Congenital Cataracts

A 4,559-g boy was born post-term, at 42 weeks and 3 days’ gestation, to a primiparous 26-year-old mother via cesarean delivery secondary to failure to progress after postdates induction. Within a few hours of birth, the neonate was noted to have bilateral leukokoria.

The mother had had a fairly unremarkable pregnancy, with normal laboratory test results and normal ultrasonography results. Specifically, she was rubella- and varicella-immune, she had no history of herpes simplex virus infection, and screening test results were negative for syphilis.

Her history was significant for congenital bilateral cataracts; according to the child’s maternal grandmother, the suspected etiology of the cataracts was congenital rubella, based on the grandmother’s lack of immunity at the time of birth. No medical records of the mother’s neonatal test results were available to the current patient’s medical team. The grandmother said that no other symptoms of congenital rubella syndrome had been noted at the mother’s birth.

A pediatric ophthalmology consultant later confirmed the diagnosis of congenital bilateral cataracts in the boy. The cataracts’ etiology was suspected to be genetic; nevertheless, further testing was done to rule out infectious and metabolic causes. Polymerase chain reaction test results of the infant’s saliva and the mother’s blood were negative for cytomegalovirus. The mother’s blood was negative for toxoplasmosis immunoglobulin G and M. Newborn screening test results were negative for metabolic diseases, specifically galactosemia.

Upon microscopic examination, the cataracts were noted to be central stellate or crystalline-like opacities. The cataracts were deemed visually significant, so the patient underwent cataract extraction surgery at 4 weeks of life and again at 7 weeks of life. 

The infant has been doing well postsurgically, developing good visual behavior with the use of contact lenses to account for the loss of focusing by the natural lenses.

Discussion

A proper eye examination of a newborn by a primary care provider involves a visual assessment of the external eye anatomy, as well as direct ophthalmoscopic examination of the eye.¹ The ophthalmoscope is used to assess for the retinal reflex, also called the red reflex. The term retinal reflex is preferred, because the color of a normal retina can vary from red to orange to yellow, and in dark-skinned individuals even almost white. The examiner should compare one eye to the other and can examine the parents’ eyes if there is uncertainty that the retina’s color is related to ethnicity. 

Concern for an abnormal retinal reflex should arise if the retina is black, white, asymmetric, partly obscured, or dim. If a primary care provider is uncertain about retinal findings of an eye examination, a timely ophthalmology consult should be obtained.

The term leukokoria comes from Greek and means “white pupil.” The differential diagnosis for leukokoria in a newborn includes cataract, retinal detachment, retinopathy of prematurity, other retinal malformation or disease, intraocular infection, retinal vascular abnormality, and intraocular tumor such as retinoblastoma. An ophthalmologist can elucidate the etiology using indirect ophthalmoscopy.

A cataract is an opacity of the lens. Cataracts typically appear black on direct ophthalmoscopy, but they appear white when light is shone laterally at the eye and the observer looks directly at the eye. Cataracts can vary in size from pinpoint to completely obscuring the retinal reflex. A small cataract might be missed if it is located in the periphery of the lens and the pupil is constricted; such cataracts, however, are less clinically significant. The larger a cataract is, and the more it blocks the visual axis, the more concern there is for its effect on vision. Cataracts may be unilateral or bilateral.

In the United States, congenital cataracts occur in approximately 2 in 10,000 live births.² Worldwide prevalence varies among countries and depends on numerous factors such as access to obstetric care and the incidence of congenital rubella. In a 2003 population-based epidemiologic study in the Atlanta, Georgia, metropolitan area, 59% of congenital cataracts reported over a 40-year period from 1968 to 1998 were isolated defects, 22% were associated with a syndrome, and the remaining 20% were associated with nonsyndromic birth defects.²

Isolated cataracts tend to be diagnosed later in life, with 38% of cases diagnosed after 6 weeks of life.² In cases of inherited cataracts, the most common mode of inheritance is autosomal dominant.³ Infectious causes of congenital cataracts include toxoplasmosis, cytomegalovirus, syphilis, rubella, herpes simplex virus, measles, polio, influenza, and varicella-zoster virus. Many but not all of these conditions are tested for during routine prenatal care. The most common metabolic cause of cataracts is galactosemia (types 1-3).⁴ Galactosemic cataracts can develop within a few days of life but are not visible at birth. All state newborn screening programs include tests for classic galactosemia (type 1), but requirements for testing for types 2 and 3 vary by state.⁴

In order to optimize visual outcomes in children, surgery for visually significant cataracts should occur between 4 and 8 weeks of life.⁵ Nonvisually significant cataracts can convert to visually significant cataracts by way of physical changes in lens opacity over time, or by inducing amblyopia, where the brain ignores the visual signal from the cataractous eye. For these reasons, all cases of pediatric cataracts should be monitored by an ophthalmologist.

References

1. American Academy of Pediatrics Section on Ophthalmology, American Association for Pediatric Ophthalmology and Strabismus, American Academy of Ophthalmology, American Association of Certified Orthoptists. Red reflex examination in neonates, infants, and children. Pediatrics. 2008;122(6):1401-1404.
2. Bhatti TR, Dott M, Yoon PW, Moore CA, Gambrell D, Rasmussen SA. Descriptive epidemiology of infantile cataracts in metropolitan Altanta, Ga, 1968-1998. Arch Pediatr Adolesc Med. 2003;157(4):341-347.
3. Olitsky SE, Hug D, Plummer LS, Stass-Isern M. Abnormalities of the lens. In: Kliegman RM, Stanton BF, St. Geme JW III, Schor NF, Behrman RE, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, PA: Elsevier Saunders; 2011:2169-2172.
4. Barry GT. Classic galactosemia and clinical variant galactosemia. In: Pagon RA, Adam MP, Ardinger HH, et al, eds. GeneReviews. Seattle, WA: University of Washington. http://www.ncbi.nlm.nih.gov/books/NBK1518/. Published February 4, 2000. Updated April 3, 2014. Accessed October 1, 2015.
5. Birch EE, Stager DR. The critical period for surgical treatment of dense congenital unilateral cataract. Invest Ophthalmol Vis Sci. 1996;37(8):1532-1538.