Purpose
To investigate the success of strabismus surgery in older adults and determine the impact of age and underlying etiology on surgical outcomes.
Methods
Retrospective review of medical records of patients aged 60 years or older who underwent strabismus surgery at a tertiary eye care center. Surgical motor and sensory outcomes were analyzed.
Results
Of the 562 that met criteria, patients were mostly female (56.1%) with a mean age of 71.7 ± 6.6 years. The majority of patients reported diplopia (85.9%). The most frequent etiologies were paralytic (27.9%), adult-onset esotropia (19.0%), and thyroid eye disease (16.4%). Following initial surgery, motor and sensory surgical success rates were 65.1% and 62.9%. No significant differences in mean age were observed based on sensory success ( P = .8529), motor success ( P = .1670), or etiology ( P = .1069). Etiology was associated with motor and sensory success ( P = .0160 and P = .0001, respectively). Adult-onset basic esotropia had higher rates of motor and sensory success ( P = .0091), and convergence insufficiency exotropia and recurrent or consecutive strabismus had higher rates of sensory success ( P = .0029 and P = .0393, respectively). Among demographic and preoperative characteristics, etiology ( P = .0008) predicted sensory success, and etiology ( P = .0670) and use of adjustable sutures ( P = .0003) predicted motor success. Patients who received adjustable sutures had significantly higher odds (OR = 2.15; 95% CI, 1.42-3.25) of motor success. Motor and sensory success rates improved to 78.1% and 73.3% after reoperation in 82 patients (14.6%).
Conclusions
Etiology was found to be predictor of sensory success, while both etiology and use of adjustable sutures were predictors of motor success. Surgical success was not influenced by increasing age.
NOTE: Publication of this article is sponsored by the American Ophthalmological Society.
INTRODUCTION
S trabismus is a commonly underestimated ocular problem in adults. Studies have shown that the prevalence of strabismus increases with age up to 84 years, peaking in the eighth decade of life, and is also associated with White race and declining health status. , Based on an annual incidence rate of 54.1 cases per 100,000 people, strabismus would be expected to develop in approximately 1 in 25 adults or in 4% of the adult population. However, a random sample of Medicare Part B physician claims revealed that diagnosis of strabismus was made in only 0.68% of aged fee-for-service Medicare beneficiaries. The difference in prevalence rates between the two studies may be due to the distinct study designs, with one using population-based data and the other relying on a claims database. A limitation of claims database reviews is the underestimation of true population rates due to undercoding. This could happen if an ophthalmological examination was not included in the physician’s claims for a sample year, or if strabismus was not reported, as it is often considered a secondary issue by many clinicians.
In the United States the population age 65 and older numbered 55.7 million in 2020, an increase of 38% in 10 years, and represented 17% of the population, more than 1 in every 6 Americans. Furthermore, in 2020, persons reaching age 65 had an average life expectancy of an additional 18.5 years (19.8 years for women and 17.0 years for men). The current growth of the aging population increases the significance of the psychosocial and functional impact of strabismus among the elderly. Research indicates that strabismus affects quality of life, limits functional ability, and increases the risk of sustaining a musculoskeletal injury, fracture, or fall. Moreover, evidence shows that adult strabismus patients suffer significant social, psychological, and economic effects due to their condition. According to Kushner, many would willingly trade a portion of their life expectancy to be free of strabismus.
Surgery can effectively alleviate the burden of strabismus in the elderly, however, information regarding surgical outcomes in this age group is limited. Strabismus in adults differs from that in children, as it encompasses a diverse range of etiologies, adding to the complexity of treatment. Kushner reported that approximately 80% of adults will achieve satisfactory alignment with one surgical procedure, depending on the nature of their strabismus. Fang and associates found that following strabismus surgery, 63% of 110 patients at least 65 years old had complete resolution of their presenting chief complaint, but etiology and motor and sensory outcomes were not analyzed. We aim to investigate the strabismus surgical success rates in the older population and analyze the impact of the patient’s age and underlying etiology on the surgical outcomes. Our goal is to gather data that will enhance counseling and surgical care for elderly patients with strabismus.
METHODS
This retrospective chart review was approved by the University of Miami Institutional Review Board and adhered to the requirements of the US Health Insurance Portability and Accountability Act of 1996 and the tenets of the Declaration of Helsinki. The medical records of adults 60 years of age or older who underwent strabismus surgery at the Bascom Palmer Eye Institute between 2015 and 2022 were reviewed. The medical records were identified using CPT codes for strabismus surgery 67311, 67312, 67314, 67316, 67318, and 67335. The surgeries were performed by four different surgeons and the choice of surgical procedure was at the surgeon’s discretion.
Collected data included patient demographics (age, sex, race, ethnicity), presence of binocular diplopia, and types and magnitude of the strabismus in prism diopters (PD) at distance and near at the preoperative and last visits. The etiology of the strabismus was classified as paralytic, thyroid eye disease (TED), following nonstrabismus ocular surgery, adult-onset esotropia including age-related distance esotropia (ARDE) and basic esotropia (AOBE), exotropia comprising basic exotropia (BXT) and convergence insufficiency exotropia (CIXT), recurrent or consecutive strabismus, sensory strabismus, and other forms of strabismus. The population was divided into 3 groups: 60 to 69, 70 to 79, and 80 years of age and above.
The surgical information recorded included the type of anesthesia used, surgical procedure performed, use of adjustable suture, surgical complications, and surgical outcomes. The outcome variables were motor and sensory success. A successful motor outcome was defined as a vertical deviation of ≤5 PD and a horizontal deviation of ≤10 PD in primary gaze. Sensory outcomes were deemed successful if there was documented resolution of binocular diplopia in primary position without prism correction in patients with preoperative diplopia. Motor and sensory success were assessed after the initial surgery and after final surgery. Only patients with at least a 2-month follow-up were analyzed.
Descriptive statistics (mean, standard deviation, count, percent) were used to summarize the data overall and by etiology. Univariable comparisons were made using the independent samples t tests, the Mann–Whitney U test, or one-way ANOVA for continuous data, and Pearson’s chi-square test or Fisher’s exact test for categorical data.
Statistical analyses of the outcome variables were only performed on success after the initial surgery. Linear regressions were used to compute the dose-response as the relationship between the surgical dose in millimeters and the amount of surgical correction. Additionally, multivariable forward binary logistic regression models were conducted to identify independent associations with surgical success after initial surgery and to predict the probability of initial success for a patient using demographic and preoperative patient characteristics (age, sex, race, ethnicity, etiology, preoperative angles of deviation, and use of adjustable sutures). The criteria for variable entry were set at a P value of .05. Analyses were performed using SAS software, version 9.4 (SAS Institute), and statistical significance was determined at a P value .05.
RESULTS
A total of 679 adults aged 60 years or older that underwent strabismus surgery were identified, however, only 562 with a follow-up of at least 2 months were included in the analysis. Patients were mostly female (56.1%) with a mean age of 71.7 ± 6.6 years (range 60-94 years). The age distribution was as follows: 230 patients (40.9%) were 60 to 69 years old, 262 (46.6%) were 70 to 79 years old, and 70 (12.5%) were aged 80 years or older. The most common race was White, comprising 493 patients (88.4%), followed by Black (30, 5.4%), unknown (29, 5.2%), and Asian (3, 0.5%) Most patients were non-Hispanic (390, 69.4%), followed by Hispanic (144, 25.6%). Demographic information is summarized in Table 1 . The most common etiologies of the strabismus were paralytic (157, 27.9%), adult-onset esotropia (107, 19%), TED (92, 16.4%), prior nonstrabismus ocular surgery (66, 11.7%) and exotropia (66, 11.7%). Table 2 shows patient distribution by etiology. The last encounter ranged between 2 and 168 months.
| All Patients | Paralytic | TED | Ocular Surgeries | ARDE | AOBE | CIXT | BXT | Recurrent | Other | Sensory | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Factors | |||||||||||
| Number of patients n (%) | 562 (100) | 157 (27.9) | 92 (16.4) | 66 (11.7) | 72 (12.8) | 35 (6.2) | 41 (7.3) | 25 (4.4) | 51 (9.1) | 12 (2.1) | 11 (2.0) |
| Age (y), mean ± SD | 71.7 ± 6.6 | 70.8 ± 6.1 | 71.6 ± 6.9 | 73.1 ± 6.7 | 72.3 ± 7.1 | 71.8 ± 6.4 | 73.4 ± 7.0 | 72.4 ± 7.1 | 69.9 ± 5.6 | 72.5 ± 8.7 | 69.6 ± 3.6 |
| AGE (y) | |||||||||||
| 60-69 | 230 (40.9) | 74 (47.1) | 41 (44.6) | 19 (28.8) | 26 (36.1) | 11 (31.4) | 15 (36.6) | 9 (36.0) | 23 (45.1) | 6 (50.0) | 6 (54.6) |
| 70-79 | 262 (46.6) | 69 (44.0) | 39 (42.4) | 36 (54.6) | 35 (48.6) | 20 (57.1) | 18 (43.9) | 10 (40.0) | 26 (51.0) | 4 (33.3) | 5 (45.5) |
| 80+ | 70 (12.5) | 14 (8.9) | 12 (13.0) | 11 (16.7) | 11 (15.3) | 4 (11.4) | 8 (19.5) | 6 (24.0) | 2 (3.9) | 2 (16.7) | 0 (0.0) |
| Gender | |||||||||||
| Female | 315 (56.1) | 85 (54.1) | 57 (62.0) | 37 (56.1) | 46 (63.9) | 20 (57.1) | 16 (39.0) | 10 (40.0) | 33 (64.7) | 6 (50.0) | 5 (45.4) |
| Male | 247 (43.9) | 72 (45.9) | 35 (38.0) | 29 (43.9) | 26 (36.1) | 15 (42.9) | 25 (61.0) | 15 (60.0) | 18 (35.3) | 6 (50.0) | 6 (54.6) |
| Race | |||||||||||
| White | 493 (88.4) | 135 (87.1) | 79 (86.8) | 58 (87.9) | 68 (94.4) | 30 (85.7) | 35 (87.5) | 24 (96.0) | 48 (94.1) | 12 (100.0) | 4 (36.4) |
| Black | 30 (5.4) | 6 (3.9) | 6 (6.6) | 5 (7.6) | 0 (0.0) | 1 (2.9) | 5 (12.5) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 7 (63.6) |
| Asian | 3 (0.5) | 1 (0.7) | 1 (1.1) | 0 (0.0) | 1 (1.4) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) |
| Unknown | 29 (5.2) | 12 (7.7) | 4 (4.4) | 2 (3.0) | 3 (4.2) | 4 (11.4) | 0 (0.0) | 1 (4.0) | 3 (5.9) | 0 (0.0) | 0 (0.0) |
| American Indian | 1 (0.2) | 1 (0.7) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) |
| More than one | 2 (0.4) | 0 (0.0) | 1 (1.1) | 1 (1.5) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0.0) |
| Ethnicity | |||||||||||
| Non-Hispanic | 390 (69.4) | 107 (68.2) | 71 (77.2) | 48 (72.7) | 60 (83.3) | 29 (82.9) | 22 (53.7) | 9 (36.0) | 32 (62.8) | 5 (41.7) | 7 (63.6) |
| Hispanic | 144 (25.6) | 40 (25.5) | 16 (17.4) | 16 (24.2) | 8 (11.1) | 4 (11.4) | 18 (43.9) | 16 (64.0) | 17 (33.3) | 5 (41.7) | 4 (36.4) |
| Unknown | 28 (5.0) | 10 (6.4) | 5 (5.4) | 2 (3.0) | 4 (5.6) | 2 (5.7) | 1 (2.4) | 0 (0.0) | 2 (3.9) | 2 (16.7) | 0 (0.0) |
| Etiology | All Patients ( n = 562) | % of Total | Preoperative Diplopia (%) | Motor Success Rate (%) After Initial/Final Surgery | Sensory Success Rate a (%) After Initial/Final Surgery |
|---|---|---|---|---|---|
| Paralytic strabismus (total) | 157 | 27.9 | 95.5 | 60.9/76.9 | 56.4/68.5 |
| Unilateral CNP 4 | 69 | 12.3 | 98.6 | 72.1/80.9 | 65.7/71.6 |
| Unilateral CNP 6 (total) | 61 | 10.9 | 91.8 | 52.5/73.8 | 53.6/73.2 |
| Unilateral partial CNP 6 | 49 | 8.7 | 93.9 | 57.1/79.6 | 56.5/76.1 |
| Unilateral complete CNP 6 | 12 | 2.1 | 83.3 | 33.3/50.0 | 40.0/60.0 |
| Unilateral CNP 3 | 15 | 2.7 | 93.3 | 46.7/60.0 b | 21.4/28.6 |
| Bilateral CNP 4 | 6 | 1.1 | 100 | 50/100 | 33.3/66.7 |
| Multiple CNP | 4 | 0.7 | 100 | 50.0/75.0 | 50.0/75.0 |
| Bilateral CNP 6 | 2 | 0.4 | 100 | 100 c | 100 c |
| Adult-onset esotropia (total) | 107 | 19.0 | 97.2 | 76.6/89.7 | 73.1/81.7 |
| Age-related distance esotropia | 72 | 12.8 | 100 | 73.6/88.9 | 68.1/77.8 |
| Adult-onset basic esotropia | 35 | 6.2 | 91.4 | 82.9/91.4 | 84.4/90.6 |
| Thyroid eye disease | 92 | 16.4 | 98.9 | 59.8/78.3 | 58.2/71.4 |
| Prior ocular surgery | 66 | 11.7 | 81.4 | 56.1/69.7 | 51.9/61.1 |
| Retina | 29 | 5.2 | 75.9 | 55.0/79.3 | 50.0/68.1 |
| Cataract | 15 | 2.7 | 93.3 | 80 c | 64.3 |
| Glaucoma | 13 | 2.3 | 69.2 | 31.0/46.2 | 33.3/44.4 |
| Orbital | 8 | 1.4 | 100 | 50 c | 50 c |
| Cornea | 1 | 0.2 | 100 | 100 c | 100 c |
| Exotropia (total) | 66 | 11.7 | 69.7 | 71.2/77.3 | 78.3/84.8 |
| Convergence insufficiency exotropia | 41 | 7.3 | 68.3 | 70.7 | 89.3 |
| Basic exotropia | 25 | 4.4 | 72.0 | 72.0/88.0 | 61.1/77.8 |
| Recurrent/consecutive strabismus | 51 | 9.1 | 52.9 | 70.6/74.5 | 81.5/88.9 |
| Other types of strabismus | 12 | 2.1 | 75.0 | 33.3/50 | 22.2/44.0 |
| Sensory strabismus | 11 | 2.0 | 18.2 | 81.8 | 100 c |
a Sensory success rates only include patients with preoperative diplopia.
b Following horizontal, vertical, and combined procedures.
Motor success was achieved in 365 patients (65.1%) after a single surgery and in an additional 73 patients (13%) following further surgery, resulting in a final motor success rate of 78.1%. Preoperatively, diplopia was present in 483 patients (85.9%), primarily in those with TED (99%), and less frequently in patients with sensory strabismus ( Table 2 ). Diplopia resolved in 303 patients (62.7%) after the initial surgery, with an additional 51 patients (10.6%) achieving resolution after further surgery, resulting in a final sensory success rate of 73.3%. Among patients with persistent diplopia, 52 achieved fusion with prism glasses, 45 experienced diplopia intermittently, and only 32 had constant diplopia. The final surgical motor and sensory success rates are displayed by age group in Figure 1 and by etiology in Figure 2 .
Complications occurred in 0.7% of patients, with no cases resulting in visual loss. Two patients experienced a “pulled-in-two” syndrome intraoperatively due to tight medial rectus muscles; only one muscle was recovered, with both patients having residual esotropia. One patient experienced a postoperative slipped medial rectus muscle 1 day after surgery that was successfully recovered, and another patient had a scleral perforation during a Harada-Ito procedure, which was treated with laser to the retina. Reoperations were performed on 82 patients (14.6%).
There were no statistically significant differences in mean age by sensory ( P = .8529) or motor success ( P = .1670) after the initial surgery, or by etiology ( P = .1069). Adjustable sutures were used in 400 patients (71.2%). There was a statistically significant association between motor success and use of adjustable sutures. After a single surgery, a significantly greater proportion of patients with adjustable sutures had overall motor success compared to those who did not have adjustable sutures (70.3% vs 53.9%, P = .0002). However, there was not a statistically significant association between sensory success and use of adjustable sutures (65.6% vs 57.6%, P = .1093). The type of anesthesia used was a retrobulbar or peribulbar block in 382 patients (68.0%) and general anesthesia in 180 patients (32.0%). There were no statistically significant associations between type of anesthesia and rates of motor ( P = .1079) or sensory success ( P = .0946).
The etiology of the strabismus demonstrated significant associations with both motor and sensory success rates ( P = .0160 and P = .0001, respectively). AOBE had significantly higher rates of motor and sensory success ( P = .0226 and P = .0091, respectively), and CIXT and recurrent or consecutive strabismus had significantly higher rates of sensory success ( P = .0029 and .0393, respectively). Conversely, the etiology group of other forms of strabismus had significantly lower rates of motor and sensory success ( P = .0294 and P = .0152, respectively).
Among demographic and preoperative characteristics, the forward logistic regression models identified etiology ( P = .0008) as a predictor of sensory success after a single surgery and use of adjustable sutures and etiology ( P = .0670) as predictors of motor success after a single surgery. The overall regression models for sensory success and motor success were statistically significant ( P < .0001 and P = .0003, respectively). Paralytic strabismus (OR = 0.26 [95% CI: 0.1-0.72]), TED (OR = 0.25 [95% CI: 0.09-0.72]), strabismus after prior nonstrabismus ocular surgery (OR = 0.21 [95% CI: 0.07-0.62]), and “other strabismus” (OR = 0.05 [95% CI: 0.01-0.33]) had significantly lower odds of sensory success compared to AOBE. Patients who received adjustable sutures had significantly greater odds of having motor success than those who did not when holding etiology constant (OR = 2.15 [95% CL: 1.42-3.25]).
paralytic strabismus
We identified 157 patients (85, 54.1% female) with paralytic strabismus with an average age of 70.8 ± 6.1 years. The distribution by age in years was: 74 (47.1%) 60 to 69, 69 (44.0%) 70 to 79, and 14 (8.9%) 80 years of age and above. Most patients were White (135, 87.1%) and non-Hispanic (107, 68.2). The most common type of cranial nerve palsy (CNP) was CNP 4 in 75 (47.8%), CNP 6 in 63 (40.1%), and CNP 3 in 15 (9.6%) as demonstrated in Figure 3 . Diplopia was present in 150 patients (95.5%). Overall, the motor and sensory success rates were 60.9% and 56.4% respectively after initial surgery and improved to 76.9% and 68.5% after reoperation. Surgical results after final surgery are summarized by type of palsy in Figure 4 .
