|Year : 2013 | Volume
| Issue : 3 | Page : 234-238
Efficacy of intacs intrastromal corneal ring segment relative to depth of insertion evaluated with anterior segment optical coherence tomography
Hassan Hashemi1, Alireza Yazdani-Abyaneh2, Amirhushang Beheshtnejad2, Mahmood Jabbarvand2, Ahmad Kheirkhah2, Seyed Reza Ghaffary2
1 Noor Ophthalmology Research Center, Noor Eye Hospital; Eye Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran
2 Eye Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran
|Date of Web Publication||9-Jul-2013|
Noor Eye Hospital, No 96, Esfandiar Blvd., Vali'asr Ave. Tehran, 19686-53111
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Aim: To evaluate the effect of implantation depth of Intacs microthin prescription inserts (Addition Technology Inc, Fremont, California) on visual and topographic outcomes in patients with post- laser-assisted in situ keratomileusis (LASIK) ectasias.
Settings and Design: Retrospective, observational case series.
Materials and Methods: In this case series, 16 eyes of 12 patients were evaluated. All cases were post-LASIK ectasia that had undergone intrastromal corneal ring segment (ICRS) implantation. The planned insertion depth was 70% of stromal thickness using a manual dissector. At least 12 months postoperatively, all eyes underwent Visante (Carl Zeiss Meditec) AS-OCT to determine insertion depth. Cases were categorized into 3 groups based on the measured implantation depth: 40-59% thickness; 60-79% thickness; and ≥80% thickness. Visual, refractive and topographic outcomes were evaluated relative to implantation depth.
Results: The lowest improvement in the study parameters ocurred when the implantation depth was ≥80%. In this group, uncorrected visual acuity (UCVA) and best spectacle corrected VA (BSCVA) improved less than 0.5 lines. Manifest refractive spherical equivalent (MRSE) and mean keratometry (Km) change was less than 0.5 diopters (D). The greatest improvements were observed with implantation depth of 60-79% where UCVA and BSCVA increased by 4.5 and 2.5 lines respectively, and MRSE and Km changed by approximately 2.00 D. Less improvement was found when ICRS were implanted between 40-59% of stromal thickness.
Conclusion: Implantation of ICRS greater than 80% of stromal thickness may have no effect on visual and topographic status.
Keywords: Intacs implantation depth, Laser-assisted in situ Keratomileusis, optical coherence tomography, post-lasik Ectasia, visual Acuity
|How to cite this article:|
Hashemi H, Yazdani-Abyaneh A, Beheshtnejad A, Jabbarvand M, Kheirkhah A, Ghaffary SR. Efficacy of intacs intrastromal corneal ring segment relative to depth of insertion evaluated with anterior segment optical coherence tomography. Middle East Afr J Ophthalmol 2013;20:234-8
|How to cite this URL:|
Hashemi H, Yazdani-Abyaneh A, Beheshtnejad A, Jabbarvand M, Kheirkhah A, Ghaffary SR. Efficacy of intacs intrastromal corneal ring segment relative to depth of insertion evaluated with anterior segment optical coherence tomography. Middle East Afr J Ophthalmol [serial online] 2013 [cited 2021 Jun 22];20:234-8. Available from: http://www.meajo.org/text.asp?2013/20/3/234/114800
| Introduction|| |
Intacs microthin prescription inserts (Addition Technology Inc, Fermont, California) were first developed for the correction of myopia from -1.0 to -3.0 diopters (D). , These intrastromal corneal ring segments (ICRS) are a 150 degree polymethyl methacrylate segment, hexagonal in cross-section, which are inserted deep into the stroma. ICRS implanation stretches the cornea peripherally resulting in central corneal flattening. ,
Colin et al.  were the first to implant ICRS for keratoconus. Subsequently, several authors reported on ICRS implantation for keratoconus, ,,,,,,,,,,,,,,,,, post-LASIK ectasia ,,,,,,,,,,, and pellucid marginal degeneration. ,,,,,, However, to the best of our knowledge, there are no reports on the effect of insertion or implantation depth of ICRS on the outcome. In this study we evaluate the outcome of Intacs ICRS implantation relative to the insertion depth as measured with anterior segment optical coherent tomography (AS-OCT).
| Materials and Methods|| |
In this retrospective study, we reviewed the records of all patients who underwent Intacs ICRS implantation for post-LASIK ectasia between 2006 and 2008. To be included all patients had to have greater than 1 year postoperative follow up. The Institutional Review Board of the Eye Research Center, Farabi Eye Hospital approved this study.
All surgeries were performed by an experienced surgeon (H.H). In all cases, 0.45 mm thick segments were implanted. A single segment was implanted for decentered cones, and double segments were implanted for central cones. Surgeries were performed with tetracaine as topical anesthesic. First, the geometric center of the cornea was marked with a blunt Sinskey hook. Then, using a circular marker, the 7.0 mm optical zone and the incision position in the flat meridian were marked. A 0.9 mm vertical incision was made with a calibrated diamond knife to a depth of 70% of the corneal thickness at the insertion location as measured preoperatively using the Pentacam rotating scheimflug camera (Oculus Gmbh, Wetzlar, Germany). After inspecting whether the depth of incision was adequate, a pocketing hook was applied to the base of the incision to create a pocket on either side taking care they were made to an equal level. After placing the vacuum centering guide, the corneal separator was inserted, and the clockwise and counterclockwise dissections were made. Next, the ICRS segment was manually introduced through the incision into the tunnel and advanced until the end was approximately 1.5mm from the incision. Finally, the incision was closed with a 10-0 nylon suture. After surgery, antibiotic and steroid eye-drops four times a day were prescribed, and the suture was removed after six weeks.
The following preoperative and postoperative data were evaluated: uncorrected visual acuity (UCVA); best spectacle corrected visual acuity (BSCVA); manifest refractive spherical equivalent (MRSE); refractive cylinder (RC); steep keratometry reading (K1), flat keratometry reading (K2), mean keratometry (K m =[K1+K2]/2), topographic cylinder (TC=K1-K2) from the EyeSys Corneal Analysis System (EyeSys Technologies, Houston, Tx, USA). UCVA and BSCVA were converted to logMAR for statistical analysis. AS-OCT was performed postoperatively using the Visante (Carl Zeiss Meditec, Jena, Germany) to determine the depth at which Intacs segments were implanted into the cornea. The depth of implanted segment was measured at the middle of its length. The stromal thickness was measured over (S1) and under (S2) the segment. Intacs depth was calculated as S1/(S1+S2), and the result was multiplied by 100 to determine the percent of stromal depth at which the ICRS had been inserted. If the two segments had been implanted, then the results of superior and inferior segments were averaged. The cases were categorized into 3 groups based on the measured depth of implantation: 40-59%, 60-79%, and ≥80% thickness depths. There were no cases with less than 40% implantation depth. Visual, refractive, and topographic outcomes were compared among the three groups.
Data were analyzed with the Statistical Package for Social Sciences software for windows (version 16.0, IBM Inc., Armonk, NY, USA). The Wilcoxon rank-sum test was used to compare preoperative and postoperative values of UCVA, BSCVA, MRSE, RC, K1, K2, K m , and TC. A p value less than 0.05 were statistically significant.
| Results|| |
Sixteen eyes of 12 patients were evaluated. The mean age of the patients was 33.25 ± 9.2 years (range, 25 years to 54 years) and the male/female and right/left eye ratios were 1:1. Mean follow up time was 23.8 ± 9.11 m (range, 12 m to 24 m). Based on AS-OCT measurements, we had 3 cases (18.8%) in the 40-59% thickness group, 9 cases (56.2%) in the 60-79% thickness, group and 4 cases (25.0%) in the ≥80% stromal thickness group. Results of the preoperative and last postoperative visits are summarized in [Table 1].
|Table 1: Mean (± standard deviation) values and changes of visual, refractive, and topographic variables before and after surgery in the entire study cohort|
Click here to view
Overall, UCVA changed by 0.32 ± 0.42 logMAR which is approximately a gain of 3 Snellen lines. BSCVA increased by 0.17 ± 0.25, which correlates a gain of 1.5 Snellen lines. Best outcomes were observed in the 60-79% thickness group. [Table 2] presents the visual outcomes relative to insertion depth.
|Table 2: Mean (±standard deviation) change (preoperative versus postoperative) in visual, refractive, and topographic variables relative to the depth of Intacs insertion|
Click here to view
Refractive and topographic outcome
Overall, MRSE and K m decreased by 1.57 ± 2.43 D and 1.6 ± 1.94 D respectively (p <0.05). The outcome was best when the ICRS were implanted to 60-79% of the stromal thickness; MRSE and K m change was 2.11 ± 3.11 D and 2.08 ± 2.40 D, respectively. When the ICRS were implanted into 80-99% of stromal depth, they had little to no effect [Table 2]. RC and TC did not show clinically or statistically significant changes as a result of surgery; overall RC and TC changes were 0.20 ±1.6 3 D and 0.32 ± 0.32 D, respectively (p >0.05, both cases). Astigmatism did not show clinically significant changes after ICRS implantation relative to depth of implantation (p >0.05; [Table 2]).
| Discussion|| |
Several authors have demonstrated that ICRS implantation in post-Lasik ectasia can improve UCVA and BCVA by approximately 70%. ,,,,,,,,,,, However, to the best of our knowledge, there are no reports evaluating the effect of implantation depth in the corneal stroma on the postoperative outcome after ICRS.
As demonstrated in [Table 2], UCVA, BSCVA, MRSE, and Km improved most significantly when the ICRS were implanted at 60-79% thickness, but there was little or no effect when the ICRS was implanted deeper than 80%. Results in the 40-59% thickness group were not as favorable as the 60-79% thickness group.
[Figure 1] shows the preoperative and postoperative topography of an eye with post-LASIK ectasia treated with a single ICRS inferiorly. AS-OCT showed a depth of 61% of stromal thickness [Figure 2]. Some steepening right above the Intacs that might lead to central flattening was observed. [Figure 3] shows the topography of the same patient's left eye which underwent implantation of a single ICRS inferiorly. However, this segment was inserted at 83% thickness [Figure 4]. No curvature change occurred over the ICRS and thus, no central flattening was expected. Corneal topography at 24 months postoperatively demonstrated no significant changes in keratometric power.
|Figure 1: Preoperative (a) and postoperative (b) topography of a patient right eye with post-LASIK ectasia that was implanted with a single intrastromal corneal ring segment|
Click here to view
|Figure 2: Anterior segment optical coherence tomography of the right eye|
Click here to view
|Figure 3: Preoperative (a) and postoperative (b) topography of the same patient left eye|
Click here to view
|Figure 4: Anterior segment optical coherence tomography of the left eye.|
Click here to view
| Conclusion|| |
The corneal stromal depth at which ICRS are implanted may be an important determinant of visual and topographic outcomes after surgery. Implanting ICRS too deep in the stroma (deeper than 80% stromal depth), may have no effect on the corneal curvature. The best stromal depth is 60-79%, and insertion in the stromal depth of 40-59% may have a lower effect.
| References|| |
|1.||Schanzlin DJ, Asbell PA, Burris TE, Durrie DS. The intrastromal corneal ring segments; phase II results for the correction of myopia. Ophthalmology 1997;104:1067-78. |
|2.||Burris TE. Intrastromal corneal ring technology: Results and indications. Curr Opin Ophthalmol 1998;9:9-14. |
|3.||Burris TE, Ayer CT, Evensen DA, Davenport JM. Effects of intrastromal corneal ring size and thickness on corneal flattening in human eyes. Refract Corneal Surg 1991;7:46-50. |
|4.||Burris TE, Baker PC, Ayer CT, Loomas BE, Mathis ML, Silvestrini TA. Flattening of central corneal curvature with intrastromal corneal rings of increasing thickness: An eyebank eye study. J Cataract Refract Surg 1993;19 Suppl:182-7. |
|5.||Colin J, Cochener B, Savary G, Malet F. Correcting keratoconus with intracorneal rings. J Cataract Refract Surg 2000;26:1117-22. |
|6.||Shetty R, Kurian M, Anand D, Mhaske P, Narayana KM, Shetty BK. Intacs in advanced keratoconus. Cornea 2008;27:1022-9. |
|7.||Ertan A, Ozkilic E. Effect of age on outcomes in patients with keratoconus treated by Intacs using a femtosecond laser. J Refract Surg 2008;24:690-5. |
|8.||Ertan A, Kamburoglu G. Intacs implantation using femtosecond laser for management of keratoconus: Comparison of 306 cases in different stages. J Cataract Refract Surg 2008;34:1521-6. |
|9.||Shabayek MH, Alió JL. Intrastromal corneal ring segment implantation by femtosecond laser for keratoconus correction. Ophthalmology 2007;114:1643-52. |
|10.||Zare MA, Hashemi H, Salari MR. Intracorneal ring segment implantation for the management of keratoconus: Safety and efficacy. J Cataract Refract Surg 2007;33:1886-91. |
|11.||Kymionis GD, Siganos CS, Tsiklis NS, Anastasakis A, Yoo SH, Pallikaris AI, et al. Long-term follow-up of Intacs in keratoconus. Am J Ophthalmol 2007;143:236-44. |
|12.||Alió JL, Shabayek MH, Artola A. Intracorneal ring segments for keratoconus correction: Long-term follow-up. J Cataract Refract Surg 2006;32:978-85. |
|13.||Alió JL, Shabayek MH, Belda JI, Correas P, Diez Feijoo E. Analysis of results related to good and bad outcomes of Intacs implantation for keratoconus correction. J Cataract Refract Surg 2006;32:756-61. |
|14.||Ertan A, Kamburoglu G, Bahadir M. Intacs insertion with the femtosecond laser for the management of keratoconus. One-year results. J Cataract Refract Surg 2006;32:2039-42. |
|15.||Colin J. European clinical evaluation: Use of Intacs for the treatment of keratoconus. J Cataract Refract Surg 2006;32:747-55. |
|16.||Kanellopoulos AJ, Pe LH, Perry HD, Donnenfeld ED. Modified intracorneal ring segment implantations (Intacs) for the management of moderate to advanced keratoconus. Efficacy and complications. Cornea 2006;25:29-33. |
|17.||Hellstedt T, Mäkelä J, Uusitalo R, Emre S, Uusitalo R. Treating keratoconus with Intacs corneal ring segments. J Refract Surg 2005;21:236-46. |
|18.||Kwitko S, Severo NS. Ferrara intracorneal ring segments for keratoconus. J Cataract Refract Surg 2004;30:812-20. |
|19.||Miranda D, Sartori M, Francesconi C, Allemann N, Ferrara P, Campos M. Ferrara intrastromal corneal ring segments for severe keratoconus. J Refract Surg 2003;19:645-53. |
|20.||Siganos CS, Kymionis GD, Kartakis N, Theodorakis MA, Astyrakakis N, Pallikaris IG. Management of keratoconus with Intacs. Am J Ophthalmol 2003;135:64-70. |
|21.||Boxer Wachler BS, Chandra NS, Chou B, Korn TS, Nepomuceno R, Christie JP. Intacs for keratoconus. Ophthalmology 2003;110:1031-40. |
|22.||Ruckhofer J, Stoiber J, Twa MD, Grabner G. Correction of astigmatism with short arc-length intrastromal corneal ring segments. Ophthalmology 2003;110:516-24. |
|23.||Colin J, Cochener B, Savary G, Malet F, Holmes- Higgin D. Intacs inserts for treating keratoconus. One year results. Ophthalmology 2001;108:1409-14. |
|24.||Carrasquillo KG, Rand J, Talamo JH. Intacs for keratoconus and post-LASIK ectasia: Mechanical versus femtosecond laser-assisted channel creation. Cornea 2007;26:956-62. |
|25.||Uceda-Montanes A, Toma´s JD, Alio´ JL. Correction of severe ectasia after LASIK with intracorneal ring segments. J Refract Surg 2008;24:408-13. |
|26.||Kymionis GD, Tsiklis NS, Pallikaris AI, Kounis G, Diakonis VF, Astyrakakis N, et al. Long-term follow-up of Intacs for post-LASIK corneal ectasia. Ophthalmology 2006;113:1909-17. |
|27.||Sharma M, Boxer Wachler BS. Comparison of single-segment and double-segment Intacs for keratoconus and post-LASIK ectasia. Am J Ophthalmol 2006;141:891-5. |
|28.||Polkroy R, Levinger S, Hirsh A. Single Intacs segment for postlaser in situ keratomileusis keratectasia. J Cataract Refract Surg 2004;30:1685-95. |
|29.||Gu¨ell JL, Velasco F, Sa´nchez SI, Gris O, Garcia-Rojas M. Intracorneal ring segments after laser in situ keratomileusis. J Refract Surg 2004;20:349-55. |
|30.||Kymionis GD, Siganos CS, Kounis G, Astyrakakis N, Kalyvianaki MI, Pallikaris IG. Management of post-LASIK corneal ectasia with Intacs inserts; One-year results. Arch Ophthalmol 2003;121:322-6. |
|31.||Siganos CS, Kymionis GD, Astyrakakis N, Pallikaris IG. Management of corneal ectasia after laser in situ keratomileusis with INTACS. J Refract Surg 2002;18:43-6. |
|32.||Lovisolo CF, Fleming JF. Intracorneal ring segments for iatrogenic keratectasia after laser in situ keratomileusis or photorefractive keratectomy. J Refract Surg 2002;18:535-41. |
|33.||Alio´ JL, Salem TF, Artola A, Osman AA. Intracorneal rings to correct corneal ectasia after laser in situ keratomileusis. J Cataract Refract Surg 2002;28:1568-74. |
|34.||Piñero DP, Alio JL, Uceda-Montanes A, El Kady B, Pascual I. Intracorneal Ring Segment Implantation in Corneas with Post-Laser In Situ Keratomileusis Keratectasia. Ophthalmology 2009;116:1665-74. |
|35.||Piñero DP, Alió JL, El Kady B, Pascual I. Corneal aberrometric and refractive performance of 2 intrastromal corneal ring segment models in early and moderate ectatic disease. J Cataract Refract Surg 2010;36:102-9. |
|36.||Ertan A, Bahadir M. Management of superior pellucid marginal degeneration with a single intracorneal ring segment using femtosecond laser. J Refract Surg 2007;23:205-8. |
|37.||Ertan A, Bahadir M. Intrastromal ring segment insertion using a femtosecond laser to correct pellucid marginal corneal degeneration. J Cataract Refract Surg 2006;32:1710-6. |
|38.||Mularoni A, Torreggiani A, Di Biase A, Laffi GL, Tassinari G. Conservative treatment of early and moderate pellucid marginal degeneration: A new refractive approach with intracorneal rings. Ophthalmology 2005;112:660-6. |
|39.||Barbara A, Shehadeh-Masha'our R, Zvi R, Garzozi HJ. Management of pellucid marginal degeneration with intracorneal ring segments. J Refract Surg 2005;21:296-8. |
|40.||Akaishi L, Tzelikis PF, Raber IM. Ferrara intracorneal ring implantation and cataract surgery for the correction of pellucid marginal corneal degeneration. J Cataract Refract Surg 2004;30:2427-30. |
|41.||Kymionis GD, Aslanides IM, Siganos CS, Pallikaris IG. Intacs for early pellucid marginal degeneration. J Cataract Refract Surg 2004;30:230-3. |
|42.||Rodriguez-Prats J, Galal A, Garcia-Lledo M, De la Hoz F, Alió JL. Intracorneal rings for the correction of pellucid marginal degeneration. J Cataract Refract Surg 2003;29:1421-4. |
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2]