Epidemiology
Retinoblastoma presents with cumulative lifetime incidence rate of one case of retinoblastoma per 18000 to 30000 live births worldwide. A higher incidence is noted in developing countries, which has been attributed to lower socioeconomic status and the presence of human papilloma virus sequences in the retinoblastoma tissue.Almost 80% of children with retinoblastoma are diagnosed before three years of age and diagnosis in children above six years of age is extremely rare. In the UK, bilateral cases usually present within 14 to 16 months, while diagnosis of unilateral cases peaks between 24 and 30 months. See also
Eye cancer
Eye examination
Retinoblastoma protein

References
External links
Retinoblastoma information from MedlinePlus
retinoblastoma at NIH/UW GeneTests
RB1 Mutation Database
Retinoblastoma at Curlie
NCBI Genetic Testing Registry
Drug tolerance or drug insensitivity is a pharmacological concept describing subjects reduced reaction to a drug following its repeated use. Increasing its dosage may re-amplify the drugs effects; however, this may accelerate tolerance, further reducing the drugs effects. Drug tolerance is indicative of drug use but is not necessarily associated with drug dependence or addiction. The process of tolerance development is reversible (e.g., through a drug holiday) and can involve both physiological factors and psychological factors.One may also develop drug tolerance to side effects, in which case tolerance is a desirable characteristic. A medical intervention that has an objective to increase tolerance (e.g., allergen immunotherapy, in which one is exposed to larger and larger amounts of allergen to decrease ones allergic reactions) is called drug desensitization.The opposite concept to drug tolerance is drug reverse tolerance (or drug sensitization), in which case the subjects reaction or effect will increase following its repeated use. The two notions are not incompatible and tolerance may sometimes lead to reverse tolerance. For example, heavy drinkers initially develop tolerance to alcohol (requiring them to drink larger amounts to achieve a similar effect) but excessive drinking can cause liver damage, which then puts them at risk of intoxication when drinking even very small amounts of alcohol.Drug tolerance should not be confused with drug tolerability, which refers to the degree to which overt adverse effects of a drug can be tolerated by a patient.