Complex pathology is now in the realm of ‘easy peasy’. Not so RGPs!
Retinal detachment? Glaucoma suspect? Microbial keratitis? These days, to most practicing optometrists, diagnosis and appropriate management of complex ocular pathology is getting into the realm of ‘easy peasy!’
Yet, interestingly, what strikes fear into the heart of many optometrists is seeing a rigid contact lens (RGP) on a patient and being the optometrist in the room that has to manage it.
A combination of limited previous prescribing experience, coupled with a healthy fear to do the best by the patient, results in some of us breaking into a cold sweat when faced with these seemingly intimidating, precisely manufactured, tiny bits of plastic.
If BCVA improves significantly, it’s an ideal time to recommend changing and getting new lenses
To assist, here’s a ‘Simple Six Step Survival Guide’ to ensure you have the basics covered… here’s how to assess a pre-existing corneal rigid lens that somehow floated into your patient chair via their tear film.
Before You Take Any Steps…
Exceptional eye care practitioner that you are, you’ve performed a thorough, detailed history and established if the existing lenses have been working well or if they have been fluctuating in their performance.
If we have an eye that has pre-existing issues with any ocular pathology or corneal irregularity – including conditions such as keratoconus or post refractive ectasia – we have to be mindful that the best-corrected visual acuity might not be 20/20. Perform a diagnosis of exclusion (pinhole), so you don’t keep going round in circles with refraction, trying to coax vision out of an eye that it simply cannot achieve. More about what to do with the best corrected visual acuity (BCVA) and over-Rx is included in the following steps.
Step 1: Assess the Central Fit
Critically, RGPs need to be optimised and well fitted centrally. In particular, if we are working with a compromised or structurally weakened cornea, we know an eye with keratoconus is more susceptible to adverse inflammatory and infectious events than a ‘normal’ cornea and is much more likely to be susceptible to apical corneal scarring1, thus causing reduced vision, and then as a consequence, the patient requiring a corneal transplant.
Assessing the central fit of a corneal RGP is best performed by pushing the lens up into the central corneal position and seeing if the lens displays an alignment fit.
An alignment fit means it displays a small amount of sodium fluorescein (NaFl) pooling to demonstrate ‘just apical clearance’ thus confirming an absence of central corneal bearing. This rests the majority of the weight (bearing) of the lens on the mid-peripheral cornea.
In dealing with a case of corneal irregularity, this means that it rests on the cornea that is relatively free from corneal ectasia surrounding the centre of the cornea. We then optimise the mid-peripheral design to be closely aligned to the corneal surface.
Here is an example to show insufficient corneal clearance leading to apical corneal scarring secondary to a suboptimal fitting (Figure 1) versus optimal central clearance (Figure 2).
In the instance of a larger specialty contact lens such as a corneo-scleral or scleral lens, there is far more lens weight to support on the cornea, so even more caution has to be taken to ensure corneal clearance. Here is a second example to show corneal apical scarring secondary to a suboptimal fitting from a longstanding poorly fitted scleral lens (Figure 3). The next lens shows the refitted patient with a much better scleral lens for her keratoconus (Figure 4 and 4a).
Step 2: Assess Peripheral Fit and Edge Lift
The peripheral fit and edge lift indicates how closely aligned the lens fits on the eye overall and will thus be one of the main factors that governs appropriate or excessive movement. It is one of the main factors to determine how much the lens moves on the eye.
Step 3: Peripheral Interaction of Lenses in Situ
Assess lens diameter: check if the corneal RGP displays any intrusion onto the limbus. If it does, consider if it has to, as it is more likely to promote a pro-inflammatory response if the lens crosses the corneo-scleral junction.
Step 4: Determine Over-Refraction (Over-Rx). Decide If You Will Incorporate Rx Change
When you perform a refraction over the contact lens (Over-Rx), assess if it yields any significant improvement in BCVA, compared to the entry VA, or reduction in undesirable symptoms.
If BCVA improves significantly, it’s an ideal time to recommend changing and getting new lenses. If so, incorporate the power change indicated and if there is any significant residual astigmatism.
If BCVA doesn’t change and the patient is symptom free, then in the wise words of Obi Wan Kenobi, “These are not the droids you seek”. Like the Storm Troopers, you’ll do more good if you leave the RGP alone and don’t make any power adjustments.
Step 5: Lens Integrity and Surface Quality
If a patient presents with lenses where eyesight has deteriorated – along with assessing if their ocular health or pathology has progressed – an important troubleshooting tip is to assess if the problem could simply be related to lens surface degradation. If there’s an issue with denatured protein, mucus or debris build up on the lens, here are some clinical tips:
- Use a peroxide system: most peroxide disinfection systems are suitable for use with RGPs. I like to put all RGP patients on AOSEPT HydraGlyde, rather than a multipurpose solution, for its microbial kill efficacy and protein removal.
- If the RGP still displays significant protein and debris build up, then consider adding an additional protein removal step such as a monthly Progent clean or Ultrazyme.
- Add a daily topical antihistamine eye drop to reduce mucus production from allergies, twice a day (before and after lens wear).
- Consider Menicare spray and/or daily cleaner for daily protein removal of recalcitrant protein deposits.
STEP 6: If In Doubt, Refer It Out!
As with many optometrists in the field, you’ll find most specialty contact lens optometrists are willing to help you as much as they can in order to ensure that every patient gets the best possible care. Developing your skills in slit lamp videography is helpful in strengthening your contact lens fitting skills so you can seek expert advice from specialty contact lens labs and colleagues.
Establishing a good relationship with a specialty contact lens practitioner, that routinely sees challenging cases, is a good way to problem solve. This also helps to determine if, with a little bit of guidance, it is a simple fix.
If you feel that the complexity of a given case is beyond the scope of your expertise and outside your comfort zone, in the patient’s best interests, refer it to a specialty contact lens practitioner.
Margaret Lam is an optometrist in theeyecarecompany practices in greater Sydney and Sydney CBD and an Adjunct Senior Lecturer at the School of Optometry and Vision Science at UNSW. Margaret practises full scope optometry, but with a passionate interest in contact lenses, retail aspects of optometry and successful patient communication and management. She has extensive experience in specialty contact lens fitting in corneal ectasia, keratoconus and orthokeratology, and is a past recipient of the Neville Fulthorpe Award for Clinical Excellence.
Margaret writes ‘mipatient’ on alternate months with Jessica Chi.