A Pattern of Age-related Macular Degeneration

Results: AMD was observed in 5.2% out of 402 subjects of 40 years and above age group with prevalence increasing with age. The prevalence of AMD was 0.7% within 40-50 years of age-group individuals increasing to 2.6% in 51-60 years, 6.5% in 61-70 years and to 19.3% among subjects above 71 years. This study revealed that the prevalence of AMD in females was higher with female preponderance in ratio of 2.5:1. 52.5 % AMD subjects in our study had visual impairment with 6/246/60 vision and 15% had vision <3/60-PL. Our study revealed statistically signifi cant increased risk for AMD with aging (p=0.00). Increased risk was observed in female gender and diabetics though the Odds ratio (OR) was statistically insignifi cant (p=>0.01).


INTRODUCTION
AMD is the leading cause of blindness in patients above the age of 50 years in developed countries. 1It accounts for 13% of all cases of legal blindness in the USA with more than 200 000 new cases reported each year. 1 The pathogenesis of this disorder is poorly understood.[4] The age related eye disease study recommends the use of multivitamins or antioxidants to reduce risk of advanced AMD. 5 Age is the most important risk factor for the development of the disease.Approximately 10% of patients aged 66-74 years will have AMD.The prevalence increases to 30% in the age group 75-85 Pokharel et al.2][3][4][5][6][7][8] This study aims to fi nd out the pattern of AMD in our context.

METHODS
A hospital based cross-sectional study in the department of Kathmandu Medical College Teaching Hospital from July, 2007-December, 2007.Ethical approval and patient consent was taken.The sampling method was randomized sampling with the participants age 40 years and above.Informed verbal consent was taken from all the study subjects.Detailed history of all cases was taken.All selected individuals were subjected to systemic examination and detailed ocular examination with dilated pupils.The individuals 40 years and above with no history of optic nerve diseases, glaucoma, active intraocular infl ammation, corneal scarring, and corneal diseases were included.But age less than 40 years, cases who refused to be a part of the study and with history of optic nerve diseases, glaucoma, active intraocular infl ammation, corneal scarring, and corneal diseases were excluded.
Diagnostic criteria for AMD were presence of hard or amorphous or calcifi ed drusens in the macula, small or large with hyperpigmentation or hypopigmentation of retinal pigment epithelium with loss of vision ≥ 6/12 with Amsler grid defect or Amsler grid blurring vision; Presence of choroidal neovascularization and macular exudates; Presence of macular disciform scarring; Cases with AMD or drusen were included in the study even with presence of the condition in one eye only; Cases with no clear view of fundus in one eye but presence of the above mentioned conditions in the other eye were also included for analysis as presence of AMD or drusen.
Statistical analysis of study subjects was done using statistical package for social sciences (SPSS) version 13 for windows.Chi-square test, correlation and logistic regression tests were analyzed.
Out of 804 eyes in this study, 5% had AMD.Out of 402 right eyes, AMD was found in 4.7% and out of 402 left eyes it was present in 5.2% (Table 1).Out of 21 AMD cases, 76.2% were females in our study and 23.8% males (Table 3).Within female gender, 7% had AMD while only 2.9% of total male study individuals had AMD.Our study reveals prevalence differences in male and female gender with higher prevalence in females.The prevalence of AMD was found to be 2.5 times higher in females than in males (OR: 1.122 with 95% confi dence interval lower 0.098; upper 1.081; p=0.068).However this female-male distribution was found to be statistically insignifi cant.

DISCUSSION
The prevalence of AMD varies from 1.2% to 29.3% world-wide.2] Another study from North India reports the prevalence rate to be 4.7%. 13In China the incidence in an observational series was 5.88%. 14The overall AMD prevalence rate in right eyes was 4.1 percent in the Funagata study in Japan. 15e prevalence of AMD observed in our study was 5% out of 804 eyes.AMD prevalence was 0.7% in 40-50 years of age-group individuals, increasing to 2.6% in 51-60 years, 6.5% in 61-70 years and to 19.3% among subjects above 71 years.There is no population-based AMD study carried out in our country for comparison.However, the prevalence of AMD observed in various retina clinics in Nepal was found to range from 4% -8.4%.
In US, the prevalence of AMD increased dramatically with age, with more than 15% of the white women older than 80 years. 4e comparison reveals very similar pattern of the agewise trend with AMD prevalence in our study too with rise of the prevalence as the age increases though the study number was lower to determine exact prevalence rate when compared with other studies.
AMD were observed to be more prevalent in female gender (7%) in our study with female: male ratio of 2.5:1 (OR 1.122).In the Beaver Dam Eye Study, women 75 years or older had seven times the incidence of late AMD as compared to men. 6 Prevalence of late AMD in men was 1.1 percent in Funagata study in Japan and 0.3% in women.2] The female gender prevalence of AMD fi nding was similar in our study with higher number AMD in females with increasing age.Role of hormones, estrogen defi ciency have been implicated for this gender prevalence in women but the results are inconsistent in different studies. 1,6The other reasons could be due to long life expectancy and obesity in females.However, in Asian population study done in Japan and China higher prevalence was seen in male population. 16% of AMD in our study was atrophic form and 5% exudative form.In a study by Jennifer, prevalence rate for atrophic form was found to be 85% in people with age related macular degeneration.End stage age related macular degeneration was found in about 1.7% of all people aged over 50, and incidence rising with age (0.7-1.4% in people aged 65-75, 11.0-18.5% in people .The age-wise trend of exudative AMD in our study could not be compared with other studies because there were only two wet AMD cases.In our study, the visual impairment due to AMD was found to be 52.5 % and 15 % were blind.In US, AMD accounts for 13% legal blindness. 4ing showed statistically signifi cant increased risk for AMD (p=0.00) in our study.Female gender and diabetes were also observed as increased risk for AMD though they were statistically insignifi cant (p=>0.01).Alcohol intake, hypertension, smoking, and nonvegetarian status revealed no risk for AMD in our study (p=>0.01).However, in other preexisting studies 1,6,8,17 statistically signifi cant increased risk for AMD was found with increasing age, in female gender, hypertension, diabetes, alcohol users and smokers.Howsoever, in some studies, risk factors like diabetes, hypertension and alcohol use were found to be statistically insignifi cant association for the development of AMD.Our fi ndings in this study regarding risk factors could be due to small study group or might be due to missing out of risk factors as we depended solely on history to rule out presence of those risk factors.
Further study with large scale population is required in Nepal to confi rm the exact incidence rate, prevalence rate, distribution age-wise, distribution sex-wise and risk factors for AMD.

CONCLUSIONS
The prevalence of AMD is 5% with female preponderance in ratio of 2.5:1.The increasing age showed statistically signifi cant increased risk for its development.Female gender and diabetes were also observed as increased risk for it though they were statistically insignifi cant.Further studies are needed in large scale population to confi rm the incidence rate, prevalence rate and associated risk factors in our population precisely.

Table 1 . Distribution of AMD AMD
The drusen formation was observed in 18.5% in 804 eyes.Out of 402 individuals, drusen were found in 10% of the individuals in the age group 40-50 years which increased to 36.3% in 60-70 years.