Changes in the Effects of Bilateral Lateral Rectus Muscle Recession According to Preoperative Angle Deviation

Sung Ha Hwang; Hae Jung Paik

doi:10.3341/jkos.2020.61.3.281

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Hwang and Paik: Changes in the Effects of Bilateral Lateral Rectus Muscle Recession According to Preoperative Angle Deviation

Original Article

J Korean Ophthalmol Soc 2020;61(3):281-287.

Published online: 25 September 2020

DOI: https://doi.org/10.3341/jkos.2020.61.3.281

Changes in the Effects of Bilateral Lateral Rectus Muscle Recession According to Preoperative Angle Deviation

Sung Ha Hwang, MD, Hae Jung Paik, MD, PhD

Department of Ophthalmology, Gachon University Gil Medical Center, Incheon, Korea

Address reprint requests to Hae Jung Paik, MD, PhD Department of Ophthalmology, Gachon University Gil Medical Center, #21 Namdong-daero 774beon-gil, Namdong-gu, Incheon 21565, Korea Tel: 82-32-460-3351, Fax: 82-32-460-3009 E-mail: hjpaik@gilhospital.com

Received 12 February 2019 Revised 22 April 2019 Accepted 21 February 2020

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To investigate how the effect of bilateral rectus muscle recession changed by analyzing the effect/dose ratio of surgery according to the preoperative angle deviation.

Methods

We retrospectively studied the medical records of patients from January 2007 to March 2014 who underwent bilateral lateral rectus muscle recession and who visited our hospital for at least 2 years after surgery. We classified the patients into two groups: the preoperative large angle deviation group (35 prism diopters [PD] or more) and the small angle deviation group (20 PD or less). We observed exodrift patterns by measuring distant and near angle deviation according to the preoperative and postoperative times. The effect/dose ratio of recession was calculated at each visit. Surgical success was defined as an alignment between 10 PD of exodeviation and 5 PD of esodeviation, both at distance and at near.

Results

Among 165 patients, 84 patients were in the large angle deviation group and 81 patients were in the small angle deviation group. Preoperative angle deviation of the large angle deviation group was 39.34 ± 5.13 PD (range: 35–55 PD) and the small angle deviation group was 19.49 ± 1.62 PD (range: 18–20 PD) (p < 0.001). At postoperative 1 day, the alignments of eyes of the two groups were −8.32 ± 9.31 PD and −13.11 ± 6.94 PD; p < 0.001, respectively. At the date of the final follow-up, the alignments of eyes of the two groups were 4.63 ± 8.94 PD and 1.22 ± 8.01 PD; p = 0.011, respectively, and the effect/dose ratios were 2.25 ± 0.62 PD/mm and 1.94 ± 0.78 PD/mm, respectively, which meant that the effect of correction for the large angle deviation group was larger than that of the small angle deviation group (p = 0.005). Both groups showed postoperative exodrift patterns and similar success rates (75.0% and 80.2%, respectively), which showed no significant difference (p = 0.268).

Conclusions

The small angle deviation group showed a larger effect of correction and high exodrift pattern at the postoperative initial time and the large angle deviation group showed a smaller effect of correction and low exodrift pattern at the postoperative initial time. The preoperative angles of deviation and the operative success rates were not related.

Keywords: Bilateral lateral rectus muscle recession, Intermittent exotropia

References

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Figure 1.

Changes in angle of deviation at distance during post-operative follow-up. Mean angle of deviation showed significant difference at all dates. ^* Mann-Whitney U-test (p < 0.05).

Figure 2.

Change in amount of corrected prism diopters (PD) per lateral recession (mm) in large angle and small angle groups (dose-effect relationship). Mean PD/mm showed significant difference at postoperative 1 day, 1 year, 2 years and last follow-up. ^* Mann-Whitney U-test (p < 0.05).

Figure 3.

Diagram of lateral rectus (LR) muscle and other structures. (A) Pulley of LR is located 2–4 mm posterior to the equator originally. (B) After large amount of recession on LR, pulley is translocated largely to the lateral side and causes strong passive elastic tension, which has the exodeviation force. (C) After small amount of recession on LR, pulley is translocated smally to the lateral side and causes weak passive elastic tension initially. (D) At the final state after small recession of LR, as the pulley is deviated later-ally, passive elastic tension becomes strong. LR = lateral rectus muscle.

Table 1.

Surgical dosages of bilateral rectus recession for exotropia

Prism diopter	LR recession (mm) in BLR
18–20	4.5–5.0
35–40	7.5–8.0
41–45	8.0–8.5
46–50	8.5–9.0
51–55	9.0–9.5

LR = lateral rectus muscle; BLR = bilateral lateral rectus muscle recession.

Table 2.

Preoperative characteristics of large angle and small angle group

Charecteristic	Large angle group (n = 84)		Small angle group (n = 81)		p-value
Charecteristic	Average	Range	Average	Range	p-value
Sex (male/female)	37/47	–	45/36	–	0.162^*
Age at surgery (years)	8.46 ± 8.77	2 to 44	7.58 ± 2.36	4 to 18	0.092^†
Follow-up (months)	42.03 ± 26.44	26 to 120	42.90 ± 23.25	24 to 112	0.824^†
BCVA (logMAR)	0.06 ± 0.24	0.00 to 0.18	0.06 ± 0.42	0.00 to 0.18	0.866^†
Spherical equivalent (diopters)	–0.73 ± 1.92	–5.50 to 1.25	–0.78 ± 1.65	–3.75 to 3.00	0.869^†
Anisometropia (diopters)	0.15 ± 0.32	0.00 to 1.75	0.18 ± 0.16	0.00 to 1.00	0.711^†
Stereopsis (good/total)	75/84	–	78/81	–	0.081^*
Amount of recession (mm)	7.68 ± 0.64	7.50 to 9.25	4.93 ± 0.32	4.50 to 5.00	<0.001
Preoperative angle deviation (PD)	39.34 ± 5.13	35 to 55	19.49 ± 1.62	18 to 20	<0.001^†

Values are presented as mean ± standard deviation unless otherwise indicated. Good stereopsis ≤100 seconds by Titmus stereopsis test.

BCVA = best-corrected visual acuity; PD = prism diopters.

^* Fisher's exact test

^† Mann-Whitney U-test.

Table 3.

Angle of deviation at distance during postoperative follow-up

Follow-up period	Large angle group (n = 84)	Small angle group (n = 81)	p-value^*
1 day (PD)	–8.32 ± 9.31	–13.11 ± 6.94	<0.001
1 month (PD)	3.02 ± 8.33	–1.72 ± 5.11	<0.001
6 months (PD)	2.80 ± 7.86	–2.67 ± 7.05	<0.001
1 year (PD)	3.68 ± 8.05	–0.50 ± 6.10	0.001
2 years (PD)	4.44 ± 8.51	0.98 ± 6.21	0.008
Last follow-up (PD)	4.63 ± 8.94	1.22 ± 8.01	0.011

Values are presented as mean ± standard deviation.

PD = prism diopters.

^* p-values by Mann-Whitney U-test, significant p-value level is <0.05.

Table 4.

The amount of corrected prism diopters per lateral recession (mm) in large angle and small angle groups (dose-effect relationship)

Follow-up period	Large angle group (n = 84)	Small angle group (n = 81)	p-value^*
1 day (PD/mm)	3.11 ± 0.57	3.38 ± 0.67	0.006
1 month (PD/mm)	2.36 ± 0.52	2.24 ± 0.53	0.124
6 months (PD/mm)	2.37 ± 0.50	2.33 ± 0.70	0.664
1 year (PD/mm)	2.35 ± 2.11	2.11 ± 0.60	0.005
2 years (PD/mm)	2.33 ± 0.53	1.97 ± 0.63	<0.001
Last follow-up (PD/mm)	2.25 ± 0.63	1.94 ± 0.79	0.005

Values are presented as mean ± standard deviation.

PD = prism diopters.

^* p-values by Mann-Whitney U-test, significant p-value level is <0.05.

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