Background/aims To evaluate treatment with custom, three-dimensional (3D) printed conformers for socket expansion in congenital microphthalmia and anophthalmia (MICA).

Methods Retrospective analysis of prospective cohort from 2016 to 2020. All children received custom-made 3D-printed conformers increasing in size. We measured height, width, thickness, surface and volume of first and consecutive conformers, as well as horizontal palpebral fissure length (HPF) at start and follow-up visits. We analysed these parameters for severely (<45%) and moderately (>45%–75%) affected children, based on affected axial length on ultrasonography.

Results We included 18 cases (9 severe, 9 moderate) with a total of 174 conformers (88 severe, 86 moderate) and a mean follow-up of 2.8 years (range 1.3–4.8). The mean relative HPF increased from 77% to 93% with 16/17 cases reaching >80%, and 12/17 cases >90% symmetry. Horizontal and vertical conformer dimensions increased up to 10 months of treatment, with a steeper slope for the severe group (10.5% vs 5.5% for height and 9.0% vs 6.1% for width gain per treatment month, for severe and moderate MICA, respectively). After 10 months of treatment conformer height and width increased only slightly. No serious complications were observed.

Conclusion 3D-design and printing of solid conformers results in highly acceptable horizontal eyelid symmetry in the treatment of congenital MICA. The mean increase in conformer height and width in the first 10 months should be about 170% for moderate and about 200% for severe MICA. The presented conformer size formulas can aid ophthalmologists and ocularists to plan conformer treatment.