Nanophthalmos is an uncommon eye condition, characterized by an abnormally small eye that maintains its normal internal structure. The term, derived from Greek, means “dwarf eye.” This condition often leads to severe farsightedness.
Defining Nanophthalmos
Nanophthalmos is defined by an eye with a significantly shorter axial length, typically less than 20 millimeters. This reduced size results in severe hyperopia, or farsightedness, because light focuses behind the retina instead of directly on it. Eyes with nanophthalmos also feature a disproportionately large lens, a thickened sclera (the white outer layer of the eye), and a crowded anterior chamber (the space between the cornea and the iris).
Genetic Basis and Other Contributing Factors
Nanophthalmos is primarily a genetic condition, with many cases inherited. Several genes, including MFRP, PRSS56, and BEST1, contribute to its development by playing roles in eye growth and development. The condition can be inherited through autosomal recessive or autosomal dominant patterns. In some instances, nanophthalmos appears sporadically, meaning there is no clear family history.
Associated Ocular Complications
The small size and distinctive structure of nanophthalmic eyes predispose individuals to several ocular complications. Angle-closure glaucoma is a frequent concern due to the crowded anterior chamber. The iris can block the drainage angle, leading to an increase in intraocular pressure and potential damage to the optic nerve.
Choroidal effusion is another common complication, occurring when fluid accumulates under the choroid, the vascular layer beneath the retina. This can lead to retinal detachment. Severe uncorrected farsightedness in children with nanophthalmos can also lead to amblyopia, commonly known as “lazy eye,” where the brain favors one eye, leading to reduced vision in the weaker eye.
Diagnosis and Identification
Diagnosis of nanophthalmos typically begins with a thorough eye examination by an ophthalmologist. The doctor observes the eye’s small appearance and severe farsightedness. Ocular biometry, using A-scan or B-scan ultrasound, measures the eye’s axial length, which is usually less than 20 mm.
Optical coherence tomography (OCT) assesses the retina and choroid for abnormalities. Genetic testing can identify specific gene mutations associated with the condition.
Treatment and Management Approaches
Managing nanophthalmos involves addressing both the refractive error and potential complications. Strong corrective lenses, such as glasses or contact lenses, are necessary to manage severe farsightedness and help prevent amblyopia in children.
Glaucoma management in nanophthalmic eyes is challenging due to the eye’s anatomy. Treatment options include eye drops to lower intraocular pressure, laser procedures like laser peripheral iridotomy, and surgical interventions such as trabeculectomy. These surgical procedures carry a higher risk of complications.
Cataract surgery also presents increased difficulties and an elevated risk of complications, such as choroidal effusion. Specialized surgical techniques, including the creation of scleral vents, may be employed to reduce pressure and fluid buildup during or after the procedure. Consistent, lifelong eye examinations are necessary to monitor and manage any emerging complications.