Injectable self inflating hydrogel pellet expanders for the treatment of orbital volume deficiency in congenital microphthalmos: preliminary results with a new therapeutic approach

Background/aim: Children with congenital microphthalmos are usually able to wear an eye prosthesis but the cosmetic aspect is determined by the size of the orbital volume deficiency. Instead of using a ball shaped standard hydrogel expander or a regular orbital implant, which would necessitate enucleation of the microphthalmic eye, this study investigates the feasibility of volume augmentation with injectable pellet expanders, as formerly suggested for acquired anophthalmos in adults only. Method: The pellet expander is made from a self inflating hydrogel that takes up water by osmosis (dry state: length 8 mm, diameter 2 mm, volume 0.025 ml; in vitro hydrated state after around 1 day: length 15 mm, diameter 4 mm, volume 0.24 ml; swelling capacity: 9.6-fold). This report concerns six patients (two girls and four boys) aged between 4 months and 42 months with unilateral microphthalmos who were treated by injection of 4-14 pellet expanders into the retrobulbar orbital tissue. Volume augmentation was 1-3.5 ml. The pellets were injected using a customised trocar and placed behind the microphthalmos directed into the intraconal space. Results: The increasing orbital volume was noticeable within 2 days and was confirmed by ultrasonography and magnetic resonance imaging. The final result can be anticipated by the volume augmentation effect produced by the amount of saline solution injected in the orbital apex region. All patients were fitted with an artificial eye, which was subsequently enlarged every 3-5 months. Anophthalmic enophthalmos was fully compensated with this technique. No complications have been encountered to date. Conclusions: Orbital volume augmentation with injectable self inflating hydrogel expander pellets is apparently a safe, quick, and minimally invasive technique for various indications in orbital reconstructive surgery-for example, to treat an enophthalmic appearance in microphthalmos and congenital or acquired anophthalmos.