Ординатура / Офтальмология / Английские материалы / Pediatric Ophthalmology for Primary Care 3rd edition_Wright, Farzavandi_2008

clearly visualized, but a cloudy cornea blocks the view of iris structure. Tables 15 1 and 15 2 list the common causes of a cloudy cornea at birth, in early infancy, and in childhood.

Congenital and Neonatal Onset of Cloudy Cornea

Corneal Dystrophy

There are 2 important corneal dystrophies that cause clouding of the cornea at birth or in early infancy: congenital hereditary endothelial dystrophy (CHED) and posterior polymorphous dystrophy (PPMD). These are disor ders of the corneal endothelium. The corneal endothelium actively pumps water out of the cornea, keeping the cornea clear. Dysfunction of the endo thelium results in edema of the cornea and corneal clouding.

Congenital Hereditary Endothelial Dystrophy

Congenital hereditary endothelial dystrophy is inherited as autosomal dominant or autosomal recessive. The autosomal recessive form is more common and presents at birth or in the neonatal period with bilateral cor neal opacities. The opacities can cause decreased visual acuity in the neona tal period and therefore may cause bilateral amblyopia and nystagmus. The cornea has an opaque, ground glass appearance secondary to corneal edema (Figure 15 1). Congenital hereditary endothelial dystrophy appears similar to cloudy corneas secondary to congenital glaucoma; however, in congenital glaucoma, the intraocular pressure is high and corneal diameters are large. In CHED, the cause of the corneal edema is abnormal corneal endothelium resulting in abnormal hydration of the cornea. Treatment for this disorder is corneal transplantation; however, the prognosis of corneal transplantation in infancy is guarded. Children with autosomal dominant CHED develop corneal clouding later (at a few years of age), do not develop nystagmus, and have a better visual prognosis.

Posterior Polymorphous Dystrophy

Posterior polymorphous dystrophy results in bilateral cloudy corneas at birth or in early infancy. Corneal clouding is quite mild and usually does not interfere with visual acuity. The corneal opacity is very mild, so treatment is usually not necessary. In rare cases, however, the opacity will progress and corneal transplantation may be indicated. In most cases, PPMD is an iso lated corneal problem, but some cases have been associated with glaucoma.

Table 15-1. Cloudy Cornea: Congenital and Neonatal Onset

A

B

C

Figure 15 4.

A, Bilateral Peter anomaly showing central corneal opacity. This patient also had glaucoma. Note that the corneas are large. B, Same eye after corneal transplantation, showing the clear corneal graft. Unfortunately, a massive graft rejection occurred 6 months after surgery.

C, Unilateral Peter anomaly that splits the pupil. This patient was treated conservatively with pupillary dilatation to expand the involved pupil and improve vision and part-time occlusion of the fellow eye to manage the amblyopia. This opacity improved over several years.

15 5). This anomaly probably represents abnormal migration of neural crest cells. Associated systemic anomalies have been described including cardiac defects, cleft lip, cleft palate, craniofacial dysplasia, and skeletal changes. In most cases, however, the Peter anomaly is isolated to the eye. Treatment

of Peter anomaly depends on the severity of the opacity. If the opacity is bilateral and blocks the visual axis, nystagmus and dense bilateral amblyopia are common. Under these conditions, corneal transplantation is advised. The prognosis for corneal transplantation is guarded because of the compli cations of graft rejection and dense amblyopia. Because of the poor results with corneal transplantation, patients with unilateral Peter anomaly are often treated conservatively without surgery. In some cases, Peter anomaly is associated with lens subluxation and lens adherence to the cornea

(Figure 15 6).

Figure 15 5.

Drawing of a corneal opacity. Peter anomaly is a defect in the posterior cornea with overlying corneal scarring.

Limbal Dermoids

Limbal dermoids are choristomas and represent abnormal surface ectoder mal tissue on the surface of the cornea. These are white or yellowish masses at the periphery of the cornea (limbus) and are usually unilateral (Figure 15 7). The limbal mass can cause irritation secondary to interference with blinking and tear coverage of the cornea. Corneal dermoids can also induce astigmatism, cause decreased visual acuity, and require surgical excision. In some cases, a corneal graft is required to replace corneal tissue. Close

Peter

Figure 15 6.

Drawing of lens adherence to cornea. Peter anomaly comes in various forms, all having a central corneal scar with a posterior defect and central iris adhesions.

examination of the dermoid often shows the presence of hair and hair folli cles. The tissue limbal dermoid cysts may be isolated or occur in association with Goldenhar syndrome (see Chapter 24).

Figure 15 7.

Limbal dermoids. A young child with a dermoid tumor at the corneal limbus. It was removed with a shave keratectomy.

Acquired Cloudy Cornea in Childhood

There are numerous causes of an acquired cloudy cornea, the more impor tant of which are listed in Table 15 2. The following are topics not covered in other chapters.

Congenital Syphilis

Syphilis is acquired in utero at any stage of pregnancy. At birth, there may be a generalized skin rash, jaundice, hepatosplenomegaly, rhinitis, and anorexia. The eyes appear normal. The first ocular complication includes a retinochoroiditis, occurring in the first few months to a year of life. By age 2 years, patients often show signs of neurosyphilis and central nervous

system involvement. The classical Hutchinson teeth occur as notched teeth and are late manifestations. The corneal involvement usually occurs late, between 5 and 20 years of age, as interstitial keratitis. This is an inflam mation of the deep corneal stroma that leads to corneal opacity. The cornea can become quite vascularized, and the vascular pattern can produce what is termed a corneal salmon patch. Treatment for ocular manifestations con sists of using topical corticosteroids and cycloplegics along with systemic treatment for the neurosyphilis. The systemic treatment of the neurosyphilis alone does not treat the interstitial keratitis because it is an inflammatory reaction and not necessarily caused by active infection.

Measles

Measles is caused by an RNA paramyxovirus and presents with an acute cough and conjunctivitis. In addition, patients have a keratitis with superfi cial punctate epithelial fluorescein staining. There are characteristic Koplik spots on the conjunctiva and caruncle. In most cases, the eye involvement is relatively mild; however, in chronically ill or malnourished children, the ker atitis can be quite severe. In developing countries, measles is a self limiting disease, but can be devastating and sometimes life threatening in underde veloped countries where there are large numbers of malnourished children. The more severe systemic complications of measles include pneumonia

and acute encephalitis. Rarely seen is the occurrence of subacute sclerosing panencephalitis. The treatment for the keratitis in uncomplicated measles is symptomatic relief with artificial tears. If there is a keratitis demonstrated by fluorescein staining of the cornea, topical antibiotics should be used to pre vent secondary bacterial infection. Topical corticosteroids–antibiotic combi nation can be used to reduce inflammation in severe cases.

Corneal Ulcers

Corneal ulcers are caused by a breakdown of the corneal epithelium with resultant necrosis of the corneal stroma. Corneal ulcers can be noninfectious (trophic ulcer) and caused by chronic corneal diseases such as vasculitis, severe corneal exposure, lack of sensory innervation (neurotrophic ulcer), or lack of vascular supply to peripheral cornea (lye burn). Infections cause corneal ulcerations when the infection violates the corneal epithelium and invades the corneal stroma. Clinically, the corneal ulcer presents as a white lesion in the cornea (Figure 15 8 and see Figure 13 3). There is usually

Figure 15 8.

Bacterial corneal ulcer is the white lesion in the central area of the cornea.

positive fluorescein staining in the area of the ulcer indicating the absence of corneal epithelium. If the lesion is in the visual axis, vision will be severely affected. Infectious corneal ulcers are difficult to treat because the cornea

is avascular and therefore immunocompromised. In many cases, weeks of high dose antimicrobial therapy are necessary to eradicate the offending organism. One of the major problems is secondary corneal scarring that occurs after the infection is cured. Corneal scarring may interfere with vision, necessitating corneal transplantation. The presence of a white corneal lesion and an inflamed eye should prompt immediate referral to an ophthal mologist. Infectious corneal ulcers can be caused by bacteria, fungus, virus, and even protozoa.

Bacterial Ulcer

Bacterial corneal ulcers are quite rare in children because the intact corneal epithelium prevents penetration of bacteria within the corneal stroma. A breakdown of the corneal epithelium, however, will provide a portal of entry for bacteria. Eyelid abnormalities (entropion with eyelash rubbing of the cornea), dry eyes, corneal exposure, and corneal trauma break down the corneal epithelium and increase the risk of bacterial infection. The use of extended wear contact lenses is another risk factor for developing bacterial keratitis. A history of conjunctivitis associated with contact lens use should prompt immediate referral, as this may represent a bacterial keratitis.