Abstract
Background:
Visual inputs are critical for locomotor navigation and sensorimotor integration in the elderly; however, the mechanism needs to be explored intensively. The present study assessed the gait pattern after cataract surgery to investigate the effects of visual restoration on locomotion.
Methods:
The prospective study recruited 32 patients (70.1 ± 5.2 years) with bilateral age-related cataracts in the Department of Ophthalmology at Peking University Third Hospital from October 2016 to December 2019. The temporal-spatial gait parameters and kinematic parameters were measured by the Footscan system and inertial measurement units. Paired t-test was employed to compare data normally distributed and Wilcoxon rank-sum test for non-normally distributed.
Results:
After visual restoration, the walking speed increased by 9.3% (1.19 ± 0.40 m/s vs. 1.09 ± 0.34 m/s, P=0.008) and exhibited an efficient gait pattern with significant decrease in gait cycle (1.02 ± 0.08 s vs. 1.04 ± 0.07 s, P=0.012), stance time (0.66 ± 0.06 s vs. 0.68 ± 0.06 s, P=0.045), and single support time (0.36 ± 0.03 s vs. 0.37 ± 0.02 s, P=0.011). High amplitude of joint motion was detected in the sagittal plane in the left hip (37.6° ± 5.3° vs. 35.5° ± 6.2°, P=0.014), left thigh (38.0° ± 5.2° vs. 36.4° ± 5.8°, P=0.026), left shank (71.9° ± 5.7° vs. 70.1° ± 5.6°, P=0.031), and right knee (59.1° ± 4.8° vs. 56.4° ± 4.8°, P=0.001). The motor symmetry of thigh improved from 8.35 ± 5.30% to 6.30 ± 4.73% (P=0.042).
Conclusions:
The accelerated gait in response to visual restoration is characterized by decreased stance time and increased range of joint motion. Training programs for improving muscle strength of lower extremities might be helpful to facilitate the adaptation to these changes in gait.
Keywords: Biomechanical phenomena, Cataract, Gait, Rehabilitation, Visual perception
Introduction
Visual information provides real-time navigation for locomotion, which significantly affects motor ability.[1,2] The age-related decline in multisensory integration prompts a significant reliance on visual information in the elderly and makes them more sensitive to the impact of visual restriction on mobility.[3] Previous studies have manifested that visual impairments would adversely affect the gait performances, resulting in a severely cautious gait pattern in the elderly.[4–6] Nonetheless, the mechanisms of sensorimotor integration underlying the significant effects of visual inputs on motor ability in the elderly need to be investigated.
The satisfactory outcome of cataract surgery resulted in optimal visual restoration in patients with age-related cataracts, thus providing an ideal model to observe the effect of visual reconstruction on gait in the elderly. Moreover, for the significant impact of vision on mobility and its role in independent viability, the changes in locomotion associated with visual improvement serve as critical indicators for the effect of cataract surgery on the quality of life. Reportedly, the walking speed measured by a stopwatch increased significantly after cataract surgery.[7–9] Studies on stability after cataract surgery also revealed an improvement in postural stability as assessed by balance performance[10] or an interaction balance testing system.[11] These previous studies confirmed the positive effect of visual restoration on mobility in patients with age-related cataracts. However, an urgent visual reconstruction makes it difficult for the elderly to make timely adjustments that match the improvement in walking speed in the short term after cataract surgery. Intensive studies on changes in gait pattern in response to visual restoration would serve as a basis for rehabilitation strategies to facilitate the adjustments.
Therefore, the present study aimed to investigate the temporal and spatial gait parameters and kinematics during level walking in patients with age-related cataracts before and 4 weeks after cataract surgery. In accordance with previous studies,[7–9] we hypothesized an increased walking speed after cataract surgery, and the acceleration might be manifested as a decrease in temporal parameters, indicating an elevated efficiency of locomotion. We also hypothesized that the kinematic manifestation of the improved walking efficiency would be the increased range of motion (ROM) in the lower limbs. Strikingly, the supporting and dynamic functions of the bilateral extremities are not identical.[12] Therefore, it could be speculated that the postoperative influence on joint motion might exhibit the feature of lateralization.
Methods
Ethical approval
This study was conducted in accordance with the Declaration of Helsinki and was approved by the Institutional Review Board of Peking University Third Hospital (No. IRB00006761–2016037). Informed written consent was obtained from all patients before their enrollment in this study.
Participants
This prospective cohort study included consecutive patients referred for cataract surgery to the Department of Ophthalmology at Peking University Third Hospital between October 2016 and December 2019. The inclusion criteria were as follows: diagnosis of binocular age-related cataracts, classified as cortical or nuclear cataracts; eligibility for consecutive cataract surgery; scheduled for implantation of monofocal intraocular lenses; age between 60 years and 80 years; uncorrected distant visual acuity equal to corrected distant visual acuity at the preoperative phase, not worse than 20/200 by Snellen chart; and right-handed. The exclusion criteria were as follows: previous ocular surgery or laser treatment; history of ametropia; the interval between the surgery of the first eye and the contralateral eye >1 week; a postoperative visual acuity worse than 20/25 on the Snellen chart 4 weeks after cataract surgery; need of refractive correction postoperatively; intraoperative or postoperative complications; detection of macular disease; neuro-ophthalmic disease; uncontrolled hypertension; history of diabetes; cardio-cerebrovascular disease; vestibular or cerebellar dysfunction; mental disease; neurological motor disorders (including Parkinson's disease); detection of symptoms of locomotor deficits; using psychotropic drugs; and musculoskeletal system injuries 6 months before the study. The screening of medical diseases was achieved by evaluating the medical history based on the preoperative evaluation form, previous medical records, common medication records, and routine preoperative tests (including electrocardiogram, chest radiograph and venous blood test for fasting blood glucose). A physiotherapist assessed the amplitude of limb movement and muscle strength by physical examination.
Surgical procedures
All patients underwent consecutive cataract surgery in the bilateral eyes on separate days. The surgery for the contralateral eye was completed within 1 week after the first eye surgery. The cataract surgery was standard minimal-incision phacoemulsification performed with topical anesthesia. All cataract surgeries were successfully completed by experienced surgeons from the same group. No complication was found during neither intraoperative nor postoperative follow-up.
Ophthalmological examinations
Refraction, visual acuity (expressed as the logarithm of the minimum angle of resolution), slit-lamp biomicroscopy, fundoscopy, and non-contact tonometry were performed during every visit.
Gait assessment
The gait parameters of each participant were examined within the week before the first eye surgery and 4 weeks after the contralateral eye surgery when the refraction and visual restoration achieved a stable status [Figure 1].[13,14] The gait was assessed in the professional laboratory for sports biomechanics in the Department of Sports Medicine at Peking University Third Hospital. The laboratory was illuminated by fluorescent lamps with 240–250 lux at the foot ground. In each walking test, the participants started walking 4 m from the start of the instrumented mat and finished walking 2 m past the mat. The practice trials were conducted before the formal test in both the pre- and post-operative phases after the participants were instructed. Data from five successful walking trials were collected, and the average derived from the median of three walks was analyzed.
Figure 1.
Flowchart of the experimental protocol on gait parameters of age-related cataract patients.
Temporal-spatial gait parameters were collected using a 2-m Footscan® plate system (2.0 m × 0.4 m, 16,384 sensors, 126 Hz sample frequency; RSscan International, Belgium). Temporal parameters [Figure 2A], including the gait cycle, single support time, double support time, stance time, and velocity (defined as the stride length divided by the gait cycle) were calculated. The stride length and walking base were measured to describe the spatial characteristics of gait [Figure 2B]. Double support time, double support duration (defined as double support time as a percentage of the gait cycle), walking base, and the coefficient of variation for the walking base were analyzed as parameters for stability.
Figure 2.
Temporal-spatial parameters are used to evaluate the gait performance of age-related cataract patients. (A) Temporal parameters: gait cycle, the time interval between two successive occurrences of initial contact of the same foot; single support time, the period between the opposite toe-off and the opposite initial contact; double support time, the period between the initial contact and the opposite toe off; stance time, the period between the initial foot contact and the toe off of the same foot. (B) Spatial parameters: stride length, the distance between two successive placements of the same foot; walking base, the side-to-side distance between the lines of the two feet.
The kinematics of the lower extremities were collected at an accuracy of 0.11° by using the inertial measurement units (IMUs) system (GaitSmart™, Hertfordshire, UK).[15,16] In the sagittal plane, the typical angles that the individuals flexed the hips, flexed the knees, swung the pelvis, swung the thighs, and moved the lower limbs, were calculated as the ROM in the hip, knee, pelvis, thigh, and shank, respectively. In the coronal plane, how the individuals swung their legs in or out when walking was calculated as the coronal movement divided by the sagittal movement and expressed as a percentage for the left and right side of the pelvis medial-lateral, thigh medial-lateral, and shank medial-lateral. The symmetry scores for the ROM between the left and right legs were calculated as follows:
Symmetry score = {2(Rleft – Rright)/(Rleft + Rright)} × 100%
where Rleft and Rright are the magnitudes of a given ROM of the left and right legs.
Statistical analysis
Statistical analyses were performed using SPSS V22.0 software (SPSS Inc., Chicago, IL, USA). Descriptive statistics for normally distributed continuous variables were reported as the mean ± standard deviation, and non-normally distributed variables are described as the median and range. Continuous variables were compared using a two-tailed paired t-test when the data were normally distributed; the Wilcoxon rank-sum test was used for non-normally distributed data. Type I error rate <0.05 indicated a statistical significance. A power analysis based on the initial data of 10 patients revealed that 24 participants would be needed to achieve the intended walking speed difference of 0.1 m/s between before and after surgery with 80% statistical power and an α level of 0.05. Also, a 50% drop-out rate was calculated, and hence, 36 participants were recruited. One participant was excluded due to the need for refractive correction postoperatively. Three subjects were excluded for missed kinematical records.
Results
Demographic characteristics of the participants
A total of 32 patients (27 females and 5 males; age: 70.1 ± 5.2 years; height: 157.2 ± 7.3 cm; weight: 61.6 ± 11.4 kg; body mass index: 24.9 ± 3.9 kg/m2) completed the pre- and post-operative follow-up [Table 1]. The visual acuity for the right (0.49 ± 0.26) and left eye (0.46 ± 0.22) significantly improved to the value of 0.10 (0.00, 0.10) (Z=−4.878, P < 0.001 and Z=−4.801, P < 0.001, Wilcoxon rank-sum test) at the postoperative phase.
Table 1.
Demographics of the participants undergoing cataract surgery.
| Preoperative visual acuity (LogMAR) | Postoperative visual acuity (LogMAR) | |||||||
| Case number | Sex | Age (years) | Body mass index (kg/m2) | OD | OS | OD | OS | Type of intraocular lens |
| 1 | Female | 78 | 24.8 | 0.3 | 0.6 | 0 | 0 | HQ201HEP |
| 2 | Female | 73 | 21.9 | 0.9 | 0.6 | 0 | 0.1 | Zeiss smart36A |
| 3 | Female | 75 | 25.6 | 0.3 | 0.1 | 0.1 | 0.1 | Zeiss smart36A |
| 4 | Female | 65 | 22.0 | 0.9 | 0.1 | 0.1 | 0.1 | Matrix 404 |
| 5 | Female | 73 | 29.4 | 0.7 | 0.7 | 0.1 | 0.1 | Zeiss mart36A |
| 6 | Male | 64 | 30.7 | 1.0 | 0.5 | 0 | 0 | Matrix400 |
| 7 | Female | 70 | 21.9 | 1.0 | 0.6 | 0.1 | 0.1 | AMO ZA 9003 |
| 8 | Male | 66 | 21.3 | 0.7 | 0.1 | 0 | 0 | Zeiss smart36A |
| 9 | Female | 57 | 31.2 | 0.4 | 0.5 | 0 | 0.1 | AMO ZA 9003 |
| 10 | Female | 73 | 23.3 | 1.0 | 0.9 | 0.1 | 0.1 | Matrix 404 |
| 11 | Female | 67 | 19.0 | 0.7 | 0.5 | 0.1 | 0.1 | AMO ZA 9003 |
| 12 | Female | 65 | 29.0 | 0.8 | 1.0 | 0.1 | 0 | Hoya pc-60R |
| 13 | Male | 76 | 24.5 | 0.4 | 0.5 | 0.1 | 0.1 | Matrix400 |
| 14 | Female | 75 | 24.6 | 0.1 | 0.2 | 0.1 | 0.1 | Zeiss smart36A |
| 15 | Female | 78 | 13.2 | 0.3 | 0.7 | 0.1 | 0.1 | Matrix 404 |
| 16 | Female | 72 | 25.2 | 0.4 | 0.5 | 0.1 | 0.1 | Matrix 404 |
| 17 | Female | 78 | 25.2 | 0.3 | 0.5 | 0.1 | 0.1 | AMO ZA 9003 |
| 18 | Male | 76 | 22.9 | 0.3 | 0.5 | 0.1 | 0.1 | Matrix 404 |
| 19 | Female | 70 | 28.6 | 0.3 | 0.2 | 0.1 | 0 | AMO ZA 9003 |
| 20 | Female | 67 | 32.0 | 0.4 | 0.4 | 0.1 | 0.1 | AMO ZA 9003 |
| 21 | Female | 72 | 22.4 | 0.3 | 0.4 | 0.1 | 0.1 | AMO ZA 9003 |
| 22 | Female | 68 | 28.0 | 0.5 | 0.3 | 0.1 | 0.1 | Rayner 970 |
| 23 | Female | 69 | 23.4 | 0.5 | 0.5 | 0 | 0 | Rayner 970 |
| 24 | Female | 74 | 22.9 | 0.4 | 0.5 | 0.1 | 0 | AMO ZA 9003 |
| 25 | Female | 68 | 23.4 | 0.3 | 0.3 | 0 | 0.1 | AMO ZA 9003 |
| 26 | Female | 72 | 26.9 | 0.5 | 0.5 | 0 | 0 | AMO ZA 9003 |
| 27 | Female | 67 | 27.7 | 0.2 | 0.2 | 0 | 0 | Rayner 970 |
| 28 | Female | 72 | 22.9 | 0.2 | 0.6 | 0 | 0.1 | Zeiss smart36A |
| 29 | Male | 62 | 28.9 | 0.6 | 0.2 | 0.1 | 0.1 | Rayner 970 |
| 30 | Female | 65 | 20.4 | 0.2 | 0.3 | 0.1 | 0.1 | Rayner 970 |
| 31 | Female | 74 | 27.3 | 0.5 | 0.7 | 0.1 | 0.1 | Rayner 970 |
| 32 | Female | 62 | 25.4 | 0.3 | 0.5 | 0 | 0.1 | Rayner 970 |
OD: the right eye; OS: the left eye; LogMAR: Logarithm of the minimum angle of resolution.
Temporal-spatial gait parameters: Improved walking speed after the visual reconstruction
An accelerated gait in the postoperative phase is manifested by decreased temporal parameters. The walking speed was 1.09 ± 0.34 m/s in the preoperative phase, which significantly increased to 1.19 ± 0.40 m/s in the postoperative phase (t=−2.814, P=0.008, paired t-test) [Table 2]. The increased speed was characterized by a decrease in the gait cycle (1.02 ± 0.08 s vs. 1.04 ± 0.07 s, t=2.661, P=0.012, paired t-test). The change in gait cycle was reflected as a decreased stance time (0.66 ± 0.06 s vs. 0.68 ± 0.06 s, t=2.087, P=0.045, paired t-test), especially the single support time (0.36 ± 0.03 s vs. 0.37 ± 0.02 s, t=2.722, P=0.011, paired t-test). The stride length was similar between the preoperative and postoperative phases (t=−0.553, P=0.584, paired t-test); also, no significant difference was detected in the comparison of double support time (t=1.191, P=0.243, paired t-test), double support time % (t=0.655, P=0.518, paired t-test), walking base (t=−0.330, P=0.743, paired t-test), or coefficient of variation for walking base (t=−0.565, P=0.576, paired t-test). The data of the temporal-spatial parameters are provided in Supplementary Tables 1 and 2.
Table 2.
Temporal-spatial gait parameters and symmetry score of kinematics before and after cataract surgery.
| Parameters | Preoperative assessment (n = 32) | Postoperative assessment (n = 32) | t value | P value |
| Temporal-spatial gait parameters | ||||
| Gait cycle (s) | 1.04 ± 0.07 | 1.02 ± 0.08 | 2.661 | 0.012 |
| Stance time (s) | 0.68 ± 0.06 | 0.66 ± 0.06 | 2.087 | 0.045 |
| Double support time (s) | 0.26 ± 0.08 | 0.25 ± 0.08 | 1.191 | 0.243 |
| Double support duration (% gait cycle) | 24.74 ± 7.22 | 24.00 ± 7.21 | 0.655 | 0.518 |
| Single support time (s) | 0.37 ± 0.02 | 0.36 ± 0.03 | 2.722 | 0.011 |
| Stride length (m) | 1.09 ± 0.17 | 1.11 ± 0.16 | −0.553 | 0.584 |
| Walking base (m) | 0.09 ± 0.04 | 0.09 ± 0.04 | −0.330 | 0.743 |
| CV∗ for walking base | 31.33 ± 21.29 | 29.47 ± 22.80 | −0.565 | 0.576 |
| Walking speed (m/s) | 1.09 ± 0.34 | 1.19 ± 0.40 | −2.814 | 0.008 |
| Symmetry scores (%) | ||||
| Hip symmetry | 11.33 ± 7.99 | 8.80 ± 6.96 | 1.696 | 0.100 |
| Knee symmetry | 5.66 ± 4.18 | 4.09 ± 2.74 | 1.837 | 0.076 |
| Pelvis symmetry | 29.51 ± 20.44 | 28.51 ± 17.48 | 0.309 | 0.759 |
| Thigh symmetry | 8.35 ± 5.30 | 6.30 ± 4.73 | 2.117 | 0.042 |
| Shank symmetry | 2.83 ± 1.90 | 2.93 ± 1.82 | −0.219 | 0.828 |
The data are presented as mean ± SD.
CV was calculated as the ratio of the SD of the mean multiplied by 100.
CV: Coefficient of variation; SD: Standard deviation.
Kinematic variables: Greater ROMs and enhanced symmetry of the lower extremities
In response to visual rehabilitation, the kinematic improvement in gait was characterized by an increase in the amplitude of motion of the lower extremities, especially the left side in the sagittal plane [Table 3]. After visual reconstruction, the right knee ROM (59.1° ± 4.8° vs. 56.4° ± 4.8°, t=−3.665, P=0.001, paired t-test), left hip ROM (37.6° ± 5.3° vs. 35.5° ± 6.2°, t=−2.601, P=0.014, paired t-test), left thigh ROM (38.0° ± 5.2° vs. 36.4° ± 5.8°, t=−2.330, P=0.026, paired t-test), and left shank ROM (71.9° ± 5.7° vs. 70.1° ± 5.6°, t=−2.253, P=0.031, paired t-test) were significantly greater than those in the preoperative phase. The ROMs data in the sagittal plane are summarized in Supplementary Tables 3 and 4. No significant differences were detected in the comparison of the coronal kinematic values. The data of the kinematic parameters in the coronal plane are provided in Supplementary Tables 5 and 6.
Table 3.
Kinematics during walking before and after cataract surgery.
| Preoperative assessment (n = 32) | Postoperative assessment (n = 32) | P value (t value) | ||||
| Kinematics | Left | Right | Left | Right | Left | Right |
| Sagittal kinematics (°) | ||||||
| Hip sagittal ROM | 35.5 ± 6.2 | 34.7 ± 6.4 | 37.6 ± 5.3 | 36.2 ± 5.5 | 0.014 (−2.601) | 0.109 (−1.648) |
| Knee sagittal ROM | 58.6 ± 5.7 | 56.4 ± 4.8 | 59.8 ± 4.9 | 59.1 ± 4.8 | 0.163 (−1.430) | 0.001 (−3.665) |
| Pelvis sagittal ROM | 4.7 ± 1.3 | 5.2 ± 1.8 | 4.6 ± 1.1 | 5.2 ± 1.4 | 0.627 (0.491) | 0.720 (0.362) |
| Thigh sagittal ROM | 36.4 ± 5.8 | 36.4 ± 5.5 | 38.0 ± 5.2 | 37.7 ± 4.6 | 0.026 (−2.330) | 0.124 (−1.581) |
| Shank sagittal ROM | 70.1 ± 5.6 | 69.7 ± 5.5 | 71.9 ± 5.7 | 71.2 ± 5.6 | 0.031 (−2.253) | 0.063 (−1.931) |
| Stance flexion | 14.1 ± 4.0 | 12.7 ± 4.0 | 14.9 ± 6.9 | 13.6 ± 4.5 | 0.546 (−0.611) | 0.099 (−1.703) |
| Coronal kinematics (%) | ||||||
| Pelvis coronal ROM | 4.5 ± 1.2 | 4.2 ± 1.6 | 4.4 ± 1.6 | 4.1 ± 1.2 | 0.800 (0.256) | 0.809 (0.244) |
| Thigh coronal ROM | 33.7 ± 10.5 | 30.5 ± 10.6 | 31.8 ± 14.8 | 31.8 ± 10.7 | 0.514 (0.660) | 0.599 (−0.531) |
| Shank coronal ROM | 18.0 ± 6.8 | 17.4 ± 7.4 | 18.2 ± 6.3 | 18.8 ± 7.7 | 0.939 (−0.078) | 0.451 (−0.764) |
The data are presented as mean ± SD. ROM: Range of motion; SD: Standard deviation.
The analysis of movement symmetry indicated an improved gait performance [Table 2]. The symmetry of the thigh improved significantly after visual reconstruction (8.35 ± 5.30% vs. 6.30 ± 4.73%, t=2.117, P=0.042, paired t-test), but no significant differences were detected in the symmetry of the hip, knee, pelvis, and shank between the pre- and post-operative phases. The data of the kinematic parameters of symmetry are provided in Supplementary Tables 7 and 8.
Discussion
Visual impairment is significantly associated with a decline in mobility and falls in the elderly.[17,18] The optimal visual quality after cataract surgery provides a valuable opportunity to assess the effects of visual restoration on the motor ability in the elderly. Herein, we conducted an interdisciplinary study to investigate the temporal-spatial gait parameters and kinematics of lower extremities during level walking in patients with age-related cataracts before and after cataract surgery. The results manifested that the essence of the accelerated gait was decreased single support time and a significant increase in ROMs of the lower extremities, especially at the supporting side, which improved the movement symmetry of the thigh. The visual function improved significantly in a short time after cataract surgery, making it difficult for the elderly to make timely adjustments that match the increase in walking speed. To facilitate these adjustments, it might be essential to focus on the training for muscle strength related to postural support and joint motion. Moreover, the potential laterality of changes in kinematic parameters suggested a feature of lateralization in the pathways of sensorimotor integration.
The increment in walking speed in the current study was consistent with that of previous studies, which reported an increase in the postoperative walking speed of 0.1 m/s (from 0.81–0.91 m/s to 0.91–1.04 m/s).[7–9] The walking speed is often analyzed as an index to assess mobility, and previous studies reported it as the best physical performance measure for predicting the onset of functional dependence in the elderly.[19,20] A meta-analysis also suggested that gait speed was associated with survival in the elderly with significant increments per 0.1 m/s.[21] Together with these findings, the increased walking speed observed in this study might be an indicator of the improved mobility-related quality of life after cataract surgery.
The present results supported our hypothesis that accelerated walking after cataract surgery is associated with decreased gait cycle, especially the single support time during stance. The single support time could be noted as an index that indicates the motor efficiency of the lower extremity in the swing process of walking. Therefore, our results suggested that efficient flexion and extension movements in the lower extremities are the main characteristics of the postoperative gait pattern. The stride length and parameters of stability (walking base, variability of walking base, and double support time) did not change significantly. The effect of visual impairment on the motor function of the elderly is a long-term process. However, the visual improvement and the corresponding increase in walking speed occurred in a short time after cataract surgery. The muscle strength and motor control by the central nervous system might not have made in-time adjustments to adapt to the walking speed changes, manifested as the compatible parameters of walking stability between preoperative and postoperative phases. Since the extensor muscle groups of the lower limbs play an important role in bearing loads during the support period, it easily occurs disuse atrophy due to the compensatory decrease in the amplitude of lower limb movement, in the state of preoperative visual impairment. Hence, to improve motor stability, it might be necessary to enhance the strength of the extensor muscle group of the lower limbs.
In accordance with the accelerated gait, the ROMs of lower limbs during level walking increased after the cataract surgery. One study has addressed the normal range of ROM measured by IMU in active older adults[22] and reported the ROM of the knee, thigh, and shank in the 60–69-year-old and 70–79-year-old age groups as follows: 62.9° ± 3.1°, 40.9° ± 6.4°, 75.1° ± 6.3° and 61.2° ± 5.7°, 41.7° ± 4.7°, 75.5° ± 6.8°. These values were higher than in the preoperative and postoperative data in our study. The long-term limitation of visual impairment and decreased participation in physical activity might explain the lower ROMs values in the current study. The long-term effect of visual restoration on participation in physical activity, as well as the correlation between changes in the walking pattern and participation in physical activity, should be analyzed in subsequent studies. Another study of subjects aged 75.6 ± 6.7 years[23] reported that the ROMs in the knee and hip (58.7° ± 5.0° and 35.8° ± 5.4° respectively), were higher than our preoperative data and lower than the postoperative data. These differences could be attributed to the positive effects of visual restoration on motor ability and the lower age of participants in the current study. Moreover, the increase in sagittal ROMs would consequently improve the foot-ground clearance for the swing phase,[24,25] which has been confirmed as a protective factor against falling in previous studies.[26,27] Together, these findings suggested that the postoperative increase of ROMs might be the kinematic basis for the decreased falling risk after cataract surgery.[28]
The current results also revealed that the postoperative influence on ROMs exhibited lateralization. A previous review on limb lateralization demonstrated that the non-dominant system could control the limb position and stabilization, while the dominant system was responsible for the initiation and execution of movement.[12] After visual rehabilitation, the increased movement amplitudes in the supporting related limb (the thigh, hip, and shank)[29] were mainly manifested on the non-dominant side, and the increase in the motivated limb (the knee)[29] was mainly manifested on the dominant side. The laterality of sensorimotor integration in the process of motor navigation[30] might explain the differences in bilateral kinematic changes.
In the present study, the symmetry of thigh movement during walking improved after cataract surgery. The thigh is the most proximal element in the kinematic chain of the lower extremities and serves as a connection with the axial skeleton.[31] The symmetry of thigh motion is crucial in maintaining the coordination of the lower extremities, which serves as an indication of improved gait performance after visual rehabilitation.
Nevertheless, the present study has several limitations. As the main parts of gait characteristics, the plantar pressure and muscle strength should be analyzed in future studies. A cohort study with long-term follow-up should be designed to explore the correlation between changes in gait parameters and falling risk. Moreover, the present study was mainly about the short-term changes in gait performance after cataract surgery. The long-term changes in mobility need to be assessed in a further study with a prolonged period of observation. A subsequent large-scale study should also be conducted to stratify the research data based on the magnitude of postoperative improvement in visual acuity for further discussion on the effect of visual restoration on gait. The healthy status of the nervous system was a critical factor affecting the gait pattern, hence, we set inclusion and exclusion criteria with respect to the health condition and employed a self-controlled study design. However, neuroimaging measurements, such as magnetic resonance imaging, should be included in future long-term studies to correct the changes in gait performance related to neurological disease. The low compliance to the gait test resulted in a small sample size, which limited the generalization of the current study. In the future study, portable equipment might facilitate the gait test and improve the compliance of patients.
In summary, the gait pattern associated with visual restoration after cataract surgery was characterized by decreased single support time, increased movement amplitude of the lower extremities on the supporting side, and improved gait symmetry, suggesting elevated motor efficiency during walking. Programs, such as training for muscle strength in the lower extremities, could have the potential to improve walking stability and help the elderly adapt to the changes in gait accompanied by visual reconstruction. Further study should be designed to evaluate the effect of muscle strength training on gait stability after visual restoration. The protective effect of visual restoration on mobility might be related to the positive effects of improved visual input on sensorimotor integration; during this process, a feature of lateralization could be detected. Therefore, the changes in cerebral activities during level walking in response to visual reconstruction need to be investigated to explore the mechanism of sensorimotor integration underlying the changes in gait patterns.
Funding
This work was supported by the National Natural Science Foundation of China (No. 81600760).
Conflicts of interest
None.
Supplementary Material
Footnotes
How to cite this article: Ao M, Shi H, Li X, Huang H, Ao Y, Wang W. Effects of visual restoration on gait performance and kinematics of lower extremities in patients with age-related cataract. Chin Med J 2023;136:596–603. doi: 10.1097/CM9.0000000000002509
Supplemental digital content is available for this article.
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