[An ultrasound biomicroscopic study on changes of the structure of ocular anterior segment after topical application...

To observe the changes of ocular anterior segment and the relation between the intraocular pressure (IOP) and these changes after the topical application of cycloplegia using ultrasound biomicroscope (UBM), especially to observe the changes of ciliary body thickness and ciliary body-lens distance.

The quantitative measurement of UBM and the measurement of IOP had been done in 48 normal eyes before and after the topical use of 2% homatropine solution. The results were statistically analyzed.

In the parameter reflecting the change of the anterior chamber angle after using 2% homatropine, the trabecular iris angle decreased, the angle open distance 250 decreased, the iris thickness 1 increased, the anterior chamber became deeper and the iris-lens contact distance became shorter, and all these differences were statistically significant (P < 0.05). In the parameter reflecting the changes of ciliary body, the ciliary body thickness and the ciliary process thickness decreased, the scleral ciliary body angle increased, the iris-zonule distance decreased and the ciliary body-lens distance increased, and all these differences were significant statistically (P < 0.05). The IOP increased from 2.35 +/- 0.46 kPa to 2.43 +/- 0.47 kPa after the topical use of 2% homatropine, but the differences were not statistically significant (P > 0.05).

After the topical application of cycloplegia, the anterior chamber becomes deeper, the anterior chamber angle becomes narrower, the ciliary body becomes thinner and moves backward and the ciliary body-lens distance increases. By using UBM the structure of ocular anterior segment in its moving state can be observed and these structures can be measured quantitatively. The ultrasound biomicroscopic imaging has its advantages in the morphological study of ocular anterior segment.