Microphthalmia is a congenital disorder that results in one or both eyeballs being abnormally small. It is characterized by a shortened axial length (in the range of 14 to 20 mm) that causes extreme hyperopia (+7.5 to +21 D). Other ocular features include normal anterior segments, elevated papillomacular retinal folds, steep corneal curvatures, shallow anterior chambers and thickened scleral walls. The disorder results in mild to moderate vision loss. Several genetically distinct forms of isolated microphthalmia have been reported. MCOP5 is a specific form of microphthalmia caused by mutations in the MFRP gene.
Diagnosis of the disorder can be made in-utero by ultrasound or CT scans as well as by genetic testing. Postnatal diagnosis is made on the basis of an ocular examination. Treatment is focused on retaining visual acuity as well as improving facial appearance. Patients may require corrective lenses or patches on their strong eye to encourage the poorer eye to develop better vision. In some cases, patients may need conformers, which are plastic structures that help the eye socket and bones to develop properly. Surgical intervention may be required in certain cases.
Nowilaty et al. (2013) described the molecular and biometric characteristics of 24 posterior microphthalmos affected patients (ages 2-47 years) from 12 Saudi families. Seven of the families were consanguineous. The parents in each of the families were unaffected except for one case where there were minor refractive errors. The patients were subjected to keratometry, corneal pachymetry and axial length measurement. The patients were all found to have high hyperopia ³8 D, normal anterior segments, axial length <20 mm (mean 16.25 mm), foreshortening of the posterior chamber and characteristic retinal papillomacular folds/wrinkles. Patients did not show signs of retinal degeneration, developmental ocular malformations, syndromic disease or night blindness. Mean cycloplegic refraction for the right eye was +15.09 D. While axial length was positively correlated with corneal diameter, it showed an inverse relationship with corneal power (mean 48.89 D). A genetic analysis revealed a novel homozygous truncating mutation in the MFRP gene of one patient. The authors noted no clinical differences between patients carrying MFRP mutations, or PRSS56 mutations, or those with no detected mutation.