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The accommodative convergence/accommodation (AC/A) and near convergence/distance (NC/D) ratios in esotropia
1Clinic of Ophthalmology, Clinical Hospital of Rijeka, Croatia.
Introduction:
In esotropias, measurement of AC/A and NC/D ratios are important for exact classification and adequate therapy. We devised a table for the calculation of AC/A and NC/D ratios to facilitate their estimation.
Method:
For the assessment of AC/A ratio, we used the gradient method range 6 Dsph and for the NC/D ratio we used the heterophoria method. For the calculation of both ratios, we used our own table. A series of 102 children were examined.
Results:
The mean value of AC/A ratio for esotropias was 4.86 +/- 2.05. The mean value of AC/A ratio for the control group was 3.9 +/- 1.92. The difference was 0.96 and was statistically significant at the level of 5% (Student's t test). The AC/A ratio is high in esotropia ranging from 1 to 10. At 58% of esotropias, the AC/A ratio is higher than the mean value of AC/A ratio of the control group. The mean value of the NC/D ratio for esotropia was 5.9 +/- 1.51. The mean value of the NC/D ratio for the control group was 5.1 +/- 1.5. The difference of 0.8 was statistically significant at a level of 5%. Thus, in esotropia the NC/D ratio is high. The NC/D ratio in esotropia ranges from 1 to 10. The NC/D ratio is low in 16% of esotropias.
Conclusion:
Our own table for calculating the AC/A and NC/D ratios was useful because it facilitates their determination. The mean values of AC/A and NC/D ratios in esotropia are high and range from 1 to 10. In 58% of cases the AC/A ratio is high and in 84% of cases the NC/D ratio is high and can be responsible for the oculomotor imbalance.