Article Text

Normative patterns and factors associated with presbyopia progression in a multiethnic Asian population: the Singapore Epidemiology of Eye Diseases Study
  1. Shivani Majithia1,
  2. Kah Hie Wong1,
  3. Miao Li Chee1,
  4. Zhi-Da Soh1,
  5. Sahil Thakur1,
  6. Xiao Ling Fang1,
  7. Zhen Ling Teo1,
  8. Charumathi Sabanayagam1,2,
  9. Yih Chung Tham1,2,
  10. Ching-Yu Cheng1,2,3
  1. 1Ocular Epidemiology, Singapore Eye Research Institute, Singapore National Eye Centre, Singapore, Singapore
  2. 2Ophthalmology and Visual Science Academic Clinical Program, Duke-NUS Medical School, Singapore, Singapore
  3. 3Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
  1. Correspondence to Professor Ching-Yu Cheng, Singapore Eye Research Institue, 20 College Road, The Academia, Level 6, Singapore, Singapore 169856; chingyu.cheng{at}duke-nus.edu.sg

Abstract

Background/Aim To investigate normative patterns and factors associated with presbyopia progression in a multiethnic Asian population.

Methods Malay, Indian and Chinese participants aged 40–80 years who had baseline and 6-year follow-up examinations with subjective refraction data were recruited from the Singapore Epidemiology of Eye Diseases Study. Presbyopia progression was defined as an increase in near addition power of ≥+0.50 dioptre (D) from baseline to follow-up visit. Modified Poisson regression analyses were used to determine baseline factors associated with presbyopia progression.

Results From the eligible 3974 eyes, 2608 eyes were included for final analysis after excluding eyes with a history of cataract surgery (929 eyes) and best-corrected distance visual acuity worse than 20/40 (342 eyes). Overall the mean near addition power change over 6 years was +0.25 D; Malays showed greater change (+0.37 D) compared with Indians (+0.23 D) and Chinese (+0.16 D). After adjusting for baseline age, gender, body mass index, hypertension, cataract, refractive error and daily hours of reading and writing, Malays were more likely to have presbyopia progression compared with Chinese (RR (relative risk)=1.67; 95% CI 1.43 to 1.95; p<0.001) and Indians (RR=1.45; 95% CI 1.25 to 1.68; p<0.001). Individuals aged 60–69 years (RR=0.77; p=0.006) and ≥70 years (RR=0.51; p<0.001) were less likely to progress in presbyopia compared with those aged 40–49.

Conclusion In this Asian population, the near addition power change over 6 years was lower than the current near addition prescription guidelines (+0.25 D vs +0.60 D). Our findings may help update near addition prescription guidelines that can be more tailored to Asians.

  • optics and refraction
  • eye (globe)
  • vision
  • epidemiology
  • public health

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Introduction

Presbyopia is an unavoidable and progressive process of ageing which involves near visual impairment (NVI) due to reduced or loss of accommodative ability, commencing around the age of 40.1 2 Globally, approximately one billion adults were affected by NVI as a result of uncorrected presbyopia.3 4 With the ageing trend worldwide, the number of individuals with presbyopia is expected to further increase.3 4 NVI is especially detrimental to the elderly as it also leads to decreased productivity, independence and quality of life.5–9 Nevertheless, NVI can be easily corrected with near vision correction.

While there are several previous reports on the prevalence of presbyopia,3 4 6 10 studies on presbyopia progression are scarce, especially in Asian populations. Donders11 first reported on changes in amplitude of accommodation with age and was followed by guidelines set by Hofstetter and Pointers12 13 on the estimated decrease in accommodative amplitude with older age, which had since been widely used by eye care practitioners when prescribing near vision correction. Based on these guidelines, presbyopia progression was commonly inferred as approximately +0.10 dioptre (D) increment per year older.13 Nevertheless, it should be noted that these guidelines were established over two decades ago and were established based on a predominantly Caucasian population, with little representation of Asians.13 Furthermore, it is also unclear whether patterns of presbyopia progression remain the same or different across demographic, systemic and ocular factors such as age, gender, socioeconomic status, near work habits and refractive status.11 14–16 To date, only one Asian population study has reported on the patterns of presbyopia progression over time,17 further highlighting the lack of knowledge in this aspect among Asians.

Hence, the purpose of this study was to evaluate the normative pattern and factors associated with presbyopia progression in a multiethnic Asian population. Findings from this study will further provide evidence-based understanding on presbyopia progression among Asians.

Materials and methods

Study population

Study subjects were enrolled from the Singapore Epidemiology of Eye Diseases (SEED) Study, comprising three major ethnic groups in Singapore, namely Malays, Indians and Chinese. Methodology and details of the SEED Study were reported previously.18–23 Study participants were randomly sampled from the south-western part of Singapore, using a standardised study protocol across the three ethnic groups of subjects, including 3280 Malays (2004–2006, response rate 78.7%),18 3400 Indians (2007–2009, response rate 75.6%)19 and 3353 Chinese (2009–2011, response rate 72.8%).20 The 6-year follow-up studies for each ethnicity were conducted from 2010 to 2017, involving 1901 Malays (2010–2014, response rate 72.1%),21 2200 Indians (2013–2015, response rate 75.5%)22 and 2661 Chinese (2015–2017, response rate 87.7%).23

Inclusion and exclusion criteria

Eyes with data on subjective refraction at both baseline and follow-up studies were included. Eyes with any previous cataract surgeries (based on baseline or follow-up visit evaluations) were excluded due to the loss of accommodation postoperatively. Additionally, eyes with distance best-corrected visual acuity (BCVA) worse than 20/40 were also excluded in order to minimise the effect of sight-threatening pathology on near vision measurements.

Ocular examinations

Every participant underwent standardised ocular examinations. Before pupil dilation, intraocular pressure was measured with Goldmann applanation tonometer (Haag-Streit, Bern, Switzerland). Non-contact partial coherence laser interferometer (IOLMaster V.3.01; Carl Zeiss Meditec, Jena, Germany) was used to measure axial length. After dilation, cataract grading was determined using the Lens Opacities Classification System III24 and fundus biomicroscopy was performed.

Visual acuity and subjective refraction

Presenting distance visual acuity (VA) with habitual optical correction (if any) was measured monocularly and binocularly using the ETDRS logarithm of the minimum angle of resolution (logMAR) numerical chart (Lighthouse International, New York, USA) at a distance of 4 m. Binocular presenting near VA with habitual optical correction (if any) was measured using the ETDRS logMAR numerical near chart (Precision Vision, La Salle, Illinois, USA) at 40 cm. VA was tested in standardised lighting conditions and was recorded in logMAR notation.

When distance or near presenting VA was worse than 20/40, subjective refraction was then performed by a certified optometrist to determine BCVA for distance. After the participant was fully corrected for distance, near addition power was further determined by adding plus lenses in increments of +0.25 D lenses monocularly to their distance prescription until near BCVA was achieved. The magnitude of near addition power was then recorded. Near addition power change over 6 years was measured as the difference between near addition power at baseline and follow-up visits.

Definition of presbyopia progression

Presbyopia progression was defined as an increase of ≥+0.50 D of near addition power between baseline and follow-up visits, based on measurements from subjective refraction.

Systemic examinations and other measurements

Body mass index (BMI) was calculated as body weight (in kilograms) divided by body height (in metres) squared. Normal BMI was defined as 18.5≤BMI<25, underweight was defined as BMI <18.5, overweight was defined as 25≤BMI<30, and obese was defined as BMI ≥30. Smoking status was assessed through self-reported questionnaires and was defined as current and non-current smokers. Hypertension was defined by systolic blood pressure (BP) ≥140 mm Hg, diastolic BP ≥90 mm Hg, physician’s diagnosis, use of hypertensive medication and/or self-reported history of hypertension. Diabetes mellitus was defined by random glucose ≥11.1, glycosylated haemoglobin (HbA1C) ≥6.5%, use of diabetic medication(s) and/or self-reported history. Kidney function was assessed using estimated glomerular filtration rate from serum creatinine using the Chronic Kidney Disease Epidemiology Collaboration equation.22 Subjects were defined to have chronic kidney disease if the glomerular filtration rate was less than 60 mL/min/1.73 m2.

Non-fasting venous blood samples were collected for biochemistry tests including plasma cholesterol (total cholesterol, low-density lipoprotein and high-density lipoprotein), serum triglyceride, HbA1C, creatinine and random glucose.

We used interviewer-administered questionnaires in order to obtain participant information on demographics, lifestyle risk factors and medical history. In addition, we asked them ‘currently, how many hours per day do you read and/or write’ in order to assess daily near work.

Statistical analysis

All statistical analyses were performed using STATA Statistical Software V.15.0. Eye-specific data were used for all statistical analyses.

Baseline characteristics of all three ethnic groups were compared using one-way analysis of variance for continuous variables, and the Pearson’s χ2 test was used for categorical variables. Univariate linear regression analyses were performed to investigate the association between ocular, systemic and demographic risk factors with the change in near addition power. Variables which were significantly associated with change in near addition power in univariate analyses (p<0.05; online supplementary table 2) and factors such as gender, refractive status and axial length were then further included in the multivariable analyses to evaluate baseline factors associated with change in near addition power over 6 years. On the other hand, modified Poisson model with robust variance was used to evaluate baseline factors associated with presbyopia progression over 6 years. To account for the correlation between pairs of eyes for each individual, generalised estimating equation models with exchangeable correlation structures were applied in the above-mentioned models.

Results

A subgroup of SEED participants with complete subjective refraction data at both baseline and follow-up visits were included in this analysis (n=2044; 3979 eyes). Of which, 929 eyes were further excluded due to cataract surgery history at baseline or during follow-up and 342 eyes were excluded due to distance or near BCVA worse than 20/40, leaving 2708 eyes (904 Malays, 828 Indians, 976 Chinese) from 1547 subjects available for final analysis. The mean age of participants was 58.9±9.1 years, 51.7% were female, 65% had hypertension, 28.1% had diabetes, and the mean axial length was 23.6±1.2 mm (table 1).

Table 1

Baseline characteristics of included participants

The mean near addition power change over 6 years was +0.25 D in the overall sample. When comparing across ethnic groups, Malays showed greater change in near addition power (+0.37 D) compared with Indians (+0.23 D) and Chinese (+0.16 D) (table 2.) This was consistently observed for the baseline age groups of 50–59, 60–69 and 70+ years (online supplementary figure 1). Correspondingly, a greater proportion of Malays (53.2%) had presbyopia progression over 6 years compared with Indians (39.9%) and Chinese (31.3%) (all p<0.001) (online supplementary table 1). Furthermore, across the range of axial length profiles, Malays consistently showed higher near addition power change compared with Chinese and Indians (figure 1).

Table 2

Near addition power change (in dioptre) over 6 years, stratified by age groups

Figure 1

Change in near addition power over 6 years, across baseline axial length and by ethnicity.

We further evaluated the factors associated with near addition power change over 6 years (table 3). After adjusting for baseline age, gender, ethnicity, BMI categories, presence of hypertension, daily hours spent reading and writing, presence of cataract, and refractive status, Malays were significantly associated with greater increment in near addition power over 6 years when compared with Chinese (β=0.21; 95% CI 0.16 to 0.26; p<0.001) and Indians (β=0.19; 95% CI 0.13 to 0.24; p<0.001; data not shown). In addition, longer hours of daily reading and writing at baseline (β=0.13; 95% CI 0.04 to 0.23; p=0.007; comparing between >5 hours and <2 hours) was also significantly associated with increment in near addition power. In contrast, older age was associated with near addition power decrement (per decade; β=−0.12; 95% CI −0.14 to 0.09; p<0.001). In further sensitivity analysis which excluded participants aged ≥70 years old, age, Malay ethnicity and longer hours of daily reading and writing remained significant (all p≤0.01; online supplementary table 3).

Table 3

Baseline factors associated with near addition power change over 6 years

On the other hand, when evaluating presbyopia progression as outcome of interest, after adjusting for baseline age, gender, ethnicity, BMI, hypertension, presence of cataract, refractive error status and daily hours spent reading and writing, Malays were more likely to have presbyopia progression compared with Chinese (RR (relative risk)=1.67; 95% CI 1.43 to 1.95; p<0.001) and Indians (RR=1.45; 95% CI 1.25 to 1.68; p<0.001; data not shown). Older age was associated with lower likelihood of presbyopia progression (per decade; RR=0.81; 95% CI 0.75 to 0.87; p<0.001). In particular, when comparing with individuals aged 40–49 years, individuals aged ≥70 years were almost 50% less likely to have presbyopia progression over 6 years (RR=0.51; 95% CI 0.39 to 0.67; p<0.001). Additionally, individuals reading and writing over 5 hours a day at baseline were more likely to have presbyopia progression (RR=1.29; 95% CI 1.04 to 1.60; p<0.020; table 4). In further sensitivity analysis where participants aged ≥70 years old were excluded, younger age, Malay ethnicity and longer hours of reading and writing remained significantly associated with higher likelihood of presbyopia progression (all p≤0.04; online supplementary table 4).

Table 4

Baseline factors associated with presbyopia progression

Discussion

Our study investigated the patterns and factors associated with presbyopia progression among the three major ethnic groups in Asia, namely Chinese, Indians and Malays. To the best of our knowledge, this is the first Asian study evaluating longitudinal near addition power change in a multiethnic population. We found that the overall near addition power change over 6 years was +0.25 D, with Malays having a greater change (+0.37 D) compared with Indians (+0.23 D) and Chinese (+0.16 D). Our overall near addition power change over 6 years is notably lower than traditional guidelines (+0.60 D over 6 years).13 Interestingly, we also observed that presbyopia progression differs among Asians, with Malays having higher proportion of presbyopia progression over 6 years (53.2%) compared with Chinese (31.3%) and Indians (39.9%); this observation was also independent of baseline refractive error status and axial length profiles. Overall, our findings suggest that a more Asian-specific guidelines for near vision correction may be warranted.

Compared with a previous Chinese population study which reported a near addition power change of +0.15 D over 6 years,17 our Chinese cohort demonstrated almost identical power change (+0.16 D). In addition, we also observed that older age groups were less likely to have presbyopia progression. Similar to our findings, Han et al17 also observed a decrement in near addition power change with older age groups. The lower likelihood of presbyopia progression in older age groups for all ethnicities is likely due to the ‘plateauing effect’ of the residual amplitude of accommodation with older age. In fact, according to Hofstetter’s average expected amplitude formula,25 participants aged ≥70 years would have an amplitude of accommodation reduced to nil, and near addition power is expected to remain stable thereafter. Hence, this might explain our observation that participants aged 40–60 years of age were more likely to have presbyopia progression than those aged ≥70. Given that individuals aged between 40 and 60 years are typically still working and have relatively higher visual demand for near work, our findings further suggest that this group of individuals may potentially benefit from more frequent optometric examinations and updates on near vision prescription.

In view of the aforementioned postulation that individuals aged ≥70 years would have stable near addition power over time, we further performed a sensitivity analysis excluding subjects aged ≥70 years when evaluating determinants of presbyopia progression. In this sensitivity analysis, we still observed Malay ethnicity to be associated with a higher likelihood of presbyopia progression compared with Chinese and Indians (online supplementary table 4). We also observed that individuals with longer hours of daily near work at baseline were associated with higher likelihood of presbyopia progression over time. This may be because individuals who performed longer hours of near work were also likely to have higher near visual demands and therefore more sensitive to blur perception for near tasks. Thus, these individuals typically favour more ‘plus’ power during near addition evaluation.

Our study had several strengths. First, the findings were derived from a large multiethnic Asian population. Second, standardised examination protocol was used for all three ethnicities, across both baseline and follow-up examinations. Third, our study included a wide range of systemic and ocular parameters for the evaluation of determinants associated with presbyopia progression. Nevertheless, it should be noted that this study only included a subsample of the original SEED Study as only study participants with complete subjective refraction data at both baseline and follow-up visits were included for final evaluation. Compared with included participants, the excluded participants had higher educational level, higher income level, more myopic refractive error and reported longer hours of daily near work at baseline (all p≤0.003; online supplementary table 5). Although baseline age, gender and systemic disease profiles were not significantly different between the included and excluded participants (all p≥0.103), potential selection bias still cannot be entirely ruled out.

In conclusion, we observed that the overall near addition power change in this multiethnic Asians population was substantially lower than the current widely used guidelines for near addition prescription. Presbyopia progression also varied among Asians, with Malays having a higher rate of presbyopia progression than Chinese and Indians, independent of baseline refractive error status. Our findings may help to update near addition prescription guidelines that are potentially more tailored to Asians.

Acknowledgments

The authors thank the ocular epidemiology research group and data science unit of the Singapore Epidemiology Research Institute for their invaluable contributions.

References

Supplementary materials

  • Supplementary Data

    This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.

Footnotes

  • SM and KHW contributed equally.

  • YCT and C-YC contributed equally.

  • —————

  • SM and KHW are joint first authors.

  • YCT and C-YC are joint senior authors.

  • SM and KHW contributed equally.

  • YCT and C-YC contributed equally.

  • Contributors SM, KHW, YCT, CS and C-YC conceived and designed the study. SM, KHW, YCT, MLC, Z-DS, ST, XLF and ZLT analysed and interpreted the data. SM, KHW, MLC and YCT wrote the manuscript. All authors reviewed and provided critical feedback to the final manuscript.

  • Funding This study is funded by the National Medical Research Council (grant numbers: NMRC/CIRG/1417/2015, NMRC/MOH-TA18nov-0002, NMRC/0796/2003 and A*STAR BMRC 08/1/35/19/550, NMRC/1249/2010, and NMRC/CIRG/1371/2013).

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval All study procedures were conducted in accordance with the Declaration of Helsinki and were approved by the SingHealth Centralised Institutional Review Board. Informed consent was obtained from all study participants.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement No data are available. Please contact the corresponding author for data availability (chingyu.cheng@duke-nus.edu.sg).