Abnormalities in the Size, Shape, or Location of the Pupil
Dyscoria is an abnormal pupil shape, typically resulting from congenital malformation such as ARS (see Fig 21-14).
Congenital miosis (microcoria) may represent an absence or malformation of the dilator pupillae muscle. It can also occur secondary to contracture of fibrous material on the pupil margin owing to remnants of the tunica vasculosa lentis or neural crest cell anomalies. The pupil rarely exceeds 2 mm in diameter, is often eccentric, and reacts poorly to mydriatic drops. Severe cases require surgical pupilloplasty. Ectopia lentis et pupillae refers to eccentric microcoria with lens subluxation, often from biallelic ADAMTSL4 mutations (also see the section “Corectopia”).
Many cases of congenital mydriasis (iridoplegia) fall within the aniridia spectrum, especially if the central iris structures from the collarette to the pupillary sphincter are absent. Congenital cardiovascular defects may be associated with congenital mydriasis in patients with heterozygous ACTA2 mutation, which sometimes causes an alternate phenotype of prominent iris flocculi rather than iridoplegia. Other causes include iris sphincter trauma, pharmacologic mydriasis, and acquired neurologic disease that affects parasympathetic innervation.
Milewicz DM, Østergaard JR, Ala-Kokko LM, et al. De novo ACTA2 mutation causes a novel syndrome of multisystemic smooth muscle dysfunction. Am J Med Genet A. 2010;152A(10): 2437–2443.
Normally, the pupil is located approximately 0.5 mm inferonasally from the center of the iris. Minor deviations of up to 1.0 mm are usually cosmetically insignificant and are not considered abnormal; displacement greater than this is considered corectopia. Sector iris hypoplasia or other colobomatous lesions can lead to corectopia. Vision can be good.
Isolated noncolobomatous, autosomal dominant corectopia has been reported. Progressive corectopia can be associated with ARS or, in adults, with iridocorneal endothelial (ICE) syndrome.
Ectopia lentis et pupillae is corectopia associated with lens subluxation. It is often due to biallelic ADAMTS4 mutations. The pupils and lenses are displaced in opposite directions. The pupils may be very small and misshapen; they often dilate poorly (see Chapter 23).
Polycoria and pseudopolycoria
True polycoria (in which each pupil has a sphincter mechanism) is very rare. Most accessory iris openings are pseudopolycoria. These iris holes may be congenital or may develop in response to progressive corectopia and iris hypoplasia in ARS (Fig 21-18) or, in adults, in ICE syndrome. Pseudopolycoria can also result from trauma, surgery, or persistent pupillary membranes.
Figure 21-18 Pseudopolycoria secondary to Axenfeld-Rieger syndrome.
(Courtesy of John W. Simon, MD.)
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.