Cataract Treatment, Research Paper Example

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Words: 1210

Research Paper

Introduction

Cataract refers to a condition shown by clouding of eye lenses. People over the age of 40 have cataracts as the major cause of vision loss. Cataract is also the world’s leading cause of blindness. Age-related decrease in accommodative amplitude begins expressing symptomatically at around 45 years of age. Accommodation refers to the process of the vertebrate eye changing optical power to ensure focus of a clear image as the distance of an object varies. According to health experts, the condition is presbyopia. Factors responsible for presbyopia include aging of the ciliary muscle, lens hardening, growth of the lens during aging, aging of the choroid, or loss of elasticity of the lens capsule (Sharma et al, 2011). Restoring accommodation is possible by replacement of the lens substance using a soft material suitable for the purpose. Fixed focal length lenses contribute to clear visualization of objects and thus providential pictures. These types of lenses are also easy to carry. A surgery to refill the lens involves removing the cortex and lens nucleus via a small capsular shaped opening, and then followed by injecting polymer that refills the capsular bag. In America, the prevalence of cataract is extremely high especially at age 80 (Friedman et al, 2009). About half of Americans at age 80 have suffered from cataract or underwent cataract surgery. At present 22 million Americans who have 40 years and above suffer from cataracts. Cataract cannot spread from one eye to another eye, but it can affect both or either eyes. Most cataracts are due to aging, but other types can affect people. These include secondary cataract, congenital, traumatic cataract and radiation cataract.

The eye lenses have viscoelastic nature and any change in the proportion affects accommodation capability. The measurement of viscoelastic properties of the eye lens is possible through atomic force microscopy and dynamic mechanical analysis (Nishi et al, 2009). In these two ways, obtained values are similar. During accommodation, the lens takes the shape determined by the lens capsule. Diminished tension on the capsule enables it to overcome the lens contents stiffness when the zonules relax. In the refilling of the lens affected by cataract, fibrosis is a problem that has always led to unsuccessful efforts of the medics. In a study conducted on monkeys, researchers reported capsular opacification development (Koopmans et al, 2006). They also reported postoperative inflammation that caused media opacities in monkeys and made the measurement of refraction impossible for some. The aim of this study is to study the effects of polymer materials on the lens. Consequently, the study will strive to depict how fibrosis affects the lens accommodation, stiffness, relaxation, viscoelastic properties, and responses to pressure.

Discussion

During lens refilling, injection materials should have enough fluids for smooth injection and to reduce leakage risk they should be viscous enough. This study entailed the use of twelve pig lenses divided into three. We had freshly extracted lenses, freshly refilled lenses and those prior refilled and showed fibrosis. In the study, we applied compressive load by applying 10% pressure on the lenses. We then measured the relaxation response force for a hundred seconds and recorded the results of stiffness and relaxation.

Refilled lenses did not show significant changes in the lenses thickness. Lenses that were natural showed the highest levels of percentage relaxation and stiffness. The refilled lenses also had significantly lower levels of percentage relaxation and stiffness including a tendency to deformation under exposure to changes in pressure. Investigators have met several issues in the venture to refill eye lenses affected by cataracts. Injectable materials could leak from the anterior opening of the capsule through which the matter of the lens came. After-cataract, either in the form of regeneratory or fibrotic capsule opacification is another problem associated with refilling. A third problem involves refractive power titration to achieve accommodation that is effective as well as emmetropia. The lens elasticity of the capsule of the lens has an effect, which is negligible in molding the lens material. As long as the contents of the lens have proper properties of viscoelasticity, accommodation can take place successfully. Koopmans et al, 2006), stated noted a change in the accommodative amplitude of refilled lenses while studying the rhesus monkeys. He cited many factors including lose of adhesion between the natural lens and the lens capsule. A reduced adhesion could lead to inefficient capsular forces transmission, which mold the contents of the lens during accommodation. Intracapsular accommodation is another cause of reduced accommodative amplitude in a refilled lens.

Lenses kept at 37 degrees Celsius showed the development of fibrosis on the anterior side. Fibrotic after-cataract may adversely affect the accommodative function because of elasticity decrease of the capsule. In addition, it may be impossible to treat regeneratory after-cataract due to a leakage risk of the refilling material leaking into the posterior region. A decrease in elastic properties due to fibrotic effects leads to a decreased accommodative amplitude.

For a successful outcome after lens refilling, capsule elasticity and transparency are mandatory (Sharmaet al, 2011). The lens epithelial cells proliferation following a cataract surgery causes after-cataract in two ways. These two ways include regenerative after-cataract and fibrotic. Fibrotic after-cataract occurs because of capsule elasticity loss due to myofibroblasts laying down the collagen while regenerative after-cataract is due to Elschnig that causes inhomogeneities. Fibrotic after-cataract rarely causes clinical problems in modern cataract surgery. Treatment of regenerative after-cataract is possible using neodymium. The study shows that further experiments on animals with viscoelastic properties like those of man could lead to discovery of crucial approaches for the treatment of cataract.

Conclusions

The effect due to fibrosis on the viscoelastic properties of the eye lenses has an influence on relaxation and stiffness, which in turn affect accommodation. Despite the challenges that still, exist for cataract surgery, the study shows that there is a remedy for the many problems associated with cataract surgery. Lose of viscoelastic properties makes the lens easily affected by pressure changes. The use of the animal (pig) lenses is an attempt to show possible effects of the various treatments on the human eye lenses in pursuit to provide a remedy for after-cataract effects. The stiffness of the eye lenses increase with the individual’s age. The change in the gradient of stiffness influences the amplitude of accommodation. Animal experiments using lens refilling have shown that lens shape changes are attainable in the early postoperative period even though the accommodative process remains not fully understood. This brief study along with others done show that refilled lens could have some reasonable optical qualities and thus the hope of cataract treatment, which still faces challenges of post surgery. Future research should strive to find out the mechanism for presbyopia and the human ocular accommodation.

References

Friedman, D. S., Congdon, N., Kempen, J., & Tielsch, J. M. (2002). Vision problems in the U.S.: prevalence of adult vision impairment and age-related eye disease in America. National Eye Institute, Bethesda, MD; and Prevent Blindness America, Schaumburg, IL.

Koopmans A. S. et al. (2006). Accommodative Lens Refilling in Rhesus Monkeys. Journal of Opthalmology: National Institute of Health, Vis Sci.; 47(7): 2976-2984.doi: 10.1167/iovs.05-1346.

Nishi, Y. et al. (2009). Lens refilling to restore accommodation. J Cataract Refract Surg 2009;35:374-382

Sharma, P.K. et al. (2011). A comparative study on the viscoelastic properties of human and animal lenses. Journal of Experimental Eye Research, Vol 93, Number 5

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