A new method for in vivo assessment of corneal transparency using spectral-domain OCT.

Corneal transparency is essential to provide a clear view into and out of the eye, yet clinical means to assess such transparency are extremely limited and usually involve a subjective grading of visible opacities by means of slit-lamp biomicroscopy. Here, we describe an automated algorithm allowing extraction of quantitative corneal transparency parameters with standard clinical spectral-domain optical coherence tomography (SD-OCT). Our algorithm employs a novel pre-processing procedure to standardize SD-OCT image analysis and to numerically correct common instrumental artifacts before extracting mean intensity stromal-depth (z) profiles over a 6-mm-wide corneal area. The z-profiles are analyzed using our previously developed objective method that derives quantitative transparency parameters directly related to the physics of light propagation in tissues. Tissular heterogeneity is quantified by the Birge ratio Br and the photon mean-free path (ls) is determined for homogeneous tissues (i.e., Br~1). SD-OCT images of 83 normal corneas (ages 22-50 years) from a standard SD-OCT device (RTVue-XR Avanti, Optovue Inc.) were processed to establish a normative dataset of transparency values. After confirming stromal homogeneity (Br <10), we measured a median ls of 570 µm (interdecile range: 270-2400 µm). By also considering corneal thicknesses, this may be translated into a median fraction of transmitted (coherent) light Tcoh(stroma) of 51% (interdecile range: 22-83%). Excluding images with central saturation artifact raised our median Tcoh(stroma) to 73% (interdecile range: 34-84%). These transparency values are slightly lower than those previously reported, which we attribute to the detection configuration of SD-OCT with a relatively small and selective acceptance angle. No statistically significant correlation between transparency and age or thickness was found. In conclusion, our algorithm provides robust and quantitative measurements of corneal transparency from standard SD-OCT images with sufficient quality (such as 'Line' and 'CrossLine' B-scan modes without central saturation artifact) and addresses the demand for such an objective means in the clinical setting.

Long-term outcomes of deep anterior lamellar versus penetrating keratoplasty for keratoconus.

AIMS: To compare the long-term outcomes of deep anterior lamellar keratoplasty (DALK) with penetrating keratoplasty (PK) in keratoconus. METHODS: Retrospective comparative case series (228 DALKs and 274 PKs). A biphasic linear model was used to describe the postoperative outcome of the endothelial cell density (ECD). Visual acuity, specular microscopy, corneal topography and optical coherence tomography findings were recorded. RESULTS: Graft survival of the 502 keratoconus eyes was 96.7 at 10 years and 95.6% at 20 years. Visual acuity improved from 20/378±5.1 lines preoperatively to 20/32±2.1 lines at 30 months. The corneal ECD decreased from 2494±382 cells/mm2 to 1521±659 cells/mm2 at 10 years. The mean simulated keratometry increased from 44.88±2.54 D at 1 year to 46.60±3.0 D at 3 years. The mean follow-up was 103.4 months for DALKs and 106.1 months for PKs. The cumulated incidence of postoperative ocular hypertension requiring treatment was significantly higher in PKs than in DALKs. The early- and late-phase rates of ECD loss were significantly lower in DALKs than in PKs. These figures in DALKs were 50% of those observed in PKs. The simulated mean keratometry was significantly higher in DALKs than in PKs in the mid but not in the long term. No significant differences in visual acuity were observed between both groups. Manual dissection-DALK featured slower visual recovery than PK and big bubble-DALK, whereas big bubble-DALK and PK featured similar visual recovery. CONCLUSIONS: DALK featuring higher endothelial survival and lower risk of postoperative ocular hypertension may be superior to PK when indicated for keratoconus.

Freeze-dried amniotic membrane graft with a spongy layer in bilateral peripheral ulcerative keratitis: a case report.

BACKGROUND: Peripheral ulcerative keratitis (PUK) is a group of inflammatory corneal ulcers with stromal thinning and peripheral localization. Amniotic membranes (AM) are used for their anti-inflammatory and healing properties. A freeze-drying process now allows maintaining the AM viable for a long time at room temperature without altering its physical, biological, and morphologic characteristics. The effectiveness of spongy freeze-dried amniotic membrane (FD-AM) graft with multimodal imaging in the management of severe corneal thinning PUK has not been reported. CASE PRESENTATION: A 67-year-old Caribbean man histologically diagnosed with ulcerative colitis, was referred to our tertiary eye care center for a deep nasal juxtalimbal ulcer of the left eye. He was treated with topical steroids and antibiotics, methylprednisolone pulses, and oral prednisone. Due to continuous stromal thinning with 100 µm of residual corneal thickness, the decision was made to perform surgery. Conjunctival resection, inlay and overlay spongy FD-AM (Visio Amtrix® S, Tissue Bank of France, FR) were performed to preserve globe integrity. Despite tapering off oral steroids, PUK developed in the fellow eye on the 2 months follow-up. Treatment with human monoclonal antibody against tumor necrosis factor-alpha was initiated to control the active underlying inflammation. Six months following surgery, the ulcer was healed and corneal thickness in front of the former ulceration was measured at 525 µm on anterior segment-optical coherence tomography. Confocal microscopy confirmed the integration of the amniotic membrane between the corneal epithelium and the anterior stroma. CONCLUSION: Transplantation of FD-AM with a spongy layer was associated with restoration of normal corneal thickness in the PUK area. It seems to be a safe, effective, and easily accessible solution for the surgical management of PUK with impending perforation.

Comprehensive Assessment of Corvis ST Biomechanical Indices in Normal and Keratoconus Corneas with Reference to Corneal Enantiomorphism.

The aim of this study was to assess Corvis ST biomechanical indices in reference to corneal enantiomorphism. In a prospective observational cohort study, 117 eyes from 63 patients with normal or keratoconus corneas were assessed by three independent observers. In the control group (n = 62), no significant differences were observed between the three observers for all indices. The best reproducibility was obtained with pachymetry and the weakest with CBI. All indices but CBI and arc length featured COV < 10%. All indices except the PD and SSI correlated with pachymetry; all but Rad correlated with IOP. The comparison of the thinnest with the thickest corneas showed no significant differences for any index except pachymetry. In the keratoconus group (n = 55), loss of corneal enantiomorphism was confirmed for all indices except the arc length, velocity, and PD. Significant differences between both groups were found for all indices, even after adjustment for pachymetry and intraocular pressure. The CBI featured the best accuracy (92%), sensitivity (91%), and graphical relevance for keratoconus diagnosis. However, its reproducibility was weak in normal corneas and was strongly dependent on corneal thickness. The SSI was independent of corneal thickness, highly reproducible, and provided the expected enantiomorphism characteristics in both groups, making it a relevant biomarker of biomechanical corneal behavior.

Full-field Optical Coherence Microscopy for Histology-like Analysis of Stromal Features in Corneal Grafts.

The quality of donor corneal stroma, which makes up about 90% of total corneal thickness, is likely to be one of the main, if not the major, limiting factor(s) for success of deep anterior lamellar and penetrating keratoplasty. These are surgical procedures that involve replacing part or all of the diseased corneal layers, respectively, by donated tissue, the graft, taken from a recently deceased individual. However, means to evaluate stromal quality of corneal grafts in eye banks are limited and lack the capability of high-resolution quantitative assessment of disease indicators. Full-field optical coherence microscopy (FF-OCM), permitting high-resolution 3D imaging of fresh or fixed ex vivo biological tissue samples, is a non-invasive technique well suited for donor cornea assessment. Here we describe a method for the qualitative and quantitative analysis of corneal stroma using FF-OCM. The protocol has been successfully applied to normal donor corneas and pathological corneal buttons, and can be used to identify healthy and pathologic features on both the macroscopic and microscopic level, thereby facilitating the detection of stromal disorders that could compromise the outcome of keratoplasty. By improving the graft quality control, this protocol has the potential to result in better selection (and rejection) of donor tissues and hence decreased graft failure.

Corneal Epithelial Thickness Mapping in the Diagnosis of Ocular Surface Disorders Involving the Corneal Epithelium: A Comparative Study.

PURPOSE: The purpose of this study was to analyze the role of corneal epithelial thickness (ET) mapping provided by spectral domain optical coherence tomography in the diagnosis of ocular surface disorders (OSDs) involving the corneal epithelium. DESIGN: This was a retrospective comparative study. METHODS: Institutional settings are as follows. Study population includes 303 eyes with an OSD and 55 normal eyes (controls). Observation procedures include spectral domain optical coherence tomography with epithelial mapping in the central 6 mm. Main outcome measures include ET map classification (normal, doughnut, spoke-wheel, localized/diffuse, and thinning/thickening patterns) and ET data and statistics (minimum, maximum, and SD). A quantitative threshold was determined with receiver operating curves to distinguish pathological from normal corneas. Sensitivity and specificity of classification and quantitative data were calculated using all eyes to assess the ability to distinguish corneas with a given corneal disorder from other conditions. RESULTS: Classification of full agreement between 3 readers was obtained in 75.4% to 99.4% of cases. Main OSD features were keratoconus (135 eyes), doughnut pattern (sensitivity/specificity = 56/94%), and max-min ET ≥ 13 µm (84/43%); limbal deficiency (56 eyes), spoke-wheel pattern (66/98%), and max-min ET ≥ 14 µm (91/59%); epithelial basement membrane dystrophy (55 eyes), inferior thickening pattern (55/92%), and central ET > 56 µm (53/81%); dry eye (21 eyes), superior thinning pattern (67/88%), and minimal ET ≤ 44 µm (86/48%); pterygium (10 eyes), nasal thickening pattern (100/86%), and nasal ET > 56 µm (80/71%); and in situ carcinoma (11 eyes), max ET > 60 µm (91/60%), and ET SD >5 µm (100/58%). CONCLUSIONS: The epithelial map pattern recognition combined with quantitative analysis of ET is relevant for the diagnosis of OSDs and for distinguishing various OSDs from each other. Deep learning analysis of big data could lead to the fully automated diagnosis of these disorders.

Update on fungal keratitis in France: a case-control study.

PURPOSE: To report an epidemiological update of documented fungal keratitis (FK) in a French tertiary ophthalmological centre from 2014 to 2018 in comparison with a previous period from 1993 to 2008. METHODS: Sixty-two consecutive FK documented by microbiological corneal scrapings were compared with the 64 FK of the previous study. Amphotericin B and voriconazole eye drops were administered hourly. Population characteristics, clinical findings, aetiological organisms and treatments were analysed. RESULTS: The most frequently identified fungi were Fusarium (61%), Aspergillus (6.5%) and Candida (5%). Thirty out of 44 cases examined with in vivo confocal microscopy (IVCM) presented filaments. Ten required conventional cross-linking, 9 therapeutic penetrating keratoplasty, and 2 enucleation. Risk factors significantly associated with the absence of response to medical treatment were patient age (p = 0.01), presence of a deep stromal infiltrate at presentation (p = 0.04) and high numbers of filaments in IVCM images (p = 0.01). The two populations were comparable in age, but not in sex ratio males/females (18/44 versus 37/26 in the previous study; p = 0.001). The frequency of contact lens-associated infection increased from 35.5% to 71% (p = 0.0001) between the two periods. Since then, filamentous FK increased from 69% (44/64) to 95% (59/62) (p = 0.0001). A history of keratoplasty was less frequently reported during the last period (3.2% (2/62) versus 17% (11/64) of cases (p = 0.01)). A clear decrease in the frequency of therapeutic keratoplasty was noted from 39% (25/64) to 14% (9/62) (p = 0.02). CONCLUSION: The frequency of filamentous keratomycosis is currently increasing. Elderly patients and the presence of numerous filaments in IVCM are associated with poor clinical outcomes.

Corneal and Epithelial Thickness Mapping: Comparison of Swept-Source- and Spectral-Domain-Optical Coherence Tomography.

OBJECTIVE: To compare the results and repeatability of the corneal thickness (CT) and epithelial thickness (ET) maps provided by Swept-Source-Optical Coherence Tomography with those of Spectral-Domain-OCT in normal eyes. METHODS: 30 normal eyes of 30 patients were assessed by 3 trained operators with SS-OCT and SD-OCT. RESULTS: The central and minimum ET obtained with both devices were correlated: central ET, r = 0.86, p < 0.05; minimum ET, r = 0.72, p < 0.05. Compared with SD-OCT, SS-OCT tended to underestimate these figures by 1.4 and 1.9 µm on average. The central and minimum CT obtained with both devices were strongly correlated: central CT, r = 0.994, p < 0.05; minimum CT, r = 0.995, p < 0.05. SS-OCT tended to overestimate these figures by 11 and 14 µm on average. Repeatability was good for both devices with a mean coefficient of variation of measurements <6% for ET and <2% for CT. Interoperator variability (standard deviation and COV) was significantly higher for SS-OCT than for SD-OCT for all local epithelial thicknesses and significantly lower for the central CT and several local corneal thicknesses, whereas no significant differences between both technologies were found for the central and minimum ET and the minimum CT. CONCLUSION: SS-OCT and SD-OCT provide reproducible measurements of CT and ET in normal corneas with a strong correlation between both technologies. However, both technologies are not interchangeable when the main thickness parameters (i.e., central and minimum CT and minimum ET) are used for diagnosing early keratoconus or calculating the expected residual stromal bed thickness before corneal refractive surgery or anterior lamellar keratoplasty.

Long-Term Results and Refractive Error After Cataract Surgery With a Scleral Incision in Eyes With Deep Anterior Lamellar Keratoplasty.

PURPOSE: Phacoemulsification in eyes with deep anterior lamellar keratoplasty (DALK) is associated with possible decreased graft survival and difficult IOL power calculation. We assessed cataract surgery in eyes with previous DALK. METHODS: Thirty-three consecutive eyes with DALK and further phacoemulsification with scleral incision were included in this retrospective study. At each postoperative visit, eyes were assessed with manifest refraction, optical coherence tomography, specular corneal topography, and noncontact wide-field specular microscopy. RESULTS: The average postkeratoplasty follow-up time was 102 months [95%-CI, (85-119)]. Cataract surgery was performed on average 43 months (30-56) after DALK. The average postphacoemulsification follow-up time was 58 months [42-74]. All grafts remained clear during follow-up. The best spectacle-corrected logarithm of the minimum angle of resolution visual acuity improved by 2.5 lines [1.8-3.1] on average after cataract surgery from 0.58 (20/77) to 0.34 (20/44) (P < 0.001). The spherical equivalent and intraocular pressure significantly improved from -4.1 D to -1.7 D and from 15.9 to 14.0 mm Hg, respectively. The corneal central thickness was not significantly modified, and the endothelial density decreased by 5.3% from 2081 to 1970 cells/mm2 (P = 0.003). The minimal difference between the achieved and predicted spherical equivalents [-0.05 D, (-2.33; +2.21)] was obtained with the Hoffer Q formula using the IOLMaster axial length and the Orbscan keratometry. CONCLUSIONS: Patients with DALK who underwent phacoemulsification with a scleral incision had a satisfying residual refractive error, very high graft survival, and very few complications. The Hoffer Q formula with the IOLMaster axial length and the specular corneal topography keratometry seems to be the most accurate for IOL calculation.

Multimodal imaging of Hurler syndrome-related keratopathy treated with deep anterior lamellar keratoplasty.

BACKGROUND: Hurler syndrome-associated keratopathy is an exceedingly rare corneal disorder that requires corneal transplantation in advanced stages. Precise assessment of the corneal condition is necessary for deciding which type of keratoplasty (i.e., deep anterior lamellar or penetrating) should be proposed. We aimed to confront the results of multimodal imaging with those of histology in a case of Hurler syndrome-associated keratopathy. CASE PRESENTATION: A 16-year-old patient with Hurler's syndrome treated with hematopoietic stem cell transplantation was referred for decreased vision related to advanced keratopathy. The patient was treated with deep anterior lamellar keratoplasty (DALK) in both eyes with uncomplicated outcome. Visual acuity improved from 0.1 (20/200) preoperatively to 0.32 (20/63) and 0.63 (20/32) after transplantation. The corneal endothelial cell density was 2400 cells/mm2 in both eyes 3 years after transplantation. In vivo confocal microscopy (IVCM) and spectral domain optical coherence tomography (SD-OCT) were performed preoperatively. The corneal buttons retrieved during keratoplasty were processed for histology. In SD-OCT scans, corneal opacities appeared as diffuse stromal hyperreflectivity associated with increased corneal thickness. IVCM showed diffuse cytoplasmic granular hyperreflectivity and rounded/ellipsoid aspects of keratocytes, presence of small intracellular vacuoles, and hyperreflective epithelial intercellular spaces. Bowman's layer was thin and irregular. The corneal endothelium was poorly visualized but no endothelial damage was observed. Histology showed irregular orientation and organization of stromal lamellae, with the presence of macrophages whose cytoplasm appeared clear and granular. A perinuclear clear halo was visible within the epithelial basal cells. Bowman's layer featured breaks and irregularities. CONCLUSIONS: The observed corneal multimodal imaging features in mucopolysaccharidosis-related keratopathy were concordant with histology. Compared with standard histology, multimodal imaging allowed additional keratocyte features to be observed. It revealed both morphological and structural changes of all corneal layers but the endothelium. This information is essential for therapeutic management which should include DALK as the first-choice treatment in case of impaired visual acuity.

Multimodal Imaging Features of Schnyder Corneal Dystrophy.

OBJECTIVE: To describe the multimodal imaging of Schnyder corneal dystrophy. METHODS: Seven eyes of seven patients (5 female and 2 male patients) aged 52 to 92 years were included in this prospective observational study. Diagnosis of SCD was confirmed by histology after keratoplasty. In vivo multimodal imaging consisted of spectral domain-optical coherence tomography with cross sections, en face scans, corneal pachymetry, and epithelial mapping, and in vivo confocal microscopy was recorded. Ex vivo full-field optical coherence tomography scans of two corneal buttons were analyzed. The seven corneal buttons obtained during penetrating or deep anterior lamellar keratoplasty were processed for light microscopy. RESULTS: Slit-lamp examination showed central stromal opacities, arcus lipoides, and midperipheral haze. Corneal crystals were found in 2 out of 7 eyes. SD-OCT cross sections and en face scans showed diffuse hyperreflectivity of the anterior, mid, and posterior stroma with a maximum in the anterior stroma, hyporeflective stromal striae, and epithelial hyperreflectivity. Central corneal thickness ranged from 507 to 635 µm. IVCM revealed hyperreflective deposits in the epithelium and throughout the stroma, thin subepithelial nerves, and needle-shaped and rectangular crystals. Keratocyte nuclei were rare or undetectable. FF-OCT scans confirmed the presence of small round and needle-shaped hyperreflective deposits in the epithelium and stroma. Histology revealed vacuolization of the basal epithelial cells and empty interlamellar stromal vacuoles. CONCLUSION: High-resolution multimodal imaging demonstrates the characteristic features of SCD which involve both the corneal epithelium and stroma, and it provides diagnosis confirmation even in eyes with no visible corneal crystals at slit-lamp examination.

Multimodal imaging of pre-Descemet corneal dystrophy.

PURPOSE: The aim of this study was to assess structural and histological changes associated with pre-Descemet corneal dystrophy with multimodal in vivo imaging. METHODS: Retrospective case series including eight corneas from four unrelated male patients with pre-Descemet corneal dystrophy characterized by the presence of punctiform gray opacities located just anterior to the Descemet membrane at slit-lamp examination of both eyes. In vivo confocal microscopy images were obtained in the central, paracentral, and peripheral corneal zones from the superficial epithelial cell layer down to the corneal endothelium in both eyes. Spectral domain optical coherence tomography scans (central and limbal zones) and mapping of both corneas were acquired. RESULTS: Diffuse small extracellular stromal deposits, presence of enlarged hyperreflective keratocytes in the posterior stroma with either hyperreflective or hyporeflective intracellular dots, and presence of activated keratocytes in the very anterior stroma were observed in all corneas with in vivo confocal microscopy. Spectral domain optical coherence tomography scans showed a hyperreflective line anterior to Descemet's membrane running from limbus to limbus and associated with a second thinner hyperreflective line just beneath Bowman's layer. Fine hyperreflective particles were observed in the posterior, mid, and anterior stroma on optical coherence tomography scans. CONCLUSION: The clinical presentation and structural anomalies found in isolated sporadic pre-Descemet corneal dystrophy are in favor of a degenerative process affecting corneal keratocytes with no epithelial or endothelial involvement. The maximum damage is found just anterior to the Descemet membrane resulting in pre-Descemet membrane location of stromal opacities. Multimodal imaging of cornea reveals that the disorder affects the whole stroma and it permits better understanding of pre-Descemet corneal dystrophy pathophysiology together with ascertained diagnosis.

Influence of graft thickness and regularity on vision recovery after endothelial keratoplasty.

AIM: To assess the influence of graft thickness and regularity on visual recovery and postoperative wavefront aberrations after endothelial keratoplasty (EK). METHODS: 150 EKs performed in eyes with corneal endothelial disorders and no other ocular comorbidities, preoperative and postoperative assessment with spectral domain optical coherence tomography and postoperative assessment with whole eye wavefront aberrometry were retrospectively analysed. Eyes were classified into five groups: Descemet Membrane Endothelial Keratoplasty (DMEK), nanothin Descemet Stripping Automated Endothelial Keratoplasty (DSAEK) (15-49 µm), ultrathin DSAEK (50-99 µm), thin DSAEK (100-149 µm) and conventional DSAEK (150-250 µm). RESULTS: The preoperative diagnosis was Fuchs dystrophy in 139 eyes (92.7%). The graft thickness measured after graft deswelling was in average 74 µm with a mean coefficient of variation of 17%. The average follow-up time was 32 months. The mean spectacle-corrected logarithm of minimum angle of resolution visual acuity improved from 0.76 (20/116) before surgery to 0.14 (20/27) at last follow-up visit. No significant differences in final visual acuity were found between the five groups. The time to reach 20/40 vision was significantly shorter in the DMEK and nanothin DSAEK groups compared with the remaining three DSAEK groups. No significant differences in postoperative aberrometry measurements were found between the five groups. Shorter time to reach 20/40 visual acuity was associated with better preoperative visual acuity and thinner graft. Higher final vision improvement was associated with poorer preoperative visual acuity. Higher postoperative high-order aberrations were associated with poorer preoperative visual acuity. CONCLUSION: The main advantage of DMEK and nanothin DSAEK over thicker DSAEKs was the rapidity of visual recovery. Final quality of vision was not influenced by graft thickness and regularity.

Long-Term Results of Cultured Limbal Stem Cell Versus Limbal Tissue Transplantation in Stage III Limbal Deficiency.

We aimed to evaluate efficiency and safety of transplantation of limbal stem cells (LSC) cultured on human amniotic membrane with no feeders and to compare cultured LSC with limbal tissue transplantation. Thirty eyes with stage III LSC deficiency were treated with autologous (autoLSC) or allogeneic (alloLSC) cultured LSC transplantation (prospective phase II clinical trial; average follow-up time, 72 months) or autologous (autoLT) or allogeneic (alloLT) limbal tissue transplantation (retrospective control group; average follow-up time, 132 months) between 1993 and 2014. The 5-year graft survival defined by absence of recurrence of the clinical signs of limbal deficiency was 71% for autoLSC, 0% for alloLSC, 75% for autoLT, and 33% for alloLT. Visual acuity improved by 9.2 lines for autoLSC and 3.3 lines for autoLT. It decreased by 0.7 lines for alloLSC and 1.9 lines for alloLT. Adverse events were recorded in 1/7 autoLSC, 7/7 alloLSC, 6/8 autoLT, and 8/8 alloLT patients. Corneal epithelial defect was the only adverse event recorded after autoLSC, whereas severe sight-threatening adverse events were recorded in the remaining three groups. Compared with failed grafts, successful grafts featured greater decrease in fluorescein staining, greater superficial vascularization-free corneal area, lower variability of the corneal epithelial thickness, and higher corneal epithelial basal cell density. Autologous cultured LSC transplantation was associated with high long-term survival and dramatic improvement in vision and was very safe. Autologous limbal tissue transplantation resulted in similar efficiency but was less safe. Cadaver allogeneic grafts resulted in low long-term success rate and high prevalence of serious adverse events. Stem Cells Translational Medicine 2019;8:1230&1241.

Contribution of Fourier-domain optical coherence tomography to the diagnosis of keratoconus progression.

PURPOSE: To determine the anatomic criteria for diagnosing keratoconus progression by corneal optical coherence tomography (OCT). SETTING: Quinze-Vingts National Ophthalmology Hospital, Paris, France. DESIGN: Prospective case series. METHODS: Scanning-slit corneal topography (Orbscan II) and Fourier-domain corneal OCT (RTVue) were performed in eyes with mild to moderate keratoconus (progressive or nonprogressive [stable] ectasia) at each examination to assess the keratoconus. Disease progression was defined as an increase of at least 1.0 diopter (D) in the steepest keratometry (K) measurement over 6 months. RESULTS: Of the 134 eyes of 134 patients with mild to moderate keratoconus, 98 had had progressive ectasia and 36 nonprogressive ectasia. The mean maximum K increased significantly in the progressive group (2.1 D ± 1.2 [SD], P < .0001) and remained constant in the stable group (-0.03 ± 0.39 D, P = .31). The mean thinnest corneal thickness increased significantly in the progressive group (-7.98 ± 9.3 µm, P < .0001) and remained constant in the stable group (-0.52 ± 4.21 µm, P = .22). The change in maximum K was significantly correlated with changes in the thinnest corneal thickness (r = -0.61, P < .0001). A cutoff value of -5 µm for the change in thinnest corneal thickness was identified on receiver operating characteristic curves as a threshold separating cases of progressive and stable keratoconus (area under the curve, 0.79; sensitivity, 68%; specificity, 89%). CONCLUSIONS: Topographic data partly reflected the structural changes occurring during the progression of corneal ectasia. Based on the pachymetric parameters provided by OCT, corneal and epithelial thinning was correlated with corneal deformation. The use of corneal OCT might therefore improve the diagnostic sensitivity for keratoconus progression.

Predictive Factors for Successful Type 1 Big Bubble during Deep Anterior Lamellar Keratoplasty.

OBJECTIVE: Big bubble (BB)-deep anterior lamellar keratoplasty (DALK) has become the reference transplantation technique for corneal stromal disorders. Type 1 BB is the desired aspect but it is not constant. We aimed to determine the predictive factors of type 1 BB success. METHODS: Observational cohort study including 77 consecutive eyes of 77 patients undergoing DALK by one surgeon at a single reference center without any selection. Clinical and spectral domain optical coherence tomography data were collected pre- and postoperatively. RESULTS: Stromal scars were found in 91.8% of cases and were located in the anterior (90.9%), mid (67.5%), and posterior (36.4%) stroma. Type 1 BB (49.3% of cases) was significantly associated with the absence of scars in the posterior stroma, stage 1-3 keratoconus, and deep trephination. Among eyes with posterior scars, type 1 BB was associated with higher minimal corneal thickness, maximum-minimum corneal thickness < 220 µm, and diagnosis other than keratoconus. Eyes with type 1 BB featured significantly thinner residual stromal bed (22 ± 8 µm versus 61 ± 28 µm), thinner corneas at 12, 24, and 36 months, and better visual acuity at 12 months compared with eyes with no type 1 BB. Conversely, no significant differences between both groups were observed for graft survival, visual acuity at 24 and 36 months, and endothelial cell density at 12 and 36 months. CONCLUSION: OCT assessment before DALK is useful for choosing trephination depth that should be as deep as possible and for looking for posterior scars. The BB technique may not be the most appropriate method in keratoconus with posterior scars. Follow-up data do not support the need for conversion to penetrating keratoplasty when type 1 BB cannot be obtained nor does it support the need for performing a penetrating keratoplasty as a first-choice procedure in eyes with posterior stromal scars.

Spectral-domain Optical Coherence Tomography in Limbal Stem Cell Deficiency. A Case-Control Study.

PURPOSE: To evaluate the efficacy of optical coherence tomography (OCT) as a noncontact method for imaging the ocular surface in limbal stem cell deficiency (LSCD) and normal eyes. DESIGN: Retrospective case-control study. METHODS: Setting: Institutional. STUDY POPULATION: Twenty-two eyes with LSCD (study group, 22 patients) and 10 normal eyes (control group, 10 patients). OBSERVATION PROCEDURES: Spectral-domain (SD)-OCT and confocal microscopy in both the limbal and central corneal zones. MAIN OUTCOME MEASURES: Pachymetry data from the central cornea, presence of the palisades of Vogt, limbal crypts, and clear transition between the hyporeflective corneal epithelium and the hyperreflective conjunctival epithelium assessed on cross sections parallel and perpendicular to the limbus and en face sections of the limbal region. Parallel, perpendicular, and en face limbal scores were calculated by adding results of the 4 limbal quadrants. RESULTS: Both the difference between the minimal and the maximal epithelial thicknesses and the epithelial thickness standard deviation were significantly higher in the study group (mean, 47 µm/10 µm) compared with the control group (mean, 8 µm/2 µm). The parallel, perpendicular, and en face limbal scores were significantly lower in the study group (0.1/0.6/0.2) compared with the control group (7.4/4.8/3.5). Poorer visual acuity was significantly associated with higher standard deviation and difference between minimal and maximal corneal epithelial thicknesses (rs, +0.81/+0.77) and lower parallel, perpendicular, and en face limbal scores (-0.82/-0.73/-0.82). CONCLUSIONS: SD-OCT of both the central cornea and limbus with various section orientations is a valuable imaging modality allowing noninvasive and rapid overall precise assessment of both normal and LSCD eyes.

Assessment of Confocal Microscopy for the Diagnosis of Polymerase Chain Reaction-Positive Acanthamoeba Keratitis: A Case-Control Study.

PURPOSE: To determine in vivo confocal microscopy diagnostic criteria to diagnose Acanthamoeba keratitis (AK) using polymerase chain reaction (PCR) as the reference diagnostic technique. DESIGN: Retrospective case-control study. Data were recorded prospectively and analyzed retrospectively. PARTICIPANTS: Fifty patients with PCR-positive AK (study group) and 50 patients with bacterial, fungal, viral, or immune keratitis featuring negative Acanthamoeba PCR results (control group). METHODS: In vivo confocal microscopy performed at the acute stage of keratitis. MAIN OUTCOME MEASURES: Presence of in vivo confocal microscopy images suggestive of AK. Multivariate logistic regression was used to determine the relationship between types of images and presence of PCR-positive AK. RESULTS: The following 4 types of images were associated significantly with PCR-positive AK (P < 0.05): bright spots (round or ovoid hyperreflective objects with no double wall; diameter, <30 µm); target images (hyperreflective objects with hyporeflective halo; diameter, <30 µm); clusters of hyperreflective objects (diameter, <30 µm); and trophozoite-like objects (diameter, >30 µm). Specificity of both target and trophozoite images was 100%. This figure was 98.2% for clusters and 48.2% for bright spots. If the diagnosis of AK was made on presence of target images, clusters or trophozoite images (at least 1 of the 3 features), the positive predictive value of confocal microscopy was 87.5% and the negative predictive value was 58.5%. CONCLUSIONS: Acanthamoeba keratitis is a serious vision-threatening disease. In vivo confocal microscopy can help in this challenging diagnosis, especially when PCR is delayed, shows negative results, or is not available. Target images and trophozoite-like images are pathognomonic of AK. Clusters of hyperreflective objects are highly specific of AK. However, the overall sensitivity of in vivo confocal microscopy features of AK is low. In addition to the clinical features, microbiological tests (direct examination and cultures of corneal scrapings), and PCR, in vivo confocal microscopy allows for more rapid diagnosis and treatment initiation, potentially leading to an improved outcome.

Stromal striae: a new insight into corneal physiology and mechanics.

We uncover the significance of a previously unappreciated structural feature in corneal stroma, important to its biomechanics. Vogt striae are a known clinical indicator of keratoconus, and consist of dark, vertical lines crossing the corneal depth. However we detected stromal striae in most corneas, not only keratoconus. We observed striae with multiple imaging modalities in 82% of 118 human corneas, with pathology-specific differences. Striae generally depart from anchor points at Descemet's membrane in the posterior stroma obliquely in a V-shape, whereas in keratoconus, striae depart vertically from posterior toward anterior stroma. Optical coherence tomography shear wave elastography showed discontinuity of rigidity, and second harmonic generation and scanning electron microscopies showed undulation of lamellae at striae locations. Striae visibility decreased beyond physiological pressure and increased beyond physiological hydration. Immunohistology revealed striae to predominantly contain collagen VI, lumican and keratocan. The role of these regions of collagen VI linking sets of lamellae may be to absorb increases in intraocular pressure and external shocks.

New parameters in assessment of human donor corneal stroma.

PURPOSE: To provide quantitative parameters for assessment of human donor corneal stroma by imaging stromal features of diseased and normal human corneas with full-field optical coherence microscopy (FFOCM), using confocal microscopy (CM) and histology as reference techniques. METHODS: Bowman's layer (BL) thickness and keratocyte density were assessed ex vivo in 23 human donor corneas and 27 human pathological corneas (keratoconus and other corneal disorders) with FFOCM, CM and histology. Stromal backscattering was assessed with FFOCM. Additionally, 10 normal human corneas were assessed in vivo with CM. RESULTS: In FFOCM, the logarithm of the normalized stromal reflectivity was a linear function of stromal depth (R2  = 0.95) in human donor corneas. Compared with keratoconus corneas, human donor corneas featured higher BL thickness (p = 0.0014) with lower coefficient of variation (BL-COV; p = 0.0002), and linear logarithmic stromal reflectivity with depth (higher R2 , p = 0.0001). Compared with other corneal disorders, human donor corneas featured lower BL-COV (p = 0.012) and higher R2 (p = 0.0001). Using the 95% confidence limits of the human donor cornea group, BL thickness < 6.5 µm (sensitivity, 57%; specificity, 100%), BL-COV > 18.6% (79%; 100%) and R2  < 0.94 (93%; 71%) were revealed as indictors of abnormal cornea. In CM, keratocyte density decreased with stromal depth (r = -0.56). The mean overall keratocyte density (cells/mm2 ) was 205 in human donor corneas, 244 in keratoconus, 176 in other corneal disorders and 386 in normal corneas. CONCLUSION: Full-field optical coherence microscopy (FFOCM) provides precise and reliable parameters for non-invasive assessment of human donor corneal stroma during storage, enabling detection of stromal disorders that could impair the results of keratoplasty.