Teachable moment in classrooms:
- tissue chapter – characteristics and locations of smooth muscle
- special senses chapter – structures inside the eyeball
- special senses chapter – location of the iris and the action of smooth muscle to change pupil diameter
The news item: Recently, the following report appeared online:
Independence woman regains sight after first-of-its-kind surgery in Missouri
In 2010, Jennifer Sanders suffered an orbital globe rupture which destroyed 95% of the iris in her right eye.
The article states that a woman whose eye ruptured in an accident suffered from poor vision and light sensitivity because of a destroyed iris. An artificial iris implanted into her eye resulted in much improved vision.
So, Why Do I Care?? In addition to trauma-caused damage of the iris, about 1% of cataract surgeries damage the iris, and there is a developmental disorder called aniridia that results in the underdevelopment of the iris. Thus, there are tens of thousands of people who suffer from the absence or malfunctioning of the iris. Poor vision affects the ability to learn in school, to get a job, to drive a car, among other things, so it is important to seek out solutions for these conditions.
Plain English, Please!!! First, let’s talk about the location and function of the iris. The iris is a flat, thin ring inside the eye. For the shape just think about a donut that somebody sat on. The forward-looking surface of the “flattened donut” is the visible, colored part of the iris; this gives us the color of the eye. The backward-looking surface of the iris is made up of a thin layer of smooth muscle. The circle-shaped opening in the “flattened donut” is the pupil where light passes through towards the deeper portion of the eye. Because of the action of the smooth muscle, the pupil can be made wider or narrower. A narrow pupil prevents large amount of light entering the eye as that light would overload the photoreceptors in the retina. A wide pupil allows more light into the eye in a dim environment, so the photoreceptors can receive enough light for producing visual experience.
Second, let’s talk about the implant itself. The implant is made of silicone, and shaped like the biological iris. It is placed into its normal location, immediately in front of the lens. Because silicone doesn’t