Posterior Stroma Research Articles

Femtosecond laser–assisted descemetorhexis for Descemet membrane endothelial keratoplasty: cell-based and tissue-based ex vivo analysis of precision and safety

To analyze precision and safety of femtosecond laser-assisted descemetorhexis and postoperative corneal wound healing in human ex vivo specimens. Department of Ophthalmology, University Hospital, LMU Munich, Munich, Germany. Experimental ex vivo study. 4 donor corneas underwent femtosecond laser-assisted descemetorhexis. The descemetorhexis was performed using the LDV Z8 femtosecond laser, followed by live/dead staining, phase contrast microscopy, and scanning electron microscopy. The descemetorhexis parameters were set using a modified optical coherence tomography image capturing of 8 segments within a focus of 100 μm at the posterior corneal stroma (reversed capsulotomy program). Live/dead sample staining analysis demonstrated that the femtosecond laser had minimal impact on the vitality of surrounding endothelial cells. Phase contrast microscopy and scanning electron microscopy evaluation showed that the laser produced precise, clear-cut edges, leaving no stromal tissue bridges. Femtosecond laser-assisted descemetorhexis could serve as a safe and precise technique with only minimal endothelial cell damage. To minimize stromal damage, further laser energy profile adjustments are necessary to optimize corneal treatment within different stages of corneal tissue swelling.

Multi modal imaging in corneal edema after corneal collagen cross-linking (CXL); a case-based literature review

BackgroundKeratoconus (KCN) is a common ectatic disorder of the cornea. Corneal collagen cross-linking (CXL) is used as an effective option to slowdown the disease progression. Although CXL is considered a safe procedure, corneal endothelial damage, especially in corneal thickness of less than 400 μm, has been reported.Case presentationA 25-year-old man known case of KCN was referred with complaints about blurred vision and discomfort of the right eye 3 days after performing CXL. The preoperative thinnest point was 461 μm. His presenting BCVA was CF at 1 m. Examination showed central corneal edema and stromal haziness. ASOCT demonstrated increased central corneal thickness and very deep CXL line. In the confocal scan, anterior stroma showed hyper-reflective lines without recognizable cells and nerves, the middle stroma showed rare active and edematous keratocytes and a hyper-reflective reticular pattern with elongated keratocytes and needle-like structures involving the posterior stroma indicated increased depth of CXL. To manage the patient, debridement of loosened epithelium was done. Non-preservative steroid 1% eye drop was prescribed frequently. The corneal edema was completely resolved during 2 months with no need for surgical procedure and BCVA of 20/30 in his right eye.ConclusionThe corneal thickness of more than 400 μm cannot guarantee the absence of corneal edema after corneal collagen cross-linking, which can pertain to several factors such as inadvertently using of higher energy as well as the incorrect observance of all guidelines, instructions, and other precautions, even by a trained surgeon.

Corneal biomechanical properties following corneal cross-linking: Does age have an effect?

PurposeTo explore the effect of age on corneal biomechanical properties following corneal cross-linking (CXL). MethodsA total of 12 pairs of human eye-banked corneas (24 corneas, from 14 females and 10 males) were used in the study. The mean donor age was 48.5 years (ranging from 26 to 71 years). Corneas were divided into three age groups: A (26–41 years), B (42–57 years) and C (58–71 years), with four pairs in each group. For each pair, the right corneas were cross-linked using accelerated CXL with UVA (10 mW/cm2) and riboflavin, while the left corneas served as controls and were not exposed to either UVA irradiation or riboflavin. The corneal elastic modulus of the anterior, mid and posterior corneal stroma was measured using nanoindentation. ResultsThe difference in the corneal elastic modulus following CXL was significant in the anterior (p = 0.00002) and mid stroma (p = 0.001); however, the difference was not significant in the posterior stroma (p = 0.27) when compared to control corneas. The corneal elastic modulus of the anterior stroma increased by 178.44% in Group A, 119.7% in Group B and 50.73% in Group C compared to control corneas. For the mid stroma, the elastic modulus increased by 47.35% in Group A, 25% in Group B and 24.56% in Group C. No differences were observed in the posterior stroma between age groups. ConclusionsCorneal elasticity showed a greater response to CXL in the younger group compared to older groups. CXL treatment showed effectiveness in enhancing stromal strength, and the effect was concentrated in the anterior and mid stroma with minimal impact on the posterior stroma in all age groups.

Descemet's membrane injury and regeneration, and posterior corneal fibrosis, in rabbits

The purpose of this investigation was to study Descemet's membrane and corneal endothelial regeneration, myofibroblast generation and disappearance, and TGF beta-1 localization after Descemet's membrane-endothelial excision (Descemetorhexis) in rabbits. Thirty-six rabbits had 8 mm Descemetorhexis and standardized slit lamp photos at 1, 2 and 4 days, 1, 2 and 4 weeks, and 2, 4 and 6 months, as well as multiplex IHC for stromal cell markers keratocan, vimentin, and alpha-smooth muscle actin (SMA); basement membrane (BM) components perlecan, nidogen-1, laminin alpha-5, and collagen type IV; and corneal endothelial marker Na,K-ATPase β1, and TGF beta-1, with ImageJ quantitation. Stromal transparency increased from the periphery beginning at two months after injury and progressed into the central cornea by six months. At six months, central transparency was primarily limited by persistent mid-stromal neovascularization. Stromal myofibroblast zone thickness in the posterior stroma peaked at one month after injury, and then progressively decreased until to six months when few myofibroblasts remained. The regeneration of a laminin alpha-5 and nidogen-1 Descemet's membrane “railroad track” structure was accompanied by corneal endothelial closure and stromal cell production of BM components in corneas from four to six months after injury. TGF beta-1 deposition at the posterior corneal surface from the aqueous humor peaked at one day after Descemetorhexis and diminished even before regeneration of the endothelium and Descemet's membrane. This decrease was associated with collagen type IV protein production by corneal fibroblasts, and possibly myofibroblasts, in the posterior stroma. Descemet's membrane and the corneal endothelium regenerated in the rabbit cornea by six months after eight mm Descemetorhexis. Real-time quantitative RT-PCR experiments in vitro with marker-verified rabbit corneal cells found that 5 ng/ml or 10 ng/ml TGF beta-1 upregulated col4a1 or col4a2 mRNA expression after 6 h or 12 h of exposure in corneal fibroblasts, but not in myofibroblasts. Stromal cells produced large amounts of collagen type IV that likely decreased TGF beta-1 penetration into the stroma and facilitated the resolution of myofibroblast-generated fibrosis.

Refractive changes of a new asymmetric intracorneal ring segment with variable thickness and base width: A 2D finite-element model.

PurposeTo evaluate the local geometric effects of a unilateral intrastromal ring segment with a combined variation of ring thickness and base width in a finite element simulation, and to compare it against the isolated effect of thickness or base width variation alone.MethodsA two-dimensional finite-element model of a transversely isotropic cornea was created assuming either axisymmetric stress or plane strain condition. The model geometry was composed of a three-layered corneal tissue (epithelium, anterior and posterior stroma) fixed at the limbus. The implantation of a triangular-shape asymmetric ring segment with varying ring thickness (150 to 300 μm) and base width (600 to 800 μm) was simulated. Also, changes induced by thickness or base width alone were studied and compared their combined effect in the asymmetric ring segment. Geometrical deformation of the simulated cornea and sagittal curvature were the main parameters of study.ResultsIncreasing ring thickness and base width along the arc of the asymmetric ring segment produced a more pronounced flattening in this part of the ring. The asymmetric design did find a good balance between maximizing corneal flattening at one end and minimizing it at the other end, compared to the isolated effect of ring thickness and width. Ring thickness was the most robust parameter in flattening both, the central and peripheral cornea.ConclusionThe finite-element model permitted a theoretical study of corneal deformation undergoing implantation of realistic and hypothetical ring geometries. Intracorneal asymmetric ring segments with varying thickness and base width can be a good alternative in corneas with asymmetric keratoconus phenotypes.

Structural Changes in Thin Keratoconic Corneas Following Crosslinking with Hypotonic Riboflavin: Findings on In Vivo Confocal Microscopy.

PurposeTo report structural changes observable in in vivo confocal microscopy (IVCM) in keratoconic corneas 400 μm treated with hypotonic riboflavin and collagen crosslinking (CXL).MethodsTen eyes of ten patients with progressive keratoconus and corneal thickness between 350 and 399 μm underwent CXL with hypotonic riboflavin. IVCM was performed preoperatively and at one month, three months, and six months after the procedure.ResultsIVCM analysis one month postoperatively showed complete absence of the subepithelial nerve plexus with gradual regeneration over six months in 8 of the 10 eyes, and poor regeneration in the remaining 2 eyes. The anterior stroma showed extracellular lacunae and hyper-reflective cytoplasm in a honeycomb appearance signifying edema at one month which gradually decreased over six months post CXL. Stromal keratocyte apoptosis was evident in the anterior stroma in all cases and extended to the posterior stroma in four eyes with gradual regeneration evident at three and six months. The specular endothelial count decreased by 8% (P = 0.005) post-CXL, but no corneas developed clinical signs of endothelial trauma.ConclusionIVCM analysis of thin corneas after hypotonic CXL showed posterior corneal structural changes. Posterior stromal changes were accompanied by a decrease in the endothelial cell count. This case series was a preliminary feasibility study that might necessitate conducting a well-designed controlled study.

Birefringence Analyses Reveal Differences in Supramolecular Characteristics of Corneal Stromal Collagen Fibrils Between Falconiformes and Strigiformes.

This study aimed to assess the birefringent properties of corneal stromal collagen fibrils in birds of the orders Falconiformes (diurnal) and Strigiformes (predominantly nocturnal) to compare their supramolecular organizations. In total, 22 corneas of Falconiformes (Caracara plancus, n=8; Rupornis magnirostris, n=10; and Falco sparverius, n=4) and 28 of Strigiformes (Tyto furcata, n=16; Pseudoscops clamator, n=6; and Athene cunicularia, n=6) were processed histotechnically into 8-μm thick sections. Corneal optical retardation (OR) values related to the form and intrinsic fractions of the total birefringence of collagen fibrils were measured using a polarized light microscope equipped with phase compensators. In addition, the coherence coefficients that inform the local orientation of the fibrils were calculated through video image analysis. All assessments were conducted both in the anterior and posterior stroma of the cornea. Differences were significant when P<0.05. The results showed supraorganizational differences between fibrils in the anterior stroma of Falconiformes and Strigiformes. The OR values were greater (P<0.0001) for Falconiformes, indicating that the corneas of these birds contain more collagen fibrils or more aggregated collagen fibrils. In contrast, the coherence coefficients were higher (P=0.016) for Strigiformes, indicating that the corneal collagen fibers in these birds are highly aligned and have few undulations. A multivariate data matrix constructed for Euclidean distance calculations showed that the dissimilarity between Falconiformes and Strigiformes corneas, in terms of the supraorganization of stromal collagen fibrils, was 4.56%. In conclusion, it is possible that the supraorganizational differences reported in this study may be sources of variation in the visual quality of Falconiformes and Strigiformes. This study provides the necessary evidence to encourage further research associating corneal optical performance to supramolecular characteristics of corneal stromal collagen.

Corneal Optical Coherence Tomography Speckle in Crosslinked and Untreated Rabbit Eyes in Response to Elevated Intraocular Pressure

PurposeTo ascertain the influence of intraocular pressure (IOP) on corneal optical coherence tomography (OCT) speckle in untreated and ultraviolet A–riboflavin induced corneal collagen crosslinked rabbit eyes.MethodsLeft corneas of eight rabbits were de-epithelialized and crosslinked by applying riboflavin and 30-minute ultraviolet A light exposure. After enucleation (6 months after treatment), each eyeball (treated and untreated) was mounted in a measurement setup, in which IOP was increased from 15 to 45 mm Hg in steps of 5 mm Hg. At each IOP value, single B-scans of the central cornea were acquired three times with the spectral-domain OCT Copernicus-HR. Then, three regions of interest, including the anterior, posterior, and entire corneal stroma, were automatically extracted. Five different probability distributions were used as a model for the corneal speckle and the one with the best goodness of fit was chosen for further analysis.ResultsThe generalized gamma distribution achieved the best goodness of fit and its scale (a) and shape (v) parameters statistically significantly changed with increasing IOP in the three regions of analysis (two-way repeated measures analysis of variance, all P < 0.05). The statistically significant difference between untreated and crosslinked eyes was observed for the shape parameters of the posterior and entire corneal stroma.ConclusionsCorneal OCT speckle is influenced by IOP and shows to be significantly different in untreated and crosslinked eyes. Corneal OCT speckle analysis has the potential to be indirectly used for assessing changes in corneal stroma in ex vivo and in vivo studies.Translational RelevanceInvestigation of corneal OCT speckle statistics can offer additional diagnostic biomarkers related to changes in the corneal stroma after ocular surgeries.

Evaluating the safety and efficacy of compression sutures with intracameral perfluoropropane (C3F8) in the management of acute corneal hydrops.

To evaluate the safety and efficacy of using corneal compression sutures with intracameral perfluoropropane (C3F8) in patients presenting with acute corneal hydrops in ectatic disorders. A retrospective analysis was done for 43 eyes of patients of acute corneal hydrops, managed using a combination of intracameral 14% C3F8 and full-thickness compression sutures. Time for resolution of edema, corneal thickness (CT) change on anterior segment ocular coherence tomography (ASOCT), and visual outcomes were assessed. Corneal edema resolved with a mean duration of 14.8 ± 3.5days (range 10-21). The mean CT on ASOCT decreased from a mean of 1437µm (689-2770µm) preoperatively to 543µm (434 -66µm) on the complete resolution of corneal edema. Our results suggest that full-thickness compression sutures and intracameral C3F8 injection can restore the imperviousness of posterior stroma. This technique appears to be a safe and effective technique for faster resolution of corneal edema post hydrops.

Corneal Keratocyte Density and Corneal Nerves Are Reduced in Patients With Severe Obesity and Improve After Bariatric Surgery.

PurposeObesity is associated with peripheral neuropathy, which bariatric surgery may ameliorate. The aim of this study was to assess whether corneal confocal microscopy can show a change in corneal nerve morphology and keratocyte density in subjects with severe obesity after bariatric surgery.MethodsTwenty obese patients with diabetes (n = 13) and without diabetes (n = 7) underwent assessment of hemoglobin A1c (HbA1c), lipids, IL-6, highly sensitive C-reactive protein (hsCRP), and corneal confocal microscopy before and 12 months after bariatric surgery. Corneal nerve fiber density (CNFD), corneal nerve branch density (CNBD), corneal nerve fiber length (CNFL), and keratocyte density (KD) from the anterior, middle, and posterior stroma were quantified. Twenty-two controls underwent assessment at baseline only.ResultsCNFL (P < 0.001), CNBD (P < 0.05), and anterior (P < 0.001), middle (P < 0.001), and posterior (P < 0.001) keratocyte densities were significantly lower in obese patients compared to controls, and anterior keratocyte density (AKD) correlated with CNFL. Twelve months after bariatric surgery, there were significant improvements in body mass index (BMI; P < 0.001), HDL cholesterol (P < 0.05), hsCRP (P < 0.001), and IL-6 (P < 0.01). There were significant increases in CNFD (P < 0.05), CNBD (P < 0.05), CNFL (P < 0.05), and anterior (P < 0.05) and middle (P < 0.001) keratocyte densities. The increase in AKD correlated with a decrease in BMI (r = –0.55, P < 0.05) and triglycerides (r = –0.85, P < 0.001). There were no significant correlations between the change in keratocyte densities and corneal nerve fiber or other neuropathy measures.ConclusionsCorneal confocal microscopy demonstrates early small fiber damage and reduced keratocyte density in obese patients. Bariatric surgery leads to weight reduction and improvement in lipids and inflammation and an improvement in keratocyte density and corneal nerve regeneration.

Corneal Remodeling in Peters Anomaly

A 14-day-old girl presented with bilateral opaque corneas and raised intraocular pressure (Fig A). Ultrasound biomicroscopy showed a well-defined central defect in the Descemet membrane and posterior corneal stroma (Fig B, arrows), with cystic intrastromal fluid clefts (Fig B, stars). Her diagnosis was Peters anomaly with glaucoma, and she underwent bilateral combined trabeculotomy with trabeculectomy. After 4 months follow-up, there was a significant improvement in peripheral cornea clarity, with persistent central corneal opacity (Fig C).

Secondary Descemet Stripping Automated Endothelial Keratoplasty without Removing the Previously Grafted Posterior Stroma

ëª©ì  데스메막박리자동내피각막이식(descemet stripping automated endothelial keratoplasty, DSEAK) 시행 ê³¼ì • 중 ì´ì „ 이식된 각막편의 ì œê±°ê°€ ì™„ì „í•˜ê²Œ 되지 않은 채 시행된 DSAEK에서 이식된 공여각막이 잘 ìœ ì§€ë˜ì—ˆë˜ 증례를 ë³´ê³ í•˜ê³ ìž 한다. 증례요약 72세 남자 환자가 우안 수포각막병증 소견으로 각막이식을 위해 의뢰되었다. 양안 백내장 및 ì„¬ìœ ì£¼ì ˆì œìˆ ì„ 받은 ì  있으며, 2ë „ ì „ 우안 DSEAK ë³‘ë ¥ì´ 있었다. DSAEK시 ì´ì „ì— 이식되어 있던 각막이식편을 ì œê±°í•˜ë ¤ê³ í•˜ì˜€ìœ¼ë‚˜, 후부각막실질의 ì œê±°ê°€ 용이하지 않아 이를 남겨둔 채 새로운 공여각막을 ì „ë°©ì— ì£¼ìž í•œ 뒤 ë¬´ê· ê³µê¸°ë¥¼ ì£¼ìž í•˜ì—¬ 각막을 ìœ ì°©ì‹œì¼°ë‹¤. ìˆ í›„ 6시간 앙와위 자세를 ìœ ì§€í•˜ì˜€ìœ¼ë©°, í•­ìƒì œ 및 ìŠ¤í Œë¡œì´ë“œ 안약을 ì ì•ˆí•˜ë©´ì„œ 경과 관찰하였다. ìˆ í›„ 3개월의 경과 관찰 기간 동안 각막 íˆ¬ëª ë„ëŠ” 잘 ìœ ì§€ë˜ì—ˆìœ¼ë©°, 각막단층촬영검사상 이식된 각막편은 잘 ìœ ì°©ëœ 상태로 관찰되었다. ê²°ë¡ ì´ì „ 각막이식편의 ì™„ì „í•œ ì œê±°ê°€ 힘들 경우 ì´ì „ 이식편 후부각막실질을 그대로 둔 채 DSAEK을 시행하더라도 합병증 없이 공여각막의 ìœ ì°©ì„ ê¸°ëŒ€í• ìˆ˜ 있을 것으로 사료된다. Keywords: Corneal endothelium, Corneal transplantation, Descemet stripping automated endothelial keratoplasty

Comparing Corneal OCT Findings in High Irradiance Corneal Crosslinking Combined with Femtosecond Laser In Situ Keratomileusis versus Femtosecond Laser In Situ Keratomileusis

Objective: To study Corneal OCT findings in the interface and the demarcation line under or over the interface in patients that undergo Femtosecond laser in situ Keratomeulisis compared to patients that undergo Femtosecond laser in situ Keratomeulisis combined with high irradiance corneal cross linking (Femto-Lasik Xtra). Study Design: Prospective Randomized Comparative Study. Methods: Our study included 40 eyes of 20 patients divided into 2 groups, a group of 10 patients with 20 eyes underwent Femto-Lasik &amp; the other group of 10 patients of 20 eyes underwent Femto-Lasik Xtra. The Femto Lasik procedure was done using Alcon Wave Light FS200 laser machine. The Femto-Lasik XTRA procedure entails the administration of half fluence high irradiance cross-linking subsequent to refractive correction. A higher concentration 0.25% riboflavin is applied on the stromal bed and the flap subsequent to laser ablation with a soak time of 90 seconds, UV-A irradiance is delivered as a homogenous beam of 30 mW/cm2 for 90 s to deliver a total fluence of 2.7J/cm2. Patients were randomly observed and HEIDELBERG ASOCT was performed after 1 week, 1 month &amp; 3 months post-operative. Results: A demarcation line was noted in femto Lasik Xtra patients, appeared more evident in the peripheral cornea and faded as it approached the central cornea. It became less evident after 1 month and 3 months period respectively. Also the flap hinge was more hyper reflective and evident in femto Lasik Xtra patients when compared to femto Lasik patients. Anterior crosslinked stroma appeared more hyper reflective than posterior stroma in femto Lasik Xtra patients. Flap edge was also more hyper reflective and better demarked in femto Lasik Xtra treated corneas when compared to femto Lasik treated corneas. Conclusion: AS-OCT showed significant differences between femto Lasik and Femto Lasik Xtra treated corneas. Significant changes were noted in the demarcation line in Femto Lasik Xtra patients along different time periods post-operative.

Use of viscoelastic substance for preventing Descemet's membrane rupture in deep anterior lamellar keratoplasty.

This study aimed to investigate the effect of using a viscoelastic substance in Descemet's membrane rupture in "double bubble" deep anterior lamellar keratoplasty. The medical records and videos of surgeries of 40 patients who underwent surgery between January 2014 and July 2015 were retrospectively evaluated. The patients were divided into two groups: 20 patients whose perforation of the posterior stromal wall was performed without administration of any viscoelastic substance (group 1) and 20 patients whose perforation of the posterior stromal wall was performed with administration of viscoelastic substance onto the posterior stroma (group 2). The Descemet's membrane perforation rate was compared between groups. Perforation of the Descemet's membrane was observed in 12 (60.0%) patients in group 1 and only three (15.0%) patients in group 2. This difference was statistically significant (p=0.003). Only one (5%) patient in group 2 had macroperforation during the procedure, and the surgery was converted to penetrating keratoplasty. Eleven (55.0%) patients in group 1 had macroperforation of Descemet's membrane, and surgeries were converted to penetrating keratoplasty. This difference between the groups was statistically significant (p=0.001). Administering a viscoelastic substance onto the posterior stromal side just before puncture is an effective method to decrease the risk of Descemet's membrane perforation in deep anterior lamellar keratoplasty.

A study on outcome of penetrating keratoplasty in various types of corneal pathologies

Introduction: Penetrating keratoplasty involves surgical removal of diseased or damaged cornea from the host and replacement with a full thickness donor cornea. The major goals of penetrating keratoplasty are to improve visual acuity, to maintain the integrity of the eye and to treat various infection or neoplastic conditions. Depending on the location of the corneal abnormality, it may be sufficient to replace the anterior corneal layers (anterior lamellar keratoplasty) or the posterior corneal stroma and endothelium (posterior lamellar keratoplasty or descements stripping endothelial keratoplasty or descements stripping endothelial keratoplasty). Materials and Methods: This study has been done in department of Ophthalmology, Pt. J.N.M. Medical College, Raipur (C.G) from July 2009 to October 2010 and consists of group of patients attending eye OPD and admitted in department of ophthalmology. All patients included in the study were enquired about their history of diminution of vision, previous surgery, duration and any other associated symptoms. The patients underwent a detailed preoperative examination including visual acuity measurement with snellen’s chart, retinoscopy and subjective correction and slit lamp biomicroscopy. Observations: Among 40 patients 23 were male and 17 were female maximum patients were above 40 years of age. Out of 40 cases (100%), 23 cases (57.5%) were therapeutic and 17 cases (42.5%) were optical purpose. The mean age of the donor cornea was (61-80 years) age group which is used in 65% (26) cases. Maximum cases (40%) had corneal ulcer followed by corneal opacity (35%) and adherent leucoma (17%). Out of 40 cases in 32 cases of PKP shows complications. Improvement in visual acuity was seen in majority of cases. Conclusion: In this study we concluded that penetrating keratoplasty is most useful to save vision and structural integrity in case of corneal blindness. Keywords: Corneal pathologies, Penetrating keratoplasty, Visual acuity.

Brillouin microscopic depth-dependent analysis of corneal crosslinking performed over or under the LASIK flap.

To determine the impact of corneal crosslinking (CXL) performed over the laser in situ keratomileusis (LASIK) flap using the Standard CXL (S-CXL) protocol or under the flap after flap lift (flap-CXL) on regional corneal stiffness using Brillouin microscopy. University of Southern California Keck School of Medicine, Los Angeles, California, and Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, USA. Laboratory ex vivo experiment. After epithelium debridement, LASIK flaps were created on intact fresh porcine eyes with a mechanical microkeratome. Then, S-CXL (riboflavin applied to the corneal surface followed by 3 mW/cm ultraviolet exposure with the flap in place for 30 minutes) or flap-CXL (riboflavin applied to the stromal bed after reflecting the flap followed by the same ultraviolet A exposure with the flap replaced) was performed. Depth profile of stiffness variation and averaged elastic modulus of anterior, middle, and posterior stroma were determined by analyzing Brillouin maps. Each eye served as its own control. The study was performed on 24 fresh porcine eyes. S-CXL had maximal stiffening impact in the anterior most corneal stroma within the LASIK flap (8.40 ± 0.04 GHz), whereas flap-CXL had lower maximal stiffening impact (8.22 ± 0.03 GHz) (P < .001) that occurred 249 ± 34 μm under the corneal surface. S-CXL increased longitudinal modulus by 6.69% (anterior), 0.48% (middle), and -0.91% (posterior) as compared with flap-CXL, which increased longitudinal modulus by 3.43% (anterior, P < .001), 1.23% (middle, P < .1), and -0.78% (posterior, P = .68). The S-CXL technique generated significantly greater stiffening effect in the anterior cornea than a modified protocol with riboflavin administration under the flap (flap-CXL). Minimal stiffening occurred in the middle or posterior cornea with either protocol.

Femtosecond Laser-Assisted Allogenic Lenticule Implantation for Corneal Ectasia After LASIK: A 3-Year In Vivo Confocal Microscopic Investigation.

To investigate morphological changes in the cornea and the implanted lenticule in patients with corneal ectasia after laser in situ keratomileusis (LASIK) and implantation using a lenticule from small incision lenticule extraction (SMILE). Eight eyes of 8 patients with ectasia after LASIK from 2015 to 2018 at the Eye and ENT Hospital of Fudan Unversity were analyzed. For recipient eyes, lenticules were transferred with a mean cryopreserved time of 20 ± 21 days extracted from SMILE donors to the exposed stromal bed after lifting the flaps and the flap was repositioned. Uncorrected and corrected distance visual acuity, manifest refraction, and corneal topography were performed. Patients were followed up for 3 years. Changes in lenticules and recipient corneas were analyzed using in vivo confocal microscopy. Activated keratocytes in the anterior and posterior stroma were observed near the lenticule at the first 6 months. Elongated, deformed keratocyte nuclei were found in the implanted lenticules in postoperative year 1. The anterior and posterior interfaces showed an absence or decrease of keratocytes and the presence of small particles of varying brightness. Nerve fibers in the implanted lenticules were detected in one case. No obvious difference was detected between cryopreserved and fresh lenticules. The preliminary findings suggest that recipient keratocytes repopulate the lenticules and the keratocytes in lenticules gradually return to their normal morphology. [J Refract Surg. 2020;36(11):714-722.].

Ocular surface analysis in patients diagnosed with X-linked ichthyosis

Seven patients (14 eyes) diagnosed with X-linked ichthyosis were studied using the Schirmer test, biomicroscopy, tonometry, endothelial count, optical coherence tomography, Pentacam®, ocular surface analyser, and confocal microscopy. The mean age was 33.83±20.17 years (range: 7-64 years). The most frequent findings in biomicroscopy were Meibomian glands dysfunction (83.3%) and stromal corneal opacities (33%). The tear break-up time was found shortened in 25% of the eyes. Confocal microscopy (both eyes) revealed activated keratocytes with hyper-reflective particles inside them in the anterior stroma and outside them in the posterior stroma. It is believed that the inclusion of the use of confocal microscopy will help in a better understanding of the corneal pathology associated with ichthyosis X, as well as new characteristics of these patients.

Iridoschisis-A Systematic Review.

Iridoschisis is a rare condition defined as a separation of the anterior iris stroma from the posterior stroma and muscle layers. In this paper, we review current data about the epidemiology, pathophysiology, clinical characteristics and differential diagnoses of this condition and discuss the specificity of surgical treatment of concomitant ocular diseases in iridoschisis patients. Iridoschisis may pose a challenge for both an ophthalmologist in an outpatient setting and an ophthalmic surgeon. Glaucoma, primarily angle-closure glaucoma, is the most often described condition concomitant to iridoschisis. Other ocular abnormalities found relatively often in iridoschisis patients include cataract, lens subluxation and corneal abnormalities. Special attention has been paid to potential complications of cataract surgery and prevention thereof. Beside addressing the practical aspects, we point to discrepancies and suggest topics for further investigation.

The effect of high-fat diet-induced metabolic disturbance on corneal neuroimmune features

PurposeThe highly innervated cornea is susceptible to nerve loss secondary to systemic diseases such as diabetes and metabolic disturbances caused by high-fat diet. In this study, we characterize the effect of high-fat diet on the mouse corneal neuroimmune phenotype, including changes to corneal nerve density and resident immune cells, alongside the clinical assessment of corneal thickness and endothelial cell density. MethodsMale C57Bl6/J mice, aged 10 weeks, were fed a high-fat diet (60 kcal% fat, 5.2 kcal/g) or control diet (10 kcal%, 3.8 kcal/g) for 16 weeks. At the study endpoint, metabolic parameters (HbA1c, weight, fasting glucose, body fat) were measured to confirm metabolic disturbance. Clinical imaging of the anterior segment was performed using optical coherence tomography to measure the corneal epithelial and stromal thickness. Corneal sensory nerves were visualized using flatmount immunostaining and confocal microscopy. The topographical distribution and density of sensory nerves (BIII-tubulin+), intraepithelial CD45+ and MHC- II+ cells, stromal macrophages (IBA1+CD206+) and endothelial cells (ZO-1+) were analysed using FIJI. ResultsHigh-fat diet mice had significantly higher blood HbA1c, higher body weight, a higher percentage of body fat and elevated fasting glucose compared to the control diet mice. Corneal epithelial and stromal thickness was similar in both groups. The sum length of the basal nerve plexus was lower in the central and peripheral cornea of mice fed a high-fat diet. In contrast, the sum length of superficial nerve terminals was similar between groups. Epithelial immune cell density was two-fold higher in the central corneas of high-fat diet mice compared to control diet mice. IBA1+CD206+ macrophage density was similar in the anterior stroma of both groups but was significantly higher in the posterior stroma of the peripheral cornea in the high-fat diet mice compared to controls. The percentage of nerve-associated MHC-II+ cells in the epithelium and stroma was higher in HFD mice compared to controls. Endothelial cell density was similar in the corneas of high-fat diet mice compared to controls. ConclusionTogether with corneal neuropathy, corneal immune cells in mice fed a high-fat diet were differentially affected depending on their topographical distribution and location within cornea, and appeared in closer proximity to epithelial and stromal nerves, suggesting a local neuroimmune disruption induced by systemic metabolic disturbance.