The morphological type of senile cataract and its effect on uptake of cataract surgery

INTRODUCTION

A cataract is any opacity of the crystalline lens irrespective of its size, location and its effect on vision. However, when located within the pupillary area, the lenticular opacity interacts with the incident light and affects the quality of the image on account of various light-related phenomena.^[1] In most cases, cataract is a gradually progressive senile process, affecting individuals from the fifth decade onwards.^[2] There is evidence to support those factors related to metabolism, genetics, trauma, exposure to ultraviolet rays, race and geographical location also play a role in the development of cataracts.^[2-4]

Blindness related to cataracts is the major cause of agestandardised disability-adjusted life years in Southeast Asia.^[5] World Health Organization (WHO)/National Programme for Control of Blindness survey estimated that there are 22 million blind people in India; about 80% of this is due to cataracts incurring an estimated gross national income (GNI) loss of INR 845 billion, with per capita loss of GNI per blind person of INR 170,625.^[6] Therefore, blindness due to cataracts is a major concern in India in terms of morbidity, and its socio-economic impact. The treatment of cataracts is mainly surgical. Globally, an increase in the rate of cataract surgery has been registered.^[7,8] In addition, an increase in the overall prevalence of cataracts, and a shift in the morphological types and age of visually significant cataracts towards pre-senile age have been reported.^[2,9] However, the delayed uptake of cataract surgery is not uncommon in rural India.^[10] This study was undertaken to look over the demographic characteristics of persons with different morphological types of senile cataracts, and to know how do the timing of uptake of cataract surgery is affected by the morphological type of senile cataract.

MATERIALS AND METHODS

This cross-sectional study was conducted from July to October 2023 in the ophthalmology department of a tertiary care teaching institute. This study was approved by the Institutional Scientific Research Committee and Institutional Ethical Committee and adhered to the Declaration of Hilinski. Persons admitted for elective cataract surgery, who were aged ≥40 years and had best-corrected visual acuity of ≤6/18 in the affected eye, were invited to participate in this study. Informed consent was obtained for participation and those who consented were enrolled in the study. Enrolled patients were presented with a pre-validated, structured questionnaire [Appendix 1] about demographics (age, gender, housing-urban/rural and vocation-outdoor/indoor), socio-economic information, personal habits (smoking, alcohol and other tobacco intake) and lifestyle (active versus sedentary), comorbid systemic conditions, drug history, previous surgeries, ocular history about trauma, surgery or any other chronic condition). An open-ended question about the reason for the delay in the uptake of cataract surgery was asked. Lifestyle was considered active if there was a daily physical work of ≥30 min for at least 5 days a week, excluding routine household chores.^[11] The primary reason for up-taking the cataract surgery was asked using open-ended questions. An enquiry was made about the reasons behind the delay in uptake of cataract surgery, if any, with the delay being the starting of the visual symptoms till seeking a professional opinion. A comprehensive ocular examination was done that included slit-lamp examination, tonometry, gonioscopy, ocular motility assessment, dilated fundus examination and A-scan biometry. Grading of nuclear sclerosis (NS) and type of cataract was done after dilation on slit-lamp examination. Group one included those with significant NS (≥grade 2), and group two included cataracts other than significant NS (≤NS 1), which included cortical cataract, posterior subcapsular cataract (PSC), and posterior polar cataract (PPC) with or without NS not exceeding grade 1. We used the operational definition of NS, which considered yellowish changes in the central zone of the lens during dilated examination.

Systemic examination, including weight and height, was done to calculate body mass index (BMI). BMI (kg/m²) was divided into four categories – underweight (<18.5), normal (18.5–24.9), overweight (25–29.9) and obese (≥30), as per the WHO classification of BMI for Asia.^[12]

The data were collected in a pro forma and transferred to the Excel sheet (Microsoft corporation; USA); data were analysed using the Statistical Package for the Social Sciences version 26. The descriptive statistics were carried out for both groups. Groups were compared using unpaired t -est, Mann-Whitney test or Welch t-test depending on distribution and variance of data. An association between type of cataract, age, gender, housing (urban versus rural), vocation, lifestyle, comorbidities and BMI were analysed using the Chi-square test of independence and logistic regression. The level of significance was set at <0.05.

RESULTS

A total of 441 eligible patients were enrolled in this study, which included 255 (58%) men and 186 (42%) women. There was no significant difference (P = 0.1) between the mean ± standard deviation (SD) age of men (63.4 ± 9 years) and women (61.6 ± 11 years). Women were more likely than men to have cataracts in pre-senile age than in senile age, χ² (1, n = 395) = 4.5, P = 0.03 [Figure 1].

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Figure 1:

The age and gender-wise distribution of study participants.

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NS of grade ≥2 was seen in 258 (59%) patients, whereas other than NS type of cataract was seen in 183 (41%), with a predominance of PSC [Table 1]. Irrespective of the grade of NS, PSC was seen in 226 (51%) eyes. The mean (±SD) age of cataract surgery in patients with cataracts other than significant NS was 60.4 years compared to the 64.5 years for NS group, and the difference was statistically significant (P < 0.05). The contralateral eye was pseudophakic in 152 (34%) patients, and the mean ± SD duration between cataract surgery in two eyes was 6 ± 1.88 (range 0–12) years.

Other than the NS type of cataract was more likely (1.8:1) but statistically not significant (P = 0.2) amongst those who spent more time outdoors. Cataracts other than significant NS were slightly but significantly (P = 0.003) more likely in patients with rural backgrounds. Smoking, alcoholism, BMI, sedentary lifestyle and diabetes mellitus did not influence age at presentation or type of cataract.

DISCUSSION

The study results revealed that patients with cataracts other than significant NS opt for surgical intervention at a relatively early age, and type of cataract is not affected by demographics. The prevalence of both pre-senile and senile cataracts has increased.^[2,9] However, this shift must be seen in the backdrop of changes in criteria to define age groups. The age between 61–73 years, and 73–85 years is categorised as pre-senile and senile, respectively.^[13] We observed that the proportion of morphological forms of cataracts other than significant NS was slightly over 50% in our cohort. Irrespective of morphological types, a large proportion of patients in our cohort also fall in the pre-senile group.

We found that nearly 43% of persons required cataract surgery before 60 years of age in our study. A similar pattern has been observed in a study on prevalence and epidemiological patterns from central India. The study reported 35.7% of all cataracts in the pre-senile age group and 43.4% were PSC.^[9] Our study observed a similar epidemiological pattern. The PSC and PPC cause more visual disturbance than the cataracts located in the peripheral zone.

We also studied differences in cataract morphology amongst patients from rural and urban backgrounds. Cataracts other than NS were more likely amongst patients from the rural background. Although the difference was small, it was statistically significant. Another reason for this variation in our study may be because of a comparatively much higher number of patients from rural backgrounds (392, 89%) than the patients with urban backgrounds (49, 11%), which might have skewed the result. For the analysis of the vocation, our main aim was to divide it into outdoor and indoor categories to assess the difference in sun exposure. Sun exposure was documented as an important risk factor for NS.^[4] In our study, we did not find a statistically significant association.

Studies have found a significant relationship between gender and type of cataract. A decrease in estrogen levels at menopause and resultant oxidative stress on the lens, has been associated with a higher prevalence of cataracts in women.^[14] However, in our study, no significant difference was found between genders.

Smoking, diabetes and hypertension have been associated with a higher prevalence of cataracts and type of cataract.^[9] The odds of developing nuclear sclerotic cataracts were higher amongst smokers, diabetic and hypertensive people.^[9] We did not find any positive association between smoking, alcoholism, BMI, sedentary lifestyle or diabetes mellitus and type of cataract. A larger cohort might be required to firmly establish or discard any association between these risk factors and type of cataract.

There were some limitations in our study. The sample size was small and a longer duration study with a larger cohort is desirable. Due to the smaller duration of the study, the impact of seasonal variation on the uptake of cataract surgery could not be studied. We used minimum visual acuity (≤6/18) for enrollment purposes only and did not study the correlation between visual acuity and other variables. This could have influenced the timing of the uptake of cataract surgery. The visual acuity of ≤6/18 also led to the exclusion of patients who opted for cataract surgery for reasons not other than visual acuity, such as glare intolerance. Further, the proportion of urban patients was small compared to rural patients, and this might have skewed the results.

CONCLUSION

Demographic factors and physical attributes do not affect the onset and morphological type of cataracts. However, women tend to have pre-senile cataracts. Overall, the proportion of PSC cataracts were higher, especially amongst those who worked outdoors but without any statistical significance.