Macular corneal dystrophy: in vivo confocal and structural data

Macular corneal dystrophy with iridofundal coloboma in the same patient: a unique combination

A young a presented with painless, progressive diminution of vision in both eyes (BE). Slit lamp examination revealed the presence of a single central corneal opacity in the right eye and multiple corneal opacities of varying sizes in the left eye (LE), limited to the anterior-mid corneal stroma. Microcornea with reduced central corneal thickness and complete inferonasal iris coloboma along with inferior fundal coloboma, sparing both the disc and macula, were noted in BE. A diagnosis of BE macular corneal dystrophy (MCD) and iridofundal coloboma (IFC) was made. The patient underwent LE sutureless anterior lamellar therapeutic keratoplasty. On histopathological examination, the excised corneal tissue revealed stromal lamellar disarray with positive colloidal iron staining, strongly suggestive of MCD. Whole-exome sequencing revealed the presence of a likely pathogenic carbohydrate sulfotransferase 6 (CHST6) mutation, confirming the diagnosis of MCD. This concurrent presence of IFC with a corneal stromal dystrophy is previously unreported in the literature, to the best of our knowledge.

The role of corneal endothelium in macular corneal dystrophy development and recurrence

Macular corneal dystrophy (MCD) is a progressive, bilateral stromal dystrophic disease that arises from mutations in carbohydrate sulfotransferase 6 (CHST6). Corneal transplantation is the ultimate therapeutic solution for MCD patients. Unfortunately, postoperative recurrence remains a significant challenge. We conducted a retrospective review of a clinical cohort comprising 102 MCD patients with 124 eyes that underwent either penetrating keratoplasty (PKP) or deep anterior lamellar keratoplasty (DALK). Our results revealed that the recurrence rate was nearly three times higher in the DALK group (39.13%, 9/23 eyes) compared with the PKP group (10.89%, 11/101 eyes), suggesting that surgical replacement of the corneal endothelium for treating MCD is advisable to prevent postoperative recurrence. Our experimental data confirmed the robust mRNA and protein expression of CHST6 in human corneal endothelium and the rodent homolog CHST5 in mouse endothelium. Selective knockdown of wild-type Chst5 in mouse corneal endothelium (ACsiChst5), but not in the corneal stroma, induced experimental MCD with similar extracellular matrix synthesis impairments and corneal thinning as observed in MCD patients. Mice carrying Chst5 point mutation also recapitulated clinical phenotypes of MCD, along with corneal endothelial abnormalities. Intracameral injection of wild-type Chst5 rescued the corneal impairments in ACsiChst5 mice and retarded the disease progression in Chst5 mutant mice. Overall, our study provides new mechanistic insights and therapeutic approaches for MCD treatment by high-lighting the role of corneal endothelium in MCD development.

Detailed corneal and genetic characteristics of a pediatric patient with macular corneal dystrophy - case report

BACKGROUND

Corneal dystrophies are a group of rare, inherited disorders that are usually bilateral, symmetric, slowly progressive, and not related to environmental or systemic factors. The majority of publications present the advanced form of the disease with a typical clinical demonstration. The initial signs and symptoms of different epithelial and stromal corneal dystrophies are not specific; therefore, it is very important to establish the early characteristic corneal features of these disorders that could guide the diagnostic process.

CASE PRESENTATION

The main purpose of this study was to report the differential diagnosis of a pediatric patient with bilateral anterior corneal involvement suspected of corneal dystrophy. An 8-year-old male patient presented with asymptomatic, persistent, superficial, bilateral, diffuse, anterior corneal opacities. Slit lamp examination results were not specific. Despite the lack of visible stromal involvement on the slit lamp examination, corneal analysis based on confocal microscopy and optical coherence tomography revealed characteristic features of macular corneal dystrophy (MCD). The diagnosis of MCD was confirmed by CHST6 gene sequencing. The early corneal characteristic features of MCD, established based on the findings of this case report, include corneal astigmatism (not specific), diffuse corneal thinning without a pattern of corneal ectasia (specific), and characteristic features on confocal microscopy (specific), including multiple, dark, oriented striae at different corneal depths.

CONCLUSIONS

The clinical examination should be complemented with corneal imaging techniques, such as confocal microscopy and optical coherence tomography. In patients suspected of corneal dystrophy, genetic testing plays an important role in establishing the final diagnosis.

Macular Corneal Dystrophy: An Updated Review

Macular Corneal Dystrophy is an autosomal recessive form of corneal dystrophy due to a mutation in CHST6 gene, which results in abnormal proteoglycan synthesis. There is accumulation of abnormal glycosaminoglycans in the corneal stroma and endothelium. The deposition results in progressive loss of corneal transparency and visual acuity. The histopathology shows characteristic alcian blue positive deposits. Management in the cases with visual loss requires keratoplasty either full thickness or lamellar. The decision about the ideal type of keratoplasty depends on age and pre-operative clinical features. Although prognosis after keratoplasty is good, recurrences can occur. Future research should be targeted towards gene therapy in this condition.

Bilateral phototherapeutic keratectomy for corneal macular dystrophy in an adolescent: case report and review of the literature

PURPOSE

Phototherapeutic keratectomy (PTK) with 193-nm excimer laser is a safe and effective procedure for the treatment of superficial corneal pathology. We aimed to review the use of PTK for the treatment of corneal macular dystrophy (MCD).

METHODS

Case report and literature review.

RESULTS

A 16-year-old boy presented to an ophthalmologist with a 4-year history of reduced vision, glare and photophobia in his left eye. He was diagnosed with corneal macular dystrophy and underwent sequencing of the CHST6 gene. Left excimer PTK with mitomycin C was performed. He remained relapse free until 18 months post procedure when his visual acuity declined and the stroma appeared more "milky". He underwent a penetrating keratoplasty in his left eye 24 month following the initial PTK.

CONCLUSION

Phototherapeutic keratectomy is an effective means of visual restoration in patients with macular corneal dystrophy and may delay penetrating keratoplasty. Patients should be counselled regarding the high risk of recurrence. This is the first reported case of a CHST6 gene positive patient with MCD that was treated with phototherapeutic keratoplasty.

Characterization of In Vivo Biomechanical Properties in Macular Corneal Dystrophy

PURPOSE

To measure and compare corneal biomechanics in patients with macular corneal dystrophy (MCD), versus those who underwent penetrating keratoplasty (PK) for MCD, versus normal subjects.

DESIGN

Cross-sectional study.

METHODS

This study enrolled 24 eyes with MCD, 25 eyes that underwent PK in patients with preoperative diagnosis of MCD, and 28 normal eyes. The ocular response analyzer was used to measure corneal biomechanical properties, including corneal resistance factor (CRF) and corneal hysteresis (CH). Intraocular pressure (IOP) was measured using a Goldmann applanation tonometer, and central corneal thickness (CCT) was measured using an ultrasonic pachymeter. The CCT, CRF, CH, and IOP were compared among the study group.

RESULTS

CCT was significantly lower in the MCD group (423 ± 47 mμ) than in the PK group (541 ± 31 mμ; P < .001) and the controls (540 ± 26 mμ; P < .001). Meanwhile, CCT was comparable between the PK and control groups (P = .98). CRF did not differ between the MCD (8.34 ± 2.12 mm Hg) and the PK (8.66 ± 1.66 mm Hg) groups (P = .89); however, both of these groups had lower CRF values than the control (9.76 ± 1.83 mm Hg, P = .02) group. No significant differences were observed among the 3 groups in CH (P = .13). IOP values did not differ between the MCD (11.25 ± 1.69 mm Hg) and PK (12.0 ± 2.67 mm Hg) groups (P = .95); however, the IOP values for both of these groups differed significantly from those of the controls (13.46 ± 2.17 mm Hg; P = .006).

CONCLUSIONS

CRF was significantly reduced in MCD and did not return to normal values even after PK. The reduced corneal rigidity could result in underestimating IOP in patients with MCD and in those undergoing PK for this stromal dystrophy.

Structural, ultrastructural, and morphometric study of the zebrafish ocular surface: a model for human corneal diseases?

PURPOSE

A morphological and morphometric study of the adult zebrafish ocular surface was performed to provide a comprehensive description of its parts and to evaluate its similarity to the human.

MATERIALS AND METHODS

The eyes of adult zebrafish were processed for light, transmission and scanning electron microscopy, and for immunohistochemical stain of corneal nerves; a morphometric analysis was also performed on several morphological parameters.

RESULTS

The corneal epithelium was formed by five layers of cells. No Bowman's layer could be demonstrated. The stroma consisted of lamellae of different thickness with few keratocytes. The Descemet's membrane was absent as the flat and polygonal endothelial cells directly adhered to the deepest corneal lamella. The immunohistochemical stain of neurofilaments failed to demonstrate corneal nerve fibers. The conjunctival epithelium was stratified, overlying the stroma formed by a subepithelial and a deep layer, this latter connected to the scleral cartilage. In the peripheral cornea and in the conjunctiva, many goblet and rodlet cells were observed. The morphometric analysis showed that the peripheral cornea epithelium was thicker when compared to the other parts of the ocular surface, with smaller superficial cells. Desmosomes and hemidesmosomes in the conjunctiva were significantly fewer in number than the other parts of the ocular surface. The stroma was thinner in the conjunctiva than in the cornea, while corneal lamellae were thicker in the intermediate stroma.

CONCLUSIONS

The zebrafish ocular surface showed significant differences compared to the human, such as the absence of Bowman's layer, Descemet's membrane and corneal nerve fibers, the reduced stromal thickness, and the presence of rodlet cells. On the basis of these original findings, it is suggested that the use of the zebrafish as a model for studying normal or pathological human corneas should be undertaken with particular caution.

Cytoarchitecture of epithelial inflammatory infiltration indicates the aetiology of infectious keratitis

PURPOSE

To analyse cytological features of corneal epithelium in infectious keratitis.

METHODS

One hundred and eighteen patients (53 males and 65 females) diagnosed with acute stage of infectious keratitis (45 viral, 40 bacterial, 23 fungal, 10 Acanthamoeba keratitis) were included in study. We performed retrospective analysis of bright and blue-light slit-lamp photographs and in vivo corneal confocal microscopy scans of the corneal epithelium from five corneal regions (superior, inferior, temporal, nasal and central). Density, morphology of inflammatory cells and their relation to epithelial structures, as well as density of nerve fibres, were evaluated in relation to the keratitis aetiology.

RESULTS

We characterized five morphological types of inflammatory cells forming infiltration. Cell and nerve fibre densities showed significant differences between groups, and the most intense inflammatory infiltration was associated with fungal then bacterial, viral and Acanthamoeba keratitis. Additionally, differences in aetiology-specific ratio of round/non-round inflammatory cells were observed.

CONCLUSION

Confocal microscopy analysis in infectious keratitis of various aetiologies revealed quantitative and qualitative differences in inflammatory cell infiltration expressed in different ratio of round/non-round inflammatory cells. In vivo microscopic analysis of both the corneal epithelial layer cytopathology and the cytology of inflammatory infiltration provides a fast and specific differentiation of keratitis aetiology that may increase the accuracy in the selection of the initial treatment.

In vivo Confocal Microscopic Analysis of Limbal Stroma in Patients With Limbal Stem Cell Deficiency

PURPOSE

Using in vivo confocal microscopy, we established that unique hyperreflective structures in the anterior limbal stroma of healthy individuals represent the limbal stromal niche. The aim of this study was to characterize the limbal stromal microarchitecture in patients with limbal stem cell deficiency (LSCD).

METHODS

After obtaining informed consent, 10 patients with LSCD and 3 with macular corneal dystrophy were recruited. In vivo confocal imaging of the limbus and cornea of the affected and normal eyes was performed using an HRT III laser scanning microscope, beyond the epithelium deep into the stroma.

RESULTS

In the case of LSCD, the limbal epithelium was replaced by conjunctival epithelium. A large number of inflammatory and dendritic cells were identified along with blood vessels from the epithelium to deep stromal layers. The unique hyperreflective niche structures were replaced by homogenously bright fibrous structures in all eyes with total LSCD. In patients with partial LSCD, even the clinically defined normal limbus had fibrotic stroma. In a patient with focal LSCD, only the affected limbal stroma remained fibrotic, whereas the adjacent clinically normal limbus had the unique hyperreflective structures. Although the opaque corneal stroma appeared bright because of proteoglycan deposition, it was possible to identify the normal limbal epithelial and stromal architecture in macular corneal dystrophy.

CONCLUSIONS

In the case of LSCD, the limbal stromal niche was replaced by bright fibrotic structures indicating persistence of damage several months after injury. Further studies are required to characterize the sequential events occurring in the anterior limbal stroma after injury using this noninvasive method.

In vivo confocal microscopic corneal images in health and disease with an emphasis on extracting features and visual signatures for corneal diseases: a review study

There is an evolution in the demands of modern ophthalmology from descriptive findings to assessment of cellular-level changes by using in vivo confocal microscopy. Confocal microscopy, by producing greyscale images, enables a microstructural insight into the in vivo cornea in both health and disease, including epithelial changes, stromal degenerative or dystrophic diseases, endothelial pathologies and corneal deposits and infections. Ophthalmologists use acquired confocal corneal images to identify health and disease states and then to diagnose which type of disease is affecting the cornea. This paper presents the main features of the healthy confocal corneal layers and reviews the most common corneal diseases. It identifies the visual signatures of each disease in the affected layer and extracts the main features of this disease in terms of intensity, certain regular shapes with both their size and diffusion, and some specific region of interest. These features will lead towards the development of a complete automatic corneal diagnostic system that predicts abnormalities in the confocal corneal data sets.

Protective effects of trehalose on the corneal epithelial cells

PURPOSE

Aim of the present work was to evaluate the effects of the trehalose on the corneal epithelium undergoing alcohol delamination.

METHODS

Twelve patients undergoing laser subepithelial keratomileusis (LASEK) were consecutively included in the study. The right eyes were pretreated with 3% trehalose eye drops, whilst left eyes were used as control. Epithelial specimens were processed for cells vitality assessment, apoptosis, and light and transmission electron microscopy; a morphometric analysis was performed in both groups.

RESULTS

In both trehalose-untreated eyes (TUE) and trehalose-treated eyes (TTE), the percentage of vital cells was similar and no apoptotic cells were observed. In TUE, the corneal epithelium showed superficial cells with reduced microfolds, wing cells with vesicles and dilated intercellular spaces, and dark basal cells with vesicles and wide clefts. In TTE, superficial and wing cells were better preserved, and basal cells were generally clear with intracytoplasmatic vesicles. The morphometric analysis showed statistically significant differences between the two groups: the TTE epithelial height was higher, the basal cells showed larger area and clearer cytoplasm. The distribution of desmosomes and hemidesmosomes was significantly different between the groups.

CONCLUSIONS

Trehalose administration better preserved morphological and morphometric features of alcohol-treated corneal epithelium, when compared to controls.