TODAY'S presbyopia patients face many visual challenges. Corneal GP lenses have an advantage over soft, hybrid, and scleral lenses in that they are free to move more on the eye. Due to this factor, corneal GP multifocals can be designed with segmented zones that separate distance, near, and intermediate add powers.

Translating GP multifocals have some additional lens parameters that can be adjusted to customize them depending on the fit and patient experience. These include segment height, prism ballasting, and truncation. These lenses are meant to be free from the upper lid; in these cases, a lid-attached design is undesirable. Rather, the goal now is to stabilize the lens on the lower lid.

TIP #1

Ideal candidates for translating GP multifocals are patients whose lower lids are at or just above the lower limbus.  This allows the lens to stabilize and helps align the segment to the desired location.

The segment lines separate the zones of power in translating designs. These can be bifocals, trifocals, or even progressive multifocals. These segments can be achieved with streaks, straight lines across the width of the lens, or crescents (i.e., sloping curved sections following the contour of the pupil). Each design’s fit guide has a recommended location for the seg lines.

TIP #2

The seg height can be increased to raise the segment up from the bottom of the lens if the segment is below the desired position, or decreased if the seg is too high (Figure 1).    Patients will often report blur at distance if the segment is too high. These are often small changes, around 0.2mm to 0.5mm.

TIP #3

Translating GPs should be able to move freely along the surface of the cornea or, in other words, translate.  Fit guides often recommend a flatter base curve selection. Translation can be assessed by having the patient look down and seeing if the upper lens edge reaches the upper limbus.

TIP #4

Sometimes an unstable lens can drop below the lower lid.  This may be an indication that the truncation should be increased. This can be particularly problematic for patients who have poor lid tonicity, ectropion, or high-minus prescriptions in which the thickest part of the lens is the edge. Truncation is a technique used to adjust a lens’s center of mass. GP multifocals can be ordered with two diameters: a vertical and a horizontal (e.g., 9.8mm by 9.5mm). In this example, there is a 0.3mm piece left off the bottom of the lens.

TIP #5

Prism can be utilized to stabilize rotation of the lens on the lower lid and also affect the center of gravity.  Base-down prism is particularly useful when translating GPs exhibit superior decentration. After ensuring the base curve is appropriately steepened, increasing prism in the lens can provide faster drop if there is still any remaining lid grab. This can improve distance vision if the patient reports fluctuation.

Consider these tips and consult with your lab the next time patients are seeking a better visual experience with their contact lenses. Translating GPs are highly customizable, which can lead to optimal visual performance for patients.