When fitting aphakic infants, there are certain properties that must be present when choosing the right contact lens. First, a lens should offer maximum oxygen permeability. This is important because infants spend most of their time sleeping and aphakic lenses are very thick. Second, lenses should come in high plus powers and steeper base curves to accommodate the frequent changes in power needed due to the fast growth of infant eyes. Third, the lens needs to be durable and easy for parents to handle. Fourth, medications must be able to be placed over the lens because it will be worn during the postoperative time while the eye is healing. Finally, the lens must be easily produced because lost lenses are most likely inevitable (Sclafani, 2006). The types of contact lenses that are available to fit pediatric aphakia include hydrogel and silicone hydrogel (SiHy) lenses, silicone elastomer lenses, and GP lenses.
Hydrogel and SiHy Lenses
Hydrogel lenses are offered in a wide array of parameters including the high plus powers needed to fit pediatric aphakes. One issue with hydrogel lenses, compared with other materials, relates to oxygen transmissibility. The high plus power of aphakic lenses results in increased center thicknesses, thereby giving a low oxygen transmissibility (Dk/t) value (Sclafani, 2006; Lindsay and Chi, 2010; Polse et al, 1978). Dehydration of hydrogel lenses is also a concern because high plus lenses on aphakic eyes may lose several diopters of power when this occurs (Fatt and Chaston, 2013).
Custom SiHy lenses are becoming increasingly more popular. These lenses are also available in a wide variety of parameters and offer a Dk that is higher in comparison to hydrogel lenses (Sweeney, 2013). Both lens types can be made with ultraviolet (UV) protection.
Silicone Elastomer Lenses
Silsoft by Bausch + Lomb is the only silicone elastomer lens available for pediatric aphakia. Its main advantage is its high breathability; it is considered a hyper-Dk lens (Dk of 340) and is approved by the U.S. Food and Drug Administration for up to 30-day extended wear.
The lens can be evaluated with fluorescein, and its increased modulus makes it feel more rigid. This rigidity can provide better optics in comparison to other soft lenses (Cutler et al, 1985; Aasuri et al, 1999; de Brabander et al, 2002).
Silsoft has a wettability treatment on the surface that is easily removed after a few weeks of wear. Once this occurs, the lens needs to be replaced because the deposits are difficult to remove and make the vision cloudy (de Brabander et al, 2002). The base curves range from 7.50mm to 8.30mm, and it has two diameters of 11.30mm and 12.50mm. The power ranges from +12.00D to +32.00D and goes in 3.00D steps after +20.00D. This lens is not offered with UV protection (Bausch + Lomb, 2015).
GP lenses are a good choice for fitting pediatric aphakia because practitioners have complete control over lens parameters and the optics are excellent. For example, a spherical lens can mask several diopters of both regular and irregular astigmatism. GP lenses have good oxygen transmissibility and can be made out of any high-Dk material.
Other benefits include that the rigid material is considered easier to handle because the lens does not fold over while trying to apply or remove it (Sclafani, 2006; Lindsay and Chi, 2010). Both corneal and scleral GP lenses are good options for fitting pediatric aphakia. Scleral lenses are initially very comfortable due to their large size and ability to vault over the cornea (van der Worp et al, 2014). All GP lenses can be made with UV protection.
There are a variety of contact lens choices for fitting aphakic pediatric patients. Becoming familiar with all of these options will aid in the success of treating this population. CLS
For references, please visit www.clspectrum.com/references and click on document #255.