ABSTRACT
Mental retardation [MR] is a congenital or early onset lifelong impairment of cognitive adaptive functioning or daily living skills. It is a serious and lifelong disability that places heavy demands on society and the health system. The prevalence of visual and ocular disorders in children with MR is high and can influence sensory-motor development and learning ability. Assessment of the genetic and epidemiologic aspects of mental retardation and clarifying the ocular and visual problems among mentally disabled children. A cross-sectional hospital based study was conducted, through a period of two years, included 190 children under 18 years of age with mild to profound intellectual disabilities who were diagnosed among 480 cases referred to the Genetic clinic, Research Institute of Ophthalmology for genetic diagnosis and counseling. The definition of MR and the criteria for diagnosis were adopted from the World Health Organization [WHO] classification. The etiology of MR was specified by obtaining information about the personal and family history that included a three generation pedigree analysis, with special attention to the presence of similar cases, thorough clinical examination including complete neurological evaluation, chromosomal and other investigative studies. Ophthalmologic examination included visual acuity testing, ocular motility and examination of the external eye and anterior segment; cycloplegic refraction and fundus examination. One hundred and ninety patients representing 39.6% of the total examined cases in two years were classified etiologically into 6 groups. Specific causes were found in 161 cases [84.7%] and the etiology was unknown in 15.3% of children. Metabolic and chromosomal disorders comprised the most common etiological problems of the examined mentally retarded children in this study. The percentage of mild, moderate, severe and profound MR was 67.5%, 26%, 5.8% and 0.7%, respectively. Family history was positive in 34.7% of patients and autosomal recessive inheritance was the commonest mode of transmission [48.4%] that reflects the high percentage of consanguineous marriages among Egyptians. Microscopically visible chromosomal anomalies of intellectually disabled patients included 25 numerical and 11 structural aberrations. Errors of refraction and strabismus were the most common in children with chromosomal disorders [24.7%] and [28.1%] respectively. While the highest percentage of optic atrophy, retinal dystrophy, microphthalmia, cataract and corneal opacities were diagnosed in children with metabolic disorders representing 76.2%, 93.3%-, 38.5%, 50% and 80% of cases diagnosed in all categories respectively. In this study, metabolic and chromosomal disorders represented the most common etiological problems among the examined mentally retarded children with the highest proportion of specific ocular and visual problems represented among them to the extent that the eye could be considered as a window for their diagnosis. In most cases, diagnosis will assist families in understanding the condition, its prognosis and recurrence risks; more epidemiological studies have to be undertaken to determine the magnitude of the problem and its pattern of distribution in our country. The results also emphasize the need for establishing an efficient system to provide regular ophthalmic care for children with mental retardation