Congenital malformation of the eye is an important cause of childhood blindness. We had 29.47% mothers with a history of night blindness during pregnancy, which is suggestive of hypovitaminosis A. Many clinical studies have covered congenital malformation of the eye and its relationship with hypovitaminosis A. Many experimental studies have suggested that hypovitaminosis and folic acid deficiencies in mother leads to congenital malformations of the eye.
Mastereo-de-las et al. have reported that mice exposed to a folic acid-deficient diet demonstrated numerous macroscopic eye anomalies, such as anophthalmia and microphthalmia. Microscopically too, the eye was the most affected organ (43.7% of the fetuses) .
Yomai et al. have documented that several putative genetic and environmental causes are associated with microphthalmia and anophthalmia, including vitamin A deficiency .
Bhattacharrji et al. and Millemann et al. have stated that the major anatomical causes of visual loss amongst 93 of the 258 patients (36.1%) were congenital anomalies (anophthalmos and microphthalmos) .
Horneby asserted the presence of epidemiological and laboratory evidence supporting a hypothesis of genetic (recessive) predisposition to the teratogenic effects of mild-to-moderate maternal vitamin A deficiency during pregnancy. This fact may explain the high prevalence of congenital eye anomalies in certain Asian countries where maternal deficiency of the vitamin is common and consanguineous marriages are popular. Besides, other congenital malformations commonly found in association with ocular coloboma (e.g. Esophageal fistulae and heart defects in CHARGE association) might also be related to the deficiency .
The results revealed that 43% of the parents were consanguineous, 19% had a positive family history, and that the frequency of coloboma was the highest in the second-born children. Eleven (16%) mothers had a history of night blindness while they were pregnant with the affected child, 7 (8%) had consumed medication during the first trimester (abortifacients in two cases), 3% had reported fever in the first trimester, and 11 (13%) had exposure to agricultural chemicals .
According to Ward et al., during embryogenesis, information encoded in the genome is translated into cell proliferation, morphogenesis, and early stages of differentiation. Embryonic pattern arises from the spatial and temporal regulation and coordination of these events. The vitamin A (retinol) derivative, retinoic acid (RA), is essential for normal development. Mammalian embryos are protected against vitamin A deficiency by maternal retinoid homeostasis until the stored retinoids fall to very low levels. Retinol binding protein, which is synthesized in the yolk sac placenta of rodent embryos and in the syncytiotrophoblast of the human placenta, is imperative for the embryo to access retinol. Synthesis and metabolism of RA may involve cytoplasmic binding proteins, but the observation that mutants lacking these proteins are normal or near-normal suggests that they are not essential. Severe congenital vitamin A deficiency results in a spectrum of malformations, including defects of the eyes, lungs, cardiovascular system, and urogenital system .
Many other studies have also reported similar findings either in clinical or in animal studies [10–16].