Retro illumination

retro-illumination

1. RETRO-ILLUMINATION Manahan, M aclester T. OP 1-1

2. Retro-illumination Object of interest is illuminated only by light reflected from the structures behind it.

3. Vary angle of illumination Moderately wide beam Slit beam is offset Medium to high magnification Reflected light from iris or fundus

4. O bjectives 1. 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.

5. Procedure direct retro-illumination: T he 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: T he 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.

6. Alignment of reflected beam with area under observation TYPE ALIGNMENT Direct Direct and full view Indirect Adjacent Marginal Margin or edge

7. Direct Retro-illumination Look to the side of the corneal block Objects viewed may have one color in direct and a different color with retroillumination .

8. 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

9. Indirect Retro-illumination

10. 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

11. observing : Vascularization Epithelial oedema Microcysts Vacuoles Dystrophies Crystalline lens opacities Contact lens deposits

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

13. Vascularization Vascular 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 .

14. Jelly Bumps Lipoidal deposition on the lens surface, common with high water content hydrogel lenses.

15. findings: Expected absence of: Vascularization Epithelial oedema Microcysts Vacuoles Bullae Dystrophies Crystalline lens opacities Contact lens deposits

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