The dioptric difference between the accommodative stimulus and the accommodative response, where the eye over-accommodates for a near target. It may cause blurred vision at near due to excessive accommodation. Potential causes include accommodative spasm and uncorrected myopia. Treatment options involve reducing accommodative demand through minus lenses at near or vision therapy to improve accommodative […]
zone of clear single binocular vision
The region bounded by the maximum limits of accommodation and vergence over which an individual can maintain clear, single binocular vision. It represents the range of viewing distances where the eyes can simultaneously focus and align on an object while avoiding blur or diplopia. The ZCSBV is measured clinically by determining the extremes of convergence and accommodation that can be evoked while retaining fusion.
zyl
Abbreviation of zylonite, an early celluloid (cellulose-nitrate) plastic prized for its mirror polish yet infamous for igniting with heat. The nickname now covers most “plastic” frames, almost all milled from safer, plant-based cellulose acetate that is light, vividly dye-able, and easily heat-adjusted around 120 °C for fitting.