Ординатура / Офтальмология / Английские материалы / Handbook of Pediatric Strabismus and Amblyopia_Wright, Spiegel, Thompson_2006

surgery.60,70 If the consecutive exotropia increases in sidegaze or is associated with an adduction deficit, consider the possibility of a slipped muscle or stretched scar. Explore the medial rectus muscles if there is a question of muscle stability, as a stretched scar or slipped medial rectus muscle is fairly common. For the advancement procedure, this author now prefers a nonabsorbable suture or a long-lasting absorbable suture. The treatment of choice for a consecutive exotropia without a slipped muscle is bilateral lateral rectus recessions.

Residual Esotropia

A residual esotropia greater than 10 to 15 PD that persists longer than 6 to 8 weeks after surgery should be treated. The first line of treatment is to give the full hypermetropic spectacle correction if the cycloplegic refraction is 1.50 or more. If there continues to be a significant esotropia after glasses are prescribed or there is not enough hypermetropia to warrant glasses, then surgery should be considered, especially if the child is under 2 years of age and there is fusion potential. If the initial recession was 5.0 mm or less, this author prefers a rerecession of one or both of the medial rectus muscles. A bilateral 2-mm re-recession corrects roughly 20 to 25 PD of residual esotropia. Patients with residual esotropia and initial recessions greater than 5.0 mm should be managed with lateral rectus resections, doing slightly less than described on the standard charts. Because a previously recessed medial rectus muscle is being resected, remember to do a slightly smaller resection to avoid an overcorrection. An alternative to surgery in cases of small residual esotropia is prescribing base-out prism glasses.

The Role of Botulinum Toxin

In addition to surgery, some have advocated the use of botulinum for the treatment of congenital esotropia. The theoretical advantage would be to create an incomitant deviation so the patient could adopt a face turn and obtain fusion. Although this has theoretical merit, there are some problems involved with the use of botulinum. These complications include secondary ptosis, initial consecutive exotropia lasting up to 2 to 3 months, and the temporary effect of the botulin injection itself. Most studies have shown that multiple injections are needed to sustain the effect.43 Even with multiple injections, alignment

of a deviation is variable and is typically smaller than congenital esotropia, usually measuring between 20 and 40 PD. Cycloplegic refraction reveals hypermetropia between 1.50 and6.50 diopters. Parents often give a history that the eyes are straight some of the time; however, when the child is tired or focusing at near, the eyes will cross. The esotropia is initially intermittent but may quickly increase to become a constant deviation. Patients with constant esotropia may lose fusion potential and are prone to develop amblyopia.

Cycloplegic Refraction

An accurate cycloplegic refraction is required to determine the full hypermetropic correction. Young children are often difficult to refract, and repeat cycloplegic refractions help ensure accuracy. Cyclopentolate is the standard cycloplegic agent. Cyclopentolate is given topically, one or two doses for a lightly pigmented iris, and two or three doses for a dark iris. Consider using atropine in patients with a darkly pigmented iris who show variable retinoscopy readings. The refraction is performed 30 min after the last dose. Atropine is given twice a day for 3 days, and the refraction is done on the third day. The mydriatic effect of these drugs lasts much longer than the cycloplegic effect, so a dilated pupil does not mean complete cycloplegia.

Treatment

The first step in the treatment of hypermetropic accommodative esotropia is to prescribe the full hypermetropic correction (see example, following). In both juvenile-onset and infantileonset accommodative esotropia, full hypermetropic correction should be prescribed as soon as the esotropia is identified, even giving glasses to children as young as 2 months of age (Fig. 7-11). Delay in treatment can result in loss of binocular potential.25

Example 1. 2-year-old with esotropia for 2 months Full ductions and versions

Cycloplegic refraction 4.50 OU

Treatment: Prescribe spectacles 4.50 sphere OU

A

B

FIGURE 7-11A,B. (A) Three-month-old infant with a 35 PD esotropia and3.00 D refractive error. (B) Infant now with straight eyes wearing full hypermetropic correction.

It is important that the child wears the optical correction fulltime. Children who intermittently remove their glasses will not relax their accommodation and will have blurred vision with their appropriate hypermetropic correction. For children who have difficulty relaxing accommodation and therefore do not

accept their hypermetropic correction, it may be helpful to prescribe a short course of cycloplegics such as atropine or cyclopentolate. Parents should be told that the glasses are prescribed to straighten the eyes by relaxing the overfocusing caused by the farsightedness.

If, after prescribing full hypermetropic correction, the eyes are straightened to within 10 PD distance and near and the patient obtains binocular fusion, nothing more need be done but continue with the full hypermetropic correction. Some advocate reducing the plus lens until an esophoria is induced; to try to build fusional divergence and wean the child from glasses. This author has not seen this practice reduce the need for spectacles but, all too frequently, has seen it turn a well-controlled deviation into a manifest esotropia. By reducing the plus, you run the risk of producing a manifest esotropia and losing binocular fusion. Remember, children with accommodative esotropia have tenuous fusion. To establish binocular function, the goal must be to align the eyes to orthotropia.

If, after wearing full hypermetropic spectacles for 4 to 8 weeks, a residual esotropia of more than 10 PD is present for distance and near (the patient is not fusing), then surgery is indicated. This residual deviation is termed partially accommodative esotropia (discussed later in this chapter). In some cases, the full hypermetropic correction will align the eyes for distance; however, a residual esotropia will persist at near. These patients have a high AC/A ratio, and bifocals are indicated (see Prescribing Bifocals below).

High AC/A Ratio Esotropia

A subgroup of patients with accommodative esotropia will have a high AC/A ratio and have a significantly larger esotropia at near. High AC/A ratio esotropia usually occurs in patients with hypermetropia but may occur in patients with myopia or no refractive error. If the eyes are straight in the distance ( 10 PD), a bifocal add is given to correct the near deviation and promote near fusion.

Example 2. 4-year-old with esotropia for 2 months Full ductions and versions

Cycloplegic refraction 3.50 OU

(phoria—fusing)

Treatment: Prescribe bifocals ( 3.50 sphere upper with 3.00 add, OU)

PRESCRIBING BIFOCALS

A bifocal add is indicated for patients who are fusing in the distance but have an esotropia at near that is large enough to interfere with near fusion ( 10 PD).42 The add will relax near accommodation, thus reducing convergence. If the AC/A ratio is 7 (high), then a 3.00 add will reduce the near esotropia by 21 PD. In the example above, the 3.00 add reduces the residual near deviation (with correction) to an esophoria of 3 PD, allowing for binocular fusion. Usually, start with a maximum near add of 3.00. Over time, the bifocal add can be diminished slowly to promote divergence. Reduce the reading add to produce a small esophoria of no more than 4 to 6 PD, which will stimulate divergence, while maintaining comfortable binocular fusion. In many cases, the bifocal can be eliminated by 10 to 12 years of age. The best bifocal is a flat-top segment that bisects the pupil. A common mistake is to prescribe a low bifocal that a child can easily look over, thus negating the purpose of the bifocal add.

Remember that bifocals will not treat a manifest esotropia in the distance. If a patient has an esotropia in the distance greater than 10 PD with full hypermetropic correction and is not fusing, then surgery is indicated, not bifocals. Bifocals, however, may be needed postoperatively if a near esotropia persists.

Partially Accommodative Esotropia

If, after wearing full hypermetropic correction, a residual esotropia ( 10 PD) for distance and near exists, it is termed partially accommodative esotropia (Fig. 7-12C). The treatment is surgery: bilateral medial rectus muscle recessions.

Example 3. 3-year-old with esotropia for 2 months Full ductions and versions

Cycloplegic refraction 3.50 OU

A

B

FIGURE 7-12A–B. Infantile accommodative esotropia. The patient is the author’s youngest son who had partially accommodative esotropia. (A) At 6 weeks of age, the patient’s eyes were well aligned with normal motility. (B) At 3 months of age, a variable esotropia occurred. Deviation measured between essentially straight and an esotropia of 40 prism diopters.

Treatment: Bilateral medial rectus recessions

E

FIGURE 7-12E. (E) At the time of this writing, patient is 13 years old and is still well aligned with an excellent sensory outcome by Titmus stereoacuity testing showing a positive fly and 3/3 animals (100 s).

After wearing the 3.50 sphere for 6 weeks, the patient in Example 3 still had a significant esotropia (Dcc ET 20, Ncc ET 25). This residual esotropia cannot be fused and should be addressed surgically. Bifocals are not indicated, as they will not correct the distance deviation. Preoperatively, it is important to

rerefract these patients to make sure that all full latent hypermetropia is corrected.

Surgery for Partially Accommodative Esotropia

Bilateral medial rectus recession is the procedure of choice for partially accommodative esotropia. There is, however, controversy regarding how to determine the target angle. Most are now increasing the amount of surgery from the standard approach using augmented surgery or prism adaptation. Below are various formulas used to determine the amount of surgery for partially accommodative esotropia.

STANDARD SURGERY

In Example 3, the standard surgery target angle is ET 20. The standard surgical approach has been to operate for the residual deviation measured with correction in the distance (i.e., standard surgery); however, standard surgery has a high undercorrection rate of approximately 25%. Because of this unacceptably high undercorrection rate, many surgeons are increasing their surgical numbers to correct partially accommodative esotropia. The idea of surgery is not to eliminate hypermetropic correction by overcorrection, but to get the eyes straight and fusing with full hypermetropic correction. Parents should be advised that spectacles will be required postoperatively.

AUGMENTED SURGERY

This author has studied results using a target angle determined by averaging the near deviation with correction and the near deviation without correction. In Example 3, the augmented surgery target angle is 30 PD (35 25/2). Results comparing standard surgery to this augmented surgery formula showed a 26% undercorrection rate for standard surgery, while augmented surgery resulted in a 93% success rate with 7% overcorrection.70 The patients who were overcorrected all had a high AC/A ratio, were well aligned at near, and had an intermittent exotropia in the distance. The augmented surgery formula is based on the near measurement, so it is not surprising that patients with a high AC/A ratio have a tendency for overcorrection in the distance. This author augments surgery as described above if the AC/A ratio is normal; however, if the AC/A ratio is high, average the near deviation without correction (largest deviation) and the