Pediatrics and Strabismus

Introduction

The goal in the treatment of infantile esotropia is early ocular alignment to provide some form of binocularity which will provide motor fusion. This motor fusion will, in turn, help to provide long-term ocular alignment and decrease the number of surgeries that a patient may be required to undergo during his/her lifetime. Most people feel that the monofixation syndrome as described by Marshall Parks is the best possible result that can be obtained in these patients. In his definition of monofixation syndrome, Parks included alignment to within 8 pd of orthophoria. It has been felt that a patient who falls anywhere in this range of orthophoria will receive an equal binocular benefit. In this paper, the authors examined this hypothesis.

Materials and Methods

A 15 year prospective study with a 5 year outcome determination was performed. Patients undergoing surgery for congenital esotropia were included. Patients who were felt to be at high risk for poor follow-up were excluded. Patients were subdivided into three groups based upon their ocular alignment: orthophoria, esotropia less than 8 pd, exotropia less than 8 pd. All patients were evaluated for binocular function with stereopsis testing and demonstration of fusion with the Worth Four-Dot test. Final ocular alignment was recorded for each patient. Whether or not a patient drifted more than 8 pd from their initial alignment point was also recorded. This was done so that patients with an initial exotropia who drifted outside the target range could be compared equally with patients who were initially esotropic who drifted the same amount but had not gone past a mark of 8 pd of exotropia.

Results

There were 118 patients in the study. Initially, 24 were orthotropic, 84 had up to 8 pd of esotropia and 10 had up to 8 pd of exotropia. Patients who were orthotropic were most likely not to drift over the five year period of the study. Patients who ere esotropic were less likely not drift compared to those that were exotropic. Sensory testing revealed better binocular function for patients who were orthotropic than esotropic. Esotropic patients had better results than exotropic patients.

Conclusions

The results of the study would indicate that all patients aligned to within 8 pd of orthophoria are not equal. Those who are aligned to orthtropia are most stable, followed by esotropic patients and then exotropic patients. However, it is possible that small "self adjustments" after surgery may play a role in this alignment. It may be that patients with the best binocular function "alter" their own alignment during the recovery period to give themselves the best alignment, orthrotropia or even esotropia. Those with poor binocular potential may stay exotropic if that is where they were initially placed. Therefore, the results would not support active intervention to achieve perfect alignment, such as reoperation for a small angle exotropia in the immediate postoperative period. This data is very useful in helping to predict long-term outcomes in this patient population.

Scott Olitsky, M.D.
Children's Hospital,
Buffalo, New York

Pediatrics and Strabismus

The ocular motility abnormality found in most patients with blowout fractures of the orbital floor is a restrictive hypotropia on the affected side with evidence of entrapment of orbital tissues around the inferior rectus muscle.However, in some cases,hypertropia can be identified on the affected side and appear to have limitation of downgaze. The objective of this paper is to understand the pathophysiology and management of patients with orbital blowout fracture with hypertropia and vertical diplopia on the affected side. Ten patients with the above criteria were followed through at least 13 days of conservative care.Computed tomography demonstrated a characteristic depressed fracture of the posterior orbital floor extending to the posterior wall of the maxillary sinus in all patients.In many patients,the inferior rectus looped inferiorly and then rose to contact the globe at a steep angle.Diplopia did not resolve spontaneously in any patient. eight patients had resolution of diplopia and hypertropia within two months of surgery where orbital contents were elevated to the posterior extent of the fracture,and the floor defects were bridged. Two patients had residual diplopia in extreme downgaze only. The authors speculate on a hypothesis based on Ct scan findings."Ct scans suggest two possibly related mechanisms for the hypertopia seen in these patients.First the angle of contact of the inferior rectus with the globe is increased greatly.When the inferior rectus approach the globe at a steep angle,its mechanical effect on the eye can be altered.The origin of the inferior rectus shifts to the point at which the muscle contacts and adheres to the floor of the orbit.The new origin of the muscle,combined with its new angle of contact with the globe,diminishes the power of the muscle".This hypothesis is based on experiences on the medial rectus after medial wall fractures.

A second mechanism for the hypertopia is suggested by the fracure deformity itself.The inferior rectus was noted to cross over a sharp fracture step off in many patients,and its motion could be limited at that point.This would create a relative posterior fixation or Faden effect and diminished the efficiency of the rectus muscle. The authors concluded that the diagnosis of a posterior blowout fracture should be supported by characteristic findings on CT scan.If the motility abnormality persist for two weeks,posterior orbital exploration and repair should be undertaken. It is a well written and useful article for strabismus specialists and oculoplastic surgeons.

Miguel Paciuc, MD
Mexico City, Mexico

Pediatrics and Strabismus

The authors retrospectively analyzed the visual acuity of 600 patients fifteen years of age or younger with intermittent exotropia to determine the incidence of amblyopia. The information recorded for analysis was taken prior to occlusion therapy and before surgical intervention. The parameters examined included: refractive error, best corrected visual acuity, type of intermittent exotropia, control of the exodeviation at distance fixation, constant or intermittent and stereoacuity at near.

From the group 412(68.7%) patients had equal vision between the two eyes, 111(18.5%) patients had unequal vision of one line difference between the eyes and 77(12.8%) patients had functional amblyopia.

Significant refractive error in the amblyopic group included 16 cases with anisometropia, four with myopia and five with astigmatism or mixed astigmatism. The prevalence of amblyopia was similar among the different types of intermittent exotropias. Patients with a constant manifest exotropia at distance were more likely to exhibit amblyopia (21%) than those with an intermittent exotropia (9.3%). The frecuency of reduced stereoacuity was not significant between the amblyopia group (67%) and non-amblyopic group (60%). This is an important well written article. Intermittent exotropia is a common type of deviation and there are few recent reports available on the prevalence of amblyopia on this condition. The study is well designed.

The results were not biased in terms of the type of exotropia found as the patients were nearly equally distributed between divergence excess (51%) and basic type (45%) with amblyopia being 12.4% and 13.3% respectively. The authors concluded that primary intermittent exotropia is susceptible to functional amblyopia despite intermittency of the deviation or the type of exotropia. They concluded that visual acuity testing must be evaluated more closely than previously suggested.

Miguel Paciuc, MD
Mexico City, Mexico

Pediatrics and Strabismus

Introduction:

Methods:

Sixty two (62) developmentally normal children who underwent strabismus surgery were compared to 29 developmentally delayed children. Over and Undercorrections were define as a deviation >10 pd from orthophoria. Because the authors noted a large incidence of overcorrections in the delayed group, these patients began receiving less surgery for the same deviations.

Results:

Prior to the adjustment in the amount of surgery performed on the delayed group, there was an incidence of overcorrection, at one year, of 18% and undercorrections of 6%. This compared to an over and undercorrection of 6% and 12% in the normal group respectively. After the modification, the overcorrection rate was 0% and the undercorrection rate was 14% in the delayed group. The rates for the normal group was essentially unchanged. Based on these results, the authors suggested performing less surgery for a given angle of esotropia in developmentally delayed children.

Comment:

The authors make their recommendations based on the large overcorrection rate at the one year postoperative evaluation interval. However, within the first three-four months following surgery there does not appear to be a significant difference in the overcorrection rate between the two groups of delayed children. Is this late overcorrection rate a factor of the surgery or the poor binocular potential of these patients? Many patients who lack good binocular vision often become exotropic with time. Once a patient has recovered from surgery, and their eyes are aligned, it would seem that it is the binocularity of these patients that helps to maintain alignment, not the amount of surgery that it took to make the eyes straight. If poor binocularity is the cause of these overcorrections, it may not be right to blame the larger amounts of surgery for causing these patients to become exotropic sooner. It may be that they started their drift to exotropia from a closer position, i.e. closer to orthotropia. Indeed, the group that received less surgery did have more undercorrections at the one year interval. Perhaps, given more time, these patients will also become exotropic as well. It will be interesting to see how these patients behave over a longer time period. The high rate of exotropic drift in these patients is important to note. Based on the authors findings, small deviations and undercorrections should probably be treated less aggressively in these patients as it may make them exotropic at a sooner point in time. However, longer term follow-up is needed before making a final determination regarding a modification in surgery for these children.

Scott Olitsky, M.D.
Buffalo, New York

Pediatrics and Strabismus

Summary:

The authors report on the results of cataract extraction (CE) and intraocular lens (IOL) implantation in 45 consecutive eyes of 37 patients between May 1991 and December 1993. Twenty (45%) eyes had traumatic cataracts and 25 (55%) had congenital or developmental cataracts. The patients ranged in age from 1 to 18 years at the time of surgery. When macular injuries were excluded, 87% of the patients with traumatic cataracts obtained 20/40 vision or better. All nine eyes with bilateral cataracts achieved at least 20/40 vision. Of the ten eyes with unilateral cataracts, only one eye had a visual acuity of 20/40 and two were 20/200. Five eyes, all having traumatic cataracts, developed postoperative complications, including iris capture (three eyes) and intraocular hemorrhage and secondary membrane formation (one eye each). Twenty seven eyes (60%) required Nd:YAG laser posterior capsulotomy and 11 (41%) of these required a second laser procedure.

Discussion:

The use of intraocular lens implantation as the first choice for visual rehabilitation of the aphakic child continues to grow in popularity. The use of an IOL has the obvious advantage of decreasing the morbidity related to long-term contact lens wear. However, as the authors note, it does not eliminate the need for careful observation and treatment for amblyopia in the visually premature child. While the results of this study are promising, most of the patients involved in this series were relatively older children and therefore, at less risk to develop amblyopia. Less than one-third of the traumatic group was under the age of six and only one was under four. In the unilateral congenital/developmental group, only four patients were under four years of age. In the bilateral congenital/developmental group four patients were less than four years of age. In the nine patients under the age of four in this study, only one developed 20/40 vision and one developed good fixation in the operated eye. The study shows good short term results in older children and the authors caution against extrapolating these results long term. Longer follow-up data is still required to ascertain the safety of IOLs in children. Furthermore, while studies like these show that IOL implantation in children is feasible, they have not been proven to increase the visual prognosis over conventional contact lens therapy.

Scott Olitsky, M.D.
Buffalo, New York

Pediatrics and Strabismus

Examination of the pediatric patient routinely includes a cycloplegic refraction. The authors agree one drop of cyclopentolate 1% (Cyclogyl 1%) is generally insufficient. They seek to determine the influence of the time interval between drops on cycloplegia and mydriasis. The currently accepted protocol is to wait 5 to 10 minutes between drops. 48 pediatric patients (2-12 years of age) were examined twice, one week apart. Two drops of cyclogyl were instilled, one minute apart on one visit and five minutes apart on the other. They noted no statistical difference in streak retinoscopy results or mydriasis, irrespective of race, iris color, gender or age. They conclude cyclopentolate 1% given one minute apart is as effective as when given five minutes apart.

Raymond G. Magauran III, MD
Buffalo, NY

Pediatrics and Strabismus

Previous reports demonstrate a risk for transient lenticular opacities and subsequent cataract formation using argon laser for pan retinal photocoagulation (PRP) in Retinopathy of Prematurity (ROP). The authors investigated the diode laser for such effects. Fourteen threshhold ROP eyes from seven patients, with significant tunica vasculosa lentis (thought to increase risk for lens opacities) were enrolled. Treatment consisted of 1060-2132 shots, 200-400 mW duration, 200 msecs delivered via a indirect ophthalmoscope. ROP regressed in all after a single treatment. No corneal, iris, posterior synechiae or lenticular changes were noted. One eye developed a micro hyphemia which resolved without sequelae in four days. They conclude that the diode laser at the energy levels used in this study can safely be used to treat ROP in the presence of tunica vasuloa lentis. They caution however that due to the limited size of the study and short follow-up time, the study is limited.

Raymond G. Magauran III, MD
Buffalo, NY