Retinal structural and vascular changes in posterior microphthalmos

Posterior microphthalmos (PM) is a rare developmental disorder characterised by high hyperopia, short axial length, presence of retinal papillomacular fold and relatively normal anterior segment findings. The study objective is to describe the retinal structural and vascular changes in eyes with PM with spectral domain optical coherence tomography, optical coherence tomography angiography and multicolour imaging.

In this retrospective, comparative case series, 10 eyes of five patients with PM as cases and 10 eyes of five age- and sex-matched controls were included. Structural changes, namely inner and outer retinal layer thicknesses, were measured using optical coherence tomography. Multicolour imaging findings were noted. Perifoveal vascular changes with qualitative and quantitative assessments were analysed using optical coherence tomography angiography.

The foveal dip was absent in all 10 eyes (100 per cent) with PM. There was an elevated retinal papillomacular fold in six eyes (60 per cent) and intraretinal cystoid spaces in two eyes (20 per cent) with PM. The inner retinal layers were thicker in PM. On multicolour imaging, foveal avascular zone and retinal wrinkles were identified in eyes with retinal papillomacular fold in blue and green reflectance images. Perifoveal vascular changes in optical coherence tomography angiography included foveal area size reduction in superficial and deep vascular networks. The foveal capillary vessel densities were higher in PM compared to the controls in both superficial (46.3 ± 3.7 per cent; p = 0.000) and deep (54.7 ± 3.5 per cent; p = 0.000) capillary plexuses. Flow areas in superficial (p = 0.693) and deep (p = 0.088) capillary plexuses were not statistically relevant.

The study suggests that in PM, retinal foreshortening occurs in one meridian leading to secondary changes such as loss of foveal dip, posterior bowing of the outer layers of the eye, thickening of the inner retina and ultimately, retinal papillomacular fold formation. The findings of the study need further validation in a larger series of patients with PM.