Expansile Gases Used in Pneumatic Retinopexy
The primary expansile gases used in pneumatic retinopexy are sulfur hexafluoride (SF6) and perfluoropropane (C3F8), with SF6 lasting approximately 2 weeks and C3F8 lasting approximately 6 weeks in the vitreous cavity. 1
Gas Properties and Duration
Sulfur Hexafluoride (SF6)
- SF6 remains in the eye for approximately 2 weeks (14-16 days), providing intermediate-duration tamponade 1, 2
- Expands to approximately 2 times its injected volume 2
- Has been successfully used in pneumatic retinopexy with reported success rates of 64.9% for retinal reattachment in non-vitrectomy cases 3
- Offers a balance between adequate tamponade duration and shorter positioning requirements compared to longer-acting gases 4
Perfluoropropane (C3F8)
- C3F8 remains in the eye for approximately 6-8 weeks (28 days or longer), providing the longest duration tamponade among commonly used gases 1, 2
- Expands significantly more than SF6, with greater expansile properties 5
- Provides nine times the longevity of air and four times the longevity of SF6 2
- May be preferred for larger macular holes (>400 μm) or cases requiring prolonged tamponade 1
Perfluoroethane (C2F6)
- C2F6 remains in the eye for approximately 16 days, offering an intermediate option between SF6 and C3F8 2
- Demonstrates efficacy similar to other perfluorocarbon gases in pneumatic retinopexy, with 71% single-procedure success rates 6
- Less commonly used than SF6 or C3F8 in current practice 5
Gas Concentration Considerations
Non-Expansile vs. Expansile Concentrations
- Non-expansile or minimally expansile concentrations of C3F8 or SF6 should be used when a full-thickness or deep lamellar macular hole is suspected to avoid excessive expansion 1
- Pure gas injections result in maximum expansion, which must be carefully considered to avoid dangerous intraocular pressure elevation 5
Critical Safety Considerations
Intraocular Pressure Complications
- Transient elevation of intraocular pressure occurs in approximately 26% of patients on the first postoperative day 3
- Central retinal artery occlusion can occur with elevated pressure, resulting in permanent vision loss, particularly in diabetic patients 3
- Patients must avoid travel to altitudes above 2000 feet during the gas tamponade period to prevent dangerous IOP elevation 1
- Scheduled postoperative visits are essential to monitor and manage IOP elevations 1
Anesthesia Precautions
- Nitrous oxide gas must be avoided during at least the last 10 minutes of air-fluid exchange when general anesthesia is used, as it can result in unpredictable gas fill postoperatively 1
Cataract Formation
- Gas-induced lens opacities are a major complication, with development or progression of mild cataract changes occurring in approximately 27% of phakic patients 5, 3
- The risk of cataract progression following gas tamponade in phakic eyes is high and should be discussed preoperatively 1
Positioning Requirements
- Face-down positioning duration varies based on gas type and hole size, with longer positioning potentially required for holes larger than 400 μm 1
- C3F8's longer duration may allow for more flexible positioning protocols compared to shorter-acting gases 1
- Patients must avoid supine (face-up) positioning even when strict face-down positioning is not required 1
Alternative Tamponade Agents
Air
- Air lasts only days in the vitreous cavity, significantly shorter than expansile gases 1, 2
- High closure rates have been reported with air tamponade when combined with ILM peeling, though this may not apply to larger macular holes (>400 μm) 1
Silicone Oil
- Silicone oil provides long-term tamponade and may be used for patients who cannot position face-down 1, 7
- Requires a second operation for removal and generally produces inferior anatomic and visual results compared to gas tamponade 1
- May be considered in selected cases where gas tamponade is contraindicated or positioning is impossible 1, 7