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OP8.3 | Cataract Surgery Preoperative Evaluation and Counselling — SDL Guide (Part 2)

Ocular Examination for Surgical Planning

Beyond visual acuity, the surgeon needs a detailed anatomical assessment of the eye to plan the operation safely and anticipate technical challenges. This examination proceeds from front to back.

Corneal Assessment: The slit-lamp examination evaluates corneal clarity, presence of scars, keratoconus (irregular astigmatism — requiring special IOL selection), and signs of Fuchs' endothelial dystrophy (guttata — small central excrescences on Descemet's membrane, predisposing to post-operative corneal decompensation). Specular microscopy quantifies endothelial cell density; low counts direct the choice of surgical technique toward MSICS rather than phacoemulsification.

Anterior Chamber Depth and Angle: A shallow anterior chamber increases the risk of phacomorphic glaucoma and may complicate lens manipulation during surgery. Slit-lamp estimation (Van Herrick grading) or anterior segment OCT provides this information. Gonioscopy assesses angle anatomy if glaucoma coexists.

Iris and Pupil: Dilated pupil size is critical for phacoemulsification — a poorly dilating pupil (common in patients on tamsulosin for prostatic hypertrophy — intraoperative floppy iris syndrome, IFIS) requires specific surgical precautions. Posterior synechiae (from prior uveitis) may prevent adequate dilation.

Lens Assessment on Slit-Lamp: Confirm morphological type (nuclear/cortical/PSC), stage of maturity, and any subluxation or phacodonesis (lens trembling, indicating weak zonules — surgical risk factor).

IOP Measurement (Goldmann Applanation Tonometry): IOP must be controlled (<21 mmHg) before elective surgery. Uncontrolled glaucoma requires treatment prior to cataract surgery — or a combined procedure (phaco-trabeculectomy or phaco-MIGS) may be planned.

Fundus Examination (Indirect Ophthalmoscopy or 90D lens): Assess the optic disc (glaucomatous cupping?), macula (age-related macular degeneration, diabetic macular oedema, epiretinal membrane), and peripheral retina (lattice degeneration, retinal breaks). If fundus view is obscured by dense cataract, B-scan ultrasonography is mandatory to exclude retinal detachment.

Biometry: Axial length + keratometry → IOL power. Inaccurate biometry is the commonest cause of unexpected post-operative refractive error. Patients with a history of refractive laser surgery (LASIK/PRK) need special modified formulae (Barrett True-K, Shammas) because keratometry overestimates corneal power.

Systemic Evaluation and Fitness for Surgery

Cataract surgery is typically performed under local (topical, peribulbar, or retrobulbar) anaesthesia with a cooperative, still patient — but even 'minor' eye surgery can precipitate a systemic crisis in a patient with uncontrolled disease. Systemic evaluation is therefore mandatory before listing any patient for surgery.

Diabetes Mellitus: The most common systemic comorbidity in cataract patients in India. Diabetics are at higher risk of post-operative infection (including endophthalmitis) and of poor wound healing. Pre-operative blood glucose should be checked; ideally, fasting blood glucose should be below 200 mg/dL on the morning of surgery, and HbA1c should reflect reasonable recent control (the exact threshold varies by institution, but persistent HbA1c >10–11% warrants deferral and endocrinology review). Diabetics with concurrent diabetic macular oedema (DMO) may have limited visual gain from cataract surgery alone; intravitreal anti-VEGF treatment for DMO may be needed separately.

Hypertension: Blood pressure should be controlled (systolic <180 mmHg, diastolic <110 mmHg) before elective surgery. Severe uncontrolled hypertension increases the risk of expulsive choroidal haemorrhage — a rare but catastrophic intraoperative complication causing sudden massive bleeding behind the choroid, often leading to blindness.

Anticoagulants and Antiplatelet Drugs: Warfarin, heparin, aspirin, clopidogrel. The risk of stopping these agents (thromboembolism, stroke) must be weighed against the risk of continuing (subconjunctival haemorrhage is common and benign; retrobulbar haemorrhage — rare but can cause orbital compartment syndrome). Current evidence generally supports continuing aspirin through cataract surgery; warfarin decisions require cardiology input. Topical and peribulbar anaesthesia are preferred over retrobulbar blocks in anticoagulated patients.

Cardiac and Respiratory Status: General anaesthesia is rarely required for cataract surgery in adults, but patients with severe anxiety, intellectual disability, or inability to cooperate may need it. In those cases, full cardiac/respiratory anaesthetic fitness assessment is mandatory.

Bleeding Disorders: Factor deficiencies, thrombocytopenia — assess clotting profile. Severe thrombocytopenia (platelets <50,000/µL) is a relative contraindication to subconjunctival injection and retrobulbar block.

Medications Relevant to the Eye: Beyond tamsulosin (IFIS), note systemic steroids (PSC cataract — already confirmed), chlorpromazine (anterior subcapsular deposits — may complicate keratometry), and amiodarone (corneal deposits affecting refractive measurements).

Interpreting Preoperative Findings — When to Proceed, When to Defer

The preoperative evaluation culminates in a clinical synthesis: integrating the visual, ocular, and systemic findings into a decision about whether to proceed with surgery, under what conditions, and with what expected outcome. This interpretive step is where diagnostic skill becomes surgical judgement — it is not algorithmic, and it cannot be delegated to a checklist alone. A careful clinician must weigh the patient's functional impairment against the risks posed by their ocular and systemic status, and must be prepared to defer or modify the surgical plan when risk exceeds acceptable benefit. The ability to make this integrated judgement, and to communicate it clearly to the patient, is what this SDL equips you with.

When to PROCEED: The patient has visually significant cataract causing functional impairment; systemic conditions are controlled; ocular anatomy is favourable; posterior segment is healthy and the visual prognosis is good; corneal endothelial density is adequate (≥1500 cells/mm² for phacoemulsification, or MSICS chosen for borderline endothelium); biometry is available and consistent; informed consent can be obtained.

When to DEFER and OPTIMISE:
- Uncontrolled DM (fasting glucose >250 mg/dL on the day, or very high HbA1c) → refer to physician/endocrinologist
- Hypertension >180/110 mmHg → medical management first
- Active uveitis or ocular infection → treat the inflammation first (active uveitis increases risk of CMO and synechiae)
- Recent MI/stroke within 3–6 months → cardiologist clearance required
- Uncorrected coagulopathy → haematology review

Managing Expectation Based on Concurrent Pathology:
This is perhaps the most important counselling task. If the patient has:
- Dry AMD with geographic atrophy: Cataract surgery will remove the lens opacity but vision will remain limited by macular disease. Patients must understand they may improve from 6/60 to 6/24, not 6/6.
- Glaucomatous field loss: Central vision may improve, but field defects will remain.
- Dense amblyopia: The operated eye was never seeing well and will not see well post-operatively — surgery is still indicated to allow fundus monitoring but the patient must be counselled accordingly.
- Diabetic macular oedema: Anti-VEGF treatment should be considered before or concurrent with cataract surgery.