Light streaks / stripes of light
"Doctor, since I had this ocular surgery, when I go outside at night I see streams and long streaks of light across the outdoor lights everywhere I look." What is that? »
This page aims at bringing some elements to better address this issue.
(In french below)
Definition of light streaks
Light streaks are a visual symptoms characterized by the perception by the eye of the a bright straight line emanating from either side of a bright light source.
Unlike circular halos or glare, the spreading of the perceived light spread is straightand always oriented in the same direction.
The mechanism behind this visual symptom is a phenomenon of diffraction of the incident light by has fine structure which is oriented, and can be single or repeated. Light streaks belong to the general group of unwanted visual phenomena called «» dysphotopsias« .
Demonstration of light streaks
Dirty deposits on the glass of windows or windshields can commonly give rise to this kind of phenomenon. It is easy to reproduce by simply leaving a fatty drag there transparent surface: smearing your finger there window but has spectacle lens suffices to cause the diffraction of light by the tiny linear deposits at the surface of the glass. Observing year incoming light source through some dirty linear deposits or scratches it has transparent surface, can clearly render characteristic light streaks, which are always perpendicular to the main axis of scratches however.
Light streaks in ophthalmology
When the direction of the light streak varied with the orientation of the patient's head, the phenomenon is so-called "entoptic". It arises from one of the optical structures of the affected eye (cornea, intraocular lens or in the vast majority of casees).
In ophthalmology, the two main causes of perception of light streak are:
– The folds of the posterior capsule after cataract surgery and replacement of the opaque crystalline lens with year intraocular lens (IOL). A scratch line marked of the optic of the IOL can also cause the perception of some light streak (s).
– The macro-folds formed by the partial displacement of has LASIK flapbecause these are usually grossly parallel folds.
Here is the drawing provided by a patient which perceived oblique light streaks around bright light sources immediately after cataract surgery of his right eye.
Ophthalmic examination at the slit lamp revealed the presence of a single posterior capsular fold marked.
The orientation of this fold was consist with the perceived light phenomenon, but this assessment requires the "vertical reversal" of the apparent direction of the capsular foldto reflect the orientation of the patient's retina opposite of that fold.
The optical phenomenon involved in the genesis of luminous streaks is related to the diffraction of light by the rectilinear folds (posterior capsule, LASIK flap, scratch of the IOL's optic, etc.). The dimension (scale) of the diffracting object (i.e. the capsular fold) are of the same global scale of the wavelengths of visible light (micron scale).
A classic experiment in Optics is to study the diffraction of light waves emitted by a monochromatic source (eg laser pointer) by a thin thread, gold hair, which have thickness of several tens of microns. When a thin wire intercepts the light laser, a diffraction phenomenon is generated. It can be displayed there screen which will feature typical bands of light (from the measurement of the angular width of the central luminous line, one can determine the thickness of the wire used for the experiment).
In physiological optics, light sources perceived by the eye in everyday life are polychromatic and non-coherent; more simply, the light waves they emit are less organized (synchronous in time and space) than a laser source. Therefore, the lateral light spreading generated by the diffraction of the waves is less uniform, because the constructive and destructive interference are much less systematized.
Nevertheless, the Directorate of this light spreading corresponds to that inflicted by the diffractive structure of rectilinear geometry to the flow of incident light waves, and are mutually orthogonal.
Some patients perceive thin iridescent gold colored side fringes "as a rainbow" at the edges of a central light streak emitted by intense white light source, such as a flash-lamp. This colorful spread reflects the sensitivity of the diffractive phenomenon to the wavelength of the light radiation into play, and echoes the intimate wave mechanism of the optical phenomenon involved in the appearance of the disturbing bright light streaks.
Beside careful slit lamp examination, there are no. investigationnal tool which can enable to objectivate the effect on ocular wavefront local of the light path disturbances. Shack Hartman aberrometers are not conceived to highlight and resolve local scatter and diffraction sources within the eye. However, double pass instruments (eg OQAS, HD-Analyzer) may help to tradeoff the scatter incured by marked LASIK flap flods.
The treatment of annoying bright streaks depends on the their cause: smoothing the flap folds in casee of complicated LASIK, however perform has YAG laser capsulotomy in casee of symptomatic capsular folds.
These maneuvers are generally effective and lead to the disappearance or high attenuation of these light streaks.
- Choi CJ, Melki SA. Maddox rod effect to confirm the visual significance of laser in-situ keratomileusis flap striae. J Cataract Refract Surg. 2011; 37 (10): 1748-50.
- Holladay JT, Bishop I, Lewis JW. Diagnosis and treatment of mysterious light seen by streaks patients following extracapsular cataract extraction. J Am Intraocul Soc Implant. 1985; 11 (1): 21-3.
"Doctor, since I had surgery to cataract surgery, when I go out at night, I see some kind of streaks, long streaks of light around the outdoor lights, everywhere I look. What is it that? »
This page live to bring answers to this type of Visual complaints.
The streak (s) light (s) ("light streaks") correspond to a Visual symptom characterized by perception by the eye of a "bright line", a "straight blunder" of a kind "of light elongation", from share and other bright light source. Bright streaks are a type of undesirable visual sensation sometimes felt after surgery of cataract)dysphotopic).
In contrast to the circular halos, bright sprawl is straight is always oriented in the same direction. The mechanism behind this is a phenomenon of diffraction the incident light by a fine structure-oriented, single or repeated.
Streaks of dirt on the glass or the vehicle windshield that can commonly give birth to this kind of phenomenon that it is easy to reproduce: just for example leave an oily streak on a transparent surface, from for example the finger on a glass, or a glass of bezel. Then looking at a light source through the surface soiled or scratched, we perceive distinctly characteristic bright sprawl, which is always oriented perpendicular to the main axis of the scratches.
(see illustration above). After taking a night picture of reference by (own) view of a smartphone (left), the following photographs (right) were obtained by leaving voluntarily, with the pulp of a finger, an oily streak on optics before the smartphone. The orientation of the light streaks, which are clearly visible around the sources of bright light on stereotypes, is every time perpendicular to the main direction of sprawl in dirty drag on the surface of the optics.
When the direction of the light streak varies with the direction of the patient's head, the phenomenon is then called 'entoptique '. It comes directly from one of the optical structures of the affected eye (the cornea or the artificial lens implant), and not a foreign element to it.
In ophthalmology, the two main causes of perception of streak (s) light (s) are:
- Thefolds of the posterior capsule after surgery the cataract and an artificial lens implant. One stripe marked optics of the implant may also cause the perception of a bright streak (s).
- Themacroplis formed by partial displacement of a flap of LASIK, because these folds are usually oriented in a parallel way.
Here is the drawing provided by a patient having received immediate after cataract surgery, oblique light streaks around the sources of bright light from his daily environment. Slit lamp examination revealed the presence of a fairly pronounced posterior capsular fold.
The direction of it is consistent with the perceived phenomenon,... condition «» to invert vertically "the direction of the capsular to fold in the same orientation as the retina of the patient to this. The orientation of the light streak is indeed perpendicular to the folds, in a coordinate system oriented from the retina of the subject, and not that of the examiner.
The optical phenomenon put in game for the genesis of the light streaks is related to the diffraction of light by the rectilinear folds (posterior capsule, flap of LASIK, stripe of an implant, etc.). The dimensions of the object diffractant (here the capsular fold) are neighbours of the wavelengths of visible light (microns).
(see above illustration) A classic experiment in experimental Optics is to study the diffraction of the light waves emitted from a monochromatic source (ex: laser pointer) by a wire, or a hair whose thickness is a few tens of microns. When the wire intercepts the laser light, a diffraction phenomenon is generated and can be viewed on a screen by a characteristic picture which applesauce a bright main line perpendicular to the axis of the wire, along with more peripheral rays separated by dark intervals. From the measurement of the angular width of the central bright line, we can determine the thickness of the wire used for the experiment.
In physiological optics, light sources collected by the eye in daily life are polychromatic and non-coherentes; more simply, the light waves they emit are less synchronous or organized in time and space than a laser source.
As a result, lateral light spread caused by the diffraction of these waves is less regular, because constructive and destructive interference are much less systematized. However, this bright sprawl management fits that inflicts on the incidental light waves flow diffractive rectilinear geometry structure. Some patients also see of thin side fringes iridescent or colored like a Rainbow at the edges of the Central bright streak emitted by an intense source of white light, as a flash lamp. This colorful sprawl reflects the sensitivity of the diffractive phenomenon throughout the wave of light radiation in game, and illustrates the intimately wave mechanism of the optical phenomenon involved in the appearance of the light streaks.
Objective investigations are limited to objectively study the effect of the folds on the ocular Wavefront. The Shack Hartman type aberrometres are not designed to highlight the effects produced by anomalies located within the eye structures such as folds (flap, or capsule). However, systems with double-pass (OQAS, HD-study) may be useful for quantifying the light diffusion induced pronounced folds of flap.
Annoying light streaks treatment depends on the cause of these: there only the flap in case of complicated LASIK, or make a YAG laser capsulotomy in case of symptomatic capsular folds. These maneuvers are generally effective and lead to the disappearance or the strong attenuation of these streaks.