Lens and Cataract Surgery
This section covers lens and cataract surgery: cataract types, biometry, IOL power, phacoemulsification, complications, and postoperative care. The exam tests preoperative calculation and intraoperative judgement.
Core rules and concepts
- Cataract is classified by age and morphology: nuclear sclerotic, cortical, posterior subcapsular, traumatic, and metabolic.
- Biometry uses axial length and keratometry; optical coherence biometry is preferred, and IOL formulas are chosen by axial length and previous refractive surgery.
- Aim for emmetropia in most eyes; target myopia in selected high-myopia or monovision cases after counselling.
- Phacoemulsification uses ultrasound to emulsify the nucleus; viscoelastic protects endothelium and maintains the anterior chamber.
- Posterior capsule rupture with vitreous prolapse requires stopping phaco, anterior vitrectomy, and controlled IOL placement; endophthalmitis is a rare emergency after surgery.
Worked example
During phacoemulsification in a 78-year-old with pseudoexfoliation, the posterior capsule ruptures and vitreous presents. The surgeon stops phaco, performs a limited anterior vitrectomy with triamcinolone to identify vitreous, and assesses capsular support. Because residual support is adequate, a three-piece IOL is placed in the sulcus rather than the bag. Haptics are kept out of the vitreous, and the wound is secured. Postoperative review checks IOP and fundus.
Traps that cost marks
Do not implant an IOL blindly after capsule rupture. Ignoring axial length or keratometry causes refractive surprise. In endophthalmitis, urgent vitreous tap and intravitreal antibiotics are required; topical antibiotics alone are inadequate. Avoid high ultrasound energy near a weak endothelium.