Changes in Epithelial and Stromal Corneal Stiffness Occur with Age and Obesity

Evaluation of the Effect of Body Mass Index and Waist Circumference on Ocular Health Parameters in Children and Adolescents

Background/Objectives: Childhood obesity is a significant health concern also capable of impacting ocular health. This study evaluates the effects of childhood obesity on corneal morphology, anterior chamber parameters, intraocular pressure (IOP), and corneal endothelial cell morphology. Understanding these relationships may contribute to early diagnosis and management strategies. Methods: This prospective, cross-sectional study was conducted at the Harran University Faculty of Medicine between January and December, 2024. Ninety children aged 7-17 years were included, with only the right eyes being analyzed. The participants were categorized into three groups based on body mass index (BMI) percentiles: normal weight (≤85th percentile), overweight (86-94th percentiles), and obese (≥95th percentile). All participants underwent comprehensive ophthalmological examinations, including IOP measurement with a non-contact tonometer, corneal topography assessment using a Scheimpflug camera, and endothelial cell morphology evaluation via specular microscopy. Results: IOP was significantly higher in the overweight and obese groups (p < 0.001). Central corneal thickness (CCT) also increased significantly in these groups (p < 0.05). Positive correlations were determined between BMI and IOP (r = 0.493, p < 0.001) and CCT (r = 0.345, p < 0.001). Additionally, waist circumference exhibited a strong correlation with BMI (r = 0.905, p < 0.001) and a significant association with IOP (r = 0.463, p < 0.001). No significant differences were observed among the groups in terms of other anterior chamber or endothelial parameters. Conclusions: Childhood obesity is associated with increased IOP and CCT, suggesting potential alterations in corneal biomechanics and ocular physiology. These findings highlight the importance of routine ophthalmological evaluation in obese children to detect early ocular changes and prevent long-term complications.

The Effect of Childhood Obesity on Intraocular Pressure, Corneal Biomechanics, Retinal Nerve Fiber Layer, and Central Macular Thickness

PRCIS

Elevated corneal hysteresis (CH) and resistance factor (CRF) in obese and overweight children imply weight's effect on corneal biomechanics. Increased Goldmann-correlated intraocular pressure (IOPg) in obese children indicates glaucoma risk, emphasizing screening for IOP and retinal changes.

PURPOSE

To evaluate the effect of obesity on corneal biomechanics, retinal nerve fiber layer (RNFL), and central macular thickness (CMT) in children.

PATIENTS AND METHODS

In this prospective, cross-sectional, comparative study, 146 eyes of normal-weight, over-weight, and obese children aged between 6 to 17 years were evaluated. The IOPg, corneal compensated IOP (IOPcc), CH, CRF, and the average retinal nerve fiber layer (RNFL), average cup-to-disk ratio (c/d), and central macular thickness (CMT) were measured by Ocular Response Analyser and Spectral-Domain Optical Coherence Tomography (SD-OCT), respectively.

RESULTS

There was no statistically significant difference regarding age, gender, IOPcc, average RNFL thickness, c/d ratio, and CMT among the groups ( P ≥0.05). The IOPg was significantly higher in obese children compared with normal-weight children, while CH and CRF values were significantly higher in both obese and over-weight children compared with healthy ones ( P <0.05). There was a positive correlation between BMI percentile and IOPg, CH, and CRF values.

CONCLUSION

In our study, higher IOPg, corneal hysteresis, and corneal resistance factor values suggest that obese children could be potential candidates for glaucoma. Therefore, it would be appropriate to screen them for IOP and retinal alterations. Further investigations with larger sample size and longer follow-up are needed to understand the risk of glaucoma in obese children.

Aberrations in Cell Signaling Quantified in Diabetic Murine Globes after Injury

The corneal epithelium is an avascular structure that has a unique wound healing mechanism, which allows for rapid wound closure without compromising vision. This wound healing mechanism is attenuated in diabetic patients, resulting in poor clinical outcomes and recurrent non-healing erosion. We investigated changes in cellular calcium signaling activity during the wound response in murine diabetic tissue using live cell imaging from both ex vivo and in vitro models. The calcium signaling propagation in diabetic cells was significantly decreased and displayed altered patterns compared to non-diabetic controls. Diabetic cells and tissue display distinct expression of the purinergic receptor, P2X7, which mediates the wound healing response. We speculate that alterations in P2X7 expression, interactions with other proteins, and calcium signaling activity significantly impact the wound healing response. This may explain aberrations in the diabetic wound response.

Diabetes mellitus and hearing loss: A review

Diabetes (type 2) and sensorineural hearing loss are common health problems manifested with ageing. While both type 1 and type 2 diabetes have been associated with hearing loss, a causal link has been difficult to establish. Individuals with diabetes have twice the incidence of hearing loss compared to those without diabetes and those with prediabetes have a 30% higher rate of hearing loss. Whether hearing loss is associated with diabetes independent of glycemic control remains to be determined. Hearing loss has its own set of risk factors and shares others with diabetes. This review will summarize the complex relationship between diabetes and sensorineural hearing loss.

Wound healing of the corneal epithelium: a review

The corneal epithelium (CE) forms the outermost layer of the cornea. Despite its thickness of only 50 μm, the CE plays a key role as an initial barrier against any insults to the eye and contributes to the light refraction onto the retina required for clear vision. In the event of an injury, the cornea is equipped with many strategies contributing to competent wound healing, including angiogenic and immune privileges, and mechanotransduction. Various factors, including growth factors, keratin, cytokines, integrins, crystallins, basement membrane, and gap junction proteins are involved in CE wound healing and serve as markers in the healing process. Studies of CE wound healing are advancing rapidly in tandem with the rise of corneal bioengineering, which employs limbal epithelial stem cells as the primary source of cells utilizing various types of biomaterials as substrates.

Pannexin1: Role as a Sensor to Injury Is Attenuated in Pretype 2 Corneal Diabetic Epithelium

Epithelial wound healing is essential to repair the corneal barrier function after injury and requires coordinated epithelial sheet movement over the wounded region. The presence and role of pannexin1 on multilayered epithelial sheet migration was examined in unwounded and wounded corneal epithelium from C57BL/6J (B6) control and diet-induced obese (DiO) mice, a pretype 2 diabetic model. We hypothesize that pannexin1 is dysregulated, and the interaction of two ion-channel proteins (P2X7 and pannexin1) is altered in pretype 2 diabetic tissue. Pannexin1 was found to be present along cell borders in unwounded tissue, and no significant difference was observed between DiO and B6 control. However, an epithelial debridement induced a striking difference in pannexin1 localization. The B6 control epithelium displayed intense staining near the leading edge, which is the region where calcium mobilization was detected, whereas the staining in the DiO corneal epithelium was diffuse and lacked distinct gradation in intensity back from the leading edge. Cells distal to the wound in the DiO tissue were irregular in shape, and the morphology was similar to that of epithelium inhibited with 10Panx, a pannexin1 inhibitor. Pannexin1 inhibition reduced mobilization of calcium between cells near the leading edge, and MATLAB scripts revealed a reduction in cell-cell communication that was also detected in cultured cells. Proximity ligation was performed to determine if P2X7 and pannexin1 interaction was a necessary component of motility and communication. While there was no significant difference in the interaction in unwounded DiO and B6 control corneal epithelium, there was significantly less interaction in the wounded DiO corneas both near the wound and back from the edge. The results demonstrate that pannexin1 contributes to the healing response, and P2X7 and pannexin1 coordination may be a required component of cell-cell communication and an underlying reason for the lack of pathologic tissue migration.

Effective elastic modulus of an intact cornea related to indentation behavior: A comparison between the Hertz model and Johnson-Kendall-Roberts model

In this study, a macro-indentation test on the submillimeter scale was performed to analyze the indentation behavior of an intact cornea under physiological pressures. The Hertz and Johnson-Kendall-Roberts (JKR) models were employed to solve the elastic modulus (E) of the intact cornea. The relevant detailed analysis showed that the JKR model, which accounted for the contribution from the adhesion energy, could be used to obtain the E values that were more than two-folds of those obtained from the Hertz model, which only considered the external force. Compared with the uniaxial tension test in vitro, unlike the elastic Hertz-model, the E values under physiological pressures that were obtained with the JKR model were between the lower and upper limits of corneal material. This phenomenon indicated that the JKR model could be used to obtain reasonably effective E values of an intact cornea under physiological pressures.

Alterations in corneal biomechanics underlie early stages of autoimmune-mediated dry eye disease

Autoimmune-mediated dry eye disease is a pathological feature of multiple disorders including Sjögren's syndrome, lupus and rheumatoid arthritis that has a life-long, detrimental impact on vision and overall quality of life. Although late stage disease outcomes such as epithelial barrier dysfunction, reduced corneal innervation and chronic inflammation have been well characterized in both human patients and mouse models, there is little to no understanding of early pathological processes. Moreover, the mechanisms underlying the loss of cornea homeostasis and disease progression are unknown. Here, we utilize the autoimmune regulatory (Aire)-deficient mouse model of autoimmune-mediated dry eye disease in combination with genome wide transcriptomics, high-resolution imaging and atomic force microscopy to reveal a potential extracellular matrix (ECM)-biomechanical-based mechanism driving cellular and morphological changes at early disease onset. Early disease in the Aire-deficient mouse model is associated with a mild reduction in tear production and moderate immune cell infiltration, allowing for interrogation of cellular, molecular and biomechanical changes largely independent of chronic inflammation. Using these tools, we demonstrate for the first time that the emergence of autoimmune-mediated dry eye disease is associated with an alteration in the biomechanical properties of the cornea. We reveal a dramatic disruption of the synthesis and organization of the extracellular matrix as well as degradation of the epithelial basement membrane during early disease. Notably, we provide evidence that the nerve supply to the cornea is severely reduced at early disease stages and that this is independent of basement membrane destruction or significant immune cell infiltration. Furthermore, diseased corneas display spatial heterogeneity in mechanical, structural and compositional changes, with the limbal compartment often exhibiting the opposite response compared to the central cornea. Despite these differences, however, epithelial hyperplasia is apparent in both compartments, possibly driven by increased activation of IL-1R1 and YAP signaling pathways. Thus, we reveal novel perturbations in corneal biomechanics, matrix organization and cell behavior during the early phase of dry eye that may underlie disease development and progression, presenting new potential targets for therapeutic intervention.

An eye on the dog as the scientist's best friend for translational research in ophthalmology: Focus on the ocular surface

Preclinical animal studies provide valuable opportunities to better understand human diseases and contribute to major advances in medicine. This review provides a comprehensive overview of ocular parameters in humans and selected animals, with a focus on the ocular surface, detailing species differences in ocular surface anatomy, physiology, tear film dynamics and tear film composition. We describe major pitfalls that tremendously limit the translational potential of traditional laboratory animals (i.e., rabbits, mice, and rats) in ophthalmic research, and highlight the benefits of integrating companion dogs with clinical analogues to human diseases into preclinical pharmacology studies. This One Health approach can help accelerate and improve the framework in which ophthalmic research is translated to the human clinic. Studies can be conducted in canine subjects with naturally occurring or noninvasively induced ocular surface disorders (e.g., dry eye disease, conjunctivitis), reviewed herein, and tear fluid can be easily retrieved from canine eyes for various bioanalytical purposes. In this review, we discuss common tear collection methods, including capillary tubes and Schirmer tear strips, and provide guidelines for tear sampling and extraction to improve the reliability of analyte quantification (drugs, proteins, others).