Haptic perception of the horizontal by blind and low-vision individuals

We examined haptic perception of the horizontal in visually impaired people. Blind people (late blind and congenitally blind), persons with very low vision, and blindfolded sighted individuals felt raised-line drawings of jars at four angles. They had to demonstrate their understanding that water remains horizontal, despite jar tilt, by selecting the correct raised-line drawing given four choices. Low-vision subjects, with near perfect scores, performed significantly better than the other groups of subjects. While the late-blind and blindfolded sighted subjects performed slightly better than the congenitally blind participants, the difference between the late-blind and congenitally blind groups was nonsignificant. The performance of the congenitally blind subjects indicates that visual experience is not necessary for the development of an understanding that water level stays horizontal, given container tilt.

Visual disorders in children with brain lesions: 2. Visual impairment associated with cerebral palsy

Disorders of visual function are a common finding in children with cerebral palsy. In some cases they are secondary to ophthalmologic abnormalities such as cataract or retinopathy, but more often they are due to damage of the central visual pathway. We review the literature on the prevalence and distribution of visual abnormalities in children with cerebral palsy and their relation to cognitive, motor and emotional development.

[Septo-optic dysplasia (de Morsier syndrome)]

Septo-optic dysplasia (or de Morsier syndrome) is a congenital disorder characterised by anomalies in cerebral midline structures, optic nerve hypoplasia, and hormonal deficiencies. Diagnosis should be made early, due to the possibility of treating the hormonal disturbances. We describe here a case with decreased visual acuity, one-sided hemianopia, nystagmus und agenesis of the septum pellucidum and discuss the heterogeneous appearance of this syndrome. There are two theories regarding its pathogenesis. The first postulates simultaneous damage to both cerebral structures and optic nerve development around the 6th week of gestation, while the other favours secondary degeneration of optic nerve fibres due to a cerebral lesion.

Head and eye movements in children with low vision

BACKGROUND

Early childhood nystagmus may herald blindness, brain tumors, benign idiopathic motor nystagmus or spasmus nutans. Nystagmus unique to low vision was sought.

METHODS

Videotapes and head/ eye movements of 18 congenitally visually impaired subjects were analyzed.

RESULTS

Nystagmus of congenitally visually impaired subjects was characterized as small horizontal or vertical movements superimposed on larger oscillations. Small and large nystagmus movements were of pendular or jerk type. Slow-phase jerk nystagmus had increasing, constant and decreasing velocities. Fast-phase nystagmus changed direction periodically. Pendular nystagmus was out of phase and evolved to jerk nystagmus in two subjects. All subjects displayed head nodding, and one stabilized gaze with head movements.

CONCLUSION

Eye movement recordings allow characterization and differentiation of subjects with nystagmus and low vision from other nystagmus forms.

Congenital and hereditary visual impairment in Greenland

Thirty-eight cases of congenital visual impairment (CVI) were reported in the Inuit population of Greenland over a period of 40 years (1950-1989), corresponding to a frequency of 86 per 100,000 live born children. The two most common causes of blindness were optic atrophy and cerebral visual impairment due to brain disorders of various etiologies. This finding is in accordance with recently published data from the Nordic countries. On the other hand, retinopathy of prematurity and congenital cataract were rare causes of CVI in Greenland. Fifteen out of the 38 cases had unknown etiology. Genetic disorders accounted for 7/38 of the cases. A separate examination of registered cases with probable genetic visual impairment, irrespective of birth year, disclosed 25 patients. New mutations seemed to be the most reasonable explanation for isolated cases of aniridia, lens ectopia, and Down syndrome, while inbreeding was a possible contributory factor in a few autosomal recessive conditions.

Visual characteristics of low vision children

A retrospective survey of pediatric clinical files from the Kooyong Low Vision Clinic (LVC) showed that the major causes of low vision were congenital or inherited conditions and most children had 6/60 (20/200) or better distance acuities. A classroom evaluation of these children showed that overall, the clinically determined visual acuity corresponded with classroom performance. A high rate of use of prescribed low vision aids was found, and a reading evaluation on a standardized test showed poor performance with respect to reading speed and comprehension, but almost all the children had adequate reading accuracy. Considering the importance of reading in education, greater emphasis on reading evaluations in routine low vision examinations is recommended.