The cornea, the transparent, dome-shaped outer layer at the front of the eye, plays a significant role in focusing light onto the retina for clear vision. It acts as the eye’s outermost lens, bending light rays to help create a sharp image. When this normally clear structure becomes clouded, a condition known as corneal haze can develop, impacting vision.
Understanding Corneal Haze
Corneal haze is a clouding of the cornea, which normally maintains transparency due to the organized arrangement of collagen fibers within its thickest layer, the stroma. Haze signifies a disruption in this precise structure.
The physical changes involve the disorganization of collagen fibrils and the formation of scar tissue within the corneal stroma. Activated stromal keratocytes, typically transparent, can transform into myofibroblasts. These opaque cells produce a disorganized extracellular matrix. This altered matrix scatters light rather than allowing it to pass through clearly, leading to the cloudy, milky, or ground-glass appearance characteristic of corneal haze.
Common Causes and How It Appears
Corneal haze can arise from various factors, often stemming from the eye’s healing response to injury or disruption. Post-surgical complications are a common cause, particularly after refractive procedures like Photorefractive Keratectomy (PRK) or certain types of LASIK, where the cornea’s surface is intentionally altered. This haze results from the eye’s natural wound healing process, involving inflammation and the production of new, sometimes disorganized, collagen.
Trauma or injury to the eye, such as scratches, abrasions, or chemical burns, can also lead to corneal haze. When the corneal epithelium or deeper layers are damaged, the repair process can result in scarring and opacification. Infections, including bacterial, viral, or fungal keratitis, trigger an inflammatory response that can cause corneal tissue damage and subsequent haze.
Inflammatory conditions affecting the eye, even those not directly infectious, can similarly contribute to haze formation. Certain underlying corneal diseases, such as keratoconus or inherited corneal dystrophies, can also predispose individuals to developing haze over time due to their impact on corneal structure and clarity. To the patient, corneal haze often appears as blurred or hazy vision, a sense of looking through a foggy window, or seeing halos around lights, especially at night. Other symptoms can include glare, increased sensitivity to light (photophobia), reduced contrast sensitivity, and sometimes eye pain or a foreign body sensation.
Diagnosing and Managing Corneal Haze
Diagnosing corneal haze typically begins with a comprehensive eye examination by an eye care professional. A primary tool is slit lamp biomicroscopy, which allows the clinician to examine the cornea’s layers in detail and assess the extent and depth of the haze. This examination helps differentiate superficial haze from deeper stromal involvement.
Further evaluation often includes corneal topography, a non-invasive test that maps the surface curvature and elevation of the cornea. This technology creates color-coded maps that can reveal irregularities in corneal shape, which are not always visible through a standard slit lamp exam, and can help monitor the progression of conditions like keratoconus. Some advanced systems, like Scheimpflug cameras, can also measure corneal thickness and densitometry, providing a quantitative assessment of the haze.
Management of corneal haze is tailored to its specific cause and severity. For inflammation and scarring, steroid eye drops are frequently prescribed to reduce the inflammatory response and minimize scar tissue formation. Nonsteroidal anti-inflammatory drug (NSAID) drops may also be used, sometimes in combination with steroids, to manage pain and inflammation. Lubricating drops can help with discomfort and support ocular surface healing.
In cases where haze is superficial and affects vision, laser procedures such as Phototherapeutic Keratectomy (PTK) can be performed to remove the cloudy tissue. PTK uses an excimer laser to precisely ablate the scarred corneal layers, aiming to restore clarity. For more severe or deep-seated haze, or if other treatments are ineffective, surgical interventions like a corneal transplant (keratoplasty) may be necessary. This procedure involves replacing the diseased or damaged cornea with healthy donor tissue. Early intervention and ongoing monitoring are important to manage corneal haze effectively and preserve vision.
Reducing Your Risk
Minimizing the risk of developing corneal haze involves adopting practices that protect the eyes from injury and infection, and diligently following medical advice after eye procedures. Wearing protective eyewear is an effective measure, particularly during activities that pose a risk of eye trauma, such as sports, home improvement projects, or working in environments with airborne debris. Safety glasses or goggles can shield the cornea from direct impact or chemical splashes.
For individuals who wear contact lenses, proper hygiene and care are important to prevent infections that can lead to corneal haze. This includes washing hands before handling lenses, using fresh solution, and adhering to the recommended wearing schedule and replacement frequency. Promptly addressing any discomfort or redness associated with contact lens wear can also prevent complications from worsening.
Following all post-operative instructions meticulously after eye surgeries, especially refractive procedures like PRK, is a significant preventive step. This often involves using prescribed eye drops, attending follow-up appointments, and avoiding activities that could disrupt the healing process. Seeking immediate medical attention for any eye injuries or suspected infections can prevent minor issues from escalating into conditions that cause corneal haze. Regular eye examinations are also recommended for early detection of any underlying conditions that might increase the risk of corneal haze development.