5.2.2. Manages the aftercare of patients wearing rigid gas permeable contact lenses. Flashcards
Routine aftercare
Generally use an all-in-one MPS solution, reduces user error
Place lenses in case overnight, soak for at least 4 hours before wear – always using fresh solution
Remove lenses from lens case, use 4 drops/20second rub on each side
Rinse with steady stream for 5 seconds
Discard solution from case, and clean with solution – clean tissue to dry case is recommended
Solution can be used for conditioner/cushion effect on insertion
Two step
- More room for user error
- Good for px’s who are heavy depositors
- Usually order in Boston 2 step
- Rub both sides with 2-4 drops of Boston cleaner on palm of hand 20s
- Rinse each side with saline for at least 5 seconds to remove cleaner
- Saline e.g. Bausch and Lomb sensitive eyes
- Place lenses in empty case and fill to top ridges with fresh Boston original conditioning solution
- Soak lenses for at least 4 hours before wear
- Before insertion, can wet lenses with conditioning solution for additionally cushioning
Other cleaning tips
- Protein remover enzyme tablets can be done weekly on px’s who are heavy depositors
1. Lenses should be cleaned and rinsed after treatment
1. E.g., Boston one step liquid enzymatic cleaner - Hydrogen peroxide cleaning can also be used, or additionally used once weekly for deep clean
3 and 9 o’clock staining
- Drying @ nasal and temporal areas of the cornea
- Triangle shaped pattern in the periphery; base of triangle corresponds to lens edge
- Caused by thick lens edge design, TD minimal or excessive, insufficient edge clearance, incomplete blinking
- Nasal & temporal bulbar redness
- Can lead to progressive scarring & corneal vascularisation
- Often asymptomatic, possibly decreased WT / red or itchy eyes
**Management **
* Cease wear 24-48 hours
* Refit with increased TD
* Reduce edge clearance
* Refit with SCL
* Blinking exercises
* Modify WT
Dimple veil staining
- Indentations of epithelium caused by pressure of gas/air bubbles trapped under rigid lens
- Small hemispherical pits in epithelium
- More prevalent in poor fitting hard lenses
- Poor lens cornea relationship
- Excessive corneal clearance
- Too flat (more common) or too steep
- Patient generally asymptomatic, may experience mild irritation
**Management **
* Modify lens fit as required
Other types of complications
- Bitot spots; build-up of keratin debris on the conjunctiva associated with long term conjunctival drying; consider thinner lens design
- Dellen; thinning of the cornea causing saucer like depression; long term consequence of desiccation
- FB track
- Lens warpage; replace lens
*
Deposits
**Protein **
* Uneven haze on lens surface
* Very common with high water, ionic lenses (softs)
* Protein remover tablets
Lipid
* High water, non-ionic lenses (softs)
* New lens, change material, increase surfactant cleaning
Fungal growth
* Poor hygiene
lens is flat
Need steeper lens. OR means we can order steeper lens of 0.15mm to correspond with +0.75. Also can reduce TD to make it more centred?
steep
In the below case, instead of giving an OR of -0.50, you can see that the lens is already a little steep so you can, in this case, flatten by 0.1mm which is equivalent to -0.50D as you will be forming a negative tear lens. As a result, the OR & the fit will both be accounted for
Rules of thumb
- Every +0.50mm increase in TD, increased BOZR by 0.05mm
- Every 0.05mm lens is flatter than corneal radius = -0.25D tear lens
- Every 0.05mm lens is steeper than corneal radius = +0.25D tear lens
- If you increase TD, you centre the lens better & better lid hitch
- If you decrease TD, you centre the lens less but reduce rocking along the steeper meridian in a more astigmatic fit
Assessor may ask you describe the design of the lenses:
- BOZR - Radius of curvature of the central, optic zone
- BOZD - Diameter of the central, optic zone of a contact lens
- HVID - horizontal visible iris diameter
- VPA - vertical palpebral aperture
- TD - total diameter of the lens
- Edge lift - Gap between cornea & back surface of peripheral curve (seen in NaFl fit)
- Curves:
- Single curve - useless
- Bicurve - rare/useless - central radius + one flatter peripheral curve (transition too sharp). Better for small diameter lens
- Tricurve - most modern lenses - central radius + more flatter peripheral curves
- Tetracurve - 3+ peripheral curves! Follows flattening of cornea very well. Best for larger diameter lens
- Aspheric lenses - not spherical but follows rate of flattening of cornea very well again
Curves:
- Single curve - useless
- Bicurve - rare/useless - central radius + one flatter peripheral curve (transition too sharp). Better for small diameter lens
- Tricurve - most modern lenses - central radius + more flatter peripheral curves
- Tetracurve - 3+ peripheral curves! Follows flattening of cornea very well. Best for larger diameter lens
- Aspheric lenses - not spherical but follows rate of flattening of cornea very well again
Reasons for using toric:
- >2.50D corneal astig (difference in K’s of 0.5mm)
- >0.75D residual astig (ocular minus corneal)
- Irregular astigmatism
- Poor fit with spherical RGP
- Excessive 3 and 9 o’clock staining
- Increase in toricity towards cornea periphery
- Large amount of lens flexure + corneal warpage
- Corneal ectasias e.g. keratoconus, PMD
Back surface toric
has closely aligned fit to steepest and flattest meridians, so much less toric rotation so no prism stabilisation. Back surface induces some residual astigmatism due to difference between tears and lens material refractive index hence why bitoric is better so its front surface can correct that
Front surface
used when there is lenticular astigmatism for the most part & hardly any corneal. Front surface cyl corrects it whilst the spherical back surface is for the power of the rest of the lens. If a back surface was used, it would not align with the shape of the cornea (as the cornea would be more spherical) and would probably end up inducing more residual astigmatism
Bitorics
used mostly instead of back surface as mentioned above & if front or back surface toric just don’t work well enough i.e. induce too much residual astigmatism
Assessor may ask you of 3 & 9 o’clock staining & how to treat:
The lenses are vaulting your eyelids at certain points on the eye, away from the cornea so on blink, not every part of the cornea is being supplied with tears and being wetted properly. This is causing some areas of dryness on your eye.
Could be caused by incomplete blinking, or even the design of the lens and how it’s centering on the eye
Management:
Aim to improve the centration of the GP lens
Blinking exercises to prevent incomplete blinking
Refit with larger diameter lens and thinner edge design
Refit with a GP toric lens if the cornea is >2D toric
Refit with SiHys if GP lens fitting cannot be improved
Ocular lubricants and/or blinking exercises
