Keratoconus is a condition where the cornea, the clear front surface of the eye, thins and progressively bulges into a cone-like shape. A healthy cornea has a round, dome-like shape that helps focus light onto the retina. In keratoconus, this weakened structure disrupts the eye’s ability to focus correctly, leading to distorted and blurred vision. The condition affects both eyes, though one is often more affected than the other, and first appears during the late teens or early thirties.
Symptoms and Associated Causes
The initial signs of keratoconus often involve:
- A progressive blurring and distortion of vision that is not easily corrected.
- Heightened sensitivity to bright lights and glare, which can make night driving difficult.
- The perception of “ghost images,” where a single object appears as multiple, overlapping images, or seeing halos around lights.
- Frequent changes in eyeglass prescriptions as the cornea’s shape continues to change.
While the exact cause remains under investigation, keratoconus is linked to a combination of genetic and environmental factors. There is often a hereditary component, with a percentage of patients having relatives with the condition. Chronic and vigorous eye rubbing is strongly associated with the disease, as the physical pressure can weaken the corneal structure. The condition is also linked with systemic diseases like allergies, asthma, and certain connective tissue disorders. A finding in keratoconus is a loss of collagen, the protein that provides strength and flexibility to the cornea.
The Diagnostic Process
Diagnosing keratoconus typically begins during a routine eye examination where initial signs like changing astigmatism or decreasing vision are noted. An ophthalmologist will then perform a more detailed evaluation, often starting with a slit-lamp examination. This involves using a high-magnification microscope to see the cornea in fine detail and identify thinning or other irregularities.
The definitive tool for confirming keratoconus is corneal topography. This non-invasive imaging technology creates a detailed, three-dimensional map of the cornea’s surface. The map uses color-coding to illustrate the curvature and elevation of the cornea, revealing the characteristic steepening and protrusion that defines the condition. Another measurement, pachymetry, is used to determine the thickness of the cornea, as thinning is a hallmark of the disease.
Treatment Approaches
Treatment for keratoconus is tailored to the stage of the condition and aims to correct vision and stabilize the cornea. In the earliest stages, vision problems from nearsightedness and astigmatism can be managed with eyeglasses or standard soft contact lenses. These options work by compensating for the mild refractive errors caused by initial changes in the cornea’s shape.
As the cornea becomes more irregular, glasses and soft lenses lose their effectiveness because they cannot conform to the cone shape. At this point, specialized contact lenses are required. Rigid gas permeable (RGP) lenses are a common next step, as they create a smooth, artificial refractive surface over the warped cornea. Hybrid lenses and scleral lenses, which are larger-diameter lenses that vault over the cornea, are also effective at providing clear vision in more advanced cases.
To stop the disease from worsening, a procedure called corneal collagen cross-linking (CXL) is frequently recommended. This minimally invasive treatment strengthens the bonds between collagen fibers within the cornea. The procedure involves applying riboflavin (vitamin B2) eye drops to the cornea, which is then exposed to a controlled amount of ultraviolet A light. This process creates new links between collagen fibers, making the cornea stiffer and more stable, thereby halting the progression of the bulging.
For a small number of patients with very advanced keratoconus, where contact lenses are no longer sufficient or tolerated, surgical intervention may be considered. One option is the implantation of small, clear arcs called Intacs into the cornea to help flatten the cone shape. In the most severe cases, a corneal transplant (keratoplasty) may be necessary to replace the diseased cornea with healthy donor tissue.
Progression and Long-Term Outlook
Keratoconus begins to manifest during puberty or the early 20s. The condition then progresses for 10 to 20 years, after which it often slows down or stabilizes, usually by the third or fourth decade of life. The rate of progression can be unpredictable and varies among individuals, with younger patients sometimes experiencing more rapid changes.
Although keratoconus can lead to significant visual impairment if left untreated, it does not result in total blindness. The outlook for individuals with this condition has improved substantially with modern treatments. Through proper management, including specialized contact lenses and procedures like corneal cross-linking, the vast majority of people with keratoconus are able to maintain functional vision. Early diagnosis is important to access these therapies and avoid more invasive procedures later.