Ординатура / Офтальмология / Английские материалы / Handbook of Pediatric Strabismus and Amblyopia_Wright, Spiegel, Thompson_2006
.pdf
232 |
HANDBOOK OF PEDIATRIC STRABISMUS AND AMBLYOPIA |
genital fibrosis syndrome may cause virtually any horizontal or vertical strabismus and is associated with extremely tight fibrotic rectus muscles on forced duction testing. It frequently presents as a large-angle congenital esotropia with severe limitation of abduction of one or both eyes; this has also been termed strabismus fixus. Even though abduction is severely restricted, OKN stimulus or the doll’s head maneuver will show abduction saccadic eye movements of brisk, albeit small, amplitudes, indicating intact lateral rectus function.
Treatment of Congenital Esotropia
The treatment of congenital esotropia (ET) is usually surgical. Occasionally, infants with esotropia may be corrected with hypermetropic spectacle correction. Spectacles should be tried in small-angle cases (ET 40) if hypermetropia is 2.00 or greater and in patients with large-angle esotropia ( 40 PD) if the hypermetropic correction is 3.00 or more. Birch et al.8 reported that 3 of 84 infants with esotropia of at least 30 PD seen at 2 to 4 months of age achieved alignment with spectacle correction and required no surgery.
It is important to fully treat amblyopia before performing surgery, with the endpoint of patching being “holds fixation well” with either eye by fixation preference testing. If the child is cosmetically straightened by the surgery, the parents may consider that the problem is cured and they may not return for amblyopia treatment. The only situation when surgery is indicated in the face of residual amblyopia is a tight medial rectus muscle that causes one eye to be buried in the medial canthus even when the good eye is patched as this blocks the vision of the amblyopic eye and makes effective amblyopia therapy impossible. This unusual problem most frequently occurs in association with strabismus fixus of congenital fibrosis syndrome or, rarely, Ciancia’s syndrome.
The standard surgical approach is bilateral medial rectus recessions using the standard surgical charts (see endpapers). The amount of recession is usually based on the near deviation as it is difficult to obtain accurate distance measurements in infants. In young infants with fusion potential, a small postoperative exodeviation is probably desirable to allow fusional convergence to align the eyes.60 In older patients with irreversible significant amblyopia, limit surgery to the amblyopic
CHAPTER 7: ESODEVIATIONS |
233 |
eye by performing a recession of the medial rectus muscle and a resection of the lateral rectus muscle.
PROGNOSIS AND TIMING OF SURGERY
There are few long-term outcome studies on congenital esotropia and these are retrospective.30,31,61 Historically, alignment and sensory outcomes for patients have been poor using the standard approach of operating late between 6 months to 2 years of age. Except for rare cases, the best results with standard surgery have been monofixation with peripheral fusion and only gross stereopsis. Monofixation and peripheral fusion, however, do not guarantee long-term stability, as many patients will lose binocular fusion over time.3,63
There is growing evidence that outcomes from surgery for infantile esotropia can be improved by early intervention to align the eyes as soon the diagnosis is firmly established, even operating before 6 months of age. The best time to operate on infantile esotropia remains controversial.11,17,30,62,71
At the time of this printing, this author suggests operating for infantile esotropia as early as 12 to 13 weeks of age, so long as the esotropia is a constant tropia greater than 40 PD and there have been two examinations (3–4 weeks apart) documenting that the deviation is stable or increasing. Infants with small to moderate deviations, intermittent deviations, or variable-angle esotropia are observed until 6 months of age or longer. CEOS data show that these patients have a significant rate of spontaneous resolution. In infants under 5 months of age, this author performs bilateral medial rectus recessions using the standard tables, with a maximum recession of 6.0 to 6.5 mm posterior to the medial rectus muscle insertion.
RATIONALE FOR EARLY SURGERY
The rationale for performing early surgery for infantile esotropia is derived from basic science research and clinical studies. Hubel and Wiesel were among the first to show that strabismus occurring during the early period of visual development causes permanent loss of binocular cortical cells and disruption of binocular visual development.33 Studies by Crawford and von Noorden21,22 and Crawford et al.20 have shown that as little as 3 weeks of prism-induced esotropia will cause permanent loss of binocular cells and stereopsis in infant monkeys. Importantly,
234 |
HANDBOOK OF PEDIATRIC STRABISMUS AND AMBLYOPIA |
A
B
FIGURE 7-6A,B. Chart from the study by Crawford and von Noorden21,22 shows the results of prism-induced esotropia in infant monkeys. Column A shows the normal distribution of occipital cortex with the largest spike in the center representing binocular cells (B) and fewer monocular cells (R, right eye; L, left eye). Columns B through E represent the cortical cell distribution after increasing duration of prism-induced esotropia. Note that after only 20 days of prism-induced esotropia (column C), almost all the binocular cortical cells are gone and there is a corresponding increase in monocular cells. Column F plots the binocular cell loss over time from prism-induced esotropia and shows an inverse relationship, with longer duration of esotropia corresponding to fewer binocular cells.
loss of binocular cells after brief periods of prism-induced esotropia persisted after removing the prisms, even after allowing up to 3 years for recovery. These studies also demonstrated that the loss of binocularity is directly proportional to the duration of the esotropia (Fig. 7-6).
CHAPTER 7: ESODEVIATIONS |
235 |
In humans, the critical period for the development of binocular vision appears to be the first 3 to 4 months of life.6,12,25,41,71 Stereopsis develops rapidly and is nearly completed in infancy.6,41,53 Birch and Stager10 have demonstrated that, by 5 months of age, about 40% of esotropes corrected with prisms had stereopsis, similar to that found in infants of this age with normal visual development. After 5 months of age, only about 20% of the early-onset esotropes demonstrated stereopsis, in contrast to 100% of normal infants. The timetable for the development of binocular fusion may be even earlier, as this author has personally seen compensatory head posturing and a gaze preference associated with incomitant strabismus in infants as young as 3 weeks, thus indicating the presence of binocular fusion. It is likely that stereoacuity improved with increasing visual experience as visual acuity improved.
Clinical studies clearly indicate that early surgery before 1 to 2 years of age is critical to obtaining some binocular fusion, at least peripheral fusion. Ing,35 in a landmark article, demonstrated the importance of early surgery, reporting that approximately 80% of congenital esotropic patients achieved peripheral fusion if aligned before 2 years of age. In contrast, patients aligned after 2 years of age had less than 20% chance of obtaining any fusion. In addition to being a consummate clinician scientist, Dr. Ing is a champion surfer (Fig. 7-7).
More recent studies indicate that surgery performed before 1 year of age results in even better binocular function and estab-
FIGURE 7-7. Photograph of Dr. Malcolm Ing surfing at his home in Hawaii with Diamond Head in the background. Dr. Ing’s landmark work on early surgery for congenital esotropia has made a tremendous improvement in the care of our patients.
236 |
HANDBOOK OF PEDIATRIC STRABISMUS AND AMBLYOPIA |
lishes random dot stereoacuity.40,50,99 Very early surgery, that is, before 6 months of age, remains controversial, but it appears to be safe and may provide the best sensory outcomes.30,71 Helveston et al.30 reported results on 10 infants operated for infantile esotropia between 12 and 23 weeks of age. All achieved a final alignment within 10 PD of orthotropia, although many required reoperation, as the follow-up was as long as 10 years. Four patients obtained stereoacuity, 1 with 140 s arc. In 1994, this author reported results of very early surgery on 7 infants operated between 13 and 19 weeks of age with a follow-up of 2 to 8 years (mean, 4.1 years). All had excellent alignment at the final visit with a tropia of 8 PD or less. Five of the 7 required only one operation to obtain good alignment, and 2 required one reoperation. Five children could cooperate with stereo testing at the outcome examination and all 5 showed stereoacuity ranging from 400 to 40 s arc. Three children achieved high-grade stereoacuity by random dot testing and 2 had 40 s arc. Figures 7-8 and 7-9 show preand postoperative photographs of the two patients who obtained 40 s arc stereoacuity after very early surgery.
The basic science data and clinical studies suggest that many patients with infantile esotropia do have the potential for
A
FIGURE 7-8A. Early surgery for congenital esotropia patient. (A) Photograph of 1-week-old infant with congenital esotropia. Patient’s grandfather is a physician and noted esotropia at birth.
CHAPTER 7: ESODEVIATIONS |
237 |
B
C
FIGURE 7-8B–C. (B) Surgery was performed at 13 weeks of age. Photograph taken 1 day after bilateral medial rectus recessions, 6.0 mm, showing consecutive exotropia. The exotropia was intermittent and resolved a few days after surgery. (C) Same patient at 5 years of age. Early surgery resulted in excellent alignment with best binocular sensory result ever reported. The patient has now been followed for more than 7 years with straight eyes, no dissociated vertical deviation, no latent nystagmus, and no inferior oblique overaction; fusion of Worth 4-dot in the distance and near, 40 s of stereo by Titmus testing, and Randot stereopsis. The only binocular functional defect is trace optokinetic nystagmus (OKN) asymmetry seen only by electro-oculogram (EOG) recording; no OKN asymmetry is seen clinically.
238 |
HANDBOOK OF PEDIATRIC STRABISMUS AND AMBLYOPIA |
A
B
FIGURE 7-9A–B. Early surgery for congenital esotropia patient. (A) Preoperative photograph of patient with infantile esotropia at 19 weeks of age. (B) Postoperative day 1 with a consecutive exotropia; this was intermittent and lasted only a day or two.
CHAPTER 7: ESODEVIATIONS |
239 |
C
D
FIGURE 7-9C–D. (C) Photograph taken at age 8 years. Patient had 40 s stereoacuity, with slight intermittent exotropia. One year later, patient underwent bilateral lateral rectus recessions for an exotropia. (D) At a recent follow-up visit at 14 years of age, patient maintains excellent alignment and 40 s stereoacuity after early surgery for infantile esotropia.
240 |
HANDBOOK OF PEDIATRIC STRABISMUS AND AMBLYOPIA |
stereopsis if surgically aligned early, prior to 1 year of age. In addition, very early surgery, before 6 months and even as young as 3 months of age, appears to be safe and may be of critical importance for establishing a high level of binocular fusion and stereopsis. It is likely that an important factor is to reduce the duration of the esotropia.
GOOD STEREOPSIS WITH LATE SURGERY
As already described, basic science research in nonhuman primates has demonstrated that brief periods of strabismus (as little as 3–4 weeks) during the neonatal period will permanently disrupt binocular function. Despite these studies, there have been sporadic cases of infantile esotropia that demonstrated stereoacuity following “late” surgery, even in adulthood (Fig. 7-10).45 In fact, two patients in Ing’s 1981 study35 achieved 40 s arc stereoacuity even though the eyes were surgically aligned after 1 year of age. It is likely that some infants who are classified as having early-onset esotropia actually have straight eyes or intermittent esotropia during the first few months of life, probably establishing binocular cortical cells needed for fusion. Perhaps, once established in early infancy, binocularity may be reestablished later in life when the eyes are aligned after strabismus surgery. Because some patients with presumed congenital-onset esotropia achieve binocular fusion after late surgery, we should not categorically assume an older patient with esotropia does not have fusion potential.
POSTOPERATIVE CARE
All patients with congenital esotropia should be followed closely for amblyopia, even if good motor alignment is achieved. The goal of surgery is to obtain alignment within 8 to 10 PD of orthotropia to allow for the establishment of peripheral fusion and the monofixation syndrome. Deviations larger than 10 PD preclude the development of even peripheral fusion. Postoperative tropias greater than 10 PD should be treated with either further surgery or spectacle correction.
Consecutive Exotropia
An initial small-angle exotropia is probably desirable in infants young enough to have fusion potential; however, a persistent exotropia 4 to 6 weeks after surgery may require additional
CHAPTER 7: ESODEVIATIONS |
241 |
A
B
FIGURE 7-10A,B. (A) Preoperative photograph of teenager with a largeangle esotropia that mother thinks was present since birth. Patient had no previous surgery. (B) Postoperatively after bilateral medial rectus recessions, the patient achieved excellent alignment, and peripheral fusion with gross stereoacuity. Old records revealed the patient to be hypermetropic, and the patient probably had an intermittent esotropia acquired during late infancy. If fusion is established in infancy, it is often retrievable later, in contrast to a constant congenital esotropia, which has a poor prognosis for fusion if alignment is delayed.