Binocular Visual Field Changes after Surgery in Esotropic Amblyopia

Abstract

purpose. To determine binocular visual field (BVF) changes after strabismus surgery in children with large angle esotropia, and whether these changes can be predicted, using a prism to correct the preoperative angle of deviation.

methods. Monocular visual field (MVF) and BVF were measured by Goldmann perimetry in healthy adults (n = 6) using a range of prisms. Visual fields were then measured in normal children (n = 19) and in children with large angle esotropic amblyopia (n = 28). The visual field was measured preoperatively with and without a prism equal to the angle of esotropia. A further evaluation was made at 2 and 18 months postoperatively.

results. In healthy adults, prisms had no significant effect on the extent of MVF or BVF. There was no significant difference in the MVF in children with and without strabismus. There was a significant reduction in the BVF and in the ratio of the BVF to MVF between normal children (138°, 0.59; P = 0.01) and children with esotropic amblyopia (120°, 0.57; P = 0.02). Postoperatively, there was a significant improvement in the BVF (P = 0.02), which was maintained at 18 months. The increase in BVF was significantly greater than the variation in repeat fields (P = 0.04), with 8 of 13 children showing an increase in the BVF above the 95% CI of the repeatability measurements. There was a good linear correlation between the size of the preoperative BVF in the presence of a prism and the postoperative BVF (r = 0.90 P = 0.001).

conclusions. Children with esotropic amblyopia demonstrate a significant reduction in their BVF. Prisms correcting the preoperative angle could be used to predict the potential increase in the BVF after surgery. Patients with a BVF/MVF approaching that found in normal children, however, may not show an improvement in the size of their BVF after surgery.

Although contraction of the peripheral binocular visual field (BVF) in patients with esotropia is well established, ^{1 2 3 4} the relationship between the extent of the BVF and angle of esotropia is less clear. ⁴ In subjects with small angle esotropia, suppression tends to be confined to a central region of the deviated eye in a region corresponding to the fovea of the fixating eye, while in patients with large angle esotropia, marked restriction of nasal and temporal hemifields has been reported. ^{1 2 5 6} This may vary, however, according to the degree of alternation, suppression, and retinal correspondence. ⁷ In animal studies, visual field (VF) losses have no direct relationship to the angle of strabismus, although the extent of the visual field is differentially impaired in mild and severe esotropia. ⁸  

It has been speculated that gains in development after surgery for infantile esotropia relate in part to an expansion of the BVF. ^{3 9} Adults undergoing surgery for large angle esotropia have a fairly uniform increase in the postoperative BVF. Wortham and Greenwald reported an expansion in the horizontal extent of the BVF by an amount approximately commensurate with the change in the angle of strabismus in ten adult esotropes after surgical alignment. ⁴ Similarly, Kushner noted an expansion of the BVF in all but one of 37 adult patients after surgery for esotropia, together with an improvement in binocular functions. ³  

It is not clear, however, whether a uniform expansion of the BVF occurs in children after surgery for esotropia and whether it is possible to predict preoperatively the change in the postoperative BVF. The purpose of this study was to characterize the VF in children with strabismic (esotropic) amblyopia and the extent to which changes in the BVF after strabismus surgery could be predicted preoperatively using a prism to correct the preoperative angle of deviation. 

Materials and Methods

Adult Subjects

Adults included in the study had no ocular abnormality, visual acuities correctable to 6/6 or better in either eye, < 0.75 diopters of anisometropia and < 1 diopter of astigmatism, and demonstrated at least 40“ of stereoacuity and the ability to maintain fusion at 34 cm in the presence of a prism from 30 prism diopters (PD) base-out to 10 PD base-in. Monocular visual fields (MVF) and BVF were recorded in the presence of the following prisms: −10, 0, +2, +10, +20, and +30 PD. 

Normal Children

To characterize the normal MVF and BVF for comparison to the VF in children with large angle esotropia, children with normal visual functions with no history of ocular disease, best corrected visual acuity (BCVA) of at least 6/6 in each eye, 40″ of stereoacuity, and the absence of a tropia or monofixation syndrome, were included. The presence of a microptropia and monofixation syndrome was assessed using a 4 PD base-out prism and a Worth 4 Dot test using rivalry or a yellow appearance of the white light as a bifoveal response. Children were excluded if they had correctable visual acuities of < 6/6 in either eye, if there was anisometropia greater than 0.75 D, or if they were unable to perform the VF test reliably (inability to maintain central fixation or inconsistent responses as judged by the operator). A subgroup of these children underwent repeated VF testing. 

Children with Large Angle Strabismic (Esotropic) Amblyopia

Children with large angle esotropia (greater than 10 PD), visual acuity of better than 6/18 in the amblyopic eye and 6/6 in the fellow eye, who had undergone full time occlusion (FTO), and whose visual acuity had stabilized, were included in the study. The size of the angle of deviation was measured using both a simultaneous prism cover test (used for the analysis) and an alternate prism and cover test. Children were excluded if they demonstrated any ocular abnormality (apart from esotropia and strabismic amblyopia), the presence of a vertical tropia, previous strabismus surgery, nystagmus, abnormal head postures, the presence of anomalous retinal correspondence using Bagolini striate glasses, an inability to maintain steady fixation with the amblyopic eye when the fellow eye was occluded, or an inability to perform a VF test (as with the above inclusion criteria for normal children). Those patients who underwent strabismus surgery, were followed for up to 2 years after surgery, with recording of the ocular status and VF at 1–3 months, 6 months, and 1–2 years postoperatively. FTO was recommenced postoperatively, if the visual acuity started to reduce. To compare variances in the normal and abnormal VF, a subgroup of children who did not undergo surgery during a similar time interval to those undergoing surgery, were recalled for repeat VF measurements. 

Recording of Visual Fields

A total of five VFs were recorded in every patient on either one or two sessions. The MVF of each eye was recorded, followed by the BVF. The MVF of the deviating eye was then recorded using a prism equal to the angle of deviation, followed by recording of the BVF with the same prism. If, after surgery, there was greater than 10 PD of residual deviation, the VF was also measured in the presence of a prism equal to this residual angle. 

VFs were recorded using a Goldman kinetic perimeter. The luminance of the bowl was set according to the manufacturer’s instructions (Haagstreit, Bern, Switzerland) at 31.5 asb (10 cd/m²). Testing was performed using III-4-e sized target while the patient fixated the central fixation hole of the hemisphere. For testing with both eyes open, children with strabismic amblyopia were required to fixate the central target with their non-amblyopic eye. Measurements were excluded and repeated if there was alternation of fixation. The stimulus was moved from without the field of view along each of 12 meridians at approximately 3° per second. Each point on the field was repeated and the mean of the two values used to construct the field. The subjects were asked to press the buzzer as soon as they detected the stimulus. In all cases, testing was performed using the optimal spectacle correction. For measurement of the VF with a prism, Fresnel prisms (72 × 72 mm) were attached to Perspex goggles which were worn by the subjects. Subjects wearing glasses were instructed to wear the Perspex goggles with the attached Fresnel prism over their spectacles. The prism was placed in front of the amblyopic eye, unless the deviation was greater than 35 PD, in which case the prism was split between both eyes. Repeat and follow-up VFs were recorded by the same examiner for the same patient. Children had to be able to demonstrate an ability to participate adequately in recording their visual field; that is, they needed to be able to satisfy the examiner that they could maintain fixation of the central target of the Goldmann perimeter during testing when the peripheral stimulus was being moved, that they could promptly respond to visualization of the target stimulus, and that they would respond to the seen stimulus at two locations in the VF within 5° on repeated testing. VFs were analyzed according to the horizontal and vertical extent of the MVF and BVF (degrees), the area of the MVF and BVF (measured by dividing the plotted VF into cm² using a transparent overlay) and the ratio of the BVF to the sum of the MVFs. Statistical analysis was performed using Student’s t-test and analysis of variance (Minitab statistical software release 13.20; Minitab Ltd., Coventry, UK). Analysis of the refractive data was according to the method of Kaye and Harris ^{10 11} . Local ethical approval was obtained and the declaration of Helsinki was adhered to. 

Results

Sixty subjects were initially included in this study. Seven subjects (children) were excluded because of inconsistency and poor concentration during testing of their visual fields. The remaining 53 subjects comprised 6 healthy adults (mean age, 34.4 years; range, 28–43 years), 19 normal children (mean age, 9.4 years; range, 5–14 years), and 28 children with large angle esotropia and amblyopia (mean age, 9 years; range, 6–15 years). A subgroup of 13 of these children underwent surgery to reduce their esotropia. 

The VF parameters for the adult data using a range of prisms are shown in Table 1 . The presence of a prism orientated base-out or base-in within the range used had no significant effect on the horizontal and vertical extent or area of either the MVF or BVF, or on the ratio of the BVF to MVF (P = 0.99). 

The parameters of the MVF and BVF for children with and without strabismus are shown in Table 2 . The VF parameters for normal children (Table 2) were significantly less than the corresponding normal adult values, for all parameters (P < 0.01) except the vertical extent of the BVF (P = 0.08) and MVF (P = 0.06) and the ratios of the BVF to MVF for horizontal extent (P = 0.63) and area (P = 0.41). 

Monocular Visual Fields

There were no significant differences between right and left vertical MVF measurements or VF areas (Table 2) between normal children and those with strabismic amblyopia (P > 0.17). Both the right and left horizontal MVF were, however, marginally but significantly smaller in children with strabismic amblyopia (105.79 ± 19.55, 106.79 ± 19.25; P = 0.05) than in normal children (116.18 ± 12.52, 117.41 ± 13.10; P = 0.05). There was no significant difference in the MVF parameters between amblyopic and fellow eyes in terms of vertical and horizontal extent or area, respectively (P = 0.21, 0.51 and 0.63; Table 2 ). 

Binocular Visual Fields

There was no significant difference in the vertical extent of BVF in children with strabismic amblyopia (107.14 ± 19.94) compared to normal children (115.39 ± 9.52; P = 0.10). Both the horizontal extent and area of the BVF were, however, significantly smaller in children with esotropic amblyopia (119.76 ± 26.31, 158.52 ± 54.67 cm²; P = 0.01) than in normal children (138.42 ± 14.60, 192.42 ± 34.07 cm²; P = 0.02). In addition, there were significant reductions (Table 2) in the BVF to MVF ratios (horizontal extent and area) in children with strabismic amblyopia (0.57 and 0.60; P = 0.03) compared to normal children (0.59 and 0.66; P = 0.03). 

Angle of Strabismus and Visual Field Parameters

Excluding normal children, there were no significant linear correlations between the angle of esotropia and horizontal extent (P = 0.29, R ² = 0.13) or area (P = 0.14, R ² = 0.22) of the BVF. If, however, normal children were included (i.e., zero angle of esotropia), there were significant linear correlations between BVF and angle of strabismus, for both horizontal extent (P = 0.003, R ² = 0.13) and area (P = 0.01, R ² = 0.17). 

Children with Strabismic (Esotropia) Amblyopia Undergoing Surgery

Thirteen of the 28 children underwent surgery for correction of the esotropia (Tables 3 and 4) . The mean age was 109.5 ± 29.62 months. The mean refractive error was 4.45 0.36 × 123.57 and 3.49 0.13 × 66.17 in the amblyopic and fellow eyes, respectively, with an interocular difference of −1.00 +0.44 × 42.22 (P = 0.07). The mean preoperative and postoperative angle of esotropia was 32.5 ± 9.5 PD and 9.1 ± 9.6 PD, respectively. These children had undergone between 3 and 6 months of FTO. The mean VA (LogMAR units) of the amblyopic and fellow eyes was 0.24 ± 0.21 and 0.02 ± 0.14, respectively. One child, who had no demonstrable binocularity preoperatively, achieved alignment postoperatively with 40” of stereoacuity. The remaining children did not show any apparent binocularity after surgery (Worth 4 Dot test or Bagolini striate glasses). 

There were no significant differences in the preoperative and postoperative extent of either the vertical (P > 0.33) or horizontal (P > 0.25) MVF, and no significant change in the vertical extent of the BVF (P = 0.35). The ratio of the BH/MH and BA/MA increased from 0.57 to 0.61 ± 0.03 (P = 0.003) and from 0.61 to 0.69 ± 0.07 (P = 0.003) pre- to postoperatively (Table 3) . This represented an increase of 8.5% in the BH/MH and 15.3% in the BA/MA. There was a significant correlation between the preoperative BVF measured in the presence of a prism equivalent to the angle of esotropia and the postoperative BVF for both horizontal extent and area (R ² = 0.83, P = 0.0001, R ² = 0.81, P = 0.001). Using a multivariate regression analysis between the preoperative values, preoperative values using a prism and the postoperative results, the preoperative values without the use of a prism did not contribute significantly either for the horizontal extent (P = 0.13) or the visual field area (P = 0.60), while the preoperative values in the presence of a prism did contribute significantly (P = 0.031 and P = 0.030). The linear regression equation for the horizontal extent of the BVF was Postop BH = −2.7 + 1.08 × Preop Prism BH (Fig. 1) . For example, if the preoperative horizontal extent of the BVF was 110, then the predicted postoperative BH would be 116, with a 95% confidence interval (CI) for the expected mean of 108–124 and a prediction interval of 86–146, given a preoperative prism BH of 110. The postoperative BVF parameters were also assessed using a prism to correct and residual postoperative deviation greater than 10 prism diopters. Although there was a slight increase in the correlation between the preoperative BVF parameters with a corrective prism and the postoperative BVF with a corrective prism, there were too few cases for a meaningful analysis. 

Visual Field Repeatability

Of the 15 children who had repeat VF measurements, 7 had strabismic amblyopia, and 8 had normal visual functions. The changes or differences in the preoperative VF were compared to repeat VF. For the monocular parameters, the differences between the preoperative and postoperative VF parameters were not significantly different from the differences between the repeat VF measurements (P > 0.12). For the binocular parameters, the increase in the BVF postoperatively was, however, significantly greater than the difference in the repeat fields for horizontal extent (P = 0.02) and area (P = 0.02). The variances for the pre- to postoperative VF were significantly greater than the variance between the repeat fields for the monocular and binocular measurements (P < 0.046) apart from the horizontal extent of the BVF (P = 0.055). 

Change in Pre- and Postoperative Binocular Visual Field

Eight out of 13 children showed an increase in the horizontal extent and area of their BVF above the 95% upper confidence interval (UCL) of the difference of those children who had repeated VF, with one patient showing a decrease in the postoperative binocular horizontal extent below the 95% lower confidence interval (LCL), and another below the 95% LCL for change in area. Four patients showed no change outside the 95% CI for the horizontal extent and 3 for the area of the BVF. Both patients who showed a decrease in the extent of their postoperative BVF, also showed a reduction in the BVF in the presence of a prism compared to the preoperative field. One patient showed a reduction in the area of the BVF in the presence of a prism but did not show any significant change in the postoperative binocular field. 

Normal Children Compared to Children with Strabismic Amblyopia Pre- and Postoperatively

There were no significant differences in the MVF measurements in normal children compared to the children with strabismic amblyopia either pre- or postoperatively (P > 0.09, P > 0.09). The horizontal extent and area of the BVF and binocular/monocular ratio field measurements were significantly smaller preoperatively in children with strabismic amblyopia than in normal children (P = 0.02). Postoperatively, however, there were no significant differences in any of these measurements compared to normal children (P > 0.16). There were no significant differences in the extent of the vertical BVF between normal children and those children with esotropia either pre- or postoperatively (P = 0.07 and P = 0.16). 

Visual Field Measurement 1.5 Years after Surgery

Nine of the 13 children were available for repeat VF measurements at approximately 1.5 years (mean 17.2 ± 2.8 months) after surgery. The residual ocular deviation (7.90 ± 8.14 PD) was not significantly different from their deviation at the time of their postoperative VF measurement (Table 4) . Excluding one patient who at 1.5 years showed a 135% increase in her binocular horizontal extent compared to the pre- and 6-week postoperative measurement, there was a 4.1 ± 19% and 10.4 ± 37.2% increase in the field parameters at 1.5 years compared to the first postoperative values. The change in field compared to the preoperative values was 12.6 ± 20.3% and 25.5 ± 31.9%. The patient (aged 5 years pre- and 6-week postoperatively, and 7 years at 1.5 years postoperatively) who demonstrated a 135% increase in the horizontal extent of BVF, also showed a 400% increase in the area of her BVF and a 114% increase in the vertical extent of her BVF compared to her preoperative and 6-week postoperative values. This likely reflected improved cognition in performing the test, as her MVF parameters had also increased substantially: horizontal extent 114 to 123%, vertical extent 93 to 135%, and area 300 to 439%. Despite the increase in her fields, her BH/MH and BA/MA were both reduced by −9% and −24% compared to the 6-week postoperative values. Overall, the changes in BH/MH and BA/MA at 1.5 years compared to the preoperative and 6-week postoperative values were 4.58 ± 4.52% and 8.78 ± 9.62%, and −2.33 ± 6.93% and −9.12 ± 11.58%, respectively. In essence, at 1.5 years there was a slight reduction in the binocular use of summed monocular fields compared to the 6-week postoperative value. 

Changes in Esotropia and Visual Field

There were no significant linear correlations between the change in angle of esotropia and the change in horizontal extent and area of the BVF, either 0.25 years postoperatively (P = 0.60, R ² = 0.05, P = 0.62, R ² = 0.04) or at 1.5 years postoperatively (P = 0.89, R ² = 0.02, P = 0.93, R ² = 0.01). 

Discussion

The BVF comprises the sum of the overlapping MVF. It is important for occupational, social, and personal safety reasons. ^{12 13} Although patients with esotropia tend to have a reduction in BVF, it is not clear whether this causes any disability. ^{1 2 3 4} The BVF has, however, been reported to change after strabismus surgery with potential benefit to the patient. ^{3 4} It has been suggested that the improvement in the BVF after surgery is due to a change in the angle of deviation. ³ If this is correct, then measurement of the BVF in the presence of a prism equal to the angle of deviation should produce a BVF similar to that which would be obtained after strabismic surgery. Any difference would then be expected to be due to the residual postoperative deviation. This, however, assumes that a prism has no intrinsic or other effect on the visual field. The effect of a prism on the VF was therefore initially measured in a group of normal adults. It appeared that the presence of horizontally aligned prisms, from a 10 PD base-in to a 25 PD base-out range, had no apparent effect on the overall size of the MVF or BVF (providing fusion could be maintained) of subjects with good binocularity. 

The reliability of testing VFs in children is of particular concern, since the series of examination relies on the child’s attention and patience. Although difficulties in maintaining stable fixation are common, many children show high levels of reliability, so that a quantified examination is possible in most children above the age of 5 years. ¹⁴ More reproducible results have usually been obtained using manual rather than automated kinetic perimetry. ^{15 16} The finding of reduced MVF and BVF in normal children compared to adults in this study, is likely to reflect a better conceptual understanding by adults in performing the test, although it may also reflect a difference in retinal sensitivity. ¹⁷ Kinetic visual field performance improves markedly between ages of 5 and 6 years and this could explain the fourfold increase in size of the postoperative VF in one of the children with esotropia at 1.5 years of follow up. 

There was a variance in VF parameters both within and between subjects, but it is unclear if the variance in the VF was also dependent on abnormalities in the VF. Any change in the VF, therefore, needs to be compared to variances of both the normal and abnormal VF. In view of this, to determine the repeatability of VF in children and to compare the VF of the amblyopic to fellow eyes, the VF was recorded in children, both with and without strabismic amblyopia. This data was then used to construct 95% CI on which to compare changes in the preoperative and postoperative VF. Our study demonstrated that children with esotropic strabismus had a reduced horizontal BVF extent compared to normal children. An effect of surgery was to reduce the difference in the extent of the BVF between children with esotropic amblyopia and normal children, consistent with previous reports. ^{1 2 3 4} Thus after surgery, there were no significant differences in either the extent of the BVF or ratio of BVF to MVF between children with and without strabismic esotropic amblyopia. Furthermore, the mean difference between the pre- and postoperative BVF measurements was significantly greater than the difference in repeated measurements of the BVF in normal children and those with strabismic amblyopia. 

The average total horizontal extent of the BVF in our esotropic patients (119°) was less than the age-matched normal children (138°). The significant reduction in the horizontal extent and area of the BVF in children with esotropia compared to normal children most likely reflected a combination of ocular alignment and suppression of the amblyopic eye during binocular viewing. Although wearing spectacles to correct a hypermetropic refractive error may have contributed to the difference in VF between normal and children with strabismus, the differences in VF were no longer apparent postoperatively in those children who underwent surgery. If only ocular alignment accounted for this difference, then a good correlation between angle of strabismus and BVF would have been expected. There was, however, no significant linear correlation between the change in angle of esotropia and change in the extent of the BVF. It is possible that a better correlation might have been found with a larger sample size and better postoperative ocular alignment. For example, although Kushner did not specifically determine whether there was a correlation between the change in angle and field gain, if the results in his study are analyzed, there is a highly significant linear between both the change in angle and field gain (R ² = 0.80, P = 6 × 10⁻¹³) and also between the size of the preoperative angle and field gain (R ² = 0.64, P = 6 × 10^-9) with coefficients of almost 1 (0.99) between the change in angle and field gain. ³ This suggests that at least 80% of the effect on field gain can be accounted for by the reduction in angle of esotropia. Furthermore, it is unlikely that the expansion in the BVF was due to a change in MVF, as the differences between the pre- and postoperative MVF did not differ significantly from the changes in the repeat MVF. In addition, although the effect of amblyopia on the extent of the VF is less clear, ^{1 2 4 5 8 18 19 20 21} most studies suggest little change in the extent of the MVF in amblyopia, which is consistent with our findings in subjects with and without amblyopia. 

The change in the BVF after surgery may differ between children and adults. Not all children showed an increase in their BVFs postoperatively, with four children showing differences within the UCL and LCL, and one child showing a reduction in the horizontal extent of the BVF below the 95% CI. Although it is unclear, however, whether there would have been a greater improvement had the children achieved better ocular alignment, there was no further improvement in the postoperative BVF measured with the patient wearing a prism equal to the residual postoperative deviation. In contrast, Wortham reported on the horizontal extent of the BVF in 10 adult esotropes undergoing surgery, and in all cases, there was expansion of BVF by an amount approximately commensurate with the changes in the angle of strabismic deviation. ⁴ A subjective improvement in peripheral vision was also appreciated by a number of patients. Similarly, Kushner reported on a series of 37 adults undergoing surgery for esotropia and noted an expansion of the BVF in all but one. ³ Although there may be an intrinsic difference in the response of adults and children undergoing surgery for large angle esotropia, without a control group it would be difficult to determine what constitutes a significant change in the VF. Whether those children who did not show a change in BVF or whose BVF reduced after surgery, readapted to their ocular alignment by further suppression of their peripheral field is unknown. The two children who showed a reduction in the postoperative BVF, however, also showed a reduction in the preoperative field in the presence of a prism, which would suggest that there was no change in the area of suppression after surgery. Although one patient showed a marked improvement in binocularity, the absence of any measured binocularity in the remaining children (apart from an increase in the extent of the binocular field) may reflect their postoperative ocular alignment. It is also possible that the fairly prolonged periods of FTO (3 to 6 months) may have contributed to the poor postoperative binocularity. As all the patients had received similar amounts of FTO, it was not possible to determine whether this was a contributing factor in determining outcome in terms of the VF after surgery. 

The change in the BVF after surgery appeared to be stable with patients maintaining their BVF up to 2 years postoperatively. It would appear that in children with large angle esotropia, approximately 80% of the change in the postoperative BVF could be predicted by measuring the preoperative BVF in the presence of a prism equal to the angle of deviation. The ability to predict which patients are likely to achieve an expansion of the BVF may help in the counseling of patients due to have surgery for large angle esotropia. 

 Submitted for publication August 29, 2003; revised December 14, 2003 and January 19, 2004; accepted February 2, 2004.

 Disclosure: S.A. Quah, None; S.B. Kaye, None

 The publication costs of this article were defrayed in part by page charge payment. This article must therefore be marked “advertisement” in accordance with 18 U.S.C. §1734 solely to indicate this fact.

Table 1.

 

 

Extent and Area of Monocular and Binocular Adult Visual Field in Presence of Prism

Table 1.

 

Extent and Area of Monocular and Binocular Adult Visual Field in Presence of Prism

Prism (PD)	MV	MH	MA	BV	BH	BA	BH/MH	BA/MA
+0	114	138	191	123	162	246	0.59	0.65
−10	109	138	196	118	157	230	0.57	0.59
+2	117	137	198	120	159	239	0.58	0.61
+10	113	135	192	114	154	233	0.57	0.61
+20	116	137	190	120	159	236	0.58	0.62
+30	113	133	188	118	152	226	0.57	0.60

 Mean monocular and binocular vertical (MV, BV) and horizontal (MH, BH) visual field in degrees, and area (MA and BA) in cm². Ratio of BVF to sum of MVF for horizontal extent (BH/MH) and area (BA/MA). PD, prism diopters; (−), base-in prism; (+), base-out prism.

Table 2.

 

 

Visual Field in Children Without and With Esotropia

Table 2.

 

Visual Field in Children Without and With Esotropia

	MV	MH	MA	BV	BH	BA	BH/MH	BA/MA
Normal Children
Mean	104	116	144	115	138	192	0.59	0.66
SD	12	13	30	10	15	34	0.03	0.08
Range	48	50	111	38	51	129	0.10	0.28
LCL	98	111	131	111	132	177	0.58	0.63
UCL	110	122	158	120	145	208	0.61	0.70
Children with Esotropia
Mean	101	106	132	107	120	159	0.56	0.61
SD	20	20	42	20	26	55	0.05	0.09
Range	77	89	177	91	115	220	0.21	0.39
LCL	92	97	114	99	109	135	0.54	0.57
UCL	109	114	150	116	131	182	0.59	0.65

 Standard deviation (SD), range, lower (LCL) and upper (UCL) 95% confidence intervals. Monocular vertical (MV) and horizontal (MH) extent in degrees; and area (MA) in cm² (only right eyes shown) Binocular vertical (BV) and horizontal (BH) extent in degrees and area (BA) in cm². Ratio of binocular to summed monocular visual field for horizontal extent (BH/MH) and area (BA/MA).

Table 3.

 

 

Preoperative (With and Without Prism) and Postoperative Visual Fields after Surgery for Large Angle Esotropia

Table 3.

 

Preoperative (With and Without Prism) and Postoperative Visual Fields after Surgery for Large Angle Esotropia

	MV	MH	MA	BV	BH	BA	BH/MH	BA/MA
Preoperative Visual Field Measurements
Mean	97	103	124	103	118	149	0.56	0.60
SD	22	23	46	20	29	55	0.04	0.06
Range	76	89	177	76	115	205	0.15	0.22
LCL	85	91	99	93	103	120	0.54	0.57
UCL	108	116	148	114	134	179	0.59	0.64
Preoperative Visual Field with Prism to Correct Angle of Esotropia
Mean	96	103	118	104	123	156	0.60	0.65
SD	19	18	37	18	24	49	0.06	0.07
Range	68	68	134	62	79	158	0.21	0.27
LCL	85	93	98	95	110	129	0.56	0.60
UCL	106	113	138	114	137	183	0.64	0.70
Postoperative Visual Field Measurements at 0.25 years
Mean	97	109	129	107	130	174	0.61	0.69
SD	18	21	41	20	29	56	0.03	0.07
Range	60	74	113	43	101	147	0.09	0.26
LCL	87	98	107	96	115	144	0.59	0.65
UCL	106	121	151	117	146	205	0.63	0.73

 Mean, standard deviation (SD), range, lower (LCL) and upper (UCL) 95% confidence intervals. Monocular vertical (MV) and horizontal (MH) extent in degrees; and area (MA) in cm². Binocular vertical (BV) and horizontal (BH) extent in degrees and area (BA) in cm². Ratio of binocular to summed monocular visual field for horizontal extent (BH/MH) and area (BA/MA). The prism was placed in front of the amblyopic eye (if deviation greater than 35 PD, prism was split between eyes) and the monocular and binocular visual fields measured.

Table 4.

 

 

Preoperative and Postoperative Changes in Angle of Strabismus and Visual Field Parameters

Table 4.

 

Preoperative and Postoperative Changes in Angle of Strabismus and Visual Field Parameters

VA OD, OS	Angle Preop (Postop 0.25, 1.5 yrs)	Angle Change (%) 0.25 (1.5) yrs	BH Preop (Preop with prism)	BH Postop 0.25 yrs (change %)	BA Change (%) at 0.25 yrs	BH Postop 1.5 yrs (change %)	BA Change (%) at 1.5 yrs
0.3, 0.3	25 (1, 1)	96 (96)	165 (148)	143 (−14)	−5	143 (−14)	−8
0.2, 0.1	70 (20, 20)	71 (71)	86 (88)	86 (0)	−13	132 (53)	82
0.3, 0.0	40 (6, NA)	85 (NA)	128 (110)	133 (4)	1	NA	NA
−0.1, 0.18	35 (18, 20)	49 (43)	50 (68)	59 (18)	55	118 (135)	400
0.0, 0.78	35 (5, 14)	86 (60)	133 (146)	154 (16)	38	142 (6)	31
0.10, 0.0	45 (20, NA)	56 (NA)	124 (122)	144 (16)	13	NA	NA
0.2, 0.30	30 (5, 2)	83 (93)	125 (136)	127 (1)	4	127 (1)	1
0.18, 0.0	40 (2, 0)	95 (100)	104 (124)	143 (38)	89	142 (36)	70
−0.2, 0.18	30 (14, 14)	53 (53)	147 (148)	160 (9)	3	147 (0)	−2
0.48, 0.18	40 (2, 4)	95 (90)	131 (145)	146 (12)	17	152 (16)	17
−0.10, 0.00	30 (4, 2)	87 (93)	103 (124)	117 (14)	30	111 (8)	34
0.00, −0.10	35 (6, NA)	83 (NA)	110 (128)	147 (33)	40	NA	NA
0.00, 0.20	45 (8, 2)	82 (96)	131 (121)	136 (4)	−3	139 (6)	5
Mean	39 (9)	79 (78)	118 (124)	130 (12)	21	135 (13)	48
SD	11 (7)	9 (10)	29 (24)	29 (14)	29	13 (20)	109

 Visual acuity (VA) in LogMAR units right and left. Angle of strabismus in prism dioptres and change in angle as a percentage (%) at 0.25 years and at 1.5 years. Extent of horizontal binocular visual field (BH) in degrees and percentage change in BH and binocular area (BA) (cm²) at 0.25 years and 1.5 years. NA, not available at follow-up.

Figure 1.

 

The linear regression equation for the horizontal extent of the BVF was postoperative BH = −2.7 + 1.08 × preoperative Prism BH. Horizontal extent (degrees) of postoperative binocular visual field (BVF) and preoperative BVF in the presence of a prism equal to the angle of esotropia.