This document discusses retro-illumination techniques used during ophthalmic examinations. Retro-illumination involves illuminating the object of interest using light reflected from structures behind it. It can be used to assess the pupils and transparent ocular media, and to observe whether any opacities are obstructive, refractive, or refractile. Direct retro-illumination views the observed structure in the direct path of reflected light, while indirect retro-illumination views the structure against a dark background. Retro-illumination allows visualization of features like vascularization, edema, microcysts, and contact lens deposits.

1. RETRO-ILLUMINATION
Manahan, Maclester 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. Objectives
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:
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.

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 retroillumination 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

16. tђคภк ‫ץ‬๏ย