Isolated trabeculodysgenesis

In approximately 50% of infants and juvenile patients with glaucoma, isolated trabeculodysgenesis is the only developmental ocular anomaly found. This is the classic defect found in primary congenital glaucoma ( Fig. 19-2 ). These eyes have no developmental anomalies of the iris or cornea, except for an abnormal insertion of the iris into the angle wall. The iris and cornea may demonstrate secondary changes as a result of elevated IOP.

Anterior segment photograph of a patient with primary congenital glaucoma with an enlarged, clear cornea. A U-shaped Haab’s striae extends from the 9 o’clock to the 1 o’clock position. The slightly rolled edges of the original break in Descemet’s membrane parallel each other.

From Campbell DG, Netland PN: Stereo atlas of glaucoma, St Louis, Mosby, 1998.

This maldevelopment of the trabecular meshwork is present in one of two forms. In the most common form, the iris inserts flatly into the trabecular meshwork either at or anterior to the scleral spur ( Fig. 19-3 ). The ciliary body is usually obscured by this insertion, although the anterior ciliary body may be seen through thick trabecular meshwork if the angle is viewed obliquely from above. The invisibility of the angle recess and ciliary body in the eye with glaucomatous trabeculodysgenesis is a key distinction from the normal infant angle. The iris insertion level may vary along the chamber angle, with some portions of the iris inserting anterior to the scleral spur and other areas inserting at the spur or even posterior to the spur ( Fig. 19-4 ). The surface of the trabecular meshwork may have a stippled, orange peel appearance. The peripheral iris stroma may appear thinned and expose radial blood vessels, as are seen in the immature iris of normal infants. More pronounced iris thinning can occur if the eye enlarges.

Gonioscopic drawing of isolated trabeculodysgenesis with flat anterior iris insertion.

In isolated trabeculodysgenesis with flat insertion, the iris may insert behind, at, or anterior to the scleral spur. In this type of disease, the iris most commonly inserts anterior to the spur.

In the second form of isolated trabeculodysgenesis, the iris inserts concavely into the chamber angle wall. The plane of the iris is posterior to the scleral spur, but the anterior stroma sweeps upward over the trabecular meshwork obscuring the scleral spur and inserting into the upper portion of the trabecular meshwork just posterior to Schwalbe’s line. Thus the iris sweeps around the angle, forming a concave or ‘wrap-around’ insertion. This conformation is recognized most easily in brown irides and is less commonly seen in children than the flat iris insertion ( Fig. 19-5 ). Both the anterior flat iris insertion and the ‘wrap-around’ configuration may appear in later ‘juvenile’ forms of open-angle glaucoma through the third or fourth decade of life.

(A) Goniophotograph of a young patient with primary congenital glaucoma revealing a flat iris with peripheral thinning and peripheral radial vessels. A high insertion to the level of the scleral spur is not visible above but is visible below. The trabecular meshwork is slightly greyish, and there is no definition to Schwalbe’s line. There is no pigmentation within the trabecular meshwork, which is normal for young people. (B) Histopathology of primary infantile glaucoma. The iris and anterior ciliary body cover the scleral spur and posterior trabecular meshwork. The intratrabecular spaces are compacted. (C) Concave iris insertion in isolated trabeculodysgenesis. The iris may sweep up over the trabecular meshwork as a dense sheet or loose syncytium. Glaucoma associated with this type of iris insertion will respond to goniotomy in infants.

A from Campbell DG, Netland PN: Stereo atlas of glaucoma, St Louis, Mosby, 1998. B from Armed Forces Institute of Pathology. In: Alward WLM: Color atlas of gonioscopy, San Francisco, Foundation of American Academy of Ophthalmology, 2000.

Isolated trabeculodysgenesis must be differentiated from the gonioscopic appearance of the anterior chamber angle in a normal newborn eye. In a normal newborn, a flat insertion of the iris into the angle wall just posterior to the scleral spur is present. The normal angle recess forms during the first 6–12 months of life. The ciliary body is seen as a distinct band anterior to this iris insertion. The more narrow the ciliary body band, the more developmentally immature is the angle.

Isolated trabeculodysgenesis usually presents with symptoms of elevated IOP after the first month of life. A key point in the surgical management of glaucoma infants: if examination reveals isolated trabeculodysgenesis, a prompt goniotomy is highly successful.

Iridodysgenesis

Congenital anomalies of the iris are associated with maldevelopment of the trabecular meshwork, the anterior stroma, the full thickness of the iris, the iris vessels, or any combination of these structures. In these disorders, the appearance of the trabecularmeshwork may be similar to that found in isolated trabeculodysgenesis. In some cases, additional changes may be seen in the angle, such as irregular clumping of tissue, abnormal vessels, or iridocorneal adhesions.

Anterior stromal defects

Hypoplasia of the anterior iris stroma is the most common iris defect associated with developmental glaucoma. True hypoplasia of the anterior stroma, as opposed to atrophy or thinning, is diagnosed only when there is clear malformation of the collarette with absence or marked reduction of the crypts. This condition is to be distinguished from the stretching of the iris from elevated IOP, which can thin the anterior stroma. The pupillary sphincter may be quite prominent and can have a distinct ring appearance or a ‘feathered’ outer border ( Fig. 19-6 ; also see Fig. 19-32 ).

Anterior segment photograph of a patient with Axenfeld’s anomaly showing a prominent, centrally displaced Schwalbe’s ring with peripheral iris attachments. There is iris hypoplasia with loss of iris stroma.

From Campbell DG, Netland PN: Stereo atlas of glaucoma, St Louis, Mosby, 1998.

Iris hyperplasia causes a thickened, velvety, pebbled appearance of the anterior iris stroma. Hyperplasia is uncommon and is sometimes seen in association with Sturge-Weber syndrome.

Developmental anomalies of the iris vasculature can occur as a persistent tunica vasculosa lentis or as irregularly wandering superficial iris vessels. In persistence of the tunica vasculosa lentis ( Fig. 19-7 ), a regular arrangement of vessels is seen looping into the pupillary axis either in front of or behind the lens. Over time, attenuation and involution of the vascular veil occur, and continued clinical surveillance is usually sufficient.

Persistence of tunica vasculosa lentis. Blood vessels extend from peripheral iris and ciliary body to envelop the equator of lens.

Superficial anomalous iris vessels wander irregularly over the iris surface ( Fig. 19-8 ) and do not conform to the normal radial configuration of the iris vasculature. The pupil is usually distorted, and the iris surface has a whorled appearance, often with areas of hypoplastic anterior iris stroma. Present at birth, it is unclear whether these vessels represent an earlier onset of primary congenital glaucoma or an entirely different syndrome. Eyes with this condition have a grave prognosis and usually require multiple surgeries.

Anomalous superficial vessels course irregularly over the anterior stroma of the iris. The anterior stroma is distorted, and the pupil may be irregularly shaped.

Structural iris defects

A structural iris defect ( Fig. 19-9 ) may be seen as a small hole through the iris with no involvement of the sphincter muscle or as a full-thickness coloboma involving the sphincter. The most severe structural iris defect is aniridia, in which only a peripheral stump of iris remains.

Structural iris defects may be of a variety of configurations, all of which are demonstrated in this single iris. Total absence of sphincter may occur, as shown in the nasal side of this iris. Elliptic openings may penetrate the anterior stroma or full iris thickness, as seen in the temporal side of this iris.

Corneodysgenesis

The corneal stretching and clouding that occur as a result of elevated IOP are acquired, not congenital, defects. Congenital corneal defects may involve the peripheral, midperipheral, or central cornea, or they may appear as abnormalities of corneal size that exist regardless of whether the IOP is elevated. In most cases, associated congenital iris abnormalities exist.

In peripheral corneodysgenesis, a condition exists in which bridging iris filaments or bands attach to a prominent cord-like Schwalbe’s line (posterior embryotoxin) (see Figs 19-31 and 19-32 ). These peripheral abnormalities extend no more than 2 mm into the clear cornea and usually involve the entire corneal circumference. Axenfeld’s anomaly is the classic disorder demonstrating these abnormalities; however, in the absence of other associated anomalous defects of the angle, posterior embryotoxin alone is not associated with glaucoma and can be seen in as many as 8% of normal eyes.

Midperipheral lesions are found in addition to the peripheral abnormalities in patients with Rieger’s anomaly. The iris is attached to the cornea in broad areas of apposition that extend out toward the center of the cornea, and pupillary anomalies and holes of the iris are common. The cornea is usually opacified in the areas of the iris adhesions (see Fig. 19-35 ).

Central corneal anomalies may show evidence of adhesions between the collarette of the iris and the posterior aspect of the central cornea. The cornea usually is opacified centrally and may be thinned. Occasionally a corneal fistula forms. An area of clear cornea between the central defect and the corneal scleral limbus is common. These corneal defects have been called a variety of names, including Peter’s anomaly, posterior ulcer of von Hippel, and posterior keratoconus (see Fig. 19-36 ). Often distinctions among corneal opacifications can be made clinically with high-resolution ultrasound biomicroscopy.

Abnormalities of corneal size may occur as microcornea or macrocornea. Microcornea may be seen in a variety of congenital anomalies, including microphthalmos, nanophthalmos, Rieger’s anomaly, persistent hyperplastic primary vitreous, and congenital rubella syndrome. Macrocornea is seen in patients with Axenfeld’s syndrome or in X-linked recessive megalocornea. It is distinguished from the corneal stretching resulting from increased IOP by the absence of tears in Descemet’s membrane. The prognosis for control of glaucoma in eyes with corneodysgenesis is considerably worse than in eyes with isolated trabeculodysgenesis.

Office examination

Depending on the age and level of cooperation of the patient, general anesthesia may be required to evaluate the child with glaucoma. A complete ocular examination, including slit-lamp examination, applanation tonometry, pachymetry, gonioscopy, optic nerve evaluation, and retinoscopy, can be performed in the office in children older than 5 years of age and, with some training, in children as young as 3. If necessary, the child can be given a mild sedative, such as chloral hydrate syrup (100 mg/kg of body weight to a maximum dose of 3 g in normal, healthy, full-term infants 1 month of age or older). Chloral hydrate does not affect IOP readings.

Many children after age 5 years can undergo kinetic Goldmann visual field testing with the assistance of a patient and encouraging perimetrist. Pediatric glaucomatous visual field defects duplicate the spectrum of field defects seen in adult primary open-angle glaucoma. A gross confrontation visual field examination can be performed on children by holding a toy in the peripheral fields and either moving the toy or shining a light within the toy. Older and more cooperative children will provide a more detailed examination. By the age of 8–10 years, some children can cooperate for a full quantitative visual field examination.

Sometimes a reasonably good office examination can be performed on infants younger than 3 months using the infant diagnostic lens of Richardson and Shaffer ( Fig. 19-13 ). The lens allows examination of the anterior segment, the angle, and the optic nerve head and is well tolerated when placed in the eye with topical anesthesia. Using a direct ophthalmoscope, the examiner can obtain a good view of the posterior pole even if the child has small pupils and mild corneal haze.

Richardson-Shaffer lens (left) is a small version of the Koeppe lens (right) that fits into the lid aperture of infants. It is useful for examining the anterior segment, as well as the fundus.

Examination under anesthesia

General anesthesia usually is required for a thorough examination of children under the age of 5. With a healthy child and an anesthesiologist experienced in dealing with infants, there is little risk. Surgery has been performed on numerous children under 7 days of age.

A standardized routine for evaluations under anesthesia (EUA) is important, with an assistant simultaneously noting clinical findings determined by the examining physician. All of the essential information regarding the presence and type of glaucoma, the extent of damage, associated findings, and the appropriate surgical options should be established in a prompt, methodical fashion. The sequential components of the EUA consist of measuring the IOP, assessing the corneal thickness and diameters, gonioscopy, and ophthalmoscopy; additionally, axial length measurements, ultrasonic biomicroscopy, or cycloplegic retinoscopy may also be performed.

Intraocular pressure measurement

There are many variables to consider when assessing a child’s IOP: the child’s age; the patient’s level of activity or sedation; effects of anesthetics; corneal thickness and health; diurnal variations, and, perhaps most importantly, the choice of measuring instrument. The clinician can choose among a variety of tonometers based on various measuring principles: applanation (Goldmann or hand-held Perkins); indentation (Schiøtz); indentation-applanation hybrid (pneumotonometer); non-contact air-puff (Keeler Pulsair), or electronic (TonoPen or Mackay-Marg). Results among instruments vary.

In a large series of unanesthetized healthy children from birth through age 16 measured with the Pulsair device, three different phases of the IOP were identified:

• 1.
  

  Neonatal phase . Up to age 1, the average IOP was 10 mmHg, without gender differences, and unrelated to gestational age or birth weight.

  
  
• 2.
  

  Phase of increased IOP values . An exponential curve of rising IOPs up to age 7–8, rising faster in boys until age 4 and continuing more slowly in girls to age 9 was seen.

  
  
• 3.
  

  Phase of steady IOPs . From age 8 onward, females had higher IOPs than males, with ‘adult’ values obtained by mid adolescence. Different instrumentation yielded similar trends but with wide variability ( Table 19-1 ).

  
  
  
  

  Table 19-1

  
  

  Intraocular pressures (mmHg) among normal awake children using different tonometers

  
  

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  Age	Pulsair (SD) *	Perkins (SD) †	Pneumotonometer (SD) †
  Premature (26–37 weeks)	10.2 ‡	18.3 §	–
  0–1 year	10.6 (3.1)	4.6 (0.5)	14.5 (0.5)
  1–2 years	12.0 (3.2)	4.9 (0.5)	14.6 (0.6)
  2–3 years	12.6 (1.5)	5.8 (1.0)	15.3 (1.4)
  3–4 years	13.7 (2.1)	6.4 (1.8)	14.5 (0.9)
  4–5 years	13.6 (2.0)	7.9 (1.3)	14.8 (2.0)
  5–6 years	14.4 (2.0)	–	–
  6–7 years	14.2 (2.3)	–	–
  7–8 years	14.0 (2.5)	–	–
  8–9 years	14.3 (1.7)	–	–
  9–10 years	14.0 (2.7)	–	–
  15–16 years	15.2 (2.4)	13.2	16.42 (2.2)

   
  

  * Data from Pensiero et al ;

  
  

  † Jaafar & Kazi ;

  
  

  ‡ Spierer et al ;

  
  

  § Musarella & Morin.

  
  

When validated by intraoperative manometry under anesthesia, the Perkins applanation device tended to underestimate IOP (especially in the supine position), the TonoPen slightly overestimated IOP, and the pneumotonometer was most accurate. In another study of children under anesthesia, the Schiøtz tonometer gave the highest readings; moreover, it is also subject to many artifacts affecting its reliability, such as altered scleral rigidity, small corneal size, or surface abnormalities. Although only one tonometer is indispensable for examinations under anesthesia, another device or two is advisable to double check the measurement and confirm a tendency toward elevation or asymmetry with respect to the fellow eye.

General anesthetics lower IOP to variable amounts and at variable times after administration ( Table 19-2 ). Intraocular pressure measurements should be taken as soon as the child is quiet, and the precise interval in minutes between onset of anesthesia and the pressure measurements should be noted. Laryngeal mask anesthesia is a valuable alternative to tracheal intubation, with the added feature of causing significantly less IOP elevation at the time of extubation in both normal and glaucomatous eyes. The laryngeal mask is particularly useful in EUAs with children because it simultaneously protects the patient’s airway and allows the examiner unhindered access to both eyes for complete evaluation, such as Koeppe gonioscopy. A mask with an oral airway is also adequate and safe for short examinations. Intramuscular ketamine can be administered in younger children when examination is for diagnosis only; intravenous administration may raise the IOP slightly.

As in the management of adult primary open-angle glaucoma, it is best to place the measured IOP into a clinical context, giving special weight to trends or to asymmetric measurements between two eyes. The diagnosis of glaucoma depends on several factors, only one of which is the pressure level. Elevated IOP by itself, unless extreme, is insufficient to confirm the diagnosis of glaucoma.

To confirm a diagnosis of glaucoma and justify surgery, it is necessary to verify other signs, such as increased corneal diameter, corneal haze, increased cup-to-disc ratio, evidence of anterior segment dysgenesis, or glaucoma in the fellow eye. Otherwise, it is better to re-examine the child in 4–6 weeks to confirm the diagnosis before performing surgery.

Corneal measurements: diameter and central thickness

As with IOP, there is no absolute normal limit for the corneal diameter among children, although growth trends are evident ( Table 19-3 ). Measuring the corneal diameters, both horizontally and vertically, is a fundamental part of childhood glaucoma assessment ( Fig. 19-14 ). A good baseline measurement is required both for initial diagnosis and for detection of subsequent corneal enlargement. An effective measurement of the corneal diameter can be obtained using calipers to measure the horizontal diameter from the first appearance of the white scleral fibers at the limbus on one side to the same point on the other side, from the 9 o’clock to 3 o’clock positions. This is then repeated vertically from 6 o’clock to 12 o’clock. The measurement is accurate to approximately 0.5 mm; therefore with this technique, changes of less than 0.5 mm should not be considered significant. Some authors prefer customized templates in increments of 0.25 mm for greater precision.

Congenital glaucoma examination series. (A) Corneal measurement. (B) View through a Swan-Jacobs lens into the angle of a child with primary infantile glaucoma.

B from Alward WLM: Color atlas of gonioscopy, San Francisco, 2000, Foundation of American Academy of Ophthalmology.

The measurement of the central corneal thickness (CCT) of adult eyes with primary open-angle glaucoma has a major impact on the clinician’s assessment for two reasons: (1) applanation IOP readings are profoundly affected by the CCT ( viz ., thicker CCTs ‘overestimate’ and thinner CCTs ‘underestimate’ true IOPs), and (2) there is a significant risk factor for developing glaucoma damage, independent of IOP corrections, with thinner CCTs. One confounding factor in applying CCT findings in children with glaucoma is the apparent slight thickening of the infant cornea until adult values are reached between age 5–9 years old.

Nevertheless, the clinical effect of CCT measures on the IOP in children is similar to that seen in adults, with thicker corneas seen with ocular hypertension and thinner CCTs on average among black children than in whites. One large study comparing children under 3 years old – those status-post-congenital glaucoma surgery versus age-related normals undergoing nasolacrimal dilation – demonstrated thinner CCT measurements in glaucomatous eyes, which positively correlated with their larger corneal diameters and longer axial lengths. On the other hand, thick CCTs are expected in eyes with significant corneal edema from elevated IOP, and have been reported in eyes with glaucoma with aniridia and in eyes status-post-congenital cataract surgery. Although examinations under anesthesia often require specula to pry the lids for several minutes, with some possible corneal drying, the clinical impact on CCT measures is negligible. The value of pachymetric measures of CCT in infantile glaucoma, though not completely clarified, is nevertheless useful.

When examining the cornea, the ophthalmologist must look for corneal haziness and tears of Descemet’s membrane. Tears involving the visual axis, as evident during retinoscopy, must be noted because they can adversely affect a child’s visual acuity and contribute to developing amblyopia.

Axial length measurement

The measurement of axial length by A-scan ultrasonography has been recommended by some investigators for routine use in the diagnosis and follow-up of congenital glaucoma, contending that it is a sensitive and reversible measure of disease. Others assert that the corneal diameter measurement, besides being easier to measure using simpler equipment, is the most significant clinical feature in detecting congenital glaucoma. One retrospective study suggests that the major contribution of both axial measures and corneal diameters is in the initial diagnostic stages of glaucoma management, but neither parameter distinguished which patients would require re-operation, especially after the age of 2 years.

Gonioscopy

In the operating room, Koeppe equipment can be used under clean but non-sterile conditions, such as during EUA ( Fig. 19-15 ). Gonioscopy has classically been performed with a smooth-domed Koeppe 14- to 16-mm lens, with a Barkan light and hand-held binocular microscope. If marked corneal clouding exists, the view may be improved by applying topical anhydrous glycerin, or, if necessary, removing the epithelium with a blade or with a solution of 70% alcohol or 10% cocaine on a cotton-tipped applicator. The Koeppe lens also can aid in the visualization of the iris, the crystalline lens, vitreous, and fundus. The lens neutralizes irregular corneal reflexes and improves the view through a small pupil, even allowing disc photography through a relatively small pupil. Thus the examiner sees the entire optic nerve head (albeit minified) in one field. Contemporary four-mirror lenses, whose corneal surface is less than 12 mm, can alternatively be used in conjunction with an operating microscope.

Bilateral lens insertion of Koeppe lenses to reveal angle abnormalities better seen by comparing both eyes.

During surgery under the operating microscope, the surgeon can use either a sterile Barkan operating lens (a truncated Koeppe lens) for tangential viewing during insertion of a gonio-knife, or a gas-sterilized four-mirror Sussman or Zeiss lens viewed perpendicularly through the microscope.

Ophthalmoscopy

Cupping of the optic nerve is an early sign of increased pressure and occurs much more quickly and at lower pressures in infants than in older children and adults ( Fig. 19-16 ). This characteristic of dramatically enlarging – and after surgery, reversible – cup size in children reflects the greater amount of elastin amidst the connective tissue of the infantile optic nerve head, allowing an elastic response to fluctuation in IOP ( Fig. 19-17 ; see Fig. 13-6 ). Decreased cupping can occur rapidly after IOP reduction and is the single most confirmatory sign that the glaucoma has been surgically stabilized or reversed.

Asymmetric disc cupping in a child with developmental glaucoma. (A) Note steep-walled cup. This is typical of glaucomatous cupping in the elastic infant eye. (B) The left eye has no cupping.

Child with isolated trabeculodysgenesis. (A) Before goniotomy. (B) After goniotomy. Note the reduction in cup size, which is common following successful surgery during the first 1–2 years of life.

Cup-to-disc ratios greater than 0.3 mm are rare in healthy infants and should cause suspicion of glaucoma ( Table 19-4 ). Inequality of optic nerve cupping greater than 0.2 cup-to-disc ratio is also suggestive of glaucoma.

In infancy, the glaucomatous cup can be oval but is more often round, steep-walled, and central, with notable circumferential enlargement. With successful control of the IOP, the cup will either remain stable or its size will decrease. An increased cup size is indicative of uncontrolled glaucoma, and the ophthalmologist must make careful drawings or take photographs with a hand-held camera for future comparison. With normalization of IOP, a reduction in cup size is especially evident in infants less than 1 year of age ( Table 19-5 ).

Other than the reversibility of cupping, the alterations of the optic nerve in infantile glaucoma are comparable to the disc changes seen in adults. For example, vertical notching at the inferior and superior poles of the disc appears less often than concentric cupping, as do nerve fiber slit defects. These findings suggest that other than the elastic properties of the infant’s disc, the child’s optic nerve is subject to similar effects that cause disc cupping in adult glaucoma.

Cycloplegic refraction

After therapeutic normalization of IOP, cycloplegic refraction should be performed to correct significant differences in refractive errors between the two eyes. The importance of refractive surveillance of these eyes cannot be over stressed. Anisometropic and strabismic amblyopia, as well as myopic astigmatism, are prominent causes of visual loss among these children, especially in unilateral cases. Vigorous amblyopia management is as important as adequate glaucoma control by surgery or medication.

Systemic evaluation

A thorough systemic evaluation is also warranted in these children, both to check for any signs of syndromes that may be associated with glaucoma and to ensure the safety of general anesthesia. The coordination of the child’s assessment with a pediatrician or specialist in genetics is invaluable.

Other glaucomas

Primary congenital glaucoma is diagnosed when glaucoma is found in a child with isolated trabeculodysgenesis but with no other ocular or systemic anomalies of development and no other ocular diseases that could result in an increase in IOP. Complete general physical and ocular examinations must be performed. Isolated trabeculodysgenesis may also be the ocular anomaly producing glaucoma in Rubinstein-Taybi syndrome, Sturge-Weber syndrome in infancy, trisomies 13–15, Lowe syndrome, and rubella.

Other causes of corneal enlargement or clouding

Megalocornea is a condition of marked corneal enlargement, often to diameters of 14–16 mm. Other signs of congenital glaucoma are absent. These eyes have deep anterior chambers and may have iridodenesis secondary to stretched zonules and a loose lens. On gonioscopic examination, the examiner may find a normal angle, prominent iris processes, or a broad, densely pigmented trabeculum. A high degree of axial myopia is part of the differential diagnosis of megalocornea, as determined by retinoscopy and axial measurements.

Ninety per cent of megalocornea cases occur in males with sex-linked inheritance ( Fig. 19-20 ). Families can have some members with megalocornea and others with primary congenital glaucoma; autosomal dominant congenital miosis can also be seen with megalocornea. This variety of anterior segment disorders is felt to be a manifestation of germ-line mosaicism, with similar embryogenic neural crest cells expressing phenotypic diversity. Some clinical observers relate that megalocornea may be a spontaneously arrested form of congenital glaucoma. Individuals with megalocornea and their families must therefore be periodically checked for the development of glaucoma as well as for cataracts, which can form in this condition.

Megalocornea. Front (A) and lateral (B) views of a 4-month-old boy with large eyes since birth. Corneal diameters were 14.5 mm, and intraocular pressures were 13 mmHg in each eye. Gonioscopy demonstrated normal infant angles, and optic discs were healthy with 0.2 cup-to-disc ratios. An uncle had megalocornea with normal intraocular pressures.

Sclerocornea is a condition in which extensions of opaque scleral tissue course into the cornea, usually bilaterally, in both autosomal dominant and recessive pedigrees. Vessels usually penetrate deeply and superficially into the cornea. It is sometimes seen in conjunction with cornea plana, Ehlers-Danlos syndrome type VI, and microcornea.

Numerous metabolic diseases can cause corneal haze, including the infantile form of cystinosis, six mucopolysaccharidoses, and the mucolipidoses.

Posterior polymorphous dystrophy occasionally can be present in infancy with corneal edema and without corneal enlargement. It is a dominantly inherited, bilateral disease characterized by peripheral anterior synechiae and polymorphous opacities, typically vesicular, at the level of Descemet’s membrane. The associated glaucoma can be either an open-angle or synechial-closure type and usually appears later in life. By corneal specular microscopy, it can be distinguished from the iridocorneal endothelial syndrome.

Congenital hereditary endothelial dystrophy can be present at birth or in the first 1–2 years of life and is seen as a diffuse, bilateral, symmetric corneal edema with photophobia. Stromal thickness can be three times the normal level, and clouding can vary from a mild haze to a milky, ground glass opacification ( Fig. 19-21 ). Although usually distinct from congenital glaucoma, cases have been reported that histologically demonstrated congenital hereditary endothelial dystrophy at the time of penetrating keratoplasty, following prior glaucoma surgery.

Congenital hereditary endothelial dystrophy. This cornea is markedly edematous but has no enlargement. Intraocular pressure was normal. Patient has since undergone corneal transplantation with excellent results.

Obstetric trauma, such as forceps injury that ruptures Descemet’s membrane, can result in corneal edema and corneal clouding. These ruptures often are vertical but may run in any direction. There is no corneal enlargement, and the optic nerve is normal. Intraocular pressure typically is normal but may be elevated, usually transiently. The condition is usually unilateral and affects the left eye because of the higher incidence of left anterior occiput presentation at birth. Frequently, periorbital tissues exhibit signs of trauma as well, at least in the perinatal period.

A host of inflammatory diseases – such as viral keratitis (e.g., adenovirus serotype 10) or viral iridocyclitis (e.g., Herpes family) – can cause corneal edema and clouding. Rubella keratitis is particularly suspect in the newborn. Syphilitic keratitis is often seen with secondary iridoschisis and angle closure. Other conditions to be considered include human immunodeficiency virus and phlyctenular disease.

Other causes of epiphora or photophobia

Diseases presented in the section on corneal clouding, such as inflammation and congenital hereditary endothelial dystrophy, can cause epiphora and photophobia. Some of the disorders discussed in this section, particularly the corneal dystrophies, can result in opacification of the cornea.

The most common cause of epiphora is obstruction of the nasolacrimal duct. Photophobia is not associated with this problem. A chronic mucopurulent discharge may be evident.

Any of several causes of conjunctivitis in the infant can present with redness and tearing. Chemical conjunctivitis caused by silver nitrate prophylaxis is a common cause in the newborn. Bacterial and chlamydial infections are usually associated with a mucoid or mucopurulent discharge and must be ruled out. Viral conjunctivitis must also be suspected. Corneal abrasions are also frequent causes of acute ocular irritation in children and are diagnosed from history and fluorescein examination.

Meesman’s corneal dystrophy usually is present in the first several months of life. Patients exhibit ocular irritation, and examination reveals multiple clear to gray-white punctate opacities of the corneal epithelium that are intraepithelial cysts. The condition is bilateral, dominantly inherited, and is the probable equivalent of Stocker-Holt dystrophy.

Reis-Buckler dystrophy can be present in the first few years of life, with ocular pain resulting from recurrent epithelial erosions. Examination reveals irregular patches of opacity in the region of Bowman’s layers that progress to a diffuse reticular pattern associated with an anterior stromal haze.

Other optic nerve abnormalities

Congenital malformations of the disc must be distinguished from disc changes caused by glaucoma. Congenital malformations include congenital pits, colobomata, and optic nerve hypoplasia.

Axial myopia can be associated with a tilted disc and accompanying scleral crescent, which is usually located inferiorly or temporally. This condition can give the optic nerve a ‘chopped-off’ appearance.

Large physiologic cups also must be distinguished from pathologic cupping caused by glaucoma. Making the distinction is not a common problem in an infant who has accompanying signs and symptoms. Problems can arise in older children in whom changes resulting from globe elasticity are not as evident and yet who are too young for precise visual field testing. Careful examination of all ocular parameters is essential, and follow-up examinations may be required before a definitive diagnosis can be made. Examination of family members can be helpful because several members may reveal a pattern of large discs with prominent cupping. Photographic documentation of the child’s optic discs, if available, is invaluable for subsequent comparison, and should be performed at the EUA or in the office if the child can cooperate.

Preoperative management

Parents of these patients are usually anxious and may have significant feelings of guilt. They should be advised that the disease has occurred because of factors that are beyond their control. The future of long-term surveillance and collaboration between physician and family should be emphasized, as well as the need for frequent follow-up examinations (often with general anesthesia), possible repeat surgeries, chronic medication use, and amblyopia management for visual rehabilitation. With bilateral glaucoma, early referral to rehabilitation specialists may maximize a child’s adjustment to limited vision in the early preschool and school years. Families will need a good deal of support, and facilitating contact with support groups of families similarly affected is particularly helpful.

Surgery should not be delayed. Medications are used briefly in the preoperative period only to permit clearing of the corneal edema and improve visualization at the time of diagnostic examination and surgery.

Although there is a wide variety of medications that reduce IOP, studies and dosage profiles for optimal administration in infants and children are usually lacking. β-Blockers, such as timolol 0.25% or betaxolol suspension 0.25%, may be administered (1 drop every 12 hours); other commercially available drugs of the same class, such as levobunolol, metipranolol and carteolol, may be equally efficacious. Prostaglandin anaologs are usually well tolerated, without demonstrable toxicity in pregnant mothers or children. Although these drugs have not yet been approved for use in children by the Food and Drug Administration, studies have shown that a minimum of side effects developed from short-term use of timolol. Parents should be cautioned to discontinue the medications if any side effects, such as asthmatic symptoms, develop. Apneic spells have been reported in a neonate receiving timolol, and caution is advised in infants of low gestational age. The anesthesiologist should be told that the patient is taking a β-adrenergic blocking agent.

Other topical agents approved for adult glaucoma can also be cautiously used in combination with a β-blocker, with special attention to side effects. Eyedrop preparations of adrenergic agonists (e.g., dipivefrin, apraclonidine), prostaglandins (e.g., latanaprost), or topical carbonic anhydrase inhibitors (dorzolamide) can be used 1 drop every 12 hours. Brimonidine should be avoided , as it may produce bradycardia, hypotension, hypothermia, and apnea in infants (manufacturer’s package insert, 1998). For short-term use, acetazolamide (5–10 mg/kg body weight every 6–8 hours) orally in suspension form may be considered. Because of the local congestive effects on the conjunctiva and the availability of other drugs, miotics (e.g., pilocarpine 1–2% every 6 hours) are less useful than in the past.

Initial surgery

In a series of 287 eyes, Shaffer reported that one to two goniotomies cured 94% of cases diagnosed between the ages of 1 and 24 months. Because this is the age of occurrence of most primary congenital glaucomas, this statistic is encouraging.

In patients in whom the onset of glaucoma occurred before 1 month of age, the success rate of 26% was poorer. Some of these patients had significant hypoplasia and increased vascularity of the iris and thus are classified now as cases of iridodysgenesis with anomalous iris vessels rather than cases of isolated trabeculodysgenesis. It is unclear whether these cases of early onset are truly primary congenital glaucoma or a more severe syndrome.

Patients with the onset of the disease after 2 years of age show poorer control with goniotomy; Shaffer reported a 38% control rate with one or two goniotomies.

A large retrospective study of a dozen reports in the world literature showed equally good results: goniotomies were most successful in children under 1 year of age, achieving successful results more than 75% of the time. Recent studies continue to confirm this, although relapses have been reported as late as 15 years following surgery. Life-long glaucoma surveillance is mandatory for these children.

Goniotomy is a safe procedure when performed skillfully. Analysis of 695 goniotomies performed without the use of intracameral viscoelastic revealed only one complication of severe visual loss, an eight-ball hemorrhage with blood staining of the cornea. There were no infections and no lens injuries. There were a few small iridodialyses (4 cases), small cyclodialyses (2 cases), and shallow anterior chambers lasting 1–2 days (5 cases) that had no sequelae. The most common complication was a cardiopulmonary event of concern to the anesthesiologist during anesthesia (6 cases). Although all patients recovered, we perform bilateral goniotomies when indicated to avoid the risks involved with an additional anesthesia and to avoid any delay in required surgery.

In patients diagnosed between 1 and 3 years of age, our approach to management is to perform two goniotomies before proceeding to trabeculotomy or trabeculectomy ( Fig. 19-22 ). Many prefer goniotomy rather than a primary trabeculotomy for several reasons: it does not disturb the conjunctiva, which may be needed for later filtering surgery; it is performed with direct visualization of the trabecular meshwork, often engaging quadrants of the angle untouched by trabeculectomy or trabeculotomy, and it incises only those tissues, the superficial trabecular tissues, that are necessary to cure this disease.

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