Contact Lenses with a Customized Fit – Better Vision, Better Comfort
Most people can choose to wear standard contact lenses rather than glasses, but those with an irregularly shaped eye or too much astigmatism may have a problem. Customized contact lenses may be the answer, as they can be adapted specifically to your needs. These lenses are also perfect for those whose regular lenses are too uncomfortable or do not provide sharp enough focus. Custom contact lenses are available in rigid gas permeable (RGP) and soft lenses to provide sharper vision and greater comfort than ever before.
RGP custom lenses
Rigid gas permeable contact lenses generally provide sharper vision than soft contact lenses, especially for those with astigmatism, but some people find them hard to wear. Traditionally, they are designed to have a slight gap between the edge of the lens and the eye for tears to flow underneath and provide more oxygen, but these lens edges can be uncomfortable. Individuals with unusual eye surface shapes will also find it impossible to center RGP lenses correctly, causing discomfort and variable standards of vision. Advanced technology now allows custom lenses to be made to differ from conventional RGP lenses by changing how the eye is measured and how the lenses are designed.
Understanding eye measurements for contact lenses
Understanding how conventional RGP lenses are fitted will help you understand the complexities of custom contact lenses. The curvature of the eye surface, the cornea, is measured using a device called a keratometer, which uses light reflections to determine the steepest and flattest meridians of the eye. The meridians are the axis lines which run through the center of the eye from 9 o’clock to 3 o’clock positions and from 12 o’clock to 6 o’clock and so on. The lens manufacturer will use three measurements – the steepest meridian of the cornea, the curve of the flattest meridian and the orientation of the flattest meridian to apply to the back surface of the conventional RGP lens for best fit. In conventional lenses the back surface has one curve for the central part of the lens (the base curve) and two or more flatter curves in the periphery of the lens. These curves make the lens align to the surface of the cornea and provide the slight edge lifts necessary for tears to flow behind the lens after blinking.
Custom RGP lens measurements are much more complex. The eye is measured using a corneal topographer which measures the eye from several thousand points to form a detailed map of the eye. This map is then used to design a multi-curved lens which exactly conforms to the shape of the cornea. This process ensures a more comfortable fit, especially for those with high degrees of astigmatism or irregularly shaped corneas. Advanced lens fabrication equipment creates smoother curvature changes and the new RGP materials allow more oxygen to pass through to the lens of the eye, relying less on tears pumping beneath the edges. The edge lift can therefore be reduced for better comfort with new custom contact lenses.
Soft custom contact lenses
Custom designs are also available in soft contact lenses. Although they lack some of the vision benefits of RGP lenses, custom soft contacts can correct higher levels of astigmatism and can provide more accurate correction than conventional toric contact lenses. Conventional toric soft contact lenses correct up to 2.50 diopters of astigmatism in increments of 0.50 or 0.75 but custom toric lenses can correct higher amounts of astigmatism and in finer increments of 0.25 diopters for potentially sharper vision.
Who should consider custom contact lenses?
Anyone who is dissatisfied with the vision produced by soft contact lenses but who found RGP lenses too uncomfortable in the past is a good candidate for custom RGP lenses. As they are so individually shaped to fit, they are suitable for those with keratoconus or unusual corneal curvature due to an eye injury or unsuccessful refractive surgery. Custom multifocal lenses are proving a successful treatment for presbyopia and may in the future by used for non-surgical treatment of myopia.
If you are tired of wearing eyeglasses and have been unsuccessful with other lens options, then custom contact lenses may be worth considering. As a guideline, custom lenses cost about double the price of regular contact lenses. Contact your eye doctor to schedule a comprehensive eye examination and discuss the options available.
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