RESUMO
OBJECTIVE: Young guinea pigs are susceptible to become myopic during form deprivation. They can also quickly recover from the myopia after removal of the form deprivation. This study investigated whether mature guinea pigs are sensitive to form deprivation and its refractive recovery from deprivation myopia. METHODS: It was an experimental study. Thirty-nine guinea pigs were arranged to 3 groups according to age. Group 1: 9-week old (n = 18). Group 2: 12-week old (n = 10). Group 3: 15-week old (n = 11). All the animals were performed refraction measurement prior to the experiment, then wore a facemask that covered one randomly assigned eye for three weeks. The masks were then removed and refraction was measured in both eyes immediately, 2 and 7 days after. RESULTS: After form deprivation, the refraction of the MFD (monocular form deprivation) eyes shifted to myopia, which had significant difference compared to the unmasked eye in all the groups (t = -5.691, -2.203, -2.760; P < 0.05), the relative myopia compared to the unmasked eye in 9 weeks old animals were (-2.53 ± 1.89) D, 12 weeks old (-1.43 ± 1.57) D, 15 weeks old (-0.60 ± 1.48) D. There was significant difference between 9 weeks old animals and 15 weeks old animal in the refractive error right after the form deprivation (F = 2.823, P < 0.05). And the distribution of refractive error tended to lower degree of myopia as the guinea pigs grew older. None of the three groups showed significant reduction in relative refractive error during the recovery, but a trend of recovery was found in 9 weeks old animals. CONCLUSIONS: The guinea pigs are sensitive to the form deprivation even when they are sexual mature, but both the susceptibility and the ability of recovery decrease as they grow older but in different patterns. The ability of recovery in short term (7 days) diminishes when guinea pig is older than 12 weeks while the sensitivity to form deprivation last until 15 w.