Causes of Cataracts and Why They're so Common

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Published: 07 February 2021

Did you know that cataracts are responsible for half of the world’s blindness (Fred Hollows Foundation 2015)?

What are Cataracts?

cataracts diagram
A cataract is when the lens in the eye becomes cloudy, causing vision impairment.

The human eye is made up of several components used to receive and transmit visual information (Perkins 2020). The lens, which sits behind the iris, plays an important role in focusing light on the retina, a light-sensitive membrane at the back of the eye. The light that hits the retina is turned into electrical signals that are transmitted through the optic nerve to the brain (NEI 2019a; Mayo Clinic 2018).

The lens in a healthy eye should be clear, allowing the retina to receive a clear, sharp image (Mayo Clinic 2018). A cataract is when the lens becomes cloudy, causing vision impairment (Vision Australia 2017).

Cataracts are primarily age-related. In fact, almost every person who is 80 or older has some level of cataract formation (Better Health Channel 2014).

Despite this, it is possible, albeit less common, for people to develop cataracts at a young age, or even be born with them (Vision Australia 2017).

Cataracts may be unilateral (affecting one eye) or bilateral (affecting both eyes) (Healthdirect 2019).

While cataracts are a leading cause of blindness, most people can be successfully treated and regain their vision (Healthdirect 2019).

What Causes Cataracts?

The lenses in the eyes generally become less flexible, thicker and less transparent with age or certain conditions, breaking down their protein structure and forming clumps. These clumps cloud areas of the lens, creating cataracts. The clouding gradually expands and becomes denser (Mayo Clinic 2018; NEI 2019b).

Cataract Statistics in Australia

In Australia, cataract is the second most common cause of bilateral vision impairment and cataract surgery is the most common elective surgical procedure (ACSQHC 2017).

Cataracts are a significant issue for First Nations peoples, being 12 times more likely to affect First Nations peoples than non-First Nations Australians. Furthermore, First Nations peoples wait about 63% longer than non-First Nations Australians to receive cataract surgery (Vision 2020 Australia 2019).

Types of Cataracts

types of cataracts

Cataracts can be categorised depending on their location within the lens:

  • Nuclear sclerotic cataracts develop over time as the nucleus (centre) of the lens hardens and becomes yellow. They are the most common type of cataract and progress gradually. They generally affect focus and in some cases may cause a temporary improvement in close-up vision.
  • Cortical cataracts are less common, affecting the cortex (peripheral outer part) of the lens. Cortical cataracts are fissures that resemble the spokes of a wheel, pointing inwards to the middle of the lens. These fissures cause light to scatter when hitting the retina, often causing issues with glare.
  • Posterior subcapsular cataracts occur on the back surface of the lens, under the lens capsule. They often cause reading issues, light sensitivity, glare and ‘halo’ effects. Posterior subcapsular cataracts generally progress the most quickly and are more likely to affect people with diabetes or those with prolonged corticosteroid use.

(Vision Eye Institute 2017; Turner 2020; Mayo Clinic 2018)

Congenital cataracts may be related to genetics, intrauterine infection, trauma or conditions such as rubella (Mayo Clinic 2018).

Risk Factors for Cataracts

In addition to age, other risk factors include:

  • Family history of cataracts
  • Diabetes
  • Eye injury
  • Unprotected eye exposure to sunlight over a long period of time
  • Long-term smoking
  • Long-term corticosteroid use.

(Vision Australia 2017; Healthdirect 2019)

Symptoms of Cataracts

Someone with cataracts may experience:

  • Blurry, hazy or foggy vision
  • Sensitivity to glare
  • Double vision
  • Distorted vision
  • Colours appearing faded or yellowed
  • ‘Halo’ effects around lights
  • The feeling that they are looking through a curtain or veil
  • Frequent prescription changes for corrective lenses
  • Difficulty reading, driving at night, seeing faces or noticing details.

(Vision Australia n.d.; Healthdirect 2019; Mayo Clinic 2018)

Symptoms may not be noticeable until the cataract has progressed to a more advanced stage (Vision Australia 2017).

Diagnosis of Cataracts

Cataracts can be identified through an eye examination, where a practitioner will assess vision, the appearance of the eye and the retina. The pupils may need to be dilated using eye drops so that the retina can be examined. A slit lamp may be used to magnify the eye so that the location and pattern of the cataract can be determined (Healthdirect 2019; Mayo Clinic 2018).

Other tests such as a CT scan, MRI scan or ultrasound may be used to examine the back of the eye (Healthdirect 2019).

Treatment for Cataracts

cataract surgery
Cataract surgery is straightforward and performed in about 20 minutes, generally only requiring local anesthetic.

Glasses and visual aids such as magnification and lighting modifications may improve vision in the early stages of a cataract, but these are not permanent solutions. Once the cataract progresses, surgical treatment is the only effective long-term option (Vision Australia 2017; Healthdirect 2019).

Cataract surgery is one of the most commonly performed and successful surgical procedures (Vision Australia n.d.). It is straightforward and performed in about 20 minutes, generally only requiring local anesthetic (Fred Hollows Foundation 2015; Healthdirect 2019).

The procedure involves removing the clouded lens and replacing it with a new, artificial one (Healthdirect 2019).

Replacing the affected lens with an artificial one may not only restore vision, but also correct any refractive errors (such as myopia). As a result, some patients may no longer require glasses after the procedure (ACSQHC 2017).

Preventing Cataracts

The risk of cataracts may be reduced by:

  • Wearing a hat and sunglasses outside to protect eyes from the sun
  • Smoking cessation
  • Regular eye examinations
  • Seeking advice from a health professional if vision changes occur.

(Vision 2020 Australia 2018)

The Cataract Clinical Care Standard

The Australia Commission on Safety and Quality in Health Care is currently in the process of finalising a new Cataract Clinical Care Standard. This standard aims to guide the assessment and care of patients over the age of 18 with cataracts in all healthcare settings (ACSQHC 2019a).

According to the draft document released in 2019, the standard comprises the following eight Quality Statements:

Quality Statement 1: Primary care assessment and referral Patients with suspected cataracts undergo an initial assessment for:
  • Visual impairment
  • Vision-related limitations
  • Comorbidities
  • Willingness for surgery.
Based on this information, patients are then referred for surgery consideration if appropriate.
Quality Statement 2: Patient information and shared decision-making Patients are provided information in a form that is appropriate for them to support shared decision-making. They are given the opportunity to discuss their needs and preferences, as well as the potential benefits and consequences of their options.
Quality Statement 3: Access to ophthalmology assessment Patients who have been referred for surgery consideration are prioritised for ophthalmology assessment based on their clinical needs
Quality Statement 4: Indications for cataract surgery Patients are offered surgery when their cataracts are at a stage where:
  • Their vision-related activities are impaired
  • They are experiencing clinically significant visual impairment where there is reduced visual acuity of 6/12 or worse, or disabling glare or contrast sensitivity
Quality Statement 5: Prioritisation for cataract surgery Patients are prioritised for surgery based on:
  • Severity of visual impairment
  • Vision-related activity limitations
  • Possible harms of delayed surgery
  • Comorbidity
  • Likely benefits of surgery
Quality Statement 6: Second-eye surgery When a patient with bilateral cataracts is planning surgery for their first eye, the practitioner should discuss with the patient whether the second eye will be operated on, and if so, when the second procedure will take place.
Quality Statement 7: Preventive eye medicines Patients should receive an intracameral antibiotic injection at the time of surgery. Postoperatively, they receive antibiotics or anti-inflammatory eye drops only if indicated.
Quality Statement 8: Postoperative care Patients should receive appropriate postoperative care until they have recovered to ensure any complications are addressed.

(ACSQHC 2019b)

Note: This information is subject to change when the final version of the standard is released.

Additional Resources


References

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