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OP8.1-6 | Lens, Cataract and Aphakia — Graded Quiz
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A 58-year-old man undergoes successful phacoemulsification. Two years later he returns with progressive blurring of vision. Slit-lamp shows a wrinkled, hazy posterior capsule behind the IOL. Visual acuity is 6/36. What is the MOST APPROPRIATE treatment?
Correct. PCO is treated definitively by Nd:YAG laser posterior capsulotomy, which creates an optical clearing in the posterior capsule. Repeat surgery is not indicated.
PCO is the commonest late complication after ECCE/phacoemulsification. It is caused by proliferation of residual lens epithelial cells onto the posterior capsule. Treatment is Nd:YAG laser posterior capsulotomy — a simple outpatient procedure — NOT repeat surgery.
PCO (posterior capsule opacification) — the commonest late complication of cataract surgery — is treated by Nd:YAG laser posterior capsulotomy. This outpatient procedure takes minutes and restores vision. Repeat surgery is neither required nor appropriate.
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The crystalline lens is suspended from the ciliary body by the zonule of Zinn. Which part of the lens is correctly identified as providing the main refractive power and consisting of the densest crystallin proteins?
Correct. The adult nucleus contains the oldest, most densely packed lens fibres with the highest crystallin concentration, contributing the greatest share of the lens's refractive power.
The adult nucleus is the innermost compact region of lens fibres, with the highest crystallin protein density and greatest refractive power. Cortical fibres are younger and more hydrated. The capsule is an elastic basement membrane, not a refractive element.
The adult nucleus is the densest, most compact region of the lens. It has the highest crystallin protein concentration and contributes the most refractive power. The cortex consists of younger, more hydrated fibres; the capsule is a structural membrane.
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A 72-year-old woman with a hypermature cataract presents with red eye, photophobia, and elevated IOP. Slit-lamp shows white fluffy material in the anterior chamber and keratic precipitates. There is no crescentic iris shadow. What is the MOST LIKELY diagnosis?
Correct. Phacolytic glaucoma is caused by leakage of lens proteins through the intact capsule of a hypermature cataract. Macrophages engulfing these proteins appear as white fluffy material in the anterior chamber, and KPs develop. IOP rises as the trabecular meshwork is clogged.
Phacolytic glaucoma occurs with a hypermature (Morgagnian) cataract — the liquefied cortex leaks through an intact capsule, and high-molecular-weight lens proteins clog the trabecular meshwork, raising IOP. KPs and white material in AC from macrophages engulfing lens protein are characteristic. Absent iris shadow confirms mature/hypermature lens.
White fluffy material in the AC + KPs + raised IOP in a hypermature cataract = phacolytic glaucoma. Lens proteins leak through the intact capsule; macrophages engulf them and along with the proteins clog the trabecular meshwork. This is a lens-induced open-angle glaucoma.
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During preoperative assessment for cataract surgery, which finding would most strongly indicate the need to DEFER surgery for further systemic workup?
Correct. A BP of 200/120 mmHg in an uncontrolled, unmedicated patient is a contraindication to proceeding. Even local anaesthesia for cataract surgery can precipitate hypertensive crisis. Surgery should be deferred pending BP optimisation.
Cataract surgery under local anaesthesia can precipitate a hypertensive crisis if uncontrolled hypertension is not addressed preoperatively. Blood pressure exceeding 180/110 mmHg is generally considered a threshold requiring deferral for optimisation. A BP of 200/120 mmHg in an untreated patient warrants deferral.
A BP of 200/120 mmHg without regular medication is a strong indication to defer surgery. The accepted threshold for deferral in most protocols is BP above 180/110 mmHg. Well-controlled hypertension (145/90 on medication) and an HbA1c of 7.5% are generally acceptable for proceeding.
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Which cataract surgical technique is MOST APPROPRIATE in a resource-limited setting handling high surgical volume, offering a good visual outcome without requiring expensive phaco equipment, using a scleral tunnel incision of 5-7 mm?
Correct. MSICS is the preferred technique for high-volume, resource-limited settings. Its scleral tunnel (5-7 mm) is self-sealing, requires no sutures in most cases, accepts a rigid PMMA IOL, and does not need expensive ultrasound equipment.
MSICS (manual small incision cataract surgery) uses a 5-7 mm self-sealing scleral tunnel, does not require expensive phaco equipment, allows a rigid PMMA IOL to be placed, and is the high-volume standard in India — including cataract camps under the NPCBVI programme.
MSICS is India's high-volume surgical standard. A 5-7 mm self-sealing scleral tunnel, no expensive equipment, rigid PMMA IOL — all make it ideal for camps and district hospitals. Phacoemulsification requires costly equipment; ECCE needs sutures and has a larger (10-12 mm) incision; ICCE is obsolete.
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A 68-year-old woman has had cataract surgery in her left eye without IOL implantation (aphakia). She requires optical correction. The right eye has normal vision. Why is a high-power convex spectacle lens CONTRAINDICATED as the correction for her left eye?
Correct. Aphakic spectacles magnify the retinal image by 25-30%. In unilateral aphakia this creates intractable aniseikonia — the two retinal images differ so greatly in size that binocular fusion is impossible. Diplopia results. Contact lenses or secondary IOL implantation are the preferred options.
Aphakic spectacles (+10D) produce ~25-30% retinal image magnification. In unilateral aphakia, the fellow eye sees a normal-sized image. The brain cannot fuse a normal image with one 25-30% larger — resulting in aniseikonia and diplopia. Spectacle correction is therefore contraindicated in unilateral aphakia. Contact lens (~7% magnification) or IOL implantation is preferred.
The fundamental problem with spectacle correction of unilateral aphakia is aniseikonia: a +10D convex spectacle lens magnifies the retinal image by approximately 25-30%. The fellow eye sees a normally-sized image. The brain cannot fuse images of such disparate sizes, causing diplopia. This is why spectacle correction is contraindicated in unilateral aphakia.
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An IMG is in the cataract theatre assisting the surgeon during an ECCE. The surgeon asks the IMG to irrigate the eye. Which solution is CORRECT for intraocular irrigation?
Correct. Balanced salt solution (BSS) is the standard intraocular irrigating fluid. Its composition protects the corneal endothelium and other intraocular structures. Normal saline and Ringer's lactate are not suitable for intraocular use.
Balanced salt solution (BSS) is the standard intraocular irrigating fluid. It is isotonic and formulated to be compatible with intraocular structures (corneal endothelium, trabecular meshwork). Normal saline and Ringer's lactate are not isotonic enough for intraocular use and can cause corneal endothelial damage. Distilled water is hypotonic and dangerous intraocularly.
Intraocular irrigation requires Balanced Salt Solution (BSS). This fluid is specifically formulated to be safe for the corneal endothelium and intraocular structures. Normal saline and Ringer's lactate have compositions that are not optimal intraocularly and may cause endothelial damage. Distilled water would cause cell lysis.
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The standard postoperative treatment regimen after uncomplicated cataract surgery (ECCE with IOL) includes which of the following as its primary pharmacological components?
Correct. Postoperative cataract treatment is topical corticosteroid (to suppress inflammation) + topical antibiotic (to prevent infection), both tapered over 4-6 weeks. This is the standard, evidence-based regimen.
Standard postoperative treatment after cataract surgery consists of: topical corticosteroid (e.g. prednisolone 1% or dexamethasone 0.1%) to control inflammation, and topical antibiotic (e.g. moxifloxacin 0.5% or ciprofloxacin 0.3%) to prevent infection — both tapered over approximately 4-6 weeks. Pilocarpine (a miotic) has no role in routine post-cataract care.
The postoperative regimen after cataract surgery is: topical corticosteroid (prednisolone or dexamethasone) + topical antibiotic (moxifloxacin or ciprofloxacin), tapered over 4-6 weeks. Systemic steroids are not routinely required. Pilocarpine would constrict the pupil and is contraindicated in the postoperative period.
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