BCLA CLEAR interactive feedback: Evidence-based contact lens practice 1 – contact lens fitting

We previously published an interactive CPD activity based on two patient cases inspired by the BCLA CLEAR series, specifically the Evidence Based Contact Lens Practice (EBP) report.

Here, we provide a summary of our discussions.

Case 1

A 30-year-old patient attends for a new contact lens fitting. She works in an office-based role, with around five to six hours of daily VDU use at work plus several hours spent looking at a smartphone. Refractive error is R -2.00 DS L -1.75/-0.75x95. She would like soft daily disposable contact lenses for infrequent wear, approximately once every week.

She has previously worn contact lenses, but tells you she suspended wear for three years, but does not explain why. You begin to run through the contact lens fitting process and find the slit lamp examination to be unremarkable. You start taking baseline measurements for lens selection, but the patient questions whether it is necessary to undergo so many different tests.

1. Based on the information available, when would you expect to recommend a daily, two-weekly or monthly, or an alternative replacement frequency lens? Please provide your reasons for your choice and any reasons for not choosing alternatives.
2. When calculating a first-choice lens, in this particular case, would you take the back vertex distance into account? At what point must you do so?
3. Would you consider fitting this patient with a toric contact lens? Provide reasons for your decision.
4. Which baseline measurements do you feel are necessary for soft contact lens fitting and why?

Discussion

• The patient specifically requested a soft daily disposable lens, in the absence of any obvious contraindications it would seem correct to honour the patient’s choice. The CLEAR EBP article highlights that evidence-based practice is comprised of clinical judgements, expertise, experience, of best research and scientific evidence, but also patient values, preferences, and needs. Also, the GOC’s standards of practice for optometrists and dispensing opticians remind us to ‘listen to patients and ensure they are at the heart of the decisions made about their care’. Having said that, some further questioning about the reasons why the patient abandoned CL wear for three years may be warranted. Also, it is important the patient makes an informed decision and so describing the other options, including pros and cons would be helpful.
• Daily disposables are a good choice especially if part of why she previously stopped contact lens wear was linked to convenience. Daily disposable contact lenses have been reported to have around half the number of compliance steps when compared to reusable lenses and in compliant wearers are linked to lower risk of complications. Careful questioning and discussions should include whether the patient has any desire to sleep/nap in lenses and the associated risks/benefits. Lens options that are licenced for these purposes with high oxygen performance materials should be discussed and may result in her preferring to go for a reusable lens. If part of her previous issues were linked to handling, then discussing lens materials with better shape retention and a higher modulus including rigids and sclerals may be advisable.
• While there will be exceptions, the CPD article indicated that for prescriptions under 4D the difference in power between the corneal and spectacle plane is likely small and so spectacle power could be used as a starting point. BVD is, however, a useful measurement. With any lens it is important to check the visual status and to conduct an over refraction.
• Regarding the use of a toric lens even though the cylindrical error is small and unilateral, best practice with soft lenses is to prescribe toric lenses for cyls from 0.75D, to maximise visual performance. Further, the patient could be left eye dominant and this could help prevent binocular vision issues. Demonstrating the difference between the spherical equivalent and toric lens to the patient can be advantageous. It is for the patient to weigh up factors such as cost etc, rather than us making that choice on their behalf. This case does, however, appear to be borderline. Understanding the purpose of the CL wear may help with decision-making, possibly taking account of the VA and other objective tests, but subjective tests are perhaps most useful. For example, the use of questionnaires, particularly at follow ups, to understand overall comfort and/or satisfaction with the lenses and vision.
• Many soft contact lens properties affect performance. With respect to the specific biometrics, we would recommend following clinical conventions for baseline data. Although there is little evidence to support some baseline tests, such as vertical visible iris diameter, even this measurement may be relevant in some cases, eg lens induced ptosis or if, in the future, switching to rigid corneal lenses. An ideal measurement for contact lens fitting is sagittal height, although given many lens suppliers do not typically provide the relevant measurements for their lenses, we would need to use other existing conversion tables to factor in this property.
• The case also reminds us of the importance of having conversations about contact lens wear. Often, the main cause of contact lens dropout amongst established wearers relates to comfort; yet the majority of these individuals can be successfully refitted. The BCLA CLEAR report on Evidence Based Contact Lens Practice suggests reviewing the evidence, considering patient needs, and applying clinical expertise to identify alternative options.

Case 2

You fit a 41-year-old patient with soft toric single vision lenses. VA with habitual spectacle correction was 6/6 for both eyes and the patient could see N5 at 45cm. Following application of the trial lenses, the patient complains of blur, yet you still record 6/6 with both eyes although she struggles to see N5 at near.

1. How would you ascertain the cause of the patient’s complaints?
2. You proceed to checking the lens fit, what specific observations do you routinely make and how would you record these?
3. Are there any additional slit lamp observations you would make, other than those relating to lens movement?
4. What are your management options?

Discussion

• Ask if blinking clears vision. Over refraction may provide further clues. As the patient is having problems at near, the patient may be over-minused/under-plussed. Check the lens fit, specifically signs of misalignment. Check the lens surface for debris, wetting.
• This case could be one of uncorrected presbyopia and asking whether holding reading material at a slightly longer working distance helps, and questioning the influence of the lighting, would provide useful information. It is worth remembering that the demand on accommodation and convergence can change when switching from glasses to contact lenses; with contact lens wear increasing accommodative demand in myopes compared to glasses.
• Understanding visual performance during the patients’ everyday activities, rather than just assessing high contrast visual acuity, including taking account of her habitual near working distances will provide us with additional insights. With toric lenses, variable vision may also be present when looking away from the primary position of gaze.
• As per the original article, observe the lens surface (wettability and quality); centration and comfort; post blink movement; horizontal lag; push up test. For toric lenses, assessments of the marker in both the primary position and during different directions of gaze is useful. Physically rotating the lens can also help ascertain rotational stability to judge the recovery of the toric marker back to the starting position. It is important to also check the ocular surface health and adnexa.
• Dependent on the findings, perhaps adjust fitting and/or compensate for any marker rotation (using CARS/LARS). Consider the over refraction. Consider early presbyopia, measure accommodative facility, working distances and typical near vision tasks and management of any additional findings such as dry eye.

We are sure you were able to come up with additional discussion points of your own. While the CPD window has passed. All Optician summaries of the BCLA CLEAR papers can still be accessed online at opticianonline.net/cpd.