Posterior Subcapsular Cataract

Posterior subcapsular cataract (PSC) is opacity in the posterior cortex just beneath the posterior capsule, in the visual axis, causing disproportionate visual symptoms for its size.

• Causes: corticosteroids (any route), diabetes, ionising radiation, chronic uveitis, retinitis pigmentosa, high myopia, trauma, smoking, and ageing; also seen after vitrectomy, and in myotonic dystrophy and neurofibromatosis type 2.
• Mechanism: migration and aberrant differentiation of lens epithelial cells to the posterior pole, with formation of swollen bladder (Wedl) cells.
• Occurs at younger ages (40s to 50s) and progresses faster than nuclear cataract.

• Marked glare in bright light and with headlights, because pupil constriction places the opaque zone in the visual axis.
• Poor near vision and reading (miosis during accommodation), with relatively good vision in dim light (pupil dilates around the opacity).
• Reduced contrast sensitivity.
• Slit lamp: a granular, vacuolated or plaque like opacity in the central posterior cortex; often best seen with retroillumination or a dilated pupil.
• Check for steroid induced raised intraocular pressure and uveitis.

• Visual acuity in bright light (near and distance) versus dim light, pinhole, glare test.
• Slit lamp with retroillumination; grading by LOCS III (P1 to P5).
• Intraocular pressure, gonioscopy, dilated fundus examination, macular optical coherence tomography (to exclude macular disease explaining symptoms).
• Medication and radiation history; HbA1c; search for uveitis.
• Posterior capsule integrity and plaque thickness at preoperative planning.

• Remove or minimise the cause where possible: lowest effective steroid dose, steroid sparing agents, glycaemic control, and uveitis control.
• Surgery early, because visual symptoms are severe despite mild morphological change. Phacoemulsification with in-the-bag intraocular lens implantation; posterior capsule plaque can be thin and adherent, so a tight capsulorhexis, careful hydrodissection and avoidance of aggressive polishing reduce capsule tears.
• Uveitic cases: control inflammation for at least 3 months before surgery, perioperative prednisolone 0.5 to 1 mg/kg daily or periocular triamcinolone 40 mg, hydrophobic acrylic lens.
• Anticipate posterior capsule opacification (up to 30 to 50 percent in young patients), which is treated with neodymium doped yttrium aluminium garnet (Nd:YAG) laser capsulotomy.
• Cystoid macular oedema prophylaxis: nepafenac 0.1 percent three times daily for 4 to 12 weeks.
• Monitor intraocular pressure after surgery in steroid responders.