This article is more than 5 years old. Information may no longer be current.
Keratoconus can be treated based on the stage of the condition
Surgeons discuss various treatment options involving intrastromal ring segments and implantable contact lenses.
Click Here to Manage Email Alerts
Most ophthalmologists would probably agree that the treatment of keratoconus has come a long way in recent years.
Traditionally, keratoconus was managed with spectacles, contact lenses and penetrating keratoplasty. While these so-called “old players” are still routinely used and continue to play an important role in keratoconus management, we now have access to additional treatment options such as corneal collagen cross-linking using riboflavin and ultraviolet light, femtosecond laser surgery, intrastromal corneal ring segments (ICRS) and implantable contact lenses, all of which have helped to improve patient outcomes.
Juan Grandin
Such additions to the keratoconus treatment armamentarium have been particularly helpful for patients who find it difficult to tolerate contact lenses; however, they also allow ophthalmologists to provide a comprehensive treatment plan for all keratoconic patients at all stages of the condition, in order to ensure the best visual outcomes possible.
Stage of the condition
At our center, the Zaldivar Institute in Mendoza, Argentina, we tailor keratoconus treatment according to the stage of the condition.
Forme fruste. A patient presenting with suspected keratoconus typically has an abnormal corneal topography but does not have any other clinical signs or symptoms. In these patients, we do a frequent topography control, usually every 6 months. We believe this is important, particularly in young patients, ie, up to 40 years of age. At this stage, we are also careful to treat conditions that affect the corneal surface, such as dry eye, meibomian gland dysfunction, and allergic conditions such as atopic keratoconjunctivitis, because they can also affect the progression of keratoconus.
Initial keratoconus. In patients with initial keratoconus, there is no loss of corrected distance visual acuity (CDVA) and no evidence of surface irregularity. However, there is usually some evidence of topographic progression. In these patients, we carry out collagen cross-linking.
Keratoconus stage 1, 2 or 3. When a patient has keratoconus stage 1, 2 or 3 (according to the Amsler-Krumeich classification) without evidence of progression but with loss of CDVA and evidence of surface irregularity, we undertake frequent topography control and implant an ICRS with a femtosecond laser in order to reduce corneal steepening and refractive errors and to improve surface regularity. Implanting an ICRS may also delay or even eliminate the need for keratoplasty.
At our center, we use the Keraring ICRS (Mediphacos), which was specifically designed to treat corneal ectasia, providing corneal surface regularization and refractive correction. Made of PMMA, the Keraring is characterized by a unique prismatic design that induces a flattening effect on the cornea and reduces the incidence of glare and halos. The Keraring is not available in the United States as a U.S. Food and Drug Administration-approved device.
Figure 1. Topography result of a Keraring implant.
Images: Grandin J, Lofti A
Figure 2. Keraring implants combined with other techniques such as corneal collagen cross-linking, PRK and phakic IOL implantation.
We also use the Keraring ICRS if a patient has keratoconus stage 1, 2 or 3 with evidence of progression, loss of CDVA and evidence of surface irregularity. However, in these cases, we also perform collagen cross-linking. ICRS and collagen cross-linking are not competing technologies. Rather, they are complementary techniques that provide synergistic results: the ICRS regularizing the surface of the cornea and collagen cross-linking improving the biomechanical properties of the cornea.
Advanced keratoconus. Finally, in the patient with stage 4 keratoconus without hydrops, we typically perform an IntraLase (Abbott Medical Optics) deep anterior lamellar keratoplasty. Preserving the endothelium has advantages in terms of visual recovery, offering resistance in case of eventual trauma, and graft survival; it also reduces the risk of graft rejection. However, if the patient has hydrops, we convert to a penetrating keratoplasty with IntraLase.
Adding an implantable contact lens
Because implantable contact lenses are posterior phakic implants and, therefore, do not physically affect the cornea, they represent a safe and effective method of correcting high refractive errors in patients with keratoconus. However, in our experience, there are several key points to keep in mind when considering implantable contact lens use in a keratoconic patient.
First, it is important to stabilize the corneal surface. If a keratoconus patient does not have a regular corneal surface, the refraction will undoubtedly continue to change after implantable contact lens implantation, ultimately resulting in poor visual acuity. Second, the surgeon must ensure that refraction is stable before proceeding with implantable contact lens implantation; ideally, uncorrected distance visual acuity (UDVA) should be 20/40 or better. Finally, it is necessary to stop progression of the condition with collagen cross-linking before implantable contact lens implantation. However, we have realized that the cornea continues to change immediately after collagen cross-linking. Consequently, after inserting the Keraring and performing collagen cross-linking, we usually allow 12 months for the cornea to stabilize before implanting the implantable contact lenses.
At our center, we regularly perform ICRS implantation and corneal collagen cross-linking followed by implantable contact lens or toric implantable contact lens implantation. To date, outcomes have been very promising. For example, a 25-year-old patient with stage 3 keratoconus who had a preoperative UDVA of counting fingers and a CDVA of 20/100 received an ICRS and collagen cross-linking. One year later, the patient’s CDVA had improved to 20/40. At this point, we implanted a toric implantable contact lens. Six months after implantable contact lens implantation, the patient had UDVA of 20/30 and CDVA of 20/25. There were no complications.
Tips and considerations
We noted that it is essential to perform frequent topography control in patients with suspicions of keratoconus and those with stage 1, 2 or 3 without evidence of progression. It is also worth reiterating that ICRS do not halt keratoconus progression per se. Rather, they remodel the cornea shape, thus helping to reduce the speed of keratoconus progression. To illustrate the importance of both these points, one of our patients was diagnosed with keratoconus in March 2005, received ICRS implantation in December 2005, experienced an improvement in his condition within 6 months and decided to not return to the clinic. Unfortunately, when he finally presented 4 years later, he had developed advanced-stage keratoconus, which may have been prevented had he fully recognized the importance of regular follow-ups with topographic measurements.
Additionally, although ICRS implantation combined with collagen cross-linking is an excellent treatment option for keratoconic patients, we believe that in patients with high refractive errors, ICRS and corneal collagen cross-linking followed by implantable contact lens or toric implantable contact lens implantation should be the gold standard treatment. Notably, we have found that, compared with other ICRS, the Keraring SI-6 has a wider base, which provides 25% greater implant volume and compensates for reduction of effect in the larger optical zone. However, regardless of which ICRS is used, our key tip for a successful surgery is to ensure precise alignment between the ICRS and the implantable contact lens. One important tip to decide whether an SI-5 or SI-6 ICRS should be implanted in the mesopic pupillary diameter. If it is greater than 4 mm, we prefer the SI-6, which allows implantation in optical zones of 5.5 mm and 6 mm. Another point to consider is whether patients will be a candidate for a phakic or pseudophakic IOL after the Keraring implantation. If they are, we always implant the SI-6 ICRS. This is to avoid possible SI-5-induced halos. The SI-5 model allows implantation in an optical zone of 5 mm.