Purpose :Entoptic starburst patterns around bright lights are routinely observed at night and are a common source of complaint associated with numerous visual therapies including multifocal contact lenses and refractive surgery. We sought to uncover the spatial characteristics and optical origins of these starbursts.
Methods: Eyes with dilated pupils, elevated levels of defocus and spherical aberration, and post-refractive surgery eyes viewed a bright (1000 cd/m2) two arc minute diameter light source. Apparent diameter of starburst was quantified using a second channel, and detailed drawings of starbursts were obtained. Pupil regions contributing to starbursts were mapped by selectively masking pupil margins, pupil center, and mid-peripheral pupils, as well as restricting the aperture to pie-shaped pupils of varying angular extent and meridian.
Results: With a 7mm pupil, starburst radius can exceed 2 degrees in eyes with elevated levels of spherical aberration (e.g. wearing multifocal contact lenses), and in post-LASIK and presbyopic eyes. The size of starbursts varies linearly with defocus level, and is proportional to pupil radius squared for paraxially focused eyes. In the presence of positive SA, temporal and superior starbursts appear when the temporal and superior sectors of the pupil are exposed, respectively, In the presence of negative SA, these same sectors produce nasal and inferior starbursts, respectively. Individual starburst lines are generated by narrow (20 to 30 degree) wide angular segments of the pupil. The center, middle, and outer edge of the starbursts originate from about 1.5 mm from pupil center, intermediate pupil radii, and pupil margins respectively.
Conclusion: Unlike the ciliary corona, which is caused by diffraction, the more typically seen starbursts appear to be caustics generated by geometrical optical aberrations within localilzed regions of the peripheral pupil. The starburst night disturbance experienced by highly aberrated eyes can be segmentally obstructed by an annular aperture (e.g., corneal inlay) or completely eliminated with a small pupil (diameter ≤3mm).