Ординатура / Офтальмология / Английские материалы / Handbook of Pediatric Strabismus and Amblyopia_Wright, Spiegel, Thompson_2006
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distance deviation with correction (smallest deviation), or use prism adaptation. The high AC/A ratio patients are difficult to manage.
PRISM ADAPTATION
Another method for determining the amount of surgical correction in patients with partially accommodative esotropia is using prism adaptation. Prism adaptation consists of prescribing baseout prism for the residual esotropia after prescribing full hypermetropic correction. In Example 3, the initial press-on prism would be 20 PD base-out. The patient returns in approximately 2 weeks after wearing the prisms. If the esotropia has increased, then the prisms are increased. This regimen continues at 1- to 2-week intervals until the deviation has stabilized. The surgeon operates on the full prism-adapted angle as determined by the press-on prisms. Operating on the larger adapted angle reduces the undercorrection rate. Results of a multicenter study on prism adaptation showed that standard surgery resulted in approximately 75% successful correction rate and operating on the prism-adapted angle resulted in an 85% success rate; however, the difficult high AC/A ratio patients were excluded from the study.58 The disadvantage of prism adaptation is the cost and time involved with prescribing press-on prisms and reexamining the patient until the deviation stabilizes.
POSTOPERATIVE CARE
Postoperative care is similar to that described for congenital esotropia. The goal is to achieve binocular fusion, as most patients with acquired strabismus have fusion potential. Patients who are aligned for distance, but have an esotropia greater than 8 to 10 PD at near, may be candidates for bifocals. The vast majority of patients will require hypermetropic correction after surgery. A small consecutive exotropia can be managed by reducing the plus of hypermetropic spectacles, but do not “cut the plus” more than 2.50 diopters as this results in instability of the angle. Large overcorrections are rare but when they occur, they must be managed by surgery.
Miotics
In rare selected patients, miotic drops such as phospholine iodide (i.e., echothiophate iodide) may be indicated to treat
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accommodative esotropia. Miotics, such as phospholine iodide, are cholinesterase inhibitors and increase the effectiveness of locally released acetylcholine. Topical phospholine iodine has a parasympathomimetic effect on the iris sphincter and ciliary muscles, causing miosis and pharmacological accommodation. Acetylcholine released in the ciliary body will last longer and produce more accommodation for a given amount of innervational stimulation. Thus, miotics reduce the accommodative effort necessary to provide a clear retinal image and will reduce the amount of associated reflex convergence. When using miotics, it is preferable to start with a low dose of phospholine iodide, 0.03%, one drop every morning. If this dose is not sufficient to correct the esotropia, the dose may be increased to twice a day or use phospholine iodide 0.125%. Miotics truly reduce the AC/A ratio and esotropia associated with hypermetropia.
Miotics can be tried if the patient has a high AC/A ratio and has minimal hypermetropia. In most cases, however, bifocal spectacles are the treatment of choice. Another indication for the use of miotics is in children who cannot wear spectacles or contact lenses; this is most useful for short periods of time, perhaps during the summer months when children are swimming. Miotics are occasionally used as a diagnostic test to determine if an esotropia will respond to hypermetropic optical correction. If the miotics fail to correct the deviation, this would identify a nonaccommodative component. Unfortunately, the only way to know if spectacles will correct the deviation is to actually prescribe them.
ADVERSE EFFECTS OF MIOTICS
Phospholine iodide, even when given topically, is systemically absorbed and will lower cholinesterase activity in the blood for several weeks,14 which is of significant note for those patients who undergo general anesthesia with succinylcholine. Phospholine iodide prolongs the effect of the succinylcholine and may prolong respiratory paralysis after surgery. Succinylcholine should be avoided if phospholine iodide has been used within 6 weeks before surgery. Systemic side effects of miotics may include brow ache, headaches, nausea, and abdominal cramping. If the lower dose of phospholine iodide is used, these complications are infrequent.
Ocular side effects of phospholine iodide include iris cysts along the pupillary margin in 20% to 50% of cases, occurring at
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any time from several weeks to several months after treatment. Iris cysts tend to regress after discontinuing phospholine iodide; however, this author has seen persistent iris cysts several years after stopping phospholine iodide therapy. Phenylephrine used in combination with phospholine iodide may prevent iris cysts. Other rare and unusual complications include lens opacities, retinal detachment in adults, and angle-closure glaucoma.
INFANTILE ACCOMMODATIVE ESOTROPIA
Infantile accommodative esotropia occurs during the first year of life. The key to diagnosing infantile accommodative esotropia is noting the presence of hypermetropia ( 2.00) and a variableangle esotropia at the onset.4,56 Treatment is to immediately prescribe the full hypermetropic correction, as determined by a good cycloplegic refraction, and treat amblyopia if present (see Fig. 7-11).18 If spectacles do not align the eyes to within 8 to 10 PD, then strabismus surgery is indicated (see Partially Accommodative Esotropia, discussed previously). The child should wear spectacles for at least 4 weeks before going to surgery. Approximately half of diagnosed patients will be corrected with spectacles alone, and half will require spectacles along with surgery (see Treatment of Partially Accommodative Esotropia, discussed previously). This author is personally very familiar with this disorder, as his youngest son developed partially accommodative esotropia that did not respond to full hypermetropic correction at 4 months of age. The author operated on his son at 6 months of age using the augmented surgery formula (Fig. 7-12). Now, at 13 years of age, he has done well with just the one surgery, having straight eyes and high-grade stereoacuity.
The prognosis for binocular fusion in patients with accommodative esotropia is quite good, as these patients have acquired strabismus. The treatment goal for accommodative esotropia is establishing binocular fusion and stereopsis.
ACQUIRED NONACCOMMODATIVE ESOTROPIA
Uncommonly, esotropia is acquired during childhood or even adulthood without significant hypermetropia. Initially, these deviations are variable and intermittent. Over time (weeks,
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months, or even years), however, the esodeviation may become constant. It is important in these cases of acquired esotropia to rule out the possibility of an intracranial tumor, Arnold–Chiari malformation, or other neurological processes such as myasthenia gravis. A divergence paralysis pattern with a larger esotropia in the distance than at near is a red flag to the possibility of a mild sixth nerve paresis and a neurological disorder.
The treatment for acquired nonaccommodative esotropia is usually surgery, and the prognosis for re-establishing binocular fusion is relatively good. Undercorrections are frequent in this group, and prism adaptation will help reduce the number of patients with a residual esotropia.
ESOPHORIA
Small esophorias (8–10 PD) can cause significant asthenopic symptoms. These patients usually complain of headaches and fatigue when reading for long periods of time. Small esophorias are best treated with hypermetropic correction for near esophorias, or base-out prisms if the deviation is present for distance and near. A reading add relaxes accommodation and convergence, thus correcting the esophoria. Base-out prisms are very effective; however, patients tend to adapt to the prisms and require increasing prisms over time. When prescribing prisms, prescribe just enough for comfortable fusion but slightly less than the full deviation to stimulate divergence. In cases of a large esophoria, surgery may be required. In these cases, it is helpful to use prism adaptation to disclose the full underlying esophoria. In any case of a symptomatic esophoria, a cycloplegic refraction is indicated, as latent hypermetropia is a common cause for an acquired esodeviation.
ESOTROPIA, NYSTAGMUS, AND
FACE TURN
Nystagmus may occur with esotropia. These patients often adopt a face turn to damp the nystagmus and improve visual acuity. Specific types of esotropia, nystagmus, and face turn syndromes include (1) manifest latent nystagmus, (2) congenital nystagmus with constant esotropia, and (3) nystagmus compen-
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sation syndrome. In these cases, the face turn is used to position the fixing eye at the null point to improve vision. In the case of manifest latent nystagmus and nystagmus compensation syndrome, the null point is always in adduction. Consequently, the fixing eye in these cases is always adducted and the face turn is toward the side of the fixing eye (Fig. 7-13). Ciancia’s syndrome (see Fig. 7-5 and Congenital Esotropia, discussed previously) is often placed in this category; however, the cause for the face turn is tight medial rectus muscles, not nystagmus and a null point.
FIGURE 7-13. Esotropia, nystagmus, and face turn. Drawing shows that the null point of the nystagmus is in adduction, so the patient adopts a face turn to the right to place the fixing right eye in adduction. Note that the face turn is to the same side as the fixing eye.
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Manifest Latent Nystagmus
Latent nystagmus (see p. 225) that spontaneously becomes manifest without monocular occlusion is called manifest latent nystagmus. The null point for manifest latent nystagmus is always in adduction. Patients with strabismus and manifest latent nystagmus will place the fixing eye in adduction to improve vision; this produces a face turn to the side of the fixing eye.23 Patients with intermittent strabismus and latent nystagmus will not manifest the nystagmus when they are aligned and fusing. At these times, the patient has straight eyes or a microtropia and fusion, so the latent nystagmus is controlled, and there is no face turn. Other times (e.g., when the patient is fatigued), the phoria breaks down to a tropia and loss of fusion. Loss of peripheral fusion changes the latent nystagmus to a manifest latent nystagmus. This causes the patient to adopt a face turn to place the fixing eye at the null point that is in adduction (Fig. 7-14).
The treatment of manifest latent nystagmus with face turn is to enhance binocular fusion in order to avoid the tropia phase. Methods for enhancing binocular fusion in patients with esotropia include providing hypermetropic correction in patients with an accommodative component or operating for the residual esodeviation. In the article by Zubcov et al.,73 five patients with esotropia and manifest latent nystagmus underwent strabismus surgery resulting in straight eyes; this converted the manifest latent nystagmus to latent nystagmus. Four of the five patients also showed improvement in binocular visual acuity because of the improved nystagmus.
Congenital Nystagmus with Constant Esotropia
Patients with congenital nystagmus may have an associated esotropia. These patients commonly adopt a face turn to place the fixing eye at the null point. The null point in congenital nystagmus may be in any gaze position. If the null point is in adduction, with the right eye fixing, the face turn will be to the right. Null point in abduction causes the fixing eye to abduct, and then the face turn is to the left. A vertical null point position causes a compensatory chin depression or chin elevation. Obviously, there is no face turn if the null point is in primary position.
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A
B
FIGURE 7-14A,B. Manifest latent nystagmus. Patient with Down’s syndrome and previous surgery for congenital esotropia. Patient now has an intermittent esotropia with peripheral fusion and monofixation syndrome. (A) Patient is fusing with a microesotropia. There is an underlying latent nystagmus that is controlled because the patient is fusing. Note that there is no face turn. (B) Now the patient has esotropia, which disrupts fusion and changes the latent nystagmus into a manifest latent nystagmus. The null point of manifest latent nystagmus is in adduction, so the fixing eye (the right eye) moves into adduction. The patient has developed a face turn to the right. Note the positive Brückner reflex with the brighter red reflex in the deviated left eye.
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Congenital nystagmus is a jerk, or pendular, nystagmus. The characteristics of congenital nystagmus are different from manifest latent nystagmus. With congenital nystagmus, there is an increasing velocity of the slow phase and no change in the nystagmus on unilateral occlusion or binocular dissociation. The nystagmus switches direction on sidegaze with the fast phase to the right in rightgaze and the fast phase to the left in leftgaze. Congenital nystagmus and latent, or manifest, nystagmus can occur concurrently.
The treatment for the face turn with esotropia is strabismus surgery to move the null point of the fixing eye to primary position. Then, if necessary, move the nonfixing eye to match. For example, if there is a right esotropia of 40 PD (20°), right eye fixing in adduction with a face turn to the right 20° (see Fig. 7-13), recess the right medial rectus and resect the right lateral rectus; this will move the right eye to primary position and correct the face turn and the esotropia at the same time (also see Chapter 10).
Nystagmus Compensation Syndrome
(Nystagmus Blockage Syndrome)
Some patients with congenital nystagmus and straight eyes may use accommodative convergence to damp their nystagmus. In rare circumstances, this can produce an esotropia. Previously, this rare syndrome has been termed nystagmus blockage syndrome or nystagmus compensation syndrome.66 These patients present with straight eyes and congenital nystagmus. On viewing near targets, they manifest a variable esodeviation while using accommodative convergence to damp the nystagmus and improve vision. Key observations include variable-angle intermittent esotropia only at near, and pupillary miosis that occurs with the esotropia (Fig. 7-15). Many patients who have been previously reported in the literature as having nystagmus blockage syndrome or nystagmus compensation syndrome actually had manifest latent nystagmus. Some have doubted the existence of congenital nystagmus with accommodative convergence causing esotropia; however, von Noorden66 has documented this syndrome with EOG recordings. Currently, a good surgical treatment for this esotropia at near does not exist. However, von Noorden has suggested a small medial rectus recession with Faden (posterior fixation suture).
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A
FIGURE 7-15A,B. (A) Nystagmus compensation syndrome. Top photograph: patient with congenital nystagmus, straight eyes, and middilated pupils. Bottom photograph: patient trying to read a near target. When patient tries to read the near target, the patient invokes accommodative convergence to damp the nystagmus and an esotropia occurs. Visual acuity improves to 20/40 at near. (Photograph courtesy of G.K. von Noorden.) (B) Electro-oculograph of a patient with congenital nystagmus and nystagmus compensation syndrome. At the beginning of the tracing, the congenital nystagmus shows large amplitude and visual acuity is 20/100. The patient then uses accommodative convergence to damp the nystagmus, an esotropia occurs, and visual acuity improves to 20/40 at near. The amplitude of the nystagmus increases as patient relaxes accommodative convergence and the congenital nystagmus recurs. (From Ref. 67, with permission.)
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CYCLIC ESOTROPIA
Cyclic esotropia is a very rare type of esotropia, with most pediatric ophthalmologists only seeing one or two cases in their entire career. This is an acquired esotropia that occurs at virtually any age, but most frequently between 2 and 6 years of age. These patients usually cycle between straight eyes and esotropia every 24 to 48 h; however, the interval may vary. To help establish a pattern, ask the parents to record on a calendar when the eyes are crossed versus the days when the eyes are straight. When the eyes are aligned, the patient has good binocular vision and stereoacuity. Cyclic esotropia is usually progressive and, in most cases, the esodeviation finally becomes constant over several months to years. Some cases of cyclic esotropia are associated with hypermetropia and, in these cases, the full cycloplegic correction should be given. Patients in whom there is no significant hypermetropia, surgery for the full deviation should be performed to provide appropriate eye alignment and preserve binocularity and fusion.13,29 Sporadic cases associated with sixth nerve palsy or central nervous system disease have also been reported.34,54
DIVERGENCE INSUFFICIENCY
Divergence insufficiency causes an esodeviation that is greater in the distance than at near and can occur, idiopathically, as a primary strabismus. An important cause for divergence insufficiency is divergence paralysis secondary to a mild sixth nerve palsy that causes an esodeviation in the distance. An acquired esodeviation with a divergence paresis pattern is a red flag for possible neurological disease. Divergence paresis has been associated with pontine tumor, head trauma, myasthenia gravis, and Arnold–Chiari malformation. Neuroimaging studies as well as a neurological consultation are indicated to rule out possible neurological disease.
SENSORY ESOTROPIA
Sensory esotropia is an esotropia occurring secondary to unilateral blindness. It has been the general teaching that, if the vision loss occurred before 2 years of age, the patient will develop