Age-related cataract

• Summary
• Background
• Clinical features
• Classification
• Cortical
• Nuclear sclerotic
• Posterior subcapsular
• Diagnosis
• Radiology in Focus
• Clinical Correlates
• Imaging Techniques
• Management
• References
• Author(s)

Summary

A cataract is opacification (clouding) of the normally clear lens of the eye, which can lead to a reduction in vision and eventual blindness if left untreated. Globally, cataracts are the leading cause of preventable blindness. They may be acquired (age-related, traumatic, associated with systemic disease or secondary to primary ocular disease) or congenital. Age-related cataracts are the commonest type. Whilst there is no intervention to prevent the development of cataracts, modern cataract surgery can replace the cloudy lens with a clear intraocular lens to improve vision.

Background

The pathogenesis of age-related cataract is poorly understood, but is thought to involve:

• Hardening and compaction of the central lens material (nuclear sclerosis) as new layers of cortical (outer) fibres proliferate over time
• Changes in the ionic components of the lens
• Chemical and structural changes of lens proteins (crystallins), leading to loss of transparency
• Pigmentation of lens proteins (from yellow to brown)

Clinical features

Opacification of the lens reduces its optical quality, which may produce a variety of visual symptoms:

• Blurred (distance or near) vision
• Glare (difficulty seeing in bright light, haloes or glare around lights)
• Poor night vision and difficulty seeing in dim light
• Increasing myopia (near-sightedness) or change in refractive status (including the “second sight” phenomenon, where vision temporarily improves during early cataract development before it deteriorates)
• Loss of contrast sensitivity
• Loss of ability to differentiate colours

However, different symptoms are predominant in different types of cataracts, as will shortly be discussed.

Classification

Age-related cataracts are divided into 3 main classes based on the location of the opacification (although there can be overlap):

• Cortical
• Nuclear sclerotic
• Posterior subcapsular

Cortical

Cortical cataracts are caused by opacification of the outer lens fibres surrounding the nucleus. The effect on vision varies depending on how close the opacities are to the centre of the visual axis. They may progress over years or months.

Symptoms:

• Glare (main symptom)
• Reduced contrast sensitivity
• Reduced distance and near vision

Nuclear sclerotic

Nuclear sclerotic cataracts involve yellowing and thickening and cloudiness of the nucleus of the lens. They are associated with myopia, and are considered an accelerated form of the normal ageing change to the lens.

Symptoms:

• Blurred vision (distance usually affected more than near vision)
• Increasing myopia (the “second-sight” phenomenon described above, where uncorrected distance vision improves in hypermetropes and uncorrected near vision improves in emmetropes)
• Reduced vision in dim light/at night
• Reduced contrast sensitivity
• Reduced ability to differentiate colours
• Glare
• Monocular diplopia (double vision occurring only in one eye, or only when one eye is open)

Posterior subcapsular

Posterior subcapsular cataracts involve opacification in the most posterior cortical layer, immediately under the lens capsule. These occur in younger patients, tend to progress more quickly than nuclear sclerotic cataracts and are most visually significant. They are associated with steroid use and diabetes.

Symptoms:

• Glare
• Reduction in near vision more than distance vision
• Vision often deteriorates quickly

Anterior subcapsular cataracts are a less common class of age-related cataract, which involve the anterior epithelial cells of the lens.

Diagnosis

Diagnosis of cataracts involves taking a thorough history from the patient and examining:

• Visual acuity, with and without spectacle correction
• Brightness acuity (in patients experiencing glare) – shining a bright light at the patient from the side whilst testing their visual acuity
• The dilated eye, including using a slit-lamp. Look out for loss of the red reflex
• Refraction (as a preoperative test in patients suitable for surgery) to determine the power of the intraocular lens implant

Radiology in Focus

In the management of age-related cataracts, imaging plays a crucial role in both diagnosis and preoperative assessment. While cataracts are primarily diagnosed through clinical examination, radiological imaging can provide valuable insights, particularly in complex cases or when associated ocular conditions are suspected.

Clinical Correlates

• Assessment of Ocular Structures: Imaging can help evaluate the overall health of the eye, including the lens, cornea, and retina. This is particularly important in patients with co-existing conditions such as glaucoma or diabetic retinopathy.
• Preoperative Planning: For patients undergoing cataract surgery, imaging can assist in determining the appropriate intraocular lens (IOL) power and assessing the anatomical features of the eye that may influence surgical outcomes.

Imaging Techniques

Ultrasound Biomicroscopy (UBM):

• Indication: Useful for assessing the anterior segment structures, particularly in cases of dense cataracts where direct visualisation is limited.

Optical Coherence Tomography (OCT):

• OCT can provide high-resolution cross-sectional images of the lens, allowing for detailed visualisation of cataract formation and progression.
• OCT enables quantitative measurement of lens density and opacity, which helps in objectively evaluating cataract severity.
• It can detect subtle changes in lens structure before they become clinically apparent, potentially allowing for earlier diagnosis of cataracts.
• After cataract surgery, OCT can be used to assess the position and alignment of the implanted intraocular lens.

B-scan Ultrasound:

A complication of phaecoemulsification is rupture of the posterior capsule. This can result in retained lens fragments. If these fragments fall into the vitreous cavity, these can be depicted on B-scan ultrasound.

In this case, B-scan ultrasound will show echogenic material in the otherwise anechoic or hypoechoic vitreous. These fragments can be removed using pars plana vitrectomy.

Management

Management of age-related cataract involves surgical removal of the clouded lens and insertion of a clear intraocular lens.

References

1. Salmon, John F., and Jack J. Kanski. Kanski’s Clinical Ophthalmology: A Systematic Approach. Ninth Edition, Elsevier, 2020.
2. Basic Clinical Science Course (BCSC) of the American Academy of Ophthalmology. Section 11. 2006 - 2007.
3. Weisschuh, Nicole, et al. ‘Identification of a Novel CRYBB2 Missense Mutation Causing Congenital Autosomal Dominant Cataract’. Molecular Vision, vol. 18, 2012, pp. 174–80.

Author(s)

Jessica Mendall

Jessica is a final year medical student studying in London. She previously studied preclinical medicine in Oxford, intercalating in Systems Neuroscience and Molecular Pathology. She is particularly interested in Ophthalmology, medical education and clinical research.

Dr Abhiyan Bhandari

Abhiyan is the Co-Founder and Radiology & Imaging Lead of Ophtnotes. He is a doctor who graduated from UCL Medical School in London. He scored in the top 10% of candidates who sat the Duke Elder examination and runs ophthalmology and Duke Elder revision sessions aimed at medical students. He also runs a YouTube channel aimed at medical students, covering topics ranging from study tips, productivity and vlogs of his journey through medical school.

Published: 23/8/22

Last updated: 29/1/25