EPIDEMIOLOGY OF RISK FACTORS OF VARIOUS MORPHOLOGICAL TYPES OF AGE-RELATED CATARACT IN EASTERN REGION OF NEPAL

1* 2 3 4 Namrata Gupta , Poonam Lavaju , Sangeeta Shah , Badri Prasad Badhu Gupta N et al Introduc on Age related cataract is the leading cause of preventable blindness globally, with mul factorial risk factors. Mul ple mechanism contributes to the progressive loss of lens transparency. Objec ve The purpose of this study is to determine the risk factors for different morphological types of senile cataract in eastern region of Nepal. Methodology A hospital based cross sec onal study was conducted in a ter ary care hospital. Four hundred pa ents aged ≥ 50 years with senile cataract a ending eye out pa ent department for one year were enrolled and divided into two groups based on Lens Opaci es Classifica on System (LOCS) III grading. Group A consisted of 'no-moderate' cataract and group B consisted of 'severe' cataract. The parameters studied were age, gender, educa on, occupa on, smoking, alcohol consump on, diabetes and hypertension, body mass index and use of topical or oral medica on. Sta s cal analysis was conducted to find an associa on of various parameters to different morphological type of cataract. Results The mean age of presenta on was 61±9.07 years. Male to female ra o was 1:02. Group A had 154 and group B 246 pa ents respec vely. Sta s cally significant associa on was seen between older age group and severe cataract (p <0.002). Household ac vi es and moderate alcohol consump on alcohol was seen associated with moderate nuclear sclerosis (p <0.001) and posterior sub-capsular cataract (p <0.003) respec vely. High blood pressure was associated with severe Nuclear Sclerosis and Posterior Subcapsular Cataract (p<0.014). Conclusion Older age groups, household ac vi es, moderate alcohol consump on and high blood pressure were found to have significant associa on with age-related cataract.


INTRODUCTION
Age related cataract is the leading cause of blindness in the world today. With an es mated 10.8 million people blind and 35.1 million visually impaired due to cataract, it represents almost 33.4% of all causes of blindness due to 1 eye diseases globally in 2010. In Nepal alone, the current prevalence of cataract is 87,500 and every year about 60,000 people get cataract. Although cataract prevalence is higher among women, cataract surgical coverage rate is 1.2-2 1.7 mes lower for them. Epidemiological studies have established certain risk factors for cataract forma on like age, female gender, gene cs and modifiable risk factors like chronic UV exposure, smoking, alcohol consump on, diabetes, hypertension, low 3 socioeconomic status, certain occupa ons. However, there are no published data regarding the distribu on of these risk factors among the target popula on in Nepal. This study was carried out to iden fy the demographic pa ern and prevalence of various risk factors for morphological types of cataract in our defined popula on. This study may help carry out research on the pathogenesis of lens opacity forma on to prevent or reduce its progression. More importantly, it can aid the current public health efforts to take care of modifiable risk factors.

METHODOLOGY
A hospital based cross -sec onal study was conducted in the out pa ent department of ophthalmology of BP Koirala Ins tute of Health Sciences in eastern Nepal for a dura on of one year. The study popula on was enrolled using convenient and quota sampling method. For sample size calcula on, a pilot study was conducted among pa ents presen ng with senile cataract for one week to find out the prevalence of various morphological types of cataract. A total of 400 eyes of 400 pa ents with age related cataract aged ≥ 50 years were included in the study. The study was approved by the Ins tu onal ethical review board of B. P. Koirala Ins tute of Health Sciences (Code no: IERB/198/014) and in accordance of declara on of Helsinki. Pa ents with lens opacifica on due to trauma, previous history of intra ocular inflamma on, complicated cataract and history of intra ocular surgery in the same eye were excluded from the study. A er obtaining informed consent, pupil was dilated with tropicamide 1% and morphology of the lens was examined under the slit lamp biomicroscope. The Lens Opaci es Classifica on System III (LOCS) was used for grading lens. Lens was classified into four major groups based on slit lamp images. Six images were used for grading Nuclear color (NC) and nuclear opacity (NO) from 0-6.9, five retro-illumina on images for grading cor cal cataract ( C) from 0-5.9, and five retro-illumina on images for grading posterior subcapsular 4 (P) cataract from 0-5.9. Based on severity cataract was divided into three grades as shown in Table 1.
The pa ent with all three types of cataract was categorized under mixed cataract. If the pa ent had bilateral cataract, the eye with severe grade of cataract was taken in the study. For our convenience, the three grades of cataract were further divided into two groups. Group A consisted of 'Nomoderate cataract' with LOCS score ≤ 4 for Nuclear cataract (NS) and cor cal cataract and <2 for Posterior Subcapsular cataract (PSC). Group B consisted of 'Severe cataract' with LOCS score >4 for NS and cor cal and ≥ 2 for PSC. Socio-demographic risk factors included age, gender, occupa on and educa on. Educa on was categorized into four groups based on highest educa on level: No formal educa on, primary (grade 6 or less), secondary (grade 7-10), th 5 ter ary (11 grade or higher, including university educa on).
The biological risk factors included current history of smoking, self-reported history of diabetes mellitus and hypertension, family history of lens opaci es, use of drugs, frequency and amount of alcohol consump on, BMI, blood pressure and blood glucose level.
Smoking history was determined by whether the pa ents were current smokers or past smokers or non-smokers. Current smokers were defined as individuals who were currently smoking or had stopped smoking less than 1 year before examina on. Number of pack years was calculated as number of cigare es smoked per day x number of years 6 smoked/20 (1 pack has 20 cigare es). The par cipants were asked about all the medica ons (prescrip on and over-the-counter) that they were regularly taking. History of intake of drugs that increase the risk of cor cal cataract such as oral steroids, oral hypoglycemic agents, insulin, β-blockers, NSAIDS was recorded.
Frequency of alcohol consump on as daily, weekly, monthly, or less o en was recorded. For easier interpreta on, the total alcohol intake was recorded into number of drinks, assuming 1 drink contained 13 grams of alcohol, corresponding 7 to 330 ml of beer, 150 ml of wine, or 45 ml of liquor. Body mass index was graded into four grades: Underweight (<18.5), Normal (18.5-24.9), Overweight (25-29.9) and Obese (>30) Diabetes mellitus was defined as a RBS of 200 mg/dl, or higher or use of diabe c medica on or self-report of physician diagnosis. In our study random blood sugar was labeled as controlled (80-140 mg) and uncontrolled (>140 mg) The blood pressure of pa ents was recorded at the me of

RESULTS
Of the 400 eyes of 400 pa ents examined, the mean age of presenta on was 61.96 ± 9.07 years. The male to female ra o was 1  Most of the study pa ents were in the age group of 50-60 years among which Group A had 53.2% pa ents and group B, 57.3%. Figure 2 shows the distribu on of different types of cataract in the two groups among different age group. (Figure 2) Significant associa on was seen betweenolder age group andsevere form of nuclear sclerosis in group B (p <0.029).There was no significant associa on between There was no significant associa on between occupa on and occurrence of severe cataract in group B, p >0.659. Most of the pa ents in the study were found to be nonconsumers of alcohol (70%). There was no significant associa on found between prevalence of moderate cataract and alcohol consump on, p > 0.334. However, among group B pa ents, 32.9% consumed of alcohol with an average consump on of 2 glass (approx. 600 ml) /day. There was significant associa on between alcohol consump on and occurrence of PSC in group B with p<0.003( figure 4).An associa on between blood pressure, blood sugar and BMI among different types of age-related cataract in two groups is illustrated in the table 2. High blood pressure was not found significantlyassociated with moderate age-related cataract (p <0.062). However, Grade III hypertension ≥ 180/110

DISCUSSION
This was a hospital based cross sec onal study carried out to determine the underlying risk factors for different morphological types of age-related cataract. The risk factors were studied based on previous studies in different parts of the world and its prevalence was determined in our study group. Our target popula on mainly consisted of Nepalese popula on of eastern belt as well as from northeastern part of India across the borders with similar geographical and living condi ons. Among the significant characteris cs, increasing age was found to be significantly associated with moderate grade of PSC and mixed type of cataract. The findings were 9 consistent with previous studies. The prevalence being less in the age group of 80 years and above (4.2%) as compared to 50-60 years (53.2%) could be explained by increased awareness and early presenta on of people with age-related cataract due to visual disability and need for early interven on. In our study, age related cataract was seen slightly more in males (50.5%) than females (49.5%). It was not consistent 3 with the findings of previous studies. This possibly may be due to less exposure of females to poten al risk factors or due to social barriers for early presenta on among females in this part of the world as compared to males. Most of the pa ents in our study were engaged in household ac vi es among which moderate NS was more prevalent. Significant associa on was found between household ac vi es and prevalence of moderate grade of 10 NS (p <0.001). Leske et all described increased associa on of non-professional occupa on and low socio-economic status with increased incidence of nuclear and cor cal opaci es. The prevalence of age-related cataract in this study popula on was irrespec ve of current or past smoking 11 history inconsistent with the findings in previous studies.
The addi ve role of other puta ve risk factors could possibly be the cause. However, age related cataract has significant associa on with moderate consump on of alcohol (p<0.003).Lindblad 7 et al in their study noted that daily intake of ≥ 1 alcoholic drink was associated with a modest increase of risk for cataract extrac on. The risk increased with increasing alcohol consump on.
In this study the level of blood sugar was not seen to be significantly associated risk factor, possibly due to smaller 12 sample size. Unlike our study in a study done byTan et all showed significantly increased risk of high blood sugar level with incident cor cal cataract.
In the present study, high blood pressure was found to be significantly associated with increased incidence of severe NS and PSC. It was seen consistent with a study by Chris ne 13 Y et al in which sta s cally significant associa on was seen with high blood pressure and posterior subcapsular cataract. Age-related cataract is a major cause of blindness through out the world which needs be er understanding of its e opathogenesis and preven on. The study was primarily interview based and grading of lens based on photographic standards which can lead to observers bias during elabora on of risk factors and grading of severity of cataract.

CONCLUSION
Older age, household occupa on, alcohol consump on and high blood pressure were iden fied as risk factors for the development of different morphological types of agerelated cataract. This study creates room for a larger study with prospec ve analysis of risk factors and its associa on with age-related cataract that can help reduce the burden of avoidable blindness in our country.

RECOMMENDATIONS
Age-related cataract is a major cause of blindness throughout the world which needs be er understanding of its e o-pathogenesis and preven on. The higher prevalence of environmental and socio-economic risk factors in developing countries like ours, that pose a risk of early development of severe Age-related cataract needs special a en on. Efforts towards preven on and be er understanding of puta ve risk factors may help reduce the burden of visual disability due to age-related cataract.

LIMITATIONS OF THE STUDY
The sample size was small as compared to previous studies. Due to variable presenta on of pa ents from different regional areas, the sample was not a true representa on of eastern Nepal. The study was primarily interview based and grading of lens based on photographic standards which can lead to observers bias during elabora on of risk factors and grading of severity of cataract.