Distribution of angle lambda and pupil offset as measured by combined Placido Scheimpflug Topography
Hesham Mohamed Gharieb1,2, Hisham Samy Shalaby1, Ihab Saad Othman2,3
1Department of Ophthalmology, Faculty of Medicine, Ain Shams University, Abbassia Square, Cairo, 11591, Egypt.
International Ophthalmology
|July 28, 2022
Summary
Angle lambda, the angle between the pupillary axis and line of sight, is larger in hyperopia than myopia. Preoperative assessment of angle lambda is recommended to prevent surgical decentration, particularly in hyperopic patients.
Area of Science:
- Ophthalmology
- Optometry
- Corneal Topography
Background:
- Angle lambda is crucial for accurate optical centration in anterior segment surgery.
- Understanding angle lambda and pupil center offset is vital for refractive surgery outcomes.
- Combined placido disc and Scheimpflug topography systems offer precise measurements.
Purpose of the Study:
- To determine the distribution of angle lambda.
- To analyze pupil center offset using advanced topography.
- To investigate the relationship between angle lambda, age, and refractive error.
Main Methods:
- A prospective study of 2178 eyes using a Sirius topography system.
- Measurements included keratometry, ACD, CCT, HVID, pupil radius, and pupil center position.
- Angle lambda was calculated trigonometrically; correlations with age and refraction were analyzed.
Main Results:
- Average angle lambda was 3.32° ± 1.99°.
- Angle lambda was significantly smaller in myopia and larger in hyperopia.
- No significant correlation was found between angle lambda and age.
Conclusions:
- Angle lambda is significantly larger in hyperopic eyes compared to myopic eyes.
- Pupil center offset is horizontally greater in hyperopia.
- Preoperative angle lambda assessment is advised to prevent decentered ablation, especially in hyperopia.
