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Keratoconus: Further Reading - Appendix 1


Keratoconus is an asymmetric, bilateral, progressive corneal ectasia and thinning that is non-inflammatory in nature (but may be a sub-inflammatory disorder due to indirect collateral involvement). These corneal changes result's in irregular astigmatism, which reduces visual acuity and which becomes ever increasingly problematic to correct. The severity and course of the disorder can vary and is unpredictable.

The term Keratoconus is derived from two Greek words: "kerato", meaning cornea, and "konos", meaning cone. Keratoconus is a degenerative disorder of the eye in which structural changes within the cornea cause it to thin and change to a more conical shape than its normal gradual curve. Keratoconus can cause substantial distortion of vision, with multiple images, streaking and sensitivity to light all often reported by the patient. Keratoconus is the most common dystrophy of the cornea, it seems to occur in all ethnic groups worldwide, although for some ethnic groups the prevalence and severity of keratoconus is higher. It is typically diagnosed in the patient's when a loss of vision by the patient is reported.

Keratoconus is a little-understood disease with an uncertain cause, and its progression following diagnosis is unpredictable. If afflicting both eyes, the deterioration in vision can affect the patient's ability to drive a car or read normal print. It does not however lead to blindness, and in most cases, corrective lenses are effective enough to allow the patient to continue to drive legally and likewise function normally. Further progression of the disease may lead to a need for surgery. Despite its uncertainties, keratoconus can be successfully managed with a variety of clinical and surgical techniques, and often with little or no impairment to the patient's quality of life.



In a 1748 doctoral dissertation, the German oculist Burchard Mauchart provided an early description of a case of keratoconus, which he called staphyloma diaphanum. However, it was not until 1854 that British physician John Nottingham clearly described keratoconus and distinguished it from other ectasias of the cornea. Nottingham reported the cases of "conical cornea" that had come to his attention, and described several classic features of the disease, including polyopia, weakness of the cornea, and difficulty matching corrective lenses to the patient's vision. In 1859 British surgeon William Bowman used an ophthalmoscope (recently invented by German physician and physicist Hermann von Helmholtz) to diagnose keratoconus, and described how to angle the instrument's mirror so as to best see the conical shape of the cornea. Bowman also attempted to restore the vision by pulling on the iris with a fine hook inserted through the cornea and stretching the pupil into a vertical stenopeic slit like that of a cat. He reported that he had had a measure of success with the technique, restoring vision to an 18-year old woman who had previously been unable to count fingers at a distance of 8 inches (20 cm). By 1869, when the pioneering Swiss ophthalmologist Johann Horner wrote a thesis entitled On the treatment of keratoconus, the disorder had acquired its current name. The treatment at that time, endorsed by the leading German ophthalmologist Albrecht von Gräfe, was an attempt to physically reshape the cornea by chemical cauterization with a silver nitrate solution and application of a miosis-causing agent with a pressure dressing. In 1888 the treatment of keratoconus became one of the first practical applications of the then newly-invented contact lens, when the French physician Eugène Kalt manufactured a glass scleral shell which improved vision by compressing the cornea into a more regular shape. Since the start of the twentieth century, research on keratoconus has both improved understanding of the disease and greatly expanded the range of treatment options.







A simulation of the multiple images seen by a person with keratoconus.
"... a candle, when looked at, appears like a number of lights, confusedly running into one another" — Nottingham.

People with early keratoconus typically notice a minor blurring of their vision and come to their clinician seeking corrective lenses for reading or driving. At early stages, the symptoms of keratoconus may be no different from those of any other refractive defect of the eye. As the disease progresses, vision deteriorates, sometimes rapidly. Visual acuity becomes impaired at all distances, and night vision is often quite poor. Some individuals have vision in one eye that is markedly worse than that in the other eye. Some develop photophobia (sensitivity to bright light), eye strain from squinting in order to read, or itching in the eye. There is usually little or no sensation of pain.

The classic symptom of keratoconus is the perception of multiple 'ghost' images, known as monocular polyopia. This effect is most clearly seen with a high contrast field, such as a point of light on a dark background. Instead of seeing just one point, a person with keratoconus sees many images of the point, spread out in a chaotic pattern. This pattern does not typically change from day to day, but over time it often takes on new forms. Patients also commonly notice streaking and flaring distortion around light sources. Some even notice the images moving relative to one another in time with their heart beat.


Signs and Diagnosis

Prior to any physical examination, the diagnosis of keratoconus frequently begins with an ophthalmologist's or optometrist's assessment of the patient's medical history, particularly the chief complaint and other visual symptoms, the presence of any history of ocular disease or injury which might affect vision, and the presence of any family history of ocular disease. An eye chart, such as a standard Snellen chart of progressively smaller letters, is then used to determine the patient's visual acuity. The eye examination may proceed to measurement of the localised curvature of the cornea with a manual keratometer, with detection of irregular astigmatism suggesting a possibility of keratoconus. Severe cases can exceed the instrument's measuring ability. A further indication can be provided by retinoscopy, in which a light beam is focused on the patient's retina and the reflection, or reflex, observed as the examiner tilts the light source back and forth. Keratoconus is amongst the ophthalmic conditions that exhibit a scissor reflex action of two bands moving toward and away from each other like the blades of a pair of scissors.

If keratoconus is suspected, the ophthalmologist or optometrist will search for other characteristic findings of the disease by means of slit lamp examination of the cornea. An advanced case is usually readily apparent to the examiner, and can provide for an unambiguous diagnosis prior to more specialised testing. Under close examination, a ring of yellow-brown to olive-green pigmentation known as a Fleischer ring can be observed in around half of keratoconic eyes.The Fleischer ring, caused by deposition of the iron oxide hemosiderin within the corneal epithelium, is subtle and may not be readily detectable in all cases, but becomes more evident when viewed under a cobalt blue filter. Similarly, around 50% of subjects exhibit Vogt's striae, fine stress lines within the cornea caused by stretching and thinning. The striae temporarily disappear while slight pressure is applied to the eyeball. A highly pronounced cone can create a V-shaped indentation in the lower eyelid when the patient's gaze is directed downwards, known as Munson's sign. Other clinical signs of keratoconus will normally have presented themselves long before Munson's sign becomes apparent, and so this finding, though a classic sign of the disease, tends not to be of primary diagnostic importance.

Corneal topogram of a keratoconus cornea

Corneal topography of a keratoconic eye

A handheld keratoscope, sometimes known as Placido's disk, can provide a simple non-invasive visualization of the surface of the cornea by projecting a series of concentric rings of light onto the cornea. A more definitive diagnosis can be obtained using corneal topography, in which an automated instrument projects the illuminated pattern onto the cornea and determines its topology from analysis of the digital image. The topographical map indicates any distortions or scarring in the cornea, with keratoconus revealed by a characteristic steepening of curvature which is usually below the centreline of the eye. The technique can record a snapshot of the degree and extent of the deformation as a benchmark for assessing its rate of progression. It is of particular value in detecting the disorder in its early stages when other signs have not yet presented.

Once keratoconus has been diagnosed, its degree may be classified by several metrics:
  • The steepness of greatest curvature from mild (< 45 D), advanced (up to 52 D) or severe (> 52 D); 
  • The morphology of the cone: nipple (small: 5 mm and near-central), oval (larger, below-center and often sagging), or globus (more than 75% of cornea affected); 
  • The corneal thickness from mild (> 506 μm) to advanced (< 446 μm).

Increasing use of corneal topography has led to a decline in use of these terms.



The National Eye Institute reports that keratoconus is the most common corneal dystrophy in the United States, affecting approximately 1 in 2,000 Americans, but some reports place the figure as high as 1 in 500*. The inconsistency may be due to variations in diagnostic criteria*, with some cases of severe astigmatism interpreted as those of keratoconus, and vice versa*. A long-term study found a mean incidence rate of 2.0 new cases per 100,000 population per year*. It is likely if modern electronic diagnostic equipment such as Corneal Topography was used in a study such as this one, more cases of Keratoconus would be picked up much more earlier. A Corneal Topography machine was a non-existent/scarce resource during 1935 through to 1982 when this study was done and therefore not possibly included right through this study period.


* Weissman BA, Yeung KK. Keratoconus. eMedicine: Keratoconus. Accessed 12 Feb 2006

* Epstein A (2000). Keratoconus and related disorders (PDF). North Shore Contact Lens. Retrieved on 2007-09-08

* Krachmer JH, Feder RS, Belin MW. Keratoconus and related noninflammatory corneal thinning disorders. Surv Ophthalmol. 1984 Jan-Feb;28(4):293–322. PMID 6230745

* Kennedy RH, Bourne WM, Dyer JA. A 48-year clinical and epidemiologic study of keratoconus. Am J Ophthalmol. 1986 Mar 15;101(3):267-73. PMID 3513592

It is suggested that males and females, and all ethnicities appear equally susceptible, though some recent studies have cast doubt upon this*, suggesting a slightly higher experience of Keratoconus amongst females. The literature however varying with regards to this and it may even be due to symptoms being reported more readily by females than males. Also, a study carried out in the UK* suggests that people of an Asian heritage are 4.4 times as likely to suffer from keratoconus than Caucasians, and are also likely to present with the condition earlier.


* Fink BA, Wagner H, Steger-May K, Rosenstiel C, Roediger T, McMahon TT, Gordon MO, Zadnik K. Differences in keratoconus as a function of gender. Am J Ophthalmol. 2005 Sep;140(3):459-68. PMID 16083843

* Pearson AR, Soneji B, Sarvananthan N, Sandford-Smith JH. Does ethnic origin influence the incidence or severity of keratoconus? | Eye. 2000 Aug;14 ( Pt 4):625–8

Keratoconus is normally bilateral (affecting both eyes) although the distortion is usually asymmetric and is rarely completely identical in both corneas. Unilateral cases tend to be uncommon, and may in fact be very rare if a very mild condition in the better eye is simply below the limit of clinical detection. It is common for keratoconus to be diagnosed first in one eye and not until later in the other. As the condition then progresses in both eyes, the vision in the earlier-diagnosed eye will often persist to be poorer than that in its fellow.



Patients with keratoconus typically present initially with mild astigmatism, commonly at the onset of puberty, and are diagnosed as having the disease by the late teenage years or early 20s. In rare cases keratoconus can occur in children or not present until later adulthood. A diagnosis of the disease at an early age may indicate a greater risk of severity in later life. Patients' vision will seem to fluctuate over a period of months, driving them to change lens prescriptions frequently but as the condition worsens, contact lenses become required in the majority of cases. The course of the disorder can be quite variable, with some patients remaining stable for years or indefinitely, while others progress rapidly or experience occasional exacerbations over a long and otherwise steady course. Most commonly, keratoconus progresses for a period of ten to twenty years before the course of the disease generally ceases. With the advent of the crosslinking treatment the worry about the progression of keratoconus can be stopped, with the early use of this treatment. Crosslinking is the first ever true treatment for Keratoconus, as it treats to strengthen the weakened Keratoconus cornea.



Picture of Corneal Hydrops

In advanced cases, bulging of the cornea can result in a localized rupture of Descemet's membrane, an inner layer of the cornea. Aqueous humor from the eye's anterior chamber seeps into the cornea before Descemet's membrane reseals. The patient experiences pain and a sudden severe clouding of vision, with the cornea taking on a translucent milky-white appearance known as a corneal hydrops. Although disconcerting to the patient, the effect is normally temporary and after a period of six to eight weeks the cornea usually returns to its former transparency. The recovery can be aided non-surgically by bandaging with an osmotic saline solution. Although a hydrops usually causes increased scarring of the cornea, occasionally it will benefit a patient by creating a flatter cone, aiding the fitting of contact lenses. Very occasionally, in extreme cases, the cornea thins to the point that a partial rupture occurs, resulting in a small, bead-like swelling on the cornea that has been filled with fluid. When this occurs, a corneal transplant can become urgently necessary to avoid complete rupture and resulting loss of the eye.


Pathophysiology and cause

Despite considerable research, the etiology of keratoconus remains somewhat of a mystery. According to research, it is suggested that keratoconus can arise from a number of different factors: genetic, stress/trauma  to the cornea, environmental or cellular, any of which may form the trigger for the onset of the Keratoconus. Once initiated, Keratoconus normally develops by progressive dissolution of Bowman's layer, the membrane lying between the corneal epithelium and stroma. As the two come into contact, cellular and structural changes in the cornea adversely affect its integrity and lead to the bulging and scarring that are characteristic of the disorder. Within any individual keratoconic cornea, there may be found regions of degenerative thinning coexisting with regions undergoing wound healing.

The visual distortion experienced by the patient comes from two sources, one being the irregular deformation of the surface of the cornea; the other being scarring that occurs on its exposed highpoints. These factors act to form regions on the cornea that map an image to different locations on the retina and give rise to the symptom of monocular polyopia. The effect can worsen in low light conditions as the dark-adapted pupil dilates to expose more of the irregular surface of the cornea. Scarring appears to be an aspect of the corneal degradation; however, a recent, large, multi-center study suggests that abrasion by contact lenses may increase the likelihood of this finding by a factor of over two.*


* Barr JT, Wilson BS, Gordon MO, Rah MJ, Riley C, Kollbaum PS, Zadnik K; CLEK Study Group. Estimation of the incidence and factors predictive of corneal scarring in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study. Cornea. 2006 Jan;25(1):16–25. PMID 16331035

A number of studies have indicated that keratoconic corneas show signs of increased activity by proteases, a class of enzymes that break some of the collagen cross-linkages in the corneal stroma, with a simultaneous reduced expression of protease inhibitors. Other studies have suggested that reduced activity by the enzyme aldehyde dehydrogenase may be responsible for a build-up of free radicals and oxidising species in the cornea. It seems likely that, whatever the pathogenetical process, the damage caused by activity within the cornea results in a reduction in its thickness and biomechanical strength.

A genetic predisposition to keratoconus has been observed, with the disease running in certain families, and incidences reported of concordance in identical twins. The frequency of occurrence in close family members is not clearly defined, though it is known to be considerably higher than that in the general population, and studies have obtained estimates ranging between 6% and 19%. A responsible gene has not been identified: two studies involving isolated, largely homogenetic communities have contrarily mapped putative gene locations to chromosomes 16q and 20q. However, most genetic studies agree on an autosomal dominant model of inheritance. Keratoconus is also diagnosed more often in people with Down syndrome, though the reasons for this link have not yet been determined.Keratoconus has been associated with atopic diseases, which include asthma, allergies, and eczema, and it is not uncommon for several or all of these diseases to affect one person. A number of studies suggest that vigorous eye rubbing may contribute to the progression of keratoconus, and that patients should be discouraged from the practice.


Contact Lens

In early stages of keratoconus, spectacles can suffice to correct for the mild astigmatism. As the condition progresses, spectacles may no longer provide the patient with a satisfactory degree of visual acuity, and most clinical practitioners will move to managing the condition with contact lenses.

Rigid gas permeable lens for keratoconus

A close-up picture of a Contact Lens


In keratoconic patients, contact lenses improve vision by means of tear fluid filling the gap between the irregular corneal surface and the smooth regular inner surface of the lens, thereby creating the effect of a smoother cornea. Many specialized types of contact lenses have been developed for keratoconus, and affected people may seek out both doctors specialized in conditions of the cornea, and contact-lens fitters who have experience managing patients with keratoconus. The irregular cone presents a challenge and the fitter will endeavour to produce a lens with the optimal contact, stability and steepness. Some trial-and-error fitting may prove necessary.

Traditionally, contact lenses for keratoconus have been the 'hard' or rigid gas-permeable variety, although manufacturers have also produced specialized 'soft' or hydrophilic lenses. A soft lens has a tendency to conform to the conical shape of the cornea, thus diminishing its effect. To counter this, hybrid lenses have been developed which are hard in the centre and encompassed by a soft skirt. Soft or hybrid lenses do not however prove effective for every patient. Recently, newer soft lenses developed for Keratoconus have had successes to a good extent. 

Some patients also find good vision correction and comfort with a "piggyback" lens combination, in which gas permeable rigid lenses are worn over soft lenses, both providing a degree of vision correction. One form of piggyback lens makes use of a soft lens with a countersunk central area to accept the rigid lens. Fitting a piggyback lens combination requires experience on the part of the lens fitter, and tolerance on the part of the keratoconic patient.

Scleral lenses are sometimes prescribed for cases of advanced or very irregular keratoconus; these lenses cover a greater proportion of the surface of the eye and hence can offer improved stability and comfort. They also vault over the cornea and so minimizes any trauma being placed on it.   


Scleral lens for Keratoconus

A Scleral Contact Lens


The larger size of the lenses may make them unappealing or awkward to use for some people at first, however their easier handling can find favour with patients after they have had some practice with using them.

Traditionally, Scleral Lenses have been offered in Keratoconus cases so advanced that a transplant is the only option, but increasingly they are being successfully used for lower grades of keratoconus where there are problems with corneal contact lens intolerance.


Surgical Options


Corneal Transplant


Penetrating Keratoplasty



A Grafted Cornea


Between 10% and 25% of cases of keratoconus will progress to a point where vision correction is no longer possible, thinning of the cornea becomes excessive, or scarring as a result of contact lens wear causes problems of its own, and a corneal transplantation in the form of a penetrating keratoplasty becomes required. Sometimes a penetrating keratoplasty is called a  perforating keratoplasty also. Keratoconus is the most common grounds for conducting a penetrating keratoplasty, generally accounting for around a quarter of such procedures. The corneal transplant surgeon trephines a lenticule of corneal tissue and then grafts the donor cornea to the existing eye tissue, usually using a combination of running and individual sutures. The cornea does not have a direct blood supply, and so donor tissue is not required to be blood type matched. Eye banks check the donor corneas for any disease or cellular irregularities.

The acute recovery period can take four to six weeks and full post-operative vision stabilization often takes a year or more but most transplants are very stable in the long term. There are reports that penetrating keratoplasty has the most successful outcome of all transplant procedures, and when performed for keratoconus in an otherwise healthy eye, its success rate can be 95% or greater. The sutures used usually dissolve over a period of three to five years but individual sutures can be removed during the healing process if they are causing irritation to the patient.

In the USA, corneal transplants (also known as corneal grafts) for keratoconus are usually performed under sedation as outpatient surgery. In other countries, such as Australia and the UK, the operation is commonly performed with the patient undergoing a general anaesthetic. All cases a require careful follow-up with an eye surgeon (ophthalmologist) for a number of years. Frequently, vision is greatly improved after the surgery, but even if the actual visual acuity does not improve, because the cornea is a more normal shape after the healing is completed, patients can more easily be fitted with corrective lenses. Complications of corneal transplants are mostly related to vascularization of the corneal tissue and rejection of the donor cornea. Vision loss is very rare, though difficult-to-correct vision is possible. When rejection is severe, repeat transplants are often attempted, and are frequently successful. Keratoconus will not normally reoccur in the transplanted cornea; incidences of this have been observed, but are usually attributed to incomplete excision of the original cornea or inadequate screening of the donor tissue. The long-term outlook for corneal transplants performed for keratoconus is usually favorable once the initial healing period is completed and a few years have elapsed without problems.

DALK Transplants

One way of reducing the risk of rejection is to use a newer technique called a Deep Anterior Lamellar Keratoplasty, referred to as DALK. In a DALK graft, only the outermost epithelium and the main bulk of the cornea, the stroma, are replaced; the patient's rearmost endothelium layer is retained, giving some additional structural integrity to the post-graft cornea. Because a graft rejection usually begins in the endothelium, the chance of a rejection episode is greatly reduced.

Furthermore, it is possible to transplant tissue from a donor which has been freeze-dried. The freeze-drying process ensures that this tissue is dead, so there is no chance at all of a rejection.

Some surgeons prefer to remove the donor epithelium, others leave the donor's cells in place. Removing it can cause a slight improvement in overall vision, but a corresponding increase in visual recovery time.



Rarely, a non-penetrating keratoplasty known as an epikeratophakia (or epikeratoplasty) may be performed in cases of keratoconus. The corneal epithelium is removed and a lenticule of donor cornea grafted on top of it. The procedure requires a greater level of skill on the part of the surgeon, and is less frequently performed than a penetrating keratoplasty as the outcome is generally less favorable. It may however be seen as an option in a number of cases, particularly for young patients.


Corneal Ring Segment Inserts


Corneal ring segment inserts for Keratoconus

A close-up picture of Intacs placed in the Cornea


Intacs inserts

A recent surgical alternative to corneal transplant is the insertion of intrastromal corneal ring segments. A small incision is made in the periphery of the cornea and two thin arcs of polymethyl methacrylate are slid between the layers of the corneal stroma on either side of the pupil, the incision then being closed. The segments push out against the curvature of the cornea, flattening the peak of the cone and returning it to a more natural shape. The procedure, carried out on an outpatient basis under local anaesthesia, offers the benefit of being reversible/removable and even potentially exchangeable with differant thickness rings to gain more correction if its needed.A development on the concept involves the injection of a transparent synthetic gel into a channel bored through the stroma. As the gel polymerises, it stiffens and takes on similar properties to the pre-formed rings.*


* Simon G, Parel JM, Lee W, Kervick GN. Gel injection adjustable keratoplasty. Graefes Arch Clin Exp Ophthalmol. 1991;229(5):418-24. PMID 1718824

The two principal types of intrastromal rings available are known by the trade names of Intacs and Ferrara rings. Intacs are flatter and less centrally placed than the prismatic Ferrara rings. Intacs were first approved by the Food and Drug Administration (FDA) in the United States in 1999 for myopia; this was extended to the treatment of keratoconus in July 2004. Ferrara rings await US FDA approval for keratoconus, it was given CE approved in Europe in August 2003.

The way Ferrara Rings differs from Intacs is that Ferrara Rings are smaller than Intacs and although small they are less likely to produce glare as they are shaped like a prism. Any light entering the ring is reflected back out again away from the visual pathway. Because these rings are smaller and positioned closer to the centre of the cornea, they are more powerful and can reduce myopia up to -12.00 D, which is more than what Intacs can correct. Glare has been reported in some individuals with large pupils. Intacs are thus preferred to be used for those with large pupils.

Clinical studies on the effectiveness of intrastromal rings on keratoconus are in their early stages, and results have so far been generally encouraging, though they have yet to enter into wide acceptance with all refractive surgeons. In common with a penetrating keratoplasty, the requirement for some vision correction in the form of corrective lenses may remain subsequent to the operation but its hoped to be more of the soft contact lens or glasses type. This depends on the level of the patients Keratoconus before the operation and the aim of Intacs is to make the cornea more of a regular shape so that to make correction with simpler corrective lenses easier. Potential complications of intrastromal rings include accidental penetration through to the anterior chamber when forming the channel, post-operative infection of the cornea, and migration or extrusion of the segments. The rings offer a good chance of vision improvement even in otherwise hard to manage eyes, but it is not guaranteed and in a few cases may worsen. 


Asymmetric Radial Keratotomy

Radial keratotomy is a refractive surgery procedure where the surgeon makes a spoke-like pattern of incisions into the cornea to modify its shape. This early surgical option for myopia has been largely superseded by LASIK and other similar procedures. LASIK itself is absolutely contraindicated in keratoconus and other corneal thinning conditions – it cannot be used for people with keratoconus because removal of corneal stromal tissue will further damage their already thin and weak corneas.

For similar reasons, radial keratotomy has also generally not been used for keratoconic patients. However, an Italian clinic has reported some success with a modified Asymmetric Radial Keratotomy (generally abbreviated to ARK, with a "miniature" version called mini-ARK. Both are used depending on the gravity of the case and now by the newer Mini-ASRK procedure. In these  asymmetric type of operations the placed incisions are confined only to one sector of the eye. It is used in treating mild to moderate and selected other cases of Keratoconus.

The experience of the surgeon plays a very important role in this surgery because the treatment plan (the monogram) needed to undertake this surgery takes many years to learn for the use in Keratoconus, therefore it is not a common place procedure. Every surgery conducted is individually tailored uniquely, so every surgery will be different to the previous one conducted. This is because the treatment is customized to the patients particular individual Keratoconus corneal profile, and by doing it this way the best optimal results with this surgery can be obtained for the right candidate. After field of view tests are taken of the patients vision and including with other tests, it is then calculated: where, how many, how deep, how long, at which angle etc, each microscopic incision should consist of when placed.

The corneal thickness is first measured using a pachymeter belore the procedure, then the surgeon makes cuts to a depth of 70-80% of the measured thickness. The patient may initially experience photophobia and fluctuation of vision after-wards, just as with other forms of refractive surgery during the recovery phase. 

Close up pictures of mini ARK

"The definition of the new mini ASRK (Asymmetric Selective Radial Keratotomy) and SACL (Selective Asymmetric Cross Linking) combined together as a treatment, is convergent in the finality to preserve and reinforce the weaken collagen fibers in the keratoconus cornea and to normalize the profile of the cornea when done early enough in the disease process.
The biomechanical implosion created by the mini incisions are reinforced by the deep fotopolimerization created by Selective Asymmetric Cross Linking that will produce a total thickness Cross Linking of the cornea and not only for 240 micron, adding an extra strength to the corneal structure combining the new links in the collagen fibers with the stimulation of the mini incisions to produce new regenerative cells to repair the incision itself. So that a new stronger corneal collagen net is the result of the two combined techniques, doubling and often tripling the refractive result of using the classic protocols alone.

We should think from now on only to create “implosive” surgical effects (where it is inwards in it's reinforcement with it's flattening and strengthening to bring the cornea back to the correct profile) because we are talking of an “explosive” pathology (where it is outwards in it's direction with it's weakening and disfigurement). Then we have to think to the asymmetric characteristic of the pathology, so that the best answer is an asymmetrical surgical and medical treatment combined together as we perform at our Rome Vision Clinic.
 All my best
Prof. Massimo Lombardi"

Corneal Collagen Crosslinking with Riboflavin

This is a treatment which has shown success at halting the progression of Keratoconus and is CE approved in Europe. Corneal Collagen Crosslinking with Riboflavin is sometimes referred to as CXL or X-linking.

CXL Treatment
Keratoconus being treated

A one-time application of riboflavin eye drops is inpregananted in to the cornea for 30 minutes. The riboflavin (B2), when activated by approximately 30 minutes illumination with UV-A light, creates collagen cross-linking to take place within the stroma and so recovers considerably the cornea's mechanical strength and making it more regular. Crosslinking was developed at the University Eye Center of Europe, Carl Gustav Carus in Dresden, Germany. The Crosslinking treatment has been shown to reduce and arrest the progression of keratoconus, and also in roughly every other patient case even reversing it to a degree, particularly when applied in combination with intracorneal ring segments. Corrective lenses may still be required after the treatment (if the treatment is done late, and in advanced cases where correction was needed to begin with) but it is hoped that it could limit further deterioration in the patient's vision and reduce the case for keratoplasty.



Other corneal thinning disorders closely related to Keratoconus

Several other non-inflammatory eye disorders also are in the same family of Primary Corneal Ectasias (which included Keratoconus), which are less common than keratoconus, also cause thinning of the cornea:

Pellucid marginal degeneration (PMD) is often considered another version of KC, in which corneal thinning occurs about a millimeter above the inferior limbus, resulting in advanced against-the-rule corneal astigmatism that may be observed by keratometry or videokeratography.

Terrien marginal corneal degeneration
is a mildly inflammatory disease, usually of the superior limbus, which also can induce irregular against-the-rule astigmatism and corneal thinning (often with vascularization and lipid deposits).

Keratoglobus (KG) is an extremely rare corneal disease in which the entire cornea, from limbus to limbus, thins, sometimes to the point where spontaneous perforation becomes possible.

Posterior Ectasia
is another extremely rare disease in which the posterior corneal surface suffers a loss of substance.


All content is intended as an informational series and should not be used as a substitute for medical advice. Up-dated info-sys 2 060606 (Wiki) GNU FDL KC data. This is the GNU Free Documentation License reference article from Wikipedia. All text is Licensed.



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