Hybrid Hype

Hybrid contact lenses were designed to provide the best features of “hard” and “soft” lenses.^1,2 Hard, or rigid gas permeable (RGP), lenses have a tough plastic design. They retain their shape better than soft lenses and are more durable and longer lasting. Because of these qualities, RGP lenses usually also provide crisper, clearer vision than soft lenses. Although soft lenses lack most of the benefits of RGP lenses, they do have some advantages, namely the fact that most patients find them more comfortable, at least initially, than RGP lenses, and they are typically easier to wear than RGP lenses.^1-3

ENTER THE HYBRID

Hybrid lenses typically pair a hard lens center with a soft skirt. As a result, they provide the easy wear and comfort of soft lenses while delivering the crisp, clear vision of RGP lenses.^3,4 Considering the many different types of contact lenses that are available to manage normal and irregular corneas, it is important to determine which lens design will produce the best result, based on the anterior segment characteristics and visual needs of each wearer.

For normal and irregular corneas, hybrid contact lenses provide the same optical performance as that of RGP lenses except, compared to the latter, hybrids are more comfortable, often exhibit better centration, and are more stable. These advantages are more evident in cases of irregular corneas, as the rigid portion is designed to vault over the corneal irregularity. Hybrids are preferred over soft lenses when the quality of vision is affected by residual higher-order aberrations or when toric soft contact lenses fail to provide stable vision.^5-7

Compared to piggyback lens systems, in which an RGP lens is fitted on top of a soft lens, hybrids are easier to handle, simpler to care for, and provide increased oxygen transmission. Despite the recent increase in the use of scleral RGP lenses, hybrids present some distinct advantages. For example, hybrid lenses allow better tear flow, have lower apical clearance, reduce the “fogging” effect, increase oxygen transmission, and better conform to the scleral shape, thanks to their soft skirt.⁶

A PRIME EXAMPLE

TR, a 58-year-old male, presented in the spring of 2019 for a comprehensive eye examination and specialty contact lens evaluation. He had reported discomfort and dislodging of RGP lenses more than 15 years ago and had then switched to soft lenses for the past 15 years. He complained of reduced distance vision in fluorescent lighting and of discomfort with the lenses after 1 or 2 weeks of wear. He had a history of a retinal detachment in 2009, which was successfully repaired with a buckle and gas bubble. He denied flashes, but reported longstanding, stable floaters for many years.

TR’s VA was 20/20 blurry OD and 20/30+1 doubling OS with his current biweekly replacement soft lenses (Acuvue Oasys, Johnson & Johnson Vision Care). His current soft lenses were OD: -10.00 DS and OS: -12.00 DS. A manifest refraction yielded the following results:

OD: -11.00 -1.00 x 060; VA: 20/25

OS: -14.75 -1.50 x 165; VA: 20/25; ADD: +2.25

TR’s horizontal visible iris diameter (HVID) was 11.20 mm OU and his keratometry readings on corneal topography were 45.66 x 47.09 @ 134 OD and 45.06 x 46.43 @ 056 OS. He was fitted with both scleral lenses and hybrid lenses. TR preferred the hybrid lenses, citing their lower cost, easier handling, and superior comfort compared to scleral lenses.

After the initial fitting appointment, I ordered Duette (SynergEyes) lenses in the following parameters: 7.3/MED/-10.50 DS (OD) and 7.4/MED/-13.00 DS (OS). TR’s VA was 20/20 OU, and fluorescein staining indicated an ideal fit pattern (Figure).

HELPFUL HYBRID POINTERS

Hybrid contact lenses for normal corneas are indicated for correcting low-to-high myopia, hyperopia, presbyopia, and astigmatism (with a similar degree of refractive and corneal astigmatism (ie, a difference < 0.75 D).

Hybrid designs can be fit empirically using keratometry, subjective manifest refraction, and HVID, without the need for a fitting set. An online calculator is available to help with initial lens selection. The base curve should be 0.10 mm or 0.50 D steeper than the flat meridian. The soft skirt curve is selected based on the HVID; a medium (8.1 mm) skirt is used for HVIDs ≥ 11.8 mm and a flat (8.4 mm) skirt for HVIDs < 11.8 mm.

These hybrid designs can be evaluated similar to soft lenses. The goal is good centration and movement. For troubleshooting, the fit is evaluated by placing saline and a few drops of regular fluorescein (high-molecular-weight fluorescein is not required) in the bowl of the lens and immediately checking the pattern. An optimal fit will show good centration with the optical zone over the pupil (Figure), 0.5 mm to 1.0 mm of movement with each blink, and the GP portion in alignment with the cornea.

HYBRID LENSES: A WINNING COMBINATION

Modern hybrid contact lenses, with their improved materials, designs, and 6-month replacement schedules, can be an effective solution for managing not only irregular corneas, but also refractive errors and presbyopia. Patients with astigmatism often experience superior and more stable vision when fit with hybrid lenses than with soft toric lenses,^6,7 and patients with presbyopia and low astigmatism experience better visual quality with hybrid lenses than with soft multifocal contact lenses.^8,9