[Orbital volume in congenital clinical anophthalmos]

The purpose of this study is to report orbital volume measurement results in patients with congenital clinical anophthalmia before and after therapy and to compare them with normal values.

Normal values were obtained from 35 healthy children (22 boys, 13 girls; aged 3 month to 7 years) in whom MRI was done for non-ophthalmological reasons. 18 patients with congenital anophthalmos could be included, 9 with bilateral, 8 with unilateral disease and 1 microphthalmos. 6 of them had MRI follow-up (more than one examination).

Orbital volume at birth is 7 ml and it increases with age: Orbital volume = 7.701 x age (month) (0.2484) ml. It is around 14.2 ml at the age 1 year, 17 ml with 2 years and reaches 23 ml with 7 years. In unilateral clinical anophthalmos orbital volume is 35 to 58 % compared with the healthy side and 31 to 65 % compared with the normal values. In bilateral cases the volume is 43 to 70 % of the normal value. During treatment it develops in parallel to the normal values.

The normal values measured by our group are in accordance with the only published study by Bentley . MRI orbital volumetry is a reliable method without using radiation. It allows us to quantify the bony asymmetry and is suitable for therapy control when using orbital expanders. The congenital missing eye might be the most important reason why the orbit does not develop in the normal way to a normal size. Self-inflating high, hydrophilic hydrogel expanders do not seem to be able to compensate this, in spite of the fact that they work very well to prepare the socket for a prosthesis.