Cataract Study Guide

📖 Core Concepts Cataract – clouding of the eye’s crystalline lens that reduces light transmission, leading to visual impairment. Lens Opacities Classification System III (LOCS III) – grades nuclear, cortical, and posterior subcapsular (PSC) opacities on a 1‑5 scale. Phacoemulsification – ultrasonic fragmentation of the lens through a small corneal incision; the modern gold‑standard surgical method. Posterior Capsular Opacification (PCO/ “after‑cataract”) – proliferative thickening of the posterior capsule after surgery; treated with Nd:YAG laser capsulotomy. Visual Acuity (VA) – primary functional measure; surgery is indicated when VA loss impairs daily activities or quality of life. 📌 Must Remember Cataracts cause ≈40 % of global blindness and ≈28 % of visual impairment (2020 data). Risk factors: aging, diabetes, long‑term corticosteroids, smoking, UV‑B exposure, poor nutrition, obesity, chronic kidney disease, autoimmune disease. Types & hallmark symptoms Nuclear: loss of distance vision > near vision. Cortical: spoke‑like peripheral opacities → glare, especially at night. Posterior subcapsular: bright‑light glare, steroid‑related. Indications for surgery: functional impairment, VA < 20/40 (or patient‑reported difficulty) despite optimal correction. Post‑op outcomes: 90 % achieve 20/40 or better corrected vision. Major complications: retinal detachment (0.4 % within 5.5 yr), endophthalmitis (<0.1 %), corneal & cystoid macular edema (1 %). 🔄 Key Processes Phacoemulsification Steps Topical or injectable anesthesia. Small corneal incision (≈2.2–2.8 mm). Capsulorhexis – circular opening of anterior capsule. Ultrasonic emulsification of lens nucleus. Irrigation/aspiration of cortical material. Insertion of intraocular lens (IOL) into capsular bag. LOCS III Grading Examine lens under slit‑lamp → assign 1 (clear) to 5 (severe) for nuclear, cortical, PSC components. Nd:YAG Laser Capsulotomy Create a central opening in opacified posterior capsule → restores visual axis. 🔍 Key Comparisons Phacoemulsification vs. ECCE Phaco: small incision, ultrasonic lens removal, faster recovery. ECCE: larger (10–12 mm) incision, manual extraction, older technique. Monofocal vs. Multifocal IOL Monofocal: corrects distance or near vision; fewer visual disturbances. Multifocal: provides both distance & near focus; higher risk of halos/glare. Nuclear vs. Cortical vs. PSC Cataract Nuclear: central opacity, worsens distance vision. Cortical: peripheral spokes, prominent night glare. PSC: posterior capsule, intense glare; strongly linked to steroids. ⚠️ Common Misunderstandings “All cataracts need surgery.” – Early or mild cataracts may be observed; surgery is for functional impairment. “Vitamin supplements cure cataracts.” – Evidence for supplementation (A, C, E, lutein/zeaxanthin) is mixed; they may slow progression but do not reverse existing opacity. “Only elderly get cataracts.” – Childhood cataracts account for 5–20 % of pediatric blindness; congenital forms require prompt treatment. 🧠 Mental Models / Intuition “Lens = clear window.” Think of the lens as a window: oxidation → dust (protein clumps) → cloudiness → less light passes. “UV & smoking = rust on steel.” Both accelerate oxidative damage, analogous to rust weakening metal. “Surgical incision size ≈ recovery speed.” Smaller incisions (phaco) → quicker healing, less induced astigmatism. 🚩 Exceptions & Edge Cases Posterior subcapsular cataract may develop rapidly in patients on systemic/topical steroids even at a young age. High‑myopic eyes have higher risk of postoperative retinal detachment. Congenital cataract → risk of amblyopia; requires surgery within weeks‑months to prevent permanent vision loss. 📍 When to Use Which Choose Phacoemulsification for most age‑related cataracts (small incision, fast rehab). Select ECCE when lens nucleus is extremely dense (e.g., mature cataract) or when phaco equipment unavailable. Opt for Multifocal IOL if patient desires spectacle‑independence for both distance and near and accepts possible halos. Use Monofocal IOL for patients prioritizing visual quality or those with occupations sensitive to halos (e.g., pilots). Apply Nd:YAG capsulotomy only after documented PCO causing visual decline, not prophylactically. 👀 Patterns to Recognize Glare + night difficulty → think cortical or PSC (look for peripheral spokes or posterior opacities). Rapid vision loss in a steroid‑treated patient → suspect PSC cataract. Bilateral, slowly progressive blur in an elderly → typical age‑related nuclear cataract. Haloes around lights + lens hydration changes → indicates cortical cataract. 🗂️ Exam Traps Distractor: “Vitamin C supplements reverse cataracts.” – Wrong; they may slow progression, not reverse. Distractor: “All cataract surgeries require large incisions.” – Incorrect; phaco uses ≤3 mm incisions. Distractor: “Posterior capsule opacification occurs immediately after surgery.” – It develops months‑to‑years later. Distractor: “Endophthalmitis risk is >1 %.” – Actual risk is <0.1 %. Distractor: “Smoking only affects nuclear cataracts.” – Smoking increases risk for all cataract types, especially nuclear. --- Use this guide to review core facts, visualize key processes, and avoid common pitfalls before your exam.