About This Page
This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Cataracts cause gradual painless decline in vision, glare, halos, and difficulty with night driving
- Age-related cataract is most common; risk factors include diabetes, corticosteroids, UV exposure, smoking, trauma, and radiation
- Exam: reduced red reflex and lens opacity; vision may improve with pinhole early but not when advanced
- Definitive treatment is surgical phacoemulsification with intraocular lens implantation when symptoms impair function
- USMLE pearl: painless cloudy vision with glare and absent red reflex = cataract; painful red eye is not cataract
Overview
A cataract is an opacity of the crystalline lens that scatters light and reduces retinal image quality. Most adult cataracts are age-related, but cataracts may also be congenital, traumatic, metabolic, medication-induced, or radiation-related. The major adult subtypes are nuclear sclerotic, cortical, and posterior subcapsular cataracts. Cataracts are reversible with surgery and are a leading cause of treatable visual impairment.
Epidemiology
Cataracts are extremely common with aging and become clinically significant in many adults over 65. Risk factors include age, diabetes mellitus, chronic corticosteroid exposure, smoking, ultraviolet light exposure, ocular trauma, prior intraocular inflammation, prior vitrectomy, radiation exposure, high myopia, and genetic syndromes. Posterior subcapsular cataracts are particularly associated with corticosteroids, diabetes, and radiation.
Clinical Features
Symptoms
Gradual painless blurry or cloudy vision
Glare, halos, and difficulty driving at night
Reduced contrast sensitivity and faded color perception
Frequent changes in eyeglass prescription; nuclear cataract may cause “second sight” from myopic shift
Acute painful vision loss is not typical and should prompt evaluation for angle closure, keratitis, or vascular occlusion
Signs
Reduced red reflex on ophthalmoscopy
Lens opacity on slit-lamp examination
Nuclear sclerosis: yellow-brown central lens opacity and myopic shift
Cortical cataract: spoke-like peripheral opacities causing glare
Posterior subcapsular cataract: glare and near-vision difficulty disproportionate to appearance
Investigations
First-line
Visual acuity testingQuantifies functional impact; glare testing may reveal disability not captured by high-contrast acuity
Slit-lamp examinationIdentifies cataract type, density, and other anterior segment pathology
Dilated fundus examinationAssesses retina and optic nerve; if view is limited, ocular ultrasound may be needed
Second-line
RefractionDetermines whether spectacles can improve vision; cataract surgery considered when refraction no longer meets functional needs
BiometryMeasures axial length and corneal power for intraocular lens calculation before surgery
B-scan ultrasoundUsed if dense cataract obscures fundus and retinal pathology must be excluded
Specialist
Preoperative ocular assessmentEvaluate corneal disease, glaucoma, pseudoexfoliation, zonular weakness, diabetic retinopathy, AMD, and anesthesia risk
1
Conservative measures
- Update refraction and optimize lighting for mild symptoms
- Reduce glare with sunglasses, anti-reflective lenses, or driving modification
- Address reversible contributors: ocular surface disease, uncontrolled diabetes, medication review
2
Indications for surgery
- Cataract surgery is indicated when visual impairment interferes with activities of daily living, driving, work, reading, or disease monitoring
- Surgery may be indicated to improve visualization/treatment of retinal disease even if visual complaint is modest
- Do not base surgery solely on visual acuity number; functional impairment is central
3
Surgery
- Standard US approach: small-incision phacoemulsification with foldable intraocular lens implantation
- Most procedures are outpatient under topical/local anesthesia with light sedation
- Preoperative biometry determines IOL power and refractive target
- Postoperative drops commonly include topical antibiotic, corticosteroid, and/or NSAID depending on surgeon protocol
4
Special situations
- Diabetic retinopathy and macular edema should be identified and managed before/after surgery
- Pseudoexfoliation increases zonular weakness and glaucoma risk
- Posterior capsular opacification after surgery is treated with Nd:YAG laser capsulotomy when visually significant
Complications
- Functional impairment: Falls, motor vehicle crashes, reduced reading, and loss of independence
- Phacomorphic angle closure: Large lens can precipitate angle closure in susceptible eyes
- Surgical complications: Posterior capsule rupture, endophthalmitis, cystoid macular edema, retinal detachment, corneal edema, IOL dislocation
- Posterior capsular opacification: Common late complication treated with Nd:YAG capsulotomy
- Worsening diabetic macular edema: Requires retinal optimization and follow-up
USMLE Step 2 CK Exam Tips
- 1Gradual painless cloudy vision + glare + decreased red reflex = cataract
- 2Posterior subcapsular cataract is associated with steroids, diabetes, and radiation
- 3Definitive treatment is phacoemulsification with intraocular lens implantation
- 4Cataract surgery is based on functional impairment, not a strict visual acuity cutoff
- 5Second sight = nuclear sclerosis causing myopic shift and temporary near-vision improvement
- 6Absent red reflex in an adult suggests cataract; in a child, leukocoria differential includes retinoblastoma
- 7Painful red eye with cloudy cornea is angle closure, not cataract
- 8Posterior capsular opacification after cataract surgery is treated with Nd:YAG laser capsulotomy
practicetest your knowledge on cataractsApply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — ophthalmology and beyond.
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