[Evaluation of grating visual acuity development in normal infants].

OBJECTIVE

To assess the grating visual acuity of Chinese normal infants from 5 to 24 months, evaluate the development of grating visual acuity in infants.

METHODS

The Teller acuity card(TM) II (Stero-Optical Company, America) was used to assess the grating visual acuity of 244 infants aged from 5 to 24 months, who met the eligible criteria. Binocular visual acuity and monocular visual acuity were both assessed. They were divided into 19 groups according to their age sequence from 5 to 24 months. Average binocular and monocular visual acuity of every group were recorded and calculated. The relationship between visual acuity and age were analyzed. The practicality and possibility of the application for the Teller acuity card in infants were assessed.

RESULTS

Binocular visual acuity was obtained in 241 infants (98.77%). Monocular visual acuity from both eyes was completed in 89.2% infants. All the tests can be finished in 2 to 5 minutes. The average of binocular visual acuities of the 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 24 months separately was: 0.17, 0.21, 0.22, 0.23, 0.23, 0.25, 0.26, 0.30, 0.33, 0.32, 0.37, 0.39, 0.42, 0.47, 0.56, 0.60, 0.83. The average of monocular visual acuities separately was: 0.15, 0.19, 0.19, 0.20, 0.20, 0.21, 0.21, 0.27, 0.23, 0.26, 0.24, 0.35, 0.26, 0.41, 0.40, 0.56, 0.80. The binocular visual acuity was slightly higher than the monocular visual acuity. The difference was less than one octave. The intraocular acuity difference was less than one octave. There were no significant differences between left and right eyes. Visual acuity of the infants aged form 5 to 14 months increased slowly from 5.1 to 9.6cpd, about 1 octave. There was an increase started from 15 months. Everyone who was reached 24 months got a visual acuity of 26cpd (snellen = 0.833), closed to the adult level. Compared to the visual acuity of 12 months age, 1.5 octaves were increased.

CONCLUSIONS

TAC is useful and practical for age norms of visual acuity of infants in clinical and vision research. Visual acuity increases progressively with age. The development of visual acuity shows a different speed in different age period. Monocular visual acuity is slightly lower than binocular visual acuity. There is a balanced visual development of both eyes.