What are the indications and preoperative investigations for each ophthalmic surgical procedure?

Ophthalmic Surgery: Indications and Preoperative Investigations

CATARACT SURGERY

Indications

The primary indication for cataract surgery is visual decline that no longer meets the patient's functional needs and where surgery offers reasonable improvement. 1

Additional indications include:

• Clinically significant anisometropia in the presence of cataract
• Lens opacity interfering with posterior segment diagnosis or management (e.g., blocking view of diabetic retinopathy or macular degeneration)
• Lens-induced inflammation and secondary glaucoma (phacolytic, lens particle, or phacoantigenic)
• Primary angle closure or lens-related glaucoma induced by the crystalline lens 1

Contraindications

Surgery should NOT be performed when:

• Tolerable refractive correction already meets patient needs
• Surgery will not improve visual function and no other indication exists
• Patient cannot safely undergo surgery due to medical/ocular comorbidities
• Appropriate postoperative care cannot be arranged
• Informed consent cannot be obtained for nonemergent surgery 1

Preoperative Investigations

Routine preoperative laboratory testing and medical evaluation are NOT indicated and do not reduce perioperative complications. 1 This is based on large randomized trials demonstrating no benefit to routine testing. 2, 3

Essential Investigations:

• Optical biometry (preferred over ultrasound for IOL power calculation) - uses partial coherence interferometry for superior accuracy 1
• Keratometry for corneal power measurement
• Complete ophthalmic examination including:
  • Best-corrected visual acuity
  • Slit-lamp examination of anterior segment
  • Dilated fundus examination
  • Intraocular pressure measurement
  • Assessment of pupil function
  • Evaluation of tear film and ocular surface
  • Assessment of blepharoptosis (can worsen post-surgery and affects astigmatism measurement) 1

Selective Medical Evaluation:

Consider medical evaluation ONLY for patients with severe, poorly controlled systemic disease:

• Chronic obstructive pulmonary disease
• Poorly controlled hypertension
• Recent myocardial infarction or unstable angina
• Poorly controlled congestive heart failure
• Poorly controlled diabetes 1

Common Pitfall: Despite evidence against routine testing, many facilities still perform unnecessary preoperative labs and ECGs. This delays care without improving outcomes. 2, 3

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REFRACTIVE SURGERY (LASIK, PRK, SMILE)

Indications

Refractive surgery is indicated when patients desire reduced dependence on glasses/contact lenses for occupational, lifestyle, or cosmetic reasons, with stable refraction and realistic expectations. 4

Contraindications

Absolute:

• Unstable refraction (must demonstrate stability over appropriate timeframe)
• Active or recurrent uveitis
• Uncontrolled autoimmune or immune-mediated disease
• Keratoconus or corneal ectasia (identified on topography/tomography)
• Uncontrolled mental illness including severe anxiety/depression
• Unrealistic patient expectations 4

Relative:

• Functional monocularity
• Significant dry eye or ocular surface disease
• Shallow anterior chamber (for phakic IOLs)
• Pregnancy or lactation
• Diabetes mellitus
• History of uveitis 4

Preoperative Investigations

A comprehensive refractive surgery evaluation requires specific measurements beyond standard eye examination to identify surgical candidates and predict outcomes. 4

Mandatory Investigations:

• Manifest refraction (primary measurement)
• Cycloplegic refraction when accuracy is questioned or in younger patients (use tropicamide for rapid onset or cyclopentolate for greater cycloplegia) 4
• Computerized corneal topography/tomography - critical for detecting:
  • Irregular astigmatism
  • Corneal warpage from contact lenses
  • Early keratoconus or ectasia
  • Abnormal pachymetric distribution 4, 5
• Central corneal thickness measurement - essential to:
  • Identify thin corneas
  • Calculate residual stromal bed thickness
  • Assess ectasia risk 4
• Distance and near visual acuity with and without correction
• Evaluation of tear film and ocular surface (dry eye is common complication)
• Ocular motility and alignment assessment 4

Contact Lens Discontinuation Protocol:

• Soft spherical lenses: Discontinue 3 days to 2 weeks before evaluation
• Toric soft lenses and rigid lenses: Discontinue longer period (weeks) due to greater corneal warpage potential
• Verify refractive stability with multiple visits if needed 4

Additional Considerations:

• Lenticular astigmatism assessment: When refraction differs significantly from topography, suspect lenticular astigmatism - may indicate early cataract, making lens surgery preferable to corneal surgery 4
• Pupillometry: Controversial value, but important for counseling about night vision symptoms 4

Common Pitfall: Performing keratorefractive surgery on undetected forme fruste keratoconus leads to post-operative ectasia. Tomography is essential, not optional. 4, 5

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INTRAOCULAR REFRACTIVE SURGERY (Phakic IOLs, Refractive Lens Exchange)

Indications

Intraocular refractive procedures are indicated for high refractive errors beyond safe keratorefractive surgery range, or when corneal surgery is contraindicated. 4

Contraindications

Absolute:

• Unstable refraction
• Visually significant cataract (for phakic IOLs)
• Shallow anterior chamber (for phakic IOLs)
• Corneal endothelial disease including Fuchs dystrophy
• Uncontrolled glaucoma
• Active external disease (blepharitis, severe dry eye)
• Active or recurrent uveitis
• Unrealistic expectations 4

Preoperative Investigations

Intraocular refractive surgery requires all standard refractive surgery investigations PLUS specific anterior segment and endothelial assessments. 4

Essential Additional Investigations:

• Corneal endothelial cell count - critical for phakic IOLs to assess risk of endothelial damage
• Anterior chamber depth measurement - essential for phakic IOL sizing
• Angle assessment via gonioscopy - rule out narrow angles
• Comprehensive dilated fundus examination - especially important in high myopes (retinal detachment risk with refractive lens exchange)
• Optical biometry for IOL power calculation (if refractive lens exchange)
• Assessment for pseudoexfoliation (increases surgical risk) 4

Critical Point: Routine medical testing is NOT required unless specific severe systemic conditions exist, consistent with cataract surgery evidence. 1, 2

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KEY PRINCIPLES ACROSS ALL OPHTHALMIC SURGERY

1. Operating surgeon must perform preoperative assessment to formulate surgical plan and establish patient relationship 1, 4

2. Informed consent is mandatory covering:

   • Expected outcomes and residual refractive error
   • Loss of best-corrected visual acuity risk
   • Night vision symptoms (glare, halos)
   • Infection and inflammation risks
   • Enhancement procedure possibilities
   • Postoperative care arrangements 1, 4

3. Avoid unnecessary testing - routine labs, ECG, chest X-rays do not improve outcomes in low-risk ophthalmic surgery 1, 2, 3

4. Patient cooperation and postoperative care capability must be assessed preoperatively 1