Cataract- Modifiable and Non-modifiable Risk factors

Experts’ take on cataract:

Simply put- clouding of the otherwise clear lens of the eye or its surrounding transparent membrane (capsule) is regarded as cataract (Nizami AA, 2019). During an interview Lawrence Woodard, MD- Medical Director at Omni Eye Services, Atlanta, explained, “The eye is similar to a camera. Just as a camera’s lens focuses light onto film, the eye’s lens focuses light onto the retina.” (Woodard, 2018). This opacification of the lens blocks the passage of light making the formation of image on the retina difficult and therefore causing visual disturbances. However, this disease is progressive as Mr Vincenzo Maurino-a renowned ophthalmologist from London states, “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.” (Maurino, 2018). WHO regards it as the most common preventable cause of blindness worldwide along with uncorrected refractive errors (World Health Organization, 2019).

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 (Jadoon, et al., 2007).

Symptoms of cataract:

Patients with cataract may present with or more of the following symptoms (Nizami AA, 2019; National Eye Institute, 2019):

• 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.
• 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:

Dr. Jeff Taylor explains, “A cataract is a clouding of the lens of the eye due to changes in proteins that make up the lens. As we age, the lens thickens and hardens.” (Taylor, 2012). Basically, degenerative changes occurring in the lens or its transparent capsule due to any reason may result in cataract. While many causes including congenital, traumatic, substance-abuse, and systemic diseases are identified; age-related damage remains the most common cause of cataract worldwide (Singh, et al., 2019).

Who is at risk?

Experts have identified numerous risk factors and preventable causes of cataract (Nizami AA, 2019). According to Dr. Jeff Taylor, “Once patients reach the age of 50, I suggest an annual comprehensive eye exam.” This is to ensure 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) (Fernández, Rodríguez-Vallejo, Martínez, Tauste, & Piñero, 2018). Whereas some researchers believe presbyopia is the first stage in the development of age-related cataract (McGinty & Truscott, 2006).
• Congenital predisposition may be due to maternal infections or hereditary fundus dystrophy (Nizami AA, 2019; Graw, 2004).
• 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 (Nizami AA, 2019).
• Family history of cataract may lead to early disease development (Verma, Nema, Verma, Dwivedi, & Gupta, 2018).
• History of previous eye surgery may also predispose the patient to the opacification of the lens (National Eye Institute, 2019).

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 (Langford-Smith, et al., 2016; Taseer, Khan, Afzal,, Gillani, & Sarwar, 2019)
• Excessive alcohol consumption increases the risk of developing senile cataract (Gong, Feng, Yan, Xu, & Pan, 2015).
• Certain pharmacological agents like corticosteroids (Sharma & Gupta, 2019) and lipid lowering agents (Despas, et al., 2019; Montastruc, et al., 2020) have been identified as culprits in lens opacification diseases.
• Poor diabetic control and long-standing diabetes are strongly associated with earlier development of cataract (Becker, et al., 2018; Taseer, Khan, Afzal,, Gillani, & Sarwar, 2019).
• Hypertensive patients are more likely to develop degenerative changes in the proteins of the eye due to increased proportion of inflammatory cytokines (Yu, Lyu, Dong, He, & Yao, 2014).
• Cataract may present as a complication of uncorrected high myopia (Ikuno, 2017).
• 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 (Miyashita, et al., 2019).
• Nutritional deficiencies have been linked with higher chances of clouding of the lens (Zainuddin, Sasaki, Kojima, Sakamoto, & Fujisawa, 1991; Athanasiov, et al., 2008)
• Severe dehydration due to excessive diarrhoea has been associated with the pathogenesis and rapid progression of cataract (Taylor H. R., 1999).
• Deficiency of parathyroid hormone frequently presents as cataract and duration of disease is directly proportional to the chances of lens opacification (Saha, et al., 2017).

Treatment options:

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 (Nizami AA, 2019). 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 (Katargina, et al., 2019). 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 (de Silva, Evans, Kirthi, Ziaei, & Leyland, 2016).
• 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 (Allen, et al., 1996)
• Trifocal IOL is a more advanced type and has shown promising results especially in those with coexisting hyperopia (Alió, Montalbán, Peña-García, Soria, & Vega-Estrada, 2013). Complete independence from glasses is markedly better in those with trifocal intraocular lens implantation as compared to bifocal (Jonker, et al., 2015).
• 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 (de Vries & Nuijts, 2013).
• Extracapsular cataract extraction with IOL implantation is regarded as the surgical management of choice in patients with senile cataract (Nizami AA, 2019).
• 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 (Bizer, 2013). 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 (Nizami AA, 2019).