Keratoconus gets worse when the cornea’s collagen structure is repeatedly weakened by mechanical, hormonal, or inflammatory forces. The single most controllable factor is eye rubbing, but sleep position, allergies, hormonal shifts, and age all play significant roles in how fast the disease progresses. Progression is typically tracked by changes in the cornea’s steepest curvature point, with an increase of 1.0 diopter or more, or a 2% decrease in central corneal thickness, signaling meaningful worsening.
Eye Rubbing Is the Biggest Controllable Risk
Rubbing your eyes does more damage than most people realize, especially with keratoconus. The mechanical force causes the collagen layers in your cornea to slip against each other, which triggers an immediate restructuring of collagen fibers and weakens the cornea’s overall stiffness. Research from a large Chinese keratoconus cohort found that the duration of eye rubbing directly predicted corneal weakening, and that biomechanical softening occurred before visible shape changes showed up on topography scans. In other words, the damage starts before your doctor can even see it on standard imaging.
The harm goes beyond simple pressure. Rubbing raises corneal temperature, which reduces the tissue’s resistance to bending. It flattens cells, ruptures others, and displaces fluid from the rubbed area. Even in people without keratoconus, studies show that rubbing increases inflammatory enzymes and signaling molecules in the tear film. For someone whose cornea is already structurally compromised, this creates a cycle: rubbing triggers inflammation, inflammation weakens collagen, and the thinning cornea becomes even more vulnerable to the next episode of rubbing.
Vigorous rubbing is also the primary trigger for acute hydrops, a painful emergency where fluid suddenly floods into the cornea through a tear in its inner lining. This complication occurs in advanced disease and can cause permanent scarring.
How You Sleep May Affect Which Eye Gets Worse
One of the more surprising findings in recent keratoconus research involves sleep position. A case-control study found that patients with keratoconus that was significantly worse in one eye were far more likely to sleep on their stomach or side, with the worse eye pressed against the pillow. The association was striking: sleeping on the same side as the steeper cornea carried an odds ratio above 90 in univariate analysis, meaning it was overwhelmingly linked to having more advanced disease in that eye.
The proposed mechanism is straightforward. Pressing your eye into a pillow for hours compresses the globe, raises local pressure, and traps heat against the cornea. Notably, the worse eye didn’t correlate with hand dominance (which would suggest rubbing), but instead matched the preferred sleeping side. If your keratoconus is noticeably more advanced in one eye, it’s worth paying attention to whether you habitually sleep with that eye compressed against a pillow or your arm.
Allergies and Chronic Eye Inflammation
Atopy (the tendency toward allergic conditions like hay fever, eczema, and asthma) is one of the most frequently cited systemic associations with keratoconus. The connection works on two levels. First, allergic eye inflammation floods the tear film with inflammatory signaling molecules and tissue-degrading enzymes. Tear samples from keratoconus patients show elevated levels of multiple inflammatory markers, and the concentration of tissue-degrading enzymes increases in proportion to disease severity. These enzymes actively break down the collagen and structural proteins that hold the cornea together.
Second, allergies make your eyes itch, and itching leads to rubbing. This combination of chemical degradation from inflammation and mechanical damage from rubbing creates a particularly aggressive progression pathway. Managing allergic eye disease with appropriate drops, rather than rubbing, is one of the most impactful things you can do to slow progression.
Hormonal Shifts and Corneal Softening
Hormones play a direct role in corneal strength, which helps explain why keratoconus often first appears during puberty and can worsen during pregnancy. Estrogen and progesterone receptors sit inside corneal cells, and when these hormones bind to their receptors, they alter how the cornea produces and maintains its structural proteins.
Estrogen specifically increases corneal flexibility by stimulating the production of enzymes that break down collagen and by boosting molecules that increase water absorption in the tissue. Lab studies on animal corneas found that exposure to estrogen over seven days measurably increased corneal thickness while reducing stiffness. Case reports have also documented keratoconus progression in patients receiving hormone replacement therapy. Pregnancy, which involves dramatic rises in both estrogen and progesterone, has been associated with worsening in some patients, though not all.
Thyroid hormones have also been implicated in altering corneal biomechanics, though the mechanism is less well characterized than for sex hormones.
Age and the Natural Timeline of Progression
Keratoconus follows a general pattern: it tends to progress most aggressively in the teens and twenties, then gradually stabilizes. Most corneal curvature changes happen within the first 20 years after disease onset. By around age 40 to 45, progression has typically stopped or slowed to a clinically insignificant rate. After about 20 years from onset, corneal curvature measurements tend to remain approximately constant.
This doesn’t mean everyone follows the same timeline. Younger patients, particularly those diagnosed in their teens, face the longest window of potential worsening and are often the strongest candidates for corneal crosslinking to halt progression early. Patients diagnosed later in life generally have a shorter and less dramatic progression course.
Oxidative Stress and UV Exposure
Your cornea sits at the front of the eye, continuously exposed to ultraviolet light, air pollution, and oxygen. This exposure generates free radicals, which are unstable molecules that damage cells and proteins. A healthy cornea has antioxidant defenses to neutralize these molecules, but keratoconus corneas show abnormal antioxidant enzyme levels, higher mitochondrial DNA damage, and a buildup of toxic byproducts from oxidative reactions.
This imbalance means the keratoconic cornea is less equipped to repair the daily wear caused by UV and environmental exposure. The resulting oxidative damage contributes to the ongoing breakdown of collagen cross-links and the loss of structural integrity. While the evidence doesn’t establish a simple “more sun equals faster progression” rule, the biochemical vulnerability is well documented.
Connective Tissue Conditions
Certain genetic conditions that affect collagen throughout the body are associated with keratoconus. Down syndrome is one of the most frequently cited, partly because it also correlates with increased eye rubbing behavior. Ehlers-Danlos syndrome, a group of connective tissue disorders, is another notable association. Keratoconus patients are five times more likely to show joint hypermobility in their hands and wrists compared to the general population, suggesting shared collagen abnormalities. Marfan syndrome and osteogenesis imperfecta round out the most commonly discussed connective tissue links.
If you have one of these conditions, your corneal collagen may be inherently less stable, meaning the same mechanical and inflammatory insults produce more damage than they would in someone with typical connective tissue.
Poorly Fitted Contact Lenses
Contact lenses don’t treat keratoconus or stop it from progressing. They correct vision. But how they fit matters for corneal health. A rigid lens that bears directly on the apex of the cone (called apical bearing) can cause chronic mechanical irritation at the thinnest, most vulnerable point of the cornea. Over time, this leads to scarring and contact lens intolerance. Modifying the fit to distribute pressure more evenly has been shown to reduce the risk of scarring. If your rigid lenses are consistently uncomfortable or you notice worsening haze at the cone’s peak, the fit may need adjustment.