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Ridley medal lecture – David F. Chang

David F. Chang, MD, Clinical Professor, University of California, San Francisco, will deliver the Ridley Medal lecture at the 38th ESCRS Congress

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Posted: Friday, September 4, 2020

David F. Chang, MD

It is a tremendous privilege to be presenting the Ridley lecture this year. Although this is one of the greatest individual honours that I’ve ever received, I wanted to use my lecture to highlight what I consider to be the greatest team of cataract surgeons – those at the Aravind Eye Care System in Southern India – and some of the most important lessons that they’ve taught us during the last two decades.

Aravind is a network of more than 10 regional centres with six main large hospitals. My collaboration with their cataract surgeons started with my first visit there in 2003. They have become the global model for reducing the backlog of cataract blindness in underserved societies, by using revenue from paying patients to subsidise cataract surgery at little or no cost to the indigent (which accounts for 60% of their total surgical volume). This is the first and most important lesson – that we can use this type of cost-recovery model to reduce and eventually eliminate global cataract blindness.

At the centre of their approach is the use of sutureless, manual, small-incision cataract surgery (MSICS). This is an extracapsular procedure where an undivided nucleus can be manually extracted through a funnel-shaped 8mm scleral tunnel incision that does not require suturing. A non-foldable PMMA IOL, costing less than $5.00 USD, is implanted through this incision. To restore vision to as many indigent cataract patients as possible, surgery is performed in an assembly line fashion to maximise efficiency, while minimising cost, and yet maintaining high-quality outcomes.

Compared to MSICS, phacoemulsification is much more expensive in terms of capital investment, maintenance and repair, and consumables per case. Furthermore, we showed in a study at the Madurai Aravind hospital that the complication rate was much higher with phaco than MSICS when the surgeon has less experience. In addition, indigent populations have a huge burden of ultra-brunescent and mature cataracts, which increases the risk of complications with phaco. Therefore in eyes with very advanced and complicated cataracts, MSICS would probably be safer than phaco for many surgeons. In fact, I use MSICS in my own practice for the most advanced cataracts that I encounter in the United States.

Another important innovation of the Aravind group is that they found a way of putting a square edge on to PMMA lenses at a cost of $1 USD. Posterior capsule opacification (PCO) is an inconvenience for patients in the West since it can be easily treated with a YAG-laser capsulotomy. However, for patients living in rural areas in developing countries, limited healthcare access makes PCO one of the leading causes of visual impairment. We performed a nine-year, long-term study that showed that when patients underwent implantation of a square-edged PMMA IOL in one eye and a round-edged PMMA IOL in the other, the eye with the square-edged lens had dramatically less PCO compared to the fellow eye. Aravind is one of the largest suppliers of IOLs for developing countries, and as a result of this study, all of their PMMA IOLs now have a square edge – which is lesson #3.

A fourth compelling lesson from Aravind is that intracameral moxifloxacin is safe and effective for endophthalmitis prophylaxis. ESCRS sponsored a landmark study with intracameral cefuroxime but vancomycin was the most commonly used antibiotic for intraocular prophylaxis in the US, until it was determined to be the cause of HORV. We authored the largest, single-institution study of intracameral antibiotic prophylaxis, comparing the endophthalmitis rates with and without intracameral moxifloxacin in two million consecutive cataract surgeries at Aravind. The endophthalmitis rate dropped from 0.07% in those who didn’t receive moxifloxacin compared to only 0.02% among those who did. Lacking a large randomised trial, this type of big data registry study offers the best available evidence in my opinion.

The last compelling lesson is that our innumerable operating room regulations in the West mandating single-use of most of our supplies, pharmaceuticals, and devices may be of unproven benefit in reducing infection rates. In addition, they add significantly to the cost and carbon footprint of cataract surgery. Studies carried out of Aravind have shown that their carbon footprint for one phaco is 20 times lower than for one phaco in the UK. That is largely because Aravind re-uses devices, pharmaceuticals and supplies such as irrigating solution, IA tubing, metal blades and cannulas, and they don’t change gowns or gloves between cases. Their robust electronic data registry allows them to continually monitor their infection rates and outcomes and they have learned that re-using these supplies and devices does not affect the outcome. After adopting intraocular moxifloxacin routinely, their endophthalmitis rate is actually lower than that of the AAO IRIS registry (0.04%), but of course intraocular antibiotic prophylaxis is not used by many Americans due to lack of a commercially approved product.

David Chang was interviewed by Roibeard O’hEineachain, Contributing Editor, EuroTimes