Cortical visual impairment in children - A new challenge for the future?

The prevalence of visual impairment in children with multiple disabilities is high;[1-3] it has been found to be 10.5% in children with developmental disabilities.[3]

Visual impairment reported in children with multiple disabilities may be secondary to ocular defects such as uncorrected refractive errors,[134] cataract,[24] nystagmus,[2] retinopathy of prematurity (ROP),[23] optic nerve atrophy,[2-4] or oculomotor abnormalities, or on account of cerebral defects such as cortical visual impairment (CVI),[2-4] delayed visual maturation (DVM),[5] or nystagmus.[2467] Identification of the cause of visual impairment is very important, to arrive at a clinical diagnosis.

The current definition of cerebral or CVI includes all visual dysfunctions caused by damage to or malfunctioning of the retrochiasmatic visual pathways in the absence of damage to the anterior visual pathways, or any major ocular disease.[8]

Cortical visual impairment has been recognized as being one of the most important causes of bilateral blindness, in the United States.[9] It is emerging as an important cause of blindness in the developing world too, with increasing survival of children who suffer perinatal hypoxia. These developmentally delayed and Cortical visually impaired children may have a wide range of visual deficits. Several perceptive visual functions such as face recognition, object recognition, motion processing, visual memory, orientation, visual spatial perception, and simultaneous perception may be affected in these children. Studies, however, have not looked at all of them systematically.[8] Vernier acuity has been found to be more affected than grating acuity.[10] There is some evidence that dorsal stream / magnocellular pathway deficits may be more common in children with CVI.[11] Studies have reported the finding of periventricular leukomalacia (PVL) on magnetic resonance imaging (MRI) of the brain, as an important anatomic finding in children with CVI.[12]

Visual impairment occurs more frequently among children with multiple disabilities. These children can have a combination of motor, cognitive, and visual dysfunction. It is important for pediatricians and ophthalmologists to look for and recognize CVI as a cause of visual development delay and visual dysfunction in all children with risk factors for perinatal hypoxia, including difficult labor and delivery, twin pregnancy, prematurity, and low birth weight, especially in the low socioeconomic group of patients, with limited access to health care and so on.

Recognizing CVI is the first step toward rehabilitation and prevention. These children need modifications in the examination techniques to assess vision and visual dysfunction. Conventional vernier acuity measurements are often not possible or give an erroneous picture. It is important to record grating acuity, which helps in follow-up.[13] Often qualitative visual acuity testing methods have to be used, to supplement the quantitative visual acuity recording methods.[6] Tests to detect the various types of perceptive dysfunctions need to be developed. These tests need to be adapted, taught, and made available to the ophthalmologists in the developing world.

Prognosis for improvement of visual impairment in CVI has also been an area of much debate. Although earlier studies had suggested that prognosis remains poor, longitudinal studies have found results to the contrary, suggesting improvement with time. Prevention will involve early recognition of the risk factors. Rehabilitation methods may need to be tailor made to each child. Each child with CVI is likely to have its own unique visual and motor deficit, necessitating an individualized approach.