Monday, March 23, 2015

Scleral Contact lens fitting for the challenging patient

Scleral Contact Lenses


Scleral contacts are large gas permeable (breathable) contact lenses specially designed to vault over the entire cornea and rest on the "white" of the eye (sclera). Scleral lenses functionally replace the irregular cornea with a perfectly smooth optical surface to correct vision problems caused by keratoconus and other corneal irregularities or anomalies. The space between the cornea and the back surface of a scleral lens acts as a fluid reservoir to fill in any irregularity and to provide comfort for people with severe dry eyes who otherwise could not tolerate contact lens wear.


Scleral contacts are significantly larger than standard gas permeable (GP) contacts and have a diameter equal to or greater than that of soft contact lenses. The smallest sclerals are approximately 14.0 mm in diameter, and the larger can be up to 24 mm.

Lenses that are 18 mm or smaller are often sub-categorized as mini-sclerals.





Large-diameter scleral and semi-scleral GP lenses rest on the sclera and vault over the misshapen cornea in keratoconus.

The average human cornea is approximately 11.8 millimeters in diameter, so even the smallest scleral contacts are designed to cover the entire corneal surface.

In comparison, most conventional GP contact lenses are 9.0 to 9.5 mm in diameter and cover only 75 to 80 percent of the cornea.

Another category of gas permeable lenses bridges the size gap between conventional GP lenses and mini-sclerals. These lenses, called corneo-scleral lenses, generally are approximately 13 to 15 mm in diameter.

Corneo-scleral lenses often are a good choice for people who require larger-than-normal GP lenses for greater comfort. They also are frequently used when contact lenses are needed after LASIK or other corneal refractive surgery to correct irregular astigmatism.





The size of lens used often is determined by the degree of complexity of the condition. Milder forms of keratoconus and irregular astigmatism from corneal grafts and refractive surgery often are easily managed with scleral lenses at the smaller end of the spectrum.

Smaller scleral and mini-scleral contacts can be easier to apply, can be less costly and require fewer care products.

More complex conditions, including advanced keratoconus, pathologically dry eyes or severe ocular surface disease that might require a large tear reservoir, often are fitted with larger scleral lenses, as they have more capacity to hold fluid or bridge large changes in corneal curvature.



Many optometrists and ophthalmologists recommend scleral contact lenses for a variety of hard-to-fit eyes, including eyes with keratoconus.

In cases of early keratoconus, a standard GP lens may be used. However, if the lens does not center properly on the eye or moves excessively with blinks and causes discomfort, switching to a large-diameter scleral contact lens may solve the problem.

Because scleral lenses are designed to vault the corneal surface and rest on the less sensitive surface of the sclera, these lenses often are more comfortable for a person with keratoconus. Also, scleral lenses are designed to fit with little or no lens movement during blinks, making them more stable on the eye, compared with traditional corneal gas permeable lenses.


In addition to keratoconus, scleral contact lenses can be used for eyes that have undergone a cornea transplant, and for people with severe dry eyes caused by conditions such as Sjogren's syndrome, graft-versus-host disease (GVHD) and Stevens-Johnson syndrome.

Advances in lens design technology are allowing manufacturers to design scleral lenses that can correct more conditions than ever before, including bifocal sclerals for the correction of presbyopia.







Scleral contact lenses are custom-made for each wearer, so fitting scleral contacts demands greater expertise and more time than fitting standard soft or GP contact lenses.

Often, computerized maps of the curvature of the entire cornea are generated to facilitate the lens fitting, and several trial lenses of different sizes and curvatures may be applied to the eye during the fitting process.

Also, depending on the complexity of the problem and how the individual eye tolerates the scleral lens, adjustments of lens parameters may be needed, which will require additional lenses to be made and exchanged. The entire scleral lens fitting process can take several visits to determine the optimal lens for each eye.

We have had extensive experience here at Farkas, Kassalow, Resnick and Associates. Feel free to call to set up a consultation or for any further information you require.

Dr. Kevin D.Rosin
212-355-5145
www.eyewise.com

3 comments:

lenzaeye said...

A contact lens fitting and a prescription written by a licensed eye care professional are required even if you have no need for vision correction and want only "non-prescription" (plano) colored contact lenses or special-effect contact lenses to change the appearance of your eyes.


https://lenzaeye.com/contact-lenses/contact-lens-fittings/

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Smith Waugh said...

Great read! Scleral lenses are truly transformative in addressing various eye conditions. The article brilliantly outlines the fitting process, shedding light on the comfort and efficacy of these lenses. As someone exploring options for vision correction, learning about the benefits of scleral lenses has been insightful. Thanks for sharing!