The first goal of vision screening is to identify children who have or are at risk of developing amblyopia; this problem can lead to permanent visual impairment unless it is treated during early childhood. Important pathologies to be screened include strabismus, cataracts, glaucoma, ptosis, refractive errors such as myopia, hyperopia and astigmatism, as well as other serious diseases like tumors or neurological diseases.
Amblyopia is a decrease in visual function in one or both eyes due to an abnormal ability of the visual pathway during childhood. Amblyopia does not necessarily imply an obvious problem in the eye. Vision loss occurs when neural pathways between the eye and the brain are not properly stimulated during recommended age.
To enable a sharp vision, light rays from an object placed in the visual field must converge to a single point of retina. The eye works like a camera – it has an opening in the front part (pupil), a focus mechanism (cornea and eye lens) and a light-sensitive portion in the back part (retina). Eyes affected by significant refractive errors such as myopia, hyperopia and astigmatism are not capable of focusing light in the intended retinal region.
Strabismus is associated to any kind of eye misalignment. There are many different types of strabismus and they are usually described according to the direction of the deviation. The most common types are endotropia (convergent deviation), esotropia (divergent deviation) and hyperopia (vertical deviation). Special strabismus patterns can have unique names, such as Brown syndrome and Duane syndrome.
Conjunctivitis is a condition in which eyes look red and may produce discharges. Symptoms change from burning, itching, foreign body feeling, discharge or crust formation on eyelashes. Bacteria, virus, other infectious agents, chemical products or allergies may cause conjunctivitis.
Mydriatics contain medication to dilate (increase the diameter) an eye’s pupil. There are two types of eye drops: one stimulates muscle contraction, which increases pupil (like phenylephrine); the other relaxes the muscles responsible for contracting pupil as well as relaxes the muscle responsible for the focusing action of crystalline (like ciclopentolathus and atropine). These two types of medicine are frequently used together.
Glaucoma represents a group of diseases defined by a characteristic optic neuropathy (optic nerve disease), which is consistent with excavation and weakening of both optic disc and connective tissue as well as with eventual development of distinct patterns of visual impairment. Although high intraocular pressure (IOP) is one of the main risk factors, its presence or absence does not play a mandatory role in defining the disease.
ARMD is the main cause of irreversible visual loss among elderly people all over the world, affecting 30 to 50 million individuals. It is a progressive degenerative disorder of the macula; it has a chronic nature and includes loss of visual acuity typically resultant of photoreceptors’ degeneration, retinal pigment epithelium (RPE) and choriocapillaris.
Cataract is the loss of transparence in crystalline (natural intraocular lens) whose function is to focus light in the retina. This “cloudiness” limits vision and may lead to blindness if not treated in extreme situations. Cataracts generally developed slowly and are pain-free. For this reason, vision and daily life may be affected without any sign.