OP1.4 | Refractive Surgery: Principles and Indications — Summary & Reflection

KEY TAKEAWAYS

Key takeaways — Refractive Surgery: Principles and Indications:

• Optical principle: excimer laser ablation (193 nm, photoablation) removes corneal stroma to reshape curvature; myopia → central flattening (less power); hypermetropia → peripheral ablation (relative central steepening); astigmatism → cylindrical ablation.

• Corneal laser procedures:
• LASIK: flap (microkeratome/femtosecond) + stromal ablation; rapid recovery; flap risks; most common globally
• PRK: surface ablation (no flap); slower recovery; no flap risk; better for thin corneas and contact sports
• SMILE: femtosecond lenticule extraction through small incision; flapless; minimal dry eye; limited to myopia/myopic astigmatism

• Lens-based procedures:
• Phakic IOL (ICL): high myopia (typically >−8 to −10 D); thin cornea; preserves accommodation; reversible
• RLE: replaces clear lens; high hypermetropia or presbyopic patients; permanently sacrifices accommodation — not for young patients

• Absolute contraindications: keratoconus / subclinical keratoconus (must screen with corneal topography + tomography), active autoimmune disease, significant dry eye, unstable refraction, thin cornea, pregnancy.

• Key complications: post-LASIK ectasia (most serious, almost entirely preventable by screening), DLK, regression, dry eye, halos/glare. Safety record excellent in well-selected patients.

REFLECT

Reflect using Kolb's experiential learning cycle:

Concrete experience: A 24-year-old software engineer comes to you asking for LASIK. He has −4.50 D myopia that has been stable for 3 years. He has no ocular history. His corneal topography shows a symmetric bow-tie astigmatism pattern. Pachymetry: 510 µm. Cycloplegic refraction confirms −4.50 D. Scotopic pupil size: 6.5 mm. Tear film break-up time: 6 seconds (slightly low; normal ≥10 sec).

Reflective observation: He appears to meet most criteria but has two borderline findings: a slightly low tear film BURT and a large scotopic pupil. How do these two findings affect your counselling?

Abstract conceptualisation: What are the mechanisms by which a large scotopic pupil increases the risk of halos/glare after LASIK? Would SMILE be a better option given the dry eye concern — and why?

Active experimentation: If after pre-operative treatment for dry eye (artificial tears, punctal plugs) his TBUT remains 7 seconds, would you proceed with SMILE or defer surgery? Draft the key consent discussion points you would have with this patient before any procedure.