What Is Keratoconus? Symptoms, Treatment, and Surgery

Keratoconus is an eye disease characterized by progressive thinning of the cornea and its forward protrusion into a cone-like shape. It manifests with blurred vision, light scattering, and frequent changes in eyeglass prescription. Early diagnosis is critical for controlling its progression.

Symptoms of keratoconus include increased sensitivity to light at night, double vision, increasing astigmatism, and difficulty seeing clearly. The disease usually begins during adolescence and progresses with age. Regular eye examinations are extremely important for early diagnosis and treatment.

Eyeglasses and contact lenses are used during the initial stage of keratoconus treatment. Corneal cross-linking may be performed to stop its progression. In more advanced cases, special rigid contact lenses or keratoplasty surgery may be required.

Keratoconus surgery is considered particularly in patients whose visual function has been severely affected at an advanced stage. Vision may be improved with a corneal transplant or ring implants. Follow-up after treatment and protection of corneal health are important for long-term success.

Keratoconus is a progressive eye disease in which the cornea becomes thinner, assumes a conical shape, and protrudes forward. This structural deterioration prevents light from focusing properly on the retina, causing blurred and distorted vision. It usually begins during adolescence and may progress until the thirties. Its symptoms include frequent changes in eyeglass prescription, difficulty seeing at night, and light scattering. Treatment options include contact lenses, corneal cross-linking (CXL), and corneal transplantation in advanced cases.

Although the cause of keratoconus is unknown, we know that it is not linked to a single factor. It generally develops when environmental factors act as triggers in a person with a genetic predisposition. In other words, if someone in your family has this disease, your likelihood of developing it is higher than normal.

However, genetic predisposition is not the only factor. The most important controllable environmental factor we emphasize is vigorous eye rubbing. Chronic itching, particularly in people with allergies, and the resulting habit of rubbing the eyes continuously and forcefully may apply mechanical pressure to an already weakened cornea, causing the disease to begin or progress more rapidly.

Some important risk factors known to play a role in the development of keratoconus include:

• Family history of keratoconus
• Vigorous and persistent eye rubbing
• Allergic eye diseases, including vernal and atopic conjunctivitis
• Down syndrome
• Ehlers-Danlos syndrome, a connective tissue disorder
• Marfan syndrome
• Sleep apnea

Keratoconus usually begins gradually during adolescence or the early twenties. Although symptoms vary from person to person, certain complaints are commonly encountered during the early stages of the disease.

Common symptoms seen during the early stages include:

• Mildly blurred or hazy vision
• Straight lines appearing wavy, curved, or broken
• Increased sensitivity to light, or photophobia
• Halos or glare around lights, particularly at night
• Frequent changes in eyeglass or contact lens prescription
• Continuous increases in myopia and astigmatism
• Inability to achieve completely clear vision even with eyeglasses

These symptoms become more severe as the disease progresses. Contact lenses may no longer fit the eye properly and may begin to cause discomfort. In the most advanced stages, a painful condition called "hydrops" may develop, in which the cornea suddenly retains fluid, swells, and causes severe vision loss. This condition may heal while leaving a permanent scar on the cornea.

When a patient presents with suspected keratoconus, we perform a comprehensive examination and several specialized tests to confirm the diagnosis and determine the stage of the disease. Early diagnosis is the most important step for starting treatments that can change the course of the disease in a timely manner.

The main methods used to establish a definitive diagnosis include:

• Biomicroscopic examination
• Corneal topography, or corneal mapping
• Corneal tomography
• Pachymetry, or measurement of corneal thickness

Among these tests, corneal topography and tomography are the gold standards for diagnosing keratoconus. These devices produce a detailed, three-dimensional map of the anterior and posterior surfaces of the cornea and measure its thickness at every point at the micron level. This allows the disease to be detected even at a very early, "subclinical" stage when it does not yet cause any symptoms. These maps also provide objective data for monitoring whether the disease is progressing.

Keratoconus tends to progress if left untreated. Over time, it may cause problems that seriously threaten both visual quality and eye health.

The most important of these include:

• Progressive and permanent vision loss
• Corneal scarring, or central opacity
• Acute hydrops, or sudden fluid accumulation in the cornea
• The need for a corneal transplant

A permanent scar in the center of the cornea blocks the passage of light and permanently impairs vision. Contact lenses are no longer beneficial after this stage. This may leave the patient requiring corneal transplant surgery. Our aim is therefore to stop the disease from progressing before it reaches this stage.

When the disease progresses and eyeglasses become insufficient, specially designed lenses are used to provide clearer vision for patients with keratoconus. These lenses mask the irregular shape of the cornea and create a smooth new surface.

The main types of specialized lenses used to improve vision in advanced keratoconus include:

• Rigid Gas-Permeable (RGP) Lenses
• Scleral Lenses
• Hybrid Lenses

Rigid RGP lenses remain stable on the cornea and provide clear vision. Scleral lenses rest on the white part of the eye without touching the cornea, providing both exceptional comfort and excellent vision, even in very advanced cases. Hybrid lenses combine the visual clarity of a rigid center with the comfort of a soft outer edge. These lenses should be selected and fitted by a physician experienced in this field.

Corneal Cross-Linking (CXL) is a groundbreaking treatment that has emerged in recent years and stops the progression of keratoconus. This treatment has been particularly welcome news for young patients whose disease is actively progressing. Its purpose is to strengthen the weakened corneal structure and stop the disease from progressing.

The procedure is based on applying vitamin B2, or riboflavin, drops to the eye, followed by controlled ultraviolet A (UVA) light. This interaction creates new and strong "cross-links" between the collagen fibers of the cornea. In this way, the cornea gains a form of biological armor, becomes stronger, and develops greater resistance.

The main benefits of CXL treatment include:

• Stopping the progression of the disease
• Strengthening the cornea
• Preventing or delaying the need for a corneal transplant
• Having a high success rate

CXL is a turning point in keratoconus management and is a highly safe treatment method that completely changes the course of the disease.

Intracorneal Ring Segments (ICRS) are a surgical treatment designed to improve visual quality by mechanically correcting the conical shape of the cornea. During this treatment, small crescent-shaped rings made of transparent plastic are placed into tunnels created in the middle layer of the cornea, usually with a femtosecond laser.

These rings surround the central cornea and create a stretching effect, helping the steepened cornea assume a flatter, more normal shape. This reduces myopia and irregular astigmatism and improves the patient's visual quality. However, it should be remembered that ring treatment does not stop the progression of the disease. It is therefore generally performed as an additional vision-improving treatment in patients whose progression has stopped or has been halted with CXL treatment.

Corneal transplantation, the most comprehensive procedure associated with keratoconus surgery, offers hope for patients with the most advanced disease when all other treatment methods have proved insufficient. During this operation, the patient's damaged corneal tissue is replaced with a healthy donor cornea.

Corneal transplantation is generally considered a last resort in the following situations:

• Advanced vision loss
• Inability to achieve sufficient vision with contact lenses
• Inability to tolerate any type of contact lens
• Permanent central corneal scarring that obstructs vision
• Severe corneal thinning or risk of perforation

Two main types of corneal transplant surgery are currently performed for keratoconus:

Deep Anterior Lamellar Keratoplasty (DALK): This is a more modern technique. In keratoconus, only the anterior and middle layers of the cornea are usually affected, while the innermost layer, the endothelium, remains healthy. During DALK surgery, this healthy innermost layer is preserved and only the affected anterior layers are replaced. Because the patient's own tissue is preserved, the risk of tissue rejection after surgery is much lower. It is therefore our preferred option in suitable cases.

Penetrating Keratoplasty (PKP, Full-Thickness Transplant): This is the traditional method. During this operation, all layers of the cornea are replaced together. It is performed when DALK is not possible and all layers of the cornea have been damaged.

Recovery after keratoconus surgery requires patience and care. Achieving completely clear vision may take months and sometimes even a year. During this period, regular use of eye drops, attending all follow-up appointments, and protecting the eye from trauma are extremely important for preventing infection and tissue rejection.

The most serious risk during this process is "graft rejection," in which the body identifies the new tissue as foreign and attacks it. It can generally be treated when detected early.

Recognizing the early signs of graft rejection is extremely important. If you notice any of the following symptoms, you should contact your doctor immediately:

• Unexpected redness in the eye
• Increased pain or foreign body sensation
• Sudden or progressively worsening blurred vision
• Extreme sensitivity to light

What kind of change does keratoconus cause in the eye?

Keratoconus is a structural disease in which the cornea becomes thinner and protrudes forward. This deformation prevents light from focusing properly and causes blurred, distorted vision.

What are the early symptoms of keratoconus?

Early symptoms include frequent changes in eyeglass prescription, glare around lights at night, and double vision. As the condition progresses, completely clear vision may not be achieved even with eyeglasses.

What causes keratoconus?

Genetic predisposition, excessive eye rubbing, allergic eye diseases, and environmental factors may weaken the corneal tissue. This plays an important role in the development of keratoconus.

Is keratoconus a progressive disease?

Yes, it usually begins at a young age and progresses over time. Vision deteriorates as the cornea becomes thinner. Early diagnosis and treatment can therefore stop its progression.

How is keratoconus diagnosed?

The diagnosis is established using advanced imaging methods such as corneal topography and pachymetry. These tests map the corneal surface and show the degree of curvature and thinning in detail.

What does cross-linking do in keratoconus treatment?

Cross-linking is a treatment that strengthens the corneal tissue and stops the progression of the disease. A combination of riboflavin drops and UV light is used to strengthen the collagen bonds.

Which surgical methods are used in advanced keratoconus?

Corneal transplantation or intracorneal ring segment implantation may be performed in advanced cases. These methods improve vision while stabilizing the corneal structure again.

Can patients with keratoconus use contact lenses?

Yes, specially designed rigid or hybrid contact lenses can improve visual quality. However, the lens must be selected individually and monitored through regular medical examinations.

What is the recovery process like after keratoconus treatment?

Burning and stinging may occur for several days after cross-linking. Vision becomes clearer within a few weeks, and progression stops as the cornea becomes stronger. Long-term follow-up is essential.

What should be done to prevent the progression of keratoconus?

Eye rubbing should be avoided, allergies should be kept under control, and regular eye examinations should be performed. If diagnosed early, the corneal structure can be preserved and the need for surgery may be prevented.