Cannabis and the Cornea

Early Lifetime Substance Use and Development of Visual Impairment: Analysis of the National Survey on Drug Use and Health Data

Purpose

To investigate the association between early lifetime substance use on the development of severe visual acuity impairment or blindness on a national level.

Methods

National Survey of Drug Use and Health data was used to identify cases of substance use before 21* years of age, within the past year, and cases of self-reported blindness or visual impairment. Univariable and multivariable binary logistic regression with time-dependency was performed to evaluate odds of visual impairment influenced by 16 substances separated into three classes: prescription, non-prescription, and illicit drugs. Adjusted variables of interest included gender, marital status, race, level of education, total family income, poverty level, population density, and history of chronic disease.

Results

55,824 total responses were analyzed with 2577 (4.6%) cases of self-reported blindness or significant visual impairment. All early-use substance categories, including prescription, non-prescription, and illegal substances, were significantly associated with self-reported VI (OR 2.068, CI 1.451-2.949, p<0.001; OR 1.352, CI 1.227-1.489, p<0.001); OR 1.211, CI 1.086-1.352, p<0.001), respectively). Non-prescription substances displayed parallel significances amongst all constituents (alcohol, cigarettes, inhalants, and marijuana) (OR=1.227, CI 1.12-1.344, p<0.001; OR 1.363, CI 1.243-1.495, p<0.001; OR 1.418, CI 1.134-1.774; OR 1.388, CI 1.27-1.518, p<0.001, respectively). Univariable and multivariable analysis revealed several significant demographical and clinical adjustors.

Conclusion

Early lifetime use of all three classes of substances is associated with enhanced odds of subsequent visual impairment or blindness. Several readily available and commonly used substances have a greater risk. These findings may help clinicians and public health agencies in mitigation ventures including education, prevention, and rehabilitation efforts.

The role of the PI3K/AKT signalling pathway in the corneal epithelium: recent updates

Phosphatidylinositol 3 kinase (PI3K)/AKT (also called protein kinase B, PKB) signalling regulates various cellular processes, such as apoptosis, cell proliferation, the cell cycle, protein synthesis, glucose metabolism, and telomere activity. Corneal epithelial cells (CECs) are the outermost cells of the cornea; they maintain good optical performance and act as a physical and immune barrier. Various growth factors, including epidermal growth factor receptor (EGFR) ligands, insulin-like growth factor 1 (IGF1), neurokinin 1 (NK-1), and insulin activate the PI3K/AKT signalling pathway by binding their receptors and promote antiapoptotic, anti-inflammatory, proliferative, and migratory functions and wound healing in the corneal epithelium (CE). Reactive oxygen species (ROS) regulate apoptosis and inflammation in CECs in a concentration-dependent manner. Extreme environments induce excess ROS accumulation, inhibit PI3K/AKT, and cause apoptosis and inflammation in CECs. However, at low or moderate levels, ROS activate PI3K/AKT signalling, inhibiting apoptosis and stimulating proliferation of healthy CECs. Diabetes-associated hyperglycaemia directly inhibit PI3K/AKT signalling by increasing ROS and endoplasmic reticulum (ER) stress levels or suppressing the expression of growth factors receptors and cause diabetic keratopathy (DK) in CECs. Similarly, hyperosmolarity and ROS accumulation suppress PI3K/AKT signalling in dry eye disease (DED). However, significant overactivation of the PI3K/AKT signalling pathway, which mediates inflammation in CECs, is observed in both infectious and noninfectious keratitis. Overall, upon activation by growth factors and NK-1, PI3K/AKT signalling promotes the proliferation, migration, and anti-apoptosis of CECs, and these processes can be regulated by ROS in a concentration-dependent manner. Moreover, PI3K/AKT signalling pathway is inhibited in CECs from individuals with DK and DED, but is overactivated by keratitis.