165

through the abnormal membrane obstructing the trabecular meshwork from the outside in, towards the anterior chamber space (165). Trabeculotomy can be performed when the cornea is cloudy and therefore is the preferred procedure if the cornea remains opaque, thereby making angle visualization for goniotomy impossible. Both goniotomy and trabeculotomy address the anatomic defect present in this disease, acting to clear away the abnormal tissue creating obstruction to outflow of aqueous humor through the trabecular meshwork.

Trabeculectomy (filtration surgery) is an alternative surgical approach in which a partial thickness fistula is created between the anterior chamber and the sub-Tenon’s space outside the eye, thereby allowing aqueous humor outflow to bypass the abnormal trabecular meshwork. It is utilized when angle surgery fails. In children, trabeculectomy is often combined with antimetabolite medication (e.g. Mitomycin-C or 5-fluorouracil) in order to prevent the fistula from scarring closed.

Drainage implant (Seton) surgery involves the placement of a tube from an externally placed reservoir into the anterior chamber,

165 Trabeculotomy utilizing the Harm’s trabeculotome.

thereby allowing an alternative outflow pathway for aqueous humor. It may be especially useful in more difficult cases. Cycloablation is used to reduce aqueous humor production. Destruction of the ciliary processes can be performed with cryotherapy or with laser. Laser can be applied externally or internally through the use of an endoscopic probe.

With these new tools now available in the armamentarium against pediatric glaucoma, progression to a blind, painful, and often unsightly eye is less likely than in preceding decades. However, in these unfortunate cases enucleation is still sometimes necessary and can be very helpful in returning the affected child to a more normal routine and appearance. Modern orbital implants can provide excellent ocular prosthesis support and very satisfactory cosmesis.

Summary

In summary, the pediatric patient with the signs and symptoms of glaucoma presents infrequently to the primary care provider. Most providers will see only a few of the cases described in this chapter during his/her career. Even with prompt diagnosis and referral to the appropriate ophthalmic specialist, treatment can be challenging and often less than optimal, requiring multiple surgical procedures and long-term medication administration in many cases, even in the hands of very experienced providers. The implications for lifelong visual compromise often depend upon the diagnostic acumen of the harried pediatrician or family practitioner during a busy clinic day. The importance of prompt specialty referral cannot be overemphasized.

Retinal diseases are amongst the most challenging of eye conditions for the nonophthalmologist to diagnose, due to the limited nature of the in-office, undilated eye exam. The standard hand-held direct ophthalmoscope available in most physician offices allows the examiner to see a greatly magnified view of the optic nerve and posterior retina, but offers a limited view of the remaining retina. A fully dilated examination using an indirect ophthalmoscope offers a substantially wider field of view, allowing for evaluation of other important anatomical structures within the retina (166).

The nonophthalmologist is often the first physician to evaluate a child and diagnose early signs of retinal disease such as poor visual attention, nystagmus, or even leukocoria. By early recognition of the possibility of these conditions and prompt referral to an ophthalmologist, the primary physician offers the patient the best opportunity for early intervention and possible treatment, when applicable.

166

166 Normal retina,demonstrating the major anatomical structures seen with indirect ophthalmoscopy.Note that the optic nerve head (wide arrow) is pink in color, the caliber of the arterioles (small arrow) is about 2/3 that of the venules (arrow), and the retina is evenly pigmented. The fovea (arrowhead) shows a normal pigmentation pattern and reflex indicative of normal development.

DEFINITION/OVERVIEW

Coats’ disease, or retinal telangiectasia, is a relatively rare condition of congenital retinal vasculature anomalies resulting in massive external retinal and subretinal accumulation of exudate (167).1–3 The classic vasculature changes are described as focal or multifocal telangiectatic vessels and microaneurysms within the arterial system of arterioles and capillaries, but these anomalies may also occur within the venular system.2 These vascular lesions are commonly found in the peripheral retina, but may also be seen centrally. The massive exudation often found in this disease can cause retinal detachment and may lead to vision loss if detachment occurs within the macula. When extensive elevation of the retina occurs, this disease may mimic retinoblastoma or other retinal tumors, and is an important condition to differentiate when such diagnoses are being considered.

167

167 Coats’ disease:retinal image showing characteristic telangiectatic blood vessels (arrow) and focal areas of yellow-white subretinal and intraretinal exudates (arrowhead).

ETIOLOGY

Coats’ disease is a sporadic disorder, without a known inheritance pattern. Recent reports have suggested that Coats’ disease may be caused by a somatic mutation in the NDP (Norrin) gene, which has been implicated in other diseases of retinal vasculogenesis. The disease is a congenital vascular disease characterized by the presence of telangiectasias of the inner retina vessels and dilated thin-walled arterioles and capillaries.

Histopathologic studies have shown that the vessel wall may consist of only endothelium, with or without a PAS-positive basement membrane. The high intravascular pressure and low vascular permeability is thought to allow for extravasation of serum, plasma, and blood cells, which accumulate within and beneath the retina. The leakage of serum is thought to allow accumulation of cholesterol and lipid in the external retina space and also stimulates retinal fibroblasts and other inflammatory cells, leading to subretinal fibrosis, further lipid deposition, and cystic changes within the retina.2,3

The inciting cause of this vascular thinning has been proposed to be the presence of PASpositive mucopolysaccharides within the vascular walls or within the retina itself, but the exact etiology of this congenital vascular disease is not known.4

CLINICAL PRESENTATION

Children may present with strabismus, decreased vision, or leukocoria. Coats’ disease is usually a unilateral disease and occurs more frequently in boys (2:1 male to female ratio). The mean age of onset is 5 years, with most cases diagnosed at ages 2–10 years. It is a sporadic disorder, with rare instances of vasculogenic retinal disease in family members. Patients with Coats’ disease have no known systemic disease such as hypertension or hypercholesterolemia that might predispose them to having retinal fluid extravasation.

For the ophthalmologist, indirect ophthalmoscopy shows areas of retinal elevation with yellow-white exudate both beneath and within the retina (168).3 Hemorrhages may also be seen. If fluorescein angiography is performed, telangiectatic vessels and microaneuryms are classically identified in the inner retinal layers. The disease may show

168

168 Coats’ disease:retinal image showing confluent areas of exudates (arrow) and adjacent area of retinal detachment (arrowhead).

focal areas of exudate, or massive accumulations of confluent lipid and cholesterol deposition. Advanced cases may present with retinal detachment and leukocoria, and areas of retinal dysplasia may simulate retinal tumor.

DIFFERENTIAL DIAGNOSIS

The most important differential diagnosis to exclude in a patient with Coats’ disease is retinoblastoma. The age of onset overlaps with that of retinoblastoma, and clinically differentiating between these two diseases can be challenging. Indeed, there have been multiple case reports of patients having undergone enucleation for presumed retinoblastoma who were found to have Coats’ disease on histopathologic examination. Other important diseases to consider are retinal exudation due to other vascular diseases such as angiomas and macroaneurysms, toxocariasis, toxoplasmosis, and rarely retinal tumors of other types (lymphoma).

DIAGNOSIS

The diagnosis of Coats’ disease is made by direct visualization of the retina using indirect ophthalmoscopy. Fluorescein angiography can be very helpful in visualizing the abnormal vasculature and identifying the classic telangiectasias and microaneurysms (and excluding other retinal anomalies). B-scan ultrasonography may also be helpful in