Off-axis edge glare in pseudophakic dysphotopsia.
OBJECTIVE
To characterize peripheral light focusing of oblique off-axis light in the edge-glare phenomenon associated with pseudophakic dysphotopsia.


METHODS
Department of Ophthalmology, Prince of Wales Hospital, The University of New South Wales, Sydney, Australia.


METHODS
Nonsequential optical ray-tracing (OptiCAD) was performed on a model pseudophakic human eye with an intraocular lens (IOL). The acrylic IOL had an anterior radius of 14.23 mm, posterior radius of 25.00 mm, center thickness of 0.72 mm, diameter of 6.00 mm, and refractive index of 1.5597. Peripheral light focusing caused by off-axis light was calculated for light rays incident on the temporal cornea at angles between 0 degrees and 120 degrees to the sagittal plane.


RESULTS
Light incident on the temporal cornea at oblique angles was able to strike the nasal portion of the IOL and the nasal retina. The focusing gain was 2.56 times the incident intensity. The critical incidence window at the temporal cornea was between 71 degrees and 89 degrees to the sagittal plane. The light-focusing effect created foci of light in the nasal edge region of the IOL. In the mid range of permissive angles, up to 3 secondary images were formed, some of which may be apparent only under scotopic conditions.


CONCLUSIONS
Off-axis light incident at the temporal cornea formed intense foci in the nasal edge of the IOL. Multiple secondary images can be formed. These spots constitute glare sources and may be of sufficient intensity to disturb vision. These findings indicate that off-axis light may be an important contributor to some disability glare problems and that IOL edge design should be reevaluated to minimize dysphotopsia associated with peripheral focusing effects.
Coroneo
Minas T
MT
Department of Ophthalmology, Prince of Wales Hospital, The University of New South Wales, Sydney, Australia.
Pham
Therese
T
Kwok
L Stephen
LS
D003198:Computer Simulation; D019466:Glare; D006801:Humans; D007910:Lenses, Intraocular; D008027:Light; D008962:Models, Theoretical; D011474:Prosthesis Design; D012542:Scattering, Radiation; D014786:Vision Disorders / Q000209:etiology*