Lecture 14 RGP complications

Question 1

What are the underlying causes of RGP complications?

Answer 1

hypoxia
drying
mechanical
toxic/hypersensitvity

Question 2

What are the signs of hypoxia?

Answer 2

*Oedema
-spectacle blur
-striae/folds
-corneal steepening/corneal warpage
*Polymegethism
*Neovascularisation

Question 3

What can cause corneal oedema?
What are the signs?

Answer 3

*Happens with PMMA and low Dk lenses
*Tight fitting which restricted tear exchange.

*Stroma likely to be affected
*Corneal oedema causes irregularity of cornea which causes light scatter
*May cause corneal clouding
*Shape of cornea will change due to oedema. -Can get corneal steepening associated with myopic shift.

Question 4

How does corneal oedema occur?

Answer 4

*If we have a tight-fitting lens, there is no oxygen permeability
*This creates a hypoxic environment
*Epithelium begins to respire anaerobically to conserve energy
*Lactic acid is created
*Lactate concentration in epithelium increases and it moves into the stroma
*Creates osmotic effect. Promotes transfer of water from less concentration to high concentration.
*Cornea starts to gain more water
*Endothelial pump cannot remove water from stroma at the same rate it is entering the stroma

Question 5

What are the signs of corneal oedema in order of increasing oedema?

Answer 5

Striae
*Fine, wispy, vertical lines
*In posterior stroma
*Striae increase as oedema increases
*Fluid separation of collagen fibres

Folds
*Depressed grooves, raised ridges
*Physical buckling of posterior stroma in response to oedema

Haze
*Stroma hazy, milky appearance
*Gross separation of collagen fibres throughout stroma

Question 6

What causes endothelial polymegathism?

What is this?

What is the consequence?

Answer 6

*Long-term hypoxia

*Structural damage to endothelial cells
*Change to shape/size of cells. Should be hexagonal
*Capacity for endothelium to remove water diminishes
*Specular reflection to examine cells

*Corneal exhaustion syndrome
*Cant repair this
*Can create problems for future surgery

Question 7

Which type of lens is neovasc not common in?

If it does occur, what is it associated with?

Answer 7

RGP lenses as lens sits in mid peripheral cornea where you don’t get neovasc

Could be associated with poor (PMMA) lens fit, chronic irritation, poor tear exchange

Question 8

What causes vascularised limbal keratitis?

What is it?

What are the signs?

What is the differential diagnosis?

Answer 8

*Chronic CL induced irritation
*Mainly mechanical gives inflammatory reaction
*Associated with inadequate lubrication and low edge lift

*Semi-opaque corneal nodule.
*Called pseudopterygium

• Approaches onto cornea.
  *Close to lens edge
  *3 and 9 o clock or 4 and 8 o clock staining
  *Coalesced superficial staining
  *Localised superficial and stromal
  neovascularization

*Pterygium

Question 9

What can cause 3 and 9 o clock staining?

What is the origin?
What is it associated with?

Answer 9

*Poor or incomplete blinking
*Poor tear film. Surface evaporates quickly (low TBUT)
*Large eye (wide palpebral aperture)
*RGP material
*Excessive edge clearance
*Edges to thick
*Total diameter too large
*Total diameter too small

-created through impression of lens edge
-nasal and temporal staining

-associated with dellen (small area of cornea that dry’s out, thins and is exposed)

Question 10

What are the solutions for 3 and 9 o clock staining?

Answer 10

*Break from lens wear- (esp if moderate)
*Correct blinking (exercises)
*Change care regime, ocular lubricants
*Refit with different material
*Refit with a soft lens
*Refit with lid attachment design
*Different TD
*Different peripheral design

Question 11

What mechanical complications can you get from RGP wear?

Answer 11

*Corneal shape changes
-corneal topography changes
-corneal warpage
-Fischer-Schweitzer pattern
*Lens binding
*Dimple staining
*Foreign body tracks
*Ptosis
*Contact lens associated palpebral changes (mechanical and allergic)
*Mechanical 3 and 9 o clock staining

Question 12

What corneal topography changes can you get?
What are the symptoms?
what is it associated with?

Answer 12

*Change in contour of cornea
*Corneal oedema makes warpage of cornea more prevalent

*Px will experience distorted vision

*Associated with ill-fitting PMMA lenses

Contraindication for refractive surgery

Question 13

What causes a fischer-schweitzer pattern?
Waht are the signs?
What is the management?
What is the differential diagnosis?

Answer 13

*Mechanical deformation caused by ill-fitting lens

*Polygonal mosaic
*Wrinkling of bowman’s membrane
*Stress indicator for cornea and poor fitting lens
*Can be localised or cover whole cornea

*Disappears on lens removal
*No long-term implications

epithelial wrinkling

Question 14

What is epithelial wrinkling associated with?

what are the signs and symptoms?

Answer 14

*Associated with soft CL

*Small lines or furrows at any angle
*Very painful
*Vision affected

Question 15

What causes lens binding?

What are the signs and symptoms?

What is the management?

Answer 15

*Immobile, decentred lens
*Eyelid pressure, indentation of cornea by lens edge
*Suction effect

*Superficial keratitis may be noted
*Px will have difficulty removing lens
*Indentation staining in removal

*Need to alter lens fit to increase mobility
*Cease wear temporarily
*Review k readings before fitting

Question 16

What causes dimple staining?
What does it indicate?
What is the management?

Answer 16

*Small bubbles become mechanically compressed
*Indentations in epithelium

*Indicates Poor lens fit relationship between cornea and posterior lens surface
*Can occur in flat and steep lens. in steep fitting, bubbles will be very central. In WTR where lens stand off the cornea, you can get air bubbles.

*Remove lens and modify fit
*Can get this in SCL

Question 17

In what lens material are foreign body tracks more common?
what are the symptoms?
What is the management?

Answer 17

*More common in PMMA and RGP lenses than soft (drape more and less movement than RGP)

*Will be Symptomatic: discomfort, lacrimation

*Assess depth and extent
-Remove lens, address cause, maybe replace lens
*Need staining to heal before lens wear

Question 18

What can cause ptosis in RGP wearers?
What is the management?

Answer 18

*Long-term wearers of PMMA or RGP lenses
*Possibly due to lens removal procedure of pulling laterally on the eyelids followed by a harsh blink
*Other causes may be the constant rubbing of the lens edge against the palpebral conjunctiva

*Exclude other serious neurological causes
*Could try soft lenses or cease wear

Question 19

What are the signs of CLAPC?
What is the management?

Answer 19

CL associated palpebral changes
*Located towards the lash margin
*Crater-like form

*Cese lens wear, lubrication drops then review
*May be looser fitting lens or lots of edge lift

Question 20

What complications can you get due to hypersensitivity/toxicity?

Answer 20

CLAPC-protein
Solution toxicity

Question 21

What causes CLAPC-protein?

What are the signs?

What is the management?

Answer 21

*Protein deposits build up on lens and proteins denature overtime
*Greater likelihood of getting inflammatory response
-Greater in RGP wearer

*Located closer to fold of everted eyelid
*Aped of papillae are more numerous and the apex of papillae are rounder, flatter

*Protein removal tablets
*Frequent replacement

Question 22

What causes a solution toxicity reaction?
What are the signs and symptoms?

Answer 22

*Sensitivity to preservative
*Can be due to getting peroxide cleaner in the eye

*Localised epithelial reaction (superficial punctate keratitis)
*Conjunctival hyperaemia
*Burning sensation