More Common CL Complications

When there's staining in an area around the periphery of the lens it's likely to be one of two things. It could be lens binding which is more common in extended wear lenses, lenses that are too tight or px working in a dry atmosphere. It could also result from damage to the lens from fingernails/getting trapped in the case.

If there are particles visible underneath the lens it's often tear film debris. This is common in the sort of patient that just plonks their lenses in straight away in the morning. The debris will be visible under the slit lamp and will appear to be squashed down by the lens. If the debris is sleep debris then the patient isn't likely to notice it, but makeup has a more granular structure that will cause the lens to become uncomfortable. Mucin balls can be found under extended wear lenses - this is tear debris rolled into a ball by the movement of the lens.

CLPC

Symptoms include itchiness which worsens on removal of the lens. Also reduced wearing time. CLPC is a type IV delayed hypersensitivity reaction. There is a type I element too - the histamine response causing the itchiness.

CL wear should be discontinued for a good length of time - a guideline used = the efron grade of the CLPC x 2 = the number of months to discontinue wear.. EG grade 2 = discontinue for 4 months, assessing again 2 months in. Lens type should also be changed - dailies so that there are no further problems with denatured proteins. Also the lenses are thinner which minimises the mechanical action on the lids. You should expect improvement of at least 1 grade after a couple of months.

Mast cell stabilisers and anti=histamines can be used in the meantime to reduce symptoms as well as cold compresses. Some optoms actually just fit dailies straight away but if the CLPC is grade 2 or more that ain't going to work.

Flat Fitting RGP

Central abrasion that could ulcerate. Refit with steeper lens. The patient could wear the flat lens while the other lens is on order but

• minimise wearing time/wear specs when poss
• come straight back to practice if red eye/painful/blurry vision

Chronic Hypoxia corn neovasc

• Due to overwear, tight fit, lower H20 content lens
• Response = increase O2 transmission w/ultrathin lens/higher H20 content lens (NB consider whether PX will be able to wear higher water content lens in office with AC)

Steep Fitting RGP - Air Bubble?

• Could result in blinking w/froth + areas of dryness
• Fit flatter

Microcysts/Vacuoles

• Reversed light path = microcyst, unreversed = vacuole.
• Grade by counting numbers

Foreign Body

• Stromal diffusion of flu indicates deep!
• Give chloramphenicol every 2hrs for 12 hrs then 4x/day
• NB you have to take lenses out to put drops in, will px comply?
• See px in 24hrs, improvement? If not up dosage again or refer to hospital
• Check that foreign body isn't still around - slit lamp, under lids
• Need to work out cause, gardening accident? Could be something that could be avoided in the future
  

CL Aftercare

Pre-Advice

• Come in wearing lenses
• Daily wear px come in PM so effects of daily lens wear can be seen, extended wear AM so effects of overnight wear can be seen
• Bring in solutions/case

Initial Discussion

• RFV, any problems? comfort & vision ok?
• Recent lens wearing history - max wearing time, how many days/week, how many hours in today?
• Probs handling lenses? Solution/care system ok?
• Any other eye problems?

Vision w/CLs

• Snellen/logMAR acuity monoc/binoc
• Ret w/trial frame, assess quality of reflex (this may indicate lens lifting off central or peripheral cornea
• Duochrome useful

Assessment of Fit (Soft)

• Comfort
• Vision
• Corneal Coverage
• Centration
• Movement on blink
• Lag on upgaze
• Push-up
• K Mires
• Any conj compression/buckling of lens edge

Assessment of Fit (RGP)

• White light - lens position wrt lids, primary & tertiary gaze, lens centration
• Blue light - flu patterns

Also look for

• lens/eye interactions eg lens edge near 3&9 o'clock staining
• Blinking pattern
• Head position (may indicate loose lens)
• Eye movements
• Palp Ap size - can reduce w/RGP, increase w/soft lens

Keratometry over lens

• Can assess fit, front surface wettability

Inspect Lenses

• Knick/tears
• Edge or body defects
• Deposits - protein, mucus, calcium, Fungi, Jelly Bumps, Rust Rings
• Do wettability/TBUT

Lenses Out

Get px to do it if poss. This allows you to see how they do it, whether they wash hands etc. If it's the first aftercare you should ask them to clean the lenses too to see how they're doing it. Correct any errors. Generally assess compliance.

Slit Lamp

White Light

• Perioc skin, eyebrows, upper and lower lids and lashes
• Bulbar conj
• Tear film
• Cornea
• Inf/sup palp conj

Blue w/Flu

• Corneal/conj staining
• TBUT
• Evert eyelids and examine papillae formation on tarsus

Also examine lenses off eye for damage/deposits. Do any necessary supplementary tests. Rose Bengal, ophthalmoscopy if not done for a while etc

Taking Action

• Same lenses w/different params - shift in Rx/alteration of fit
• New lenses of same general type - higher Dk/t
• New lens type - hydrogel to Si-H to improve physiology, RGP to soft to improve comfort
• Change lens wear modality - extended wear to daily wear
• Change replacement freq - monthly to daily?

Taking Action: Care Systems

• Completely change regimen - multipurpose to hydrogen peroxide
• Change version - 2 step to 1 step
• Alter protocol - add extra saline rinse?
• Change to avoid particular preservative
• Eliminate need for solutions - dailies

Final discussion with patient

• Reassurance concerning symptoms - eyes often feel dry at end of day
• Explain why lenses are being changed - more myopic
• Explain why solns being changed - different preservative to avoid red eyes
• Answer any other questions raised - px has heard about extended wear
• Recommended date of next visit - 6 mths?
  

Contact Lenses: Fit Assessment

RGP

• Let lens settle for a few minutes
• Can check centration, TD and movement under white light first - want good centration, staying within limbus, slow and smooth drop on blink, TD should allow ~1mm each side
• Then check flu pattern w/blue light - areas of dark blue = touch and brighter green = clearance with thicker tear film

Alignment Fit

• Even thickness of tears
• Good edge
• Hint of apical clearance
• Centres well
• Drops slowly & smoothly
• Stays within limbus in all dirs of gaze

Steep Fit

• Central pooling suggesting BOZR is less than k reading
• Inadequate edge
• Centres well
• Comfort often fine
• Drops slowly
• +ve liquid lens
• Could see bubble if very steep

Flat Fit

• Central touch and wide edge
• Discomfort
• Centres poorly and moves too much
• Drops quickly and in arc shape on push-up
• -ve liquid lens

Strategies

• Lid Attachment - common now that GP lenses are bigger. Has good comfort. The edge of the lens is in contact with the lid during blinking and in the primary position
• Lid attachment is the natural fit w/minus lenses and gives good tear exchange and comfort. It's more difficult with a plus lens (a -ve carrier is an option). Beware of corneal exposure and moulding
• Interpalpebral was more common when more people were using the smaller PMMA lenses. The centration is good and there's less flare. This strategy is useful if the patient has an irregular peripheral cornea as it only fits the regular central part.
• Alignment fit is used for modern lenses - multicurves, aspherics
• Apical clearance gives better centration if using a small lens.

Overrefraction

• A steep lens results in a positive tear lens so the minus power of the lens itself needs to increase
• A flat lens results in a negative tear lens so the plus power of the lens itself needs to increase

Edge Clearance

• This is the gap between the cornea and the lens edge
• Poor EC = stagnant tears, binding, staining, discomfort, hard to remove
• Good EC = easy removal of lens, good tear exchange, improves lens movement

Soft Lenses

• Can first check comfort and vision - is vision same as best spec Rx?
• If the lens blurs straight after blinking and then clears = flat fit
• If vision starts off clear and then blurs this suggests the lens is too steep
• Can do this subjectively or with keratometer
• Assess coverage (lens 1mm over each side ideally)
• Centration - if bit off to one side but all of cornea is still covered = acceptable. If cornea not covered can either fit a larger TD or smaller BOZR
• Good blink induced movement is 0.2-0.5mm upwards lens recovery straight after blink
• Excess blink induced movement is >0.5mm upwards recovery following blink - fit larger TD or smaller BOZR
• Inadequate = <0.2mm>
• Lag on upgaze - similar params to blink induced movement
• Push-up Test - lens should move w/slight resistance when pushed through lids
• If lens is totally free then larger TD or smaller BOZR
• If movement is sluggish then smaller TD or larger BOZR

Using K Mires

• STEEP - Mires immediately clear post-blink due to lid compression of lens, then mires blur as lens distorts
• FLAT - Mires are blurred immediately post-blink due to prismatic effect of lens movement, then mires clear and lens stabilises

Effect of TD/BOZR on Sag

• Greater BOZR = less sag, flatter fit, looser lens
• Greater TD = more sag, steeper fit, tighter lens

Misc

• Thinner lenses move less than thicker lenses
• Spun cast lenses move less than lathe cut/molded
  

Soft Lens Problems

When doing aftercares the patients (hopefully) turn up with their lenses in but it's also helpful if they bring their case and care system with them too. You can make them demonstrate how they clean their lenses and inspect the mankiness of the case. Even if they are using the solutions etc correctly if they then put the lenses into a manky case they are undoing all the good work. They should really be using the case that's designed to go with the solution too. Someone using a peroxide system will have a barrel case with air vents so the oxygen produced in the process has somewhere to go. Obviously using the peroxide based system and using a flat sealed case ain't going to work as well.

Yet again we have to stress the importance of records. Record all the advice you've given to the patient in case of sueage/gettinghauledupinfrontoftheGOCage. For example if you write down "Advised Patient To Come Back In A Month" at the time and then they don't turn up after you'd sent them the reminder then you have a point from which to defend yourself.

The receptionist should be taught to prioritise contact lens problems. People who should be squashed in as quickly as possible include those with acute red eye, painful eye, sticky eye/discharge, blurry vision and someone with a lens stuck in their eye.

The four main problems encountered in practice are

• Hypoxia
• Toxicity
• Mechanical Insult/Trauma
• Infection

HYPOXIA

eg Px ok but can't wear lenses as long as they used to (12hrs down to 10hrs). NB Ask how long they can wear the lenses comfortably. Patients will often tolerate uncomfortable lenses for a lot longer. You want to try and get an accurate estimate. Also VA is often a bit reduced towards the end of the day. There are three mains signs of hypoxia:

1. Striae - vertical colourless lines running parallel in the centre of the cornea. They are an indicator of corneal oedema. Short term oedema to be precise. When you wake up in the morning your cornea has swollen by 4%. This reduces back to zero as the day goes on. When swelling goes up to 7% or over then striae will appear. The number of striae give an indicator as to the level of oedema.
2. Epithelial Microcysts - These are cysts made up of cellular debris. Their presence suggests that the hypoxia has been there for several weeks. NB complete epithelial turnover in the cornea all the way down to the Bowman's layer takes 2-3 weeks. When a bit of damage is done to the uppermost layers that can be sorted in a couple of hours but an entire regeneration takes longer.
3. Corneal Neovascularisation - Suggests that hypoxia has been there for a few to several months. It takes some time for new blood vessels to form. NB When the hypoxia is sorted the ghost vessels will remain and should be visible. The new vessels are usually spotted at the top and the bottom of the cornea covered by the lids.

Management of Hypoxia

There are several options

• Change the lens type - higher water content (better O2 transmission), thinner, higher Dk material. Silicone hydrogel?
• Reduce wearing time - difficult to get people to cooperate. Needs to be a reduction of 30%-50% for any difference to be noticed. Which is a lot really for people who wear their lenses all the time. And inconvenient.
• RGPs - Smaller, better O2 transmission. But people don't like em.

Remember that there's 21% oxygen in the air, so an eye without a lens is exposed to all of that. Any lens that allows less than 10% of oxygen to get to the cornea is likely to have hypoxia. NB There are different concentrations of oxygen at the edge, centre etc depending on the thickness of the lens, whether it is high + or - etc

TOXICITY

If a patient reports a stinging sensation on inserting the lens that clears up as the day goes on and doesn't have any real other symptoms then it's likely to be a toxic reaction. Ask when the stinging first occurred and if anything changed at that point in time. Here are some problems that don't involve the contact lenses in any way that could have occurred

• New makeup, aftershave, whatever
• Px shaved his beard off at the same time as stinging began - having to use shaving products and aftershave now which could be getting into his eye
• New dog. New dog that px is allergic to
• New quilt with feathers in it that px is allergic to

So basically don't assume that it's the solution causing the problem straight away. Again check how the patient is cleaning the lenses - they might just be doing it wrong. Slit lamp examination could reveal non-serious shallow diffuse corneal punctate staining - same in both eyes. Again this suggests a toxic reaction.

Management

• Get them to get rid of their new quilt/care for the lenses better
• Replace the solution - patient may have developed allergy to the preservative. Choose one with a different preservative, duh. There's no point otherwise. Eg chlorhexidine to polyhexanide to preservative free
• Change the lens type. Pxs aren't usually allergic to a component of the lens, but if you suspect it then you'd be looking to change to a non ionic lens which is more deposit resistant BUT will have a lower water content. So consider that.

MECHANICAL

Painful eye, made more painful when lens is taken out. This suggests damage to cornea from a foreign body or a defect on the lens. The lens will act as a 'bandage' in this case shielding the cornea from the lids and reducing the painful sensation. You could also consider dry eye, especially if the patient is older. Checking TBUT would be a good idea. 10 secs and upwards will probably be ok. You need to compare it to the blink frequency. If the px blinks every 8 seconds then a TBUT of 12s would be ok.

Management of dry eye

• Artificial tear - gel is the best. Watch preservative! Unit dose best but expensive
• Punctal plug
• Decrease wearing time
• Blinking exercises. These never work
• Change lens type - make it thicker and decrease water content to reduce evaporation. Or Si-H. High water content lenses dry much faster.

Management of foreign body

• If on surface of lid remove w/moist cotton bud or nylon loop or sterile needle, forceps
  
• Irrigate (NB always nasal to temporal and with px tilting head down)
• Refer to hospital if it's embedded in the cornea

INFECTION

It's really easy to pick up an eye infection. Discard lenses and start anew! If the infection is painless then it may be herpes - reduced corneal sensitivity - px might not even know there's a problem.