Positive cooperativity in synergistic activation of Wnt proteins.

BACKGROUND: Wnt proteins are crucial for embryonic development, stem cell growth, and tissue regeneration. Wnt signaling pathway is activated when Wnt proteins bind to cell membrane receptors. METHODS AND RESULTS: We employed a luciferase reporter assay in HEK293STF cells to measure Wnt protein-induced signaling. We observed that Wnt3a uniquely promotes the Wnt/ß-catenin pathway through positive cooperativity. Additionally, MFH-ND, a molecular mimic of Wnt ligands, markedly increased Wnt3a-induced signaling in a dose-responsive manner. This suggests that various Wnt ligands can synergistically enhance Wnt pathway activation. CONCLUSIONS: The study suggests the likelihood of various Wnt ligands coexisting in a single signalosome on the cell membrane, providing new insights into the complexities of Wnt signaling mechanisms.

Limbal stem cell therapy.

PURPOSE OF REVIEW: To highlight the progress and future direction of limbal stem cell (LSC) therapies for the treatment of limbal stem cell deficiency (LSCD). RECENT FINDINGS: Direct LSC transplantation have demonstrated good long-term outcomes. Cultivated limbal epithelial transplantation (CLET) has been an alternative to treat severe to total LSCD aiming to improve the safety and efficacy of the LSC transplant. A prospective early-stage uncontrolled clinical trial shows the feasibility and safety of CLET manufactured under xenobiotic free conditions. Other cell sources for repopulating of the corneal epithelium such as mesenchymal stem cells (MSCs) and induced pluripotent stem cells are being investigated. The first clinical trials of using MSCs showed short-term results, but long-term efficacy seems to be disappointing. A better understanding of the niche function and regulation of LSC survival and proliferation will lead to the development of medical therapies to rejuvenate the residual LSCs found in a majority of eyes with LSCD in vivo. Prior efforts have been largely focused on improving LSC transplantation. Additional effort should be placed on improving the accuracy of diagnosis and staging of LSCD, and implementing standardized outcome measures which enable comparison of efficacy of different LSCD treatments for different severity of LSCD. The choice of LSCD treatment will be customized based on the severity of LSCD in the future. SUMMARY: New approaches for managing different stages of LSCD are being developed. This concise review summarizes the progresses in LSC therapies for LSCD, underlying mechanisms, limitations, and future areas of development.

Single mRNA detection of Wnt signaling pathway in the human limbus.

Limbal epithelial stem/progenitor cells (LSCs) are adult stem cells located at the limbus, tightly regulated by their close microenvironment. It has been shown that Wnt signaling pathway is crucial for LSCs regulation. Previous differential gene profiling studies confirmed the preferential expression of specific Wnt ligands (WNT2, WNT6, WNT11, WNT16) and Wnt inhibitors (DKK1, SFRP5, WIF1, FRZB) in the limbal region compared to the cornea. Among all frizzled receptors, frizzled7 (Fzd7) was found to be preferentially expressed in the basal limbal epithelium. However, the exact localization of Wnt signaling molecules-producing cells in the limbus remains unknown. The current study aims to evaluate the in situ spatial expression of these 4 Wnt ligands, 4 Wnt inhibitors, and Fzd7. Wnt ligands, DKK1, and Fzd7 expression were scattered within the limbal epithelium, at a higher abundance in the basal layer than the superficial layer. SFRP5 expression was diffuse among the limbal epithelium, whereas WIF1 and FRZB expression was clustered at the basal limbal epithelial layer corresponding to the areas of high levels of Fzd7 expression. Quantitation of the fluorescence intensity showed that all 4 Wnt ligands, 3 Wnt inhibitors (WIF1, DKK1, FRZB), and Fzd7 were highly expressed at the basal layer of the limbus, then in a decreasing gradient toward the superficial layer (P < 0.05). The expression levels of all 4 Wnt ligands, FRZB, and Fzd7 in the basal epithelial layer were higher in the limbus than the central cornea (P < 0.05). All 4 Wnt ligands, 4 Wnt inhibitors, and Fzd7 were also highly expressed in the limbal stroma immediately below the epithelium but not in the corneal stroma (P < 0.05). In addition, Fzd7 had a preferential expression in the superior limbus compared to other limbal quadrants (P < 0.05). Taken together, the unique expression patterns of the Wnt molecules in the limbus suggests the involvement of both paracrine and autocrine effects in LSCs regulation, and a fine balance between Wnt activators and inhibitors to govern LSC fate.

Autologous Serum Eye Drops in the Management of Limbal Stem Cell Deficiency Associated With Glaucoma Surgery.

PURPOSE: To evaluate safety and efficacy of autologous serum eye drops (AS) in the treatment of limbal stem cell deficiency (LSCD) associated with glaucoma surgery. METHODS: Retrospective case series of eyes with glaucoma surgery-induced LSCD treated with AS. Diagnosis of LSCD was confirmed by anterior segment optical coherence tomography, in vivo confocal microscopy, and/or impression cytology. Limbal stem cell deficiency severity was staged using a clinical scoring system (2-10 points). Outcome measures were changes (≥2 points) of the LSCD score and best-corrected visual acuity (BCVA) from the baseline to the last follow-up. RESULTS: Thirteen eyes of 12 consecutive patients treated with 50% AS for at least 3 months were included. The mean age was 78.9±7.5 years and the mean duration of AS use was 20.9±16.8 months. Indications of AS included LSCD progression in eight eyes (61.5%) and visual axis threatening in five eyes (38.5%). The mean LSCD score at baseline (6.7±1.6) was similar to that at last follow-up (6.5±2.2, P =0.625). Two eyes (15.4%) showed improvement, nine eyes (69.2%) were stable, and two eyes (15.4%) worsened. The mean baseline BCVA (0.89±0.64 logMAR) was similar to the mean final BCVA (1.05±0.63 logMAR, P =0.173). There were no serious adverse complications related to AS. CONCLUSION: AS appears to be well tolerated and may stabilize the progression of LSCD with limited effects. A larger study is necessary to confirm the findings.

RETINAL DETACHMENT IN EYES WITH BOSTON TYPE 1 KERATOPROSTHESIS: Surgical Techniques and Mid-Term Outcomes.

PURPOSE: To evaluate the mid-term outcomes of pars plana vitrectomy performed for retinal detachment (RD) repair after Boston Type 1 keratoprosthesis (KPro) implantation. METHODS: Retrospective review of medical records of KPro implanted at the Stein Eye Institute presenting with RD and treated by pars plana vitrectomy. Functional success was defined as a postoperative visual acuity maintained within 2 Snellen lines of the corrected distance visual acuity measured before the development of the RD (baseline) and anatomical success as an attached retina after the pars plana vitrectomy. Kaplan-Meyer survival analyses were performed. RESULTS: Among the 224 KPro performed, 28 (15.2%) RD were identified; of which, 21 (9.4%) were included. The mean follow-up was 42.5 ± 27.3 months. Vitreoretinal proliferation was present in 18 of 21 eyes (85.7%). Surgical techniques were adapted to the complex anterior segment anatomy of KPro eyes. Anatomical success was achieved in 18 of 21 eyes (85.7%). Functional success occurred in 17 of 21 eyes (81.0%), and 5 of 21 eyes (23.8%) reached 20/400 or better visual acuity at the final follow-up. The KPro was retained in 11 in 21 eyes (52.4%). The retention rate decreased from 94.7% at 1 year to 53.5% at 5 years. The most frequent complications were retroprosthetic membrane (47.6%) and corneal melt (23.8%). CONCLUSION: Modified pars plana vitrectomy techniques resulted in relatively good mid-term anatomical, functional, and retention rate outcomes, given the severity of RD at presentation and the numerous preoperative comorbidities of KPro eyes.

Limbal stem cell diseases.

The function of limbal stem/progenitor cells (LSCs) is critical to maintain corneal epithelial homeostasis. Many external insults and intrinsic defects can be deleterious to LSCs and their niche microenvironment, resulting in limbal stem cell dysfunction or deficiency (LSCD). Ocular comorbidities, frequent in eyes with LSCD, can exacerbate the dysfunction of residual LSCs, and limit the survival of transplanted LSCs. Clinical presentation and disease evolution vary among different etiologies of LSCD. New ocular imaging modalities and molecular markers are now available to standardize the diagnosis criteria and stage the severity of the disease. Medical therapies may be sufficient to reverse the disease if residual LSCs are present. A stepwise approach should be followed to optimize the ocular surface, eliminate the causative factors and treat comorbid conditions, before considering surgical interventions. Furthermore, surgical options are selected depending on the severity and laterality of the disease. The standardized diagnostic criteria to stage the disease is necessary to objectively evaluate and compare the efficacy of the emerging customized therapies.

POSTOPERATIVE POSTERIOR SEGMENT COMPLICATIONS AFTER BOSTON TYPE 1 KERATOPROSTHESIS: Incidence, Risk Factors, and Intermediate-Term Outcomes.

PURPOSE: To identify the incidence of, risk factors for, and outcomes of posterior segment complications (PSC) after Boston Type 1 keratoprosthesis (KPro) implantation. METHODS: Retrospective, consecutive case series of KPro procedures at the Stein Eye Institute. Data regarding ocular history, intraoperative details, postoperative management, and outcomes were collected. Eyes with at least one PSC (PSC group) were compared with eyes without PSC (No PSC group), and risk factors for PSC were determined. RESULTS: Ninety-five PSC occurred in 69/169 eyes (40.8%), at a mean of 20.1 months after KPro implantation (0.01 complications/eye month). The median follow-up after KPro implantation was 44.0 months (range 3.0-174.4). The most common PSC were epiretinal membrane (16.6%), cystoid macular edema (12.4%), vitritis (11.2%), and retinal detachment (9.5%). Previous retinal detachment repair, concomitant intraocular lens removal, postoperative aphakia, and vitritis were risk factors for retinal detachment. Postoperative infectious keratitis was a risk factor for epiretinal membrane, cystoid macular edema, and vitritis. The posterior segment complication group had a significantly higher rate of eyes failing to maintain visual acuity ≥20/200 (HR = 2.28; 95% CI = 1.35-3.85) and KPro retention failure rate (HR = 1.66; 95% CI = 0.95-2.91). CONCLUSION: Posterior segment complications occur in approximately 40% of eyes after KPro implantation, resulting in reduced visual outcomes and KPro retention.

CATASTROPHIC ANTIPHOSPHOLIPID SYNDROME AND POSTERIOR OCULAR INVOLVEMENT: Case Series of 11 Patients and Literature Review.

PURPOSE: To describe the posterior ophthalmic manifestations of catastrophic antiphospholipid syndrome. METHODS: Retrospective case series of patients presenting with catastrophic antiphospholipid syndrome and posterior segment ocular manifestations. The main outcomes were the type of posterior segment manifestations at catastrophic antiphospholipid syndrome diagnosis, specifically retinal vascular occlusion, vasculitis, or choroidopathy, and the final best-corrected visual acuity. RESULTS: This study included 23 patients (11 cases treated by the authors and 12 published case reports); 21 (91%) of them female. Their median age at diagnosis was 28 years (range, 16-79 years). Ophthalmologic manifestations were usually bilateral (n = 19, 83%) and involved vascular occlusive retinopathy (n = 17, 74%), choroidopathy (n = 11, 48%), or retinal vasculitis (n = 1, 4%). Final best-corrected visual acuity was not significantly worse than the best-corrected visual acuity at diagnosis (P = 0.16). Retinal vascular occlusions were associated with poorer final visual acuity than choroidopathy (P = 0.002). After a median follow-up of 14 months (range, 2-132 months), nearly half the patients (n = 11, 48%) had permanent vision loss including best-corrected visual acuity of <20/400 for 4 patients. CONCLUSION: Posterior ophthalmic manifestations of catastrophic antiphospholipid syndrome were mainly bilateral retinal vascular occlusion, which had the worst visual prognosis, followed by choroidopathy and retinal vasculitis. Permanent visual loss was common.

Anterior segment optical coherence tomography imaging in peripheral ulcerative keratitis, a corneal structural description.

BACKGROUND: Anterior segment optical coherence tomography (AS OCT) is a helpful tool used to diagnose and manage many corneal conditions, but its use has not been reported in case of peripheral ulcerative keratitis (PUK). The aim of this study is to describe AS OCT findings in cases of PUK. METHODS: Retrospective observational case series of six eyes presenting with a PUK and proven systemic vasculitis. Clinical course, slit lamp photographs, and AS OCT findings were the main outcomes. RESULTS: The AS OCT findings were found to correlate with the ocular disease's level of activity. In the acute stage, an absence of corneal epithelium, a scrambled appearance of the anterior stroma and a heterogeneous stromal reflectivity were observed. During the reduction of disease level activity, an irregular hyporeflective epithelium, a smoother anterior stroma, and a homogenous hyperreflective stroma were seen. At the healed stage, a filling of the corneal defect by a hyporeflective thick epithelium, the persistence of the hyperreflective underlying stroma, and a demarcation line were observed. The mean total corneal thickness at last follow-up was significantly thicker (509 ± 147 µm) compared with the mean corneal thickness at onset (408 ± 131 µm; P = 0.03). CONCLUSIONS: AS OCT provides an assessment of structural changes occurring in PUK, useful for its diagnosis and monitoring.

Hyperreflective pyramidal structures on optical coherence tomography in geographic atrophy areas.

PURPOSE: We observed hyperreflective dome-shaped or pyramidal structures (HPS) on spectral domain optical coherence tomography (SD-OCT) in patients affected with geographic atrophy (GA). Our purpose was to describe the multimodal imaging features of HPS identified in areas of GA in patients with age-related macular degeneration. METHODS: This is a retrospective case series of patients with GA harboring HPS in atrophic areas. Multimodal imaging examination including infrared reflectance, fundus autofluorescence, and SD-OCT, was performed for each patient. Infrared and fundus autofluorescence appearance and mean SD-OCT height of HPS in GA were analyzed. RESULTS: A total of 36 eyes of 25 patients (20 women; mean age, 82.3 ± 5.9 years, range, 73-92 years) with GA were included. A total of 96 HPS in GA were analyzed by SD-OCT. In all HPS (96/96, 100%), the peripheral part was hyperreflective. In 66 of 96 HPS (69%), the center was heterogeneously hyperreflective, whereas in 30 of 96 HPS (31%), the center was hyporeflective. On infrared reflectance images, HPS in GA appeared as hyporeflective lesions surrounded by hyperreflective halos, within an area of background hyperreflectivity because of GA in all eyes. On fundus autofluorescence, 39 of 96 HPS (41%) were heterogeneously hyperautofluorescent, whereas 57 of 96 HPS (59%) were hypoautofluorescent. Mean height of HPS was 91 ± 50.9 µm in the foveal scan (range, 42-291 µm). CONCLUSION: We describe a multimodal imaging of distinctive lesions that presented as hyperreflective pyramidal structures on SD-OCT. We suggest the name "ghost drusen" because these HPS appear in GA areas, and because of their pyramidal or dome-shaped aspect on SD-OCT.

Aftereffects of visuomanual prism adaptation in auditory modality: Review and perspectives.

Visuomanual prism adaptation (PA), which consists of pointing to visual targets while wearing prisms that shift the visual field, is one of the oldest experimental paradigms used to investigate sensorimotor plasticity. Since the 2000's, a growing scientific interest emerged for the expansion of PA to cognitive functions in several sensory modalities. The present work focused on the aftereffects of PA within the auditory modality. Recent studies showed changes in mental representation of auditory frequencies and a shift of divided auditory attention following PA. Moreover, one study demonstrated benefits of PA in a patient suffering from tinnitus. According to these results, we tried to shed light on the following question: How could this be possible to modulate audition by inducing sensorimotor plasticity with glasses? Based on the literature, we suggest a bottom-up attentional mechanism involving cerebellar, parietal, and temporal structures to explain crossmodal aftereffects of PA. This review opens promising new avenues of research about aftereffects of PA in audition and its implication in the therapeutic field of auditory troubles.

Three-Dimensional Reconstruction of Subbasal Nerve Density in Eyes With Limbal Stem Cell Deficiency: A Pilot Study.

PURPOSE: Corneal subbasal nerve parameters have been previously reported using two-dimensional scans of in vivo laser scanning confocal microscopy (IVCM) in eyes with limbal stem cell deficiency (LSCD). This study aims to develop and validate a method to better quantify corneal subbasal nerve parameters and changes from reconstructed three-dimensional (3D) images. METHODS: IVCM volume scans from 73 eyes with various degrees of LSCD (mild/moderate/severe) confirmed by multimodal anterior segment imaging including IVCM and 20 control subjects were included. Using ImageJ, the scans were manually aligned and compiled to generate a 3D reconstruction. Using filament-tracing semiautomated software (Imaris), subbasal nerve density (SND), corneal nerve fiber length, long nerves (>200 µm), and branch points were quantified and correlated with other biomarkers of LSCD. RESULTS: 3D SND decreased in eyes with LSCD when compared with control subjects. The decrease was significant for moderate and severe LSCD (P < 0.01). 3D SND was reduced by 3.7% in mild LSCD, 32.4% in moderate LSCD, and 96.5% in severe LSCD. The number of long nerves and points of branching correlated with the severity of LSCD (P < 0.0001) and with declining SND (R2 = 0.66 and 0.67, respectively). When compared with two-dimensional scans, 3D reconstructions yielded significant increases of SND and branch points in all conditions except severe LSCD. 3D analysis showed a 46% increase in long nerves only in mild LSCD (P < 0.01). CONCLUSIONS: This proof-of-concept study validates the use of 3D reconstruction to better characterize the corneal subbasal nerve in eyes with LSCD. In the future, this concept could be used with machine learning to automate the measurements.

Comparison of Automated and Manual Measurement of Corneal Epithelial Thickness in Eyes With Limbal Stem Cell Deficiency.

PURPOSE: The purpose of this study was to compare the outcomes of manual and automated corneal epithelial thickness (CET) assessments using anterior segment optical coherence tomography in eyes with limbal stem cell deficiency (LSCD). METHODS: Eighty-seven eyes from 64 patients with LSCD and 65 eyes from 39 healthy subjects were included in this cross-sectional study. OCT images of corneas were acquired using a Fourier-domain anterior segment optical coherence tomography. The automated measurement of CET was obtained using the manufacturer's program and the manual measurements were obtained by 2 masked observers. The average CET was obtained from 3 consecutive epithelial profile maps. The average CET of manual measurement was obtained from 3 consecutive cross-line scans using 3-point measurement as previously described. RESULTS: The central CET was thinner in patients with LSCD compared with healthy individuals by both manual and automated measurements. Automated CET measurements were similar to the manually obtained CET in the healthy controls (r = 0.911). However, there is a lower correlation between the automated and manually obtained CET in the LSCD group (r = 0.497). Manual measurements of CET (39.8 ± 11 µm) in eyes with LSCD were significantly lower than the automated measurements (48.8 ± 7.2 µm, P = 0.001, 95% CI -11.0 to -6.9). The correlations between the automated and manually obtained measurements in the mild, moderate, and severe stages of LSCD were 0.623, 0.632, and 0.378, respectively. CONCLUSIONS: There is a large discrepancy between the manual and automated measurements in eyes with LSCD but not in normal eyes. Automated measurements in LSCD exhibited a higher rate of errors and nonuniform measurements due to the presence of subepithelial scars. Automated CET measurements appear to be unreliable in eyes with corneal scars in LSCD.

Vertical prism adaptation, but not sound presentation, modulates the visuospatial representation: A manual line-bisection study.

The present study aimed at testing whether vertical prism adaptation (PA) can modulate vertical visuospatial representation, assessed with a vertical manual line-bisection (MLB) task (Experiment 1). In a second time, we wanted to investigate the potential influence of sound presentation during such a task. Sound is a spatially valued element that has previously been reported to modify horizontal visuospatial representation. In Experiment 2, we presented either a high pitch, a low pitch, or no sound during the same MLB as in Experiment 1. With this experiment, we also searched for an eventual interaction between the effect of sound presentation and the potential cognitive aftereffects of vertical PA on visual representation. Both Experiments 1 and 2 were constructed with the same design and conducted with two distinct groups of young healthy right-handed participants. First, we assessed the initial sensorimotor state with an open-loop pointing task, and the initial representational state through a vertical MLB (with addition of sound for Experiment 2). Then participants were submitted to a 16-minute PA procedure and were tested again on the open-loop pointing task and the MLB to assess the aftereffects following prism removal. Our results showed sensorimotor aftereffects following both upward and downward PA, in a direction opposed to the optical deviation used. The early aftereffects measured following PA were symmetrical, but at the end of the experiment the residual aftereffects were smaller following downward PA than upward PA. We also provide a new insight on the aftereffects of vertical PA on visuospatial representation, showing that downward PA (but not upward PA) can produce an upward bias on the manual line-bisection task. This is the first proof of such cognitive aftereffects following vertical PA. However, we found no effect of sound presentation on the vertical visual space representation and no interaction between PA and sound presentation.

Co-existence of Neurotrophic Keratopathy in Eyes With Limbal Stem Cell Deficiency.

PURPOSE: To investigate whether neurotrophic keratopathy is present in limbal stem cell deficiency (LSCD), by measuring corneal sensation and characterizing corneal subbasal nerve plexus. DESIGN: Prospective, cross-sectional, case-control comparative study. METHODS: A total of 46 eyes with LSCD and 14 normal eyes were recruited from 2019 to 2022. Corneal sensation was measured using a Cochet-Bonnet esthesiometer, and subbasal nerve plexus was imaged using in vivo confocal microscopy (IVCM) at the central cornea and 4 limbal regions. Subbasal nerve density (SND, number of nerves/mm2), subbasal nerve length (SNL, total length of nerves/mm2) and subbasal nerve branch density (SNBD, number of branches/mm2) were quantified. LSCD was graded to stage 1, 2, and 3 using a previously established staging method consisting of clinical scores, basal cell density, central corneal epithelial thickness, and SNL. RESULTS: The mean (±SD) cornea sensation in the central cornea and limbus were 29.2 ± 21.5 and 33.6 ± 15.1 mm in the LSCD group and 57.6 ± 5.8 and 54.3 ± 4.7 mm in the control group, respectively (all P < .001). In sectoral LSCD, the corneal sensation in the affected regions (29.1 ± 17.6 mm) decreased significantly compared to the unaffected regions (41.4 ± 18.2 mm, P < .001). Central corneal SND, SNL, and SNBD were reduced by 84.6%, 82.6%, and 89.2%, respectively, in LSCD compared to controls (all P < 0.05). The central corneal sensation negatively correlated with the severity of LSCD (rho = -0.64, P < .0001) and positively correlated with SND, SNL, and SNBD (rho = 0.63, 0.66, and 0.56, respectively; all P < .001). CONCLUSIONS: Corneal sensation was reduced in eyes with LSCD. The degree of corneal sensation reduction positively correlated with the severity of LSCD. This finding demonstrated the coexistence of neurotropic keratopathy in LSCD.

Descemet Stripping Endothelial Keratoplasty in Patients With a Custom Foldable Silicone Artificial Iris: Safety and Efficacy Outcomes.

PURPOSE: To assess outcomes of Descemet stripping endothelial keratoplasty (DSEK) in eyes with custom artificial iris (CAI) implantation. METHODS: This is a retrospective, interventional, consecutive, surgical case series of patients who underwent DSEK after CAI implantation between 2010 and 2021 at 2 referral centers. Primary safety measures were loss of corrected distance visual acuity (CDVA), increase in intraocular pressure (IOP), development or progression of glaucoma, and intraoperative and postoperative complications. Efficacy measures were graft survival at year 1 and improvement in cosmesis at postoperative month 3. In general, measures were compared between baseline and postoperative year 1 while any complication was reported for the full follow-up period. RESULTS: Thirty-nine eyes of 39 patients were identified. 64.1% of eyes had acquired aniridia from trauma. The mean follow-up interval was 27.7 months (range 12.2-117.4). Median CDVA improved from logMAR 1.0 to 0.7 at year 1 (P = 0.0047). At the final follow-up, permanent loss of CDVA occurred in 25.6% of eyes, of which 90% was due to glaucoma. The most common postoperative complication was IOP elevation (66.7% of eyes). Graft survival at postoperative year 1 was 82.0% (95% confidence interval, 66.3-91.4). Secondary graft failure occurred in 28.2% of eyes at a mean duration of 39.7 months (SD 27.9 months) after DSEK. Cosmesis improved among 87.2% of eyes at postoperative month 3. CONCLUSIONS: DSEK is an effective procedure for addressing corneal edema in eyes with a CAI, but a majority develop elevated IOP and graft survival is shorter than in eyes without a CAI.

Infectious Crystalline Keratopathy Secondary to Mycobacterium chelonae.

PURPOSE: The aim of this study was to describe the clinical presentation and multimodal imaging of a patient diagnosed with infectious crystalline keratitis (ICK) secondary to Mycobacterium chelonae . METHODS: This is a case report of a patient with a crystalline corneal infiltrate imaged with anterior segment optical coherence tomography and in vivo scanning laser confocal microscopy. Bacterial, fungal, acanthamoeba, and acid-fast cultures were performed to identify the causal pathogen. RESULTS: Examination revealed a white stellate opacity in the midstroma underlying the scalloped border of an area of central corneal stromal thinning, consistent with a diagnosis of ICK. Anterior segment optical coherence tomography demonstrated a hyperreflective diamond-shaped opacity located at a depth of 334 µm, which demonstrated multiple stellate projections on in vivo scanning laser confocal microscopy. The acid-fast culture was positive for Mycobacterium chelonae . CONCLUSIONS: Although ICK is most commonly associated with Streptococcus species, it may be secondary to atypical bacteria including Mycobacterium species, underscoring the importance of diagnostic imaging and collecting corneal cultures to identify the pathogenic organism.