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From the editor

Reducing the environmental impact of cataract surgery

Sustainability versus safety: A tradeoff?

Mamalis, Nick MD

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Journal of Cataract & Refractive Surgery: January 2018 - Volume 44 - Issue 1 - p 1-2
doi: 10.1016/j.jcrs.2018.01.001
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“Waste not, want not.”

—Old proverb

Modern healthcare uses large quantities of resources and generates large quantities of waste. For example, the National Health Services are responsible for 5% of the United Kingdom’s greenhouse gases.1 Similarly, in the United States, the healthcare sector produces 10% of the total greenhouse gas and 9% of criteria air pollutants.2 The topic of the environmental impact of cataract surgery is something that has been rarely considered in ophthalmology. Thiel et al.3 performed an extensive waste and life-cycle assessment of phacoemulsification cataract surgery at 2 centers in the Aravind Eye Care System in southern India. They reported that a single cataract surgery using phacoemulsification in the United Kingdom releases the equivalent greenhouse gases of driving a passenger vehicle nearly 700 kilometers. They then carefully analyzed the system used at the Aravind Eye Care system and found that phacoemulsification surgery generated 0.25 kg of solid waste and approximately 6 kg of carbon dioxide–equivalent greenhouse gases (the same as driving a passenger vehicle approximately 25 kilometers). They concluded that if India’s ophthalmologists used the United Kingdom’s methods for phacoemulsification in cataract surgery, India alone would produce the same greenhouse gases as 250 000 passenger vehicles.

Equally important to the sustainability of cataract surgery as decreasing the environmental impact of cataract surgery is the issue of safety. In other words, is there a tradeoff between sustainability and safety? The Thiel et al. study3 found that the methods used in the Aravind system significantly reduced the environmental impact as well as costs associated with the surgical supplies and equipment used in the performance of phacoemulsification cataract surgery. More important, they found no significant issues with safety and that this decrease in waste generated with cataract surgery yielded comparable to better patient outcomes with less spending.

An area of potential savings of resources used in cataract surgery is the reuse of phacoemulsification tips for the removal of the lens nucleus. However, questions related to the reuse of phaco tips must be addressed. Cecchini et al.4 performed a study in which they assessed phacoemulsification tips in cataract surgery, comparing new unused tips with tips after a single use and then with tips after multiple uses. The tips were evaluated with X-ray photoemission spectroscopy and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy analysis and contact profilometry. The analyses were performed at the far end of the phacoemulsification tip. This study found that the used tips showed signs of wear at the end of the tip with some deposition of debris. They also found that the cutting edge appeared to be rounded and irregular. In addition, after surgery, there was an increase in the surface roughness. Chemical analysis of the tip showed some modification of the superficial alloy composition as well as some biologic debris that was deposited after surgery. The authors found that the changes were more remarkable after multiple surgical procedures. These authors concluded that used tips showed relevant signs of deterioration and deposition of biologic material, mostly involving the outer edge. They stated that the single use of disposable phaco tips seems to be highly advisable.

This issue of the journal contains a recent laboratory study evaluating the morphologic changes induced after multiple uses of different types of phacoemulsification tips in an ex vivo model by Tsaousis and coauthors (pages 91–97). This study was performed at the University of Utah’s Moran Eye Center as well as the Utah Nanofab Laboratory at the College of Engineering. Eight types of phaco tips from different manufacturers were evaluated using an identical experimental profile. Fresh porcine lens nuclei were soaked in neutral buffer formalin for various amounts of time in a standardized study model developed at Moran Eye Center to create uniformly hard lens nuclei that mimic human cataractous lens nuclei. The phaco tips in each group were then used to emulsify the porcine cataractous lenses, which were of moderate hardness, for 2 minutes using 100% continuous ultrasound power. This was chosen to represent the extreme of clinical use in a dense nucleus. Each tip evaluated in this study was used for 5 consecutive cycles to simulate clinical reuse in multiple cases. Scanning electron microscopy was used to evaluate the tips to detect any significant microscopic structural changes. In addition, in cases in which SEM detected significant amounts of deposits, energy-dispersive X-ray spectroscopy was performed to define the origin of the deposits. Furthermore, white-light interferometry was used to analyze the tips after SEM imaging to quantify the microscopic degree of roughness at the tips distal opening. White-light interferometry offers noncontact, high-precision 3-dimensional metrology of surface features.

Scanning electron microscopy evaluation of the phaco tips showed no abnormalities in the new unused tips, which acted as a control. The SEM images were taken at 3 areas of the phacoemulsification tip (ie, wrench, proximal, and distal edges) before the initial use. Corresponding areas of the tips were evaluated after the phacoemulsification cycles in corresponding areas and showed small deposits (possible tissue residues on different areas of the tip) with no significant structural changes, such as scratches, cracks, or breaks. There was no sign of micro stress fractures or fissuring in any of the tips evaluated. The tips did show areas of precipitated salt, likely from the balanced salt solution used. In addition, the tips had surface deposits of material (carbon-rich and oxygen-rich) that were consistent with the porcine lens tissue that had not been adequately washed off. White-light interferometry analysis of the surface roughness of the distal opening of the different reused tips after 5 phacoemulsification cycles showed a small increase in microscopic roughness. This study concluded that the ex vivo experimental simulations of heavy clinical reuse did not result in significant ultrastructural damage to the phacoemulsification tips. In addition, when the tips were subjected to identical experimental conditions in reuse, there was no ultrastructural difference in the durability or integrity of the phacoemulsification tips that were labeled for single use or for multiple uses.

One of the most important issues to be addressed in the reuse of phacoemulsification tips is to ensure that there is no compromise in patient safety involving the use of these tips for the removal of cataracts. The ex vivo experiments performed at the Utah Nanofab Laboratory showed that the reuse of phacoemulsification tips did not cause significant structural micro fractures, deformations, fissures, breakage, or failure as assessed using SEM analysis. This finding was consistent across different models and different manufacturers of the tips. In addition, this study specifically found no differences in durability between tips labeled as single use and tips labeled for up to 50 uses. No structural changes that would lead to a decrease in the cutting ability of the reused tips were noted. This model was very robust, using extreme settings of 100% continuous longitudinal phacoemulsification power that would simulate 10 minutes of continuous phacoemulsification at 20% power. Another important finding were the insignificant changes in the phaco tips’ surface roughness after the 5 ex vivo phaco cycles. The conclusions in the Tsaousis et al. study are quite different than those in the Cecchini et al.4 study. It is not clear whether the reported increased mean surface roughness in the used tips versus the new tips would be of clinical significance. As stated in the discussion of the paper, “We do not believe that their recommendation to adopt only single-use disposable phaco tips is based on meaningful clinical evidence. Considering the global prevalence of reusing phaco tips, such a sweeping recommendation should not be based purely on theoretical concerns extrapolated from ultrastructural surface changes of uncertain relevance.”

In conclusion, the reuse of phacoemulsification tips in the experimental model reported by Tsaousis et al. did not lead to significant structural damage or wear. Therefore, it is recommended that cataract surgeons be allowed discretion in terms of reusing phaco tips based on their best clinical observation and judgment. This would help reduce the higher cost associated with single-use phacoemulsification tips as well as possibly decrease the environmental impact associated with single-use phacoemulsification tips.

References

1. Sustainable Development Unit. Carbon Footprint Update for NHS in England 2015. January 2016, Sustainable Development Unit, Cambridge, UK, Available at: https://www.sduhealth.org.uk/documents/publications/2016/Carbon_Footprint_summary_NHS_update_2015_final_v2.pdf Accessed 8-1-2018
2. Eckelman MJ, Sherman J. Environmental impacts of the U.S. health care system and effects on public health. PLoS One. 11(6): 2016, e0157014, Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4900601/pdf/pone.0157014.pdf Accessed 8-1-2018
3. Thiel CL, Schehlein E, Ravilla T, Ravindran RD, Robin AL, Saeedi OJ, Schuman JS, Venkatesh R. Cataract surgery in environmental sustainability: waste and lifecycle assessment of phacoemulsification at a private healthcare facility. J Cataract Refract Surg. 2017;43:1391-1398.
4. Cecchini P, D’Aloisio R, Antonuccio M, Turco G, Bondino F, Magnano E, Di Nicola M, Tognetto D. Chemical and physical analysis of phaco tips surface before and after cataract surgery. J Cataract Refract Surg. 2017;43:1107-1114.
© 2018 by Lippincott Williams & Wilkins, Inc.