Description　　
Intrastromal corneal ring segments (ICRS) are composed of microthin soft plastic inserts of variable thickness that are placed in the periphery of the cornea. They have been investigated as a means of improving vision in diseases such as keratoconus and pellucid marginal degeneration, and for astigmatism following penetrating keratoplasty (PK).

For individuals who have keratoconus who receive ICRS, the evidence includes primarily single-institution case series. Relevant outcomes are change in disease status, functional outcomes, and treatment-related morbidity. A number of single-center case series with sample sizes ranging from 19 to 105 eyes have been published. These series have generally reported that a substantial proportion of patients with keratoconus treated with this device have improved vision at 1 to 2 years of follow-up. More limited data are available on long-term efficacy. ICRS is associated with a number of adverse events and explantation. The net health outcome is uncertain. The evidence is insufficient to determine the effects of the technology on health outcomes.

Clinical input strongly supported the use of ICRS in a select group of patients with advanced keratoconus whose only other option for restoration of functional vision was the more invasive PK. Some clinicians may opt to delay a more invasive procedure, although the success rate of this strategy is as yet unproven. Therefore, use of ICRS may be considered medically necessary in patients with keratoconus who meet the U.S. Food and Drug Administration humanitarian device exemption criteria for use of this device. 

For individuals who have pellucid marginal degeneration who receive ICRS, the evidence includes a few case series. Relevant outcomes are change in disease status, functional outcomes, and treatment-related morbidity. A small number of case series with fewer than 25 eyes per study have been published on ICRS in patients with pellucid marginal degeneration. Most reports have assessed devices not available in the United States. In 1 study, which included some patients implanted with Intacs, there was no improvement in uncorrected visual acuity 6 months after surgery. Moreover, explantation occurred in about 20% of eyes due to visual deterioration. The evidence is insufficient to determine the effects of the technology on health outcomes.

For individuals who have astigmatism after PK who receive ICRS, the evidence includes a few case series. Relevant outcomes are change in disease status, functional outcomes, and treatment-related morbidity. Two case series, with 9 and 54 patients, were identified; both used devices not available in the United States. ICRS was associated with adverse events such as extrusion and Descemet membrane detachment. The evidence is insufficient to determine the effects of the technology on health outcomes.

Background 
Vision Disorders
Keratoconus is a progressive bilateral dystrophy characterized by paracentral steepening and stromal thinning that impairs visual acuity.

Pellucid marginal degeneration is a noninflammatory progressive degenerative disease, typically characterized by bilateral peripheral thinning (ectasia) of the inferior cornea. Deterioration of functional vision results from the irregular astigmatism induced by asymmetric distortion of the cornea, and visual acuity typically cannot be restored by using spherocylindrical lenses. 

Treatment 
Initial treatment for keratoconus often consists of hard contact lenses. A penetrating keratoplasty (i.e., corneal grafting) was traditionally considered the next line of treatment in patients who developed intolerance to contact lenses. While visual acuity is typically improved with penetrating keratoplasty, perioperative complications are an associated risk; long-term topical steroid use is required; and endothelial cell loss occurs over time, which is a particular concern in younger patients. As an alternative, a variety of keratorefractive procedures have been attempted, broadly divided into subtractive and additive techniques. Subtractive techniques include photorefractive keratectomy or laser in situ keratomileusis (LASIK), although, generally, results of these techniques have been poor. In deep anterior lamellar keratoplasty, pathologic corneal stromal tissue is selectively removed to the level of the Descemet membrane, followed by transplantation of a donor graft. Implantation of intrastromal corneal ring segments (ICRS) represents an additive technique, in which the implants are intended to reinforce the cornea, prevent further deterioration, and potentially obviate the need for penetrating keratoplasty.

Rigid gas permeable contact lenses may be used to treat pellucid marginal degeneration. ICRS, crescentic lamellar keratoplasty, penetrating keratoplasty, and corneal wedge excision have also been proposed as treatments.

ICRS correct myopia by flattening the center of the cornea and represent an alternative to LASIK and other refractive surgeries. A proposed advantage of ICRS is that their insertion does not affect the central cornea and, thus, their effect is not related to the healing process in the cornea. No corneal tissue is removed, and the implants may be removed or replaced. However, mild myopia is effectively treated with spectacles or contact lenses. 

Intrastromal Corneal Ring Segments 
ICRS are composed of microthin soft plastic inserts of variable thickness that are placed in the periphery of the cornea. They are inserted through an incision made in the cornea, into which channels have been created by rotating a lamellar dissector or by using a femtosecond laser. One or 2 segments are implanted in each channel, and various implants with a range of thicknesses are available for different degrees of correction. They affect refraction in the eye by physically changing the shape of the cornea (flattening the front of the eye), thereby correcting the irregular corneal shape and restoring a degree of functional vision. If required, the implants can be removed or replaced at a later date.

Regulatory Status
Intacs^®, an intrastromal corneal ring, was approved by the U.S. Food and Drug Administration (FDA) for 2 indications. In 1999, Intacs^® (KeraVision, now Addition Technology) was approved by FDA through the premarket approval process for the following labeled indication:

“The KeraVision Intacs are intended for the reduction or elimination of mild myopia (-1.00 to -3.00 diopters spherical equivalent at the spectacle plane) in patients:

• Who are 21 years of age or older.
• With documented stability of refraction as demonstrated by a change of less than or equal to 0.50 diopter for at least 12 months prior to the preoperative examination.
• Where the astigmatic component is +1.00 diopter or less.”

In 2004, Intacs^® received additional approval by FDA through the humanitarian device exemption process for the following indication:

“This device is indicated for the reduction or elimination of myopia and astigmatism in patients with keratoconus, who are no longer able to achieve adequate vision with their contact lenses or spectacles, so that their functional vision may be restored and the need for a corneal transplant procedure may potentially be deferred. The specific set of keratoconic patients proposed to be treated with Intacs prescription inserts are those patients:

• Who have experienced a progressive deterioration in their vision, such that they can no longer achieve adequate functional vision on a daily basis with their contact lenses or spectacles;
• Who are 21 years of age or older;
• Who have clear central corneas;
• Who have a corneal thickness of 450 microns or greater at the proposed incision site; AND
• Who have corneal transplantation as the only remaining option to improve their functional vision.”

Note: The humanitarian device exemption does not require manufacturers to provide data confirming the efficacy of a device but rather data supporting its “probable” benefit. The humanitarian device exemption process is available for devices treating conditions that affect fewer than 4000 Americans per year.

ICRS devices available outside of the United States include:

• Intacs SK
• Ferrara intrastromal corneal ring segments
• KeraRing intrastromal corneal ring segments
• MyoRing intracorneal continuous ring.

FDA product code: LQE.

Related Policies
90301 Keratoprosthesis
90322 Endothelial Keratoplasty
90328 Corneal Collagen Cross-linking

Policy:
Implantation of intrastromal corneal ring segments may be considered MEDICALLY NECESSARY for the treatment of keratoconus in patients 21 years of age or older who meet the following criteria:

Implantation of intrastromal corneal ring segments is considered NOT MEDICALLY NECESSARY as a treatment of myopia.

Implantation of intrastromal corneal ring segments is considered investigational and/or unproven and therefore NOT MEDICALLY NECESSARY for all other conditions.

Policy Guidelines 
There is a category I CPT code for this procedure:

65785: Implantation of intrastromal corneal ring segments

Benefit Application
BlueCard/National Account Issues
Some Plan benefits or contracts may include an exclusion for refractive eye surgery that would apply to the use of intrastromal corneal ring segments as a treatment of mild myopia.

State or federal mandates (e.g., FEP) may dictate that all devices approved by the U.S. Food and Drug Administration (FDA) may not be considered investigational, and thus these devices may be assessed only on the basis of their medical necessity.

Rationale 
Evidence reviews assess the clinical evidence to determine whether the use of technology improves the net health outcome. Broadly defined, health outcomes are the length of life, quality of life, and ability to function including benefits and harms. Every clinical condition has specific outcomes that are important to patients and managing the course of that condition. Validated outcome measures are necessary to ascertain whether a condition improves or worsens; and whether the magnitude of that change is clinically significant. The net health outcome is a balance of benefits and harms.

To assess whether the evidence is sufficient to draw conclusions about the net health outcome of technology, 2 domains are examined: the relevance, and quality and credibility. To be relevant, studies must represent 1 or more intended clinical use of the technology in the intended population and compare an effective and appropriate alternative at a comparable intensity. For some conditions, the alternative will be supportive care or surveillance. The quality and credibility of the evidence depend on study design and conduct, minimizing bias and confounding that can generate incorrect findings. The randomized controlled trial (RCT) is preferred to assess efficacy; however, in some circumstances, nonrandomized studies may be adequate. RCTs are rarely large enough or long enough to capture less common adverse events and long-term effects. Other types of studies can be used for these purposes and to assess generalizability to broader clinical populations and settings of clinical practice.

Keratoconus
Clinical Context and Therapy Purpose
The purpose of intrastromal corneal ring segments is to provide a treatment option that is an alternative to or an improvement on penetrating keratoplasty, in patients with keratoconus.

The question addressed in this evidence review is: Does intrastromal corneal ring segments improve the net health outcome in patients with keratoconus.

The following PICO was used to select literature to inform this review.

Populations
The relevant population of interest is individuals with keratoconus.

Interventions
The intervention of interest is intrastromal corneal ring segments.

Comparators
The comparator of interest is penetrating keratoplasty.

Outcomes
The beneficial outcomes of interest are change in disease status, functional outcomes, and treatment-related morbidity.

Study Selection Criteria
Methodologically credible studies were selected using the following principles:

1. To assess efficacy outcomes, comparative controlled prospective trials were sought, with a preference for RCTs.
2. In the absence of such trials, comparative observational studies were sought, with a preference for prospective studies.
3. To assess longer-term outcomes and adverse events, single-arm studies that capture longer periods of follow-up and/or larger populations were sought.
4. Studies with duplicative or overlapping populations were excluded.

Review of Evidence
According to a Cochrane review by Zadnik et al. (2019), there are no published RCTs of intrastromal corneal ring segments for treating keratoconus.¹ The published data on Intacs for keratoconus consists of single-institution case series, many of which used the device commercially available in the United States. ^{2,3,4,5,6,7,8,9,10,11,12,13,14,15} Sample sizes ranged from 19 to 105 eyes. Findings from a systematic review of case series by Izquierdo et al. (2019) (N = 1325 eyes) indicated that intrastromal corneal ring implantation improved uncorrected distance visual acuity (0.23 ± 0.28, Logarithm of the Minimum Angle of Resolution) and corrected distance visual acuity (0.06 ± 0.21, Logarithm of the Minimum Angle of Resolution) at 12 months.¹⁶ Additionally, these case series have indicated that a substantial proportion of patients with keratoconus treated with this device have improved vision at 1 to 2 years of follow-up. Most studies have reported improvements (in uncorrected or corrected visual acuity) in at least 75% to 80% of patients in whom changes in 2 to 3 lines of corrected or uncorrected visual acuity were considered a success. ^3,4,5,7,11 Approximately 10% of patients required a second procedure because of an unsatisfactory initial result.^5,6

One of the larger studies was published by Colin and Malet (2007).¹² They reported on 2-year follow-up from a prospective, single-center European study in 100 eyes with keratoconus (82 consecutive patients) and Intacs implantation. Patients had been referred for a penetrating keratoplasty procedure due to contact lens intolerance for correction of myopia and irregular astigmatism. Intacs inserts were removed from 4 (4%) eyes due to poor visual outcome or extrusion, and 14 eyes were lost to follow-up. Of the 82 remaining eyes (68 patients), both corrected and uncorrected visual acuity remained relatively stable between 1 and 2 years of follow-up.

Studies with 5 years of follow-up include Bedi et al. (2012).¹³ They evaluated the risk of keratoconus progression in a study of 105 consecutive eyes (85 patients) that had undergone Intacs implantation. At the 1-year follow-up, 1 eye had extrusion and 12 (11.4%) had undergone removal of Intacs because of unsatisfactory results; these eyes were managed by penetrating or deep lamellar keratoplasty. Of the 105 eyes, 80% retained the Intacs implant and showed no keratoconus progression over 5 years of follow-up. In addition, Vega-Estrada et al. (2013) reported that, in a series of 51 eyes, the improvement in vision obtained at 6 months after Intacs implantation was maintained out to 5 years postoperatively. ² However, the analysis only included cases without significant changes in corneal topography over the 12 months prior to surgery. Kymionis et al. (2007) reported on 5-year follow-up on 28 patients (36 eyes) who had initially participated in a clinical trial evaluating the safety and efficacy of Intacs implantation in patients with keratoconus.¹⁴ In 5 patients (7 eyes), the Intacs segments were removed due to patient dissatisfaction. Five-year follow-up was reported for 17 (59%) eyes. Refractive stability was obtained at the 6-month follow-up and remained stable throughout the 5-year follow-up. Alternatively, Kang et al. (2019) reported mixed visual acuity findings at the 5-year follow-up for 30 eyes. While improvements in corrected distance visual acuity were maintained at 5 years, compared to preoperative values, uncorrected distance visual acuity and spherical and spherical equivalent worsened at 5 years.¹⁷

For adverse events, a larger retrospective study by Nguyen et al. (2019)¹⁸ evaluated a consecutive series of 572 eyes with femtosecond laser-created Intacs intracorneal ring implantation for keratoconus or corneal ectasia to assess the incidence of explantation and its determinants. Overall, the intracorneal ring segments (Intacs) were explanted in 35 eyes (6.1%) of 31 patients. Explantation was due to medical complications in 15 eyes (2.6%), most frequently being keratitis with signs of inflammation (n = 11, 31%). A total of 20 (3.8%) explantations were due to optical/refractive considerations. Use of adjunctive corneal crosslinking did not affect explantation risk.

Section Summary: Keratoconus
For individuals who have keratoconus who receive intrastromal corneal ring segments, the evidence includes case series. Relevant outcomes are change in disease status, functional outcomes, and treatment-related morbidity. A number of single-center case series with sample sizes ranging from 19 to 105 eyes have been published. The series has generally reported that a substantial proportion of patients with keratoconus treated with this device have improved vision at 1 to 2 years of follow-up. A single case series of 572 eyes have suggested that risk of explantation may be modest (6.1%). However, long-term data are more limited.

Pellucid Marginal Degeneration
Clinical Context and Therapy Purpose
The purpose of intrastromal corneal ring segments is to provide a treatment option that is an alternative to or an improvement on penetrating keratoplasty, in patients with pellucid marginal degeneration.

The question addressed in this evidence review is: Does intrastromal corneal ring segments improve the net health outcome in patients with pellucid marginal degeneration.

The following PICO was used to select literature to inform this review.

Populations
The relevant population of interest is individuals with pellucid marginal degeneration.

Interventions
The intervention of interest is intrastromal corneal ring segments.

Comparators
The comparator of interest is penetrating keratoplasty.

Outcomes
The beneficial outcomes of interest are change in disease status, functional outcomes, and treatment-related morbidity.

Study Selection Criteria
Methodologically credible studies were selected using the following principles:

1. To assess efficacy outcomes, comparative controlled prospective trials were sought, with a preference for RCTs. 
2. In the absence of such trials, comparative observational studies were sought, with a preference for prospective studies.
3. To assess longer-term outcomes and adverse events, single-arm studies that capture longer periods of follow-up and/or larger populations were sought.
4. Studies with duplicative or overlapping populations were excluded.

Review of Evidence
Pinero et al. (2009) published a European multicenter retrospective analysis of 21 consecutive eyes in 15 patients who had been implanted with intrastromal corneal ring segments (3 Intacs, 18 KeraRings) for pellucid marginal degeneration. All subjects had experienced reduced best spectacle-corrected visual acuity and/or contact lens intolerance or dissatisfaction prior to implantation.¹⁹ At 6 months after surgery, uncorrected visual acuity had not changed; 17% of eyes lost lines of best-corrected visual acuity, and 44% of eyes gained 2 or more lines of best spectacle-corrected visual acuity.

Ring explantation was performed in 4 (19%) eyes due to visual deterioration during the follow-up. Mean keratometry decreased 1.76 diopters (D), from 44.95 to 43.19 D at 6 months postoperatively (p < 0.01).

A 2010 publication from Europe retrospectively analyzed intrastromal corneal ring segments implantation (KeraRing) in 16 consecutive eyes of 10 patients with pellucid marginal degeneration who had reduced best spectacle-corrected visual acuity and dissatisfaction with spectacle and contact lens-corrected vision.²⁰ At 12 months after implantation, uncorrected visual acuity improved from 1.69 to 0.83 (Logarithm of the Minimum Angle of Resolution). At the 36-month follow-up, patients (n = 11 eyes) had gained a mean of 2.4 lines uncorrected visual acuity and 3.3 lines of best spectacle-corrected visual acuity. There was a statistically significant reduction in manifest spherical refraction from -2.43 to -0.72 D. For the patients (n = 11 eyes) who completed 36-month follow-up, there was no significant change in outcome measures between 12 and 36 months. No intraoperative or postoperative complications were noted aside from white deposits around the segments in 1 patient.

Section Summary: Pellucid Marginal Degeneration
For individuals who have pellucid marginal degeneration who receive intrastromal corneal ring segments, the evidence includes only a few case series, most of which have assessed devices not available in the United States. Relevant outcomes are change in disease status, functional outcomes, and treatment-related morbidity. In 1 study, which included some patients implanted with Intacs, there was no improvement in uncorrected visual acuity 6 months after surgery. Moreover, explantation occurred in about 20% of eyes due to visual deterioration.

Astigmatism After Penetrating Keratoplasty
Clinical Context and Therapy Purpose
The purpose of intrastromal corneal ring segments is to provide a treatment option that is an alternative to or an improvement on penetrating keratoplasty, in patients with astigmatism after penetrating keratoplasty.

The question addressed in this evidence review is: Does intrastromal corneal ring segments improve the net health outcome in patients with astigmatism after penetrating keratoplasty.

The following PICO was used to select literature to inform this review.

Populations
The relevant population of interest is individuals with astigmatism after penetrating keratoplasty.

Interventions
The intervention of interest is intrastromal corneal ring segments.

Comparators
The comparator of interest is penetrating keratoplasty.

Outcomes
The beneficial outcomes of interest are change in disease status, functional outcomes, and treatment-related morbidity.

Study Selection Criteria
Methodologically credible studies were selected using the following principles:  

1. To assess efficacy outcomes, comparative controlled prospective trials were sought, with a preference for RCTs. 
2. In the absence of such trials, comparative observational studies were sought, with a preference for prospective studies.
3. To assess longer-term outcomes and adverse events, single-arm studies that capture longer periods of follow-up and/or larger populations were sought.
4. Studies with duplicative or overlapping populations were excluded.

Review of Evidence
Two case series (2009, 2012) were identified in which intrastromal corneal ring segments were implanted to correct residual astigmatism after penetrating keratoplasty.^21,22 In 1, conducted in Spain, 9 patients received intrastromal corneal ring segments (KeraRings) for high astigmatism ( > 4 D) after the procedure.²¹ Mean keratometry decreased 4.17 D (from 46.28 to 42.11 D). Of the 9 patients, 1 reported night halos and 2 had the implant removed due to compulsive eye rubbing and vascularization in the stromal tunnel. The authors noted that, in patients with a corneal transplant with a diameter of 7.5 mm or smaller, intrastromal corneal ring segments should not be used because the segments would be proximate to the graft-host junction. In another study, Coscarelli et al. (2012) in Brazil retrospectively reviewed chart records of 54 patients (59 eyes) who had intrastromal corneal ring segments with the Ferrara ring.²² Mean corrected distance visual acuity improved from 0.45 Logarithm of the Minimum Angle of Resolution preoperatively to 0.30 Logarithm of the Minimum Angle of Resolution postoperatively. Mean corneal topographic astigmatism decreased from 3.37 D preoperatively to 1.69 D postoperatively.

Section Summary: Astigmatism After Penetrating Keratoplasty
For individuals who have astigmatism after penetrating keratoplasty who receive intrastromal corneal ring segments, the evidence includes 2 case series. Relevant outcomes are change in disease status, functional outcomes, and treatment-related morbidity. The case series (n = 9 and 54, respectively) were identified assessing intrastromal corneal ring segments in patients with astigmatism after penetrating keratoplasty. Neither provides evidence relevant to this review because both were conducted outside of the United States and used devices not cleared by the U.S. Food and Drug Administration.

Adverse Events
Literature searches have identified case reports of adverse events following implantation of intrastromal corneal ring segments, including persistent pain, extrusion, traumatic shattering, bacterial keratitis, fungal keratitis, corneal edema, deep corneal vascularization, Descemet membrane detachment, and alterations of extracellular matrix components and proteinases. In a 2010 multicenter series of 251 intrastromal corneal ring segments implantations, 58 eyes of 47 patients had the devices explanted.²³ The main cause was extrusion (48%), followed by poor refractive outcomes (38%), keratitis (7%), and corneal melting and perforation (7%). The time from implantation to explantation ranged from 0.1 to 82 months.

In another study (2006), 6 of 20 eyes had “significant” problems at 3 to 6 months postoperatively related to corneal thinning and subsequent ring exposure, and a dense corneal infiltrate developed in 1 patient at 7 months.²⁴ Histopathologic examination of 8 eyes that underwent penetrating keratoplasty after removal of Intacs implants revealed keratocyte apoptosis.²⁵

Summary of Evidence
For individuals who have keratoconus who receive intrastromal corneal ring segments, the evidence includes primarily single-institution case series. Relevant outcomes are change in disease status, functional outcomes, and treatment-related morbidity. A number of single-center case series with sample sizes ranging from 19 to 105 eyes have been published. These series have generally reported that a substantial proportion of patients with keratoconus treated with this device have improved vision at 1 to 2 years of follow-up. More limited data are available on long-term efficacy. Intrastromal corneal ring segments is associated with a number of adverse events and explantation. Although, a single case series of 572 eyes have suggested that risk of explantation may be modest (6.1%). The net health outcome is uncertain. The evidence is insufficient to determine that the technology results in an improvement in the net health outcome.

For individuals who have pellucid marginal degeneration who receive intrastromal corneal ring segments, the evidence includes a few case series. Relevant outcomes are change in disease status, functional outcomes, and treatment-related morbidity. A small number of case series with fewer than 25 eyes per study have evaluated intrastromal corneal ring segments in patients with pellucid marginal degeneration. Most reports have assessed devices not available in the United States. In 1 study, which included some patients implanted with Intacs, there was no improvement in uncorrected visual acuity 6 months after surgery. Moreover, explantation occurred in about 20% of eyes due to visual deterioration. The evidence is insufficient to determine that the technology results in an improvement in the net health outcome.

For individuals who have astigmatism after penetrating keratoplasty who receive intrastromal corneal ring segments, the evidence includes a few case series. Relevant outcomes are change in disease status, functional outcomes, and treatment-related morbidity. Two case series, with 9 and 54 patients, were identified; both used devices not available in the United States. Intrastromal corneal ring segments was associated with adverse events such as extrusion and Descemet membrane detachment. The evidence is insufficient to determine that the technology results in an improvement in the net health outcome. 

The purpose of the following information is to provide reference material. Inclusion does not imply endorsement or alignment with the evidence review conclusions.

Clinical Input From Physician Specialty Societies and Academic Medical Centers
While the various physician specialty societies and academic medical centers may collaborate with and make recommendations during this process, through the provision of appropriate reviewers, input received does not represent an endorsement or position statement by the physician specialty societies or academic medical centers, unless otherwise noted.

In response to requests, input was received through 1 physician specialty society and 3 academic medical centers while this policy was under review in 2009. Input considered implantation of intrastromal corneal ring segments to be medically necessary for select patients with keratoconus when the only other option for improving visual acuity is corneal transplantation. Input agreed that implantation of intrastromal corneal ring segments is not medically necessary for treatment of myopia.

Practice Guidelines and Position Statements
Guidelines or position statements will be considered for inclusion in ‘Supplemental Information’ if they were issued by, or jointly by, a U.S. professional society, an international society with U.S. representation, or National Institute for Health and Care Excellence (NICE). Priority will be given to guidelines that are informed by a systematic review, include strength of evidence ratings, and include a description of management of conflict of interest.

In 2007, the National Institute for Health and Care Excellence (NICE) issued guidance on corneal implants for keratoconus.²⁶ The guidance, based on 9 case series, a nonrandomized controlled trial, and specialists’ opinions, concluded, “Current evidence on the safety and efficacy of corneal implants for keratoconus appears adequate to support the use of this procedure…”

U.S. Preventive Services Task Force Recommendations
Not applicable

Ongoing and Unpublished Clinical Trials
Some currently unpublished trials that might influence this review are listed in Table 1.

Table 1. Summary of Key Trials 

NCT: national clinical trial. 

References:

1. Zadnik K, Money S, Lindsley K. Intrastromal corneal ring segments for treating keratoconus. Cochrane Database Syst Rev. May 14 2019; 5: CD011150. PMID 31087649
2. Vega-Estrada A, Alio JL, Brenner LF, et al. Outcomes of intrastromal corneal ring segments for treatment of keratoconus: five-year follow-up analysis. J Cataract Refract Surg. Aug 2013; 39(8): 1234-40. PMID 23747207
3. Alio JL, Shabayek MH, Belda JI, et al. Analysis of results related to good and bad outcomes of Intacs implantation for keratoconus correction. J Cataract Refract Surg. May 2006; 32(5): 756-61. PMID 16765791
4. Boxer Wachler BS, Christie JP, Chandra NS, et al. Intacs for keratoconus. Ophthalmology. May 2003; 110(5): 1031-40. PMID 12750109
5. Colin J. European clinical evaluation: use of Intacs for the treatment of keratoconus. J Cataract Refract Surg. May 2006; 32(5): 747-55. PMID 16765790
6. Levinger S, Pokroy R. Keratoconus managed with intacs: one-year results. Arch Ophthalmol. Oct 2005; 123(10): 1308-14. PMID 16219721
7. Siganos CS, Kymionis GD, Kartakis N, et al. Management of keratoconus with Intacs. Am J Ophthalmol. Jan 2003; 135(1): 64-70. PMID 12504699
8. Ziaei M, Barsam A, Shamie N, et al. Reshaping procedures for the surgical management of corneal ectasia. J Cataract Refract Surg. Apr 2015; 41(4): 842-72. PMID 25840308
9. Beniz LA, Queiroz GH, Queiroz CF, et al. Intrastromal corneal ring segments delay corneal grafting in patients with keratoconus. Arq Bras Oftalmol. Feb 2016; 79(1): 30-2. PMID 26840163
10. Heikal MA, Abdelshafy M, Soliman TT, et al. Refractive and visual outcomes after Keraring intrastromal corneal ring segment implantation for keratoconus assisted by femtosecond laser at 6 months follow-up. Clin Ophthalmol. 2017; 11: 81-86. PMID 28096650
11. Miraftab M, Hashemi H, Hafezi F, et al. Mid-Term Results of a Single Intrastromal Corneal Ring Segment for Mild to Moderate Progressive Keratoconus. Cornea. May 2017; 36(5): 530-534. PMID 27984365
12. Colin J, Malet FJ. Intacs for the correction of keratoconus: two-year follow-up. J Cataract Refract Surg. Jan 2007; 33(1): 69-74. PMID 17189796
13. Bedi R, Touboul D, Pinsard L, et al. Refractive and topographic stability of Intacs in eyes with progressive keratoconus: five-year follow-up. J Refract Surg. Jun 2012; 28(6): 392-6. PMID 22589292
14. Kymionis GD, Siganos CS, Tsiklis NS, et al. Long-term follow-up of Intacs in keratoconus. Am J Ophthalmol. Feb 2007; 143(2): 236-244. PMID 17184717
15. Fernandez-Vega Cueto L, Lisa C, Poo-Lopez A, et al. Intrastromal Corneal Ring Segment Implantation in 409 Paracentral Keratoconic Eyes. Cornea. Nov 2016; 35(11): 1421-1426. PMID 27490048
16. Izquierdo L, Mannis MJ, Mejias Smith JA, et al. Effectiveness of Intrastromal Corneal Ring Implantation in the Treatment of Adult Patients With Keratoconus: A Systematic Review. J Refract Surg. Mar 01 2019; 35(3): 191-200. PMID 30855097
17. Kang MJ, Byun YS, Yoo YS, et al. Long-term outcome of intrastromal corneal ring segments in keratoconus: Fiveyear follow up. Sci Rep. Jan 22 2019; 9(1): 315. PMID 30670787
18. Nguyen N, Gelles JD, Greenstein SA, et al. Incidence and associations of intracorneal ring segment explantation. J Cataract Refract Surg. Feb 2019; 45(2): 153-158. PMID 30509748
19. Pinero DP, Alio JL, Morbelli H, et al. Refractive and corneal aberrometric changes after intracorneal ring implantation in corneas with pellucid marginal degeneration. Ophthalmology. Sep 2009; 116(9): 1656-64. PMID 19643482
20. Kubaloglu A, Sari ES, Cinar Y, et al. A single 210-degree arc length intrastromal corneal ring implantation for the management of pellucid marginal corneal degeneration. Am J Ophthalmol. Aug 2010; 150(2): 185-192.e1. PMID 20570241
21. Arriola-Villalobos P, Diaz-Valle D, Guell JL, et al. Intrastromal corneal ring segment implantation for high astigmatism after penetrating keratoplasty. J Cataract Refract Surg. Nov 2009; 35(11): 1878-84. PMID 19878819
22. Coscarelli S, Ferrara G, Alfonso JF, et al. Intrastromal corneal ring segment implantation to correct astigmatism after penetrating keratoplasty. J Cataract Refract Surg. Jun 2012; 38(6): 1006-13. PMID 22624900
23. Ferrer C, Alio JL, Montanes AU, et al. Causes of intrastromal corneal ring segment explantation: clinicopathologic correlation analysis. J Cataract Refract Surg. Jun 2010; 36(6): 970-7. PMID 20494769
24. Kanellopoulos AJ, Pe LH, Perry HD, et al. Modified intracorneal ring segment implantations (INTACS) for the management of moderate to advanced keratoconus: efficacy and complications. Cornea. Jan 2006; 25(1): 29-33. PMID 16331037
25. Samimi S, Leger F, Touboul D, et al. Histopathological findings after intracorneal ring segment implantation in keratoconic human corneas. J Cataract Refract Surg. Feb 2007; 33(2): 247-53. PMID 17276265
26. National Institute for Health and Care Excellence (NICE). Corneal implants for keratoconus [IPG227]. 2007; https://www.nice.org.uk/guidance/IPG227. Accessed February 11, 2021. 

Coding Section

Procedure and diagnosis codes on Medical Policy documents are included only as a general reference tool for each policy. They may not be all-inclusive. 

This medical policy was developed through consideration of peer-reviewed medical literature generally recognized by the relevant medical community, U.S. FDA approval status, nationally accepted standards of medical practice and accepted standards of medical practice in this community, Blue Cross Blue Shield Association technology assessment program (TEC) and other non-affiliated technology evaluation centers, reference to federal regulations, other plan medical policies and accredited national guidelines.

"Current Procedural Terminology^© American Medical Association. All Rights Reserved" 

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