Blindness is the condition of lacking visual perception due to physiological or neurological factors. Various scales have been developed to describe the extent of vision loss and define “blindness.”[1] Total blindness is the complete lack of form and visual light…
Blepharitis (pronounced /bl?f?r?a?t?s/) is an ocular disease characterized by inflammation of the eyelid margins. Blepharitis may cause redness of the eyes, itching and irritation of the eyelids in one or both eyes. Its appearance is often confused with conjunctivitis and…
An optical system with astigmatism is one where rays that propagate in two perpendicular planes have different foci. If an optical system with astigmatism is used to form an image of a cross, the vertical and horizontal lines will be…
Asthenopia (aesthenopia) or eye strain is an ophthalmological condition that manifests itself through nonspecific symptoms such as fatigue, red eyes, eye strain, pain in or around the eyes, blurred vision, headache and occasional double vision. Symptoms often occur after reading,…
Amblyopia, otherwise known as lazy eye,[1] is a disorder of the visual system that is characterized by poor or indistinct vision in an eye that is otherwise physically normal, or out of proportion to associated structural abnormalities. It has been…
Amaurosis (Greek meaning darkening, dark, or obscure) is vision loss or weakness that occurs without an apparent lesion affecting the eye [1]. It may result from either a medical condition or from excess acceleration, as in flight. The term is…
Addison’s disease (also known as chronic adrenal insufficiency, hypocortisolism or hypocorticism) is a rare endocrine disorder in which the adrenal gland produces insufficient amounts of steroid hormones (glucocorticoids and often mineralocorticoids). It may develop in children as well as adults,…
Ascariasis is a human disease caused by the parasitic roundworm Ascaris lumbricoides. Perhaps as many as one quarter of the world’s people are infected[1], and ascariasis is particularly prevalent in tropical regions and in areas of poor hygiene. Other species…
Acromegaly (from Greek akros “extreme” or “extremities” and megalos “large” – extremities enlargement) is a syndrome that results when the pituitary gland produces excess growth hormone (hGH) after epiphyseal plate closure. A number of disorders may be affecting the pituitary…
Hypothyroidism is the disease state in humans and animals caused by insufficient production of thyroid hormone by the thyroid gland. Cretinism is a form of hypothyroidism found in infants. Causes of Hypothyroidism About three percent of the general population is…