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.