BEFORE FITTING SOFT contact lenses for presbyopia, whether it be for multifocals or monovision, it is customary to check eye dominance so the clinician knows which eye will be more sensitive to blur at distance and which eye will perhaps be more tolerant of pushing plus to aid in near vision. However, what if the patient is monocular and the dominant eye is the only eye the practitioner has to work with?

A SAMPLE CASE

A new 63-year-old female patient presented to the clinic dissatisfied with her vision in her multifocal contact lenses (MFCLs). She had tried three different brands of MFCLs in the prior six months, but none of them gave her acceptable vision. The challenge was that she also had refractive amblyopia OS that was only correctable to 20/200; OD was correctable to 20/25 with a refraction of +5.75 –0.75 x 015 add +2.50.

Upon evaluation of her most recent MFCL, it was easy to see why she was only able to achieve 20/40 vision, as the lens was decentered temporally and barely covered her nasal limbus. A simultaneous vision MFCL is designed under the assumption that the lens will only be successful if the optical center aligns with the patient’s line of sight.

However, a lens placed on the ocular surface is not guaranteed to perfectly center. Soft lenses tend to decenter slightly temporally due to the nasal sclera being flatter compared to the other quadrants (Ritzmann, 2018), and a significant amount of lateral decentration suggests that a lens has inadequate sagittal depth (Lampa, 2021). Misalignment of the CL optics with the visual axis results in haloes, ghosting, and even monocular diplopia.

To help this patient achieve the success that she so greatly wanted, custom multifocals seemed to be a superb option, as everything about the lens can be customized. For success with this specific patient, several customizations were needed. First, she had a horizontal visible iris diameter of 11.3mm, which is smaller than the usual average of 11.6mm to 12.0mm (Young, 1992), and slightly steeper simKs of 45.00D and 45.75D.

A custom base curve of 7.90mm, a diameter of 14.2mm, and a 2.0mm center near add zone with a 3.0mm intermediate zone were chosen for the first empirically ordered lens to compensate for her small photopic pupil size of 2.8mm and mesopic of 3.5mm. All these customizations resulted in notably improved centration of the lens and an outcome of 20/25 distance visual acuity (VA), but with only 20/50 near VA.

Although a cursory glance with the slit lamp suggested that the lens was centered, further evaluation of topography over the lens suggested that the near-center optics were not centered over the patient’s visual axis. The average angle kappa center is ±5°, however this patient had a large angle kappa that was 0.6mm from the pupil, which is not uncommon for hyperopic patients, as they usually possess a greater one (Kumar, 2010). The final adjustment, the icing on the cake, was offsetting the MFCL optics by 0.7mm nasally, which resolved shadowing and improved near VA to 20/25.

As seen in Figure 1, tangential maps taken over a MFCL can illustrate where the optics align. Although this image does not show the eye of the patient in the sample case, it shows very dramatically that offsetting the optics (left side) can allow a MFCL to perform better.

While fit is important with any CL, centration of the multifocal lens is crucial, and the ability to tailor the lens based on each patient’s specific needs helps to guarantee success. By becoming comfortable with custom MFCLs, practitioners can not only better meet the needs of patients, but also develop a dedicated patient following. CLS

References

1. Ritzmann M, Caroline PJ, Börret R, Korszen E. An analysis of anterior scleral shape and its role in the design and fitting of scleral contact lenses. Cont Lens Anterior Eye. 2018 Apr;41:205-213.
2. Lampa M. Soft multifocal contact lens fitting. Contact Lens Spectrum. 2021 Nov;36:12.
3. Young G. Ocular sagittal height and soft contact lens fit. Cont Lens Anterior Eye. 1992;15:45-49.
4. Kumar DA, Agarawal A, Jacob S. Angle kappa may play important role in success of multifocal IOLs. Ocular Surgery News. 2010 May 10.