Nelson_Pediatric Ophthalomology, 3e

18 2 Abnormalities Affecting the Eye as a Whole

NANOPHTHALMIA N anophthalmia is a subtype of simple micro phthalmia. It is a congenital and typically bilateral condition ( Fig. 2-7 ), although it can be unilateral. It is characterized by reduced globe vol ume, although the eye is otherwise grossly normal. Etiology ● Nanophthalmia results from an arrest in the growth of the eye during the embryonic stage and may result from a smaller optic vesicle anlage. ● Most cases are sporadic but both autosomal recessive and autosomal dominant inheri tance have been reported. Signs ● Reduced axial length of the globe ( < 20 mm) ● Very high hyperopia ( > 10 diopters) ● Reduced corneal diameter ● Lens is normal in size. ● Shallow anterior chamber ● Thick sclera ● Fundus may show crowded optic disc, vas cular tortuosity, and macular hypoplasia. ● Because of the anatomy, these eyes are at high risk for angle-closure glaucoma. They tolerate intraocular surgery poorly with a high rate of complications, including uveal effusion and retinal detachment. Differential Diagnosis ● High hyperopia in a normal eye Diagnostic Evaluation ● Measurement of corneal diameter ● A-scan to measure the axial length of the eye ● Pentacam and ultrasound biomicroscopy to image the anterior chamber and assess its depth ( Fig. 2-8 ) Treatment ● Glasses are needed to correct significant refractive error.

● Management of narrow-angle or angle-closure glaucoma is initially medical, although the response to treatment is typi cally poor, and miotics may even worsen the condition by relaxing the lens zonules. Pe ripheral laser iridotomy can relieve pupillary block and may be moderately successful. Laser trabeculoplasty, if performed, must be done early before anterior synechiae de velop and permanent damage to the outflow mechanism occurs. Iridoplasty, circumfer ential laser burns to the iris to contract the iris away from the anterior chamber angle, can further open the drainage angle. Cau tion must be used with fistulizing glaucoma surgery because postoperative malignant glaucoma can ensue. Because nanophthal mic eyes are more prone to significant post operative inflammation, steroids should be used judiciously. ● Removal of the lens must be anticipated and can be complicated by uveal effusion and nonrhegmatogenous retinal detachments. Although challenging in these high-risk eyes, small-incision cataract surgery is safe and diminishes the need for prophylactic sclerotomies. Prognosis ● The prognosis for vision is good if glau coma is treated early and successfully. Sharan S, Grigg JR, Higgins RA. Nanophthalmos: ultrasound biomicroscopy and Pentacam assess ment of angle structures before and after cata ract surgery. J Cataract Refract Surg . 2006;32(6): 1052-1055. Singh OS, Simmons RJ, Brockhurst RJ, Trempe CL. Nanophthalmos: a perspective on identification and therapy. Ophthalmology . 1982;89(9):1006-1012. Yalvac I, Satana B, Ozkan G, Eksioglu U, Duman S. Management of glaucoma in patients with nanophthalmos. Eye . 2008;22(6):838-843. REFERENCES

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