Keratoconus: the best approach

Thanks to advances in diagnostics and therapy, keratoconus is today an increasingly treatable condition, with excellent results in terms of visual acuity preservation, provided that diagnosis is made as early as possible and the most effective treatment is adopted from the outset.

Keratoconus is a progressive corneal pathology, which can occur at different times in life, but usually makes its onset in the early 40s, with a slow, but often progressive and disabling, curving and thinning of the cornea.

It should be emphasised that keratoconus does not always have an evolutionary tendency, since, in a fairly significant number of cases, especially if the onset is late - after the age of 30 -, the deformation produced by an initial structural weakness of the cornea is generally not followed by further deterioration.

Keratoconus is characterised by abnormalities in the functioning of certain cells of the cornea, the keratocytes, which among other things have the purpose of making the corneal tissue compact and elastic, thanks to their ability to bind collagen fibres. When these cells become diseased, the bonds are reduced in number and, consequently, the strength of the cornea is reduced and the fibres, no longer held to each other, tend to slip, leading to the loss of solidity, strength, and shape of the cornea itself.

Causes and risk factors

The causes of keratoconus are not yet fully known, but the hereditary component is considered the most relevant, although we do not know the type of inheritance or which chromosomes are involved.

Other relevant causative factors are the prolonged or incorrect use of contact lenses and allergic conjunctivitis of particular intensity and duration.

Symptoms

The effects on vision manifest themselves initially with the sensation of blurred vision, especially in the evening and in activities such as driving a car or watching television.

As the corneal deformation progresses, there is a further progressive deterioration of visual quality. In the advanced stages, vision is poor in all light conditions and can often only be improved with rigid contact lenses.

A thorough ophthalmic examination, including specific examinations such as topography to analyse corneal curvatures and pachymetry to check corneal thicknesses, will allow the diagnosis to be made.

Treatment

Until a few decades ago, no action was possible to counteract keratoconus and the ophthalmologist's activities were limited to monitoring the worsening, prescribing glasses or contact lenses and finally, often, corneal transplant surgery.

The introduction of the cross-linking marked a turning point in the prognosis of the disease allowing, in almost all cases, the evolution of degeneration to be halted.

The cross-linking technique is performed after local anaesthesia (with anaesthetic eye drops) and consists of applying vitamin B2 eye drops to the cornea (riboflavin). This drug is left on the cornea for 10 minutes to allow it to penetrate into the deep layers: it is then instilled regularly for a further 30 minutes, during which time a source of ultraviolet light is used to activate riboflavin. The aim of the treatment is to eliminate diseased cells from the cornea, an action that results in the activation of stem cells capable of producing new healthy cells that will colonise the treated areas in order to stop corneal wear and tear. (see Collagen cross-linking using riboflavin and ultraviolet-a for corneal thinning disorders: an evidence-based analysis).

Not all patients can undergo the treatment, as insufficient corneal thickness, advanced age, the presence of lesions or scars, or the too advanced stage of evolution of keratoconus may constitute absolute contraindications to performing cross-linking safely.

Cross-linking is able to freeze the progression of the disease, but cannot restore the damage and deformations that keratoconus has already caused on the cornea. This is why early diagnosis is extremely important: in the onset stages, symptoms are virtually absent and the treatment is optimal.

To make this approach possible, every eye examination performed on patients between the ages of 10 and 40 should include specific examinations for keratoconus.

A significant advance was the so-called 'customised' cross-linking, which sets the treatment according to the specific characteristics of the diseased cornea to be treated.

Among the new proposals in cases of advanced keratoconus is the implantation of an intrastromal corneal lenticule that is able to stimulate the regeneration of the Fresh myopic intrastromal lenticular (FML) corneal stroma without the need for invasive penetrating keratoplasty. The study on the clinical application of this technique was presented by Dr Ceren Semiz from the Department of Ophthalmology at Eye Hospital Pristina, Kosovo at the ESCRS Winter Meeting 2024 in Frankfurt.

Good results also came from the two-step surgical approach, combining intracorneal rings with PRK (radial photokeratotomy) and corneal cross linking.

This protocol, presented by Dr. Olicier Prisant at EuCornea 2024 in Paris, has already been tested on a large cohort of patients with advanced keratoconus (946 eyes treated, including 686 with three-month follow-up data).

On the subject of keratoconus and crossi-linking see also:

• Keratoconus - Italian Ophthalmologist
• Clinical practice: application of corneal cross-linking in the treatment of infective keratitis - Oculista Italiano

• Avetisov SE, Averich VV, Pateyuk LS. Keratokonus: osnovnye napravleniya issledovanii [Keratoconus: main lines of research]. Vestn Oftalmol. 2023;139(3. Vyp. 2):11-20. Russian. doi: 10.17116/ophthalma202313903211. PMID: 37144364.
• Pron G, Ieraci L, Kaulback K; Medical Advisory Secretariat, Health Quality Ontario. Collagen cross-linking using riboflavin and ultraviolet-a for corneal thinning disorders: an evidence-based analysis. Ont Health Technol Assess Ser. 2011;11(5):1-89. Epub 2011 Nov 1. PMID: 23074417; PMCID: PMC3377552.