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Re: Multiple prenatal ultrasound scans and ocular development: 20‐year follow‐up of a randomised, controlled trial. Ultrasound in Obstetrics & Gynaecology 2014; 44:166–70. Forward H, Yazar S, Hewitt AW, Khan J, Mountain JM, Pesudovs K et al.

How do sonographers answer the question: Is ultrasound safe? It can be difficult to answer this question when there are few large-scale, long-term prospective studies that demonstrate the safety (or otherwise) of ultrasound scanning. This article by Forward et al. (2014) provides sonographers with some armoury to reassure their obstetric patients of the safety of ultrasound. The study investigates the impact of multiple prenatal scans on ocular development. This is pertinent because, as the author’s state, the developing lens is particularly vulnerable to intrauterine insult. This was a randomised study of two groups of pregnant women: one group (regular) who underwent one ultrasound scan at 18weeks of gestation and one group (intensive) who underwent ultrasound scans (including Doppler flow studies) at 18, 24, 28, 34 and 38weeks of gestation. After 20 years, 571 liveborns from the regular group, and 563 liveborns from the intensive group returned for ophthalmic examinations. Comparative data is presented for vision tests and refractive error, anterior ocular biometry, optic disc measurements and intraocular pressure. There were no significant differences between each group for any parameters, except for intraocular pressure, where the intraocular pressure of liveborns from the regular group was slightly less that for liveborns from the intensive group (p=0.034). The authors believe that the difference of 0.42mmHg, while statistically significant, has minimal clinical significance. The results indicate that the more frequent ultrasound examinations did not have an adverse effect on adult vision. These findings of no adverse effects on vision because of prenatal