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.
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.
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.
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.