Petechial hemorrhages are pinpoint blood spots that occur when capillaries rupture. In the eye they are seen in the whites of the eye (bulbar petechiae) and in the mucosal linings (undersides) of the eyelids (conjunctival petechiae).
Petechiae tend to occur whenever there is a combination of increased backpressure in the capillaries and deficient blood oxygen (hypoxia). Such a combination occurs during manual (bare hands) strangulation. Neck compression impedes venous return to the heart from the face and head. Airway compromise causes hypoxia. The combination of these events causes ocular capillaries to rupture, forming petechiae. When hypoxia and pressure is extreme, the petechiae become numerous and large, and merge together to form so called confluent petechiae and hemorrhages.
Ocular petechiae are seen in other forms of asphyxia as well. Asphyxia is the condition of insufficient supply of oxygen to the tissues. Asphyxia can be mechanical (such as strangulation and smothering), traumatic (from crushing chest compression, or trapping of the body under a heavy weight) or chemical, such as occurs with carbon monoxide exposure, which impedes the chemical ability of the hemoglobin in the blood to carry oxygen. Of these types of asphyxia, traumatic asphyxia would produce the most severe petechiae.
Other causes of ocular petechiae and hemorrhages would include bleeding disorders, unintended overuse of blood thinners, leukemia, platelet disorders and many others listed in the reference.
In forensic autopsies, ocular petechiae are seen as a red flag that may indicate strangulation or suffocation. That being said, the most common cause of ocular petechiae seen in medical examiner/coroner death cases is heart attack. The patient experiences increased intravascular pressure in the head and neck region due to grunting and the Valsalva maneuver (straining down on the respiratory muscles and contraction of the diaphragm) during the cardiac event, coupled with the hypoxia that occurs as a result of the loss of cardiac output.
As to the rate of disappearance of ocular petechiae I would cite a recent exchange of Emails by a group of fellow forensic pathologists on this subject. The consensus was that ocular petechiae in living subjects such as survivors of attempted strangulation last for several days, getting gradually less prominent, and then slowly fade over time. If petechiae are extensive, confluent and involve larger areas of hemorrhage, then complete resolution of the hemorrhages could take weeks.
"A petechial hemorrhage is a tiny pinpoint red mark that is an important sign of asphyxia caused by some external means of obstructing the airways."
A petechial hemmorrhage could be a tiny red dot or a large red spot covering much of the white of the eye. They can be used by forensic scientists to help decod a cause of death.
They can happen when the body is stressed and the eyes are under pressure. The healing time would vary by person and degree as it is effectively a bruise on the eye.