Ptds In — Ophthalmology [2021]

| Component | Function | Key Parameters | |-----------|----------|----------------| | | Excises vitreous gel | Cut rate (5k–20k cpm), duty cycle, port size/gauge | | Infusion system | Maintains intraocular pressure (IOP) | Pressure control (10–60 mmHg), active fluidics | | Aspiration/vacuum | Removes excised vitreous and debris | Vacuum (0–650 mmHg), flow rate (0–50 mL/min) | | Illumination (endolight) | Visualizes posterior segment | Fiber optic, xenon/LED, chandelier vs. handheld | | Wide-angle viewing | Panoramic retinal view | Non-contact (e.g., BIOM, Resight) or contact lenses | | Bipolar diathermy | Hemostasis | Power (0–100%), continuous/pulsed | 3. Gauge Evolution: 20G → 23G → 25G → 27G Smaller gauge = less invasiveness, but trade-offs exist.

| Gauge | Incision size | Suture required? | Vitreous removal speed | Preferred use case | |-------|---------------|------------------|------------------------|--------------------| | 20G | 0.9 mm | Yes | Fastest (but obsolete) | Historic, now rare | | 23G | 0.72 mm | No (sutureless) | Fast | General vitrectomy, diabetic TRD | | 25G | 0.5 mm | No | Moderate | Macular holes, ERM, vitreous hemorrhage | | 27G | 0.4 mm | No | Slower but precise | Macular surgery, pediatric, near-avascular | ptds in ophthalmology

1. Introduction and Historical Context Pars Plana Vitrectomy (PPV) is a microsurgical procedure that removes the vitreous humor from the eye through small incisions in the pars plana (the flat part of the ciliary body). First pioneered by Robert Machemer in the early 1970s, PPV has evolved from a 17-gauge, single-port, laborious procedure into a sophisticated, high-speed, multi-port, sutureless system. | Component | Function | Key Parameters |