9 EyeWorld Asia-Pacific | December 2024 About The Physicians David Chang, MD | Altos Eye Physicians, California Graham Barrett, MD | Australia Relevant Disclosures Chang: RxSight, Perfect Lens, J&J Vision, Alcon, and Carl Zeiss Barrett: Alcon, Haag Streit, Rayner, Zeiss and Bausch & Lomb But even in these more challenging cases, as published by Dr Liangpin Li and coauthors in 2023, 80% or more of eyes can be predicted within 0.5 D following Lasik using modern formulae. These results are not dissimilar to the LAL studies and are compatible with my own experience. Using the measured posterior cornea option in the True K formulae equivalent to the True K TK, further improves the prediction accuracy in eyes with a history of previous refractive surgery. 100 80 60 40 20 0 Shammas Haigis-L M-Masket Masket True K NH True K IOL Formulae Outcomes - Post Refractive 56% 46% 38% 26% 82% 74% Comparative analysis of IOL power calculations in postoperative refractive surgery patients: A theoretical surgical model for FS-LASIK and SMILE procedures. Source: Graham Barrett, MD Liangpin Li, Liyun Yuan, Kun Yang, Yanan Wu, Xia Hua, Yan Wang and Xiaoyong Yuan BMC Opthalmology volume 23, Article number: 416 (2023) The outcomes achievable with the different pathways are therefore similar but the additional effort required with the adjustable IOL is far greater. The LAL requires patients to wear protective sunglasses for several weeks and at least 3 additional visits for adjustment and final lock-in with a light delivery device. Not least repeated refraction, which is inherently variable compared to the precision of biometry, is required with additional personnel – this is truly disruptive technology! Optimum results with biometry do require more than a single instrument, optimising the ocular surface measuring the posterior cornea and occasionally repeating measurements. The effort required to implement these simple measures is straightforward and within reach of all practices. The additional expense to incorporate the light adjustable lens far exceeds that required for accurate biometry. Biometers and topographers are an essential part of any practice that performs cataract surgery but implanting the adjustable IOL requires the additional purchase of a light delivery device and the cost of the additional time and effort is also costly. The additional costs for a patient are also considerable and estimated to be in the range of US$5,000 per eye. I do recognise that many patients are willing to pay and the ability for surgeons to charge patients more as a premium option may be one of the reasons this lens is more popular in the USA than other countries. Finally, in regard to safety there are potential complications related to the use of UV light at 650 nm. 49% of patients experience a red tint to their vision or erythropsia and a small percentage (1.8%) have experienced a Tritan anomaly in their colour perception. Postoperatively, the minimum pupil diameter required for complete lock-in is greater than 6.5 mm and this is not always achievable. There are anecdotal reports of unexpected outcomes after LAL implantation and lock-in. Failure to wear protective glasses can be problematic as in this case report in Ophthalmology of a patient who failed to wear protective glasses and required explantation of the light adjustable IOL. Undiagnosed previous herpetic keratitis can be reactivated and there are a number of medications susceptible to photosensitization that must be avoided. So use of the light adjustable IOL does entail some risk compared to the use of formulae. To summarise the comparison of which pathway you should choose for perfection, comparing the light adjustable lenses vs formulae. I would regard the outcomes as equivalent but consideration of LAL is reasonable in post refractive eyes. The additional effort required for using an adjustable light IOL is considerable and the logistics are problematic compared to formulae. Routine use of a light adjustable IOL is definitely considered cost effective in some health delivery systems. And there are certain safety considerations and precautions required. I would like to conclude with an ancient Chinese proverb. It is far better to “Measure twice and cut once” in woodwork and I would suggest the same applies in cataract surgery. I would consider accurate biometry and formulae a preferable pathway to precision and perfection. FEATURE Pathways to Precision and Perfection – Light Adjustable Lens (LAL) vs. IOL Formulae
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