Journal List > J Korean Ophthalmol Soc > v.58(10) > 1010651

Lee, Lee, and Kyung: Comparison of Exodrift between Natural Group and Postoperative Group in Intermittent Exotropia Patients

Abstract

Purpose

To compare the exodrift between unilateral lateral rectus (ULR) recession and observation groups in moderate angle intermittent exotropia (IXT).

Methods

A retrospective study was performed in 769 patients who were diagnosed with IXT from 2005 to 2015. Seventy-six patients were enrolled in this study that presented with IXT of 20 to 25 prism diopters (PD) on their first visit and were observed for more than 6 months without or after operation. The observation group (group 1) was composed of 29 patients who had regular examination without operation. The surgery group (group 2) was composed of 47 patients with ULR recession that were observed for deviation changes since surgery.

Results

The mean age was 71.8 ± 22.0 months at first visit in group 1 and 91.1 ± 18.9 months before surgery in group 2 (p < 0.01). The distant exodeviation was 22.9 ± 2.5 PD at first visit in group 1 and 22.9 ± 2.4 PD before surgery in group 2 (p = 0.89). During follow-up, mean exodrift was 0.6 ± 9.0 PD in group 1 and 10.0 ± 7.4 PD in group 2 (p < 0.01). Exodrift up to postoperative 6 months in group 2 was 3.2 ± 4.0 PD and exodrift from postoperative 6 months to 2 years in group 2 was 7.1 ± 6.9 PD. More exodrift was noticed after post-operative 6 months (p = 0.04).

Conclusions

Comparing the exodrift between the groups in moderate angle IXT, patients in the observation group showed less exodrift. Patients who had a ULR recession presented more exodrift after postoperative 6 months. Even though they were ortho-tropic at postoperative 6 months when the operation was thought to be stabilized, an increase in exodrift after postoperative 6 months could not be excluded.

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Figure 1.
Exodrift 1 and exodrift 2 in each group. In group 2, exodrift 2 was 7.1 ± 6.9 PD which is more than exodrift 1 of 4.1 ± 5.7 (p = 0.01, paired t-test). Exodrift 1 was −0.5 ± 3.4 PD in group 1 and 4.4 ± 5.6 PD in group 2 and there was significant difference (p < 0.01, t-test). Exodrift 2 was 0.1 ± 4.0 PD in group 1 and 7.1 ± 6.9 PD in group 2 and there was significant difference (p < 0.01, t-test). Exodrift 1: difference of PD during first 1 year in group 1 and from postoperative 6 months to postoperative 18months in group 2. Exodrift 2: difference of PD during first 2 years in group 1 and from post-operative 6 months to postoperative 30 months in group 2. Post-OP = postoperative; mo = months.
jkos-58-1169f1.tif
Figure 2.
Kaplan-meier survival curve. Group 1 is the observation group who didn't have a surgery and group 2 is the surgery group who had a unilateral lateral recession. Exodrift more than 10 PD was plotted in the survival curve. These survival curve indicated that the estimated mean times to exodrift more than 10 PD were 8.3 ± 3.1 years in group 1 and 3.7 ±3.8 years in group 2. The cumulative probability of exodrift was sinificantly higher in group 2 than group 1 (p < 0.01, log rank test).
jkos-58-1169f2.tif
Table 1.
Surgical table for moderate angle intermittent exotropia
PD Unilateral LR recession (mm)
20 8.5
21–24 9
25 10

PD = prism diopters; LR = lateral rectus.

Table 2.
Clinical characteristics of Group 1 and 2
  Group 1 (n = 29) Group 2 (n = 47) p-value*
Demographics      
 Sex (male/female) 17/12 19/28 0.16
 Fusion at distance (good/fair/poor) 7/15/7 12/24/8 0.58
 Amblyopia 7 4 0.09
 Refractive errors (SE) –0.4 ± 2.2 (−10.0–1.75) –0.6±2.0 (−10.25–2.75) 0.72
 Anisometropia 3 0 0.05
 Age at the 1st examination (months) 71.8 ± 22.0 (44–131) 84.3 ± 23.6 (21–126) 0.02
 Follow up periods (months) 53.8 ± 29.4 (6–115) 44.9 ± 27.0 (6–99) 0.18
 Near stereopsis at first visit (arcsec) 74.0 ± 34.7 (25–200) 87.9 ± 78.1 (20–400) 0.52
Deviation      
 Distant deviation at 1st examination (PD) 22.9 ± 2.5 (20–25) 23.1 ± 3.8 (20–25) 0.85§
 Near deviation at 1st examination (PD) 24.5 ± 7.1 (8–35) 24.3 ± 4.9 (15–35) 0.88
 Distant deviation at post-OP about 6 months (PD)   5.2 ± 5.5 (−6–15)  
 Distant deviation at last visit (PD) 23.5 ± 8.7 (0–50) 12.2 ± 8.3 (−4–30) <0.01
Deviation drift      
 Exodrift (total) 0.6 ± 9.0 (−25–30) 10.0 ± 7.4 (−4–25) <0.01
 Exodrift during post-OP 6 months   3.2 ± 4.0 (−6–10)  
 Exodrift 1 –0.5 ± 3.4 (−8–5) 4.4 ± 5.6 (−5–20) <0.01
 Exodrift 2 0.1 ± 4.0 (−10–5) 7.1 ± 6.9 (−5–20) <0.01

Values are presented as mean ± SD unless otherwise indicated. ‘Group 1’ is ‘the patients who had regular examination about the deviation without operation’ and ‘Group 2’ is ‘the patients who had a unilateral lateral rectus recession’. ‘Exodrift (total)’ means ‘difference of PD between last visit and first visit in group 1 and between last visit and post-operative day 1 in group 2’. ‘Exodrift 1’ means ‘difference of PD during first 1 year in group 1 and from postoperative 6 months to postoperative 18 months in group 2’. ‘Exodrift 2’ means ‘difference of PD during 2 years in group 1 and from postoperative 6 months to postoperative 30 months in group 2’.

SE = spherical equivalent; PD = prism diopters; post-OP = postoperative.

* p-value by student t-test

p-value by Fisher's exact test

The difference of the age between group 1 (71.8 ± 22.0) at first examination and group 2 (91.1 ± 18.9) at operation was also significantly efficient (p < 0.01, t-test)

§ The difference of distant deviation between group 1 (22.9 ± 2.5) at first examination and group 2 (22.9 ± 2.4) at operation was also not significantly efficient (p = 0.89, t-test).

Table 3.
The number of patient according to amount of total exodrift in group 1 and group 2
  Group 1 Group 2
Total exodrift* ≤ −6 PD 4 (13.8) 0 (0)
Total exodrift > −6 PD and ≤ 10 PD 24 (82.8) 21 (44.7)
Total exodrift > 10 PD 1 (3.4) 26 (55.3)

Values are presented as n (%). ‘Group 1’ is ‘the patients who had regular examination about the deviation without operation’ and ‘Group 2’ is ‘the patients who had a unilateral lateral rectus recession’. PD = prism diopters.

* Total exodrift was defined by subtraction; difference between final deviation and first visit deviation in group 1, difference between final deviation and postoperative first deviation in group 2

Esotropia was calculated as minus number. The negative number of exodrift means decrease of exotropia deviation.

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