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Posterior Subcapsular Cataract (PSC)

ROUTINE — Lens

Symptoms

Visual complaints

  • Disproportionate glare and difficulty in bright light or with oncoming headlights, often out of proportion to Snellen acuity.
  • Significant difficulty with near tasks (reading) — near vision is often more affected than distance.
  • Vision may paradoxically improve in dim light or with pupil dilation, since the plaque sits centrally under the posterior capsule.

Clinical Findings

Core findings

  • A granular, plaque-like opacity just anterior to the posterior lens capsule, centered on the visual axis.
  • Best seen with retroillumination — appears as a "snowflake" or breadcrumb-like shadow against the red reflex.
  • Because it sits directly in the visual axis, PSC causes visual symptoms out of proportion to its size compared with nuclear or cortical cataract.

Etiology

Idiopathic/age-related

  • Can occur as an isolated age-related change, though it progresses faster than nuclear or cortical cataract.

Corticosteroids

  • Classic association: chronic steroid use by any route (topical, inhaled, oral, intravitreal) — dose- and duration-dependent.

Ocular inflammation

  • Chronic anterior uveitis — Fuchs heterochromic iridocyclitis is a classic cause of rapid PSC.

Other associations

  • Diabetes mellitus, prior vitrectomy, ocular trauma, radiation exposure, high myopia.

Red Flags

Young patient with PSC

  • Screen for chronic steroid exposure, uveitis (look for keratic precipitates, flare), diabetes, or prior radiation/trauma — PSC in a young patient is rarely purely age-related.

Rapidly progressive PSC with heterochromia

  • Consider Fuchs heterochromic iridocyclitis (stellate KPs, iris atrophy/heterochromia, no posterior synechiae).

Investigations

Clinical exam

  • BCVA with glare testing — may reveal reduced acuity in bright conditions despite good acuity in the dark.
  • Dilated slit-lamp exam with retroillumination to characterize the plaque.

Directed workup if young or rapidly progressive

  • Review medication history for steroid exposure.
  • Anterior chamber exam for uveitis; blood glucose if diabetes is suspected.

Treatment

Address the cause

  • Taper/discontinue steroids if feasible; treat underlying uveitis or diabetes.

Surgical

  • Phacoemulsification with IOL implantation once symptoms (glare, near-vision difficulty) are functionally significant — PSC often warrants earlier surgery than its Snellen acuity alone would suggest.

Clinical Pearl

PSC is the cataract that lies to the Snellen chart — a patient can read 20/25 in the dim exam lane and still be unable to drive at night. Always ask about glare and near-vision symptoms specifically, and test acuity in bright light if the complaint doesn't match the chart.

Differential Diagnosis

  • Nuclear sclerotic cataract
  • Cortical cataract
  • Posterior capsular opacification (post-surgical)
  • Fuchs heterochromic iridocyclitis

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