Prevalence of cataract and cataract surgery in urban and rural Chinese populations over 50 years old: a systematic review and Meta-analysis

PINK1-mediated mitochondrial autophagy protects lens epithelial cells by reducing ROS and apoptosis

Cataracts are one of the primary causes of blindness worldwide; however, their pathogenesis remains unclear. Oxidative stress and apoptosis are two dominant inducers in the progression of cataracts; however, little is known about the specific mechanisms associated with mitophagy. This study aimed to investigate the role of PTEN-induced putative kinase 1(PINK1)-mediated mitophagy in cataract development. Initially, we induced a rat cataract model using sodium selenite and observed the upregulated expression of PINK1 and other autophagy-related proteins within lens epithelial cells, accompanied by apoptosis. Furthermore, the survival rate of human lens epithelial cells was significantly reduced by H2O2 treatment. However, PINK1 overexpression reduced ROS levels, allowing cells to survive. This reduction in reactive oxygen species (ROS) levels led to a decrease in cleaved caspase-3 and Bcl-2-associated X protein (Bax) expression and an increase in B-cell lymphoma 2 (Bcl-2) levels. In summary, PINK1 maintains mitochondrial functional stability and inhibits apoptosis by activating mitophagy, thus potentially playing a crucial protective role in cataract pathogenesis.

Factors affecting the refractive error after cataract surgery

Modern cataract surgery has entered the era of precision refractive surgery and is no longer only about the restoration of vision, and the factors affecting the refractive error after cataract surgery are gaining increasing attention with the patients' growing expectation of postoperative visual quality. The refractive error after cataract surgery is related to the accurate measurement of ocular biological parameters, the optimization of the intraocular lens calculation formula, and the prediction of the effective lens position. Clinicians must consider multiple factors to reduce the postoperative refractive error and improve the postoperative satisfaction of cataract patients. In this work, we review factors that affect the refractive error after cataract surgery.

Assessing the Impact of AI-Assisted Portable Slit Lamps on Rural Primary Ophthalmic Medical Service

PURPOSE

To investigate the effect of an AI-assisted portable slit lamp (iSpector) and basic ophthalmology training on cataract detection, referral, and surgery rate in rural areas.

METHODS

This randomized control trial randomly assigned 63 village doctors to either the AI-assisted group (providing iSpector and training) or the control group (providing training). Doctors were followed for 1 year before intervention as a baseline and 1 year after to make the comparison. Multivariable Poisson regression was applied to compare the difference in cataract detection, referral, and surgery rate between the two groups, adjusted for primary doctors' baseline characteristics. We further conducted subgroup analysis to estimate the change after the intervention.

RESULTS

Compared to the control group, the detection, referral, and surgery rate of cataracts among the AI-assisted group was comparable, 1.7 times higher, and 4.9 times higher, respectively. Providing iSpector and training increased the detection, referral, and surgery rate of cataracts. However, only based on training to elevate the detection rate of cataracts did not change the referral and surgery rate.

CONCLUSIONS

iSpector helps village doctors detect and refer cataract patients appropriately, thus increasing the probability that patients receive cataract surgery.

Global prevalence of cataract surgery

PURPOSE OF REVIEW

The objective of this review article is to ascertain the global distribution of cataract surgery and evaluate the extent of its coverage in recent years.

RECENT FINDINGS

The cataract surgical rate (CSR) has been reported from 36 to 12 800 (per million population) across different countries. The average cataract surgical coverage (CSC) in the majority of countries was around 50% or lower. Additionally, in many countries, the efficient CSC (eCSC) deviates from the CSC, emphasizing the importance of attention to the quality of surgical procedures. Socioeconomic status and access to health services are key determinants in the distribution of cataract surgery. This procedure is more prevalent among older individuals, with a higher incidence among men and private insurances tend to cover a larger portion of cataract surgeries. The pandemic of COVID-19 has had a detrimental effect on cataract surgery rates in numerous countries.

SUMMARY

The rate of cataract surgery and its extent of coverage in certain countries is inadequate. The primary factor influencing the quantity and coverage of cataract surgeries is the economic status of the countries. Additionally, government support through insurance and the provision of appropriate healthcare services can contribute to an increase in cataract surgeries.

Anxiety and depression in Chinese cataract patients: a network analysis

BACKGROUND

Prior research has demonstrated that people with cataracts are more likely to experience anxiety and depression co-occurring when the condition advances to a degree that impairs vision beyond its physiological effects. According to network theory, there is a connection between the interplay of anxiety and depression and the genesis of comorbidity. Using a network viewpoint, our study examined the network properties of anxiety-depression in cataract patients to pinpoint central and bridge symptoms as well as possible intervention targets for more focused and successful therapies.

METHOD

A total of 1,254 cataract patients were enrolled in our study. The Nine-item Patient Health Questionnaire (PHQ-9) and the Seven-item Generalized Anxiety Disorder scale (GAD-7) were used to measure depression and anxiety symptoms, respectively. The R 4.3.3 software was utilized for network model building and descriptive statistics. Furthermore, we displayed a "Thoughts of death" flow network.

RESULT

In the network, A5 "Restlessness"- D7 "Concentration difficulties" showed the strongest edge. A2 "Uncontrollable worry" and D2 "Depressed or sad mood" could be identified as the central symptoms. A7 "Afraid something will happen" and D7 "Concentration difficulties" could be identified as bridge symptoms. The strongest edge in the flow network was D9 "Thoughts of death"-D6 "Feeling of worthlessness".

CONCLUSION

"Uncontrollable worry", "Depressed or sad mood", "Afraid something will happen" and "Concentration difficulties" could be potential targets for the prevention of anxiety and depression in cataract patients. Furthermore, this study emphasizes how important it is to prevent suicide in cataract patients, and the symptom "Feeling of worthlessness" can be used as an effective target.

NCME-Net: Nuclear cataract mask encoder network for intelligent grading using self-supervised learning from anterior segment photographs

Cataracts are a leading cause of blindness worldwide, making accurate diagnosis and effective surgical planning critical. However, grading the severity of the lens nucleus is challenging because deep learning (DL) models pretrained using ImageNet perform poorly when applied directly to medical data due to the limited availability of labeled medical images and high interclass similarity. Self-supervised pretraining offers a solution by circumventing the need for cost-intensive data annotations and bridging domain disparities. In this study, to address the challenges of intelligent grading, we proposed a hybrid model called nuclear cataract mask encoder network (NCME-Net), which utilizes self-supervised pretraining for the four-class analysis of nuclear cataract severity. A total of 792 images of nuclear cataracts were categorized into the training set (533 images), the validation set (139 images), and the test set (100 images). NCME-Net achieved a diagnostic accuracy of 91.0 % on the test set, a 5.0 % improvement over the best-performing DL model (ResNet50). Experimental results demonstrate NCME-Net's ability to distinguish between cataract severities, particularly in scenarios with limited samples, making it a valuable tool for intelligently diagnosing cataracts. In addition, the effect of different self-supervised tasks on the model's ability to capture the intrinsic structure of the data was studied. Findings indicate that image restoration tasks significantly enhance semantic information extraction.

Famine exposure in early life increases risk of cataracts in elderly stage

BACKGROUND

Epidemiological studies have shown that early-life nutritional deficiencies are associated with an increased risk of diseases later in life. This study aimed to explore the correlation between famine exposure during the early stages of life and cataracts.

METHODS

We included 5,931 participants from the Chinese Longitudinal Healthy Longevity Survey (CLHLS) 2018 cross-sectional data in our study. Subjects were categorized into three groups by their age during the famine: adulthood group, school age famine exposure group, and teenage famine exposure group. Utilizing binary logistic regression models, we investigated the relationship between early-life famine exposure and cataracts.

RESULTS

Compared to the adulthood group, both the school age exposure group (OR = 2.49, 95%CI = 1.89-3.27) and teenage exposure group (OR = 1.45, 95%CI = 1.20-1.76) had a heightened risk of developing cataracts in elderly stage. And the sex differences in the impact of famine during early years on elderly cataract risk were observed, particularly indicating a higher risk among women who experienced childhood famine compared to men with similar exposure.

CONCLUSION

Famine exposure during the early stages of life is associated with a heightened risk of developing cataracts in old age. To prevent cataracts in elderly individuals, particularly in females, measures should be taken to address nutritional deficiencies in these specific periods.

Continuing benefits of the Montreal Protocol and protection of the stratospheric ozone layer for human health and the environment

The protection of Earth's stratospheric ozone (O3) is an ongoing process under the auspices of the universally ratified Montreal Protocol and its Amendments and adjustments. A critical part of this process is the assessment of the environmental issues related to changes in O3. The United Nations Environment Programme's Environmental Effects Assessment Panel provides annual scientific evaluations of some of the key issues arising in the recent collective knowledge base. This current update includes a comprehensive assessment of the incidence rates of skin cancer, cataract and other skin and eye diseases observed worldwide; the effects of UV radiation on tropospheric oxidants, and air and water quality; trends in breakdown products of fluorinated chemicals and recent information of their toxicity; and recent technological innovations of building materials for greater resistance to UV radiation. These issues span a wide range of topics, including both harmful and beneficial effects of exposure to UV radiation, and complex interactions with climate change. While the Montreal Protocol has succeeded in preventing large reductions in stratospheric O3, future changes may occur due to a number of natural and anthropogenic factors. Thus, frequent assessments of potential environmental impacts are essential to ensure that policies remain based on the best available scientific knowledge.

Impact of Telemedicine on Blood Glucose Control and Ophthalmic Screenings for Patients with Diabetes in Remote Areas During the COVID-19 Pandemic: A Real-World Study in Northern Taiwan

Introduction: The purpose of this study was to assess the impact of telemedicine on ophthalmic screening and blood glucose control for patients with diabetes in remote areas of Northern Taiwan during the coronavirus disease 2019 (COVID-19) pandemic. Methods: Telemedicine was implemented in Shiding and Wanli Districts using a 5G platform from April 2021 to December 2022. Patients with poorly controlled diabetes received real-time consultations from endocrinologists at Far Eastern Memorial Hospital, 50 km away, for medication adjustment, diet control, and lifestyle recommendations. The study also provided cloud-upload blood glucose meters for self-monitoring and regular medical advice from hospital nurses. Ophthalmic screenings included fundus imaging, external eye image, and intraocular pressure measurement, with instant communication and diagnosis by ophthalmologists through telemedicine. A satisfaction questionnaire survey was conducted. Results: The study enrolled 196 patients with diabetes. Blood glucose and glycosylated hemoglobin levels were significantly reduced after applying telemedicine (p = 0.01 and p = 0.005, respectively). Ophthalmic screenings led to hospital referrals for 16.0% with abnormal fundus images, 15.6% with severe cataract or anterior segment disorders, and 27.9% with ocular hypertension or glaucoma. Fundus screening rates remained high at 86.3% and 80.4% in 2022, mainly using telemedicine, comparable with the traditional screening rate in the past 5 years. The overall satisfaction rate was 98.5%. Conclusions: Telemedicine showed effectiveness and high satisfaction in managing diabetes and conducting ophthalmic screenings in remote areas during the COVID-19 pandemic. It facilitated early diagnosis and treatment of ocular conditions while maintaining good blood glucose control and fundus screening rates.

Cost-effectiveness and cost-utility of a digital technology-driven hierarchical healthcare screening pattern in China

Utilization of digital technologies for cataract screening in primary care is a potential solution for addressing the dilemma between the growing aging population and unequally distributed resources. Here, we propose a digital technology-driven hierarchical screening (DH screening) pattern implemented in China to promote the equity and accessibility of healthcare. It consists of home-based mobile artificial intelligence (AI) screening, community-based AI diagnosis, and referral to hospitals. We utilize decision-analytic Markov models to evaluate the cost-effectiveness and cost-utility of different cataract screening strategies (no screening, telescreening, AI screening and DH screening). A simulated cohort of 100,000 individuals from age 50 is built through a total of 30 1-year Markov cycles. The primary outcomes are incremental cost-effectiveness ratio and incremental cost-utility ratio. The results show that DH screening dominates no screening, telescreening and AI screening in urban and rural China. Annual DH screening emerges as the most economically effective strategy with 341 (338 to 344) and 1326 (1312 to 1340) years of blindness avoided compared with telescreening, and 37 (35 to 39) and 140 (131 to 148) years compared with AI screening in urban and rural settings, respectively. The findings remain robust across all sensitivity analyses conducted. Here, we report that DH screening is cost-effective in urban and rural China, and the annual screening proves to be the most cost-effective option, providing an economic rationale for policymakers promoting public eye health in low- and middle-income countries.

Crystalline lens nuclear age prediction as a new biomarker of nucleus degeneration

BACKGROUND

The crystalline lens is a transparent structure of the eye to focus light on the retina. It becomes muddy, hard and dense with increasing age, which makes the crystalline lens gradually lose its function. We aim to develop a nuclear age predictor to reflect the degeneration of the crystalline lens nucleus.

METHODS

First we trained and internally validated the nuclear age predictor with a deep-learning algorithm, using 12 904 anterior segment optical coherence tomography (AS-OCT) images from four diverse Asian and American cohorts: Zhongshan Ophthalmic Center with Machine0 (ZOM0), Tomey Corporation (TOMEY), University of California San Francisco and the Chinese University of Hong Kong. External testing was done on three independent datasets: Tokyo University (TU), ZOM1 and Shenzhen People's Hospital (SPH). We also demonstrate the possibility of detecting nuclear cataracts (NCs) from the nuclear age gap.

FINDINGS

In the internal validation dataset, the nuclear age could be predicted with a mean absolute error (MAE) of 2.570 years (95% CI 1.886 to 2.863). Across the three external testing datasets, the algorithm achieved MAEs of 4.261 years (95% CI 3.391 to 5.094) in TU, 3.920 years (95% CI 3.332 to 4.637) in ZOM1-NonCata and 4.380 years (95% CI 3.730 to 5.061) in SPH-NonCata. The MAEs for NC eyes were 8.490 years (95% CI 7.219 to 9.766) in ZOM1-NC and 9.998 years (95% CI 5.673 to 14.642) in SPH-NC. The nuclear age gap outperformed both ophthalmologists in detecting NCs, with areas under the receiver operating characteristic curves of 0.853 years (95% CI 0.787 to 0.917) in ZOM1 and 0.909 years (95% CI 0.828 to 0.978) in SPH.

INTERPRETATION

The nuclear age predictor shows good performance, validating the feasibility of using AS-OCT images as an effective screening tool for nucleus degeneration. Our work also demonstrates the potential use of the nuclear age gap to detect NCs.

Six-Year Change in Cataract Surgical Coverage and Postoperative Visual Outcomes in Rural Southern China: The Yangxi Eye Study

PURPOSE

The purpose of this study was to investigate a 6-year change in cataract surgical coverage (CSC), effective cataract surgical coverage (eCSC), and visual outcomes in an elderly population in rural southern China.

DESIGN

This is a prospective population-based study with a 6-year follow-up.

METHODS

The study included rural residents aged 50 years and above in southern China with comprehensive eye examinations at baseline and follow-up in 2014 and 2020, respectively.

RESULTS

Five thousand six hundred thirty-eight participants underwent baseline examinations (mean age 66.1±10.2 y, 50.8% women); and 3141 (64.9%) of 4841 eligible survivors attended the 6-year follow-up. Cataract surgical coverage was 41.7% and 40.6% at baseline and follow-up, respectively, while eCSC were 32.6% and 26.6%. In multivariate models, the 6-year likelihood of cataract surgery decreased with older age [odds ratio (OR)=0.97 per year, 95% confidence interval (CI): 0.94, 0.99, P =0.012] and worse baseline presenting uncorrected visual acuity (PVA) in the worse-seeing eye (OR=0.35 per unit logarithm of the minimum angle of resolution (logMAR), 95% CI: 0.25, 0.48, P <0.001), and increased with prior cataract surgical history at baseline (OR=3.88, 95% CI: 1.91, 7.09, P <0.001). The likelihood of receiving effective cataract surgery decreased with worse baseline PVA in the worse eye (OR=0.49 per unit logMAR, 95% CI: 0.24, 0.97, P =0.042) and better-seeing eye (OR=0.68 per unit logMAR, 95% CI: 0.48, 0.95, P =0.026). Posterior capsular opacification was the main reason for PVA <6/18, reporting it in logMAR (0.5) in operated eyes (38.4% at baseline; 28.1% at follow-up).

CONCLUSIONS

World Health Organization has established a global target of increasing eCSC by 30% before 2030, but no increase was found in rural southern China between 2014 and 2020, let alone reaching the World Health Organization target of 56.3%. Strategies to improve surgery incidence should focus on older persons and those with worse preoperative PVA.

Time trends and gender disparities of Chinese cataract burden and their predictions

AIM

To evaluate the trends and changes in the number and rates of disability-adjusted life years (DALYs) and prevalence of cataract in China between 1990 and 2019, and to predict the trends of cataract burden from 2020 to 2030.

METHODS

The Global Burden of Diseases (GBD) database was employed to collect the data on DALYs and the prevalence of cataract in China, which was distinguished by age and sex during the past three decades from 1990 to 2019, and then changes in the number and rates of cataract from 2020 to 2030 were predicted. All data were analyzed by the R program (version 4.2.2) and GraphPad Prism 9.0 statistics software.

RESULTS

The number of DALYs of cataract increased from 449 322.84 in 1990 to 1 087 987.61 in 2019, number of cataract cases increased from 5 607 600.94 in 1990 to 18 142 568.96 in 2019. The age-standardized DALY rates (ASDR) generally increased slightly [estimated annual percentage change (EAPC=0.1; 95%CI: -0.24 to 0.45), age-standardized prevalence rates (ASPR) also increased (EAPC=0.88; 95%CI: 0.6 to 1.15). Cataract burden increased with age and female gender. Among the causes of cataract, air pollution was the most important, followed by smoking, high fasting plasma glucose, and high body mass index (BMI). The burden of cataract is predicted to grow persistently from 2020 to 2030, the number of DALYs and prevalence for cataract will rise to 2 336 431 and 43 698 620 respectively by 2030, the ASDR is predicted to be 85/100 000 and ASPR will be 1586/100 000 in 2030, females will still be at greater risk of suffering from cataract than males.

CONCLUSION

The burden of cataract in China kept rising from 1990 to 2019. Increasing age and female gender are risk factors for cataract. Air pollution, smoking, high fasting plasma glucose, and high BMI are associated with cataract. The burden of cataract in China will gradually increase from 2020 to 2030, the elderly women in particular need attention. Our results may be of help for providing reference strategies to reduce cataract burden in the near future.

Auto-refraction versus subjective refraction in different phakic and pseudophakic conditions: the Tehran Geriatric Eye Study (TGES)

AIM

To compare the subjective refraction data with non-cycloplegic auto-refraction findings in the geriatric population above 60 years of age according to the different crystalline lens conditions.

METHODS

This report is a part of the Tehran Geriatric Eye Study (TGES) that was conducted from January 2019 to January 2020 on elderly population 60 years of age and above in Tehran. The samples were selected by multi-stage stratified random cluster sampling. Of 3791 individual invitees, 3310 (response rate: 87.3%) participated in this study. All study participants underwent non-cycloplegic auto-refraction (auto-refractometer/keratometer Nidek ARK-510) and subjective refraction.

RESULTS

Regarding the sphere, eyes with mixed cataract had the worst limits of agreement (LoA: -1.24 to 0.87) and the best agreement was related to the pseudophakic eyes (LoA: -0.83 to 0.54). The highest (0.27±0.31 D) and lowest (0.21±0.27 D) differences between the two methods regarding the cylinder power were observed in eyes with cortical cataract and normal eyes, respectively. The worst LoA between the two methods in measuring the cylinder power was related to the eyes with mixed cataract (LoA: -0.44 to 0.96). Regarding the J0 (horizontal/vertical components of astigmatism), the mean values of J0 obtained by auto-refraction were tended more toward against the rule direction in all crystalline lens conditions, and the two methods had the greatest difference in cortical cataract cases (0.05±0.17 D). Regarding the J45 (oblique components of astigmatism), the lowest (0±0.11 D) and highest (-0.01±0.12 D) differences were observed in normal eyes and eyes with cortical cataract, respectively.

CONCLUSION

The auto-refractometer/keratometer Nidek ARK-510 results in the elderly with different phakic and pseudophakic conditions do not correspond well with subjective refraction findings. This discrepancy in spherical findings is more pronounced in individuals with mixed cataract than in other cases.

Involvement of IGF1 in endoplasmic reticulum stress contributes to cataract formation through regulating Nrf2/NF-κB signaling

Endoplasmic reticulum (ER) stress is reportedly involved in the development of ophthalmic diseases. This study aimed to investigate the role and potential mechanism of insulin-like growth factor 1 (IGF1) in ER stress. A mouse cataract model was constructed by subcutaneous injection of sodium selenite, and sh-IGF1 was used to evaluate the effect of silencing IGF1 on cataract progression. Slit-lamp and histological examination of the lens were performed to examine lens damage. The regulatory effects of IGF1 on inflammatory responses, oxidative stress, and ER stress were evaluated using ELISA, reverse transcription-quantitative PCR (RT-qPCR), and immunoblotting analysis. Tunicamycin was used to induce ER stress in the lens of epithelial cells. The NF-E2 related factor-2 (Nrf2) inhibitor ML385 and nuclear factor-κB (NF-κB) agonist diprovocim were used to confirm whether IGF1 regulates inflammation and ER stress through Nrf2/NF-κB signaling. Silencing IGF1 alleviated lens damage and reduced lens turbidity in the cataract mice. Silencing IGF1 inhibited inflammatory response, oxidative stress and ER stress response. Meanwhile, IGF1 was highly expressed in sodium selenite-treated lens epithelial cells. The ER stress agonist tunicamycin suppressed cell viability as well as induced ER stress, oxidative stress and inflammation. Silencing IGF1 increased cell viability, EdU-positive rate and migration. Also, silencing of IGF1 reduced inflammation and ER stress via regulating Nrf2/NF-κB pathway. This study reveals silencing IGF1 attenuated cataract through regulating Nrf2/NF-κB signaling, which shares novel insights into the underlying mechanism of cataract and provides potential therapeutic target for cataract.

The Role of Village Doctors in Residents' Uptake of Eye Screening: Evidence from Ageing Residents in Rural China

The lack of formal eye screening is the main reason for insufficient eye care utilization in rural China. Cataract, in particular, is increasingly prevalent with the aging population, but the treatment rate is relatively low. Village doctors are the most accessible health care resource for rural residents, receiving few empirical investigations into their role in eye care. This study aims to assess the role of village doctors in residents’ uptake of eye screening (vision and cataract screening), the first step of cataract treatment. Data come from a community-based, cross-sectional survey conducted in 35 villages of a county of the Gansu Province, Northwestern China, in 2020. Among 1010 residents aged ≥ 50 and 35 village doctors, the multivariate logistic regression shows that village doctors’ age, time spent on public health service, and service population were positively associated with residents’ uptake of vision and cataract screening. Village doctors were capable of playing an active role in primary eye health services due to their richer knowledge about cataracts than residents (accuracy rate 86.75% vs. 63.50%, p < 0.001), but less than half of them were willing to undertake eye screening. This study highlights the positive role of village doctors in aging residents’ eye screening and the potential role in improving the uptake of eye screening by offering health education.

Difference in Quality of Vision Outcome among Extended Depth of Focus, Bifocal, and Monofocal Intraocular Lens Implantation

We aimed to compare the postoperative quality of vision among patients who received extended depth of focus (EDOF), bifocal, and monofocal intraocular lens (IOL) implantation. A retrospective study was conducted, and 87 patients who underwent cataract surgery were enrolled. Patients were categorized into different groups according to IOL design, with 24, 29, and 34 individuals constituting bifocal, EDOF, and monofocal groups. Preoperative and postoperative visual acuity (VA), biometry data, refractive status, contrast sensitivity (CS), higher-order aberrations (HOAs), and a quality of vision questionnaire that consisted of 11 questions were obtained 1 month postoperatively. The Kruskal−Wallis test and Pearson’s chi-square test were applied for statistical analyses. The postoperative CDVA was better in the EDOF group than in the bifocal group (p = 0.043), and the residual cylinder was lower in the EDOF groups than in the other two groups (both p < 0.05). The CS was worse in the EDOF group than in the other two groups (all p < 0.05), while the spherical aberration and trefoil were lower in the EDOF group than in the bifocal group (both p < 0.05). In terms of the quality of vision, the scores were better in the monofocal group than in the EDOF group in seven items (all p < 0.05), and the quality of vision in the bifocal group was better than in the EDOF group in small print reading (p = 0.042). In addition, the incidence of glare was lower in the monofocal group than in the other two groups (p < 0.001), while the spectacle dependence ratio was significantly higher in the monofocal group compared to the other two groups (p < 0.001). In conclusion, the general quality of vision was better in the monofocal group compared to the bifocal and EDOF groups, while the spectacle dependence ratio was significantly higher in the monofocal group than in the other two groups.