Understanding Cataracts And Their Relationship With Hypertension

Introduction

Cataracts are the most common cause of impaired vision in the world, specifically in older adults. In this progressive condition, the eye's natural lens clouds over. It often distorts one's vision, mostly affecting visibility under poor lighting or bright light sources.¹

Hypertension, or high blood pressure, are among the most common diseases claiming millions of lives every year. It is often called the "silent killer" because it rarely presents noticeable signs and symptoms. It can lead to severe medical complications, which may range from heart diseases to strokes. Current research demonstrates the potential link between hypertension and the possible formation of cataracts. As such, this paper delves into the very nature of cataracts, including the symptoms and risk factors that predispose one to such conditions. The relationship between hypertension and cataract formation is explored in detail as well.²

Cataracts

Cataract, which might be defined as any degree of opacity of the crystalline lens, occurs whenever the refractive index of the lens varies by appreciable amounts over distances about the wavelength of the transmitted light. Such a variation in the refractive index may be due to changes in the lens cell structure, changes in lens protein constituents, or both. 

In most cases, cataracts are associated with loss of the lens microarchitecture. Large fluctuations in optical density cause significant scattering of light. Concentrations of high molecular weight protein aggregates of a dimension on the order of at least 0.1 nm can lead to such light scattering and opacity as well. Short-range, ordered crystalline packing is critical in preventing the crystalline lens, which comprises more than 90% of soluble lens protein, from forming a separate homogeneous phase.³

Cataracts can be present at birth or even appear within the first year of life. This form of cataract is termed congenital or infantile. Another type occurs in the first ten years and is called juvenile cataracts. However, over half of the cases occur after 45 years and are termed senile and age-related. 

The boundaries between different types of cataracts are approximate. For instance, some investigators might classify juvenile cataracts as occurring before 20 years of age and age-related cataracts as occurring after 60 years of age. Subtle cataracts may not be evident for years after they develop, especially if they are asymptomatic. The age at onset of a cataract does not determine its aetiology. 

Hereditary or secondary to a noxious intrauterine event (rubella), cataracts associated with systemic or genetic disease often do not develop until the second or third decade. An example is cataracts associated with retinitis pigmentosa. Even age-related cataracts, typically considered due to multiple insults accumulated over many years, have a genetic component that makes certain individuals more susceptible to environmental insults.³ Its symptoms include blurred vision, difficulty seeing at night, light sensitivity, double vision, etc.⁴

Hypertension

Hypertension is a multifactorial syndrome with various underlying causes. Chronic elevation of blood pressure can lead to serious complications, including stroke, kidney failure, increased morbidity, and death. It is clinically defined as a blood pressure reading greater than 120/80mmHg. Several factors can contribute to the development of hypertension, like diet, a sedentary lifestyle, smoking, chronic stress, etc.⁵

The link between hypertension and cataracts

Hypertension appears to have a complex and multifaceted relationship with the development of cataracts. Key contributing factors include:⁶

Increased oxidative stress

Hypertension involves increased oxidative stress, wherein free radicals accumulate in greater quantities than the available antioxidant reserve. Oxidative stress leads to cell damage of the tissue due to its excessive effects, contributing to lens damage that gives rise to cataracts. 

Vascular changes

High blood pressure can alter ocular blood vessels, altering nutrition and health in the lens. Metabolic changes that lead to the development of cataracts may result from poor blood flow.

Systemic inflammation

Research shows that hypertension is associated with chronic inflammation, which can lead to the progression of cataracts. Inflammatory markers in the body affect the transparency of the lens and increase the chances of cataracts.

Medication impact

Certain medications, such as diuretics and beta-blockers, have been observed to increase the risk of cataract development. However, the association is complex and individual-dependent.

Diagnosis

Cataracts are diagnosed using a comprehensive eye examination offered by an eye care provider. These may include:⁷

• Visual acuity test: The test determines how well you see at various distances
• Dilated eye exam: Eye drops are used to open the pupils in order to get a view of the lens and retina
• Tonometry: It measures the pressure inside the eye

Treatment options

Treatment varies depending on the stage of development. Mild cataracts may not be treated; but for advanced cases, surgery is recommended.

Non-invasive methods

Some non-invasive methods include:⁸

• Glasses: A pair of lenses can help a person view objects when the cataract is still at an incipient stage
• Magnification lenses: These prove helpful for reading and other activities that require close vision

Invasive methods

Cataract surgery has long been considered one of the most popular and effective forms of surgery in the world. The procedure involves:⁹

• Phacoemulsification: This is the most common procedure, where an ultrasonic device breaks up the cloudy lens and then sucks it out. An artificial, intraocular lens is implanted
• Extracapsular cataract extraction: Advanced cataract procedure with a larger incision, making way for the removal of the lens. It is generally an outpatient procedure with a very short recovery time. Most patients see considerable improvements in their vision

FAQs

What are cataracts and how do they blur vision?

Foggy or milky vision, blurry or altered vision, halo rings around lights, whitening and dulling of color perception, are typical symptoms which may severely affect the ability to perform daily activities.

How does high blood pressure contribute to cataract?

High blood pressure may cause damage to the blood vessels in the eye tissue and impair the oxygen supply, which leads to a faster oxidation of the lens, particularly among the elderly.

Is reducing high blood pressure going to contribute to the prevention of cataracts? 

The lowering of high blood pressure may greatly minimize the chances of cataract through substantial reduction of harm to the eyes and improvement in blood vessel functioning in eyes.

What should I do to avoid cataracts?

Regular eye exams, proper diet, exercise, and blood pressure control may play important roles in ensuring one's eye health and retard the progression of the cataract.

Summary

Hypertension has been identified as a risk factor for the development of cataract in various studies. Through clinical observations, it has been noted that the formation of cataract is more prevalent among hypertensive individuals than normotensives. Oxidative stress due to hypertension might expedite the breakdown of proteins in lenses, thus increasing the susceptibility of developing cataracts at a younger age. Moreover, drugs used in the treatment of blood pressure, such as diuretics, have been found to increase the risk for certain types of cataracts, although the benefits of managing blood pressure outweigh such risks.

Therefore, control of hypertension may be an important preventative measure in stopping the onset of cataracts in some people. In addition, other interventions such as lifestyle modification and prescribed drugs can reduce the potential onset of cataracts and maintain overall eye health in patients suffering from hypertension. This can be achieved by ensuring the early diagnosis and treatment of cataracts among those suffering from hypertension.