ICAO codes are separate and different from IATA codes, which are generally used for airline timetables, reservations, and baggage tags. For example, the IATA code for London's Heathrow Airport is LHR and its ICAO code is EGLL. ICAO codes are commonly seen by passengers and the general public on flight-tracking services such as FlightAware, though passengers will more often see the IATA codes, on their tickets and their luggage tags.
Episcleritis is a relatively common, benign, self-limited inflammation of the episcleral tissues. There are two forms of this condition: nodular and simple. Nodular episcleritis is characterized by a discrete, elevated area of inflamed episcleral tissue. In simple episcleritis, vascular congestion is present in the absence of an obvious nodule. A 2013 study estimated incidence of episcleritis as 41.0 per 100,000 per year and prevalence at 52.6.
The first is non-arteritic (NAION) and the second is arteritic (AAION) and is almost always associated with giant cell arteritis. Posterior ischemic optic neuropathy (PION) encompasses those conditions that result in ischemia to any portion of the optic nerve posterior to the optic disc.p to 97% of patients with NAION have small optic discs with small or absent optic cups. Acutely, it can be difficult to determine the cup/disc ratio because of optic nerve edema and the clinician should note the cup/disc ratio in the fellow eye.