L and T

Jan
2007

Get Going With Goggles





As vision professionals, when we’re are asked about what products we recommend for recreational activities, the first things that often come to mind are sunglasses. But when was the last time you thought first about goggles? Whether you’re skiing, swimming, cycling or just plain shooting hoops in the driveway, many new and specialized goggles are now available for sports and recreational-specific activities. Like choosing the appropriate clothing for the weather, selecting the appropriate goggle and eyewear for your favorite recreational pursuit is not only important for protecting your vision, it’s essential to maximize your performance and enjoyment.

We are fortunate because goggle technology has kept improving and the result is a bonanza of terrific products to choose from. To ensure an optimally suited and tailored choice, I recommend considering four things when dispensing goggles:
    1. Impact protection
    2. Exposure protection
    3. Vision/acuity enhancement
    4. Activity-specific consideration
Let’s begin with a general discussion of each of these items.

1. IMPACT PROTECTION
Recreational and sports activities often involve a degree of potential of eye or face impact. But the impact exposure contains energy and forces that surpass the design of eyewear that meets only the conventional ANSI (Z80) standard. Therefore, dress eyewear and even eyewear that meets occupational standards (ANSI Z87) will probably not be sufficient. These standards are primarily concerned with lensimpact resistance (both standard and high velocity). We need to consider lens retention as equally important.

Alongside these two lens-based considerations is the question of distributing and dissipating impact energy to the facial and bone structure surrounding the eye. Here, particularly with respect to racquet sports, eyewear that meet the additional protection standards (such as those from the ASTM F803-88a) is mandatory.

2. EXPOSURE PROTECTION
Exposure to wind, rain and snow can significantly impact a person’s vision. Beyond just UV, blue-light and bright-sunlight protection, we must protect the integrity of the eye’s precorneal tear film. Primarily from experience with LASIK and other refractive surgeries, we now know a stable, properly functioning precorneal tear film is essential to a client’s subjective impression of good vision and acuity. Recreational eyewear, therefore, must fit the orbital structure of a person’s face optimally, providing not only a comfortable fit, but also allowing proper air and wind management for the activity under consideration. Too much wind seal may result in fogging, while too little may allow too much tear film evaporation. And beyond the specific activity being considered, your client’s individual susceptibility to dry eye must also be taken into account.

3. VISION/ACUITY ENHANCEMENT
In addition to the full UV absorption expected of eyewear for recreational use, the selection of tints (hue and density) appropriate to the activity must be made. Many of the sports-specific goggles and sunwear from the major manufacturers contain well-tested tint recommendations for specific uses. Hues and densities should not only be chosen with respect to the intended purpose, they may also need to be trial-tested on the patient. In this way, hues that will be either complementary or conflict with a client’s individual color preference will become obvious. In some cases, you as the vision professional may have to discover whether a patient’s color habit (color preference based on familiarity and usage over time) should be noted. Additionally, achieving maximum acuity and vision enhancement requires understanding how the benchmark of 20/20 vision correction may not be sufficient for optimal distance acuity outdoors. To better comprehend this point, consider this example:

The testing distance for 20/20 vision is, by definition, 20 feet. Did you know that the 20-foot testing distance inherently under-corrects your full distance vision by 0.16D? (20 feet = 6.1meters; 1/6.1m = 0.16D). And while ANSI Z80 tolerance standards have proven to be reasonable and workable for most indoor-use eyewear, they currently allow a power tolerance of plus or minus 0.12D. If a client’s 20/20-determined Rx gets combined with a weak-side of tolerance fabrication, they could end up with their distance focus off by over 0.25 diopters. This is important to know since we may perform an Rx compensation to allow for non-standard vertex distances (closer than normal) and/or face-form angle (“wrap”) for goggles and recreational eyewear. Whether it is you or your lab that may make these compensations, the ultimate success and client satisfaction is founded upon a “fully” optimized distance correction. This is the starting point for any pair of “high-definition” recreational eyewear and Rx goggle.

4. ACTIVITY-SPECIFIC CONSIDERATIONS General sport and recreational eyewear should handle differing lighting conditions, offer superior central-gaze acuity, and feature lenses that are virtually shatter-proof. Some specific activities, however, will have their own set of specific needs. Take cycling for example. Bicyclists and motorcyclists have very different head postures for their riding activities. Bicyclists often have their head down and forward to minimize wind resistance. This means the bicyclist’s visual axis is through the upper portion of a lens whose pantoscopic tilt is more severely angled than conventional eyewear. A motorcyclist’s riding posture can be just the opposite. Their head may be tilted up and back, making the visual axis intersect nearer to the bottom of the lenses and often at zero (or reverse) pantoscopic angle. The fit and fabrication of recreational goggles and eyewear for these people will be properly optimized if we consider these activity- specific differences during the selection and measurement process.

We’ll discuss more activity-specific considerations within our analysis of the other recreational activities. Let’s begin our review of activities with skiing.

SKIING
Skiing employs the use of conventional sunwear frames as well as snow goggles. Because of their large surface area on the face and excellent wind seal, goggles are often the preferred eyewear product. But since many snow goggles do not allow for comfortable addition of Rx eyewear underneath, skiers often choose the “Rx insert” positioned behind the goggle’s plate to provide their distance correction. These inserts often hold the lenses at a pantoscopic angle and vertex distance position that may not require Rx compensation, but each fitting situation should be analyzed separately.

Ideally, all insert lenses should be made from either polycarbonate or Trivex, a highly impact-resistant material made by PPG Industries and offered under different brand names by a number of lens manufacturers. The advantage of adding an AR coating may be offset against a non-AR lens’ treatability with a fog-preventative product. For those skiers who prefer the non-goggle approach, many “shield” types of eyewear are available that either provide Rx inserts or can have the Rx lenses ground and mounted within the “plate” itself. Other companies offer a marriage of the best qualities of goggle, shield and eyewear that avoids the Rx insert’s “lookingthrough- two-lenses.” By combining a wraparound eyewear frame, factory-mounted, Rxcompensated lenses and detachable, foam-sealed “moisture-chambers,” the eye’s natural tears (and supplemental eye drops) will not evaporate so quickly. For goggle and wrap-around sunwear, lens-tint choices should include any blue-blocking or blue-scatter-reducing hues, with or without additional reflective finishes, for ideal protection and acuity enhancement. Typical lens colors recommended for skiing include yellow, gold and brown/amber, vermilion/ rose and medium gray (Note: dark gray tints and polarizing lenses may reduce the visibility of moguls—subtle undulations in the surface of the snow). Photochromic lenses are especially useful for all-day/dusk enjoyment on the slopes, without the inconvenience of having to change out lenses or shield plates.

SWIMMING
Swimming has its own set of vision and activitybased considerations that separate it from most other recreational activities. The comfort and efficiency of the eye-orbit seal is paramount, since very little air-exchange will occur. Swim goggles are made from materials treated for fogresistance for this reason. Exposure considerations include reducing the constant contact with chlorinated, salt and even fresh water, which will upset a swimmer’s cornea and tear film. Patients who prefer to wear contact lenses should be advised to use disposables for swimming purposes, along with a “plano” goggle. However, because of the increased risk of infection when swimming with contacts, it is recommended to use corrective swim goggles as the preferred approach. Pre-made Rx swim goggles are available from a number of companies. Prescriptions for most swim goggles do not require an Rx compensation—since the plane of the lenses is fitted with very little face-form (wrap) angle. However, because all pre-made goggles are assembled for each eye from spherical-powers only, you should be familiar with computing the spherical-equivalent of a sphero-cylindrical prescription. To compute the spherical equivalent of an Rx containing cylinder power, take half of the cylinder power and add it to the sphere power. (Note: Always respect the signs of the sphere and cylinder powers when performing this simple arithmetic.) For example:

Rx: R -1.00 -2.00 x 90 = sph. equiv. = -2.00 sph.
      L+1.00 -2.00 x 90 = sph. Equiv. = 0.00
      (plano) sph.

When your computation yields a sphere power that is not available, be sure to always select the next sphere power that is less, not more than the computed power. Since swimmer’s vision is often more concerned with acuity primarily for the ranges of 10 to 15 feet, this should not present any problems. Rx computation for swimming is one of the only recreational activities where full distance correction is not always needed, nor desirable. If anisometropia exists, select spherical powers for each eye that most closely match the dioptric difference between the eyes. Some trials with different goggles may need to be done in office to determine an acceptable compromise. Most premade swim goggles feature lenses that are 30 to 40 percent tint density. This degree of absorption makes a goggle useful under a variety of indoor and outdoor conditions.

For discriminating patients or those with significant astigmatism, custom made-to-order goggles are also available. LT


Barry Santini is a New York State optician based in Seaford, N.Y.

 

|