Phakonit (Phaco-NIT) — Theory Answer

Definition

Introduction / History

• Described by Dr. Amar Agarwal (Chennai, India) in 2001.
• Original Phakonit used a 0.9 mm corneal incision with a 21-gauge phaco needle.
• Later refined to Microphakonit using a 0.7 mm phaco tip and a 0.7 mm irrigating chopper (smallest incision phaco technique) - Microphakonit and Microincisional IOLs.
• It represents the evolution from coaxial phaco -> bimanual MICS -> Phakonit -> Microphakonit.

Principle

Instrumentation

1. Bare/unsleeved phaco needle (21G, later 0.7 mm design) - connected to aspiration.
2. Irrigating chopper - fluid infusion + nucleus chopping, through a separate paracentesis/incision.
3. Trapezoidal or straight needle-knife to fashion the sub-1 mm incisions (hence "needle incision," as opposed to a keratome).
4. Foldable IOL suitable for injection through a small incision (incision is enlarged to ~1.5-2.0 mm at the end for IOL insertion, or a rollable/microincision IOL is used for true MICS).

Surgical Steps

1. Two stab incisions made with a needle: one for the phaco needle (aspiration) and one for the irrigating chopper (infusion) - typically 0.9 mm (or 0.7 mm in microphakonit).
2. Continuous curvilinear capsulorrhexis performed through the same or a third incision.
3. Hydrodissection and hydrodelineation.
4. Nucleus emulsified by bimanual phaco-chop: chopper infuses fluid and chops while the bare needle aspirates fragmented nucleus (no sleeve, so no simultaneous irrigation at the aspiration port).
5. Cortical clean-up by bimanual irrigation-aspiration.
6. Incision enlarged (to ~1.5-2.8 mm depending on IOL platform) for foldable IOL implantation, or a true MICS IOL is injected without enlarging.
7. Wound is generally self-sealing; sutureless.

Advantages

• Minimal surgically induced astigmatism (near astigmatically neutral).
• Faster visual rehabilitation.
• Reduced incidence of wound-related complications (leak, endophthalmitis risk lower with smaller, well-constructed incisions).
• Improved chamber stability during chop due to independent infusion via chopper.
• Useful in patients needing small, sutureless, "no-bandage" surgery.

Disadvantages / Limitations

• Technically more demanding; steep learning curve for bimanual chop.
• Thermal wound burn risk if aspiration flow/vacuum not well balanced (sleeveless needle has no cooling irrigation at the aspiration port itself).
• Needle incision (as opposed to keratome-made incision) can be less precise/uniform, so incision architecture needs practice.
• Available foldable IOLs for true sub-1mm implantation are limited (usually incision still enlarged to insert IOL, partly negating the "small incision" benefit at that final step) unless a genuine microincision IOL (e.g., very high-index rollable lens) is used.
• Not universally adopted; mainly practiced/popularized by a few high-volume surgeons.

Phakonit vs Conventional Coaxial Phaco vs Standard MICS

Exam Tip / Key One-Liners

• Phakonit = phacoemulsification through a needle-made, sub-1 mm incision using bimanual, sleeveless technique.
• Coined and pioneered by Amar Agarwal.
• Progression: Phakonit (0.9 mm) -> Microphakonit (0.7 mm).
• It is a subtype of bimanual MICS (Microincision Cataract Surgery).

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