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Journal Français d'Ophtalmologie
Volume 41, n° 1
pages 62-77 (janvier 2018)
Doi : 10.1016/j.jfo.2017.08.003
Received : 6 June 2017 ;  accepted : 17 August 2017
Revues générales

Sclerotic scatter
Dispersion sclérale
 

Figure 1




Figure 1 : 

Basil Graves. Photography taken at the Oxford ophthalmology congress in 1937 and provided by Richard Keeler, honorary curator at the Royal College of Ophthalmologists. The man with the white handkerchief is Basil Graves, 48 years old at the time.


Figure 2




Figure 2 : 

Sclerotic scatter. A red laser aiming beam is applied at the nasal limbal sclera where it is scattered, travels into the cornea through total internal reflection in every possible directions, reaches the opposite side where it scatters a second time in the limbal sclera where it appears as a red light arc.


Figure 3




Figure 3 : 

Schematic cross-section of sclerotic scatter. The incident light (1) is scattered by the limbal sclera (2) in every direction. Most of the directions are incompatible with entry into the cornea (red arrows) but some light does enter the cornea (yellow arrow). Among these rays, some are refracted and leave the cornea (3). Other travelling through total internal reflection may be stopped and scattered by a corneal opacity (4) or may reach the other limbus where they scatter a second time (5) and are visible to the examiner in the form of a limbal scleral arc of light.


Figure 4




Figure 4 : 

Sclerotic scatter with an undisrupted and then trypan blue-filled anterior chamber: a: the slit lamp attached to the operating microscope illuminates the temporal limbus and elicits a limbal scleral light arc on the opposite side; b: the anterior chamber is filled with trypan blue using a Ryckroft canula; c: the anterior chamber is completely filled with trypan blue; d: the slit light beam is again applied at the temporal limbus, which results in a limbal scleral light arc unchanged compared to the initial situation.


Figure 5




Figure 5 : 

Decoupling of the biomicroscope binoculars from the illumination system. Decoupling is achieved by unscrewing the thumb wheel securing the illumination system (yellow curved arrow).


Figure 6




Figure 6 : 

Decentring the illumination system. The decentring is achieved by moving the illumination system around a vertical axis (blue dotted line), either counterclockwise as illustrated here (yellow dotted lines/curved arrows) or clockwise.


Figure 7




Figure 7 : 

Sclerotic scatter in a normal eye. The light beam is directed on one limbus while, through decoupling, the binoculars are centered on the cornea, which does not scatter any light and conveys light to the other limbus, where an arc of light is visible.


Figure 8




Figure 8 : 

Examination of an endothelial lesion through sclerotic scatter, then direct illumination: a: sclerotic scatter clearly shows a cluster of slight central corneal opacities standing out against the dark background of the pupil; b: direct illumination shows that the opacities are endothelial pigments.


Figure 9




Figure 9 : 

Per-operative views of a herpetic corneal scar: a: using direct illumination and retro-illumination, the scar is barely visible; b: using sclerotic scatter, the scar stands out against the dark pupil and the scar limits are sharply demarcated.


Figure 10




Figure 10 : 

Corneal scar caused by a metallic wounding agent. Sclerotic scatter shows the penetration site, roughly vertical and sprinkled with numerous tiny metallic debris shining against the dark background, and the stromal scar, roughly rectangular and extended to the right of the penetration site.


Figure 11




Figure 11 : 

Stromal dystrophic lesion: a: under diffuse illumination, the peripheral yellowish lesion extends from the 9 to the 3 o’clock meridian; b: under sclerotic scatter, the lesion is luminous against a dark background facilitating the analysis of its outline, slightly irregular and, between 1 and 2 o’clock, showing two focal interruptions.


Figure 12




Figure 12 : 

Corneal scar caused by glass debris: a: under diffuse illumination, the scar is barely visible, even against the dark dilated pupil background; b: under sclerotic scatter, the complex shape of the scar as well as that of the scars of the nylon stiches (removed) are clearly visible.


Figure 13




Figure 13 : 

Superficial punctate keratitis. Sclerotic scatter clearly displays numerous epithelial defects against the dark pupil and iris background.


Figure 14




Figure 14 : 

Cornea verticillata and round corneal scar. Sclerotic scatter displays the characteristic brownish combed appearance of amiodarone-related cornea verticillata as well as a round stromal scar located just above and caused by a small superficial metallic foreign body removed a few years before.


Figure 15




Figure 15 : 

Complex corneal lesion: a: under diffuse illumination, the lesion is difficult to analyse partly because a nuclear cataract is present and brightens the background; b: under sclerotic scatter, the lesion appears to be much less large than previously thought, is split into two stromal scars (the largest is on the left) and numerous roughly vertical arcuate endothelial lines of pigment. These lesions stand out against the dark background, with sclerotic scatter providing very little lens illumination.


Figure 16




Figure 16 : 

Use of sclerotic scatter to guide diode laser cycloablation: a: using sclerotic scatter in the dark operating rooms allows clear visualisation of the limbal scleral arc of light opposite the illuminated side; b: the laser probe is put immediately posterior to the posterior limit of the limbal scleral arc of light, which stands 0.5mm behind the scleral spur.


Figure 17




Figure 17 : 

Sclerotic scatter in everyday life. In this left eye, the lateral light illuminates the nasal limbus. The left part of the eyeball is in the shade, which allows the limbal scleral arc of light to be clearly visible.


Figure 18




Figure 18 : 

Sclerotic scatter in everyday life. In the left eye, the light strikes the nasal limbus, where it induces sclerotic scatter and leaves the temporal part of the eyeball in the shade, which explains why the temporal limbal scleral arc of light is easily seen. In the right eye, the light strikes the temporal limbus, where it induces sclerotic scatter and leaves the nasal part of the eyeball in the shade. However, reflection of light on the nose base makes the shade less deep, to such an extent that the nasal limbal sclera arc of light is not visible.


Figure 19




Figure 19 : 

Sclerotic scatter in real life. In this right eye, the light strikes the temporal limbus with a mostly vertical/slightly lateral direction, elicits sclerotic scatter and results in a nasal limbal scleral arc of light standing out in this shaded area.


Figure 20




Figure 20 : 

Sclerotic scatter in everyday life. In this individual, limbal scleral arc of light is visible at the temporal limbus of the left eye and also–despite less contrast owing to reflection of the lateral light on the nose base–at the nasal limbus of the right eye.


Figure 21




Figure 21 : 

Sclerotic scatter in real life. In the left eye, the light strikes the nasal limbus with a mostly vertical/slightly lateral direction, induces sclerotic scatter and results in a temporal limbal scleral arc of light standing out in this shaded area. In the right eye, the light strikes the temporal limbus, where it induces sclerotic scatter. Reflection of the light on the nose diminishes the shade on the nasal side and makes the contrast insufficient for the nasal limbal scleral arc to be seen by the human eye.


Figure 22




Figure 22 : 

Sclerotic scatter in real life: a: in the left eye in the primary position of gaze, the lateral light strikes the temporal limbus in a lateral fashion and induces sclerotic scatter. A limbal scleral arc of light is visible on the nasal side, which stands in relative shade. This relative shade also allows the subject to see a tiny red spot just temporal to the plica semilunaris, corresponding to the internal projection of the pupil area; b: a moment later, under the same lighting conditions, the subject has turned her head and has moved her eye in adduction. The postero-lateral light is concentrated by the cornea in a trans-cameral fashion to the nasal limbus, where it appears as a clear spot is peripheral light focusing (“Coroneo effect”).


Figure 23




Figure 23 : 

Schematic drawing of peripheral light focusing. The postero-lateral light (1) is refracted by the temporal cornea (2), concentrated through the anterior chamber (3) and reaches the nasal limbus where light intensity is roughly 20 times that of the incident light (4).


Figure 24




Figure 24 : 

Peripheral light focusing in everyday life. In this subject, the postero-lateral albedo strikes the temporal cornea, is concentrated through the anterior chamber and is concentrated at the nasal limbus, where it appears as a bright light spot.


Figure 25




Figure 25 : 

Peripheral light focusing in everyday life. An example of peripheral light focusing, with the characteristic nasal bright spot of concentrated light, caused not by albedo, but by direct light.


Figure 26




Figure 26 : 

Co-existence of sclerotic scatter and peripheral light focusing in everyday life: a: in this right eye, the slightly postero-lateral light induces sclerotic scatter on the temporal side, which results in a limbal scleral arc of light clearly visible on the nasal side. Peripheral light focusing is visible on the iris as a triangular light pattern whose summit projects on the nasal sclera, on the 3 o’clock meridian, but is barely visible as the light concentration does not reach its peak for this light incidence and because the sclerotic scatter limbal arc provides a clear background; b: in the same eye, eye adduction results in a much more postero-lateral angle of the incident light. Under this angle, sclerotic scatter is not induced whereas peripheral light focusing reaches its peak, and is clearly visible as a concentrated light spot at the nasal limbus just above the 3 o’clock meridian.

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