Factors Affecting Contrast Sensitivity in Intermittent Exotropia

Analysis of Changes in High-order Aberration and Contrast Sensitivity After Epiblepharon Surgery

PURPOSE

To investigate changes in corneal anterior high-order aberration (HOA) and contrast sensitivity (CS) before and after epiblepharon surgery.

METHODS

A retrospective observational analysis of the degree of corneal erosion, HOAs and CS was conducted in the OD and OS, respectively, before and after epiblepharon surgery. The correlations between corneal erosion, HOAs, and CS were analyzed.

RESULTS

Forty-nine patients were included in the study. Among the anterior HOAs, total HOA, coma, and trefoil showed significant improvement after surgery ( P = 0.003, P = 0.009, and P = 0.018, respectively). In the CS test, there was a significant improvement in CS after surgery at 1.1 cycles per degree (cpd) under photopic conditions, regardless of glare. Preoperative correlation analysis between HOAs and corneal erosion showed a significant positive correlation with total HOA ( P = 0.001) and coma ( P = 0.001). Preoperative correlation analysis between CS and corneal erosion showed a significant negative correlation at 1.1 cpd with glare under photopic conditions ( P = 0.049). A negative correlation was also observed between CS under mesopic and photopic conditions and total HOA both before and after surgery.

CONCLUSION

Significant improvement in corneal anterior HOAs and CS at 1.1 cpd under photopic conditions was observed after epiblepharon surgery. Total HOA of anterior cornea showed a negative correlation with CS. A decrease in HOAs and recovery of corneal erosion after epiblepharon surgery will help improve CS.

Binocular contrast sensitivity in patients with intermittent exotropia in relation to angle of strabismus and level of compensation

Intermittent exotropia (IXT) causes photophobia, and photophobia has been studied by measurement of contrast sensitivity (CS). CS was reduced in children with IXT. We compared binocular CS (BCS) in patients with IXT and normal subjects in relation to the angle of strabismus and control of IXT. This case-control study was performed on 40 patients with IXT and 40 normal subjects who were examined with the CSV1000 CS device in mesopic (3 cd/m2) and photopic (85 cd/m2) conditions with and without a glare stimulus at 3, 6, 12, and 18 cycle/degree (cpd) spatial frequencies. The angle of strabismus and near stereoacuity were also measured. The patient's IXT compensation was graded based on the office control scale. The mean age for IXT and normal participants were 12.30 ± 0.60 (range, 6-18) and 11.00 ± 0.78 (range, 6-18) years, respectively (P = .34). The IXT patients had lower binocular CS than controls at all spatial frequencies (P < .001). The largest decrease in CS occurred at 6 cpd spatial frequency under mesopic condition (1.61 ± 0.07 vs 1.38 ± 0.15, P < .001) and photopic condition with glare (2.03 ± 0.06 vs 1.77 ± 0.13, P < .001). Patients with better control scores had higher levels of BCS; also, the score of BCS showed a significant decrease in patients with a deviation of 25 prism diopter or more, compared to those with less deviation. BCS correlated at 3 and 6 cpd with near stereoacuity (r = -0.652, P < .001 and r = -0.613, P < .001). Binocular CS in patients with IXT correlates with the angle of strabismus and level of compensation.

Changes in contrast sensitivity after surgery for intermittent exotropia

To determine whether intermittent exotropia (IXT) surgery affects contrast sensitivity (CS), this retrospective study evaluated the changes in monocular and binocular CS and the binocular summation ratio (BSR) quantified as the ratio between the values of the binocular and the better monocular CS score (BSR = binocular CS score/better monocular CS score) after surgery for IXT. The subjects were patients who had undergone IXT-correcting surgery with a postoperative follow-up of > 3 months and had pre- and postoperative records of Mars CS test scores. In total, 64 patients (128 eyes) were evaluated. Both the binocular and monocular CS scores of the operated eyes were significantly worse on postoperative 1 day than the preoperative scores, but they were recovered after 1 week. The monocular CS scores of the operated eyes were significantly worse than those of the non-operated eyes until 1 week. There was no significant difference in monocular CS scores between the one-muscle and two-muscle surgeries and in binocular CS scores between the successful alignment and overcorrection groups even on the first day after surgery. The mean BSR was significantly decreased until postoperative month 1, however, recovered to preoperative levels after month 3. In conclusion, IXT-correcting surgery may temporarily worsen the CS, but it is recovered to preoperative levels. Thus, changes in CS in the immediate postoperative period after strabismus surgery should not be of concern.

Analysis of Improvement Time and Influencing Factors of Diplopia after Intermittent Exotropia in Children

Objective

To observe and analyze the occurrence rate, improvement time, and influencing factors of diplopia after intermittent exotropia in children.

Methods

A total of 135 children with intermittent exotropia treated in our hospital from February 2019 to April 2021 were recruited. A reasonable surgical plan was exerted according to the preoperative examination of the children, the children were divided into groups according to their age, degree of strabismus, visual acuity, and binocular visual function, and the postoperative diplopia occurrence rate and improvement time of diplopia in different groups were observed and compared.

Results

Postoperative diplopia occurred in 74 of 135 children with intermittent exotropia, and the postoperative incidence of diplopia was 54.81%. All diplopia occurred on the first day after the operation. There were 62 cases of contradictory diplopia (83.78%) and 12 cases of fusion of powerless diplopia (16.22%). Except for 1 case of amalgamated powerless diplopia, diplopia was not significantly improved after 6 months, which seriously affected the life of the children after the second operation, and all the others were significantly improved within 90 days. The improvement time of diplopia was 3-90 days, and the average improvement time of diplopia was 13.25 ± 3.16 days. According to their age, the children were divided into the 3-6 years old group (n = 69), the 7-10 years old group (n = 47), and the 11-14 years old group (n = 19). Postoperative diplopia occurred in 25 cases (36.23%) in the 3-6 years old group, 34 cases (72.34%) in the 7-10 years old group, and 16 cases (84.21%) in the 11-14 years old group. There was a significant difference in the incidence of postoperative diplopia among the three groups (P < 0.05). There was a significant difference in the improvement time of diplopia among the three groups (P < 0.05). According to the degree of strabismus before the operation, the children were divided into the <50△ group (n = 74) and the ≥50△ group (n = 61). Postoperative diplopia occurred in 32 cases (43.24%) in the <50△ group and 43 cases (70.49%) in the ≥50△ group. There was a significant difference in the incidence of postoperative diplopia between the two groups (P < 0.05). There was a significant difference in the improvement time of diplopia among the three groups (P < 0.05). According to the results of the visual acuity examination, the patients were divided into the ≥0.8 (naked eye) group (n = 21), the ≥0.8 (ametropia) group (n = 32), and the <0.8 (amblyopia) group (n = 32). Among them, diplopia occurred in 10 cases (47.62%) in the ≥0.8 (naked eye) group, 40 cases (48.78%) in the ≥0.8 (ametropia) group, and 24 cases (75.00%) in the <0.8 (amblyopia) group. The incidence of diplopia in the <0.8 (amblyopia) group was significantly higher than that in the ≥0.8 (naked eye) group and the ≥0.8 (ametropia) group, and the difference was statistically significant (P < 0.05). The postoperative diplopia improvement time in the <0.8 (amblyopia) group was significantly higher than that in the ≥0.8 (naked eye) group and the ≥0.8 (ametropia) group, and the difference was statistically significant (P < 0.05). There was no significant difference in diplopia occurrence rate and diplopia improvement time between the ≥0.8 (naked eye) group and the ≥0.8 (ametropia) group (P > 0.05). According to the results of binocular visual function examination, 92 cases had a primary function, 45 cases (48.91%) had diplopia after the operation, the average recovery time of diplopia was 12.58 ± 3.16, 43 cases had no primary function, and 30 cases (69.77%) had diplopia after the operation. The average recovery time of diplopia was 13.02 ± 3.84. There was a significant difference in the incidence of diplopia between the two groups (χ 2 = 5.162). There was no significant difference in the recovery time of diplopia between the two groups (χ 2 = 0.570, P < 0.05). In 80 cases with secondary function, diplopia occurred in 36 cases (45.00%), and the average recovery time of diplopia was 10.14 ± 2.88; in 55 cases without secondary function, diplopia occurred in 39 cases (70.91%), and the average recovery time of diplopia was 14.86 ± 3.73. There was a significant difference in the incidence of diplopia between the two groups (χ 2 = 8.861, P < 0.002). There was a significant difference in the recovery time of diplopia between the two groups (χ 2 = 6.469, P < 0.001). In 77 cases with tertiary function, diplopia occurred in 32 cases (41.56%), and the average recovery time of diplopia was 9.61 ± 2.39; in 58 cases without tertiary function, diplopia occurred in 43 cases (74.14%), and the average recovery time of diplopia was 13.11 ± 3.05. There was a significant difference in the incidence of diplopia between the two groups (χ 2 = 14.221 P < 0.001). There was a significant difference in the recovery time of diplopia between the two groups (χ 2 = 5.355, P < 0.001).

Conclusions

The age, degree of strabismus, visual acuity, and binocular visual function of children with intermittent exotropia are significant factors affecting the occurrence rate and recovery time of diplopia after the operation. The younger the age, the smaller the degree of strabismus, the better the vision and the second or third grade of visual function, the smaller the occurrence rate of diplopia, and the shorter the recovery time of diplopia. Thus, the above influencing factors have a certain guiding significance in predicting the improvement of postoperative diplopia and the time of diplopia disappearance. The purpose of intermittent exotropia surgery in children is not only to correct eye position and improve appearance but also to establish normal retinal correspondence in order to obtain binocular monocular function. Furthermore, postoperative diplopia in children with concomitant exotropia is very common; therefore, careful examination, comprehensive analysis, and surgical plan should be designed according to the above factors. Stereoscopic vision training as early as possible after the operation is beneficial to the establishment of normal retinal correspondence and the elimination of diplopia.