1. Fluorescein Patterns

2. General Information Hydrostatic forces from the tear film holds the CL to the eyeHydrostatic forces from the tear film holds the CL to the eye Fluorescein shows us where there are tears between the lens and corneaFluorescein shows us where there are tears between the lens and cornea –Fluorescein turns green when a cobalt blue or UV light hits it Variations in the intensity of the green will tell us where the lens is close to and far from the corneal surfaceVariations in the intensity of the green will tell us where the lens is close to and far from the corneal surface These variations appear as “fluorescein patterns” that tell us how the lens is fittingThese variations appear as “fluorescein patterns” that tell us how the lens is fitting

3. Viewing the Fluorescein Pattern Instill a small amount of fluorescein into the tearsInstill a small amount of fluorescein into the tears –Wet the strip with saline –Shake off excess fluid from strip –Lightly touch the strip to the inferior palpebral or bulbar conjunctiva –Do not swab or paint the conjunctiva –Do not touch the cornea –Have the patient blink 2-3 times to distribute the fluorescein

4. Viewing the Fluorescein Pattern Use the cobalt blue filter in the slit lampUse the cobalt blue filter in the slit lamp Use a yellow (Wratten 12) filterUse a yellow (Wratten 12) filter –In front of the objective or ocular –Not in front of the light source Use low mag: 10xUse low mag: 10x Use a wide beamUse a wide beam –Slit beam to see FP profile in one meridian Alternatively, use a Burton lampAlternatively, use a Burton lamp –Does not work if the RGP material has a UV blocker: Boston materials

5. Viewing the Fluorescein Pattern Cobalt blue filter without yellow filter Cobalt blue filter with yellow filter

6. Viewing the Fluorescein Pattern Minimum tear thickness visible = 0.0022 mmMinimum tear thickness visible = 0.0022 mm –If tear film is thinner than this, FP appears black –A thin tear film is almost always present between lens and cornea, so some green will be visible even where lens is closest to the cornea Gradation of 0.02 mm visible as changes in FP green intensityGradation of 0.02 mm visible as changes in FP green intensity

7. Viewing the Fluorescein Pattern Too much fluorescein will obscure the true FPToo much fluorescein will obscure the true FP –Front surface fluorescein –Artificially thick post-lens tear film –Wait for most of the Fl to dissipate Too little will not reveal true FPToo little will not reveal true FP –Will appear “alignment” even if not

8. Viewing the Fluorescein Pattern

9. Pattern Relationships AlignmentAlignment –Back surface of lens matches the corneal curvature ClearanceClearance –There is space between the lens and cornea TouchTouch –The lens is close to the cornea compared to another part of the lens FlatSteepAligned

10. Pattern Locations ApicalApical –Central portion of the FP –Area under the optic zone Mid-peripheralMid-peripheral –Area under the intermediate curves –Determines lens positioning and movement patterns PeripheralPeripheral –Area under the peripheral curve –Determines tear exchange

11. Pattern Dynamics Static patternStatic pattern –FP when the lens is centered on the cornea –If lens decenters, must manually center lens using patient’s lids –Gives true apical relationship Dynamic patternDynamic pattern –FP when the lens is in its normal resting position –May be different from static pattern –Pattern not as flat as when centered because peripheral cornea is flatter

12. Pattern Dynamics Dynamic pattern: Normal resting position Static pattern: Lens in central position

13. Patterns Apical alignment (AA)Apical alignment (AA)

14. Patterns Apical clearance (AC)Apical clearance (AC)

15. Patterns Apical touch (AT)Apical touch (AT)

16. Patterns Mid-peripheral alignmentMid-peripheral alignment

17. Patterns Mid-peripheral touchMid-peripheral touch

18. Patterns Mid-peripheral clearanceMid-peripheral clearance

19. Patterns Peripheral clearancePeripheral clearance Minimal / none Moderate / medium High / excessive

20. Toric Patterns With-the-ruleWith-the-rule

21. Toric Patterns Against-the-ruleAgainst-the-rule

22. Toric Patterns 1 D corneal toricity1 D corneal toricity

23. Toric Patterns 2 D corneal toricity2 D corneal toricity

24. Toric Patterns 3 D corneal toricity3 D corneal toricity

25. Toric Patterns 4 D corneal toricity4 D corneal toricity

26. Toric Patterns Alignment, clearance and touch patternsAlignment, clearance and touch patterns Apical touch: On Flat K Apical alignment: Splitting K Apical clearance: On Steep K

27. Toricity and Lens Position With-the-rule corneasWith-the-rule corneas –Superior or inferior position –Good for LA but poor if inferior –Steeper fits tend to center better Against-the-rule corneasAgainst-the-rule corneas –Temporal or nasal position –Poor comfort when decentered laterally –Difficult to stabilize –Steeper fits tend to center better

28. Changes in FP with Decentration FP is not as flat as when centeredFP is not as flat as when centered –Central cornea is steeper than periphery Mid-peripheral arcuate poolingMid-peripheral arcuate pooling Companion touch in peripheryCompanion touch in periphery –In direction of decentration

29. Changes in FP with Decentration

30. Toricity and Lens Movement