Types of Cataracts: A Clinical Overview

Not all cataracts are the same. The type of lens opacity, where it forms in the lens, what caused it, and how quickly it progresses, influences the symptoms a patient experiences, the timing of the decision to operate, and the technical approach used in surgery. This overview covers the main cataract classifications used in clinical practice, from common age-related types to rarer entities including traumatic, congenital, and hypermature cataracts.

How Cataracts Are Classified

Cataracts are classified by their location within the lens, their morphology, and their aetiology. The most widely used clinical grading system is the Lens Opacities Classification System III (LOCS III), which grades nuclear opalescence, nuclear colour, cortical opacity, and posterior subcapsular opacity on standardised photographic scales. Location-based classification, nuclear, cortical, or posterior subcapsular, is the most practical framework for understanding how different cataract types affect vision and surgical planning.

The natural lens is a biconvex structure divided into an outer capsule, a cortex, and a central nucleus. Opacities can form in any of these layers, each producing a distinct clinical picture. Mixed cataracts, with features of more than one type, are common, particularly in older patients with longstanding lens changes. Age-related (senile) cataracts are by far the most prevalent category; secondary cataracts arise from systemic disease, medication use, trauma, or radiation exposure.

Nuclear Cataracts

Nuclear cataracts affect the central lens nucleus and are the most common cataract type in clinical practice. They develop gradually with ageing, producing progressive yellowing and hardening of the nucleus that causes reduced distance vision, increased glare, and faded colour perception. A characteristic early feature is nuclear myopic shift, where the lens becomes more convergent as it hardens, temporarily improving near vision without glasses (sometimes called "second sight") before overall vision deteriorates.

Nuclear sclerosis is graded from NS1 (mild yellowing, minimal visual impact) to NS4 or NS5 (dense brown or black brunescent nucleus with severe visual impairment). The degree of nuclear sclerosis influences surgical technique: harder nuclei require more phacoemulsification energy to emulsify and fragment, increasing the risk of endothelial cell loss. Very dense brunescent nuclei may require modified cracking techniques and more instrument manipulation.

Risk factors for nuclear cataract include advancing age, cumulative ultraviolet light exposure, cigarette smoking, and female sex. Onset is typically in the sixth decade or later. Progression is usually gradual over years, though it can accelerate in patients with systemic conditions including diabetes mellitus.

Cortical Cataracts

Cortical cataracts form in the outer lens cortex as spoke-like or wedge-shaped opacities that radiate from the lens periphery toward the centre. Early cortical changes may be detected on slit-lamp examination before patients notice significant visual symptoms; as opacities approach the visual axis, glare, particularly from oncoming headlights, and reduced contrast sensitivity become the dominant complaints.

Cortical cataracts are associated with diabetes mellitus, ultraviolet light exposure, and certain systemic medications. They may progress more rapidly than nuclear cataracts and can be present in younger patients with systemic risk factors. At surgery, the cortical material must be thoroughly aspirated from the capsular bag after removal of the nucleus; residual cortical material increases post-operative inflammation and raises the risk of posterior capsule opacification.

Posterior Subcapsular Cataracts

Posterior subcapsular cataracts (PSC) develop at the back surface of the lens, immediately in front of the posterior capsule. Because they sit directly in the visual axis, PSC produce disproportionately pronounced symptoms relative to their size on slit-lamp examination, particularly difficulty with near vision and severe glare and halos in bright light and with oncoming headlights. PSC can progress more rapidly than nuclear or cortical cataracts and may cause functional impairment in younger patients.

PSC is associated with corticosteroid use (both systemic and inhaled), posterior uveitis, retinitis pigmentosa, and prior ionising radiation to the head or neck. In patients on long-term systemic corticosteroids for inflammatory conditions, lens examination should be part of regular ophthalmological monitoring. Inhaled corticosteroids at high doses have also been associated with posterior subcapsular opacity in observational studies, though the absolute risk is lower than with systemic agents.

Surgically, PSC presents a particular challenge because the posterior capsule, which must remain intact to support the IOL, lies immediately behind the opacity. The posterior capsule in eyes with PSC may be more adherent to the opacity, requiring careful technique during cortex removal.

Traumatic Cataracts

Traumatic cataracts result from blunt or penetrating ocular injury and may present acutely or develop over months to years following the initial trauma. Blunt trauma produces characteristic concussion rosette opacities at the posterior lens pole, caused by disruption of lens fibre organisation at the moment of impact. Penetrating trauma that breaches the lens capsule leads to rapid cortical hydration and pronounced opacification within hours to days. Electrical injury can cause anterior subcapsular vacuoles and stellate opacities.

The surgical management of traumatic cataracts differs from age-related cataracts in several respects. Trauma may compromise the zonular fibres that suspend the lens, creating lens instability that increases the risk of intraoperative complications and may require the use of capsular tension rings or alternative IOL fixation strategies. The eye may also have other traumatic injuries, such as corneal scarring, vitreous disturbance, or retinal pathology, that require assessment and management alongside or before cataract surgery. IOL power calculation in eyes with prior corneal trauma may be less predictable due to altered corneal curvature.

Congenital and Paediatric Cataracts

Congenital cataracts are present at birth or develop in the first year of life and require early treatment to prevent deprivation amblyopia, a permanent reduction in visual acuity from the visual cortex failing to develop normally during the critical period of visual development. Early surgery and optical rehabilitation (contact lenses or glasses, with patching of the fellow eye to drive amblyopia treatment) are the priorities; the timing of surgery and the decision whether to implant an IOL at the time of cataract removal depend on the child's age.

Paediatric cataracts may be isolated or associated with systemic conditions including galactosaemia, Down syndrome, Lowe syndrome (oculocerebrorenal syndrome), and maternal infections during pregnancy (particularly rubella and toxoplasmosis). A systematic evaluation for associated conditions is part of the assessment. Management of paediatric cataracts requires subspecialty paediatric ophthalmology expertise and differs substantially from adult cataract surgery in technique, IOL selection, and long-term follow-up requirements.

Morgagnian and Hypermature Cataracts

A Morgagnian cataract is an advanced form of hypermature cataract in which the lens cortex has liquefied completely, leaving the dense brown nucleus suspended within the capsular bag in a pool of liquid cortex. The lens takes on a milky white appearance and the nucleus may be visible as a brown sphere that sinks inferiorly under gravity when the eye is tilted. Morgagnian cataracts are more commonly encountered in populations with limited access to timely cataract surgery.

These cataracts present particular surgical challenges. The liquefied cortex is under pressure within the capsular bag; if the anterior capsule is opened carelessly, the sudden change in pressure can cause the hard nucleus to surge forward and prolapse through the incision. Special techniques, including controlled decompression of the liquid cortex and a modified capsulorhexis approach, are used to manage this risk. The dense nucleus typically requires significant phacoemulsification energy to remove, and the capsular bag may be weakened by prolonged distension. Pre-operative uveitis from lens protein leakage is a recognised complication of hypermature cataracts and requires treatment before surgery.

Referral Considerations for GPs and Optometrists

Referral for cataract surgery is indicated when lens opacification is causing functional visual impairment that affects daily activities, including driving, reading, or occupational tasks. Visual acuity alone is a poor guide to surgical timing; a patient with 6/12 acuity and severe glare may be more functionally impaired than one with 6/18 acuity and minimal symptoms. The patient's own account of functional difficulty should drive the referral decision.

For referral information for GPs and optometrists, including what to include in a referral letter and how quickly patients are seen, see the Northern Eye Consultants referrer page. Useful information to include in any cataract referral: best-corrected visual acuity in each eye, lens opacity type and density if visible, current refractive correction, relevant ocular history, and a list of all current medications, particularly alpha-blockers and anticoagulants.

For a detailed explanation of the surgical technique used to remove cataracts, see Phacoemulsification: How Modern Cataract Surgery Works. For a guide to intraocular lens options, including monofocal, toric, EDOF, and multifocal lenses, see the companion article on this site. For patients still considering whether their symptoms warrant assessment, see our guide on how to know if you need cataract surgery. For a clinical discussion of complex cataract types and their surgical management, see Dr MacIntyre's article on complex cataract surgery in Melbourne.

References

1. Chylack LT Jr, Wolfe JK, Singer DM, et al. The Lens Opacities Classification System III. Arch Ophthalmol. 1993;111(6):831–836.
2. American Academy of Ophthalmology. Traumatic Cataract. EyeWiki. Updated 2023. eyewiki.aao.org.
3. Jobling AI, Augusteyn RC. What causes steroid cataracts? A review of steroid-induced posterior subcapsular cataracts. Clin Exp Optom. 2002;85(2):61–75.
4. Cumming RG, Mitchell P, Leeder SR. Use of inhaled corticosteroids and the risk of cataracts. N Engl J Med. 1997;337(1):8–14.
5. Gupta VB, Rajagopala M, Ravishankar B. Etiopathogenesis of cataract: an appraisal. Indian J Ophthalmol. 2014;62(2):103–110.
6. StatPearls. Cataract. Treasure Island (FL): StatPearls Publishing; 2024. Available from: www.ncbi.nlm.nih.gov/books/NBK539699/

Dr Ross MacIntyre BA (Chemistry) MD FRANZCO is a cataract, corneal and refractive surgeon practising in Melbourne, with over 7,000 cataract surgeries performed. He completed subspecialty fellowship training in cornea, complex cataract and refractive surgery at the Wilmer Eye Institute, Johns Hopkins University, and holds a public appointment at the Royal Victorian Eye and Ear Hospital. Consultations are at Northern Eye Consultants, Suite 5, Northpark Hospital Consulting Rooms, 135 Plenty Road, Bundoora. For referrals, call (03) 9466 8822 or use HealthLink EDI nthneyec. For a complete overview of cataract surgery, see corneaeyedoctor.com/cataract-surgery/.