Vergence adaptation in esotropia.

Vergence adaptation and anomalous fusional movements have been used by strabismics to overcome prism. There has been controversy in the literature regarding the nature of the vergence responses by esotropes to prism, i.e., fusional, avoidance of fusion, and/or anomalous fusion. This paper reviews the various types of movements made by esotropes to prism and attempts to explain the mechanism. In addition, the relation of these vergence movements to prismatic, orthoptic, and surgical correction is discussed.

Comparison of fusional ranges measured by Risley prisms, vectograms, and computer orthopter.

Maximum base-in (BI) and base-out (BO) fusion vergence ranges were measured in 38 normal subjects using 3 different clinical procedures. These procedures used different instruments, instructions, and vergence stimuli (Risley prisms, vectograms, and video-displayed contour and random dot stereograms) presented at 50.8 cm. Test-retest measures, which were taken on each test for each subject, indicated high positive correlations between test and retest measures for most vergence tests. Paired inter-test correlations among five different tests varied as a function of the pairing as well as type of measure taken (BI, BO, break, recovery). It was concluded that different methods of measuring vergence provide different kinds of information and such tests may not be used interchangeably.

Proptosis and increase of intraocular pressure in voluntary lid fissure widening.

The eyeball proptoses about 0.5 mM and increases in intraocular pressure (IOP) about 2 mmHg with voluntary widening of the lid fissure. The findings probably result from the retraction of the upper lid into the orbit, thus increasing the volume of orbit contents and forcing the eyeball forward. Decrease in IOP with repeated tonometry may result, in part, from decay of the increased pressure induced by lid fissure widening.