Nanophthalmos

Nanophthalmos is a rare developmental eye condition characterized by abnormally small eyes (reduced axial length, typically less than 20 mm in adults) that are otherwise structurally normal, distinguishing it from microphthalmos where structural abnormalities are present. The term derives from the Greek word 'nanos' meaning dwarf. Synonyms include nanophthalmus and pure microphthalmos. The condition affects both eyes (bilateral) and is present from birth, though it may not be diagnosed until later in childhood or adulthood when complications arise. The small eye in nanophthalmos leads to extreme hyperopia (farsightedness), typically greater than +8 diopters, due to the shortened axial length. The lens and cornea are relatively normal in size but disproportionately large for the small globe. Patients are at significantly increased risk for angle-closure glaucoma because the anterior chamber is shallow and crowded. Uveal effusion syndrome, characterized by fluid accumulation beneath the choroid and retina, is another serious complication that can lead to retinal detachment. The thickened sclera seen in nanophthalmos is thought to impede normal drainage of fluid from the eye, contributing to uveal effusion. Several genetic forms have been identified, including NNO1 (linked to chromosome 11), NNO2 (associated with MFRP gene mutations), and forms associated with PRSS56, TMEM98, and BEST1 gene mutations. Management focuses on monitoring and treating complications. Angle-closure glaucoma may require laser iridotomy or surgical intervention. Uveal effusion may be treated with partial-thickness sclerectomy to improve fluid drainage. Cataract surgery, when needed, carries higher risk in nanophthalmic eyes due to the small surgical space and propensity for uveal effusion. Regular ophthalmologic monitoring is essential for early detection and management of complications.

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