Background: Anophthalmia and microphthalmia are serious eye malformations which recently have been associated with exposure to Benomyl. Data on these malformations are scarce in the literature and reported prevalences at birth vary strongly.
Methods: Data from three large registers of congenital malformations were analysed and comprised 849 malformed infants based on close to 5.7 million births.
Results: This is the largest available epidemiological study on anophthalmia and microphthalmia. The prevalence at birth was 1.50 per 10,000, varying between 0.92 and 2.29 between registers but no varying significantly between races in the California register. The variation in rates was mainly due to different inclusion of chromosomally abnormal infants (mainly trisomy 13) and of infants with microphthalmia occurring with major non-eye malformations. On the other hand, rates of anophthalmia and isolated microphthalmia were similar. Other major non-eye malformations were found in 73% of infants without a known chromosome anomaly. The malformation was bilateral in 53-60% of infants except when microphthalmia existed without any other malformations when only 27% were bilateral. Sex distribution was normal, there was a slight excess of twins, and an increased risk at high maternal age.
Conclusions: In analytical studies searching for the cause of these malformations, it may be useful to restrict the analysis to infants with anophthalmia or isolated microphthalmia as the recording of such cases seems to be more reliable than of microphthalmia occurring with other malformations. The conclusions presented in the literature on the possible effect of Benomyl are partly based on data with apparent very incomplete ascertainment.