As patients mature and their presbyopia matures along with them, the optical management of their ametropia becomes increasingly complex. Navigating the available options can be overwhelming for patients and practitioners alike. Most of these optical tools, especially in contact lenses, incorporate rotationally symmetric optics. This same rotationally symmetric optical principal applies to the primary method of compensating for the near-vision requirements in the presbyopic population—that of simultaneous vision (Figure 1); simultaneous vision presents both distance and near optics to the eye within the pupil at the same time (Figures 1 and 2). This increasing optical complexity is magnified in those patients who have astigmatism, especially for those who desire contact lens correction.
Contact lens correction of astigmatism and presbyopia can be separated into two main groups: 1) contact lens options that correct astigmatism, specifically corneal astigmatism, by their inherent non-flexing nature (i.e., GP materials); and 2) those that manage astigmatism within the optics of the lenses themselves (i.e., soft lenses).
GP lenses are best for patients whose corneal toricity is responsible for their refractive astigmatism. Options include aspheric corneal GPs, translating corneal GPs, hybrid multifocals, scleral multifocals, and orthokeratology.
When deciding whether a GP lens is appropriate for a patient requiring presbyopic correction, first analyze whether the corneal astigmatism matches/aligns with the refractive astigmatism. Do this by comparing the amount of corneal toricity to the refractive astigmatism (at the plane of the cornea). If they match, a GP lens may be an excellent option. Note: for patients who have a significant amount of regular/symmetric corneal astigmatism, a bitoric multifocal corneal GP may be an excellent option.
For patients whose vision is compromised by irregular corneal astigmatism, a GP lens is optimal. However, be cautious when adding complex multifocal optics to their already compromised visual system.
Soft Lens Options
With soft lenses, the astigmatic correction needs to be added to the lens itself, which instantly makes the lens non-rotationally symmetric (i.e., toric). Options include soft toric aspheric multifocal lenses and soft toric monovision.
The simultaneous optics in soft lenses are separated into three main categories: aspheric center-near, aspheric center-distance, and concentric (Figure 2). The designs all rely on presenting the specified optical profile within the pupil; the visual result will depend on the size of an individual’s pupil as well as the centration of the lens.
These lenses are made-to-order and typically not found in diagnostic sets due to the complexity of incorporating the multifocal optics and toricity into the lenses. Prior to ordering trial lenses, it is imperative to understand your patients’ refractive error at the plane of the cornea, pupil size, central K value, visible iris diameter, and visual expectations.
If you understand why you should initially select a specific modality based on your patients’ individual ocular profile and refractive error, you will be better able to navigate the complexities of presbyopia-correcting contact lenses. CLS