The normal process of change is: brittle nails, straight nails, spoon-shaped nails. Subungual hematoma occurs when trauma to the nail results in a collection of blood, or hematoma, under the nail. It may result from an acute injury or from repeated minor trauma such as running in undersized shoes. Acute subungual hematomas are quite painful, and are usually treated by releasing the blood by creating a small hole in the nail. Drilling and thermal cautery  are common methods for creating the hole. Thermal cautery is not used on acrylic nails because they are flammable. Onychomatricoma, a tumor of the nail matrix. Nail pemphigus, an auto-immune disease. Erythronychia, red bands in the nail from some inflammatory conditions. Melanonychia, a black, brown or grey  discoloration of the nail, with numerous causes. Nail changes and conditions associated with them
Nail inspection can give hints to the internal condition of the body as well. Nail disease can be very subtle and should be evaluated by a dermatologist with a focus in this particular area of medicine. A nail technician may be the first to note a subtle change in nail health. Pliability
Brittleness is associated with iron deficiency, thyroid problems, and impaired kidney function. Splitting and fraying are associated with psoriasis and deficiencies of folic acid, protein, and Vitamin C.
Unusual thickness is associated with circulation problems. Shape and texture
Nail clubbing - nails that curve down around the fingertips with nailbeds that bulge is associated with oxygen deprivation and lung, heart, or liver disease.
Several therapeutic approaches, such as contact lenses, drugs, surgery, and low vision rehabilitation have also been proposed. For example, it has been proposed that mini-telescopic eyeglasses suppress nystagmus.Surgical treatment of congenital nystagmus is aimed at improving head posture, simulating artificial divergence, or weakening the horizontal recti muscles. Clinical trials of a surgery to treat nystagmus (known as tenotomy) concluded in 2001. Tenotomy is now being performed regularly at numerous centres around the world. The surgery aims to reduce the eye oscillations, which in turn tends to improve visual acuity.Acupuncture tests have produced conflicting evidence on its beneficial effects on the symptoms of nystagmus. Benefits have been seen in treatments in which acupuncture points of the neck were used, specifically points on the sternocleidomastoid muscle. Benefits of acupuncture for treatment of nystagmus include a reduction in frequency and decreased slow phase velocities, which led to an increase in foveation duration periods both during and after treatment. By the standards of evidence-based medicine, the quality of these studies is poor (for example, Ishikawas study had sample size of six subjects, was unblinded, and lacked proper controls), and given high quality studies showing that acupuncture has no effect beyond placebo, the results of these studies have to be considered clinically irrelevant until higher quality studies are performed. Physical or occupational therapy is also used to treat nystagmus.