Chiasmal coefficient of flash and pattern visual evoked potentials for detection of chiasmal misrouting in albinism

The diagnosis of albinism can be confirmed by electrophysiological examination, when chiasmal misrouting can be demonstrated. The present study describes a quantitative analysis method for this purpose. A chiasmal coefficient (CC) was calculated by correlating the differential potential over left and right hemisphere, when stimulating left versus right eye. This CC will be negative in albinism and positive in normal individuals. VEPs were recorded in 20 control subjects, four children with congenital motor nystagmus and six children with albinism. In up to 25% of the controls the CC was negative, when using flash VEP. However, with pattern VEP all had a positive CC. All children with albinism had a negative CC. Three of the four patients with congenital motor nystagmus had a positive CC, and one child had a small negative value with flash stimulation. In conclusion, determination of CC is a valuable and objective analysis method for electrophysiological determination of chiasmal misrouting. The method is relatively simple and only needs two electrode tracings. One should be aware of false-positive results when using flash stimulation. Whenever possible pattern stimulation should be used

Cyclic esotropia:V-pattern and upshoot in adduction

Three patients with cyclic esotropia are described. In all upshoot in adduction developed in the, course of the disease, and in two of the patients a V-pattern was noticed. In two of these cases the strabismus was addresses by surgery on the horizontal muscles only. In the other case both inferior oblique muscles were also weakened. In all patients the V-pattern and upshoot in adduction diminished or completely resolved. Excyclotorsion, caused by loss of fusion may be the explanation for the development of V-pattern and upshoot in adduction in cyclic esotropia. Restoration of fusion by surgery on the horizontal muscles may then be enough to eliminate the vertical incommitance.</p

Cyclic esotropia: V-pattern and upshoot in adduction

Three patients with cyclic esotropia are described. In all upshoot in adduction developed in the, course of the disease, and in two of the patients a V-pattern was noticed. In two of these cases the strabismus was addresses by surgery on the horizontal muscles only. In the other case both inferior oblique muscles were also weakened. In all patients the V-pattern and upshoot in adduction diminished or completely resolved. Excyclotorsion, caused by loss of fusion may be the explanation for the development of V-pattern and upshoot in adduction in cyclic esotropia. Restoration of fusion by surgery on the horizontal muscles may then be enough to eliminate the vertical incommitance

The polaroid suppression test in a pediatric population with ophthalmologic disorders

Purpose: The Polaroid suppression test (PST) is a new method for early detection of amblyogenic factors by screening for suppression. The apparatus can elicit suppression with the use of Polaroid filters. The aim of the present study was to examine a population of children with known ophthalmologic disorders using the PST to determine the rate of false-negative results of the PST. Methods. Six hundred four children, varying in age between 3 and 15 years (mean, 7.9) were examined using the PST. Ophthalmologic disorders ranged from strabismus and amblyopia to refractive disorders. Results. Mean testing time for the PST was 43 seconds. The PST could not be administered to 34 children (5.6%); 443 children (73.3%) had abnormal results; and 127 children (22.2%) showed no suppression. The suppression in constant strabismus. was detected in almost all cases. The sensitivity for accommodative forms of strabismus was lower, but amblyopia was never missed in these cases. In children with normal eye alignment, only 2.7% with an interocular acuity difference of more than 0.1 logMAR had no suppression. Of all 119 children with clinical defined amblyopia, only 1 (0.8%) did not have suppression. Overall sensitivity of the PST for strabismus and/or abnormal interocular acuity difference was 96.2% and specificity was 41.1%. Conclusions: The PST has great potential as a visual screening tool in young children. Only few children with amblyogenic factors were missed. Thus, the test can differentiate those children at risk for amblyopia from normally sighted children. Because specificity is lower, all children showing suppression with the PST in a screening situation should have further examination by the health care worker before being referred to the ophthalmologist