The impact of cataract surgery on vision-related quality of life for cataract patients in China: a prospective study

Background: Cataract is one of the most common blinding eye diseases, and patients' psychological, life and social activities will be significantly affected. Thus, the aim of this study is to to assess the impact of cataract surgery on vision-related quality of life (VRQOL) in China’s poor areaTibet. Methods: This study was a prospective cohort study. Subjects were invited to complete a validated questionnaire before and three months after cataract surgery. The 25-item National Eye Institute Visual Functioning Questionnaire (NEI VFQ-25) was used to assess the Vision-related quality of life. Generalized linear estimating equation (GEE) analysis and descriptive analyses were performed to record change of VRQOL before and after surgery. Results: One hundred and twenty-two patients were included. Among the One hundred and twenty-two patients, one hundred and seventeen (94.26%) completed the follow-up assessment after surgery. The total VRQOL was significantly improved after cataract surgery (p <0.001). the item of stereopsis and Binocular contrast sensitivity were also related to changes in VRQOL. Conclusions: The majority of patients had significantly improved VRQOL after cataract surgery in Chinese population.

.However, most of the studies were conducted in developed countries, where visual impairment was minor before cataract surgery and patients had better financial conditions [6]. In fact, we should pay more attention to cataract patients in poor areas, because cataracts have a greater impact on their lives.
However, the impact of visual impairments on the quality of life after cataract surgery is unclear. Previous analyses of HRQoL assessments using generic instruments results in cataract subjects. Most studies show a strong correlation between binocular vision and VRQOL before cataract surgery. [7][8][9]. After cataract surgery, stereopsis was found to be strongest correlation with VRQOL, followed by binocular contrast sensitivity, while visual acuity shows only a weak correlation. But, other studies have suggested that changes in visual acuity and disability glare are related to changes of VRQOL, but not to contrast sensitivity [10].
The 25-item National Eye Institute Visual Functioning Questionnaire (NEI VFQ-25) which including emotional well-being and social functioning item is a reliable questionnaire performed to assess the influence of vision on quality of life. It is widely used in many countries of the world [11][12][13][14][15].The Chinese version of NEI-VFQ-25 has been verified in Chinese population. The results suggestion that the questionnaire is an effective way to evaluate the vision-related quality of life of patients with eye diseases in China [16].
Due to conflicting evidence, the aim of this study was to assess the impact of cataract surgery on VRQOL using NEI-VFQ-25 in China.

Methods
This study was approved by the ethics committee of Eye hospital, Wenzhou Medical University. All patients signed informed consent. All study procedures according to the Declaration of Helsinki.

Study Design and Sample
A prospective cohort study was conducted between May 2019 and June 2019 in the Naqu, Tibet, China. All of the cataract patients who matched the inclusion criteria were invited to participate in this study. Patients were asked to complete the questionnaire before cataract surgery and again 3 months after cataract surgery.
The following demographic and clinical data were collected: gender,age, sex, ,ethnicity, marital status, live alone, education level , currently employed, wears glasses, takes prescription medication, co-morbid condition.
Inclusion criteria for subjects were as follow: age > 40 years; age-related cataract need cataract surgery. Exclusion criteria were: can't understand questionnaire; diseases cause significant ocular conditions; other systemic diseases.

Questionnaire
The impact of visual impairment on vision-related quality of life was measured by NEI VFQ-

Statistical analysis
Descriptive analyses were used to record the basic demographic characteristics of the population.
The influence of cataract surgery on the VRQOL score using generalised linear estimating equations (GEE) model. The GEE model was fitted for the 247 participants for whom complete before and after surgery data were available. Time, visual acuity and contrast sensitivity(before or after surgery) was added to the model as an explanatory variable.
All statistical analyses used the SPSS 12.0 software (SPSS, Chicago, IL, USA). Significant difference set at P value < 0.05.

Results
A total of 122 cataract patients completed ophthalmic and physical examination before the cataract surgery and completed the questionnaire. Five cataract patients lost followup after cataract surgery. The final response rate was 95.1%.
At last, 117 subjects was recruited in this study, including 50 males. The mean age was 63 ± 8.5 years. The 99% patients were out of work. In terms of education, only 11% of patients completed junior high school education or higher education.
There was no significant differences between subjects who completed two questionnaires and those who only completed the questionnaire before surgery at baseline information, detail see Table 1. The NEIVFQ-25 scores for cataract patients before and after cataract surgery are showed in Table 2. Subjects with cataract have low HRQoL, Table 2 Vision-related quality of life scores before and after cataract surgery (n = 117) It will improve 15 points in the VRQOL composite score postoperation after adjusting for potential confounders (p < 0.001). In addition, there were significantly associated with improvement in VRQOL in binocular contrast sensitivity and stereopsis after surgery, interesting, visual acuity was not.
The VRQOL score will improve 13 points if one log unit contrast sensitivity increased(p < 0.001). On the contrary, VRQOL score will decrease 3 points if increase one log in stereopsis (p < 0.001).

Discussion
To our knowledge, this is the first study comparing quality of life before and after cataract surgery inTibetan popolation. We found that NEIVFQ-25 scores for cataract patients were significant improvement after cataract surgery. Others also found the same results that cataract surgery could significant improve quality of life in Japan and the USA population [17,18]. However, what needs to be noticed is that NEI VFQ-25 measures the combination of visual function and social emotional structure but lacks visual function evaluation. This may reduce the effectiveness of the composite score.
As we predicted, the scores of quality of life in cataract patients were very low before surgery. The lowest item were role difficulty and mental health. It mean that cataract seriously affects the patient's mental health.
Visual impairment affects patients 'daily activities, leading to reduced social interactions and further exacerbates patients' psychological symptoms. Fagers found that psychiatric symptoms will increase with decreased of vision, but better as vision improved [23]. These results suggest that we should give more mental health attention to cataract patients.
We found that improvement in contrast sensitivity and stereopsis were related to improvement in VRQOL after cataract surgery, however, visual acuity was not association with VRQOL. We further found that VRQOL score will improve 13 points if one log unit contrast sensitivity increased after adjusting for potential confounders. Previous research come to the same conclusion [6,7]. The reason why contrast sensitivity affects quality of life is that contrast sensitivity is needed in everyday activities. This result suggested that we need take contrast sensitivity and stereopsis into account when assess the impairment caused by cataract.
We also found that the improvement in stereopsis was significantly associated with improved VRQOL after cataract surgery. However, previous studies rarely measured stereopsis when investigating the effects of cataract surgery on VRQOL. More and more research found that stereopsis is significantly associated with improvements in VRQOL.
A UK study found that the most strongly association with changes in VRQOL after surgery was stereopsis [24]. Previous studies examining the impact of cataract surgery on VRQOL have seldom measured stereopsis, which was significantly associated with improved VRQOL. The studies from Spain and Denmark also found the same results [25].The specific mechanism by which stereopsis affects quality of life is still unclear, we need to study further.
The advantages of this article was that it is the first to assess cataract surgery on VRQOL in Tibetan population. Tibet is one of most poor area in China. Previous studies have seldom included rural inhabitants, and more than 93% of patients in this study were rural residents. It is important to concern the impacted of cataract surgery on VRQOL in poor areas. Another advantage of this study is using GEE linear regression model to eliminate other factors which may affect the vision-related quality of life, such as co-morbidities including and medication usage.

Conclusions
Cataracts significantly affect patients' HRQoL. Our results showed that improves the HRQoL at 3 months after cataract surgery. We also found that the improvement in stereopsis was significantly associated with improved VRQOL after cataract surgery.

Abbreviations
Vision

Availability of data and materials
Data will be available upon request by email.

Ethics approval and consent to participate
All procedures performed in this study involving human participants were in accordance with the ethical standards of the institutional and/or national research committee (Research Ethics Committee of UFVJM, 2174074) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. All subjects signed a written informed consent form before the beginning of this study.

Consent for publication
Not applicable.