Am I at risk for cataract?
A cataract is defined as clouding or opacification of an otherwise clear lens of the eye or its surrounding transparent membrane, the capsule. According to Dr. Lawrence Woodard, MD at Omni Eye Services, Atlanta, “The eye is similar to a camera; just as a camera’s lens focuses light onto a film, the eye’s lens focuses light onto the retina.”
Another important function of the lens is its ability to adjust an eye’s focus at all distances by the process of accomodation; this allows us to see things clearly both up close and far away. The opacification of the lens blocks the passage of light making the formation of a clear image on the retina blurred, while hardening of the lens makes accommodation difficult thereby causing numerous visual disturbances.
This disease is progressive and so are the visual symptoms. According to Mr Vincenzo Maurino- a renowned ophthalmologist, “Normally, a cataract starts forming at the age of 50-60 when the lens starts to become a little less transparent and then as the patient ages further, it starts affecting the quality of the vision itself and requires removal.” WHO regards it as the most common preventable cause of blindness worldwide along with uncorrected refractive errors.
Epidemiology of cataract:
According to World Health Organization, (2010) 20 million people go blind because of cataract which represents 51% of all the blind people worldwide. Studies suggest that cataract is responsible for clinical blindness i.e. visual acuity of <3/60 in approximately 570,000 adults in Pakistan.
Symptoms of cataract:
Patients with cataract may present with or more of the following symptoms:
- Blurred vision is usually progressive and painless. It may be unilateral or bilateral.
- Increased sensitivity to glare of bright lights particularly headlights causing difficulty in driving at night.
- Double vision or diplopia is the perception of two images of a single object.
- Halos or rings around light. These halos are mostly rainbow coloured.
- Worsening presbyopia that is a refractive error associated with age.
- Colour vision abnormalities causing yellowing of perceived images.
Pathophysiological basis of cataract:
The lens is composed of fibers enclosed by a thin capsule, and is maintained by zonules on both sides. The lens fibers are made from the lens epithelium and migrate from the margin towards its center. The central part of the lens is called the nucleus and is made up of the oldest fibers, while the newly formed lens fibers are deposited in layers around it, called the cortex. The lens fibres are made up of water and protein, called crystallins. The clarity of lens is dependent on the fine arrangement of the three-dimensional structure of these proteins and their hydration. With increasing age, the metabolic efficiency of lens reduces, thus increasing its predisposition to noxious factors; oxidative stress breaks down the three-dimensional structure of proteins allowing them to aggregate or clump together, along with damage to the cell membranes of lens fibres. This results in clouding or discoloration of lens in that area and scattering of light, noted as an early cataract. The process continues gradually till the whole lens becomes cloudy, making it harder to see.
Based on location of opacification within the lens, cataracts are classified into three types: cortical, nuclear, and posterior sub-capsular opacities. The type of cataract affects the type and severity of patient’s symptoms:
A sub-capsular cataract occurs at the back of the lens and noted in diabetics or in people taking high doses of steroid medications. Such an opacity may not produce any symptoms until it is well-developed.
A nuclear cataract forms deep in the central zone (nucleus) of the lens and are associated with ageing. It affects the brightness of colours as the earliest symptom. As the nuclear cataract develops, it causes an index myopia which results in a temporary improvement in near vision, called the “second sight.”
A cortical cataract is characterised by whitish, wedge-like opacities that start in the periphery of lens and move to the center in a spoke-like fashion, surrounding the central nucleus. These opacities particularly cause symptoms of glare while driving at night.
Some factors, discussed below, may provoke the above mechanisms and a cataract is noticeable at an early age.
Who is at risk?
Experts have identified numerous risk factors and preventable causes of cataract that need to be looked for to ensure an early detection of disease. The risk factors may be divided into those that can be modified and those that cannot.
Non-modifiable risk factors of cataract:
- Advancing age is the most significant risk factor. Individuals in the fifth and sixth decades of life are most prone to developing cataract. A new term has been introduced that represents both presbyopia and senile cataract- Dysfunctional lens syndrome (DLS). Whereas some researchers believe presbyopia is the first stage in the development of age-related cataract.
- Congenital predisposition may be due to maternal infections or hereditary fundus dystrophy.
- Traumatic injury to the eye may accelerate the degenerative changes. This may result from perforating or blunt trauma, electrical burns, radiation exposure or chemical burns.
- Family history of cataract may lead to early disease development.
- History of previous eye surgery may also predispose the patient to the opacification of the lens.
Modifiable risk factors of cataract:
- Smoking is a well-established, preventable cause of cataract as it causes deposition of metal ions in the human lens
- Excessive alcohol consumption increases the risk of developing senile cataract
- Pharmacological agents like corticosteroids and lipid lowering agents have been identified as culprits in lens opacification diseases.
- Poor diabetic control and long-standing diabetes are strongly associated with earlier development of cataract
- Hypertensive patients are more likely to develop degenerative changes in the proteins of the eye due to increased proportion of inflammatory cytokines
- Cataract may present as a complication of uncorrected high myopia
- Prolonged and excessive ultraviolet radiation a.k.a. sun exposure may lead to damage to the lens, accelerating and/or mimicking age-related detrimental changes, hence increasing the chances of developing certain types of cataract
- Nutritional deficiencies have been linked with higher chances of clouding of the lens. Diet rich in fruits and vegetables high in antioxidants (vitamin E and the carotenoids lutein and zeaxanthin) may help prevent certain types of cataracts
- Severe dehydration due to excessive diarrhoea has been associated with the pathogenesis and rapid progression of cataract
- Deficiency of parathyroid hormone frequently presents as cataract and duration of disease is directly proportional to the chances of lens opacification
Treatment of cataract is almost always surgical. A trial of conservative management may, however, be given if visual acuity is more than or equal to 6/24. Commonly performed surgical procedures include:
- Irrigation and aspiration of the lens followed by intraocular lens (IOL) implantation. It is commonly performed in case of congenital cataract. The intraocular comes in the following varieties:
- Monofocal IOL is the prototype and patients with monofocal lens implantation may require corrective glasses after cataract surgery. However, implantation of such intraocular lens may also save the patients from the side effects produced by the multifocal variety.
- Bifocal IOL was not a huge leap of discovery as it produced results similar to that of monofocal. While correction in the affected eye was satisfactory, spectacles may be required for the other eye.
- Trifocal IOL is a more advanced type and has shown promising results especially in those with coexisting hyperopia. Complete independence from glasses is markedly better in those with trifocal intraocular lens implantation as compared to bifocal.
- Multifocal IOL produce noteworthy improvement in near vision and spectacle independence as compared to monofocal IOL, however, side effects such as halos, glare, and photic phenomena have been reported.
- Extracapsular cataract extraction with IOL implantation is regarded as the surgical management of choice in patients with senile cataract.
- In cases with coexisting astigmatism, a toric intraocular lens is preferred over the standard intraocular lens as it decreases the dependency on spectacles post cataract surgery. These may also be of monofocal, multifocal, and sinusoidal trifocal varieties.
Benefits of cataract surgery:
Dr. Jeff Taylor gives hope to all individuals suffering from the disease as he states, “Cataracts are one of the most treatable eye diseases.” Furthermore, Mr Vincenzo Maurino claims, “…removal of the cataract will give most patients 99% perfect vision, with the added benefit of reducing of their dependence on glasses.” The most evident and straight-forward benefit is better vision. Due to the recent technological advancements, intraocular lens (IOL) come in great varieties allowing those with other co-existing conditions like myopia, hyperopia, presbyopia, and astigmatism to see better than before they had cataract as these conditions may also be addressed during cataract surgery. As a result, patients attain complete independence from spectacles given the right type of IOL is employed. Overall, there is marked improvement in quality of life and high levels of patient satisfaction after cataract surgery with a success rate ranging between 70-80% in light of recent studies.
- Alió, J. L., Montalbán, R., Peña-García, P., Soria, F. A., & Vega-Estrada, A. (2013). Visual outcomes of a trifocal aspheric diffractive intraocular lens with microincision cataract surgery. Journal of refractive surgery, 29(11), 756-761. Retrieved from https://www.healio.com/ophthalmology/journals/jrs/2013-11-29-11/%7Ba2d75d80-ffc5-4f91-92ea-8fabd6e61ca8%7D/visual-outcomes-of-a-trifocal-aspheric-diffractive-intraocular-lens-with-microincision-cataract-surgery
- Allen, E., Burton, R., Webber, S., Haaskjold, E., Sandvig, K., Jyrkkiö, H., . . . Wollensak, J. (1996). Comparison of a diffractive bifocal and a monofocal intraocular lens. Journal of Cataract & Refractive Surgery, 22(4), 446-451. Retrieved from https://www.sciencedirect.com/science/article/abs/pii/S088633509680040X
- Athanasiov, P., Casson, R., Sullivan, T., Newland, H., Shein, W., Muecke, J., . . . Aung, T. (2008). Cataract in rural Myanmar: prevalence and risk factors from the Meiktila Eye Study. British journal of ophthalmology, 92(9), 1169-1174. Retrieved from https://bjo.bmj.com/content/92/9/1169.short
- Becker, C., Schneider, C., Aballéa, S., Bailey, C., Bourne, R., Jick, S., & Meier, C. (2018). Cataract in patients with diabetes mellitus—incidence rates in the UK and risk factors. Eye, 32(6), 1028-1035. Retrieved from https://www.nature.com/articles/s41433-017-0003-1
- Bizer, W. F. (2013, January 01). Can you explain the surgery for cataract with astigmatism? Retrieved from https://www.aao.org/eye-health/ask-ophthalmologist-q/cataract-surgery-astigmatism.
- de Silva, S. R., Evans, J. R., Kirthi, V., Ziaei, M., & Leyland, M. (2016). Multifocal versus monofocal intraocular lenses after cataract extraction. Cochrane Database of Systematic Reviews. Retrieved from https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD003169.pub4/abstract
- de Vries, N. E., & Nuijts, R. M. (2013). Multifocal intraocular lenses in cataract surgery: literature review of benefits and side effects. Journal of Cataract & Refractive Surgery, 39(2), 268-278. Retrieved from https://www.sciencedirect.com/science/article/abs/pii/S0886335012016665
- Despas, F., Rousseau, V., Lafaurie, M., De Canecaude, C., Durrieu, G., Bagheri, H., . . . Montastruc, J. L. (2019). Are lipid‐lowering drugs associated with a risk of cataract? A pharmacovigilance study. Fundamental & clinical pharmacology, 33(6), 695-702. Retrieved from https://onlinelibrary.wiley.com/doi/abs/10.1111/fcp.12496
- Fernández, J., Rodríguez-Vallejo, M., Martínez, J., Tauste, A., & Piñero, D. P. (2018). From Presbyopia to Cataracts: A Critical Review on Dysfunctional Lens Syndrome. Journal of ophthalmology. Retrieved from https://www.hindawi.com/journals/joph/2018/4318405/abs/
- Gong, Y., Feng, K., Yan, N., Xu, Y., & Pan, C. W. (2015). Different amounts of alcohol consumption and cataract: a meta-analysis. Optometry and Vision Science, 92(4), 471-479. Retrieved from https://journals.lww.com/optvissci/fulltext/2015/04000/Different_Amounts_of_Alcohol_Consumption_and.13.aspx
- Graw, J. (2004). Congenital hereditary cataracts. International Journal of Developmental Biology, 48(8-9), 1031-1044. Retrieved from http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.462.6413&rep=rep1&type=pdf
- Ikuno, Y. (2017). Overview of the complications of high myopia. Retina, 37(12), 2347-2351. Retrieved from https://journals.lww.com/retinajournal/Abstract/2017/12000/OVERVIEW_OF_THE_COMPLICATIONS_OF_HIGH_MYOPIA.18.aspx
- Jadoon, Z., Shah, S. P., Bourne, R., Dineen, B., Khan, M. A., Gilbert, C. E., & Group, P. N. (2007). Cataract prevalence, cataract surgical coverage and barriers to uptake of cataract surgical services in Pakistan: the Pakistan National Blindness and Visual Impairment Survey. British Journal of Ophthalmology, 91(10), 1269-1273. Retrieved from https://bjo.bmj.com/content/91/10/1269.short
- Jonker, S. M., Bauer, N. J., M. N., Berendschot, T. T., Van den Biggelaar, F. J., & Nuijts, R. M. (2015). Comparison of a trifocal intraocular lens with a+ 3.0 D bifocal IOL: results of a prospective randomized clinical trial. ournal of Cataract & Refractive Surgery, 41(8), 1631-1640. Retrieved from https://www.sciencedirect.com/science/article/abs/pii/S0886335015010020
- Katargina, L., Kruglova, T., Trifonova, O., Egiyan, N., Kogoleva, L., & Arestova, N. (2019). Refraction in pseudophakic eyes after surgical treatment of congenital cataracts. Vestn Oftalmol, 135(1), 36-41. Retrieved from https://europepmc.org/abstract/med/30830072
- Langford-Smith, A., Tilakaratna, V., Lythgoe, P. R., Clark, S. J., Bishop, P. N., & Day, A. J. (2016). Age and smoking related changes in metal ion levels in human lens: implications for cataract formation. PloS one, 11(1). Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4721641/
- Maurino, V. (2018, May 16). An expert’s guide to cataracts. Retrieved from https://www.topdoctors.co.uk/medical-articles/an-expert-s-guide-to-cataracts.
- McGinty, S. J., & Truscott, R. J. (2006). Presbyopia: the first stage of nuclear cataract? Ophthalmic research, 38(3), 137-148. Retrieved from https://www.karger.com/Article/Abstract/90645
- Miyashita, H., Hatsusaka, N., Shibuya, E., Mita, N., Yamazaki, M., Shibata, T., . . . Sasaki, H. (2019). Association between ultraviolet radiation exposure dose and cataract in Han people living in China and Taiwan: A cross-sectional study. PloS one, 14(4). Retrieved from https://journals.plos.org/plosone/article/file?type=printable&id=10.1371/journal.pone.0215338
- Montastruc, G., Despas, F., Rousseau, V., Lafaurie, M., De Canecaude, C., Durrieu, G., . . . Montastruc, J. (2020). Lipid-lowering drugs and the risk of cataract: An Observational Post Marketing Study. . Archives of Cardiovascular Diseases Supplements, 12(1), 190. Retrieved from https://www.sciencedirect.com/science/article/pii/S187864801930936X
- National Eye Institute. (2019, August 3). Cataracts. Retrieved from https://www.nei.nih.gov/learn-about-eye-health/eye-conditions-and-diseases/cataracts.
- Nizami AA, G. A. (2019, December). Cataract StatPearls [Internet]. (Treasure Island (FL): StatPearls Publishing) Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK539699/.
- Saha, S., Gantyala, S. P., Aggarwal, S., Sreenivas, V., Tandon, R., & Goswami, R. (2017). Long-term outcome of cataract surgery in patients with idiopathic hypoparathyroidism and its relationship with their calcemic status. Journal of bone and mineral metabolism, 35(4), 405-411. Retrieved from https://link.springer.com/article/10.1007/s00774-016-0767-6
- Sharma, P., & Gupta, D. (2019). Corticosteroid Induced Cataract In COPD Patient. JK Science, 41(1), 48-49. Retrieved from http://www.jkscience.org/archives/volume211/10-%20Case%20Report.pdf
- Singh, S., Pardhan, S., K. V., Swaminathan, G., Ravichandran, J., Ganesan, S., . . . Raman, R. (2019). The prevalence and risk factors for cataract in rural and urban India. Indian journal of ophthalmology, 67(4), 477. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6446631/
- Taseer, Z., Khan, M. A., A. S., Gillani, S. A., & Sarwar, S. (2019). CATARACT; DIABETES AND SMOKING AS A MAJOR RISK FACTOR FOR CATARACT IN THE COMMUNITY POPULATION OF RESIDENTS OF LAHORE CANTT. Professional Medical Journal, 26(2). Retrieved from http://search.ebscohost.com/login.aspx?direct=true&profile=ehost&scope=site&authtype=crawler&jrnl=10248919&AN=134630419&h=iRwtiWc1RboWH8bOQmMQfLc7JX%2BvH83mbo55GfqOF5nYiQJx2jQy%2BvckPZqyEenRoYQjg8pz%2FPM2J38fCc9HxQ%3D%3D&crl=c
- Taylor, H. R. (1999). Epidemiology of age-related cataract. Eye, 13(3), 445-448. Retrieved from https://www.nature.com/articles/eye1999119
- Taylor, J. (2012, September). Cataract Q&A with Dr. Jeff Taylor. (R. Morrell, Interviewer) Retrieved from https://yoursightmatters.com/cataract-qa-dr-jeff-taylor/
- Verma, S., Nema, N., Verma, A., Dwivedi, S., & Gupta, M. (2018). Risk factors and visual outcome in presenile cataract. Indian Journal of Clinical and Experimental Ophthalmology, 4(4), 450-453. Retrieved from http://www.academia.edu/download/58783348/IJCEO-4-4-450-453.pdf
- Woodard, L. (2018, June). Educating Patients About Cataracts. (CollaborativeEYE, Interviewer) Retrieved from https://collaborativeeye.com/articles/may-june-18/educating-patients-about-cataracts/
- World Health Organization. (2010). Priority eye diseases. WHO facts-sheet. Retrieved from https://www.who.int/blindness/causes/priority/en/index1.html
- World Health Organization. (2019). Blindness and vision impairment. WHO Fact-sheets. Retrieved from https://www.who.int/news-room/fact-sheets/detail/blindness-and-visual-impairment
- Yu, X., Lyu, D., Dong, X., He, J., & Yao, K. (2014). Hypertension and risk of cataract: a meta-analysis. PloS one, 9(12). Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4256215/
- Zainuddin, D., Sasaki, K., Kojima, M., Sakamoto, Y., & Fujisawa, K. (1991). Risk factor analysis in a cataract epidemiological survey in West Sumatra, Indonesia. Distribution of Cataracts in the Population and Influencing Factors, 21, 78-86 . doi:https://doi.org/10.1159/000419939