ocular straylight

Ocular straylight is a phenomenon where parts of the eye are able to scatter light, creating glare. It is analogous to stray light in other optical systems; scattered light reaches the retina, but does not contribute to forming a correct image.

One can observe the effect of straylight by looking at a distant bright light source against a dark background. If the source is small, it would look like a small bright spot if the eye imaged it perfectly. Scattering in the eye makes the source appear spread out, surrounded by glare. The disability glare caused by such a situation has been found to correspond precisely to the effect of true light.Vos JJ. "Disability glare - a state of the art report". Commission International de l'Eclairage Journal. 1984;3/2:39-53{{clarify|date=November 2015}} As a consequence, disability glare was subsequently defined by this true light, called "straylight".{{clarify|date=November 2015}}

Individual differences

Straylight can differ considerably between individuals. Aging of the crystalline lens of the human eye causes straylight to become worse.Van den Berg TJTP et al. "Straylight effects with aging and lens extraction". Am J Ophthalmol. 2007;144:358-363 Lens extraction and artificial lens implantation is an effective treatment.

Less common causes for straylight include:

Diseases of the cornea, e.g. Fuchs' dystrophy.Van der Meulen IJ et al. "Quality of vision in patients with Fuchs Endothelial dystrophy and after DSEK". Arch Ophthalmol 2011
Lack of pigmentation, e.g. albinism.Kruijt B et al. "Ocular straylight in albinism". Optom Vis Sc 2011;88:E585-E592
Laser refractive surgery, with occasional haze formation.Van Bree MC et al. "Straylight values after refractive surgery". Ophthalmology 2011;118:945-953.
Excessive floaters in the vitreous humour.Mura M et al. "Surgery for floaters". Ophthalmology 2011;118:1894
Contact lenses.Van der Meulen IJ et al. "Straylight measurement in contact lens wear". Cornea 2010;29:516-522

References

Category:Vision