Definition of keratoconus: The word keratoconus is derived from the Greek and Latin. Kerato means horny and cone means cone-shaped. It is a bilateral, progressive, asymmetric, non-inflammatory thinning and ectatic condition of the cornea, resulting in a high degree of irregular myopic astigmatism.

Predominance: Keratoconus is estimated to occur in 1 in 2,000 people in the general population. There does not seem to be a significant preponderance with respect to men or women.

What is the usual age of onset of keratoconus?

The onset of keratoconus is between the ages of 10 and 30. Changes in the shape of the cornea usually occur slowly over several years.

Symptoms: The symptoms depend on the severity of the disease. The most common symptoms include:

• Blurred vision.

• Distortion of vision.

• Photophobia.

• Flash.

• Irritation and itching in the eyes.

• Frequent power changes of shows.

• Inability to wear contact lenses.

Reasons:

The cause of keratoconus remains unknown, although recent research seems to indicate that possible causes include:

• Keratoconus is thought to involve a defect in collagen, the tissue that makes up most of the cornea.

• Keratoconus has a genetic component and studies indicate that about 8% of patients have affected family members.

• It occurs more often in people with certain medical problems, including certain allergic conditions.

• Some think that chronic excessive rubbing of the eyes can cause keratoconus.

Classification:

(A) Based on keratometry reading:

1. Mild: Keratometric readings are less than 45D in both meridians.

2. Moderate: Keratometric readings are between 45D and 52D on both meridians.

3. Advanced: Keratometric readings are between 53D and 62D on both meridians.

4. Severe: Keratometric readings are on both meridians greater than 62D.

(B) Based on the morphological form:

1. Nipple Cones: Characterized by their small size (5 mm) and great curvature. The optic center is often central or paracentral and displaced inferonasally.

2. Oval Cones: Which are larger (5-6 mm), ellipsoidal and commonly displaced inferonasally.

3. Globus cones: which are larger than 6 mm and can affect more than 75% of the cornea.

Clinical features:

1. Early stage impaired vision in one eye caused by progressive irregular myopic astigmatism with pronounced keratometry reading.

2. Scissor reflex in retinoscopy.

3. Ophthalmoscopically shows an “oil droplet reflex”.

4. Munson’s sign: bulging of the lower eyelid when looking down.

5. Fleischer ring epithelial iron deposits at the base of the cornea. The iron deposition mechanism is not clearly understood. It may be a distribution of tears.

6. Progressive central or paracentral stromal thinning with inferior apical protrusion.

7. Vogt’s striae: deep, fine vertical stromal folds that temporarily disappear with digital pressure.

8. Conical reflection of Rizutti’s sign in the nasal cornea when light is projected from the temporal side.

9. Prominent corneal nerves.

10. Acute hydropes: corneal edema resulting from tears due to rupture of Descemet’s membrane and acute leakage of aqueous humor into the stroma and corneal epithelium. These tears usually heal in 6-10 weeks and the edema gradually disappears.

11. Variable corneal scarring, depending on the severity of the disease.

Associations: Ocular and systemic associations of keratoconus include:

Ocular:

• Spring conjunctivitis.

• Blue sclera.

• Aniridia.

• Ectopia Lentis.

• Retinitis pigmentosa.

• Leber congenital amaurosis.

systemic:

• Down’s Syndrome.

• Ehlers-Danols syndrome.

• Marfan syndrome.

• Atopic dermatitis.

• Imperfect osteogenesis.

Exams and Tests:

• Visual acuity test: Visual acuity is an indication of the clarity or sharpness of vision. It is a measure of how well a person sees.

• Refraction: A refraction test is an eye exam that measures a person’s eyeglass or contact lens prescription.

• Slit Lamp Review: The slit lamp is an instrument consisting of a high-intensity light source that can be focused to shine a thin sheet of light into the eye. Slit lamp examination provides a stereoscopic magnified view of ocular structures in detail, allowing anatomical diagnoses to be made for a variety of ocular conditions such as keratoconus.

• Corneal topography: Corneal topography, also known as photokeratoscopy or videokeratography, is a non-invasive imaging technique for mapping the curvature of the corneal surface. The three-dimensional map is a valuable help. It is also used in the diagnosis and treatment of a number of conditions; in the planning of refractive surgery such as LASIK and evaluation of its results; or in evaluating contact lens fit or diagnosing keratoconus.

Treatment:

Optical:

Sample: In the early stages of keratoconus, the samples often successfully correct myopia astigmatism associated with keratoconus. But in severe cases it does not give a good quality of vision due to the large amount of corneal toricity.

Contact lenses:

1. Soft contact lenses: In the early stages of keratoconus, soft contact lenses are helpful. Because soft contact lenses provide good comfort. But in advanced stages, soft contact lenses cannot correct irregular astigmatism. Therefore, soft contact lenses are not useful in advanced stages of keratoconus.

2. Rigid Gas Permeable (RGP) Contact Lenses: As the condition progresses, the cornea becomes highly irregular and vision is no longer adequately corrected by glasses and soft contact lenses. Rigid gas permeable contact lenses are then required to provide optimal visual acuity. Rigid Gas Permeable Lenses allow jumping over the cornea, replacing corneal irregularities by filling the tears between the cornea (front surface of the eye) and the posterior surface of RGP lenses with a smooth, uniform refractive surface to improve clarity. vision.

3. Piggyback Contact Lenses: Sometimes the ideal fit of a rigid gas permeable contact lens on a cone-shaped cornea is not possible. To get a good fit and a good visual result, some professionals wear contact lenses in tow. This method involves placing a soft contact lens, such as one made of silicone hydrogel, over the eye and then placing an RGP lens over the soft contact lens.

4. Pink-K Lens: The Rose-k lens was introduced by Dr. Paul Rose in 1995. This lens is the most frequently prescribed gas permeable lens in the world for keratoconus. This lens has a complex geometric design. Here are six different curves on the posterior surface of the lens and the decreasing optical zone as the base curve increases. The lens material is Boston.

5. Boston Sclera Contact Lens: In advanced cases of keratoconus to delay surgery, the Boston scleral contact lens is very helpful. It is made of a material that allows the passage of oxygen to the eye, larger diameters (15 to 24 mm), the edges rest on the sclera or white portion of the eye and the central optic zone (12 mm) is designed to completely dome over the eye. irregular horny part in shape These larger lenses are also more stable than conventional gas permeable contact lenses.

Surgical:

Penetrating keratoplasty: In about 15% of cases, keratoconus progresses to the stage where a corneal transplant is required to achieve better vision.

Cross-linking of corneal collagen with riboflavin (C3-R): A new minimally invasive procedure called Corneal Collagen Crosslinking with riboflavin (vitamin B) and ultraviolet-A (UVA 365nm) is called C3-R.

Treatment is performed in the operating room under completely sterile conditions. Usually, one eye is treated in a single session. The treatment is carried out by means of anesthetic eye drops. The surface of the eye (cornea) is treated with the application of Riboflavin eye drops for 30 minutes. The eye is then exposed to UVA light for 30 minutes. The combination of riboflavin drops and ultraviolet light that react with the tissues of the cornea, strengthening them by creating more ‘cross-linking’ between them. The resulting increase in stiffness and stiffness of the cornea stabilizes corneal ectasia. Therefore, the treatment lasts about an hour per eye. After the treatment, antibiotic eye drops are applied; a bandage contact lens can be applied, which will be removed after a few days.

However, it is necessary to understand that collagen crosslinking treatment is not a cure for keratoconus, rather it is intended to slow the progression of the condition. However, after the crosslinking treatment, the patient feels more comfortable wearing contact lenses.

Keratoconus complications:

• Patients with even borderline keratoconus should not undergo laser vision correction. Corneal topography is done before laser vision correction to rule out people with this condition.

• There is a risk of rejection after corneal transplant, but the risk is much lower than with other organ transplants.

When to contact a medical professional?

Youth whose vision cannot be corrected to 20/20 or 6/6 with glasses should be evaluated by an ophthalmologist experienced in keratoconus.

Does keratoconus affect both eyes?

Yes, keratoconus usually affects both eyes. Keratoconus is basically a bilateral condition; the degree of progression of the two eyes is often uneven.

Does keratoconus cause blindness?

Keratoconus does not cause total blindness. However, it can lead to significant visual impairment resulting in legal blindness.

Prevention:

There are no preventative measures. Some specialists believe that patients with keratoconus should receive intensive treatment for eye allergies and should be instructed not to rub their eyes.