Cataract and Refractive Surgery
Core concepts
Understand cataract grading (LOCS), biometry (optical vs. ultrasound, IOL power formulas - SRK/T for average eyes, Barrett/Hoffer for extremes), and the shift toward swept-source OCT biometry. Know the types of IOLs: monofocal, toric (for regular astigmatism), multifocal/EDOF (diffractive vs. extended depth of focus), and the trade-offs (halos, reduced contrast). Refractive surgery: keratorefractive (LASIK, PRK, SMILE) vs. lens-based (phakic IOL, refractive lens exchange), and the corneal thickness/topography criteria.
Traps
The classic trap is post-refractive surgery IOL calculation - prior myopic LASIK causes hyperopic surprise if standard formulas are used; use the history method or adjusted keratometry. Another is IFIS (intraoperative floppy iris syndrome) in patients on tamsulosin - ask about it preoperatively and modify technique. Questions also test endophthalmitis timing: acute (bacterial, within days) vs. chronic (Propionibacterium, weeks to months, capsular plaque).
Worked example
A patient with prior myopic LASIK needs cataract surgery. Rule of thumb: never trust the corneal power alone - obtain historical refraction and use a post-refractive formula (e.g., Barrett True-K) or the history method; if unknown, use adjusted K values and warn about refractive surprise. For IFIS, use iris hooks or a pupil expander and intracameral phenylephrine.