<prompt> Which of the following is true regarding pterygium?Occurs in inter palpepbral fissure mostly on nasal sideDual pterygium is located superiorly and inferiorlyInfective in etiologyIt is not associated with UV radiation  <response>: Ans: a Occurs in inter palpepbral fissure mostly on nasal sideRef: Parson, pg. 175-176Pterygium is a degenerative condition of the subconjunctival tissue which proliferates to invade the comea.lt usually involves the nasal side. When double, both nasal and temporal region is involved.Aetiology: Exposure to sun UV radiation Dry heat High wind Abundance of dustPterygium should be distinguished from a pseudoptyerygium which is an inflammatory process by passing a probe underneath the neck of pseudo pterygium. 