AIM: To study the relationship between positive and negative relative accommodation capabilities, far and near horizonal heterophoria, accommodative facility and youth myopia development.

METHODS: In the case of informed consent, the 266 cases of University new students, which the average age was 18.8±0.8 years, were selected. According to refractive state, the volunteers were divided into 5 groups: emmetropic group(n=29), low myopia group(n=118), moderate myopia group(n=82), high myopia group(n=37), anisometropia group(n=26). The anisometropia group was not included in the objects of study. The positive and negative relative accommodation force were measured by the phoropter integrated refractometer; far and near phoria were measured by Von Graefe; adjustment flexibility was measured by ±2.00D butterfly mirror. The eye movement parameters of different groups were statistically analyzed.

RESULTS: The positive relative accommodation force of emmetropic group was 4.87±1.47D; low, medium, high myopia group were respectively 2.36±1.21D, 2.92±1.40D, 2.86±1.81D. The PRA of different myopia group were significantly lower compared with the emmetropic group, the difference was statistically significant(P<0.05); the regulation flexible degrees of emmetropia group had no significant difference compared with different myopia groups(P>0.05); far and near level phoria had no significant differences between the emmetropia and myopia group(P>0.05), there was a statistically significant difference between the low myopia and high myopia group(P<0.05).

CONCLUSION: Myopia positive relative accommodation decreased significantly may be one cause of youth myopia by causing accommodation insufficiency and forming hyperopic defocus. There was no relationship between negative adjustment relative force, adjustment flexibility, far, near phoria and youth myopia.