Microphthalmia is a congenital condition where one or both eyes are abnormally small. This developmental disorder results in underdeveloped eyeballs. It affects approximately 1 in 5,300 babies born in the United States each year, with global estimates ranging from 0.2 to 30 per 10,000 births.
Understanding Microphthalmia
Microphthalmia varies in severity, from slightly smaller eyes to cases where the eyeball appears almost entirely missing. A diagnosis typically involves an adult eye length below 21 mm, compared to an average of 23.8 mm. The cornea, the clear front part of the eye, may also be smaller, with a diameter under 9 mm in newborns or 10 mm in children over two years.
The reduced eye size can significantly affect visual function, ranging from mild impairment to blindness, depending on severity and associated abnormalities. Microphthalmia can affect one eye (unilateral) or both eyes (bilateral). When unilateral, the size difference can lead to facial asymmetry as a child grows due to its impact on orbital growth.
Causes and Associated Conditions
Microphthalmia development involves genetic and environmental factors. Genetic causes include specific gene mutations or chromosomal abnormalities. Over 90 genes are linked to microphthalmia, with SOX2, OTX2, and STRA6 being common, accounting for about 75% of bilateral anophthalmia or severe microphthalmia cases. Chromosomal abnormalities are found in approximately 20-30% of cases, often with syndromic forms.
Environmental factors during pregnancy can also contribute. These include maternal infections like rubella, toxoplasmosis, cytomegalovirus (CMV), or influenza. Exposure to drugs or toxins, such as isotretinoin or thalidomide, maternal alcohol consumption, or vitamin A deficiency, are also associated.
Microphthalmia can be an isolated condition, meaning it is the only health problem, or syndromic, occurring as part of a broader genetic syndrome affecting multiple body systems. Syndromic microphthalmia accounts for 60-80% of cases. Examples include CHARGE, Fraser, and Walker-Warburg syndromes.
Associated ocular abnormalities often include:
Coloboma (missing eye tissue)
Cataracts (cloudy lens)
Microcornea (small cornea)
Retinal detachment
Persistent fetal vasculature
Non-ocular conditions, if part of a syndrome, can involve neurological issues, skeletal anomalies, intellectual disability, or craniofacial malformations like cleft lip or palate.
Diagnosis and Management Approaches
Diagnosis can occur before birth through prenatal ultrasound or fetal MRI. After birth, diagnosis is made via a clinical ophthalmological examination, including eye inspection, palpation, and corneal diameter measurements. Advanced imaging, such as MRI or CT scans, is performed to assess the condition’s extent and rule out other neurological or systemic abnormalities. Genetic testing can help identify the underlying cause, especially in bilateral or severe cases, though a specific gene may not always be identified.
Management is individualized, aiming to optimize visual function and support overall development. Medical interventions include low vision aids like magnifiers and medications for conditions such as glaucoma. Surgical options address issues like cataracts or other structural abnormalities. Prosthetic eye fitting is common, helping encourage orbital growth and prevent facial asymmetry, especially in unilateral cases. Therapeutic support, such as occupational therapy, aids daily living skills, while early intervention programs provide comprehensive developmental support.
Life with Microphthalmia
Living with microphthalmia requires ongoing medical and visual support, tailored to individual needs and condition severity. Regular follow-ups with a multidisciplinary team, including ophthalmologists, pediatricians, and geneticists, are important to monitor eye health and overall development. For children, educational considerations are significant, and school accommodations, such as specialized learning techniques or assistive technologies, may be necessary.
Emotional and psychological well-being are also important as individuals and families adapt. Support groups and community resources offer valuable connections for sharing experiences and accessing practical advice. These resources help foster independence and promote a positive quality of life, emphasizing that affected individuals can lead fulfilling lives with appropriate support.