Long term follow-up of axial length and orbital dimensions in congenital microphthalmia and anophthalmia

Purpose: To evaluate axial length (AL), orbital width (OW) and height (OH) development in congenital microphthalmia and anophthalmia (MICA) using serial ultrasonography measurements. Methods: A longitudinal prospective cohort (n = 74) of unilaterally and bilaterally affected MICA patients was followed from 2013 to 2022 at the university hospital in Amsterdam, the Netherlands. Clinical entity, age, severity category based on axial length, conformer treatment and intra-orbital cysts were registered. The main outcome measures were the absolute and relative growth of AL, OW and OH. Surgical and intra-orbital cyst cases were described separately. Results: Absolute microphthalmic eye size increased in 27/49 (55%) unilateral MICA eyes, but growth arrest/decrease in the remaining could shift the case to a more severe category over time. A final affected/unaffected orbital symmetry >= 80% was seen in the large majority of unilateral cases (45/46 for OW, 43/46 for OH). Cases with AL < 10.5 mm had orbital symmetry <80% more often. Most orbital symmetry changes were seen in moderate and severe unilateral cases treated with 3D-printed conformer therapy starting at age <1 year, with 6/10 (60%) symmetry increase, 30% unchanged symmetry and 10% symmetry decrease. All cases older than 6.5 years (n = 6) did not show any change anymore, regardless of treatment. For bilateral and unilateral mild cases, orbital dimensions kept the same proportions during follow-up, with or without conformer treatment. Conclusions: Using severity categories in MICA based on relative AL may aid the decision to start conformer treatment, as most orbital symmetry changes were seen in moderate and severe unilateral cases receiving 3D-printed conformer therapy that started under age 1.