Keratoglobus is a rare, non-inflammatory eye condition affecting the cornea, the transparent front part of the eye. This disorder causes the entire cornea to become unusually thin and bulge outward in a spherical or globular shape. This widespread thinning and protrusion can significantly affect vision and eye comfort.
Causes and Associated Conditions
The precise origin of keratoglobus is not fully understood. However, a structural weakness within the corneal tissue is thought to contribute to its gradual thinning and bulging. Evidence suggests that genetic factors may play a role in its development.
Keratoglobus is frequently associated with certain genetic systemic diseases, often presenting as a congenital condition, meaning it is present from birth. These associated conditions include Ehlers-Danlos syndrome, particularly type VI, which involves defects in collagen synthesis. Marfan syndrome, another connective tissue disorder, and Leber congenital amaurosis, a severe inherited retinal disease, are also linked to keratoglobus. These associations suggest that underlying systemic issues or collagen abnormalities may contribute to the corneal changes.
Identifying Keratoglobus
Individuals with keratoglobus often experience severely blurred or distorted vision. High myopia, or extreme nearsightedness, is a common symptom, along with irregular astigmatism that is challenging to correct with standard eyeglasses. Patients may also report sensitivity to light or discomfort, and frequent changes in their eyewear prescription. The outward bulging of the cornea might also be noticeable.
An ophthalmologist diagnoses keratoglobus through a comprehensive eye examination using specialized equipment. A slit-lamp examination allows the eye care provider to observe the diffuse thinning and globular protrusion of the cornea. Pachymetry, a technique that measures corneal thickness, provides precise data on the extent of thinning across the cornea. Corneal topography and tomography are advanced imaging techniques that map the curvature and shape of the cornea, revealing the characteristic globular distortion and irregularities.
Differentiating keratoglobus from keratoconus, a more common corneal ectasia, is important due to their distinct characteristics. While both involve corneal thinning and protrusion, keratoglobus typically presents with a generalized, global thinning and spherical bulging of the entire cornea. Keratoconus, in contrast, usually involves a more localized, cone-shaped protrusion and thinning, often in the central or paracentral cornea. This distinction guides appropriate management strategies.
Management and Treatment Approaches
Managing keratoglobus often begins with non-surgical strategies aimed at vision correction and corneal protection. Specialized, large-diameter scleral contact lenses are a primary non-surgical intervention. These lenses vault entirely over the irregular corneal surface, resting on the white part of the eye (sclera), creating a smooth, new refractive surface for light to pass through. This design effectively corrects high myopia and irregular astigmatism, significantly improving visual acuity.
Surgical interventions become necessary for advanced cases or to address specific complications. Corneal cross-linking (CXL) is a procedure used to strengthen the corneal tissue and halt its progression. This involves applying riboflavin eye drops to the cornea, followed by exposure to ultraviolet-A light, which helps create new bonds within the corneal collagen fibers. CXL aims to increase the cornea’s rigidity and prevent further deterioration of its shape.
Corneal transplantation, or keratoplasty, is typically reserved for severe cases where vision cannot be adequately corrected with lenses, or when corneal perforation occurs. Due to the widespread thinning in keratoglobus, a large-diameter penetrating keratoplasty, which involves replacing the entire central and peripheral cornea with donor tissue, is often performed. Newer techniques, such as the “tuck procedure,” involve creating a host pocket at the limbal margin to tuck in a trimmed donor corneo-scleral graft, addressing the peripheral thinning characteristic of the condition.
Living with Keratoglobus
A significant consideration for individuals living with keratoglobus is the extreme fragility of the cornea. The widespread thinning makes the eye particularly vulnerable to injury, necessitating constant vigilance. Even a light bump or accidental poke can potentially lead to severe damage.
Therefore, wearing protective eyewear, such as glasses with polycarbonate lenses, is strongly recommended at all times. This is especially important during sports, physical activities, or any situation where there is a risk of impact to the eyes. These measures protect the delicate cornea from potential harm.
Regular, lifelong monitoring by an eye care specialist is also important to track the condition’s progression. These ongoing check-ups allow for timely adjustments to management strategies, ensuring that any changes in corneal shape or thickness are addressed promptly. Consistent follow-up helps to preserve vision and maintain the long-term health of the eyes.