Pterygium Most Commonly Occurs on the Nasal Side
Pterygium develops most frequently on the nasal (medial) side of the conjunctiva, accounting for approximately 72% of cases 1. This nasal predominance is well-established in clinical practice and supported by recent surgical outcome data.
Clinical Distribution Pattern
The typical distribution of pterygium by location is:
- Nasal pterygium: 72% - by far the most common presentation
- Bipolar pterygium: 8% - affecting both nasal and temporal sides
- Temporal pterygium: 3% - relatively rare
- Unspecified/other locations: remaining cases 1
Why the Nasal Side Predominates
Multiple mechanisms explain this nasal predilection 2:
Increased UV light exposure - The nasal conjunctiva receives more concentrated ultraviolet radiation due to light reflection patterns and the anatomy of the periorbital region. Light enters from the temporal side and reflects off the nose, concentrating exposure nasally.
Tear film dynamics - Abnormal tear distribution and flow patterns may preferentially affect the nasal conjunctiva
Anatomical factors - The nasal conjunctiva may have different responses to physical and chemical stimuli compared to temporal conjunctiva
Genetic and environmental interactions - Predisposition combined with chronic irritation from habitual eye rubbing tends to affect the nasal side more frequently
Clinical Implications
When examining for pterygium, always check the nasal conjunctiva first as this is where you'll find the lesion in nearly three-quarters of cases. However, don't neglect examining the temporal side, particularly in patients with significant UV exposure or recurrent disease, as bipolar presentation occurs in 8% of cases.
The nasal predominance is so consistent that a primarily temporal pterygium should prompt consideration of whether the diagnosis is correct or if there are unusual contributing factors in that specific patient.