Uncorrected near-sightedness is one of the most common causes of vision impairment globally along with cataracts, macular degeneration, and vitamin A deficiency. Etymology
The term myopia is of Koine Greek origin: μυωπία myōpia (or μυωπίασις myōpiasis) "short-sight(-ness)", from Ancient Greek μύωψ myōps "short-sighted (man), (man) with eyes getting shut", from μύειν myein "to shut the eyes" and ὤψ ōps "eye, look, sight" (GEN ὠπός ōpos). The opposite of myopia in English is hyperopia (long-sightedness). Signs and symptoms
A myopic individual can see clearly out to a certain distance (the far point of the eye), but objects placed beyond this distance appear blurred. If the extent of the myopia is great enough, even standard reading distances can be affected. Upon routine examination of the eyes, the vast majority of myopic eyes appear structurally identical to nonmyopic eyes.Onset is often in school children, with worsening between the ages of 8 and 15. Causes
The underlying cause is believed to be a combination of genetic and environmental factors. Risk factors include doing work that involves focusing on close objects, greater time spent indoors, urbanization, and a family history of the condition. It is also associated with a high socioeconomic class and higher level of education.A 2012 review could not find strong evidence for any single cause, although many theories have been discredited. Twin studies indicate that at least some genetic factors are involved.
Signs and symptoms
STK typically occurs in the buccal sulcus (inside the cheek) or the labial sulcus (between the lips and the teeth) and corresponds to the site where the tobacco is held in the mouth. It is painless.The appearance of the lesion is variable depending upon the type of tobacco used, and the frequency and duration of use. It takes about 1-5 years of smokeless tobacco use for the lesion to appear. Early lesions may appear as thin, translucent and granular or wrinkled mucosa. The later lesion may appear thicker, more opaquely white and hyperkeratotic with fissures and folds. Oral snuff causes more pronounced changes in the oral mucosa than tobacco chewing. Snuff dipping is associated more with verrucous keratosis.As well as the white changes of the oral mucosa, there may be gingival recession (receding gums) and staining of tooth roots in the area where the tobacco is held. Diagnosis
Diagnosis is mainly clinical, based on the history and clinical appearance. The differential diagnosis includes other oral white lesions such as Leukoplakia, squamous cell carcinoma, oral candidiasis, lichen planus, white sponge nevus and contact stomatitis. In contrast to pseudomembraneous candidiasis, this white patch cannot be wiped off. Tissue biopsy is sometimes carried out to rule out other lesions, although biopsy is not routinely carried out for this condition. Treatment
Apart from stopping the habit, no other treatment is indicated. Long term follow-up is usually carried out.