Myopia is eyesight abnormality when a person can see clearly only nearby objects while distant objects appearblurred. Unfortunately, shortsightedness is widespread, both children and adults might have this abnormality.
What is myopia about?
Myopia (shortsightedness) is a very widespread disease affecting both children and adults. According to the World Health Organization information, 800 million people on our planet suffer from shortsightedness.
Quite often our eye is compared with a photo camera. The eye cornea and lens act as camera lens: they pass through and refract the light rays entering the eye. Retina acts as photosensitive film: an image appears on it due to photosensitive cells. Then the image transforms into nerve impulses and is transmitted to the brain through the optic nerve as if through wires. The image will be clear if the cornea and lens reflect the light rays in the way that the focus (the rays intersection point) to be on the retina. For this very reason healthy people are able to see objects clearly in the distance.
For myopic people, light rays are focused in front of the retina, and the image appears blurred. This occurs on two reasons:
- The cornea and lens refracts the light rays too much.
- Eye extends too much during its growth process, and retina moves away from the normally located focus. Normal eye length for adults is 23-24 millimeters, and myopic eye length is 30 millimeters and more. Eye extension by 1 millimeter results in shortsightedness increase by 3 diopters.
There are many causes of myopia, but the doctors consider the most important ones as follows:
- Excessive eye work at nearby distance from the object (with no rest for eyes and with bad lightning).
- Inherited predisposition to myopia, which is manifested in the peculiar features of the eyeball structure and its metabolism.
-Weakened sclera producing no proper resistance to the eye excessive growth.
- Not sufficiently developed accommodative muscle of the eye which is responsible for adjusting the lens to different distances; overstrain of the weakened muscle can lead to myopia as well.
As a rule, myopia develops in the childhood and becomes noticeable during the first school years. Children see distant objects blurred and have problems in distinguishing letters and figures written on the blackboard. They try to accommodate themselves closer to a TV set on to sit in the front rows in a movie theater. Myopic people often screw up their eyes when looking at distant objects.
In addition to deteriorating eyesight into the distance, myopic people have eyesight problems in the twilight: such people have vision problems on the street, it is hard for them to drive at this time.
To improve vision, myopic people have to wear contact lenses or spectacles with minus diopters. They quite often have to replace ocular glasses and lenses because of eyesight deterioration. However, one should know that spectacles are unable to stop myopia progression, they only correct the light refraction. If eyesight deteriorates, and one has to replace spectacles with stronger ones, this means myopia progression. Occurring because of the eyeball increasing extension.
Progressive myopia is not a harmless eyesight defect eliminated by means of glasses, but a disease with serious consequences.
Children, more frequently the ones aged from 7 to 15, suffer from progressive myopia. Eyeball extension leads to extending vessels being inside the eye, to retina malnutrition, and visual acuity deteriorates. Retina, like a delicate veil being strained, is being torn gradually in some regions, small holes appear in it, and it may result in retinal detachment. This is the worst complication of myopia when eyesight is lost significantly, up to absolute blindness.
Only a specialist is able to determine the degree of your myopia and select the treatment method being most appropriate for this case.
In hypermetropia, or farsightedness, the rays emanated from extremely distant objects, are focused beyond the retina, this may be caused by the weak optic system refraction or by not sufficiently extended eye.
Hypermetropia of weak degree can be compensated by accommodation strain, that is by increasing the eye lens refractive force. This is the case of hidden hypermetropia.
Refraction abnormality – astigmatism. Normal cornea has spherical form, that is its refractive force is the same both on vertical and on horizontal levels. In Astigmatism, the cornea refractive force on these levels is different. For example, in the vertical position the cornea refracts stronger than in the horizontal position.
You already know that the eye lens is a transparent lens. Sometimes it turns opaque. Cataract is the disease causing the eye lens opacity.
Changing the eye lens transparency prevents the light rays penetrating the eye, and the person’s vision deteriorates. Cataract can affect the whole eye lens or its part.
Many people think that cataract is a film which constantly grows and clouds the eye. This does not correspond to the facts. Cataract causes irreversible changes in the very eye lens. This disease may arise in one or two eyes, but it is not passed from one eye to another. Cataract development is not related to the excessive eye load. Cataract does not mean a danger of becoming absolutely blind for you.
The Causes of Cataract Development.
There is a variety of causes for cataract development: trauma, the eye tissues nutrition disorder related to age, ray affection, diabetes, some eye diseases (such as glaucoma) or your organism peculiarities of hereditary character.
More frequently cataract appears during the organism aging process which causes the eye lens density increase and the lens opacity. This is aging or senile cataract. It can arise at the age of 45 already. Cataract can develop in the childhood as well, in this case it is called congenital cataract.
After eye trauma occurs, the lens can become opaque at any age. Strong blow, cut, puncture, thermal or chemical burn may result in traumatic cataract appearing.
One more cataract is diabetic cataract arising as diabetes complication. It is marked by fast opacity development in the both eyes lenses.
Depending on the size and location of the opaque region in the eye lens, you may notice or, on the contrary, have no idea that you have cataract developing.
If cataract is located on the eye lens periphery, you will fell no changes in your eyesight. The closer to the lens center the opacity is, the more serious vision problems become.
You may notice that the outward objects are not seen clearly, their contours are blurred, especially in the bright light. The image appears double, and photophobia occurs frequently. One eye may have better eyesight than another. The eye pupil which usually looks black, may turn white or become of yellow shade.
These phenomena are increasing and make you frequently replace your spectacles to stronger ones.
Taking doctor’s advice is strongly recommended! Only specialists is able to determine if you have cataract or not.
The wide spreading of glaucoma, the disease early diagnosis difficulties and serious prognosis are the reasons of constantly increased attention the scientists and practice doctors have to this disease. This eye disease is the second most frequent cause of incurable blindness.
What is Glaucoma about
Glaucoma is the eye chronic disease in which the intraocular pressure raises and the optic nerve is affected. The vision deteriorates up to absolute blindness. The blindness caused by glaucoma is of irreversible nature because the optic nerve is destroyed. In this case, returning vision to the patient is already impossible!
Unfortunately, glaucoma is a rather widespread disease. More frequently it affects people aged over 40, but it can affect young people as well (adolescent glaucoma) or even newborn babies (congenital glaucoma).
The normal intraocular pressure figures are individual for every person, but on average they are within the range of 16-25 millimeters of mercury column when measured by Maklakov tonometer. The constancy of intraocular pressure is determined by the balance of the liquid produced inside the eye and the liquid flowing out of the eye.
Therefore, the eye liquid retention results in intraocular pressure increase, and high intraocular pressure destroys the optic nerve.
Hereditary factors play critical role in glaucoma arising.
If your relatives had glaucoma, you should be especially careful and undergo regular ophthalmologist examinations. The examination and intraocular pressure measurement minimum once a year will allow to reveal the disease and to treat it efficiently.
Glaucoma Symptoms and Forms
There are three main features of glaucoma:
- Intraocular pressure increase.
- Eyesight area narrowing.
- Optic nerve changing.
For timely glaucoma revealing, it is important to know its symptoms and the patient’s feelings.
The following symptoms may point to intraocular pressure increase:
- Eyesight blurs, net appears in front of the eyes.
- Iridescent rounds appear when looking at the light source (for example, at the lighting bulb).
- Feeling of discomfort in the eye, feeling of heaviness and strain.
- Slight colic in the eye.
- Feeling of eye moistening.
- Deterioration of vision in the twilight.
- Slight pain around the eyes.
Glaucoma is not an infectious disease. As a rule, it arises in two eyes, but not simultaneously. In the second eye it can be revealed only several months or years later.
Only a specialist is able to determine if you have glaucoma and in which form.