[Study of habitual and vegetal accommodative tonus in children with myopia and hyperopia]

The difference between primary and cycloplegic refraction is called habitual accommodative tonus. Vegetal Tonus corresponds to the accommodative rest and is determined by vegetal innervation balance of ciliary muscle. The purpose of the study was to develop the method for objective measurement of vegetal accommodative tonus according to its dark focus. We examined 31 children (62 eyes) aged from 5 till 16 years old. 36 eyes were low myopic, 10 eyes--low hyperopic, 10 eyes showed to have moderate and 6 eyes high hyperopia. The measurements were performed using binocular open-field autorefkeratometer (Grand Seiko WR-5100K) in a fashion developed by the authors. The results showed positive habitual accommodative tonus in all refractive anomalies. Vegetal accommodative tonus appeared to be positive in all eyes with low myopia and hyperopia. In eyes with moderate and high hyperopia the portion of negative vegetal accommodative tonus rises. Data revealed in the study can be of great importance for understanding of postnatal refractogenesis.