Abstract
The growing environmental impact from healthcare sector necessitates the adoption of sustainable strategies to reuse, recycle, reduce waste, lower carbon emissions, etc. In ophthalmology, surgical waste poses a significant environmental challenge, particularly due to the high volume of surgeries, along with single-use instruments, packaging materials and disposable surgical supplies. Examples of practical strategies to reduce surgical waste include adopting reusable surgical instruments when safe and feasible, minimizing unnecessary packaging and optimizing operating room protocols, e.g., multidose topical drops on multiple patients. An education regarding sustainability for medical personnel can further decrease waste production in the long term. Collaboration between healthcare providers, manufacturers and policymakers is essential to developing and integrating sustainability into ophthalmic practice. By implementing these strategies, ophthalmologists can contribute to a more environmentally responsible healthcare system without compromising patient safety.
Introduction
Climate change, one of the greatest health threats of this century, is becoming an emergency issue to be dealt with for sustainability, good health and well-being. It contributes to rising temperature, heatwaves, wildfires, floods, storms and hurricanes, which have intensified and increased in severity over the past few years. These environmental disasters directly affect public heath, for example, by causing respiratory diseases, heatstroke, infectious disease, and stress, or indirectly, by making it difficult to access healthcare or leading to shortages of medical services in affected areas, and facilitating transmission of the pathogen through ecosystem modifications and changes in human behavior. Countries or regions with weak health infrastructure are the most vulnerable, particularly low-income and middle-income countries (LMICs). Thus, further delay in addressing the climate change will significantly increase the risk to both the physical and mental health of the global population.
The primary cause of the climate change is an increase in greenhouse gases (GHGs) in the atmosphere, particularly carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O). These gases trap heat from the sun, creating a “greenhouse effect” that warms the planet. While GHGs are naturally present in the atmosphere, human activities, e.g., burning of fossil fuels and industrial processes, have dramatically increased their concentrations, leading to global warming and eventually, climate change. A term “carbon footprint” or “carbon emission” is widely used in environmental studies and refers to the total GHG emissions calculated over a full life cycle of a product or process. The gaseous emissions are then converted to a unit “carbon dioxide equivalent (CO 2 -eq)” to quantify the environmental impact of the carbon footprint. Although the CO 2 -eq of each product or process may not be directly comparable across the studies due to the variations in estimation methods, it remains a widely used research outcome in most publications. Many studies also translate CO 2 -eq into other relatable terms to engage the readers, e.g., the equivalent distance driven by a car, the amount of petrol burn or the carbon emission from an international flight. Some studies may report waste in terms of “mass of waste (g or kg)”. However, for consistency, CO 2 -eq was primarily selected as the unit to demonstrate an environmental impact in this review.
According to a study in 2019 by Health Care Without Harm, an international nongovernmental organization that works on healthcare worldwide to create ecological sustainability, and ARUP, a global collective of designers, engineers and consultants who dedicate to sustainable development, the healthcare sector was responsible for 4.4 % of global GHG emission (2 gigatons of CO 2 -eq), which resulting from energy consumption, transportation, product manufacturing, usage and disposal of products. Majority of these emission (71 %) originate from the healthcare supply chain, including the production, transport and disposal of goods and services, such as pharmaceuticals, chemicals, food and agricultural products, medical devices, hospital equipment and instruments. A country in our Asia-Pacific region, China, is among the top three countries with the highest GHG emission in the healthcare sector. These top three countries are the US, China and the European Union, which collectively account for 56 % of the world’s total healthcare-related climate footprint. Since every country will experience the effects of climate change, it is our shared responsibility to take an action in reducing the GHGs emissions and make our community more sustainable.
This review aims to highlight the importance of the climate change and the strategies to mitigate these effects as an ophthalmologist. We have summarized our content into four major topics: 1) the environmental impacts from ophthalmic procedures, 2) ophthalmologists’ attitudes toward the climate change, 3) strategies or interventions and 4) potential concerns. Additionally, a real-world example of sustainable practices from the authors’ institution is included to provide the readers a model on the attempt to reduce environmental impact while maintaining high-quality of ophthalmic care.
Ophthalmic procedures and environmental impact
Aside from generation and distribution of electricity, gas and heat or cooling, which accounted for 40 % of the total carbon footprint emission, the operational facilities were the second-largest source of emission. Operating rooms (ORs) alone contributed to 13 % of the carbon emission and approximately 30–70 % of hospital waste. Thus, the operational procedures and medical supplies are significant sources of GHG emissions and have become an area of interest in numerous publications across various medical specialties.
In ophthalmology, our surgeries rank as the highest in volume in medicine. A cataract surgery itself is considered the most commonly performed ophthalmic surgery worldwide, with more than 26 million surgeries conducted annually with an increasing number. The carbon footprint of a single cataract surgery varies, ranging from a high of 181.9 kg CO 2 -eq in a university hospital in the UK to a low of approximately 6 kg CO 2 -eq in tertiary care centers in India. Several observational studies have reported carbon footprint ranging from 41.0 kg to 151.9 kg CO 2 -eq per single phacoemulsification, with the majority of the emissions attributed to disposable materials, patient and staff travel, and medical equipment. Additionally, the unused pharmaceutical products during phacoemulsification contribute to financial and environmental burdens. A study in 2019 by Tauber et al. conducted at four surgical sites in the US found that approximately two-thirds (65.7 % by volume) of eyedrops were unused. The disposal of unused or partially used topical eyedrops or ointments resulted in an estimated cost of $150 per case and contributed to between 23,000 and 105,000 tons of CO 2 -eq emissions annually in the US.
In vitreoretinal surgery, a greater number of instruments are used compared to cataract surgery, resulting in a higher CO 2 -eq per procedure. The gases used in tamponade the retina (sulphur hexafluoride [SF 6 ], hexafluoroethane [C 2 F 6 ] and octafluoropropane [C 3 F 8 ]) are also among the most potent GHGs. Their atmospheric lifetimes are more than ten times longer than CO 2 , and their heat absorption potentials are thousands times greater . Compared to C 2 F 6 , procedures using C 3 F 8 and SF 6 generate 1.9 and 4.4 times more CO 2 -eq, respectively. SF 6 is also one of the six highly potent GHGs regulated under the Kyoto Protocol, an international treaty adopted in 1997 in Kyoto, Japan, under the United Nations Framework Convention on Climate Change which aims to reduce GHG emissions and combats global warming. The type of gas used varies depending on the surgical indications and institutional practices; however, a study from India reported that C 3 F 8 was used in 70 % of vitreoretinal surgeries. As a result, carbon footprint of vitreoretinal surgeries varies by procedure type, ranging from 32.0 kg CO 2 -eq for macular hole repair to 60.0 kg CO 2 -eq for rhegmatogenous retinal detachment surgery.
Another common ophthalmic procedure is an intravitreal injection (IVI). In 2016, over 20 million IVIs were performed worldwide, and the number is expected to increase each year. Reports from Ireland and New Zealand estimated that the carbon emissions associated with a single IVI, excluding the anti-vascular endothelial growth factor (anti-VEGF) agent, were 13.68–14.1 kg CO 2 -eq, with patient travel being a major source (40–77 %) of carbon emissions. The CO 2 -eq from anti-VEGF agents also varies among agents due to the variation of the procurement (production, distribution, consumption, packaging and disposal of an item), e.g., 16.5–20 kg CO 2 -eq for bevacizumab, 320 kg CO 2 -eq for ranibizumab and 375–423 kg CO 2 -eq for aflibercept. Packaging of IVI medications, especially brand-name drugs, additionally generates more considerable waste.
Surgical waste from other ophthalmic procedures, e.g., trabeculectomy and surgical drainage device surgery, has also been reported. The solid waste generated per case was at least equal to or greater than that from phacoemulsification. One study reported approximately 0.5 kg of solid waste from trabeculectomy and 0.4 kg from surgical drainage device surgery in India, whereas in the US, trabeculectomy produced 1.4 kg of waste, which was 3.7 times more than in India.
Attitudes of ophthalmologists and surgeons toward climate change
A recent survey conducted by the European Society of Cataract and Refractive Surgeons (ESCRS) with 458 respondents (77 % practicing in Europe) revealed that 99 % were concerned about global warming and climate change, with 72 % feeling “very concerned”. Regarding OR waste, 92 % believed it was excessive, with 63 % rating it as “far too much”, and 96 % agreed that surgical waste should be reduced. Most respondents cited restrictions on reuse imposed by manufacturers and regulatory bodies as a major driver of this waste. There was a strong desire to have more reusable options for instruments, devices and supplies. These findings are comparable with an earlier 2020 survey of 1300 North American cataract surgeons and nurses using the identical questionnaire. In that survey, 93 % believed that OR waste was excessive and should be reduced, 78 % supported reusing more supplies, 90 % expressed concerns about global warming, and 87 % wanted medical societies to advocate for reducing the surgical carbon footprint. Additionally, more than 90 % of the respondents believed that profit motives, reducing liability and unconcern on the carbon footprint drive manufacturers to produce more single-use products. Over 90 % also expressed a desire for more reusable products and greater regulatory and manufacturer discretion regarding when and which products can be safely reused. Given a comparable cost, 79 % of surgeons preferred reusable over disposable instruments. The survey also highlighted a strong willingness to reuse many surgical supplies, as well as topical and intraocular medications. 29
The respondents from both surveys ranked similar factors influencing their willingness to reuse supplies and medications on multiple patients. However, more ESCRS surgeons considered the risk of endophthalmitis to be a major concern (64 % vs 48 %), while fewer ESCRS surgeons were strongly influenced by cost savings (47 % vs 63 %), efficiency (49 % vs 63 %) and malpractice liability (41 % vs 51 %). Additionally, ESCRS surgeons were more likely to cite reducing environmental footprint as a key factor for using reprocessed single-use supplies and devices (79 % vs 58 %). These similarities suggested concerns about sustainability among ophthalmic personnel in the western world.
Another recent survey in 2022 conducted in the US with 219 surgeons found that 90 % agreed or strongly agreed that waste of sterile surgical items is an issue, and 95 % agreed or strongly agreed to a willingness to change the operating room workflow to reduce waste. These results suggest that focusing on minimizing OR waste, particularly by eliminating unnecessary waste of sterile surgical supplies, may be a key to sustainability in healthcare.
Strategies to make a surgery more sustainable
Sustainable strategies have been advocated in healthcare sectors, especially in the approaches related to the OR. A potential intervention was developed based on the concept of “5 Rs” of sustainability: refuse, reduce, reuse, repurpose and recycle. A review in 2023 included 23 unique OR quality improvement initiatives, which aimed to reduce the environmental impact and costs, showed that 39.3 % of the total 28 interventions was categorized as “refuse”, 28.6 % as “reduce”, 10.7 % as “reuse” and 21.4 % as “recycle”. An intervention on education to reduce regulated medical waste showed the greatest potential financial cost savings ($694,141 per year) with 30 % reduction in regulated medical waste. Another review in cataract surgery divided the interventions into a decision tree for use by an individual surgeon, which included four domains: 1) advocacy and education, 2) pharmaceuticals, 3) processes and 4) supplies and waste. The authors concluded that certain interventions may be safe, cost-effective and environmentally friendly, e.g., dispensing medications home to patients after surgery, multi-dosing appropriate medications, training staff to properly sort medical waste, reducing the number of supplies used during surgery and implementing immediate sequential bilateral cataract surgery where clinically appropriate. As there were many interventions, we selected some of the practical interventions and discussed below.
Multi-dose topical medication for multiple patients
Drug waste significantly increases both costs and environmental impact in the healthcare sector. In the previously mentioned study by Tauber et al. conducted at four surgical sites in the US, eyedrops (65.7 % by volume) were more unused compared to injections (24.8 %) or systemic medications (59.9 %). On average, 83,070 of 183,304 ml per month (45.3 %) of pharmaceuticals were unused across all sites after phacoemulsification, with an estimated cost of approximately $195,200 per site. Thus, topical drug is more likely to generate waste than the others. The Ophthalmic Instrument Cleaning and Sterilization (OICS) Task Force, comprising specialists from American Society of Cataract and Refractive Surgery (ASCRS), American Academy of Ophthalmology (AAO), American Glaucoma Society (AGS) and Outpatient Ophthalmic Surgery Society (OOSS), addressed the importance of the unnecessary waste and provided three recommendations regarding the safe and responsible use of perioperative topical medications:
- 1.
Topical drugs in multi-dose containers can be used on multiple patients in surgical facilities if proper guidelines are followed. This recommendation is based on the evidence that a proper reuse of eye medication bottles for multiple patients does not contribute to increased rates of endophthalmitis after cataract surgery.
- 2.
Topical drugs in multi-dose containers can be used until the manufacturer’s labeled date of expiration if proper guidelines are followed. Notably, the 28-day expiration policy applies to injectable medication, not to topical eye medications.
- 3.
When applicable, patients should be able to bring their partially used medication home for postoperative use.
However, multi-dose bottles whose tips become contaminated should be immediately discarded.
For the proper administration of topical eyedrops, ophthalmic personnel should wash their hands before and after administering eyedrops to patients’ eyes. The tamper-proof seal on unopened eyedrops should be removed completely before use, and when the dropper bottle cap is removed, it should be placed on a clean surface with the inside facing up to avoid contamination. After administering the eyedrops, the cap should be replaced in a sterile manner and screwed down tightly to prevent leaking and contamination.
Sterilization and reusing surgical instruments
The important factors that could lower carbon footprint are reuse of surgical materials and efficient autoclave settings. While disposable items offer convenience and are perceived as associated with lower risk of infection, they also contribute to environmental impact and hidden burdens, e.g., costs in procurement, stock check or inventory management, storage and disposal of packaging. A significant portion of carbon emissions originates from the manufacturing and distribution of single-use surgical supplies in high-income countries (HICs).
A concern about infection of reusable items has been long-lasting, but evidence does not always support the notion that single-use items are safer. Studies from 11 regional eye hospitals comprising the Aravind Eye Care System (AECS) in southern India, reported an endophthalmitis rate of 0.02 % in 314,638 cataract surgeries with intracameral moxifloxacin. At AECS, all eyes received topical and intracameral antibiotic prophylaxis but many disposable supplies, e.g., surgical gloves, gowns, irrigation/aspiration (I/A) tubings, irrigation bottles, blades, and cannulas, are routinely reused to reduce cost and waste. Multiple patients simultaneously have cataract surgery in a single operating room that contains multiple surgical tables and teams. Operating surgeons and scrub nurses do not rescrub, regown or reglove between consecutive cases. Despite these multiple reused items, the endophthalmitis rates after cataract surgery in AECS are lower than 0.04 % rate reported in the US. Another study from AECS involving 3241 cataract surgeries showed no bacterial or fungal growth in extensive microbiological cultures of immediate use steam sterilization (IUSS) sterilized ophthalmic surgical instruments (surgical cannulas, syringes, phacoemulsification and coaxial/bimanual I/A tips, phacoemulsification and I/A sleeves) and surgical products that were reused across multiple patients without sterilization (phacoemulsification tubings/handpieces, coaxial I/A handpieces, residual-unused fluid from balanced salt solution bags after being used for multiple patients). No case of endophthalmitis was observed over a six-week follow-up period.
These findings suggest that certain practices mandated by regulatory and licensing agencies might not have a proven benefit and may not justify the significantly higher costs and carbon footprint they entail. If comprehensive reuse and sterilization protocols, such as those at AECS, are not feasible due to policy or other constraints, adopting specific measures—such as using reusable cassettes in phacoemulsification—has demonstrated reduction in plastic consumption (75.3 %), decreased storage volume (67.7 %) and enhanced efficiency and cost savings (16.9 % cost saving).
OICS also published evidence-based recommendations regarding the cleaning and sterilization of intraocular instrumentations. General administrative principles, cleaning intraocular instruments, ultrasonic cleaning, reuse of phaco tips, etc. were discussed in this paper. The risk of toxic anterior segment syndrome from routine use of enzymatic detergent was mentioned because of the microscopic residues are difficult to eliminate from intraocular instrumentation. If enzymatic detergent has to be used for any reason, instructions for proper dilution and disposal of cleaning solutions should be followed. They also supported the safety of common short-cycle instrument processing practices for sequential same-day anterior segment surgery, and the future studies evaluating on OR protocols that may increase cost, waste and carbon footprint, without any actual safety benefit.
Education and advocacy
Although literature regarding to education and advocacy specific to ophthalmology is limited, many educational and advocacy interventions, in general, carry minimal risks and can be applied across various specialties and procedures. Significant majority of physicians are already concerned about global warming and climate change and believe that OR waste is excessive and should be reduced. Education was also proposed to be one of the most potent intervention with cost saving and high environmental impact. Thus, implementing the education on surgical waste or climate change-related issues for medical personnel may have a great benefit and contribute to long-term sustainability in healthcare.
Within the institution, clinicians can engage in educational activities, e.g., grand rounds or training sessions with their peers and colleagues, to discuss sustainability, climate change and proper waste sorting. Advocating for the inclusion of formal coursework on climate and health in medical and nursing school curricula, as well as in continuing education programs, can better prepare clinicians for future work. Training operating room staff on sterilization, proper waste sorting and recycling protocols can have positive environmental and financial impacts. Clinicians can also advocate for institutional policy changes, such as investing in renewable energy sources, green building design and carbon offsets.
This advocacy could extend beyond health system practices and policies to manufacturers, organizations, local and federal governments. Collaboration between clinicians or departments and the industry can be effective in promoting sustainability. For example, a group of ophthalmology theater teams in UK teaching hospitals, together with supplier companies, created an “Eco-packs” project which could save 675 kg of waste and 350 kg of CO 2 -eq annually for the cataract surgery. An international consortium, Medical Society Consortium on Climate and Health, was also established in 2017 and includes many major medical associations, such as the AAO. The consortium aims to inform policymakers and the public about the harmful health effects of climate change and to reduce the healthcare system’s carbon footprint.
Finally, national policy can have a significant impact. For instance, the National Health Service (NHS) in the UK, the largest employer of healthcare personnel in Europe, has set a target to become the world’s first net-zero healthcare system by 2040. Healthcare sectors in the UK then played vital roles directly through clinical work and indirectly through areas such as procurement.
The potential concerns
Risks of infection, transmitting infection and endophthalmitis
When considering the use of reusable materials and recycling strategies in ophthalmology, a primary concern is the potential risk of infection, including cross-contamination between patients and endophthalmitis. Although these risks are low, they can have severe consequences and must be balanced against costs, environmental impact and overall population health. For example, with a concern using multi-dose topical drops on multiple patients, one study in the UK showed that a contamination rate per drop application was 2.5 %. The risk of cross-contamination with coagulase-negative staphylococcus would be between 1:400 and 1:80 if the bottle was reused once or six times, respectively. Eliminating this risk to zero by using disposable droppers only once costs between £2.75 and £4.6 million per year and generates between 6.85 and 11.42 more tons of paper waste and between 12.69 and 21.15 more tons of plastic waste than reusing the disposable dropper.
Another study showed that cost savings to both patients ($283.85) and the facility ($330.91) per cataract case were significant with a policy and procedural approach to the use of multi-dose eyedrops on multiple patients. Conversely, a study from Germany reported a 2 % contamination rate (Staphylococcus spp.) of the dropper tip in 245 samples and recommended the use of single-dose eyedrops in preoperative and intraoperative contexts. However, as exposure to staphylococcus is not necessarily lead to infection, determining acceptable risk levels for a given cost can help maximize both cost-effectiveness and patient safety. The evidence also suggests that limited durations of use, proper handling of multi-dose droppers and regular training of administering staff can minimize contamination risk, reduce waste and lower environmental and financial costs before, during and after cataract surgery.
While AECS in India applying reused instruments reported an endophthalmitis rate of 0.02 % after cataract surgery, which is lower than the rate of 0.04 % in the US, another study from Thailand showed an endophthalmitis incidence of 0.10 % (13 eyes) in 12,989 cases of recycled pars plana vitrectomy (PPV) devices. Of which, 3 eyes (0.11 %) using 20-gauge vitrectomy, 8 eyes (0.09 %) using 23-gauge vitrectomy and 2 eyes (0.18 %) using 25-gauge vitrectomy. These endophthalmitis rates from PPV with reused instrument are comparable with the rates mentioned in the literature, which ranged 0.02–0.15 % in 20-gauge vitrectomy and 0.03–1.55 % in 25-gauge transconjunctival sutureless vitrectomy. These findings suggest that the risk of infection from reused instruments is low and may be achieved by proper guidelines, standardized sterilization and thorough training of medical personnel and OR staff. This risk of infection, therefore, should not be overwhelming the environmental harm and costs associated with single-use instruments.
Potential cost-effectiveness
From certain perspectives, the cost of a sustainable option may appear to be higher than that of less environmentally friendly alternatives. For example, in cataract surgery, phacoemulsification requires more instruments than those with manual small-incision cataract surgery whereas the former is 1.4–4.7 times more expensive and generates more CO 2 -eq. However, in general, phacoemulsification may still be a preferable option for cataract surgery due to lower postoperative astigmatism and complications, which may require more additional costs to treat and also patient transportation costs for more frequent follow-up, etc. Femtosecond laser-assisted cataract surgery, on the other hand, was less cost-effective compared to the conventional phacoemulsification.
In IVI, since many injections over the years are generally required, most of the emission came from patient travels and the agent used (bevacizumab 16.5 kg CO 2 -eq vs aflibercept 375 kg CO 2 -eq). A longer acting drug (if possible, with divided dosage or multi-dose packaging) and simultaneous bilateral eye injection (if needed) could reduce the number of clinic visits or transportation, thereby effectively lowering the carbon emission.
Contradictions with national regulatory agency or policy
For a similar procedure, HICs are more likely to generate greater waste and GHGs emission than the LMICs. For example, 0.5 kg vs 1.4 kg of solid waste were generated from trabeculectomy, and 0.25 kg vs 2.3–3.9 kg of waste were generated from phacoemulsification in India and the US, respectively. However, numerous practices, e.g., reusing disposable items or dividing intravitreal medication into multiple individual usage, may be prohibited or challenging in licensed surgical facility or clinic in many HICs. For example, the US Food and Drug Administration (FDA) issued a guidance document in 2000 concerning the reprocessing of single-use medical devices by third parties or hospitals. The FDA states that hospitals and third-party reprocessors will be considered “manufacturers” and will be regulated similarly. A repurposed single-use device must meet the same regulatory requirements as when it was initially manufactured. National organizations in the US such as OICS, which include experts from ASCRS, AAO and OOSS, later published evidence-based recommendations regarding the cleaning and sterilization of intraocular instrumentations to balance the safety, cost and environmental impact. However, an adherence to these guidelines does not guarantee compliance with any legal or regulatory standards, nor Medicare or other third-party payer reimbursement. Individual physicians must make independent judgments regarding what is appropriate for the patient’s best interest and circumstances. Surgeons, physicians or even researchers in HICs may then struggle to adopt sustainable interventions due to conflicts with existing policies. Manufacturers also face regulatory restrictions and liability concerns, including potential lawsuits for defective products. These require them to promote disposable items to ensure product safety and comply with regulations, to avoid penalties and reputational damage. Thus, an evidence-based approach to clinical safety that incorporates environmental considerations is essential. Health investment and national policy must be retooled to support decarbonization, for example, a net-zero policy of NHS. If all of the health sectors—individual healthcare providers, healthcare facilities, ministries of health, international development agencies, healthcare organizations and industries— all take action toward this goal, meaningful progress can be achieved.
Artificial intelligence in healthcare: a double-edged sword?
Artificial intelligence (AI) has the potential to reduce healthcare-related GHG emissions, particularly through autonomous AI, where medical decisions are made without human oversight. A 2022 study found that autonomous AI reduced GHG emissions by 80 % compared to those generated during an in-person specialist encounter. However, AI technologies can also have a significant environmental impact due to their high energy consumption, material requirements and resource demands. As the healthcare sector continues to adopt AI, it is crucial to balance its benefits with environmental responsibility. By implementing best practices for sustainable AI—such as using renewable energy sources for AI computations, minimizing the carbon footprint of data centers, creating more compact and computationally efficient AI models and investing in the research and development of eco-friendly AI—healthcare organizations can leverage AI’s transformative potential while actively contributing to environmental sustainability.
A real-world example
At Chiang Mai University Hospital, Chiang Mai, Thailand, sustainability principles have already been incorporated into cataract, vitreoretinal and other surgeries. Multidose preoperative drops, e.g., anesthetic or dilating agents, are used on multiple patients by using a standard “no touch” technique when instilling one drop into each eye of the patients. Reusable surgical gowns, drapes and covers are made from fabric that adheres to the hospital’s sterilization protocols ( Fig. 1 ). Phacoemulsification and I/A tips, sleeves, tubing and handpieces are sterilized and reused. Vitrectomy sets and other instruments (e.g., intraocular lens injector, forceps, micro-scissor and silicone oil injector) are also sterilized for reuse and packed with minimal packaging materials as possible ( Fig. 2 ). Intraocular gas is procured in large bottles and divided into individual doses for each procedure ( Fig. 3 ). For example, 4–5 ml of 100 % SF₆ is withdrawn into a 20-ml syringe and then diluted to a 20 % concentration using a sterile technique. Additionally, some ophthalmic instruments are custom-made, e.g., an iris retractor fashioned from Prolene 4-0 sutures ( Fig. 4 ).
