Outcome of Unilateral Lateral Rectus Resection in Patients with Age-Related Distance Esotropia

Abstract

Purpose: We sought to evaluate the surgical outcomes of unilateral lateral rectus (LR) resection among patients with age-related distance esotropia (ARDE). Methods: We conducted a retrospective review of 39 patients who underwent unilateral LR resection for ARDE between January 2019 and November 2024 performed by a single surgeon at a tertiary eye centre in Brisbane, Queensland. The inclusion criteria included symptomatic horizontal diplopia at distance, comitant esotropia that was at least 25% greater at a distance than nearby, and absence of an abduction deficit or neurologic abnormality. In all but one procedure, an adjustable-suture technique was used. The amount of LR resection was based on a 1 mm per 4 prism dioptre (PD) personal surgical table. Pre- and postoperative measurements of deviation close up at near (33 cm) and at a distance (6 m) were obtained using prism and alternate cover testing. Results: The mean (±SD) patient age was 68.1 ± 9.7 years (range: 44–91). The mean preoperative esotropia measured 14.3 ± 2.7 PD at a distance and 4.7 ± 3.3 PD nearby. The mean LR resection was 3.8 ± 0.7 mm (range: 3.0–6.0 mm), with a mean follow-up of 18 months (range: 9–26). Diplopia was resolved in 97% (38/39) of the patients. At the final follow-up, 85% (33/39) were orthophoric at a distance, and all were orthophoric nearby. Five patients (13%) required postoperative adjustment, four of whom achieved orthophoria. Three patients had minimal residual esotropia (<5 PD). Conclusions: Unilateral LR resection with adjustable sutures provides a safe, effective, and targeted surgical option for ARDE, achieving high rates of distance orthophoria and diplopia resolution without compromising near alignment. Prospective long-term studies are warranted to confirm durability and refine surgical dosing.

1. Introduction

Age-related distance esotropia (ARDE), also termed divergence-insufficiency-type esotropia, is an increasingly recognised form of adult-onset strabismus that primarily affects older individuals. It is characterised by a comitant esodeviation that is greater at a distance than nearby, leading to symptomatic diplopia during distance fixation, while close visual tasks remain relatively unaffected [1,2,3,4,5]. With an ageing global population, ARDE is being encountered more frequently in clinical practice and now represents a significant subset of adult strabismus cases [6,7].

Clinically, ARDE typically presents in patients over the age of 60 years with gradually progressive horizontal diplopia. Symptoms often begin intermittently and worsen over time, particularly during activities requiring sustained distance fixation such as driving or watching television. Despite relatively small angles of deviation, patients are often highly symptomatic due to reduced fusional divergence amplitudes associated with ageing [8]. This reduction in compensatory mechanisms contributes to the disproportionate functional impairment observed in ARDE.

A major diagnostic challenge in ARDE is its overlap with neurogenic causes of diplopia, particularly sixth-cranial-nerve palsy. Both conditions may feature distance esotropia; however, ARDE is distinguished by full ocular ductions, normal saccadic velocities, and an absence of neurological signs [2,8]. Carrying out a careful clinical assessment and applying appropriate imaging are essential to exclude alternative diagnoses such as intracranial pathology, myasthenia gravis, and thyroid eye disease.

Historically, divergence insufficiency was thought to arise from a central neurological deficit. However, advances in orbital imaging have led to a paradigm shift, with ARDE now recognised as a mechanical disorder within the spectrum of sagging eye syndrome [4,5]. Age-related degeneration of orbital connective tissues, particularly the lateral rectus–superior rectus (LR–SR) band, results in inferior displacement of the lateral rectus pulley and reduced abducting force [4]. This mechanism explains the characteristic clinical features of ARDE and provides a rationale for surgical approaches that enhance lateral rectus function.

Management of ARDE depends on symptom severity and patient preference. Prism correction is often effective for small deviations but may be limited by optical distortion, cosmetic concerns, and reduced compatibility with multifocal lenses [2,9]. The increasing demand for spectacle independence has further reduced the acceptability of prism therapy.

Surgical intervention is therefore frequently required. Both medial rectus (MR) recession and lateral rectus (LR) resection have been shown to be effective [10,11]. However, MR recession risks inducing near diplopia, whereas LR resection strengthens divergence while preserving convergence. This makes LR resection particularly appealing in regard to ARDE, where near alignment is typically preserved.

While bilateral LR resection is effective, it may be excessive for small-angle deviations. Unilateral LR resection has emerged as a more targeted approach, with several studies demonstrating favourable outcomes [12,13,14,15]. However, existing data are limited by small sample sizes and variable surgical techniques.

In the present study, we aim to evaluate the outcomes of unilateral LR resection using standardised dosing and adjustable sutures in a single-surgeon cohort.

2. Materials and Methods

2.1. Study Design and Ethics

In this retrospective observational study, we reviewed consecutive patients who underwent unilateral lateral rectus (LR) resection for age-related distance esotropia (ARDE) between January 2019 and November 2024 at a tertiary eye centre in Brisbane, Australia. All procedures were performed by a single surgeon (SD). Ethical approval was granted by the Research and Ethics Committee of Queensland Children’s Hospital and Health Service (EX/2025/QCHQ/121377, 3 August 2025), and the study was conducted in accordance with the Declaration of Helsinki.

2.2. Eligibility Criteria

Patients were identified through clinical electronic medical records, and they were included in the study if they met all of the following criteria: (1) being afflicted with symptomatic horizontal diplopia predominantly at a distance; (2) being afflicted with comitant esotropia in primary position that is at least 25% greater at a distance than close up; (3) having full ocular ductions with no abduction deficits; (4) having no clinical features suggestive of neurological or neuromuscular disease; and (5) having a minimum postoperative follow-up period of 6 months. Exclusion criteria were prior strabismus surgery, restrictive or paralytic strabismus, thyroid eye disease or other orbital pathologies, and known neurological disease.

2.3. Preoperative Assessment

All patients underwent a comprehensive ophthalmic and orthoptic evaluation prior to surgery.

Best-corrected visual acuity (BCVA) was measured using standard Snellen charts. Refraction was performed where appropriate to ensure optimal correction. Patients with significant visual impairment (VA < 6/30) were excluded to avoid confounding from sensory strabismus.

Horizontal deviation was measured using prism and alternate cover testing in primary position nearby (33 cm) and at a distance (6 m). At least two preoperative ocular motility measurements were obtained to avoid measurement errors. Given the diagnostic overlap between ARDE and neurogenic causes of distance diplopia, all patients underwent cranial and orbital magnetic resonance imaging (MRI) to exclude intracranial or orbital mass lesions and extraocular muscle disease. Imaging features consistent with age-related changes in the LR–SR band were not considered exclusionary.

2.4. Surgical Technique

Surgery was performed under general anaesthesia. A limbal conjunctival incision was used to isolate the LR, which was secured using double-armed 6-0 polyglactin (Vicryl) sutures (Ethicon US, LLC. 2020 (Raritan, NJ, USA)). The planned resection amount was determined using a standardised dosing table of 1 mm LR resection per 4 prism dioptres (PD) of preoperative distance esotropia. The LR was resected and reattached to its original scleral point of insertion. A “bow-tie” adjustable knot configuration was used to facilitate postoperative adjustment. An adjustable-suture technique was used for all but one patient (who declined postoperative adjustment during the surgical consent acquisition process). All patients were reviewed with the prism cover test after fully waking up from general anaesthesia (usually 2–3 h after initial operation). Ocular alignment was reassessed using prism cover testing at a distance and nearby. The target postoperative outcome was orthophoria or small exophoria (<4 PD) at distance; maintenance of near orthophoria; and absence of diplopia.

Adjustment was performed if either of the following was observed: residual esotropia or exotropia corresponding to >4 PD at a distance or symptomatic diplopia in primary gaze. During adjustment, the LR was tightened or recessed using the adjustable suture mechanism until satisfactory alignment and comfortable binocular single vision were achieved.

2.5. Outcome Measures

Primary outcomes were postoperative alignment at distance and nearby and diplopia status at final follow-up (resolved, intermittent, or persistent). Secondary outcomes included requirement for same-day postoperative adjustment and duration of follow-up. Final outcomes were recorded at the most recent postoperative visit.

3. Results

3.1. Patient Characteristics

Forty-three patients with distance esotropia were identified during the study period. Four patients were excluded, as their horizontal deviation occurred after head trauma was sustained. Thus, thirty-nine patients met the inclusion criteria. The mean (±SD) age at surgery was 68.1 ± 9.7 years (range: 44–91), with a male-to-female ratio of 5:8. All patients had good preoperative BCVA (6/6–6/12), minimizing confounding from sensory strabismus. The mean preoperative esotropia was 14.3 ± 2.7 PD at a distance and 4.7 ± 3.3 PD nearby, consistent with the distance–near disparity characteristic of ARDE. All patients had minor refractive errors, and none had myopia corresponding to more than 2.0 dioptres (

Table 1. Patient characteristics and surgical outcomes following unilateral LR resection for ARDE.

Patient	Age (y)	Preop Distance (PD)	Preop Near (PD)	LR Resection (mm)	Postop Distance (PD)	Follow-Up (mo)
1	63	12	5	3	0	16
2	65	12	4	3	0	12
3	74	14	6	4	0	12
4	73	12	4	3	0	15
5	75	16	6	3	2 ET	12
6	90	16	8	4	Esophoria	12
7	67	14	10	4	0	9
8	87	20	6	5	0	9
9	68	18	6	4	Esophoria	12
10	83	18	2	4	0	26
11	73	18	8	4	0	9
12	63	16	6	4	0	18
13	56	18	10	4	0	12
14	71	10	0	3	0	24
15	67	14	0	4	0	24
16	48	16	4	5	0	24
17	69	12	0	3	0	24
18	52	16	5	4	0	24
19	89	12	4	4	0	24
20	84	12	0	3	0	24
21	69	14	6	4	0	24
22	56	12	5	4	0	24
23	44	12	0	4	Esophoria; diplopia	24
24	76	12	0	3	0	24
25	91	10	0	3	0	24
26	74	12	4	3	0	24
27	64	12	5	3	0	24
28	50	16	6	5	0	24
29	49	20	14	6	0	18
30	73	12	4	3	0	14
31	64	12	4	4	3 ET	18
32	53	16	6	5	4 ET	18
33	75	14	5	4	0	18
34	74	14	4	4	0	12
35	81	16	6	5	0	12
36	58	14	5	4	0	12
37	48	12	4	4	0	12
38	67	14	3	4	0	12
39	73	18	0	3	0	12

Note: All postoperative near deviations were 0 PD for all patients. PD = prism dioptres; ET = esotropia.

).

3.2. Surgical Dosing and Follow-Up

The mean LR resection was 3.8 ± 0.7 mm (range: 3.0–6.0 mm). The mean follow-up duration was 18 months (range: 9–26 months).

3.3. Alignment and Diplopia Outcomes

Diplopia resolved in 38/39 (97%) patients. At final follow-up, 33/39 (85%) were orthophoric at distance. All patients were orthophoric at near at the final follow-up. Same-day postoperative adjustment was performed for 5/39 (13%) patients, and the amount adjusted was based on pre-adjustment prism cover test measurements, 4/5 of which were determined to be orthophoric upon final review. Three patients had small residual distance esotropia (<5 PD): Patient 5 (2 PD esotropia, asymptomatic), Patient 31 (3 PD esotropia, intermittent diplopia when fatigued), and Patient 32 (4 PD esotropia, controlled with 4 PD base-out prism in glasses). Overall, 38/39 (97%) achieved satisfactory binocular single vision at a distance at their respective final follow-ups (Table 1).

4. Discussion

Age-related distance esotropia (ARDE) is a distinct and clinically important subtype of adult-onset strabismus. Although the magnitude of deviation typically ranges from small to moderate, the associated symptoms can be disproportionately disabling [1,7]. The restoration of comfortable binocular single vision at a distance is therefore a key therapeutic objective, often necessitating intervention beyond conservative measures.

4.1. Clinical Significance and Natural History

The natural history of ARDE is typically one of gradual progression. Patients often present with intermittent diplopia that becomes increasingly frequent over time, eventually becoming constant in some cases. Longitudinal data suggest that distance esodeviation may increase over time, while fusional divergence amplitudes remain relatively limited and do not significantly improve [7]. This progressive mismatch between motor deviation and sensory compensation likely explains the increasing symptom burden observed among affected individuals.

Importantly, ARDE must be distinguished from neurological causes of diplopia, particularly sixth-cranial-nerve palsy. The absence of abduction deficits and preservation of saccadic velocity are key differentiating features, but diagnostic uncertainty often persists, especially in early presentations. This can lead to extensive investigations, patient anxiety, and delays in definitive management. Improved recognition of ARDE as a benign, mechanical condition may help streamline diagnosis and reduce unnecessary imaging in appropriate clinical contexts.

4.2. Pathophysiology and Implications for Surgical Strategy

The evolving understanding of ARDE as part of sagging eye syndrome has important implications for management. Age-related degeneration of orbital connective tissues—particularly the lateral rectus–superior rectus (LR–SR) band—results in inferior displacement of the lateral rectus pulley and elongation of extraocular muscle paths [4,5]. This alters the effective vector of the lateral rectus muscle, reducing its abducting force and impairing divergence.

This mechanical model challenges earlier concepts of a supranuclear divergence deficit and provides a strong anatomical rationale for surgical strategies that enhance lateral rectus function. It also explains why ocular ductions remain full despite impaired divergence: the issue lies not in muscle weakness per se but in altered biomechanics.

Furthermore, sagging eye syndrome is a progressive condition. Even after successful surgical correction, ongoing connective tissue involution may result in gradual recurrence or drift over time. Long-term studies have reported recurrence rates of approximately 20%, highlighting the importance of patient counselling and long-term follow-up [13] (

Table 2. Summary of published series reporting LR resection for divergence-insufficiency-type esotropia/ARDE.

Author (Year)	Population	Sample (N, Age)	Surgery/Dosing	Follow-Up and Outcomes
Hoover and Giangiacomo (1993) [12]	Divergence/ partial VI palsy	N = 9; age not reported	Unilateral LR resection; variable dosing	Short-term follow-up; improvement in distance diplopia
Thacker et al. (2005) [13]	Divergence palsy (mixed)	N = 29 (5 unilateral); age not reported	Unilateral/bilateral LR resections; variable dosing	Mean follow-up—39 months (up to 7 years); long-term success—approximately 86%; some late recurrences
Stager et al. (2013) [15]	Divergence- insufficiency-type esotropia	N = 57; mean age: 68 years (range, 40–88 years)	Unilateral LR resection; 4–6 mm	Median follow-up—10 weeks (minimum 6 weeks); 93% diplopia resolution at last follow-up
Yadav et al. (2014) [14]	ARDE	N = 14; mean age: 79.8 years (range, 68–90 years)	Unilateral LR resection; 4.9 ± 1.3 mm	Short- to intermediate-term follow-up; 100% orthophoria at follow-up

Notes: ARDE, age-related distance esotropia; LR, lateral rectus; VI, sixth cranial nerve.

).

4.3. Comparison of Surgical Approaches

A range of surgical options have been described for ARDE, including medial rectus (MR) recession, lateral rectus (LR) resection, and combined or bilateral procedures [2,10,11].

4.3.1. Medial Rectus Recession

Medial rectus recession has been shown to be effective in correcting distance esotropia, with outcomes comparable to lateral rectus resection when augmented dosing is used [10]. However, this approach involves weakening convergence, which may be undesirable for patients with already-limited fusional reserves. Although studies have reported low rates of postoperative near diplopia, the theoretical risk remains, particularly for older patients with reduced adaptability.

Additionally, MR recession in ARDE often requires larger-than-standard surgical doses to achieve adequate correction, reflecting the altered dose–response relationship in divergence insufficiency [11]. This variability may reduce predictability and increase the risk of under-correction.

4.3.2. Lateral Rectus Resection

Lateral rectus resection offers several advantages. By strengthening divergence without compromising convergence, it preserves near alignment while directly addressing the underlying mechanical deficit. This is particularly relevant in ARDE, where near binocular function is typically intact preoperatively.

Our findings support the effectiveness of unilateral LR resection, with 97% diplopia resolution and preservation of near orthophoria in all patients. These results are consistent with previous studies. Stager et al. reported a 93% success rate [15], while Yadav et al. achieved 100% orthophoria in a smaller cohort [14]. Thacker et al. demonstrated durable long-term outcomes, although some late recurrence was observed [13].

4.3.3. Unilateral vs. Bilateral Surgery

Bilateral LR resection is effective for correcting larger deviations but may be excessive for the relatively small deviations typical of ARDE. Overcorrection of near angle of deviation is a potential concern, particularly for patients with minimal preoperative near deviation. Unilateral LR resection provides a more conservative and targeted approach, reducing surgical exposure while achieving satisfactory alignment in most cases.

The success of unilateral surgery in our cohort supports its use as a first-line surgical option for small-to-moderate deviations. However, larger deviations or cases with progression may still require bilateral intervention.

4.3.4. Alternative Techniques

Lateral rectus equatorial myopexy has been proposed as a technique with which to address pulley displacement directly by repositioning the lateral rectus muscle [16]. While conceptually appealing, this approach is technically more complex and less widely adopted. Current evidence remains limited, and further studies are needed to define its role relative to conventional muscle surgery.

4.4. Role of Adjustable Sutures

Adjustable sutures are particularly well suited to ARDE due to the small magnitude of deviations and the high sensitivity of patients to residual misalignment. In this study, 13% of patients required same-day postoperative adjustment. While the majority achieved satisfactory alignment without adjustment, this subset highlights the value of intraoperative flexibility.

Older patients typically have reduced fusional convergence and divergence amplitudes, limiting their ability to compensate for even minor residual deviations. Consequently, achieving precise alignment is critical. Adjustable sutures allow fine-tuning of ocular alignment in the early postoperative period, reducing the risk of persistent diplopia.

Our findings suggest that standardised dosing, combined with adjustable sutures, provides both predictability and flexibility. Importantly, the relatively low adjustment rate indicates that the surgical dosing strategy was an important factor in the satisfactory surgical outcome in our cohort, and LR resection without adjustment can also produce highly successful outcomes.

4.5. Clinical Implications

The results of this study have several practical implications. First, unilateral LR resection represents an effective and minimally invasive surgical option for ARDE, particularly for patients with small-to-moderate deviations. Second, the alignment outcomes are highly favourable, with preservation of near function, which is critical for patient satisfaction.

Third, the use of adjustable sutures enhances surgical precision and should be considered standard practice for this population. Finally, recognizing ARDE as a mechanical rather than neurological condition can help guide both diagnosis and management, reducing unnecessary investigations and facilitating timely intervention.

4.6. Limitations

Several limitations should be acknowledged. This study’s retrospective design introduced potential selection bias, and the absence of a control group limits direct comparison with alternative surgical approaches. The study was conducted by a single surgeon, enhancing consistency but potentially limiting generalisability.

The mean follow-up duration of 18 months, while longer than in several published series, may still be insufficient for capturing long-term recurrence. Given the progressive nature of connective tissue degeneration in sagging eye syndrome, a longer follow-up is essential to assess durability.

Additionally, we did not include standardised patient-reported outcome measures. While diplopia resolution is a clinically meaningful endpoint, validated quality-of-life instruments would provide a more comprehensive assessment of treatment benefit.

This study’s small sample size prohibits meaningful subgroup analysis of the efficacy of treatment for various angles of deviation.

4.7. Future Directions

Future research should focus on conducting prospective, multicentre studies with longer follow-ups to evaluate the durability of surgical outcomes. Comparative studies between unilateral and bilateral procedures, as well as between MR recession and LR resection, would help refine surgical decision-making.

Further investigation into the role of orbital imaging in guiding surgical planning may also be valuable, particularly for identifying patients with significant pulley displacement. Finally, incorporation of patient-reported outcome measures is essential to fully capture the functional impact of treatment.

5. Conclusions

Unilateral lateral rectus resection is a safe, effective, and targeted surgical option for age-related distance esotropia. Use of adjustable sutures facilitates early fine-tuning and is well suited to small-angle diplopic deviations, producing high rates of distance orthophoria and diplopia resolution while preserving near alignment. Prospective studies with longer follow-ups are warranted to confirm durability and refine surgical dosing.