Comparability of corneal thickness and opacity depth assessed by OCT and UBM

Anterior Segment Optical Coherence Tomography for Superficial Keratectomy

PURPOSE

To report the use of anterior segment optical coherence tomography (AS-OCT) for superficial keratectomy (SK) in anterior corneal opacity.

METHODS

The characteristics of 43 eyes (39 patients) with various lesions responsible for anterior corneal opacity were included in this retrospective non-comparative study. AS-OCT was performed on all eyes before surgery. The thickness of corneal opacity and the underlying healthy stroma were measured. SK was performed on each individual.

RESULTS

Four types of anterior corneal opacity were evaluated, including corneal degeneration (26/43), Reis-Bücklers corneal dystrophy (8/43), alkali burn (1/43) and corneal tumors (8/43). Based on AS-OCT images, all eyes showed abnormal hyper-reflective signals and erosion in the superficial cornea to less than one-third of the normal corneal thickness in the deepest corneal opacity. All 43 eyes underwent an SK procedure. In addition, 1 eye with alkali burns and 7 eyes with corneal tumors were combined with amniotic membrane transplantation. All eyes restored transparency without significant complications.

CONCLUSION

AS-OCT is a valuable method for objective preoperative and noninvasive assessments of anterior corneal opacities and is useful for guiding SK.

Assessment of Changes in Cap and Residual Stromal Thickness Values during a 6-Month Observation after Refractive Lenticule Extraction Small Incision Lenticule Extraction

Background: In this study, the changes in corneal cap and residual stromal thickness (RST) values during a 180-day observation period after refractive lenticule extraction small incision lenticule extraction (ReLEx SMILE) were assessed. Methods: Fifty patients underwent ReLEx SMILE using the VisuMax 500 femtosecond laser, with corneal imaging conducted pre and post procedure via anterior segment optical coherence tomography (AS-OCT). Cap thickness in the center and 1.5 mm from the center in four meridians was measured at various intervals. Results: The results showed a significant decrease in cap thickness 180 days post procedure compared to earlier intervals (p < 0.05). Similarly, RST decreased gradually and significantly post procedure (p < 0.05). Notably, changes in cap thickness within the central 1.5 mm area were more dynamic than RST changes during the 6-month observation period following SMILE. Conclusions: The corneal cap thickness measured with swept-source AS-OCT within the central 1.5 mm area underwent more dynamic changes than the residual stromal thickness during the 6-month observation following SMILE.

Correlation of anterior segment optical coherence tomography and ultrasound biomicroscopy in congenital corneal opacity

PURPOSE

To investigate the correlation between swept-source anterior segment optical coherence tomography (AS-OCT) and ultrasound biomicroscopy (UBM) in congenital corneal opacity (CCO).

METHODS

All children with unilateral or bilateral congenital corneal opacities who underwent examination under anesthesia (EUA) and anterior segment optical coherence tomography (AS-OCT) imaging from January 1, 2022, to December 31, 2022, were included. Main outcome measures were corneal and anterior segment evaluation and correlation of UBM and AS-OCT findings.

RESULTS

A total of 22 eyes of 15 patients were imaged using both technologies. The age at first EUA ranged from 11 days to 4 years. Different phenotypes were classified based on the clinical examination, UBM, and AS-OCT findings. Fourteen eyes were diagnosed with Peters anomaly, congenital corneal staphyloma was observed in 4 eyes, 2 eyes had coloboma, 1 eye had peripheral sclerocornea, and 1 eye was diagnosed with congenital primary aphakia. AS-OCT and UBM findings were closely correlated in 18 of 22 eyes (82%) but AS-OCT failed to provide detailed information in 4 eyes (18%) where UBM revealed more details.

CONCLUSIONS

Although AS-OCT offers valuable preliminary data for initial assessment and counseling, it may not consistently provide precise assessments in all cases. Therefore, UBM should be considered for definitive evaluation.

SeqCorr-EUNet: A sequence correction dual-flow network for segmentation and quantification of anterior segment OCT image

The accurate segmentation of AS-OCT images is a prerequisite for the morphological details analysis of anterior segment structure and the extraction of clinical biological parameters, which play an essential role in the diagnosis, evaluation, and preoperative prognosis management of many ophthalmic diseases. Manually marking the boundaries of the anterior segment tissue is time-consuming and error-prone, with inherent speckle noise, various artifacts, and some low-quality scanned images further increasing the difficulty of the segmentation task. In this work, we propose a novel model called SeqCorr-EUNet with a dual-flow architecture based on convolutional gated recursive sequence correction for semantic segmentation and quantification of AS-OCT images. An EfficientNet encoder is employed to enhance the intra-slice features extraction ability of semantic segmentation flow. The sequence correction flow based on ConvGRU is introduced to extract inter-slice features from consecutive adjacent slices. Spatio-temporal information is fused to correct the morphological details of pre-segmentation results. And the channel attention gate is inserted into the skip-connection between encoder and decoder to enrich the contextual information and suppress the noise of irrelevant regions. Based on the segmentation results of the anterior segment structures, we achieved automatic extraction of essential clinical parameters, 3D reconstruction of the anterior chamber structure, and measurement of anterior chamber volume. The proposed SeqCorr-EUNet has been evaluated on the public AS-OCT dataset. The experimental results show that our method is competitive compared with the existing methods and significantly improves the segmentation and quantification performance of low-quality imaging structures in AS-OCT images.

Development of stromal differentiation patterns in heterotypical models of artificial corneas generated by tissue engineering

Purpose: We carried out a histological characterization analysis of the stromal layer of human heterotypic cornea substitutes generated with extra-corneal cells to determine their putative usefulness in tissue engineering. Methods: Human bioartificial corneas were generated using nanostructured fibrin-agarose biomaterials with corneal stromal cells immersed within. To generate heterotypical corneas, umbilical cord Wharton's jelly stem cells (HWJSC) were cultured on the surface of the stromal substitutes to obtain an epithelial-like layer. These bioartificial corneas were compared with control native human corneas and with orthotypical corneas generated with human corneal epithelial cells on top of the stromal substitute. Both the corneal stroma and the basement membrane were analyzed using histological, histochemical and immunohistochemical methods in samples kept in culture and grafted in vivo for 12 months in the rabbit cornea. Results: Our results showed that the stroma of the bioartificial corneas kept ex vivo showed very low levels of fibrillar and non-fibrillar components of the tissue extracellular matrix. However, in vivo implantation resulted in a significant increase of the contents of collagen, proteoglycans, decorin, keratocan and lumican in the corneal stroma, showing higher levels of maturation and spatial organization of these components. Heterotypical corneas grafted in vivo for 12 months showed significantly higher contents of collagen fibers, proteoglycans and keratocan. When the basement membrane was analyzed, we found that all corneas grafted in vivo showed intense PAS signal and higher contents of nidogen-1, although the levels found in human native corneas was not reached, and a rudimentary basement membrane was observed using transmission electron microscopy. At the epithelial level, HWJSC used to generate an epithelial-like layer in ex vivo corneas were mostly negative for p63, whereas orthotypical corneas and heterotypical corneas grafted in vivo were positive. Conclusion: These results support the possibility of generating bioengineered artificial corneas using non-corneal HWJSC. Although heterotypical corneas were not completely biomimetic to the native human corneas, especially ex vivo, in vivo grafted corneas demonstrated to be highly biocompatible, and the animal cornea became properly differentiated at the stroma and basement membrane compartments. These findings open the door to the future clinical use of these bioartificial corneas.

Bioimaging of Dissolvable Microneedle Arrays: Challenges and Opportunities

The emergence of microneedle arrays (MNAs) as a novel, simple, and minimally invasive administration approach largely addresses the challenges of traditional drug delivery. In particular, the dissolvable MNAs act as a promising, multifarious, and well-controlled platform for micro-nanotransport in medical research and cosmetic formulation applications. The effective delivery mostly depends on the behavior of the MNAs penetrated into the body, and accurate assessment is urgently needed. Advanced imaging technologies offer high sensitivity and resolution visualization of cross-scale, multidimensional, and multiparameter information, which can be used as an important aid for the evaluation and development of new MNAs. The combination of MNA technology and imaging can generate considerable new knowledge in a cost-effective manner with regards to the pharmacokinetics and bioavailability of active substances for the treatment of various diseases. In addition, noninvasive imaging techniques allow rapid, receptive assessment of transdermal penetration and drug deposition in various tissues, which could greatly facilitate the translation of experimental MNAs into clinical application. Relying on the recent promising development of bioimaging, this review is aimed at summarizing the current status, challenges, and future perspective on in vivo assessment of MNA drug delivery by various imaging technologies.