Accommodation is really nothing more than the eye continually focusing and refocusing on the objects around you as you change position. The lens becomes flatter or rounder, longer or shorter, depending on the distance of the object in focus. Some people, however, have poor accommodation, meaning that the time between you moving and the refocusing on the eye is too long and vision can get blurry. A small lag is normal and not noticeable to the average person.

The main symptom of an accommodative anamoly is eye strain and blurred vision, though irritation, headache, and vertigo can also be signs of an accommodation problem.

Study is still being done, but accommodation seems to be a result of over-rigidity of the lens or weakened ciliary muscles, the muscles that cause the expansion and contraction of the lens. The causes of this condition remain hazy if it is a rigid lens that causes the problem, but usually a weakening of the ciliary muscles is a response to some other condition in the body that can vary from the flu to nasal obstruction to anemia or high blood pressure. To treat an accommodation anomaly it is best to treat the cause; glasses for eye strain or removal of nasal obstructions if there are any, and so on. Most people, regardless of the cause of their problem, will receive reading glasses, and some will also be given the option of doing reading exercises.

Everything we see is a result of the projection of light onto the retina, a thin piece of tissue at the back of the eye. It converts the light into signals interpreted by the brain as images. All of the other parts of the eye work together so that the light is focused correctly, ensuring that the image sent to the brain is accurate. Vision problems occur when any of these important parts are damaged or not operating normally. It is therefore easiest to discuss those problems when you can compare them with a normal eye and see what part of the chain of the events has broken down. Here we will watch the way light journeys through the various components of the eye to its destination: the retina.

When light enters the eye, the first thing it encounters is the cornea, a clear film of five layers of tissue. Transparency is the most crucial quality of the cornea, and so it has no blood vessels—all of the necessary nutrients are diffused through fluids on either the inside or the outside of the cornea and through a transparent protective cover called the conjunctiva. The cornea’s two main functions are to protect the eye from toxins and particles that could damage the eye and to act as the primary window for light entering the eye, reflecting and focusing the light onto the lens, light’s next stop in its journey.

Between the cornea and the lens, however, it is important to mention the iris and the pupil. The iris is the colored part of the eye, and the pupil is actually just a small hole in the iris, even though it appears to be black. Light reflected from the cornea passes through the pupil and onto the lens, and the iris controls just how much of that light is allowed through. In bright areas the pupil does not need to be very large for clear vision, while in darkness the pupil will dilate (become larger) to optimize the amount of light that can get back to the lens and the retina. To see this happening in real time, just spend a few minutes outside on a sunny day and then walk inside and look in a mirror. A few seconds after coming inside your pupil will be small, but given some time to assimilate it will adjust to the darker room and expand.

The light that passes through the pupil is reflected onto the lens next. Much like a camera lens, both the cornea and the lens have the job of correctly focusing the light so that the image projected onto the retina is as clear as possible. The lens is transparent and fibrous and controlled by tiny muscles that flatten or accommodate it depending on whether or not the eye is focusing on something that is far or near. The change in the shape of the lens also affects the size of the pupil, which gets larger when the lens is flat and focusing on something far away and gets smaller when light is reflecting off an object that is close and the lens is more convex. The pupil therefore effectively has an infinite number of shapes, as it is affected by the amount of light entering the eye and the distance away from the object in focus.

Once the light has been processed by the lens it is then bent and reflected as an upside-down image onto a single point on the last of the ten layers of the retina. This, however, is not quite the end of the journey, because from that layer the image is then projected onto the ninth layer, the photoreceptor layer. This is the part of the retina that is able to interpret the image that up until now has just been passed through and processed by the other parts of the eye. There are two categories of photoreceptors, rods and cones, and it is they that compress the image into a message that is sent through the optic nerve to the brain, where finally the inverted image becomes the right-side-up one that you see.

The process of vision is very complex and requires that every participant function exactly as it was intended, because any alteration, however slight, can result in impaired vision. It is no wonder, therefore, that vision problems are so common and so varied, or that there are people who spend their careers devoted to solving them!

Color blindness is not connected to vision loss; it is merely a description of the way that some people see the world around them. Those with color blindness most often have trouble distinguishing between reds and greens, though there is a very small percentage of the population that has a deficiency in seeing yellows and blues.

The condition is caused by defective cones in the retina. The cones are what normally respond to light and detect and transmit color, and there are three types. Most commonly the red-green cones will transmit at a diminished frequency, which results in those affected detecting lesser amounts of red in the world around them.

Color blindness is a hereditary condition found on a gene on the X-chromosome and it is a recessive trait. Because males only have one X-chromosome, if the gene is given to them they will be color deficient. Females, on the other hand, are only colorblind if both of their X-chromosomes contain the colorblind gene. Consequently most of the colorblind population is male. Many women can be carriers of the gene, however, and not exhibit any deficiency, and it is through them that the condition is passed. If you are a male and are colorblind then your mother is a carrier; any brothers you have must also be color blind, while a sister could be a carrier or not have the gene at all. For a woman to be colorblind her father must also have the deficiency and her mother must be a carrier or also color blind; this is why the condition is rare in females.

Color blindness can be overcome mostly with an awareness of the condition; knowing you may not see the world the way everybody else does means you may have to make slight adjustments in how you organize your closet or recognize the lights on the traffic light, but those are skills easily learned. It is important, however, to become aware of the condition early enough to be able to alert schoolteachers so they may work with the child’s slightly different perspective. Having colorblindness does not put you at risk for other eye conditions.

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Color Blindness

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