Cataract knives are precision instruments designed for creating incisions during cataract surgery and other anterior segment procedures. Their primary uses include:
1. Primary Cataract Incisions
- Clear Corneal Incision (CCI)
- Made with a 2.2–3.2 mm keratome (e.g., Alcon Slit Knife, Beaver Blade).
- Provides entry for phacoemulsification probes and IOL insertion.
- Self-sealing design reduces post-op leakage.
- Scleral Tunnel Incision
- Used in manual small-incision cataract surgery (MSICS).
- Requires a crescent knife for a sclerocorneal tunnel.
2. Secondary Incisions (Side Ports)
- Paracentesis
- Made with a 15° or 30° angled knife (e.g., MVR blade).
- Allows insertion of secondary instruments (choppers, viscoelastic cannulas).
- Typically 1 mm wide.
3. Capsulotomy (Anterior Capsule Opening)
- Manual Continuous Curvilinear Capsulorhexis (CCC)
- A cystotome (modified bent needle) or capsulorhexis forceps may be used.
- Some surgeons use ultra-sharp diamond knives for precision.
4. Specialized Procedures
- Corneal Relaxing Incisions (CRIs) for Astigmatism
- Diamond knives (e.g., Atlas CRI knife) create arcuate cuts to flatten steep meridians.
- Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK)
- Trebphine knives or diamond blades prepare donor tissue.
- Glaucoma Surgery (Trabeculectomy)
- 15° Blade creates a scleral flap.
5. Pediatric & Complicated Cataract Surgery
- Smaller, sharper blades (MVR knives) for congenital cataracts.
- Diamond knives for fibrotic capsules (e.g., post-vitrectomy).
Types of Cataract Knives & Their Uses
| Knife Type | Common Uses | Blade Characteristics |
|---|---|---|
| Keratome (Steel/Diamond) | Clear corneal incisions | 2.2–3.2 mm, angled tip |
| MVR Blade | Paracentesis, pediatric cases | 15°–30° sharp tip |
| Crescent Knife | Scleral tunnel incisions | Semi-lunar curved edge |
| Diamond Knife | Premium precision cuts (CRIs, DSAEK) | Ultra-sharp, long-lasting |
| Cystotome | Capsulorhexis initiation | Bent needle tip |
Key Considerations in Knife Selection
- Blade Material
- Stainless steel (cost-effective, reusable).
- Diamond (sharper, more expensive, long-lasting).
- Single-use disposable (reduces infection risk).
- Blade Angle & Geometry
- Sharper angles (15°) for easier penetration.
- Wider angles (30°–45°) for stability in tough corneas.
- Sterilization & Reusability
- Autoclaving for steel blades (limited cycles).
- Ethylene oxide (EtO) gas for diamond knives.