Too strong dioptre correction in early ages could lead to accommodation difficulties and shifting from nearsightedness (myopia) to farsightedness (hyperopia).
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An interesting recent research showed that more people are worried about losing their sight than losing their memory and the ability to hear. And they are concerned with a reason. Our eyes are the first source that supplies our brain with information where are we and what are we looking at.
Our brain interprets what is sent to it from our eyes and then we "see". But they are eye diseases that cause damage and even blindness if they are not detected soon enough, and also visual conditions related to the distance when looking at objects.
Those are myopia (nearsightedness or shortsightedness) and hyperopia (farsightedness, longsightedness or hypermetropia).
There are three factors that determine focus of the eye: cornea, lens and the length of the eyeball. Cornea, the transparent front part of the eye, contributes the most of the eye's focusing power although its focus is fixed. Together with the lens, the cornea refracts 70-80% of light to be focused on retina (a multi-layered sensory tissue that lines the back of the eye).
The length of the eyeball is also important for focus. If the eyeball is too long or the cornea is too curved, therefore too powerful, the light entering the eye falls in front of the retina resulting in myopia (close objects are seen clearly, but objects farther away appear blurred).
If the eyeball is too short or the cornea has too little curvature, light rays focus behind the retina resulting hyperopia (distant objects are seen clearly but close ones don't come into proper focus).
Myopia (nearsightedness) that develops in childhood is often called juvenile onset myopia. Parents are usually the first to notice that something is wrong with the sight of their child.
The child holds books very close while reading and needs to sit very close to the television or blackboard, rubbing her/his eyes frequently, often complaining about a headache. In many cases, myopia stabilizes when the growth process is completed and glasses can offer normal vision.
However, higher levels of myopia tend to be hereditary. If one parent is myopic, the child has 30 percent chance to develop myopia. The child whose both parents are myopic has 50 percent chance to develop nearsightedness. The development of disease is also environmental influenced (watching at the computer screen).
Myopia can be benign or malignant and develop gradually or rapidly often worsening during childhood and adolescence. After performing a series of eye tests that are different for preschool children from those for adults and, depending on the degree of nearsightedness, the eyeglasses will be prescribed.
Too strong dioptre correction in early ages could lead to accommodation difficulties and shifting to farsightedness.
Degenerative (malignant) myopia is rare. The dioptre increases suddenly and it is followed by gradual or sudden appearance of degenerative changes in the retina, choroid (the vascular layer of the eye), vitreous (a thick, transparent substance that fills the centre of the eye), sclera (the white or white of the eye) and the optic nerve. This form of myopia gets progressively worse over time.
Patients with degenerative myopia typically complain about headaches, decreased vision and sensitivity to light. If retinal degeneration or detachment is present, patients may also report light flashes and floaters which are associated with retina changes. Those with degenerative myopia have an increased incidence of cataract formation.
Much like gray hair and wrinkles, hyperopia (foresight) is a symptom of aging (presbyopia) but also, just like myopia, it is a hereditary condition. The ability of accommodation to near objects decreases with age and, usually, first symptoms appear around 40-50 years of age.
The first symptoms include: the inability to read small print especially in low light; eye fatigue and/or headaches during prolonged reading; blurred vision while focusing on near object; aching or burning eyes and irritability or nervousness after sustained concentration.
Common vision screenings, often done in schools, are generally ineffective in detecting farsightedness and visiting an ophthalmologist is the only right way in detecting the condition. In general, a person with hyperopia can often go years without experiencing any symptoms of foresight.
However, a child with severe farsightedness may have "crossed" eyes (strabismus) and is in higher risk to develop amblyopia (lazy eye), have a lack of interest in reading and difficulties while reading, rub her/his eyes often and complain about frequent headaches.
Eyeglasses are usually the first option at a young age. The next step in correcting the amount of light entering eyes, just like in case of myopia, are corrective lenses or reshaping of the cornea through surgical and non-surgical methods. ■