured after the second stage of the implantation) was 34.7 months (range, 3-107 months). METHODS The MICOF keratoprosthesis surgery involves 2 procedures. In stage 1, a supporting titanium frame is inserted into the lamellar pocket; a polymethyl methacrylate (PMMA) optical cylinder is implanted 3 months later (stage 2). Data were collected from the preoperative, intraoperative, and postoperative courses. Statistical analysis was performed to identify factors influencing postoperative complications. MAIN OUTCOME MEASURES Visual acuity (VA), keratoprosthesis retention, and significant postoperative complications. RESULTS The MICOF keratoprosthesis dramatically improved vision in most patients. The percentage of eyes with postoperative VA of 20/100 or better was 80.7% (67/83) at 6 months after stage 2, 82.4% (61/74) at 1 year, 72.7% (40/55) at 2 years, 78.8% (26/33) at 3 years, 78.9% (15/19) at 4 years, 100% (8/8) at 5 years, 80% (4/5) at 6 years, 100% (2/2) at 7 and 8 years, and 100% (1/1) at 9 years. The most common complication, retroprosthetic membrane formation, occurred in 39 of 85 eyes. The overall keratoprosthesis retention rate was 81.2% at an average follow-up of 34.7 months (range, 3-107 months). Ten eyes presented with elevated intraocular pressure after implantation; 3 of these had underlying glaucoma. All 3 eyes received cyclocryotherapy to control intraocular pressure. Sterile vitreitis occurred in 2 eyes, and retinal detachment occurred in 1 eye. CONCLUSIONS The MICOF keratoprosthesis is an effective alternative for patients with corneal blindness and a poor prognosis for penetrating keratoplasty.

Long-term outcomes of MICOF keratoprosthesis in the end stage of autoimmune dry eyes: an experience in China

Aims To evaluate the clinical outcomes following Moscow Eye Microsurgery Complex in Russia keratoprosthesis (MICOF KPro) implantation in end-stage autoimmune dry eyes. Methods A retrospective observational case series. Fourteen patients with end-stage autoimmune dry eyes underwent MICOF KPro surgery by one surgeon (YH) in the Chinese PLA General Hospital between 2000 and 2009. Retention of the prosthesis and vision were recorded and postoperative complications were analysed. Results Preoperative diagnosis included Stevens–Johnson syndrome (n=7), ocular cicatricial pemphigoid (n=4) and Sjogrens syndrome (n=3). The mean follow-up period was 3.9 years (range 10 months–7.8 years). After surgery, 13 eyes (93%) showed a visual acuity of 20/200 or better and 6 eyes (43%) achieved excellent vision of 20/40 or better. At last visit, 69% of the eyes (9/13) maintained a visual acuity of at least 20/200. The first case retained a visual acuity of 20/80 7.8 years after the operation. The most common complication was stromal melting that threatened anatomical success. Seven of the first eight patients showed tissue melting, and four of them had leakage. All of these were repaired successfully. The latter six cases received prophylactic autologous auricular cartilage implantation to reinforce the anterior surface of recipients cornea at either stage 1 or 2. Other causes of vision loss included pre-existing glaucoma (n=6), sterile vitritis (n=5), cylinder loosening (n=1) and retroprosthetic membrane (n=4). Conclusion MICOF KPro provided useful vision for the end stage of autoimmune dry eyes in our study. Anatomical stability of KPro was achieved in all cases using repair and reinforcing surgery.

Association between vascular endothelial growth factor +936 C/T gene polymorphism and age-related macular degeneration

Objectives The pathogenesis of age-related macular degeneration (AMD) remains unknown. Vascular endothelial growth factor (VEGF) is an important regulator of angiogenesis and a target for inhibition therapy in wet AMD. This study investigated the association between the VEGF +936 C/T gene polymorphism and AMD, in a Chinese Han population. Methods Patients with AMD, and age- and sex-matched controls were enrolled. Restriction fragment length polymorphism was used to analyse the VEGF +936 polymorphism in the promoter and the 3′ untranslated region of the gene. Results The study included 200 AMD patients and 200 control subjects. There was a significantly higher prevalence of the TT genotype among AMD patients (9.0%) compared with controls (3.5%); the odds ratio for this genotype in AMD patients was 2.73 (95% confidence intervals 1.11, 6.68). There were no significant associations between any genotype and AMD subphenotypic categories (early, geographic atrophy, choroidal neovascularization). Conclusions The present study findings suggested that the VEGF +936 TT genotype was associated with AMD among Han Chinese patients.

Keratoprosthesis Sterile Vitritis

Dear Editor: We had previously reported the visual rehabilitation and complications after the implantation of MICOF keratoprosthesis (The keratoprosthesis used in our hospital was developed by the Moscow Eye Microsurgery complex in Russia, hence it is called the MICOF keratoprosthesis). Retroprosthetic membrane formation and glaucoma were the most common and risk factors for the visual function. In addition, we observed the particular phenomenon of sudden sterile vitritis without the other signs of bacterial endophthalmitis. The major presenting symptom in sterile vitritis was a rapid and painless visual decline. All symptoms happened with no warning and obvious presentations. Visual function was almost completely recovered in most patients within a few weeks. Here we report our experience of 6 patients with a discussion of etiology and treatment of sudden sterile vitritis. The study protocol conformed to the tenets of the Declaration of Helsinki, and it received ethical approval from the China Eye Research Institute Review Board. A total of 96 MICOF keratoprostheses were implanted in 96 eyes of 96 patients between April 1, 2000, and May 1, 2010 in our hospital. Sterile vitritis occurred in 6 patients, 1 to 30 months postoperatively. The preoperative corneal diagnosis was alkali burn (3 eyes), Stevens-Johnson syndrome (SJS, 2 eyes), and acid burn (1 eyes). Four eyes had a history of 1–3 prior penetrating keratoplasty (PKP) surgeries. All patients presented with sudden, marked decrease in vision with little or no pain. The recovery of vision was complete in 2 to 6 weeks. The first 2 cases were treated like bacterial endophthalmitis. Both patients underwent pars plana vitrectomy as soon as the diagnosis was confirmed. Samples of vitreous cultures revealed no bacterial or fungal growth. Peribulbar injection of dexamethasone 2.5 mg, tobramycin 20 000 units, and 1% lidocaine 0.2 ml (DG mixture) and antibiotics were used in the first 3 days of the other 4 patients. Triamcinolone (40 mg) and intensive topical steroid therapy were applied then after. The recovery of vision almost to the pre-episode level was seen in the other 4 patients. Iodizedlecithin was usually a supplementary treatment to reduce the vitritis. Differential diagnosis of endophthalmitis and sterile vitritis is of much importance. Endophthalmitis is an inflammatory reaction of intraocular fluids or tissues. Since the MICOF optical cylinder is only 2.2–2.5 mm in diameter, it was difficult to find flocculent “snow flake” vitritis with slit lamp or fundoscopy in sterile vitritis. The patients always had externally quiet eyes and minor ocular complaints in association with anterior chamber cells and a dense cellular reaction in the vitreous. Sterile vitritis developed in 6.25% (6/96) of the eyes in our hospital, as compared with 5% (7/136) of the eyes in the multicenter series and 10% (5/50) in a series of patients who received the Boston type 1 keratoprosthesis between 2004 and 2008. Visual acuity (VA) came back in the 4 patients with peribulbar injection of DG mixture and triamcinolone (40 mg) in 2 to 6 weeks. Because of the concern for possible bacterial endophthalmitis, pars plana vitrectomy, and antibacterial therapy were used in the first 2 patients. Sequelae of the pars plana vitrectomy might explain the subsequent VA decline. Although sterile vitritis is a well-recognized complication after keratoprosthesis surgery, the pathogenesis is still unknown. Since the same keratoprosthesis and techniques were used in all 96 patients, it seems not to be any device-related factors contributing to this phenomenon. Considering the unlikely relationship between sterile vitritis and bacterial, this complication might be an immune phenomenon. Because of the uncertain etiology, systemic antibiotics were still recommended. However, peribulbar injection of DG mixture, triamcinolone, and intensive topical steroid might be a proper therapy in our series. Despite most patients regaining VA, sterile endophthalmitis in MICOF patients is not harmless and cold threatens prosthesis retention or function. More research needed to understand the reason for what appears to be sterile vitritis in this setting. JIFENG YU, MD YIFEI HUANG, MD, PHD JING SONG, MD LIQIANG WANG, MD FENGXIANG WANG, MD Beijing, China

Biocompatibility of helicoidal multilamellar arginine-glycine-aspartic acid-functionalized silk biomaterials in a rabbit corneal model.

Silk proteins represent a unique choice in the selection of biomaterials that can be used for corneal tissue engineering and regenerative medical applications. We implanted helicoidal multilamellar arginine-glycine-aspartic acid-functionalized silk biomaterials into the corneal stroma of rabbits, and evaluated its biocompatibility. The corneal tissue was examined after routine hematoxylin-eosin staining, immunofluorescence for collagen I and III, and fibronectin, and scanning electron microscopy. The silk films maintained their integrity and transparency over the 180-day experimental period without causing immunogenic and neovascular responses or degradation of the rabbit corneal stroma. Collagen I increased, whereas Collagen III and fibronectin initially increased and then gradually decreased. The extracellular matrix deposited on the surface of the silk films, tightly adhered to the biomaterial. We have shown this kind of silk film graft has suitable biocompatibility with the corneal stroma and is an initial step for clinical trials to evaluate this material as a transplant biomaterial for keratoplasty tissue constructs.

Changes in objective vault and effect on vision outcomes after implantable Collamer lens implantation: 1-year follow-up.

Purpose To investigate the changes in vault and the effect on visual outcomes 1 year after implantable Collamer lens (ICL) implantation. Methods In this retrospective study, 127 eyes of 66 patients undergoing ICL implantation were examined both before and up to 1 year after the surgery. The examination contents included white-to-white (WTW) diameter, central vault of the ICL (distance between posterior surface of ICL and anterior surface of crystalline lens), refractive error, and wavefront high-order aberration (HOA). All statistical analyses were performed using SPSS 13.0 software. Results A significant decrease in vault was noted up to 1 month, after which the value stabilized (p=0.001). The moderate vault decreased significantly after the first 3 months postsurgery (paired-samples t test, p<0.05). Low vault showed a tendency to increase and high vault showed a tendency to decrease, but not significantly, over time. There was no statistically significant correlation between the amount of vault and the refractive error (Pearson correlation coefficient R=0.111, p=0.473) and there was a statistically significant correlation between the vault and HOAs (R=0.304, p=0.024). Conclusions Implantable Collamer lens vault over the crystalline lens had the tendency toward a slight decrease with time and did not significantly affect the vision outcome 1 year after surgery.

Systemic application of sphingosine 1-phosphate receptor 1 immunomodulator inhibits corneal allograft rejection in mice

Purpose:  This study aims to investigate the effects of systemic application of sphingosine 1‐phosphate receptor 1(S1P1) on allogeneic corneal transplantation in mice.

Prolonging Survival of Corneal Transplantation by Selective Sphingosine-1-Phosphate Receptor 1 Agonist

Corneal transplantation is the most used therapy for eye disorders. Although the cornea is somewhat an immune privileged organ, immune rejection is still the major problem that reduces the success rate. Therefore, effective chemical drugs that regulate immunoreactions are needed to improve the outcome of corneal transplantations. Here, a sphingosine-1-phosphate receptor 1 (S1P1) selective agonist was systematically evaluated in mouse allogeneic corneal transplantation and compared with the commonly used immunosuppressive agents. Compared with CsA and the non-selective sphingosine 1-phosphate (S1P) receptor agonist FTY720, the S1P1 selective agonist can prolong the survival corneal transplantation for more than 30 days with a low immune response. More importantly, the optimal dose of the S1P1 selective agonist was much less than non-selective S1P receptor agonist FTY720, which would reduce the dose-dependent toxicity in drug application. Then we analyzed the mechanisms of the selected S1P1 selective agonist on the immunosuppression. The results shown that the S1P1 selective agonist could regulate the distribution of the immune cells with less CD4+ T cells and enhanced Treg cells in the allograft, moreover the expression of anti-inflammatory cytokines TGF-β1 and IL-10 unregulated which can reduce the immunoreactions. These findings suggest that S1P1 selective agonist may be a more appropriate immunosuppressive compound to effectively prolong mouse allogeneic corneal grafts survival.