The use of intraocular gas in retina procedures can be traced back to 1911, when Ohm treated 2 patients with retinal detachments by injecting intravitreal air, successfully reattaching 1 retina.1 Techniques for air tamponade evolved over subsequent decades until 1973 when Norton, inspired by the use of sulfur hexafluoride (SF6) gas for pneumothorax in pulmonary tuberculosis, described its application as an intraocular tamponade.2 With the development of pars plana vitrectomy in the early 1970s and the refinement of pneumatic retinopexy in the early 1980s, intraocular gas quickly became a cornerstone of modern retinal detachment repair.
Although multiple gases have been investigated for ophthalmic use, the modern use of fluorinated gases stems from work published by Lincoff et al.3 When used for intraocular procedures, fluorinated gases are nontoxic, chemically inert, demonstrate predictable expansion, and are gradually absorbed into the venous circulation before being exhaled. Today, SF6 and perfluoropropane (C3F8) are the most widely used gases for retinal tamponade in the United States, while perfluoroethane (C2F6) is used less frequently.4
The properties of fluorinated gases have also made them useful in other areas of medicine. For example, SF6 microbubbles may be used as a contrast agent in vascular ultrasonography, while hydrofluorocarbon gases such as isoflurane, sevoflurane, and desflurane are commonly used inhalational anesthetics. Fluorinated gases are also used as propellants in metered dose inhalers and as refrigerants which facilitate the cold storage of medications.
Figure 1. Rhegmatogenous retinal detachment successfully repaired using pars plana vitrectomy with air tamponade. Image courtesy Trent Chiang, MD, and Geoffrey G. Emerson, MD, PhD, FASRS.
Types and Properties of Fluorinated Gases
Fluorinated gases are synthetic compounds and do not naturally occur in significant quantities. They are generally divided into 4 types: hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), SF6, and nitrogen trifluoride (NF3). HFCs are primarily used as refrigerants, and unlike chlorofluorocarbon (CFC) refrigerants, they do not contain the chlorine atoms that react with atmospheric ozone molecules. In recognition of the risks associated with ozone depletion, the use of HFCs expanded significantly following the 1989 adoption of the Montreal Protocol in which member countries agreed to phase out CFCs.
While fluorinated gases do not contribute to ozone depletion, they do have high global warming potential (GWP). GWP is a standardized metric used to compare how much a particular gas will warm the surface of the Earth when released into the atmosphere relative to carbon dioxide (CO2). It is typically expressed as the cumulative warming effect of one metric ton of a particular gas over a 100-year period (GWP100), with the warming potential of CO2 defined as 1. Fluorinated gases have exceptionally high warming potential, with SF6 gas having the highest GWP100 of any gas yet evaluated (Table 1).5 To facilitate comparisons, when discussing the contribution of a given quantity of gas to global warming, it is common practice to report the mass of CO2 which would cause an equivalent degree of warming (CO2e). This is calculated by multiplying the mass of a gas by its GWP100.
Because of their high GWP100 values, even small amounts of fluorinated gas emissions can contribute significantly to global warming. In recognition of this, members of the 1997 Kyoto Protocol agreed to regulate and reduce emissions of HFCs, PFCs, and SF6 in addition to carbon dioxide, methane, and nitrous oxide. The remaining fluorinated gas, NF3, was later added by amendment.
Despite not participating in the Kyoto Protocol, the United States tracks and regulates fluorinated gases through a combination of federal and state initiatives. Since 1990, the US Environmental Protection Agency (EPA) has published an annual report detailing the sources and amounts of greenhouse gas (GHG) emissions, as well as GHG “sinks”—sources of greenhouse gas uptake such as vegetation growth. However, the last published report was in 2022, and in 2025 the EPA released a proposal to end the EPA’s GHG reporting program.6
In the most recent report, fluorinated gases comprised 3.1% of all greenhouse gas emissions in the United States. While most of these were HFCs, PFCs and SF6 accounted for 14.3 million metric tons (MMT) CO2e out of the total 6,343.2 MMT CO2e emitted in 2022. While most fluorinated gas emissions were produced by nonmedical industries, according to a 2024 EPA report, “Other Scientific Applications,” which includes medical use, accounted for the emission of 100,000 metric tons CO2e. While this is a significant quantity of CO2e, it constitutes a very small proportion of overall US emissions (0.0016%).7
Health and Environmental Impacts of Greenhouse Gases
Climate changes which may result from GHG emissions may be associated with both systemic and ocular adverse health effects. These potentially include an increased risk of retina-related pathology. Changing weather patterns have been associated with increased prevalence of disease vectors associated with infectious uveitis.8 Ambient air pollution may be associated with an increased risk of central retinal artery occlusion, retinal vein occlusion, diabetic retinopathy, uveitis, and age-related macular degeneration.9-13 In addition, an association between heat waves and tractional retinal detachment has been reported though causality is unclear.14
In addition to the ethical case for reducing the environmental impact of retinal specialty care, a practical case is also prudent to consider given a recent increase in environmental regulation. For example, in 2023 the European Union reached an agreement (EU Regulation 2024/573) that aims to phase out fluorinated gas use by 2050.15 While exceptions are likely to be made for medical uses, the rules may make current usage patterns increasingly more costly and difficult.
The carbon footprint associated with fluorinated gas use for retinal surgeries in the United States is unknown and attempts to estimate it are limited by incomplete data. While it is commonly cited that 225,000 to 300,000 vitrectomies are performed annually in the United States, the sources of these figures remain obscure.16-18 Furthermore, the annual number of gas-utilizing procedures, the types of gases used, and the average amounts of gas used per procedure have not been reported.
However, extrapolation from available data may provide general estimates. The California Air Resources Board (CARB) requires annual reporting of SF6 sales, and in 2024, 826 kg of SF6 gas were sold to the medical industry in California.19 The American Society of Retina Specialists (ASRS) lists 387 ASRS members practicing in California. This total includes both surgical and nonsurgical members, and individual gas usage likely varies widely among surgeons. If we assume that the majority of the SF6 is used for eye surgery, a rough estimate of approximately 2 kg SF6 per retina specialist per year can be derived. Extrapolating this figure to all US retina specialists (n=3,126; includes both active and inactive ASRS members), yields an estimated national total of roughly 6,252 kg of SF6 used for retina surgery in 2024. This amount of SF6 has a GWP100 of over 150,000 metric tons CO2e, which exceeds the total amount of SF6 reported for medical use by the 2022 GHG Inventory. This discrepancy may indicate rising amounts of SF6 emission over time, differences in inventory accounting methods, or inaccurate use assumptions. This figure also does not account for PFC emissions produced by retinal surgery. Additional research or access to industry data would potentially aid in clarification of these figures.
Strategies to Reduce Gas Use
With the aim of reducing the carbon footprint of retina specialty care, it is worth discussing ways to reduce the amount of gas used by retina specialists. This could be accomplished by favoring procedures that require less (or no) gas, such as primary scleral buckling for retinal detachment repair, or by choosing alternative agents for tamponade. Recent studies have suggested that air tamponade can have similar efficacy to gas when used for retinal detachment repair (Figure 1).20-23 Using fluorinated gases other than SF6 could also be beneficial, and dilute concentrations of C2F6 and C3F8 (8% and 6% respectively) have been shown to provide similar retinal contact angles compared to SF6 over the first 7 days postoperatively.24
Theoretically, even when SF6 is used for tamponade, the gas-related carbon footprint of a single retinal surgery is exceedingly small. Previous publications have assumed that 25 mL of 100% SF6 gas is used per pars plana vitrectomy (PPV), which is equal to 3.9 kg CO2e.25 This is approximately the amount of CO2 emitted by driving 10 miles in a passenger vehicle. However, given the large number of retinal surgeries performed in the US, and variations inherent to a real-world setting, the gas-related carbon footprint of retinal surgeries may be significantly more substantial.
In a multicenter study from the United Kingdom by Moussa et al, the volume of gas that should have been required for a particular number of surgeries was compared to the amount actually used.25 For SF6, only 1,206 surgeries were performed when the total amount of SF6 gas that was actually used should have been sufficient for 49,108 surgeries (2.5%). For C2F6 and C3F8, the respective number of surgeries performed were only 4.2% and 0.9% of the total that should have been able to be performed given the total amounts of gas used.25 This suggests a significant amount of gas was wasted over the course of nearly 5,000 surgeries. The reasons for this may include variable amounts of gas used by different surgeons, gas wasted by vitrectomy machine or manual canister purge cycles, gas leakage during canister nonuse (eg, valve inadvertently left open or inadequately closed), or expiration of the gas canister prior to full usage.
In the UK study, smaller canister volumes were associated with significantly improved efficiency. In the US market, ISPAN gas canisters (Alcon) are currently available in 20 g and 125 g sizes; the previously available 450 g canister is no longer being distributed. Assuming 25 mL are used per PPV surgery, the number of theoretical surgeries that each canister should allow at standard temperature and pressure (STP) are presented in Table 2. Each canister has an expiration date of 2 years, and all gas remaining in canisters after the date of expiration is typically discarded.
In addition to favoring the use of smaller canisters, new products may further reduce the amounts of wasted gas. Alcon has recently received FDA approval for single-use gas systems for both surgery and in-office use. Unifeye is a gas delivery system for vitrectomy surgery that contains a “pico-cylinder” of pressurized and liquefied SF6 or C3F8. Users can set the desired gas concentration, and the device will dispense the necessary quantity of gas and blend it with filtered air in a 50 mL syringe.26 Unipexy is similar, but this device provides pure SF6 or C3F8 and has an integrated syringe and needle for ease of use in pneumatic retinopexies.26 The actual masses of gas contained by each device are not published, but, in theory, even if each unit contains more gas than is necessary for a particular procedure, there may be less gas use per surgery due to reduced gas waste. Additional work is necessary to determine the overall environmental impact of this approach.
Other useful interventions may focus on recycling programs for unused gas, designing canister regulators to minimize gas loss, or implementing systems to capture unused amounts of gas rather than venting them into the atmosphere. These interventions are already being implemented in other fields, including leak detection protocols in the electrical industry and the use of volatile capture technology systems to capture exhaled fluorinated anesthetic gases.
Conclusion
While fluorinated gas emissions are only one part of the environmental impact of retina specialty care, they may be an attractive target for carbon footprint reduction given that the amount needed for patient care is dwarfed by the amount currently used in clinical practice. Additional work on methods to reduce gas waste could yield meaningful environmental benefits. Opportunity exists for collaboration between industry partners and professional societies, such as ASRS and AAO, to standardize best practices for gas conservation. Furthermore, considering recent government regulations, it may be in the best interest of the specialty to plan for a future where the use of fluorinated gases is minimized. RP
References
1. Ohm J. Über die Behandlung der Netzhautablösung durch operative Entleerung der subretinalen Flüssigkeit und Einspritzung von Luft in den Glaskörper [On the treatment of retinal detachment by surgical evacuation of subretinal fluid and injection of air. Albrecht von Græfe’s Archiv Für Ophthalmologie. 1911;79(3):442-450. https://doi.org/10.1007/BF01977971
2. Norton EW. Intraocular gas in the management of selected retinal detachments. Trans Am Acad Ophthalmol Otolaryngol. 1973;77(2):OP85-OP98.
3. Lincoff A, Haft D, Liggett P, Reifer C. Intravitreal expansion of perfluorocarbon bubbles. Arch Ophthalmol. 1980;98(9):1646. doi:10.1001/archopht.1980.01020040498023
4. Vaziri K, Schwartz SG, Kishor KS, Flynn HW Jr. Tamponade in the surgical management of retinal detachment. Clin Ophthalmol. 2016;10:471-476. doi:10.2147/OPTH.S98529
5. Smith C, Nicholls CRJ, Armour K, et al. The earth’s energy budget, climate feedbacks, and climate sensitivity supplementary material. Intergovernmental Panel on Climate Change. 2021. Accessed October 27, 2025. https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Chapter07_SM.pdf
6. US Environmental Protection Agency. EPA releases proposal to end the burdensome, costly greenhouse gas reporting program, saving up to $2.4 billion. News release. September 12, 2025. Accessed October 27, 2025. https://www.epa.gov/newsreleases/epa-releases-proposal-end-burdensome-costly-greenhouse-gas-reporting-program-saving-24
7. EPA (2024) Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2022. U.S. Environmental Protection Agency, EPA 430-R-24-004. https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks-1990-2022.
8. Khairallah M, Mahendradas P, Curi A, Khochtali S, Cunningham ET Jr. Emerging viral infections causing anterior uveitis. Ocul Immunol Inflamm. 2019;27(2):219-228. doi:10.1080/09273948.2018.1562080
9. Cheng HC, Pan RH, Yeh HJ, et al. Ambient air pollution and the risk of central retinal artery occlusion. Ophthalmology. 2016;123(12):2603-2609. doi:10.1016/j.ophtha.2016.08.046
10. Chua SYL, Warwick A, Peto T, et al. Association of ambient air pollution with age-related macular degeneration and retinal thickness in UK Biobank. Br J Ophthalmol. 2022;106(5):705-711. doi:10.1136/bjophthalmol-2020-316218
11. Tan H, Pan S, Zhong Z, Su G, Kijlstra A, Yang P. Association between Fine Particulate Air Pollution and the Onset of Uveitis in Mainland China. Ocul Immunol Inflamm. 2022;30(7-8):1810-1815. doi:10.1080/09273948.2021.1960381
12. Wu Y, Zhang S, Qian SE, et al. Ambient air pollution associated with incidence and dynamic progression of type 2 diabetes: a trajectory analysis of a population-based cohort. BMC Med. 2022;20(1):375. doi:10.1186/s12916-022-02573-0
13. Zhang HW, Lin CW, Kok VC, et al. Incidence of retinal vein occlusion with long-term exposure to ambient air pollution. PLoS One. 2019;14(9):e0222895. doi:10.1371/journal.pone.0222895
14. Auger N, Rhéaume MA, Bilodeau-Bertrand M, Tang T, Kosatsky T. Climate and the eye: case-crossover analysis of retinal detachment after exposure to ambient heat. Environ Res. 2017;157:103-109. doi:10.1016/j.envres.2017.05.017
15. Regulation (EU) 2024/573 of the European Parliament and of the Council of 7 February 2024 on fluorinated greenhouse gases, amending Directive (EU) 2019/1937 and repealing Regulation (EU) No 517/2014 (Text with EEA relevance). Official Journal of the European Union. 2024;L 2024/573:1-116. Accessed September 17, 2025. https://eur-lex.europa.eu/legal-content/EN/ALL/?uri=CELEX:32024R0573
16. American Academy of Ophthalmology. Sustainability and Ophthalmology. Accessed October 27, 2025. https://eyewiki.org/Sustainability_and_Ophthalmology
17. Bascom Palmer Eye Institute. Vitrectomy. Images. 2007: 1-10.
18. New Vision Eye Center. What to know about vitrectomy. March 13, 2025. Accessed October 27, 2025. https://www.newvisioneyecenter.com/blog/what-to-know-about-vitrectomy/
19. Vejar M, California Air Resources Board, personal communication, September 2025.
20. Chiang TT, McClintic S, et al. Comparison of retinal detachment repair outcomes using 20% sulfahexafluoride (SF6) vs air tamponade in pars plana vitrectomy surgery with or without scleral buckle. Presented at: American Society of Retina Specialists (ASRS) annual meeting; July 31, 2025; Long Beach, California.
21. Govers BM, Lamers MPM, Klevering BJ, Keijser S. Air versus fluorinated gas tamponades in pars plana vitrectomy treatment for primary rhegmatogenous retinal detachment. Acta Ophthalmol. 2022;100(8):e1600-e1605. doi:10.1111/aos.15144
22. Tetsumoto A, Imai H, Hayashida M, et al. The comparison of the surgical outcome of 27-gauge pars plana vitrectomy for primary rhegmatogenous retinal detachment between air and SF6 gas tamponade. Eye (Lond). 2020;34(2):299-306. doi:10.1038/s41433-019-0726-2
23. Uemura A, Mihara N, Yamakiri K, Santo K, Hamada T, Sakamoto, T. Air versus sulfer hexafluoride gas tamponade in vitrectomy for uncomplicated retinal detachment with inferior breaks. Retina. 2022;42(7):1262-1267. doi:10.1097/IAE.0000000000003470
24. Teh BL, Toh S, Williamson TH, Obara B, Guillemaut JY, Steel DH. Reducing the use of fluorinated gases in vitreoretinal surgery. Eye (Lond). 2024;38(2):229-232. doi:10.1038/s41433-023-02639-0
25. Moussa G, Ch’ng SW, Park DY, et al. Environmental Effect of Fluorinated Gases in Vitreoretinal Surgery: A Multicenter Study of 4,877 Patients. Am J Ophthalmol. 2022;235:271-279. doi:10.1016/j.ajo.2021.09.020
26. US Food and Drug Administration. Unifeye/Unipexy gas delivery system directions for use. October 31, 2023. Accessed October 27, 2025. https://www.accessdata.fda.gov/cdrh_docs/pdf23/P230012C.pdf