Clear Vision – Refractometer Applications for Ophthalmology

The refractive index is the key factor in the correction of defective vision. Meanwhile, ametropia effects close to 50% of the world wide population. Especially the increases of display work stations, excessive use of smartphones, and aging population have played an important influence. Luckily, modern high-tech polymers allow even higher refractive indexes and therefore significant thinner glasses and contact lenses.

1 Introduction

1.1 Human Eye

The human eye is a miracle of nature. Photo receptors allow the human being to perceive light stimulation and color in the spectral range from 400nm to 700nm of the electromagnetic Waves. Especially the sharpness of vision highly depends on the precise projection of the light beam on the retina. The filigree interaction between lens, corneal, and eye fluid make this possible. Changes in the focal point will directly lead to blurred images. We know this as nearsightedness, when the focal point is in front of the retina, and farsightedness, when the focal point is behind the retina. Especially changes in the lens or the corneal will lead to optical aberration. This lens is not a stiff object. It can be bent by muscles. During aging the lens will lose its bending properties. This will lead to problems in the reading area.

Most important parameter is the refractive index, which mainly influences the light directions angle after passing materials e.g. the corneal or human lens. Minimal changes in the refractive index can lead to vision valves, caused by less liquid or different salt concentration. In the following chapters you will learn more about the importance of the refractive index for vision correction and its quality control.

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