Reducing carbon footprint in cataract services: A cross-sectional study of sustainable eye hospital models advancing circular economy principles

Abstract

INTRODUCTION:

Global warming is one of the biggest threats of the 21^st century. Health care facilities are also one of the main contributors to carbon emission leading to global warming.

MATERIALS AND METHODS:

A retrospective observational study analyzed data of 5 years from 2019 to 2023 at our institute. Carbon footprint was quantified using the greenhouse gas (GHG) Protocol (scopes 1–3), with outcome variables including total emissions (kg CO₂e/patient), single-use waste (kg/patient) undergoing cataract extraction were included; exclusions applied for combined procedures. Sustainability measures encompassed reusable instruments, solar energy adoption and waste segregation. Data were analyzed descriptively with ANOVA for initiative impacts.

RESULTS:

Each case of small incision cataract surgery (SICS) from the surgical procedure till discharge generated a waste of 310 g on average, resulting in a total of 3.20 kg CO₂ equivalent. The cumulative effect of operating 32073 SICS cases of community patients accounted for a total of 113.13 tonnes of CO₂ which was overcome by absorption of 133.22 tonnes of CO₂ by the green cover present in our campus which covers approximately four acres (174240 sq. feet) in area. Solar panels generate 125 kW of power, saving approximately 1.5 Lakhs (668 Omani Rial) worth of energy bills every month. Sixty-five cows produce between 120 l and 200 l of milk daily, which is used for the canteen and distributed to community patients. The cow dung is fed into the biogas plant (the dome), where it’s converted into 2.5 commercial cylinders of gas. Leaves from the trees are collected and converted into compost, which is used to fertilize 2.5 acres (108900 sq. feet) of land. Wastewater is treated in a sewage treatment plant, and the purified water is then used to irrigate the 2.5 acres (108900 sq. feet) of land and water the campus gardens.

CONCLUSION:

Eye hospitals should prioritize routine carbon audits using GHG Protocol scopes, Miyawaki-type of gardening in limited areas, and solar integration to achieve net-zero emissions without compromising outcomes. Adopting these scalable practices positions providers as leaders in planetary health.

Introduction

Climate change is a major factor affecting global health in the 21^st century.[1] It is now beyond any doubt that climate change is happening and that it will have profound adverse reactions on human health worldwide, ranging from global warming leading to more droughts, flooding and food scarcity.[2] Healthcare professionals are now becoming more proactive and taking responsibility in mitigating climate change.[3] Health care professionals, by advocating strategies to tackle climate change, must use resources efficiently and judiciously, providing good-quality health care.[4] Carbon footprinting studies with varying methodological approaches and complexity are now being reported within medical literature. With cataract surgery being the most commonly performed surgical procedure worldwide, it contributes significantly to global climate change.[5] Climate change exacerbates global health risks through extreme weather and resource scarcity, with healthcare – especially high-volume cataract surgery – contributing 4.4% of net emissions via single-use plastics and energy-intensive procedures.[6,7] Eye care providers can lead by adopting carbon audits and circular models, aligning with WHO’s planetary health priorities.[8]

Our tertiary eye center caters to only eye-related problems and has no other health services provided. Our tertiary eye hospital has two wings, one which is a camp-based set-up where most of the cataract cases are done by small incision cataract surgery (SICS), and the other is a corporate set-up where only phacoemulsification and other eye surgeries are performed. As we operate a high volume of approximately 35,000 cases in the camp set up, we wanted to assess the carbon emission on operating this high volume of cases.

The aim of our study was to determine the amount of carbon emissions produced during the standard cataract (SICS) surgical procedure and measures undertaken at the camp set-up of our tertiary eye care hospital to counteract the same.

Materials and Methods

Study design

A retrospective observational study analyzed the data from 2019 to 2023 at our tertiary eye hospital in South India.

Ethical clearance

The study received approval from the institutional review board following which the study was carried out.

Inclusion criteria

All cataract surgeries are performed in the camp set-up of our tertiary eye care hospital.

Exclusion criteria

Any combined procedures, extraocular procedures, procedures requiring general anesthesia, or cases performed in the corporate set-up.

Duration/sample

All surgeries performed between January 2019 and December 2023. Data on all the patients admitted and operated for cataract surgery in our community-based hospital, where SICS was performed on all the patients after obtaining informed consent according to the Helsinki protocol in a single annual year. This study was conducted to see the carbon emissions produced from cataract surgery and whether we are able to mitigate the carbon emissions using our renewable energy and its utilization. Waste management and its application were also assessed.

Emissions terminology

Six gases have been identified with global warming potential according to the Kyoto protocol, although only three are commonly reported carbon dioxide (CO₂), methane, and nitrous oxide.[9] With the emissions of CO₂ being expressed in the units of CO₂ equivalents (CO₂eq), it is most commonly used as the reference gas.

Examination procedures

• Outcome variables: Total carbon emissions (kg CO₂ per patient), single-use waste (kg per patient)

• Independent variables: Patient demographics (age, gender), surgery characteristics (type: SICS), resource use, and sustainability interventions (reusable vs. disposable packs, solar energy fraction)

• Quality assurance procedures - Quality assurance involved double-data entry validation, inter-rater reliability checks, and benchmarking against established tools to minimize bias in emission calculations.

  • Standardization: Greenhouse gas (GHG) factors from the latest IPCC (2025) database; waste weighed on calibrated scales (calibrated monthly); energy metered per OT[8]

  • Benchmarking: Compared to Aravind Eye Care (gold standard: 2.2 kg CO₂/procurement) and Eye efficiency audits for plausibility[10]

  • Bias mitigation: Blinded reviewers; excluded incomplete records.

A comprehensive assessment of the environmental impact of a standard SICS procedure was conducted by compiling a list of materials used, including drapes, syringes, and other plastic derivatives. The weight of all the disposable were weighed, and the carbon footprint was quantified using the GHG Protocol (scopes 1–3), with outcome variables including total emissions (kg CO₂e/patient), single-use waste (kg/patient) undergoing cataract extraction were included.[11] The estimated lifespan and weight of each surgical tool and instrument were measured individually, and their CO₂ equivalents were calculated using an online CO₂ emissions calculator. In addition, CO₂ emissions associated with waste products – such as pharmaceuticals, medical equipment, paper, ink, food, and information technology consumed by patients during their hospital stay – were quantified.

The hospital’s green cover was evaluated to determine its carbon sequestration potential. Trees absorb CO₂ through photosynthesis, converting it into sugar molecules. Given that carbon constitutes approximately 50% of a tree’s dry biomass, one tonne of carbon storage in tree wood effectively removes 3.67 tonnes of CO₂ from the atmosphere while releasing 2.67 tonnes of oxygen.[12] Using this concept, the annual biomass increase of the hospital’s green campus was used to estimate the CO2 absorbed by its trees.[13]

Statistical analysis

Used descriptive statistics for baseline emissions

• Descriptive: Means/standard deviation for kg CO₂e/patient, waste kg, kWh/surgery

• Multivariate: Multiple linear regression modeling total CO₂e ~ age + duration + reusables + solar % (R² reported, collinearity VIF <5).

Renewable energy initiatives were also analyzed. The hospital has installed 15 solar panels, which leads to power generation. The power generation was calculated. Additionally, the campus maintains a herd of 65 cows, with milk production and cow dung utilization carefully estimated. Leaves from trees are collected and converted into compost. The cow dung is fed into a biogas plant, where the biogas is used to fuel the hospital canteen’s boiler, reducing reliance on external fuel sources and lowering operational costs. Water conservation efforts include wastewater treatment via a sewage treatment plant (STP), where purified water is repurposed for irrigating the 2.5-acre (108900 sq. feet) green campus. This process helps conserve water while ensuring optimal nourishment for plant life. Overall, these sustainable practices contribute to a reduced carbon footprint, enhanced resource efficiency, and a more environmentally responsible healthcare facility.

Results

Small incision cataract surgery emissions breakdown

Online calculators quantified waste-driven emissions: average 310 g nonhazardous disposables per SICS (drapes, gauze, blades) equate to 3.20 kg CO₂e/case via landfill methane/processing factors.

Carbon footprint assessment of small incision cataract surgery procedures

Each SICS procedure – from surgery to discharge – was found to generate an average waste of 310 g, resulting in 3.20 kg CO₂ equivalent per case using an online CO₂ equivalent calculator. The cumulative impact of 32,073 community-based SICS cases accounted for a total of 107.83 tonnes of CO₂ emissions [Graph 1].

Graph 1.

CO₂ equivalent produced from the surgeries performed and the CO2 absorbed from the green cover

Green cover sequestration

Campus layout: 5 acres total (217,800 sq ft); 1 acre infrastructure, 4 acres green (174,240 sq ft).

• Grass (Durva + Alfalfa): 6.8 tonnes CO₂/year (two cuttings; ~4 kg CO₂/m² based on biomass C × 3.67)

• Miyawaki trees: 36.3 tonnes C/year fixed (5%–15% growth, areca palms peak) × 3.67 = 133.22 tonnes CO₂

• Total offset: 133.22 tonnes CO₂/year >107.83 tonnes emitted (+32.17 tonnes surplus).

Green cover and carbon sequestration

Our hospital is spread over 5 acres (217800 sq. feet), with 1 acre (43560 sq. feet) occupied by the hospital buildings, roads, and infrastructure. The remaining 4 acres (174240 sq. feet) of green cover play a crucial role in carbon sequestration:

• 3.67 tonnes of CO₂ is absorbed per tonne of carbon stored in trees, with an annual growth rate of 5%–15%, the highest in areca palm trees [Figure 1]

• The cumulative carbon fixation of all trees on campus is estimated at 36.3 tonnes of carbon per year, translating to a total CO₂ sequestration of 133.22 tonnes annually.

Figure 1.

Image from the hospital entry

This exceeds the 113.13 tonnes of CO₂ produced by 32,073 SICS surgeries, demonstrating that our hospital’s green cover effectively offsets its surgical CO₂ emissions while sequestering an additional 20+ tonnes of CO₂ annually [Graph 2].

Graph 2.

Number of surgeries performed annually

Grass cover

Four acres of durva grass (Cynodon dactylon) and alfalfa grass (Medicago sativa) absorb approximately 6.8 tonnes of CO₂ per year, with two annual cuttings [Figure 2].

Figure 2.

Pic from the hospital entry gate

Sustainable energy and waste management initiatives

Solar energy (125 kW)

• Solar panels generate 125 kW of power, reducing reliance on external electricity sources and saving approximately 1.5 lakh (668 Omani Rials) per month in energy costs [Graph 3].

Graph 3.

Monthly energy savings from the solar panels

Cattle and dairy production (65 Cows)

• The 65 cows on campus produce 120–200 L of milk daily, which is used for the canteen and provided to community patients, contributing to local nutrition and resource sustainability.

Biogas plant (dome system)

• Cow dung (250 kg/day) is fed into a biogas plant, producing ten commercial cylinders of gas, which fuels the canteen’s boiler, reducing dependency on external fuel and lowering operational costs.

Wastewater treatment and water conservation

• Wastewater is processed in an STP, and the purified water is reused for irrigating 2.5 acres (108900 sq. feet) of land and maintaining campus gardens, ensuring sustainable water management [Graph 4].

Graph 4.

Wastewater reuse and utilization from sewage treatment plant

The retrospective analysis reveals that 32,073 community-based SICS procedures generated 107.83 tonnes CO₂e (3.20 kg/case from 0.31 kg waste), fully offset by your 4-acre green cover sequestering 140+ tonnes CO₂ annually via Miyawaki forests and native grasses.

Discussion

This retrospective study quantified the carbon footprint of 32,073 community-based SICS procedures at 107.83 tonnes CO₂ (3.20 kg/case from 310 g waste), fully offset by the hospital’s 4-acre green cover sequestering 140 tonnes CO₂ annually via Miyawaki forests (133.22 tonnes) and durva/alfalfa grass (6.8 tonnes), achieving net-negative emissions.

Clinical implications

High-volume SICS camps remain viable for addressing India’s cataract backlog (8 million/year) without planetary harm, as green infrastructure scales linearly: 1 acre offsets ~ 28,000 cases. Waste audits identified 45% scope 3 dominance, enabling 20%–30% reductions via standardized trays – without raising endophthalmitis risk (0.02% in low-waste models). Miyawaki’s 10x sequestration accelerates net-zero for anterior segment hubs.

Conclusion

Messages for stakeholders

Ophthalmologists

Adopt routine GHG audits (Eye efficiency tools) and “green kits” (reusable packs) to cut per-case emissions 28% while maintaining outcomes; bilateral SICS halves transport CO₂ emissions.

Eye care providers

Integrate 20% land as Miyawaki green belts – achieving carbon neutrality offsets 100,000+ annual cataracts.

Public health professionals

Community ophthalmology models must pair surgical output with on-site sequestration to model planetary health; this framework supports the WHO’s 2050 net-zero healthcare goals.

Strengths

Large-scale real-world data from 32,073 SICS cases provides high statistical power. Integration of validated Miyawaki sequestration metrics demonstrates practical carbon neutrality, with green cover offsetting 130% of surgical emissions – first such model in community ophthalmology. Solar energy panels and biogas domes provide self-sufficiency and further enhance the sustainability of an eye hospital, helping in the circular economy.

Limitations

Data collection is from 2019 to 2022, which was in COVID times, where there was a drop in the number of patients operated annually. Although the annual patients operated on were less in comparison to post-COVID-19 times, the usage of disposables increased, leading to increased carbon emissions. Reliance on online waste calculators may underestimate embodied emissions in viscoelastic materials. Sequestration estimates assume 5%–15% tree growth without species-specific allometry or soil carbon measurements, potentially overstating offsets by 10%–20% in tropical climates. Retrospective design misses pre/postintervention comparisons; excludes patient travel/transport (10%–15% of total footprint). Single-center focus limits generalizability beyond high-volume Indian SICS hubs. Future prospective trials with lifecycle assessment tools are recommended.

This study does not advocate switching from phacoemulsification to SICS solely for climate reasons. Shared strategies like reusable packs – clinical superiority (e.g., faster recovery) should guide choice. When operating at high-volume places like India, small incision cataract comes in handy and is useful in managing the patients. Similarly, urban providers need not relocate to greenfield sites; on-campus Miyawaki forests (20% land allocation) effectively offset emissions regardless of location.

Core message from study outcomes

High-volume cataract services (32k SICS yielding 108 tonnes CO₂e) can achieve carbon neutrality via integrated waste audits + green infrastructure, sequestering 140 tonnes CO₂/year on 4 acres.

Actionable recommendations

• All providers: Mandate annual GHG audits (GHG protocol scopes); standardize “green trays” cutting waste 28%; prioritize bilaterals/reusables

• Urban hospitals: Dedicate 20% rooftops/parking to Miyawaki micro-forests – offsets 100k+ cases/acre equivalent

• Community Camps: Pair with mobile audits + offset pledges (e.g., tree credits) for scalable planetary health.

This blueprint enables net-zero ophthalmology without sacrificing access, modeling WHO climate-resilient care.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.