Ординатура / Офтальмология / Английские материалы / Shields Textbook of Glaucoma, 6th edition_Allingham, Damji, Freedman_2010

Figure 13.8 Severe optic nerve cupping in the left eye of an 8-year-old girl with juvenile-onset glaucoma.

In contrast to infants and very young children, older children with glaucoma typically present with decreased vision (usually from induced myopia, but occasionally from end-stage optic nerve damage) or because they are known glaucoma suspects (e.g., with Sturge-Weber syndrome, aniridia, or aphakia or pseudophakia). Although elevated IOP produces corneal enlargement limited to the first 3 years of life, scleral stretching persists for approximately 10 years, producing progressive myopia (and often astigmatism), usually seen in older children with glaucoma. While optic nerve cupping is not by itself a reliable indicator of glaucoma, its presence should prompt a thorough evaluation for possible glaucoma in a child of any age (Fig. 13.8). Older children infrequently present with symptoms of acute glaucoma, such as nausea associated with eye pain, headaches, and even colored haloes around lights (e.g., secondary to trauma or angle closure, as with cicatricial retinopathy of prematurity).

Visual loss from infant and childhood glaucoma most often results from pathologic changes in the eye, such as corneal opacification and optic nerve damage. Poor vision may also occur despite adequate IOP control, secondary to the development of anisometropia or strabismic amblyopia, especially in unilateral

or asymmetric bilateral childhood glaucoma. DIFFERENTIAL DIAGNOSIS

The clinical features of glaucoma in infancy and childhood overlap partly with those of other pediatric ophthalmic conditions, with the exception of elevated IOP (Table 13.2) (3, 5). When faced with ocular signs or symptoms suggestive of possible glaucoma, the clinician must consider and rigorously exclude glaucoma, keeping in mind that identifying a coexisting nonglaucomatous disorder does not eliminate the possibility of glaucoma. For example, glaucoma may complicate uveitis, Peters anomaly, and megalocornea; glaucoma may even occur coincident with the commonly encountered congenital nasolacrimal duct obstruction (3).

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Table 13.2 Differential Diagnosis of Features Commonly Found in Childhood Glaucomas

I. Disorders showing “ red eye” and epiphora

A.Congenital nasolacrimal duct obstruction

B.Conjunctivitis (infectious, chemical exposure)

C.Corneal epithelial defect/abrasion

D.Keratitis (especially herpes simplex)

E.Inflamed anterior segment (uveitis, trauma)

II. Disorders showing corneal edema or opacification

A.Forceps-related birth trauma (with Descemet tears)

B.Congenital malformation/anomaly

1.Sclerocornea

2.Peters anomaly

3.Choristomas (dermoid-like)

4.Other anterior segment dysgenesis C. Corneal dystrophy

1.Congenital hereditary endothelial dystrophy

2.Posterior polymorphous dystrophy D. Keratitis

1.Herpetic

2.Rubellaa

3.Phlyctenular

E. Metabolic disease

1.Mucopolysaccharidoses

2.Mucolipidoses

3.Cystinosis

4.Oculocerebrorenal (Lowe) syndrome

III. Conditions showing corneal enlargement

A.Axial myopia

B.Megalocornea

C.Megalophthalmos

IV. Conditions with actual or “ pseudo” optic nerve cupping

A.Physiologically large optic nerve cup

B.Coloboma or pit of the optic nerve

C.Atrophic optic nerve (with substance loss)

D.Hypoplastic optic nerve

E.Malformation of the optic nerve

a Rare in developed countries.

Adapted from Refs. 3 and 5.

THE DIAGNOSTIC EXAMINATION

Although any child with suspected glaucoma requires a detailed pediatric ophthalmic examination, there are specific goals of the glaucoma-related examination: (a) confirming or excluding the diagnosis of glaucoma, (b) determining the cause of the glaucoma (if present), and (c) gathering information (including any prior glaucoma interventions) vital to plan the optimal management. Examination under anesthesia may be avoided if the diagnosis of glaucoma can be confidently excluded (in an infant or young child) or if an older child would benefit from a medication trial. The examination under anesthesia, when it is indicated, provides a one-stop opportunity for more detailed gonioscopy and evaluation of the optic nerve head, as well as measurements of corneal diameter, central corneal thickness, and axial length, immediately followed by any needed surgical intervention.

Vision Testing (Acuity and Visual Fields)

Optimal vision-testing methods will vary with the patient's age and cognitive function. While central, maintained fixation behavior and absent nystagmus are encouraging in infants, older children should perform optotype testing with proper refractive correction. Visual loss in children with glaucoma often results from ocular changes related to glaucoma or from amblyopia in asymmetric cases; visual acuity loss resulting from optic nerve damage represents an unfortunate, often end-stage situation.

Visual field testing, especially quantitative automated static perimetry, often proves challenging for young children and for all children with nystagmus or poor vision. Hence, perimetry rarely makes the diagnosis of glaucoma but serves instead to assess adequacy of control in older children with glaucoma who can perform reliable baseline examination. Visual field assessment is nonetheless worthwhile in all children with glaucoma, because even confrontation visual fields can often verify suspected severe nasal field loss in children with severe glaucoma and poor vision. Children with associated neurologic conditions (e.g., Sturge-Weber syndrome) may have underlying homonymous hemifield loss independent of their glaucoma. Newer, faster testing algorithms may allow younger children to undergo automated (Humphrey) visual field testing more reliably (6) (Fig. 13.9). Frequency-doubling perimetry (see Chapter 5) may also hold promise for screening and following visual fields over time in children with known or suspected glaucoma (7, 8).

External Examination

External examination helps identify evidence of associated abnormalities (e.g., neurofibromatosis, facial hemangioma), buphthalmos (especially asymmetry between the eyes), photophobia, or nasolacrimal obstruction. Overall assessment of the child's health and systemic features can also provide clues to a glaucoma diagnosis (e.g., facial features suggesting metabolic disorders, connective tissue disorders, chromosomal abnormalities). Occasionally, the ophthalmologist may be the first to suspect the systemic condition related to the ocular abnormality being examined (e.g., oculocerebrorenal or Lowe syndrome, neurofibromatosis).

Corneal Examination

This portion of the examination assesses the cornea for glaucoma-induced changes such as enlargement, edema, and scarring. Other abnormalities, if present, may also suggest coexisting ocular abnormalities (as with developmental glaucomas such as Axenfeld-Rieger or Peters, as discussed in Chapter 14). P.211

Figure 13.9 Humphrey visual field testing demonstrates an inferior arcuate scotoma in the left eye of this 11-year-old with juvenile open-angle glaucoma, who presented with severe optic nerve cupping and had suc cessful control of glaucoma with mitomycin C-augmented trabeculectomy.

The healthy newborn's cornea has a horizontal diameter ranging from 9.5 to 10.5 mm, which enlarges by about 0.5 to 1.0 mm in the first year of life (9, 10 and 11) (Table 13.3). Distention of the globe in response to elevated IOP (buphthalmos) leads to enlargement of the cornea, especially at the corneoscleral junction. A corneal diameter larger than 12 mm in the first year of life is a highly suspect finding. Asymmetry in diameter between the two corneas or a corneal diameter of 13 mm or more at any age strongly suggests abnormality (3). Corneal enlargement is more obvious in asymmetric cases (Fig. 13.1). Simple inspection of the corneas will often identify asymmetric corneal diameters of as little as 0.25 mm, likely because of the examiner's assessment of corneal area (rather than its diameter) by visual inspection. Corneal diameters can be measured by using a millimeter ruler held in the frontal plane in the office, or by calipers in the anesthetized state.

Table 13.3 Corneal Diameter in Children: Healthy and Glaucomatous Eyesa Corneal Diameter, mm

aData are from Refs. 9 and 10.

Acute, severe IOP elevation produces corneal enlargement in the newborn or infant, frequently accompanied by tears in the Descemet membrane (Haab striae). These often appear acutely as areas of increased corneal edema and clouding (3) (Figs. 13.5 and 13.6). In more advanced cases, dense opacification of the corneal stroma may persist despite IOP reduction (Fig. 13.10). In contrast, moderate IOP elevation insufficient to produce noticeable corneal opacity gradually enlarges the infant's corneas, sometimes proceeding unnoticed if symmetric, while concurrent optic nerve damage progresses to severe degrees (Fig. 13.8).

Tonometry (Intraocular Pressure Measurement)

Although IOP assessment in children with suspected or known glaucoma remains critical to their diagnosis and effective management, tonometry often presents challenges in the young

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patient. The best IOP measurements are those obtained in a calm child in the office setting, because IOP may be falsely elevated in a struggling patient and is often unpredictably altered by systemic sedatives and anesthetics (Table 13.5). A sleepy or hungry infant often permits tonometry while taking a bottle in his or her caregiver's arms.

Figure 13.10 A 9-month-old boy with congenital glaucoma and residual corneal scarring from Haab striae, despite successful IOP control with angle surgery.

Although various instruments have been used for IOP measurement in children, the Perkins applanation tonometer and the Tono-Pen (i.e., a handheld Mackay-Marg-type tonometer) rank highly in terms of

accuracy and ease of use in these patients (12, 13, 14 and 15). Children as young as 3 or 4 years of age can often cooperate with Goldmann applanation tonometry (Freedman S, personal observation). The Icare tonometer (Icare Finland, Helsinki), a relatively new handheld device, records IOP in awake patients without requiring topical anesthetic and has a tiny tip that advances easily between the lids of a normally blinking child. Published reports of this rebound tonometer have shown the Icare similar in accuracy to the Tono-Pen and comparable with Goldmann tonometry for IOPs over a reasonable range in adults (Chapter 2) (Fig. 13.11). Icare was reported to be comfortable and highly reproducible for tonometry in healthy school-aged children (16). The Icare tonometer has already proven valuable as a screening tool in children and will probably allow IOP assessment in many infants and children previously requiring anesthetic examination. Home tonometry in children suspected of having large diurnal IOP variation is possible with this instrument (Freedman S, unpublished data).

The pneumatonometer (see also Chapter 2), although cumbersome to use on children in the office setting, often serves as a confirmatory technique to Tono-Pen or Perkins tonometry during examination under anesthesia. This tonometer may be particularly helpful in settings where an opaque or scarring corneal surface precludes useful measurement using handheld instruments; often the readings are several millimeters of mercury higher by pneumotonometry than by applanation. Schiötz indentation tonometry is not recommended for use in eyes with childhood glaucoma, even in the operating room, because of its tendency to underestimate IOP in these eyes (David Walton, MD, personal communication).

Figure 13.11 Icare tonometry being performed in the right eye of a 13-year-old boy 1 day after glaucoma drainage-device surgery for aphakic glaucoma.

The normal IOP in childhood, ranging from about 10 to 22 mm Hg depending on the tonometer and reported pediatric population (3), rises from infancy to reach normal adult levels by middle childhood (17) (Table 13.4).

IOP measurements are variably lowered by the use of sedatives, narcotics, and inhalation anesthetic agents (18, 19 and 20), and elevated by endotracheal intubation (3) (Table 13.5). Ketamine anesthesia, previously reported to elevate IOP (21), has recently compared favorably with sevoflurane anesthesia in terms of minimally altering measured IOP over several minutes after induction (22). Chloral hydrate conscious sedation, effective only in small children and with careful monitoring, reportedly minimally affects awake IOP readings (23). Although IOP measurements taken in a sedated or anesthetic state are

often less reliable than those recorded in a calm, awake child, high preoperative IOP measurements generally remain in an abnormal range, and asymmetric IOPs between the two eyes usually remain so and often signal abnormality. Special care must be taken to avoid spuriously high IOP measured in the anesthetized child who is in laryngospasm, or “ligh t” with eyes rolled upward or downward compared with the midline.

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a Values obtained by using a noncontact tonometer (Keeler Pulsair, Keeler Ltd., Windsor, Berks, UK). IOP values for children vary widely, depending on the type of instrument used. IOP, intraocular pressure. Adapted from Ref. 17.

Table 13.5 Intraocular Pressure Effects of Selected Sedatives and Anesthetic Agents Sedative/Anesthetic Agents/Related

Anterior Segment Examination (Biomicroscopy)

Anterior segment findings provide key information in the evaluation of the pediatric glaucoma patient. As noted earlier, simple inspection of the child's eyes often assists in overall assessment of the corneal size, symmetry, and clarity. Biomicroscopy (optimally with a handheld slitlamp) adds details of corneal architecture and affords improved examination of the corneal details, especially Haab striae. As the IOP is normalized and tears in the Descemet membrane are repaired by endothetial overgrowth, the corneal edema may clear; however, the linear opacities persist, and they are associated with reduced endothelial counts, as viewed by specular microscopy (24), and produce variable permanent scarring and refractive errors. Slitlamp biomicroscopy of the cornea may also demonstrate accompanying findings as clues to the underlying cause of the glaucoma (e.g., posterior embryotoxon in Axenfeld-Rieger syndrome, or

central corneal opacity or corneal adhesions to the iris or lens in Peters anomaly).

The limbus may be dramatically stretched and thinned by ocular stretching in an infant eye with glaucoma, and the anterior chamber often deepens. Abnormalities of the iris and lens may signal primary anomalies or those secondary to other eye diseases (e.g., aniridia, Axenfeld-Rieger syndrome, ectropion uvea).

Gonioscopy

Gonioscopy, providing vital anatomic information about the mechanism of glaucoma in a given eye, can be performed in the office or under anesthesia. Indirect gonioscopy with a Zeiss or Sussman gonioprism proves simple to perform at the slitlamp in the older child, whereas Koeppe (direct) gonioscopy is useful for infants and in the operating room, facilitating detailed inspection of the iris and angle structures (and optic nerve head, by using a direct ophthalmoscope) (Fig. 13.12). In contrast to the healthy adult angle, the healthy infant's angle demonstrates a trabecular meshwork that appears almost as a smooth, homogeneous membrane extending from the peripheral iris to the Schwalbe line. This trabecular meshwork becomes coarser and often increasingly pigmented over time (25, 26). In darkly pigmented individuals, pigmentation of the uveal meshwork with increasing age enhances visibility of this lacy structure. Characteristic features of the child's angle structures help identify eyes with congenital glaucoma of varying severity (see below and Chapter 14). Additional abnormalities present in cases of anterior segment dysgenesis (e.g., aniridia, Axenfeld-Rieger, Peters), aphakic, and secondary glaucomas, for example (for additional details, see Chapter 14).

Figure 13.12 Technique of gonioscopy during examination under anesthesia, performed by using a Koeppe gonioscopy lens and portable slitlamp biomicroscope.

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Taken together with other findings of anterior examination, the adequacy of the angle view and its findings are important guides to the appropriate surgical intervention that may be needed.

Optic Nerve and Fundus Examination

The appearance of the optic nerve head is usually the focus of the fundus examination in an eye with glaucoma, although associated fundus abnormalities may help confirm the glaucoma type (e.g., a stalk in persistent fetal vasculature, foveal hypoplasia in aniridia, or choroidal hemangioma in Sturge-Weber syndrome) or provide useful information for surgical planning (e.g., peripheral retinal pathology or vitreous stranding may suggest vitrectomy and peripheral laser, along with implantation of a glaucoma drainage device, in eyes with aphakia).

Evaluation of the optic nerve head is one of the most important methods for diagnosing childhood glaucoma and for assessing its response to therapy. Indirect ophthalmoscopy with a 28-diopter (D) or 30-D lens may minimize apparent optic nerve head cupping, better appreciated in the older child by using binocular viewing at the slitlamp, or with a 14-D indirect lens or direct ophthalmoscope through a Koeppe gonioscopy lens under anesthesia (which usually affords an adequate view, even with an undilated pupil).

The optic nerve head in healthy newborns is typically pink but may have slight pallor, and a small physiologic cup is usually present (27). The morphology of glaucomatous optic atrophy in childhood resembles that seen in adult eyes, with a preferential loss of neural tissue in the vertical poles (28). In contrast to the adult, however, the scleral canal in children enlarges in response to elevated IOP, especially in the horizontal meridian, causing further enlargement of the cup in addition to that resulting from the actual loss of neural tissue (28).

Cupping of the optic nerve head proceeds more rapidly in infants than in adults and is more likely to be reversible if the pressure is lowered early enough (15, 17, 29, 30, 31, 32, 33 and 34). The cupping appears to be caused by incomplete development of connective tissue in the lamina cribrosa, which allows compression or posterior movement of the optic disc tissue in response to elevated IOP, with an elastic return to normal when the pressure is lowered (32). Dramatic reversal of optic nerve cupping can even occur in older children with glaucoma on sustained lowering of IOP, although significant improvement of visual field loss does not necessarily occur (Fig. 13.13).

Significant optic nerve cup size and asymmetry of cupping between fellow eyes suggest, but do not confirm, glaucoma in an infant. Possible explanations for cupping asymmetry in the absence of IOPrelated changes include asymmetry in the size of the optic canal itself and significant differences in the axial lengths of the two eyes (e.g., in unilateral high myopia or hyperopia).