), but few macular degeneration patients experience total visual loss.The area of the macula constitutes only about 2.1% of the retina, and the remaining 97.9% (the peripheral field) remains unaffected by the disease. Even though the macula provides such a small fraction of the visual field, almost half of the visual cortex is devoted to processing macular information.In addition, people with dry macular degeneration often do not experience any symptoms but can experience gradual onset of blurry vision in one or both eyes. People with wet macular degeneration may experience acute onset of visual symptoms. Risk factors
Key risk factors are age, race/ethnicity, smoking, and family history. Advanced age is the strongest predictor of AMD, particularly over 50. Race/Ethnicity
As illustrated by the Figure in this section, derived from data presented by the National Eye Institute of the United States (https://www.nei.nih.gov/learn-about-eye-health/eye-health-data-and-statistics/age-related-macular-degeneration-amd-data-and-statistics/age-related-macular-degeneration-amd-tables), among those over 80 years of age, White individuals are more than 6-fold more likely to develop AMD than Black or Hispanic individuals. Thus, white background is a major risk factor for AMD. In Caucasian (White) skin, there is a specific group of polymorphic genes (with single nucleotide alterations) that encode for enzymes and transcription factors responsible for the early steps (including the first step, formation of L-DOPA from the amino acid tyrosine) of the melanin synthesis pathway. Many of these enzymes and transcription factors are reviewed by Markiewicz and Idowu. Also, as reviewed by Sturm et al.
Primary
Primary occlusal trauma occurs when greater than normal occlusal forces are placed on teeth, as in the case of parafunctional habits, such as bruxism or various chewing or biting habits, including but not limited to those involving fingernails and pencils or pens. The associated excessive forces can be grouped into three categories. Excesses of:
Duration
Frequency and
MagnitudePrimary occlusal trauma will occur when there is a normal periodontal attachment apparatus and, thus, no periodontal disease. Secondary
Secondary occlusal trauma occurs when normal or excessive occlusal forces are placed on teeth with compromised periodontal attachment, thus contributing harm to an already damaged system. As stated, secondary occlusal trauma occurs when there is a compromised periodontal attachment and, thus, a pre-existing periodontal condition. Cause and treatment
Teeth are constantly subject to both horizontal and vertical occlusal forces. With the center of rotation of the tooth acting as a fulcrum, the surface of bone adjacent to the pressured side of the tooth will undergo resorption and disappear, while the surface of bone adjacent to the tensioned side of the tooth will undergo apposition and increase in volume.In both primary and secondary occlusal trauma, tooth mobility might develop over time, with it occurring earlier and being more prevalent in secondary occlusal trauma. To treat mobility due to primary occlusal trauma, the cause of the trauma must be eliminated. Likewise for teeth subject to secondary occlusal trauma, though these teeth may also require splinting together to the adjacent teeth so as to eliminate their mobility.