RETRO-ILLUMINATIONManahan, Maclester T. OP 1-1

Retro-illuminationObject of interest is illuminated only by light

reflected from the structures behind it.

Vary angle of illumination

Moderately wide beam

Slit beam is offset

Medium to high magnification

Reflected light from iris or fundus

Objectives1. Assessment of pupils and all parts of the transparent ocular media (tear film, cornea, aqueous, lens, and vitreous). 2. Used to observe whether the opacity is -Obstructive – Opaque to light-Respersive – Scatters light-Refractile – Refracts, minimizes or distorts the views of background.3. Observe anterior capsular changes -Deposits, Foreign bodies, Opacities Below Capsule.

Procedure

direct retro-illumination: The observed feature on the cornea is viewed in the direct pathway of reflected light. The angle between the microscope and the illuminating arm is about 60°.indirect retro-illumination: The angle between the microscope and slit-lamp arms is greatly reduced or increased so that the feature on the cornea is viewed against a dark background. It may be necessary to uncouple the beam.

Alignment of reflected beam with area under observation

TYPE ALIGNMENT

Direct Direct and full view

Indirect Adjacent

Marginal Margin or edge

Direct Retro-illumination

Look to the side of the corneal blockObjects viewed may have one color in direct and

a different color with retroillumination.

The object (observed structure) is viewed in the direct pathway of the reflected light. The illuminated background is directly behind the observed structure.

direct retro-illumination

Indirect Retro-illumination

The object (observed structure) is not viewed in the direct pathway of the reflected light. The retro-illumination object is viewed against a dark non-illuminated background. The reflecting illuminated surface is to one side of the axis of observation.

observed structure

observing:VascularizationEpithelial oedemaMicrocystsVacuolesDystrophiesCrystalline lens opacitiesContact lens deposits

Limbal InjectionLimbal vessel engorgement seen with retro-illumination and very high magnification. This may be a prelude to vascularization.

VascularizationVascular ingrowth into the cornea arising from a vaso-proliferative stimulus..Observe the looping and branching limbal vessels seen against the illuminated background of the clear cornea.

Jelly BumpsLipoidal deposition on the lens surface, common with high water content hydrogel lenses.

findings:Expectedabsence of:

VascularizationEpithelial oedemaMicrocystsVacuolesBullaeDystrophiesCrystalline lens opacitiesContact lens deposits

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