An Epithelial Abrasion Model for Studying Corneal Wound Healing

The cornea is critical for vision, accounting for about two-thirds of the refractive power of the eye. Crucial to the role of the cornea in vision is its transparency. However, due to its external position, the cornea is highly susceptible to a wide variety of injuries that can lead to the loss of corneal transparency and eventual blindness. Efficient corneal wound healing in response to these injuries is pivotal for maintaining corneal homeostasis and preservation of corneal transparency and refractive capabilities. In events of compromised corneal wound healing, the cornea becomes vulnerable to infections, ulcerations, and scarring. Given the fundamental importance of corneal wound healing to the preservation of corneal transparency and vision, a better understanding of the normal corneal wound healing process is a prerequisite to understanding impaired corneal wound healing associated with infection and disease. Toward this goal, murine models of corneal wounding have proven useful in furthering our understanding of the corneal wound healing mechanisms operating under normal physiological conditions. Here, a protocol for creating a central corneal epithelial abrasion in mouse using a trephine and a blunt golf club spud is described. In this model, a 2 mm diameter circular trephine, centered over the cornea, is used to demarcate the wound area. The golf club spud is used with care to debride the epithelium and create a circular wound without damaging the corneal epithelial basement membrane. The resulting inflammatory response proceeds as a well-characterized cascade of cellular and molecular events that are critical for efficient wound healing. This simple corneal wound healing model is highly reproducible and well-published and is now being used to evaluate compromised corneal wound healing in the context of disease.

Dissociation between Corneal and Cardiometabolic Changes in Response to a Time-Restricted Feeding of a High Fat Diet

Mice fed a high fat diet (HFD) ab libitum show corneal dysregulation, as evidenced by decreased sensitivity and impaired wound healing. Time-restricted (TR) feeding can effectively mitigate the cardiometabolic effects of an HFD. To determine if TR feeding attenuates HFD-induced corneal dysregulation, this study evaluated 6-week-old C57BL/6 mice fed an ad libitum normal diet (ND), an ad libitum HFD, or a time-restricted (TR) HFD for 10 days. Corneal sensitivity was measured using a Cochet-Bonnet aesthesiometer. A corneal epithelial abrasion wound was created, and wound closure was monitored for 30 h. Neutrophil and platelet recruitment were assessed by immunofluorescence microscopy. TR HFD fed mice gained less weight (p < 0.0001), had less visceral fat (p = 0.015), and had reduced numbers of adipose tissue macrophages and T cells (p < 0.05) compared to ad libitum HFD fed mice. Corneal sensitivity was reduced in ad libitum HFD and TR HFD fed mice compared to ad libitum ND fed mice (p < 0.0001). Following epithelial abrasion, corneal wound closure was delayed (~6 h), and neutrophil and platelet recruitment was dysregulated similarly in ad libitum and TR HFD fed mice. TR HFD feeding appears to mitigate adipose tissue inflammation and adiposity, while the cornea remains sensitive to the pathologic effects of HFD feeding.

Association between diabetes and keratoconus-a systematic review and meta-analysis

PURPOSE

To assess the association between diabetes mellitus and keratoconus.

METHODS

PubMed, Google Scholar, Web of Science, and Scopus databases were searched for literature on the association between diabetes and keratoconus. The last literature search was conducted on April 4, 2021. A secondary form of the literature search was conducted by manually scanning the reference list of retrieved eligible articles. Included studies were cohort, case-control, or cross-sectional study design that used odds ratio or risk ratio to evaluate the relationship between keratoconus and diabetes. Egger's test was used to assess the presence of publication bias. The quality of eligible studies was assessed using the Newcastle-Ottawa Scale.

RESULTS

Nine studies (six case-control and three cohort studies) published between 2000 and 2021 were included. The total number of keratoconus patients and controls were 27,311 and 53,732. respectively. Meta-analysis revealed no significant association between diabetes mellitus and keratoconus; the pooled odds ratio was 0.87 (95% confidence interval: 0.66-1.14; p = 0.314). There was significant heterogeneity (Q (df = 7) = 33.36, p < 0.001;I² = 79.01, p < 0.001). Age of participants (p < 0.0001), study design (p < 0.001), and sample size (p = 0.024) were significant sources of heterogeneity. There was no evidence of publication bias.

CONCLUSION

The current meta-analysis revealed no significant association between diabetes mellitus and keratoconus. Well-designed longitudinal prospective studies are, however, needed to investigate any association between diabetes mellitus and keratoconus.

A Low-Fat/Sucrose Diet Rich in Complex Carbohydrates Reverses High-Fat/Sucrose Diet-Induced Corneal Dysregulation

High-fat/sucrose diet feeding in mice causes loss of corneal nerve function and impairs corneal wound healing. While changing to a diet with a low fat/sugar composition and enrichments in complex carbohydrates mitigates the reduction in nerve function, it remains to be determined if it has an effect on corneal wound healing. In this study, 6-week-old C57BL/6 male mice were fed either a normal diet or a high-fat/sucrose diet for 20 weeks. A third group (diet reversal) was placed on a high-fat/sucrose diet for 10 weeks followed by a normal diet for an additional 10 weeks. A central corneal epithelial abrasion wound was created, and wound closure was monitored. Neutrophil and platelet recruitment was assessed by immunofluorescence microscopy. Mice fed the high-fat/sucrose diet-only had greater adiposity (p < 0.005) than normal diet-only fed mice; diet reversal markedly reduced adiposity. Following corneal abrasion, wound closure was delayed by ~6 h (p ≤ 0.01) and, at 30 h post-wounding, fewer neutrophils reached the wound center and fewer extravascular platelets were present at the limbus (p < 0.05). Diet restored normal wound closure and neutrophil and platelet influx in the injured cornea. These data suggest compositional changes to the diet may be an effective diet-based therapeutic strategy for maintaining or restoring corneal health.

Referral Pattern and Comanagement of Patients With Keratoconus in West Africa: A Survey-Based Study of Optometrists in Ghana and Nigeria

OBJECTIVES

To investigate the referral and management patterns of patients with keratoconus among primary eye care practitioners in Ghana and Nigeria.

METHODS

A questionnaire adapted from previous studies was modified and created using Google Forms. The online survey was distributed to prospective participants using e-mails and other social media platforms. Data were analyzed using the Statistical Product and Service Solutions software (version 25.0; IBM Corp, Armonk, NY; Released 2017).

RESULTS

One hundred and sixty-nine optometrists responded to the survey (61.54% from Nigeria and 38.46% from Ghana). Most (88.6%) practiced without corneal topographers. Most respondents (77.7%, n=136) reported not fitting rigid gas-permeable (RGP) contact lenses in a year and 68% were willing to refer for contact lens fitting to another practitioner. The major barriers to RGP fitting were lack of experience (44.4%, n=72), cost to practice (15.4%, n=25), and other reasons (12.4%), whereas 27.8% (n=45) preferred not to answer. Seventy-six percent of respondents (n=133) were willing to fit RGPs if the respondents received the training to do so. About half of the respondents (53.8%) reported progression of cornea signs as the reason for referral to an ophthalmologist. Half of the respondents (n=51.4%) did not have a cornea surgeon in the area the respondents practiced, and 76.3% reported not comanaging patients at all with ophthalmologists.

CONCLUSION

This study highlights the current standard of care of patients with keratoconus in West Africa. The findings from this study suggest that clinical guidelines and further training of eye care practitioners in West Africa are needed to better manage patients with keratoconus.