January 2019

CORNEA

Presentation spotlight
Intracorneal ring segments and ectasia


by Stefanie Petrou Binder, MD, EyeWorld Contributing Writer

According to [Dr. Seitz’s] study outcomes, eyes with post-LASIK keratectasia benefited from Intacs implantation, improving corrected and uncorrected visual acuity.

Intacs SK for treatment of keratoconus, pellucid marginal degeneration, and iatrogenic keratectasia after LASIK

Intacs are placed in a midperipheral stromal tunnel created with the femtosecond laser in 80% depth, as
measured with the anterior segment OCT in the 6–7 mm zone
Source: Berthold Seitz, MD

ICRS improve visual acuity in higher grade ectasia patients and help to stabilize the cornea

Intracorneal ring segments (ICRS) are emerging as a practicable treatment option in eyes with corneal ectatic disease. ICRS implantation is minimally invasive and complication free in the hands of an experienced surgeon. They can be explanted (reversible) and can be combined with or followed by corneal stabilizing procedures, such as crosslinking (CXL). Approaches to the treatment of ectasia are stage related and include contact lenses, ICRS, CXL, deep anterior lamellar keratoplasty (DALK), and penetrating keratoplasty (PKP).
Corneal ectatic disorders are a group of presumably non-inflammatory, progressive eye conditions characterized by bilateral, often asymmetric corneal thinning. They are associated with a reduction in the mechanical strength of the cornea, a progressive decrease in visual acuity, and the development of both irregular astigmatism and corneal opacification. Ectatic disorders are either primary, as seen in keratoconus and pellucid marginal degeneration, or iatrogenic, as noted in post-LASIK corneal ectasia.

Intacs for ectatic disease

Berthold Seitz, MD, Saarland University Medical Center, Department of Ophthalmology, Homburg, Germany, shared his experience using ICRS in patients with keratectasia in a presentation he gave at the 2018 World Ophthalmology Congress. According to Dr. Seitz, ICRS were effective in stopping the progression associated with keratectasia and improved visual acuity.1
His study included 84 eyes of 69 patients who received ICRS from August 2011 to September 2015, of which 74 eyes were implanted with Intacs SK (Addition Technology, Lombard, Illinois) and 10 eyes with the Keraring S16 (Mediphacos, Belo Horizonte, Brazil). The Intacs group was comprised of patients diagnosed with keratoconus who had contact lens intolerance (n=65 eyes), PMD (n=2 eyes), and post-LASIK keratectasia (n=6 eyes) with clear, unscarred central corneas, and one case involving a Ferrara Ring (AJL Ophthalmic, Araba, Spain) explantation. The Keraring group was made up of 10 keratoconus eyes.
The same surgeon conducted all of the surgeries and the tunnel was created using a femtosecond laser that allowed ICRS implantation in the 6–7 mm optic zone. The ring segments were implanted deep in the corneal stroma, at 80% depth from the thinnest part of the cornea as measured by the anterior segment OCT.
At 3 months following surgery, the Intacs SK group showed an increase in uncorrected distance visual acuity of logMAR 0.99 ± 0.35 at baseline to logMAR 0.29 ± 0.17, while the Keraring S16 group showed an increase in uncorrected visual acuity of log MAR 0.93 ± 0.4 at baseline to logMAR 0.41 ± 0.34. The keratometric values were reduced in both groups, which seems to indicate that ectasia was thwarted.
“Frequent postoperative controls are important to identify ectatic progression,” Dr. Seitz said. “Progression is defined as a function of the topographic refraction in the flat and steep axes. There is no progression if we observe no increase in K value of 1 D after two checkup exams within 6 months or any changes in visual acuity.”

When and how do ICRS work?

In a study that evaluated the outcomes of ICRS for the treatment of keratoconus, corrected distance visual acuity (CDVA) decreased significantly in patients with mild keratoconus (P<0.01) but significantly increased in all other grades (P<0.05). The improvement in visual acuity and the decrease of keratometric and aberrometric values were stable over a long period of time in eyes with stable keratoconus. Eyes with progressive keratoconus showed a significant improvement immediately after the procedure, then had a significant regression of greater than 3 D by the end of the follow-up period.2
The best indications for the implantation of ICRS were a loss of two or more lines of best corrected visual acuity after ectasia and eyes with post-LASIK ectasia grade 4, according to a study that evaluated the clinical results of ICRS in a large series of post-LASIK ectasia patients and determined which clinical parameters were related to the success of the technique. Patients who lost two or more lines due to ectasia had a mean gain of 2.89 lines of corrected distance visual acuity after ICRS implantation (P<.001). In contrast, patients who did not lose vision after ectasia had a mean loss of –2.00 lines of CDVA after ICRS implantation (P<.001). The study showed that the odds ratio of a gain of at least one line of CDVA was 18 times greater for those who had lost two or more lines after ectasia.3
“This study suggests that we keep in mind that patients who did not have visual loss from post-LASIK ectasia will have a greater risk of visual loss after the implantation of a ring segment,” Dr. Seitz said.
He explained that ICRS acts as placeholder between the loose collagen lamellae in the eyes of patients with keratectasia. “The arc shortening effect is proportional to the thickness of the ICRS and the optical zone size. The peripheral cornea at the site of the ICRS is ‘moved’ forward, thus flattening the central part of the cornea,” he said.
Indications for ICRS include moderate keratectasia (when it is “too early” for keratoplasty), contact lens intolerance, centrally clear cornea (no scars), steep K value below 62 D, corneal thickness at least 400 µm at the implantation site, and realistic expectations. Contraindications for ICRS are advanced keratectasia grade IV, severe atopy, corneal hydrops, herpetic keratitis, and collagen, vascular, and autoimmune disease.
“Post-LASIK corneal ectasia is one of the most troublesome complications after LASIK,” Dr. Seitz said. “Its incidence has been reported to be between 0.04% and 0.6%. It can occur several months or even years after laser surgery. Risk factors include abnormal preoperative corneal topography, low residual stromal bed thickness, young patient age, thin preoperative corneal thickness, and higher attempted refractive correction.”
According to his study outcomes, eyes with post-LASIK keratectasia benefited from Intacs SK implantation, improving both corrected and uncorrected visual acuity. Ectasia also seemed to be limited in these patients.

References

1. El-Husseiny M, et al. Intracorneal ring segments to treat keratectasia – interim results and potential complications. Klin Monbl Augenheilkd. 2016;233:722–6.
2. Alio JL, et al. Intrastromal corneal ring segments: how successful is the surgical treatment of keratoconus? Middle East Afr J Ophthalmol. 2014;21:3–9.
3. Brenner LF, et al. Indications for intrastromal corneal ring segments in ectasia after laser in situ keratomileusis. J Cataract Refract Surg. 2012;38:2117–24.

Editors’ note: Dr. Seitz has no financial interests related to his comments.

Contact information

Seitz
: berthold.seitz@uks.de

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