COOKIE magazine recently caught up with Ms. Oh Poh Ling, who specializes in contact lens fitting for keratoconus-affected eyes. She discussed a range of specialty contact lenses designed for irregular or diseased corneas, as well as the fitting process for these lenses.
With keratoconus, characterized by irregular corneal shape, vision can become distorted, and regular eyeglasses may not provide sufficient correction. Moreover, the process of fitting contact lenses for keratoconus patients can be more challenging compared to fitting lenses for individuals with normal eyes.
“The irregular corneal shape requires specialized lenses that conform to the cornea’s contour, providing better vision and comfort,” shared Ms. Oh.
Fortunately, nowadays, there are specially designed rigid corneal lenses, as well as customized soft lenses, which can be used to provide these patients with optimum visual outcomes. “With software-based designing and high customization options available with lenses these days, it is now possible to fit nearly all types and shapes of corneas,” she continued.
Ms. Oh dove into the following contact lens options currently available for keratoconus patients:
1. Scleral lenses
These are large-diameter lenses that vault over the entire cornea and rest on the sclera. These lenses create a space between the lens and the cornea, which is filled with saline solution or, in some cases, eye drops.
“Semi-scleral lenses are typically employed for patients with irregular corneas, such as those experiencing keratoconus. However, they can also be beneficial for individuals with normal corneas who are grappling with dry eye symptoms and find it challenging to wear standard soft or semi-hard lenses. The fluid-filled space between the cornea and the lens created by sclera lenses provides comfort and improved vision for those with irregular corneas,” explained Ms. Oh.
2. Rigid gas permeable (RGP) lenses
RGP lenses are smaller than scleral lenses and offer excellent visual correction for irregular corneas by maintaining a smooth optical surface over the damaged or irregular cornea.
“These lenses are commonly recommended for individuals dealing with mild to moderate keratoconus. Within this classification, they are further categorized into four distinct types: ROSE K2, ROSE K2 nipple cone, ROSE K2 irregular cornea, and ROSE K2 post graft. The specific lens chosen depends on the unique irregularities present in the cornea’s shape. By tailoring the lens selection to match the cornea’s contours, improved comfort and vision are achieved, as the lens can achieve an optimal fit on the cornea,” she summarized.
3. Hybrid lenses
Hybrid lenses have a rigid center with a soft outer skirt. The rigid center corrects the irregular cornea’s shape, while the soft skirt enhances comfort and lens stability.
“Hybrid lenses serve not only patients with keratoconus but also those grappling with high astigmatism and presbyopia, especially when conventional soft or customized lenses prove inadequate in terms of adaptation and comfort. In cases of keratoconus, these lenses offer a dual advantage—clear vision through their rigid center and sustained comfort via the presence of a soft outer ring,” she said.
4. Custom soft lenses
These are specially designed soft lenses made to match the unique contours of the cornea, providing comfort and visual correction for certain cases of corneal damage.
“Tailored soft lenses are designed for individuals with irregular corneas, post-surgical corneal situations, high prescriptions, and presbyopia. They offer versatility across various conditions and prove especially advantageous for addressing irregular corneas or scenarios where standard soft lenses fall short in delivering optimal visual outcomes,” Ms. Oh further explained.
5. Piggyback lenses
These involve wearing a soft lens underneath a rigid gas-permeable lens to enhance comfort, while still providing visual correction for irregular corneas.
“Finally, piggyback lenses cater to individuals with mild to moderate keratoconus as well as irregular corneas. By combining the usage of a soft contact lens atop an RGP lens, this approach offers enhanced comfort and improved clarity of vision for the patient,” she remarked.
6. From fitting to follow up
According to Ms. Oh, in the optometrist center where she works, she has encountered numerous patients with complex corneas. Below, she outlined her treatment process—from the initial evaluation and fitting to subsequent follow-ups.
“The process begins with a comprehensive eye examination and corneal evaluation. Specialized diagnostic tests like corneal topography, keratometry, and corneal pachymetry are used to assess the shape, curvature, and thickness of the cornea. This helps in understanding the extent of corneal irregularities or damage,” Ms. Oh began.
“Based on the evaluation results, we will then determine the appropriate type of contact lens for the patient’s specific condition. Factors like the severity of corneal irregularities, tear film stability, and patient lifestyle are considered when prescribing the lenses,” she continued.
The fitting process involves selecting the size and parameters of the contact lenses to ensure they fit comfortably and securely on the eye. For semi-scleral lenses and custom soft lenses, precise measurements of the cornea are obtained to create lenses that are specifically tailored to the individual’s needs.
Ms. Oh shared a case of a keratoconus patient who had been using ROSEK2 lenses (RGP lenses) for an extended period. “Due to the progression of his keratoconus, he has developed an intolerance to these semi-rigid lenses. As a result, we had to transition to semi-scleral lenses, which are particularly suitable for more advanced keratoconus cases. The large diameter of the lens ensures that it rests on the sclera, avoiding contact with the sensitive and irregular corneal surface, thus providing better comfort and improved vision,” she said.
After the delivery of the lenses, Ms. Oh would schedule regular follow-up visits with her patients to monitor the progress and make any necessary adjustments to the lenses, if any. This helps ensure the contact lenses are providing optimal vision correction and comfort.
Ms. Oh also noted that patients with severe corneal diseases or irregularities may require multiple fittings or a combination of different lenses to achieve the best results. In such cases, close collaboration between the optometrist and the patient is essential to address any challenges that may arise.
Editor’s Note: This article was published in COOKIE magazine Issue 13.
