Cataracts are a leading cause of blindness worldwide, contributing to nearly half of all cases. According to the World Health Organization (WHO), cataracts affect approximately 65.2 million people worldwide. Amidst a growing global population of older individuals, this age-related disease has attracted considerable research interest, particularly regarding its underlying causes.
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Cataract research encompasses studies using animals with induced cataracts and human lenses removed from patients. Major focus areas include investigating potential defects in lens protein formation and structure, identifying risk factors, and developing effective disease control strategies.
Investigations into the cause of cataracts have revealed a link between oxygen exposure and cataract formation. Interestingly, some studies suggest that statins, commonly used to lower blood cholesterol, could exert antioxidant effects that counteract the inflammation and oxidative stress implicated in cataract development.
Furthermore, eye drops containing acetyl-carnosine have shown promise in reducing oxidation and glycation damage in the lens by minimizing crystallin cross-linking, potentially contributing to cataract prevention. Additionally, studies indicate that diets rich in the antioxidants lutein and zeaxanthin may lower the risk of developing nuclear cataracts.
The Lens Opacities Classification Scheme (LOCS III), a standardized grading system, categorizes cataracts based on slit lamp images. By comparing these images with standard photographic transparencies, cataracts are classified as nuclear, cortisol, or posterior. Additionally, a severity grade ranging from 1 to 5 is assigned.
The Oxford Clinical Cataract Classification and Grading System (OCCGS) is another slit-lamp-based system that utilizes diagrams and Munsell color samples for cataract grading. Studies have demonstrated the comparability and high reproducibility of both LOCS III and OCCGS. However, the inherent subjectivity of these techniques highlights the need for an objective and reproducible method to standardize cataract grading.
Scheimpflug photography, an innovative imaging technique, represents a significant advancement in cataract research. This anterior eye segment analysis system offers objective and accurate quantification of cataract intensity and type. Its advantage lies in its ability to generate three-dimensional images of the lens by capturing multiple static slit images. This technique produces sixty images at three-degree intervals around a central axis, providing a detailed visualization of the degree of opacity and its precise location within the lens.
Wavefront aberrometry has emerged as another promising technique for evaluating abnormalities in the entire eye and its optical system. Initially employed in corneal refractive surgery, this imaging technique is now undergoing research to explore its clinical applications in cataract management.
New avenues in cataract research
Cataract research has seen significant advancements in recent years, leading to improved surgical techniques, innovative lens technologies, and potential preventive strategies.
Lens refilling
Lens refilling is an innovative approach to cataract treatment that aims to restore the natural lens's clarity by injecting a biocompatible hydrogel into the lens capsule. This technique holds the potential to revolutionize cataract surgery by eliminating the need for artificial lens implantation and preserving the eye's natural accommodation ability.
Traditional cataract surgery involves removing the clouded natural lens and replacing it with an artificial intraocular lens (IOL). While IOLs provide clear vision, they cannot adjust focus for different distances, often requiring glasses for near-vision tasks. Conversely, lens refilling seeks to maintain the natural lens's ability to accommodate, potentially restoring a full range of clear vision without needing glasses.
The lens refilling procedure involves carefully removing the cataract-affected lens material while preserving the lens capsule, a thin, transparent membrane that holds the lens in place. A biocompatible hydrogel, designed to mimic the optical properties of the natural lens, is then injected into the lens capsule, filling the space previously occupied by the cataract.
Extended depth of focus intraocular lenses
Extended depth of focus (EDOF) intraocular lenses represent a significant advancement in cataract surgery technology. They offer patients a wide range of clear vision and reduce dependence on glasses for both near and far distances. These innovative lenses provide a more natural visual experience compared to traditional monofocal IOLs, which only provide clear vision at a single distance.
Gene therapy: A revolutionary approach to combating and preventing cataracts
Gene therapy has emerged as a promising frontier in cataract research, offering the potential to prevent or delay cataract formation by targeting the underlying genetic factors that contribute to the disease. While gene therapy for cataracts is still in its early stages of development, significant progress has been made in recent years.
One promising approach involves delivering viral and non-viral vectors to restore the function of specific genes that play a crucial role in maintaining lens clarity. For instance, researchers are investigating ways to deliver genes that encode proteins involved in lens transparency and antioxidant defense mechanisms. By correcting these genetic defects, gene therapy could potentially prevent or delay cataract formation.
Another research area is focused on developing gene therapy strategies to protect lens cells from oxidative stress, a major contributor to cataract development. Researchers are exploring molecular techniques to introduce genes that encode antioxidant enzymes or other protective proteins. These genes could help neutralize harmful free radicals and protect lens cells from damage, thereby delaying cataract formation.
Gene therapy targets cataract candidate genes suspected to play a role in the development of cataracts. Mutations or alterations in these genes can disrupt normal lens function and increase the risk of cataract formation. Some of the most widely studied cataract candidate genes include:
- The genes CRYAA, CRYAB, and CRYGC encode crystallin proteins and are well-known to maintain lens transparency and prevent protein aggregation. Mutations in these genes can lead to cataract formation.
- The gene major intrinsic protein (MIP) encodes a protein that regulates water transport in the lens (aquaporin 0, also known as AQP0). Mutations in the MIP gene have been reported to be associated with congenital cataracts.
Original Sources
- http://www.biomedcentral.com/content/pdf/1471-2415-11-32.pdf
- http://www.auckland.ac.nz/
- https://www.rpbusa.org/rpb/
- http://www.nhs.uk/conditions/cataracts-age-related/Pages/Introduction.aspx
- http://www.nei.nih.gov/health/cataract/webcataract.pdf
- http://www.nccah-ccnsa.ca/docs/nccah%20partner%20documents/vision_cataracts_web.pdf
- https://www.aoa.org/
- https://www.who.int/
References
- Bai, Chao, et al. "A novel missense mutation in the gene encoding major intrinsic protein (MIP) in a Giant panda with unilateral cataract formation." BMC genomics 22.1 (2021): 1-10. https://pubmed.ncbi.nlm.nih.gov/33530927/
- Constable, Ian Jeffery, et al. "Gene therapy for age-related macular degeneration." The Asia-Pacific Journal of Ophthalmology 5.4 (2016): 300-303. https://www.sciencedirect.com/science/article/pii/S2162098923003183
- Gillespie, Rachel L., et al. "Personalized diagnosis and management of congenital cataract by next-generation sequencing." Ophthalmology 121.11 (2014): 2124-2137. https://pubmed.ncbi.nlm.nih.gov/25148791/
- Karahan, Mine, et al. "Crystalline gene mutations in Turkish children with congenital cataracts." International Ophthalmology 41 (2021): 2847-2852. https://pubmed.ncbi.nlm.nih.gov/33864186/
- Liu, Jing, Yi Dong, and Yan Wang. "Efficacy and safety of extended depth of focus intraocular lenses in cataract surgery: a systematic review and meta-analysis." BMC ophthalmology 19 (2019): 1-10. https://pubmed.ncbi.nlm.nih.gov/31477053/
- Nibourg, Lisanne M., et al. "Nanofiber-based hydrogels with extracellular matrix-based synthetic peptides for the prevention of capsular opacification." Experimental eye research 143 (2016): 60-67. https://www.sciencedirect.com/science/article/abs/pii/S0014483515300403
- Yuan, Lamei, et al. "Identification of a novel GJA3 mutation in congenital nuclear cataract." Optometry and Vision Science 92.3 (2015): 337-342. https://pubmed.ncbi.nlm.nih.gov/25635993/
- Zhang, Wen-Wen, and Zheng-Gao Xie. "Advances in the Study of Lens Refilling." Journal of Ophthalmology 2020 (2020). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7471792/#:~:text=Although%20lens%20refilling%20has%20made,and%20clarity%20of%20the%20capsule.
Further Reading
AI offers hope for enhanced cataract surgery in developing nations