Keratoconus symptoms often first appear in adolescence and then worsen over the next couple of decades. If you were diagnosed with keratoconus in adolescence and chose Rigid Gas Permeable (RGP) contact lenses to correct your vision, cornea pain may not have interfered with wearing your RGP lenses for many years. However, some people who wear RGP – or “hard” – contact lenses develop cornea scarring due to the standard way “hard” (and “soft”) contact lenses rest on the cornea (per the Cornea Research Foundation of America). Furthermore, the progressive corneal thinning that frequently occurs in keratoconus can lead to cornea pain. When wearing RGP contact lenses no longer feels comfortable, scleral contact lenses may be preferable.
The following describes how to prepare to switch from RGP contact lenses to scleral contact lenses, and the differences between them. Additionally described are some symptoms other than nearsightedness and astigmatism that can accompany keratoconus.
What are Scleral Contact Lenses?
While RGP contact lenses are designed to rest on the cornea, scleral contact lens – instead – rest on the white of the eye (termed the sclera). As a larger-diameter RGP contact lens, there is generally a more intensive “learning curve” for someone to become proficient at self-insertion of a scleral contact lens than for other lens types.
However, the American Academy of Ophthalmology (AAOO) notes that one of the benefits of scleral contact lenses is that the purposely-designed space created between a person’s cornea and the back of the scleral lens acts as a fluid reservoir. Moreover, the AAOO specifies that this can potentially provide relief for someone experiencing “dry eyes” or corneal pain as particular symptoms resulting from keratoconus.
Corneal Imaging Techniques – Gauging Whether RGP Contact Lenses or Scleral Contact Lenses are Better for Each Patient
An article in Clinical and Experimental Optometry describes an imaging system in which a camera perpendicular to a slit beam is used to image a portion of the cornea (anterior segment). In this technological system – called the Scheimpflug imaging system – the images are digitized in it, and then the image data is transferred to a computer interface for analysis. Additionally, this article describes the three major morphological subtypes of keratoconus as follows:
- Centered (nipple) cones: This accounts for around 50 percent of keratoconus cases, and is characterized by a cone diameter of 5 mm. or less; the cone is round and positioned centrally or slightly inferior to the visual axis.
- Oval (sagging) cones: Larger in diameter than centered cones, oval cones display either inferonasal or inferotemporal displacement of the corneal apex (thereby increasing the difficulty of of achieving adequate contact lens centration and/or pupil coverage as compared to centered cones).
- Globus cones: As the least common subtype, a globus cone is determined by the existence of a conical area involving at least 75 percent of the entire cornea; this subtype is considered the most difficult in terms of contact lens-fitting due to the need for a larger contact lens diameter, so visualization of globus cones are most likely to result in a fitting for scleral contact lenses.
How Scleral Lenses are Used to Treat “Dry Eyes”
The sensation of having “dry eyes” is common in keratoconus-afflicted people. Scleral contact lenses are designed to hold moisture (with a preservation-free saline solution formula specifically for use with scleral lenses) in their aforementioned reservoir. In this way, scleral contact lenses are especially suited as corrective eyewear in people with persistent “dry eyes” (as noted in an article in Current Opinion in Ophthalmology).
For a keratoconus-afflicted high school or college student, having persistent “dry eyes” can interfere with wearing RGP contact lenses long enough to finish taking notes during a course lecture or answer all of the questions on an exam. In this way, “dry eyes” can significantly interfere with the ability to perform at a high level in an academic environment.
Corneal Pain and Diminished Vision
Myopia and astigmatism are the primary reason for decreased visual acuity in keratoconus-afflicted people, but a scratch on the cornea can result in “hazy” vision that also reduces eyesight. A cornea infection can easily occur as a result of a scratched cornea, and either (or both) of these adverse occurrences can cause corneal pain.
Not only can corneal pain interfere with engaging in normal daily activities, but it can also make driving a motor vehicle a dangerous proposition. By switching away from RGP contact lenses to utilization of scleral contact lenses, the corneal pain may be lessened enough in many people to drive safely again – and, thereby, preserve a greater level of independence.
At the Precision Keratoconus Center, we we want to help you to preserve your eyesight and cope with your other keratoconus symptoms through appropriate keratoconus treatment.