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[In vivo confocal microscopy and optical coherence tomography as innovative tools for the diagnosis of limbal stem cell deficiency (French translation of the article)]

The limbus is the anatomical and functional barrier between corneal and conjunctival epithelia. It is characterized by presence of the limbal stem cell niche which allows corneal homeostasis to be maintained. Limbal stem cell deficiency is characterized by a dual process: insufficient regeneration of corneal epithelium, which cannot therefore assure its function of physiological support, associated with corneal invasion by conjunctival proliferation. Diagnosis is currently made via routine clinical examination, corneal impression cytology and in vivo confocal microscopy (IVCM). Slit lamp examination shows abnormal limbal anatomy, thin and irregular epithelium with late fluorescein staining, and superficial vascularization. With its high resolution, IVCM allows identification of limbal and corneal epithelial changes at a cellular level in en face views, parallel to the corneal surface, but with a restricted viewing field of the corneal surface. It shows a poor transition between the corneal and conjunctival epithelia, associated with a loss of the normal corneal epithelial stratification, low basal cell and sub-basal nerve plexus densities, even with sub-epithelial fibrosis. Optical coherence tomography in central cornea and at the limbus, with scans in different orientations, allows a quick, global and non-invasive analysis of normal eyes and those with limbal stem cell deficiency. It shows a thin limbal epithelium, lacking normal thickening, featuring absence of stromal undulations and limbal crypts in cross-sections and sections parallel to the limbus, lack of visible limbal crypts in en face sections, loss of clear transition between the hyporeflective corneal epithelium and the hyperreflective conjunctival epithelium, and hyperreflective sub-epithelial fibrosis.

[Imaging of corneal dystrophies: Correlations between en face anterior segment OCT and in vivo confocal microscopy]

PURPOSE

To evaluate the usefulness of en face Optical Coherence Tomography (OCT) for evaluation of corneal dystrophies and to describe correlations with in vivo confocal microscopy (IVCM).

PATIENTS AND METHODS

Thirty-two eyes of 16 patients with 4 types of corneal dystrophies (epithelial basement membrane dystrophy, Fuchs dystrophy, Reis-Bücklers corneal dystrophy and Crocodile Shagreen dystrophy) were enrolled in this study. Axial and reconstructed en face scans were acquired using OCT. Images were then correlated to IVCM findings.

RESULTS

En face OCT provided new insights into the structure, size and depth of corneal tissue alterations in various corneal dystrophies. OCT en face images were well correlated with IVCM features. Despite lower resolution than IVCM, en face OCT offers the advantages of being non-invasive and allowing the analysis of larger corneal areas.

CONCLUSION

En face OCT provides useful new information in corneal dystrophies. This imaging technique will probably increase in popularity in the near future for the assessment of various anterior segment diseases.

Reis-Bücklers corneal dystrophy: a reappraisal using in vivo and ex vivo imaging techniques

PURPOSE

To characterize the phenotype of Reis-Bücklers corneal dystrophy (RBCD) using in vivo and ex vivo imaging techniques.

METHODS

Five RBCD patients with penetrating keratoplasty (PK) were enrolled. Before surgery, all patients underwent a complete ophthalmological examination including slitlamp biomicroscopy, in vivo confocal microscopy (IVCM) and anterior segment (AS) optical coherence tomography (OCT). After PK, corneal buttons were examined by light and transmission electron microscopy (TEM). Correlations between in vivo and ex vivo images were analyzed.

RESULTS

In all cases, irregular geographic-like subepithelial gray-white opacities were observed in the central and mid-peripheral cornea. AS-OCT images of the cornea of all patients revealed hyperreflective homogeneous and continuous deposits concentrated at the level of Bowman's layer and anterior stroma. Using IVCM, a highly reflective irregular amorphous material was observed from intermediate epithelial cells to the anterior stroma. Sparse deposits of highly reflective material were also detected in the posterior stroma. TEM showed in all specimens basal epithelial cells containing small vesicles with rod-shaped dense material.

CONCLUSIONS

IVCM and AS-OCT may be a useful adjunct to biomicroscopy for the diagnosis and management of RBCD. The correlations between the different in vivo and ex vivo imaging techniques emphasize the hypothesis of an epithelial origin for RBCD.