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When to treat, when to refer pediatric strabismus
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At the American Academy of Optometry's December meeting in Orlando, Primary Care Optometry News organized a round-table discussion on the topic of pediatric strabismus. Four experts discussed the prevalence of the condition; how primary care optometrists should evaluate various cases; what cases can be treated in the primary care practitioner's office; which cases should be sent to specialists; clinical pearls for diagnosis; and the upper level of therapy. Panelists included: Michael Bartiss, OD, MD; Jeffrey Cooper, OD; Kelly A. Frantz, OD; and Paulette P. Schmidt, OD, MS.
Primary Care Optometry News: What is the prevalence of pediatric strabismus?
Paulette P. Schmidt, OD, MS: The literature we reviewed for our grant is fairly current, and we've found rates of 2% to 4%.
Jeffrey Cooper, OD: The ratio is reported to be one exotrope for every three esotropes. The average optometrist isn't seeing those numbers because pediatric ophthalmologists are holding on to patients longer and have better surgical success, thus the failures do not land in our offices. I usually see more exotropes because the exotropia tends to occur later — and is intermittent — so the parent looks for nonsurgical solutions.
Michael Bartiss, OD, MD: Because infantile esotropia syndrome manifests before 6 months of age, the pediatrician sees the child first, and makes the diagnosis. Infantile esotropia is primarily a surgical disease, not a vision therapy disease.
PCON: How do you handle a 6-month-old esotrope with a fixed angle who is referred from the pediatrician and qualifies for a surgical treatment protocol?
Cooper: It's clearly an initial surgical protocol. I will not treat a nonaccommodative esotropia that is 40 to 70D other than surgically. However, after surgery, you should try to establish some binocularity since you are within the critical period of time.
PCON: How would you evaluate a 2 1/2-year-old accommodative esotrope who is only intermittently esotropic, or a 4-year-old intermittent exotrope who squints one eye when in bright sunlight?
Cooper: If a child is intermittent, you have time to use a variety of nonsurgical treatment modalities. Treatment is directed by parents: those who want a quick fix tend to seek surgical consultations, while those who don't want surgery tend to seek nonsurgical means. If you have a large nonaccommodative deviation, surgery, vision training and prisms all have a place.
Kelly A. Frantz, OD: Surgeons don't see our successes; we don't need to send them. And vice versa.
Bartiss: I don't see optometry and pediatric ophthalmology as being mutually exclusive approaches to a problem. I think intermittent exotropes — as long as the angle deviation isn't really large — do better with training than surgery if they are motivated and compliant with therapy. They're the most difficult patients to achieve a stable binocular outcome if you ignore sensory fusion and sensory feedback. The key is to train these patients if at all possible. If the exotropia is a large angle, surgery may be needed "to get in the ballpark" beforebinocular training begins.
Schmidt: With an accommodative esotrope I want to help parents understand it is more than an eye turn. We also have a visual system compromise. There may be associated visual acuity loss, for example, amblyopia, suppression or other subtle anomalies. I try to help parents understand that we can intervene with surgery and prisms to resolve cosmetic side effects, but, more importantly, we should see if there is potential for re-establishing functional binocularity. We in health care centers can help our primary care colleagues by employing secondary levels of intervention and monitoring to aid in resolving the problem or predicting the likelihood of reestablishing binocularity.
PCON: Can you give us clinical pearls that work well with children?
Cooper: Before they are 2 1/2 years old, they are easy to examine. You initially see how that child moves his or her eyes, because the blind child does not make eye contact. Young children are reflex bound, so evaluating ocular motilities is easy. They will follow a transilluminator. You can evaluate pupillary responses rapidly. Infants fixate on a light, so you can perform an accurate cover test.
We use the COW barking dog. I then try to perform a slit lamp and digital pressures. As long as I've eliminated strabismus and any organic pathology, then I rule out anisometropia with a cycloplegic exam. If you are looking for amblyopia, it is easy to determine the presence or absence of central fixation. If you use an ophthalmoscope with a slit in it, the kids are so reflex bound you will see the fovea in the center of the slit, and you'll see if they're off even a half degree. Do the good eye first to establish a normal fixation pattern and then determine if they have anisometropia.
Frantz: I use lens bars for the retinoscopy. Cartoons are invaluable for keeping fixation during retinoscopy. For cover test fixation targets I use animated targets that I can change rapidly. For children 1 or 2 years old, I put lights inside puppets. For older kids, I put stickers on tongue depressors. The keys are to change the targets and keep it fun for the child.
Schmidt: I urge my colleagues to get down to the child's level — that might be on the floor — and to have an armamentarium of fixation characters that give you 3 or 4 seconds longer fixation assessment with each character. I also urge them to give little credence to symbol charts for measurement of acuity if they are presenting one symbol at a time, as this does not accurately assess acuity.
We don't have many good visual acuity charts to use in children of this age. There are some new charts coming out that we hope will be as good as the adult charts used to document amblyopia. My key approach — other than using multiple fixation characters —is putting one particular cartoon character over a transilluminator head. I use it to rapidly do a cover test or check corneal reflexes. The second tool I rely on is electrodiagnostic testing: taking a look at transient visually evoked potential to determine the monocular and binocular characteristics of vision. With young children, I need an objective way to determine the sensory anomalies present with the strabismus and to monitor the effect of my intervention program.
PCON: You're concerned about single presentation characters. Are you overestimating acuity?
Schmidt: Yes. We are overestimating acuity with most figure charts, even if visual acuity is measured with an isolated row of figures.
Frantz: The newer Lea chart (Precision Vision, Villa Park, Ill.) is better because the choices are a square, a simple house, an apple and a circle. If they blur they look similar, and at least there are several on each line so you have contour interaction. But even better are the tests with contour interaction bars around the optotype.
Bartiss: In a very young child, however, your primary concern is detecting amblyopia. Picture optotypes will give you an idea if there is an acuity difference between the eyes.
Schmidt: The quality of the response is important — the ease with which the child responds or lack of response. But if one is simply measuring visual acuity with picture charts a difference between the acuity in the two eyes can be undetectable.
PCON: What do you advocate for routine cycloplegia in a 2 1/2-year-old accommodative esotrope?
Cooper: I do a normal cycloplegic examination and eliminate strabismus with my refraction. I use 1% Cyclogyl (cyclopentolate HCl, Alcon) or, in younger kids, 0.5% Cyclogyl.
PCON: Do you ever send parents home with atropine sulfate?
Frantz: No.
Bartiss: I do, occasionally, when I need a reliable cycloplegic refraction and we're having difficulty getting complete cycloplegia in the office. In young children, because you get so much systemic absorption through the skin, you are much more likely to get anticholinergic side effects, including gastric dumping. For routine dilations in infants, I'll use Cyclomydril (cyclopentolate HCl 0.2%, phenylephrine HCl 1%, Alcon) and make sure to wipe the excess from the skin. After that, I base my decision on how darkly pigmented the iris is.
If I have a 2- or 3-year-old with blue eyes, 1% Cyclogyl works well, but allow 30 or 40 minutes for it to work. With a darkly pigmented child, I might use homatropine. I have the child look back and forth from distance to my retinoscope. If I'm still seeing a fluctuating reflex after two doses of the drops, I will send the family home with a prescription for 1% atropine solution. I'll have Mom or Dad put a drop in the child's eyes in the morning and evening the day before the return visit, and the morning of the return visit, again, wiping away all excess from the skin.
Encouraging the child to keep his or her eyes closed for 1 to 2 minutes after the drops are instilled also helps to decrease the chance of systemic absorption of the drops, because less volume goes through the nasolacrimal duct and on to the nasal mucosa.
Cooper: I've been burned with Cyclogyl, which can be a problem if you make a determination of surgery on the basis of the findings. You must rule out the accommodative component, particularly in the child with a high ratio of accommodative convergence to accommodation (AC/A). I send patients home with 0.5% atropine ointment. Then I'm sure afterwards I've eliminated accommodative esotropia.
Schmidt: If I have a 2 1/2- to 3-year-old and I do not want to rely solely on 1% cyclopentolate, I use a combination agent: cyclopentolate, tropicamide and phenylephrine. We use spray or drops.
Frantz: We've been using the spray. I don't think there's been research on accommodative esotropes with the spray, but we're getting reasonable results with nonstrabismic children.
Bartiss: With a darkly pigmented child, we'll use a drop of 0.5% proparacaine in the eye first. It "roughens" the epithelium, giving better ocular absorption. Also, I keep the drop in my pocket so it's closer to body temperature. Before I instill the drops in a child's eyes, I put a drop on their hand. This way they realize the drops aren't some horrible medicine that will hurt them. Then I have them close their eyes and tilt their heads back. I put the drop in the medial canthus and let them open their eyes.
Frantz: That's the idea with the spray. Children can close their eyes while it's applied.
Bartiss: When using an ointment or spray like that, however, you risk getting more systemic absorption. In a healthy older child the risk is low, but in an infant you have to be careful.
PCON: How would you approach an intermittent exotrope of 10 
?
Cooper: The literature demonstrates that passive means have some effect, such as part-time occlusion, minus lenses or prisms. Simple occlusion is a technique where you alternately occlude 3 hours a day, one eye each day. If the condition gets worse, stop the occlusion and the eyes will return to where they were prior to occlusion. I then see patients a month later. This can be part of the treatment at least in initial stages. It shouldn't work, but I have seen success in some patients with occlusion therapy. It should disrupt binocular vision but doesn't always. This means we don't understand the mechanisms of binocularity.
Bartiss: I use occlusion occasionally in overcorrected esotropic patients. As a primary treatment, I don't think it's sound physiologically, but there is no good data available. Minus lenses are a nonsurgical option, although I'm not a big believer in that treatment option.
Frantz: I don't find that overminusing has much effect before the child is 4 years old. I use it occasionally in the first 6 years of life before I do much therapy. If the parents can wait for more active treatment, we do what we can passively. The basic therapies are push-up techniques with toys and stickers, and a TV trainer.
Cooper: The older group, in my experience, won't get better unless you are active, with either a surgical, vision training or combined approach. The patient won't stay with me if I do nothing. With passive therapy I can keep them going, and once in a while I get a surprise. Although I do them, I don't believe they're great methods. It does give me something to calm the patient, even with minus lenses, which at least decrease the appearance of the deviation.
Bartiss: There are convergent exercises you can do with young children, from threading cereal on a shoe string to using a pick-up stick and a straw. I also think a TV trainer is a good idea.
Schmidt: I want to see if there is a suppression underlying or exacerbating the strabismic condition. If we have a child in this small angle of strabismus who is not ready for full-blown therapy, then I'd like to hold the eyes in a fusion position perhaps with minus lenses or to target the treatment of suppression.
PCON: How about a 2 1/2-year-old accommodative esotrope?
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Frantz: First thing to consider is cycloplegic refraction. If the esotropia is fully accommodative, put on the plus. Generally, they accept the full plus. I don't use multifocals at that age. I would consider a bifocal by about age 3, if the angle is larger at near point, and set it up really high so they have to use it. Managing fully accommodative esotropia is something the primary care practitioner can do. Using Fresnel prisms, I have had success with those who are not fully accommodative or those who are nonaccommodative. I use prisms more frequently for esotropia than for exotropia. I start with Fresnel, and if it's going well, then we have it ground in. But I've been known to put on 30 or 40 D, and you can't grind that in.
Cooper: I'll grind in prism right away if I have a residual angle at distance that's less than 15 D. I'd rather grind it in than use Fresnel, because of the cosmetics and the degradation of visual acuity.
Frantz: The disadvantages of Fresnel are the contrast sensitivity and acuity, but the advantage is the magnitude you can put on.
PCON: If you have maximum cycloplegia — maximum plus in a single vision prescription — and still have an esotropic deviation at near, then you put the patient into a multifocal and are still not achieving what you want, can you still train?
Cooper: You can usually correct the near. Your problem is often with the residual deviation at distance.
Frantz: Think prism at that point unless there is a lot of suppression.
Cooper: If I can't get a young child motorically straight, I think surgery.
Bartiss: You have to look at how big the angle is. Prescribing the full hyperopic refraction is appropriate. Kids with accommodative esotropia usually manifest their strabismus around age 2 and are usually about 4 to 4.5 D hyperopic, depending on their AC/A. I begin by prescribing full plus to see if they will straighten with this. If the distance deviation disappears but a residual esotropia persists at near, I'll prescribe a bifocal if it decreases the esotropia to less than 10 D and allows binocular fusion. If this fails to produce fusion, then surgical intervention becomes appropriate.
A useful technique for any accommodative esotrope is see how much plus they'll accept without cycloplegia. First, I will check for the best monocular visual acuity with the current spectacle correction. I'll take a +0.50 lens out of my trial lens rack and have the child read the line again backwards. I keep adding plus till the line blurs, and then I know how much plus I can "push" on the patient without compromising visual acuity. That's very important in the 7- to 10-year-olds because they need good distance acuity to function well in school.
PCON: To what age are you aggressive in your anti-amblyopia therapy? When do we tell the parent we've got the best vision can out of that eye?
Frantz: There isn't an upper age limit to attempting therapy if the patient is motivated. There are literature reports of older adults who had success with treatment, although it does take longer.
Cooper: If you want to cure amblyopia, which to me means the kid has equal vision between the two eyes and is 20/20, you have to make the diagnosis by age 2 and be aggressive. If the child comes in with a right esotropia and I patch, occlude and get the child to alternate, but I didn't measure visual acuity, it is remotely possible that the child wasn't amblyopic. I've never seen a child with a constant right esotropia who wasn't amblyopic. I do better with a 3-year-old than a 6-year-old, but 6 and 9 are pretty much the same. You have to watch these kids at least to age 12 because some of them come back with a recurrence of their amblyopia.
Frantz: I've seen regression at age 40 in a patient who stopped therapy then.
Bartiss: There are two things that determine your final level. One is certainly the visual cortex development. When we treat amblyopia, however, we are really trying to establish central steady fixation. This is a monocular phenomenon, and if a child is 12 years old and not a central steady fixator, that child has potential for increased vision. Most patients have potential for increased vision if they are not centrally fixating. That is where the highest concentration of cone cells are. When you establish central steady fixation in the amblyopic eye, that's when you've reached the point of diminishing returns. When do you decide this child has had enough treatment? If you've been patching, and the child goes from 20/100 to 20/40 and he or she is not centrally fixating, continue treatment.
Frantz: I think you can treat strabismus at older ages if patients have had some normal binocular vision. If they have binocular cortical cells, you can reestablish binocularity. If they have normal correspondence and they've been suppressing for years, you can break down the suppression with therapy.
Cooper: If they have been straight until a little after age 2, you probably had some form of binocular disparity detectors. If they weren't straight before age 2, your goal is peripheral fusion at best.
For Your Information:
- Jeffrey Cooper, OD is a clinical professor at the State University of New York College of Optometry. He has a practice in Manhattan and one in Brooklyn. Dr. Cooper can be contacted at 8717 21st Ave., Brooklyn, NY 11214; (212) 758-0772; fax: (212) 758-3532.
- Michael Bartiss, OD, MD, graduated from the State University of New York optometry school, then attended medical school at the University of Buffalo. He underwent fellowships in pediatric ophthalmology, ocular plastics and reconstructive surgery. He is in private practice in Pinehurst, N.C., and may be contacted at Carolina Eye Associates, 2170 Midland Road, Southern Pines, NC 28387-2927; (910) 295-2100; fax: (910) 295-5339.
- Kelly A. Frantz, OD, is an associate professor at Illinois College of Optometry. She teaches courses in binocular vision treatment and works in the pediatric/binocular vision clinic at the school. Dr. Frantz can be reached at Illinois College of Optometry, 3241 S. Michigan Ave., Chicago, IL 60616; (312) 225-1700; fax: (312) 949-7660.
- Paulette P. Schmidt, OD, is an associate professor of optometry and physiological optics at the Ohio State University College of Optometry, Columbus. Dr. Schmidt is the principal investigator for a multicenter clinical study targeted at screening preschool children and funded by the National Eye Institute. She can be reached at Ohio State College of Optometry, A324 Starling Loving Hall, 338 West 10th Avenue, Columbus, OH 43210; (614) 292-3189; fax: (614) 292-7493; e-mail: schmidt@osu.edu.