The Femto-LASIK procedure

Modern Methods of Keratoconus Treatment: Situation in Armenia

03 March 2016 | KERATOCONUS | Цитата

Keratoconus which was first described in detail in 1854 is a bilateral and asymmetric corneal degeneration characterized by localized corneal thinning which leads to protrusion of the thinned cornea. Corneal protrusion causes high myopia and irregular astigmatism, affecting visual quality. It usually becomes apparent during the second decade of the life.

Signs and Symptoms: The ocular symptoms and signs of keratoconus vary depending on disease severity. Patients with keratoconus often complain of decreased vision, photophobia, monocular diplopia, visual distortion, asthenopia and glare around lights. Usually keratoconus does not normally produce any symptoms and thus can go unnoticed by the patient and practitioner unless specific tests (i.e., corneal topography) are undertaken for diagnosis. Disease progression is manifested by a significant loss of visual acuity which cannot be compensated for with spectacles. Therefore, there should be a suspicion about the presence of keratoconus in any patient with myopic astigmatism whose spectacle prescription is changing more frequently than normal or when a visual acuity of 6/6 or better is difficult to achieve with increasing against-the-rule astigmatism (9).

Management and treatment: Keratoconus management varies depending on the disease severity. Traditionally, incipient cases are managed with spectacles, mild to moderate cases with contact lenses, and severe cases can be treated with keratoplasty. Other surgical treatment options include intra corneal rings segments, corneal cross-linking, laser procedures (i.e., photorefractive keratectomy, phototherapeutic keratoctomy, lasik in situ keratomileusis) intra-ocular lens implants or a combination of these.

Spectacles

Spectacles are normally used in early cases of keratoconus only. As the disease progresses, irregular astigmatism develops and adequate visual acuity cannot be achieved with this type of visual correction .

Contact lenses

Contact lens wear has represented the most common and successful treatment option for early to moderate cases of keratoconus. A study which evaluated contact lens prescribing

trends in 518 keratoconus patients (1004 eyes) over a 30-year period showed that contact lens wear represented a satisfactory treatment method and delayed the need for surgery in approximately 99% of all fittings. Although contact lenses for keratoconus are manufactured with hydrogel, silicone hydrogel, gas permeable and hybrid (i.e., rigid centre and soft skirt) materials, gas permeable contact lenses remain the most commonly used contact lens type (32, 33) as high levels of irregular astigmatism cannot normally be corrected with other contact lens types.

Surgical procedures

Although penetrating keratoplasty (PKP), in which the entire thickness of the cornea is removed and replaced by transparent corneal tissue, is perhaps the most commonly used surgical option for advanced cases of keratoconus which cannot be successfully managed with contact lenses (9,44) its use is limited to a relatively low number of cases.

Deep Lamellar Keratoplasty (DLK), in which superficial corneal layers are removed and replaced with healthy donor tissue has been employed in keratoconus management in recent years. However, eyes undergoing PKP are more likely to achieve 6/6 (20/20) vision than those undergoing DLK (47). On the other hand, a higher risk of endothelial cells loss and graft rejection has been reported with the use of PKP in comparison with DLK (47, 48).

Photorefractive keratectomy (PRK), a technique which permanently changes the shape of the anterior central cornea using an excimer laser to ablate a small amount of tissue from the corneal stroma has been used in the treatment of keratoconus with modest success. Although some studies have reported a significant reduction in cone progression in subjects with early keratoconus (50) as well as an increase in visual acuity and a decrease in high-order aberrations (51) the technique has been frequently associated with the development of ectasias post-treatment and thus, this procedure is not longer commonly used. However, it has been reported that some corneas with inferior steepening on corneal topography should not always represent a contraindication for PRK treatment (52). Other corneal surgical procedures for the treatment of moderate keratoconus include excimer laser-assisted anterior lamellar keratoplasty (53) epikeratoplasty (54)and laser-assisted in situ keratomileusis (54).

The crosslinking method of treatment of keratoconus has been carried out at the Department of Diagnostics and Laser Surgery of Ophthalmologic Center after S. Malayan starting from 2009. This procedure is performed by the Head of the Department, PhD Yelena A. Malayan.

Since then, 1612 eyes were operated. The numbers of surgeries performed annually are the following: 100 eyes during 2009, 136 eyes during 2010, 278 eyes during 2011, 270 eyes during 2012, 396 eyes during 2013, 303 eyes during 2014 and 214 eyes during 2015. The results are very encouraging and even more than doctor’s expectations. In majority of cases were being possible to stop progression of the disease and escape the necessity of keratoplsaty.



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