Peters anomaly is one disease in a constellation of diseases that causes corneal opacity due to dysgenesis of the anterior segment during development. Peters anomaly can cause devastating corneal opacity in an infant leading to severe amblyopia. Diagnosis involves careful anterior segment exam as well as testing for other systemic findings which would suggest Peters Plus syndrome. Treatment involves surgical intervention to establish a clear visual axis with either corneal transplant or optical iridectomy.
Coloboma and other anomalies of anterior segment ICD-9 743.44
Peters’ anomaly is one disease in a constellation of diseases that causes corneal opacity due to anterior segment dysgenesis (ASD) during development. An estimate of 44-60 cases of Peters anomaly are reported in the United States annually. It has been known over the years as primary mesodermal dysgenesis of the cornea, congenital anterior synechiae, posterior keratoconus and anterior chamber cleavage syndrome. Peters anomaly affects the iris, corneal endothelium, and Descemet’s membrane, leading to Peters type I. Peters type II in addition features lens abnormalities and tend to be bilateral. 60% of those with Peters anomaly have bilateral involvement. In both forms, opacification of the cornea leads to an amblyogenic effect on an infant's developing vision. Peters Plus syndrome includes short stature, developmental delay, dysmorphic facial features, cardiac, genitourinary, and central nervous system malformations. These systemic findings are seen in up to 60% of patients. Bilateral Peters is more strongly associated with systemic malformations (71.8%) as compared to unilateral Peters anomaly (36.8%). Peters is also associated with many other ocular pathologies including glaucoma, sclerocornea, corectopia, iris hypoplasia, cataract, ICE syndrome, aniridia, iris coloboma, persistent fetal vasculature and microcornea.
Peters anomaly falls within the spectrum of anterior segment dysgenesis, which includes other diseases such as Axenfeld-Rieger syndrome. There have been multiple genetic loci that have been identified as causes for Peters anomaly including PAX6, PITX2, PITX3, FOXC1, FOXE3, CYP1B1, MAF and MYOC. The variety of genes involved contributes to the significant degree of phenotypic variability found in ASD. Reported chromosomal abnormalities in chromosome 20, trisomy 13 and chromosome 11 have been reported to contribute to Peters. Peters can occur sporadically, but autosomal dominant and recessive inheritance have been reported.
In addition, lab studies on mice have shown that a deficiency of heparan sulfate leads to improper neural crest TGF-β2 signaling leading to ASD2. Peters Plus syndrome is an autosomal recessive congenital disorder affecting beta-1,3-galactosyltransferase-like glycosyltransferase gene(B3GALTL) on chromosome 13.
Premature infants are at highest risk for development of ASD, including Peters anomaly. In addition, a deficiency of heparan sulfate can lead to abnormal neural crest development in utero. Fetal alcohol syndrome has been reported as a cause of Peters. Intrauterine infection and teratogenic exposures during pregnancy may also be associated with Peters. 
Histologically, in Peters type I, the cornea at the area of opacity has an an endothelium with underlying iridocorneal synechiae that extend from the iris collarette to the border of the corneal opacity. There are diverse histological changes in Descemet’s membrane. Most commonly, the Descemet’s membrane of the cornea is absent, but there has also been a reported case of a “multiple-layer” structure of Descemet’s. Keratolenticular adhesions to the posterior cornea are also seen in some cases and can be visualized with slit lamp biomicroscopy or ultrasound biomicroscopy (UBM). Thinning, thickening, or absence of Bowman’s membrane and defects in the posterior stroma can occur, including residual fibrosis in the opacified stroma and central concave defect in the posterior corneal stroma (posterior ulcer) with disorderly stromal lamellae in the ulcer bed. The opacification often involves the central cornea; however, it can also affect the entire cornea. Peters type II also features lens abnormalities that can be seen histologically.
The critical embryological event that is associated with Peters is the formation of the anterior chamber. Normal corneal development depends on neural crest migration which occurs in 3 distinctive waves during embryogenesis to produce the structures of the anterior chamber. This typically occurs during the 7th week of gestation.
The first wave involves the formation of the corneal endothelium as the neural crest cells migrate between the surface ectoderm and the lens. In the second wave, peripheral neural crest cells migrate between the newly formed corneal endothelium and surface ectoderm to form the keratocytes that will lead to formation of corneal stroma. The final wave involves formation of the iris stroma. Any disruption of neural crest migration or separation including incomplete migration/differentiation of central corneal endothelium and Descemet membrane precursor cells or defective separation between the primitive lens and cornea can lead to an ASD.
PAX6, PITX2, and FOX genes, mentioned above as possible genes associated with Peters, are homeobox genes that are involved with corneal development. However, the mechanisms of how these transcription factors interact at the periocular neural crest cell level to direct their differentiation into corneal endothelium are still under investigation. There are also reported cases of Peters that do not have mutations in these genes. 
Peters anomaly occurs as a result of an in-utero abnormality of multiple genetic loci that causes anterior segment dysgenesis. No primary prevention has been described for this disorder.
Peters anomaly is diagnosed by anterior segment examination, which shows corneal opacification present at birth. B-scan ultrasonography or ultrasound biomicroscopy can be used to examine the anatomic relationship between the lens, iris and cornea. Ultrasound biomicroscopy is useful in detecting central corneal opacity, the absence of Descemet's membrane, and iridocorneal and keratolenticular adhesions. If full-thickness corneal transplantation is performed, then histopathologic findings of the cornea are a useful adjunctive tool in the diagnosis of Peters as well. Genetic testing of one of the aforementioned genes can help to confirm Peters anomaly, but it is classically diagnosed clinically.
Patients are often seen initially by the pediatrician and found to have an abnormal red reflex with a corneal leukoma. Nystagmus or abnormal vision may be noted by the pediatrician or guardian of the patient.
Patients should be screened for systemic malformations, including congenital cardiac defects, craniofacial dysplasia and skeletal, central nervous system, and urogenital anomalies.
Anterior segment exam reveals an opacification on the cornea with underlying loss of endothelium and Descemet’s membrane with overlying corneal edema. Iris strands can often been seen attached to the area of opacified cornea. These strands may or may not be still attached to the body of the iris. Corectopia is often present in addition to a shallow anterior chamber. In addition, in type II Peters’ lens is typically adherent or closely abutting the cornea.
These figures show the stromal opacity within the cornea in a 1 week old newborn child. Note the extremely shallow anterior chamber.
The most common sign is a corneal opacification seen at birth.
Decreased vision by way of blockage of the central visual axis due to the corneal opacification will lead to deprivation amblyopia. In addition, patient may suffer from glaucoma due to likely malformation of the angle structures as well as shallow anterior chamber.
Peters’ is diagnosed by clinical features seen on anterior segment exam. Genetic testing can be done to characterize other potential systemic involvement.
Genetic testing for aforementioned genes and chromosomes.
Peters’ anomaly is part of a spectrum of ASD which have similar pathways of development. These include: Axenfeld-Rieger anomaly and syndrome, iridocorneal endothelial syndrome, posterior polymorphous dystrophy, congenital hereditary endothelial dystrophy, and congenital hereditary stromal dystrophy.
Peters anomaly is on the differential diagnosis for congenital corneal opacifications. The S.T.U.M.P.E.D classification system can aid the differential.
- tears in Descemet's
- endothelial dystrophy
Treatments for Peters’ anomaly aim at clearing the central visual axis to allow for visual maturation. Full thickness penetrating keratoplasty is the current standard of care. Iridoplasty for reformation of iris and cataract extraction for those with lens involvement.
Medical therapy would include monitoring of glaucoma as intraocular pressure are often elevated in Peters’ patients due to the dysgenesis of anterior segment structures including angle structures.
Medical follow up
Patients with Peters’ anomaly should be considered for a corneal transplant for clearing of the central visual axis as soon as medical possible. Due to the systemic problems that can accompany Peters’ anomaly including heart and central nervous system defects, consult to genetics, cardiology and neurosurgery should be considered. Close follow up for management of glaucoma with frequent examination under anesthesia.
Penetrating keratoplasty is indicated in Peters’ for infants. Cataract extraction with limited anterior vitrectomy in the setting of an opacified lens and corneal lenticular adhesion.
Surgical follow up
As with any corneal graft, frequent follow-up is required to help prevent graft failure. In children, follow-up with frequent exam under anesthesia is warranted to check pressure as these infants will be on long term immunosuppression with topical steroids and cyclosporine to avoid rejection. Complete suture removal within the first 2-3 months may be necessary as younger patients tend to have a more robust response with corneal neovascularization along the suture tracts.
Treatment for spectacle correction and amblyopia treatment should be initiated as soon as possible.
Graft failure, infection, and steroid induced glaucoma.
Prognosis for maintaining clear graft after 2 years is a low 22% as reported in a study by Rao et al5. Due to the young age of the patients, it is believed that immunologic rejection is the most common cause of graft failure. Graft failure rates have been reported to increase when combined with lensectomy and vitrectomy. In addition, those with preexisting glaucoma have a poorer visual prognosis.
Overall visual prognosis is poor after corneal graft with one study finding that less than one-third of eyes with Peters’ have visual acuity better than 20/400. In that same study, predictors of poor visual outcome included stromal vessels and large corneal grafts >8mm.
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