Journal of Pediatric Ophthalmology and Strabismus

Rate of Deterioration in Accommodative Esotropia Correlated to the AC/A Relationship

Irene H Ludwig, MD; Marshall M Parks, MD; Pamela R Getson, PhD; Lisa A Kammerman, PhD

Abstract

ABSTRACT

We analyzed the claim that accommodative esotropia tends to deteriorate with greater frequency if the accommodation convergence relationship (AC/A) is high. Records of 119 patients whose eyes were aligned with spectacles alone were studied. Their AC/A relationships were graded according to the difference between the distance and near measurements: normal included 0 to 9 prism diopters (Δ) difference; grade 1 ranged from 10 to 19Δ difference; grade 2 from 20 to 29Δ difference; and in grade 3 the difference was 30Δ or greater. Deterioration is characterized by a nonaccommodative component of esotropia greater than 10? at distance becoming superimposed on the initial accommodative esotropia. Deterioration occurred in 7.7% of patients with a normal AC/A, 25% with grade 1 high AC/A, 44% with grade 2 high AC/A, and 52% with grade 3 high AC/A. Hypotheses were investigated using chi square, ttest, analysis of variance (ANOVA), and log linear analyses. Distributional differences were highly significant by chi square test (p = 0.001) with a rejection of the null hypothesis of no difference between the groups at the α = 0.05 level. An alternate analysis of average AC/A ratio in the deteriorated versus nondeteriorated patients was equally statistically significant by the t-test. Hypermetropia was significantly higher in the normal AC/A group. Multi-factor comparisons showed that time-to-deterioration, treatment delay, age of onset, and amblyopia were factors that did not relate significantly to the incidence of deterioration.

Abstract

ABSTRACT

We analyzed the claim that accommodative esotropia tends to deteriorate with greater frequency if the accommodation convergence relationship (AC/A) is high. Records of 119 patients whose eyes were aligned with spectacles alone were studied. Their AC/A relationships were graded according to the difference between the distance and near measurements: normal included 0 to 9 prism diopters (Δ) difference; grade 1 ranged from 10 to 19Δ difference; grade 2 from 20 to 29Δ difference; and in grade 3 the difference was 30Δ or greater. Deterioration is characterized by a nonaccommodative component of esotropia greater than 10? at distance becoming superimposed on the initial accommodative esotropia. Deterioration occurred in 7.7% of patients with a normal AC/A, 25% with grade 1 high AC/A, 44% with grade 2 high AC/A, and 52% with grade 3 high AC/A. Hypotheses were investigated using chi square, ttest, analysis of variance (ANOVA), and log linear analyses. Distributional differences were highly significant by chi square test (p = 0.001) with a rejection of the null hypothesis of no difference between the groups at the α = 0.05 level. An alternate analysis of average AC/A ratio in the deteriorated versus nondeteriorated patients was equally statistically significant by the t-test. Hypermetropia was significantly higher in the normal AC/A group. Multi-factor comparisons showed that time-to-deterioration, treatment delay, age of onset, and amblyopia were factors that did not relate significantly to the incidence of deterioration.

INTRODUCTION

The success associated with treating accommodative esotropia with hypermetropic spectacles has been known since the time of Donders.1 Bifocal therapy to correct the residual esodeviation at near in patients with high accommodative convergence relationships also is well-established.2·5 Despite achieving initial ocular alignment by spectacles alone, we noted that some patients develop a nonaccommodative component superimposed on their accommodative esotropia. Moreover, this trend seemed directly proportional to the severity of the high accommodation convergence relationship (AC/A).6 This study was undertaken either to corroborate or refute the findings of a previous study.6

MATERIALS AND METHODS

Records were analyzed from the private practice of one of us (MMP) of the accommodative esotropie patients achieving ocular alignment at distance and near fixation with spectacle correction alone. The records of all patients in the practice since its inception were available, but due to the volume, not all could be reviewed. Three letters were selected by a computer's random number generator, and only records of patients with last names beginning with these letters were searched.

Criteria for inclusion in the study determined prior to the record search were:

* Onset of the esotropia prior to 8 years of age;

* Initial successful alignment with spectacles alone (with or without bifocals) to within 8Δ for both distance and near viewing;

* No greater than 1.5 D anisometropia (spherical and/or cylindrical difference);

* Follow-up of 5 years.

Excluded from the study were:

* Amblyopia of 20/100, or greater;

* Siblings;

* Mental retardation;

* Dissociated vertical deviation (DVD);

* Previous extraocular muscle surgery;

* Absence of follow-up within 2 years after receiving the initial spectacles.

Ocular alignment was measured with prism and alternate cover at 6 and 0.33 m. The refractive state was determined by retinoscopy 40 minutes after instilling cyclopentolate 2% (combined with tropicamide 1% in darkly pigmented individuals) into the eyes.

The severity of the high AC/A relationship was graded according to the difference between the distance and near prism and alternate cover measurements obtained under controlled accommodation circumstances. A difference of less than 10Δ was considered normal. The grades of high AC/A relationships had near measurements exceeding the distance measurements as follows: grade 1 was 10 to 19Δ; grade 2 was 20 to 29Δ; grade 3 was 30Δ or greater. The maximal difference between the distance and near measurements obtained over 8 years follow-up determined the AC/A grade. However, the average AC/A for each patient was calculated by averaging the difference between the distance and near measurements for all examinations within the first 8 years of follow-up (only preoperative measurements were used in surgical patients).

Group Characteristics: The records of 119 patients were included in the study. The average age of onset of esotropia was 2 years, 9 months (range 2 months to 6 years, 10 months). Length of follow-up averaged 9.35 years (range 5 to 31 years).

Table

TABLE 1Bifocal Use by AC/A Grade (Near-Distance Prism Cover Test)

TABLE 1

Bifocal Use by AC/A Grade (Near-Distance Prism Cover Test)

Table

TABLE 2Deterioration by AC/A Grade

TABLE 2

Deterioration by AC/A Grade

Bifocals were prescribed for 67 patients (56.3%) (Table 1). The one patient with a grade 2 high AC/A initially, who was not given bifocals, maintained near alignment over 9 years without them, although the AC/A relationship improved to grade 1 after the first year of spectacle wear. One patient with a normal AC/A wore bifocals for 2.5 years.

RESULTS

Thirty-six patients deteriorated (30.3%), while 83 maintained spectacle alignment. Table 2 lists the deteriorated and undeteriorated patients according to their graded AC/A relationship. The increased incidence of deterioration in the high AC/A grades was statistically significant. The mean interval to deterioration after initial spectacle alignment was 2.16 years (range 1 month to 7 years). The average AC/A of the deteriorated patients was significantly higher than that of the undeteriorated group (Table 3).

The association between AC/A grade and hypermetropia showed that mean hypermetropia (spherical equivalence, averaged between both eyes) was significantly greater in children with a normal AC/A relationship than the mean hypermetropia for each grade of high AC/A relationship (Table 4). Hypermetropia compared for deteriorated versus undeteriorated status (Table 5) revealed a significantly higher mean hypermetropia in the undeteriorated group.

A one-way analysis of variance of the time-to-deterioration (following initial spectacle alignment) across AC/A grades showed no significant group differences (Table 6). The variability of time-to-deterioration was large within all the AC/A grades.

Table

TABLE 3Average AC/A by Deterioration Status

TABLE 3

Average AC/A by Deterioration Status

Table

TABLE 4Mean Hypermetropia by AC/A Grade (ANOVA, F-test with post hoc comparisons)

TABLE 4

Mean Hypermetropia by AC/A Grade (ANOVA, F-test with post hoc comparisons)

Table

TABLE 5Mean Hypermetropia by Deteriorated or Undeteriorated Outcome

TABLE 5

Mean Hypermetropia by Deteriorated or Undeteriorated Outcome

Table

TABLE 6Time to Deterioration by AC/A Grade

TABLE 6

Time to Deterioration by AC/A Grade

Table

TABLE 7Delay-to-Treatment by Outcome

TABLE 7

Delay-to-Treatment by Outcome

The delay between the onset of esotropia and spectacle correction of the misalignment was investigated for the deteriorated and undeteriorated patients. Delay-to-treatment was investigated by a two-way analysis of variance (ANOVA) of AC/A grade by deteriorated or undeteriorated status. The interaction of grade and status was nonsignificant [F = 0.77, df = (3,108), p = 0.516), as was the delay-to-treatment across AC/A grades while controlling for deteriorated versus undeteriorated status [F = 0.33, df = (3,108 ), p = 0.80321. Thus, delay-to-treatment was not significantly different among the different AC/A groups. The finding of a significantly longer delay-to-treatment in the undeteriorated patients than in those who eventually deteriorated while controlling for AC/A grades was unexpected and unexplainable (Table 7).

Initial comparison of age at onset in deteriorated and undeteriorated patients showed a signficantly older age of onset in the undeteriorated group than in the deteriorated group (Table 8 ). However, results of two-way ANOVA by AC/A grade and status revealed no effect due to these variables individually, but their interaction was significant (p = 0.042). In fact, the age of onset was higher in the deteriorated patients of AC/A grades 1 and 2 than in the undeteriorated patients.

Amblyopia status was recorded for all study patients, and was determined to be present in 24.4% (patients with amblyopia of 20/100 or greater at any time already had been excluded from the study). Amblyopia was evaluated for an association with AC/A grade and deteriorated or undeteriorated outcome status (Table 9) by loglinear models. In the amblyopia group 34.5% deteriorated, while a slightly smaller percentage, 28.9% , of nonamblyopic patients deteriorated; however, the loglinear analysis indicated that amblyopia and outcome were independent. A smaller percentage of grade 1 AC/A patients were amblyopic (8.7% ) than normal (33.3% ), grade 2 (26.9% ). and grade 3 (22.6% ) AC/A patients. No clinical significance could be derived from this pattern.

Inferior oblique overaction was rare at initial examination of both deteriorated and undeteriorated patients (Table 10). Although most deteriorated patients maintained normal inferior oblique action, several developed inferior oblique overaction, usually at the same time the deterioration developed (Table 11).

Table

TABLE 8Age at Onset (Months) by Outcome and AC/A Grade

TABLE 8

Age at Onset (Months) by Outcome and AC/A Grade

Table

TABLE 9Amblyopia by Outcome and AC/A Grade

TABLE 9

Amblyopia by Outcome and AC/A Grade

Table

TABLE 10Deterioration by Inferior Oblique Overaction at Initial Examination

TABLE 10

Deterioration by Inferior Oblique Overaction at Initial Examination

Table

TABLE 11Deterioration by Maximal Inferior Oblique Overaction Measurement

TABLE 11

Deterioration by Maximal Inferior Oblique Overaction Measurement

DISCUSSION

The rate of deterioration after initial successful alignment with spectacles was greater in patients with a high AC/A relationship and less in patients with high hypermetropia; the highest hypermetropia was in the normal AC/A group. Factors not significantly related to the rate of deterioration included time-to-deterioration, delay in treatment, age of onset, and amblyopia.

There have been other reports of deterioration in esotropie patients initially aligned by spectacles. Raab found a 13% incidence of deterioration in patients with normal AC/ A relationships, and 21% deterioration in those with a high AC/A.4 These figures were not statistically significant, possibly due to insufficient sample size. Baker and Parks found a 50% deterioration incidence in both normal (n = 11) and high AC/A relationship (n = 10) patients whose accommodative esotropia began before 1 year of age.7 Von Noorden, Morris, and Edelman found a higher incidence of deterioration in patients with lower AC/A ratios,3 but their study used the grathent AC/A ratio8-10 rather than the linear AC/A relationship.11 However, a low AC/A ratio by the grathent method may result from poor response to the +3.00 lens used in the test, and therefore not reflect the true amount of deviation at near.

The significantly higher rate of deterioration in patients with a high AC/A relationship in our study correlates with the previous, unpublished data gathered in a similar manner, but with a slightly different AC/A grading system.6 However, if the data of this study were evaluated with the old grading system (normal AC/A was 0 to 10Δ; grade 1 high AC/A was 11 to 20Δ; grade 2 was 21 to 30Δ; and grade 3 was >30?), the rate of deterioration in patients with a high AC/A relationship would be even higher. The explanation for increasing incidence of deterioration with increasing AC/A grade is not provided by the data, but it is postulated that patients with a high AC/A relationship experience near esotropia repeatedly throughout each day, despite having bifocal spectacles. This may, over time, lead to permanent changes in the extraocular muscles, causing deterioration.

The higher degree of hypermetropia in the normal AC/A group in this study is consistent with a number of other reports.2,4,7 Raab found that increasing hypermetropia over time was not a significant contributor to deterioration,4,12 a factor not evaluated statistically in our study. Our data revealed no correlation between age of maximal hypermetropia and age of deterioration.

The average time to deterioration in this series, 2.16 years, was similar to that observed in other studies.4,7 The unexpected finding of a longer average delay-to-treatment in undeteriorated patients is unexplainable, but does suggest that treatment delay does not contribute to deterioration once alignment is achievable by spectacles.

Although amblyopia may be expected to contribute to deterioration, our data show no statistically significant association between amblyopia and deterioration. However, only mildly amblyopic patients (20/80 or better) were included in the study.

Inferior oblique overaction previously has been associated with deterioration.4,12 Although inferior oblique overaction developed in a significant number of our deteriorated patients, it did not precede deterioration, and therefore was not a useful prognostic indicator.

CONCLUSION

Our data show a strong trend toward deterioration in patients with high AC/A relationships. We recommend that the clinician see such patients with greater frequency, and also use the deterioration figures to inform the parents of the prognosis for lasting success of spectacle correction.

REFERENCES

1. Donders FC: On The Anomalies of Accommodation and Refraction of the Eye. London, The New Sydenham Society, 1864.

2. Parks MM: Abnormal accommodative convergence in squint. Arch Ophthalmol 1958; 59:364-380.

3. Von Noorden GK, Morris J, Edelman P: Efficacy of bifocals in the treatment of accommodative esotropia. Am J Ophthalmol 1978; 85:830-834.

4. Raab EL: Etiologic factors in accommodative esodeviation. Trans Am Ophthalmol Soc 1982; 80:657-694.

5. Burian HM: Accommodative esotropia. Classification and treatment. Int Ophthalmol Clin 1971; 11(4).23-26.

6. Manley DR, Parks MM: Unpublished data, in Duane TD, Jaeger EA (eds): Clinical Ophthalmology. Philadelphia, Harper & Row, 1986, vol 1, chap 12. p 5.

7. Baker JD, Parks MM: Early-onset accommodative esotropia. Am J Ophthalmol 1980; 90:11-18.

8. Von Noorden GK: Binocular Vision and Ocular Motility, ed 3. St. Louis, CV Mosby, 1985, pp 85-99, 280-283.

9. Ogle KN, Martens TG: On the accommodative convergence and the proximal convergence. Arch Ophthalmol 1957; 57:702-715.

10. Sloan LL, Sears ML, Jablonski MD: Convergence-accommodation relationships. Arch Ophthalmol 1960; 63:283-306.

11. Bateman JB. Parks MM: Clinical and computer-assisted analyses of preoperative and postoperative accommodative convergence and accommodation relationships. Ophthalmology 1981; 88:1024-1030.

12. Raab EL: Hypermetropia in accommodative esodeviation. J Pediatr Ophthalmol Strabismus 1984; 21:194-198.

TABLE 1

Bifocal Use by AC/A Grade (Near-Distance Prism Cover Test)

TABLE 2

Deterioration by AC/A Grade

TABLE 3

Average AC/A by Deterioration Status

TABLE 4

Mean Hypermetropia by AC/A Grade (ANOVA, F-test with post hoc comparisons)

TABLE 5

Mean Hypermetropia by Deteriorated or Undeteriorated Outcome

TABLE 6

Time to Deterioration by AC/A Grade

TABLE 7

Delay-to-Treatment by Outcome

TABLE 8

Age at Onset (Months) by Outcome and AC/A Grade

TABLE 9

Amblyopia by Outcome and AC/A Grade

TABLE 10

Deterioration by Inferior Oblique Overaction at Initial Examination

TABLE 11

Deterioration by Maximal Inferior Oblique Overaction Measurement

10.3928/0191-3913-19880101-04

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