Corneal cone – qualification for surgery
Corneal cone is a progressive eye disease that leads to thinning and distortion of the cornea, with subsequent deterioration of vision – myopia and astigmatism and often hypersensitivity to light. Excessive habitual eyelid rubbing causes damage to corneal collagen.
To be sure if you have corneal cone you need to perform corneal topography. Corneal topography is a non-invasive and painless examination. Depending on the diagnosed changes, measures are taken to:
- Stopping the progression – and in some cases reversing – of lesions.
- The aim is for the patient to achieve the greatest possible visual acuity. If the corneal relief is small, soft contact lenses are used, when the relief is large hard lenses come into play.
A treatment that helps prevent the need for a corneal transplant is Cross-Linking (CLX) , also known as cross-linking, cross-collagenization of the cornea. The treatment stiffens the cornea and increases its mechanical resistance, which is done by increasing the number of bonds between the collagen fibers that build it.
It occurs under the influence of UVA irradiation of the cornea. In order to increase the sensitivity of the superficial layers of the cornea to UVA radiation, it is soaked in a special photosensitizing substance, riboflavin (vitamin B2).
The procedure can be performed using two methods: Epi-Off and Epi-On. The effect of both methods is comparable.
Indications for Cross-Linking treatment
Among the indications for the Csoss-Link procedure are progressive corneal cone, corneal ectasia (corneal dilatation diseases) and recurrent corneal cone after corneal transplantation. The procedure is also used to treat transparent marginal corneal degeneration(keratotorus: Pellucid Marginal Degeneration PMD).
Qualification for the procedure includes:
- patient interview
- computerized eye examination (autorefractometry)
- Keratometry (measurement of the curvature of the cornea).
- pachymetry (measurement of corneal thickness).
- corneal topography
Preoperative studies include:
- patient interview
- computerized eye examination (autorefractometry)
- Keratometry (measurement of the curvature of the cornea).
- tonometry (measurement of intraocular pressure)
- optometric examination:
- Visual acuity without correction (vis sc),
- eye dominance,
- subjective refraction,
- In case of astigmatism – Determining the power and axis of the cylinder
- Corrected visual acuity (vis cc),
- Checking the parameters of binocular vision (fusion, stereopsis, presence of foria/tropia),
- In the case of presbyopia, the determination of addition (nearsightedness allowance) and simulation of monovision (monovision tolerance test).
- pachymetry (measurement of corneal thickness).
- corneal topography
- dynamic pupilography
- BUT – tear film interruption test (tear film quality).
- Eye biometry (measurement of eyeball length), anterior chamber depth (Anterion)
- Cycloplegia (paralysis of accommodation and pupil dilation)
- autorefraction
- anterior and posterior biomicroscopy of the eye
- tomography (OCT – optical coherence tomography of the eye)
- fundus photography (fundus camera image)
Examination of the anterior segment of the eye is performed at SwissLaser through the platform ANTERION® . The device combines corneal topography and tomography, measurement of the anterior segment of the eye, measurement of axial length, and IOL ( Intraocular lens power calculation) calculation to facilitate the routine surgical procedure. Visual confirmation of all measurements with high-resolution swept source OCT images ensures diagnostic confidence. One of the ANTERIONA® modules (the Barret module) includes calculation formulas for calculating toric lenses.
OCT examination of the posterior segment of the eye and cornea is performed at SwissLaser with the Retina Scan Duo ™. It’s a high-resolution OCT and funduscamera (imaging the fundus of the eye through the pupil) in one.
Contraindications to performing Cross-Linking treatment
Among the contraindications to the procedure are:
- cornea too thin – in order to perform crosslinking the cornea should be at least 400 µm thick (if corneal thickness is below the minimum value, endothelial damage cannot be excluded; corrected vision in glasses or contact lenses should not be less than 0.3)
- corneal healing disorders
- inflammations of the cornea
