Is gender a risk factor for cataract ?

Commonly recognized clinical sub-types of cataract are nuclear, cortical and posterior subcapsular types (PSC). However, it is not very clear how these clinical sub-types correspond to distinct etiological entities. The current theories developed on cataract formation do not distinguish between the clinical sub-types . Surprisingly, many biochemical changes in the lens that cause cataract are also found in aging lenses with normal clarity 3 .


Introduction
Age related cataract is the major cause of low vision and blindness in the world today 1 with 17 million bilaterally blind in 1990 2 .
Commonly recognized clinical sub-types of cataract are nuclear, cortical and posterior subcapsular types (PSC).However, it is not very clear how these clinical sub-types correspond to distinct etiological entities.The current theories developed on cataract formation do not distinguish between the clinical sub-types 2 .Surprisingly, many biochemical changes in the lens that cause cataract are also found in aging lenses with normal clarity 3 .
Reactive oxidizing chemicals such as superoxide, hydrogen peroxide and hydroxyl radicals are toxic to biomolecules and are capable of producing cataract due to oxidative stress.The human lens possesses various defences against such oxidative damage that include small molecular anti-oxidants such as glutathione, vitamin C, vitamin E and enzymes such as catalase, glutathione peroxidase and superoxide dismutase.Repair systems of the lens remove damaged proteins 4 .All these systems become deteriorated under extreme oxidative stress or during aging process.Aging will ultimately result in certain biochemical changes in the lens that includes disulfide cross-Linkages which lead to insoluble high molecular weight aggregates 5 and peroxidation of membrane lipids.The oxidative damage to the lens epithelial cell DNA causes apoptosis 6 .In animal models the morphological appearance of oxidative cataract resembles both cortical and nuclear types 7 .Pathology of PSC cataract is quite different.It may be due to posterior migration of lens epithelial cells.An unknown factor is operating here to disrupt the cell to cell contact.Another mechanism put forward for cataract or genesis is the polyol pathway.Excess glucose are converted in the lens by aldose reductase to sorbitol.Sorbitol accumulations in the lens causes increased osmotic pressure causing cell damage that lead to opacification but clinical studies have shown a failure for aldose reductase inhibitors to prevent cataract in human lens 8 .It is also hypothesized that direct damage by ultraviolet A and B radiation may result in cataract 8 .Data collection on prevalence of cataract blindness is always subjected to misclassification bias 9 because a dense obvious age released cataract may not reveal a possibility of having glaucoma or macular damage or any other posterior segment pathology unless specific investigations are performed.Reported rates for the three most common sub-types of cataract have shown a great variability in age race and gender distribution in many studies performed in the west 10 .One way of finding the impact of cataract on the healthcare system is to measure the prevalence of surgical cataract extraction.This finding is dependent and influenced by the availability of surgical services and demand in a district or a country.But it provides an important and useful estimate of potential cataract burden in a population and different distributions 11 .

Objective
To find the impact of cataract on healthcare system by measuring the prevalence of surgical cataract extractions and its gender distribution as a risk factor.

Methodology
As mentioned in the introduction, the number of cataracts performed was used as a gauging system to find the impact of cataract on healthcare system in this study.Prevalence values and distribution of age and gender were analysed using available information.In Galle district the prime institution that performs cataract surgery is Karapitiya Teaching Hospital.Small number of cataract surgeries is being done at the private sector.Co-operative Hospital is one of the major institutions where cataract surgeries are being done at the private sector.Cataract surgeries performed over past 5 years period (2001-2006) in these two institutions were analyzed using data available from operation registers.Adjoining districts in Southern Province, i.e.Matara and Hambantota Hospitals were having functioning eye units with Eye Surgeons for this whole period.Patients who were admitted to Teaching Hospital Karapitiya from these areas for cataract surgeries were excluded from the study.For prevalence calculations data from census of population 2001 was used for males and females of Galle district in their relevant age categories.Data analysis was performed to find the prevalence values according to gender and age.

Findings
More than sixteen thousand entries on cataract surgeries over 5 year period starting from 2001 were analysed.90% of cataract surgeries of Galle District had been performed at the public sector institution.

Table 2 -Age and gender distribution of Cataract surgeries
A steady increase of cataract surgeries after the 3 rd decade of life is shown both in males and females.
The age group of 30-39 years showed the least prevalence and a sudden increase was seen after 50 years.

Discussion and Conclusion
The total prevalence for cataract surgeries among males and females is 3.2 / 1000 population and for males and females separately it was 2.7 and 3.7 / 1000 population showing a female preponderance.
The cataract surgery prevalence shown in table 3 almost exclusively relate to the District of Galle.The proportion of the population who have undergone cataract surgery has a marked increase in the decades after 40 yrs.Sudden increase of cataract surgical prevalence after 50 years is suggestive of the occurrence of cataract after 50 years is higher.Prevalence of cataract surgery is significantly lower in young age groups.Female gender has shown an increased age adjusted rate of cataract surgical prevalence in this study.
Statistical calculation using goodness of fit test shows a significant increase of cataract surgical prevalence among females than males (P = 0.05).Relative risk calculated using the cataract surgeries performed as incidence cases shows a relative risk of 1.36 among females compared to males in getting cataract.This is a significantly higher risk among females.(CI =

Table 3 -Prevalence* of any cataract** by age and gender
* Prevalence -per 1000 population / year ** Any type of cataract including cortical, nuclear or PSC 12,13anka i.e. 0.7%.This finding may suggest poor health-seeking behaviour among people with cataract and as a result there may be a backlog of cataract remaining in Galle District yet.It has been shown in Australian Blue Mountain Study12,13that females gender is generally associated with increased age adjusted risk of cataract and the findings of our study are also similar to the Australian Study.These findings are suggestive of gender as a risk factor for cataract and further studies to confirm this finding will be necessary.