Intrastromal corneal ring segments for management of keratoconus

Keratoconus is a progressive corneal ectasia, which can be managed both by conservative measures like glasses or contact lenses in non-progressive cases or surgical procedures like collagen crosslinking (CXL) with or without adjuvant measures like intrastromal corneal rings segments (ICRS) or topography guided ablation. Various kinds of ICRS are available to the surgeon, but it is most essential to be able to plan the implantation of the ring to optimize outcomes.

Aims:

The aim of this study is to evaluate the visual outcome and progression in patients of keratoconus implanted with ICRS.

Materials and Methods:

Two different types of ICRS-Intacs (Addition Technology) and Kerarings (Mediphacos Inc.) were implanted in 2 different cohorts of patients and were followed-up to evaluate the outcome of the procedure. All patients underwent a complete ocular examination including best spectacle corrected visual acuity, slit lamp examination fundus examination, corneal topography and pachymetry. The ICRS implantation is done with CXL to stop the progression of the disease. Improvement in uncorrected visual acuity (UCVA), best spectacle corrected visual acuity and topographic changes were analyzed.

Results:

A significant improvement in keratometry and vision was seen in both groups.

Conclusion:

ICRS have been found to reduce corneal irregularity and flatten keratometry with improvement in UCVA and best corrected visual acuity.     

Clinical outcomes after intrastromal corneal ring segments reoperation in keratoconus patients

AIM:To evaluate the clinical outcomes after Ferrara intrastromal corneal ring segments (ICRS) reoperation in patients with keratoconus.RESULTS: The mean follow-up time after the reoperation was 30.5±9.7 months. The mean UCVA improved from 20/300 to 20/80 (P=0.005); the mean BCVA improved from 20/160 to 20/50 (P=0.0002), the mean keratometry reduced from 49.33±4.19D to 46.16±3.90D (P=0.0001), the mean pachymetry at the thinnest point increased from 450±42.9mm to 469±40.8mm (P=0.0001). The asphericity increased from -0.84±0.74 to -0.35±0.81 (P=0.15) and the spherical equivalent reduced from -4.64±4.87D to -3.04±3.45D (P=0.137). The changes in the asphericity and spherical equivalent were not statistically significant.CONCLUSION: Ferrara ICRS implantation showed to be a reversible and readjustable surgical procedure for keratoconus treatment. Good outcomes can be obtained even after removal, addition, reposition or exchange of ICRS.     

Intracorneal ring segments in ectatic corneal disease – a review

The purpose of this review is to collect and summarize all the scientific literature regarding the use of intracorneal ring segments (ICRS) in corneal ectatic disease. These implants, initially designed to correct myopia in normal eyes, are implanted in the deep corneal stroma with the aim of achieving modifications to the corneal curvature and subsequently refractive adjustments. Colin et al. in 2000 were the first to report the efficacy of these implants in reducing the refractive error and corneal steepening in keratoconus eyes. Two main types of ICRS have been developed and used for the treatment of ectatic corneal disease, different in profile and diameter of implantation: Intacs and Ferrara rings. Successful outcomes have been reported by several authors with these implants in keratoconic eyes using different nomograms. Besides keratoconus, ICRS have been also used successfully for the management of pellucid marginal degeneration and post‐laser in situ keratomileusis corneal ectasia. The implantation procedure may be performed today by two surgical techniques to create the corneal channels where implants are inserted: mechanical dissection using a manual semicircular dissector (mechanical‐assisted) and photodisruption of lamellar tissue using the femtosecond laser technology (femtosecond‐assisted). With both techniques, visual, refractive and topographic improvements have been observed, although higher incidence of intraoperative and postoperative complications have been reported with the mechanical procedure according to the evidence found in the peer‐reviewed literature. ICRS technology is a promising therapeutic option in corneal ectatic disease, avoiding corneal graft and allowing a visual and refractive rehabilitation.     

Evaluation of intrastromal corneal ring segments for treatment of keratoconus with a mechanical implantation technique

Purpose:

To evaluate the clinical outcomes of intrastromal corneal ring segment (ICRS) implantation in patients with keratoconus using a mechanical implantation technique.

Materials and Methods:

Thirty eyes of 17 patients with keratoconus were enrolled. ICRSs (Keraring) were implanted after dissection of the tunnel using Tunc''s specially designed dissector under suction. A complete ophthalmic examination was performed, including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent, keratometric readings, inferosuperior asymmetry index (ISAI), and ultrasound pachymetry. All 3-, 6-, and 12-month follow-ups were completed, and statistical analysis was performed.

Results:

The mean preoperative UDVA for all eyes was 1.36 ± 0.64 logMAR. At 12 months, the mean UDVA was 0.51 ± 0.28 logMAR (P = 0.001), and the mean preoperative CDVA was 0.57 ± 0.29 logMAR, which improved to 0.23 ± 0.18 (P = 0.001) at 1 year. There was a significant reduction in spherical equivalent refractive error from –6.42 ± 4.69 diopters (D) preoperatively to –1.26 ± 1.45 D (P = 0.001) at 1 year. In the same period, the mean K-readings improved from 49.38 ± 3.72 D to 44.43 ± 3.13 D (P = 0.001), and the mean ISAI improved from 7.92 ± 3.12 to 4.21 ± 1.96 (P = 0.003). No significant changes in mean central corneal thickness were observed postoperatively. There were no major complications during and or after surgery.

Conclusion:

ICRS implantation using a unique mechanical dissection technique is a safe and effective treatment for keratoconus. All parameters improved by the 1-year follow-up.     

Clinical outcomes after implantation of a new intrastromal corneal ring with 140-degree of arc in patients with corneal ectasia

AIM: To evaluate the clinical and tomographic outcomes after implantation of a new intrastromal corneal ring segment (ICRS) with 140-degrees of arc in eyes with corneal ectasia. METHODS: We evaluated patients with corneal ectasia implanted with Ferrara 140° ICRS from April 2010 to February 2015. Outcome measures included preoperative and postoperative corrected distance visual acuity (CDVA), keratometry simulated (K) reading, tomographic astigmatism and asphericity. All patients were evaluated using the Pentacam Scheimpflug system. RESULTS: The study evaluated 58 eyes. The mean follow-up was 16.81±10.8mo. The CDVA (logMAR) improved from 0.5±0.20 (20/60) to 0.3±0.21 (20/40) (P<0.01). The average K reduced from 49.87±7.01 to 47.34±4.90 D (P<0.01). The asphericity changed from -0.60±0.86 to -0.23±0.67 D (P<0.01). The mean preoperative tomographic astigmatism decreased from -8.0±3.45 to -4.53±2.52 D (P<0.01). CONCLUSION: The new ICRS model with 140-degrees of arc effectively improve the visual acuity and reduce the high astigmatism usually found in patients with corneal ectasia.     

Orbscan检查仪筛查临床前期圆锥角膜应用研究

目的比较0rbscan眼前节系统和普通角膜地形图仪筛查早期圆锥角膜的应用价值。方法选择我所拟行准分子激光手术患者1829例3652眼，根据检查方法不同分实验组和对照组，检查前均停止配戴角膜接触镜2周以上。对照组采用TomeⅢ角膜地形仪常态小瞳孔下做角膜地形图；实验组采用美国博士伦公司新款0rbscan眼前节诊断系统，半暗室状态下测定。结果实验组972眼检测出临床前期圆锥角膜19眼，检出率1.95％；对照组2680眼检测出临床前期圆锥角膜18眼，检出率0.67％；2组检出率相比差异有统计学意义（P〈0.05）。结论0rbscan可作为准分子激光屈光手术前筛查的重要检查手段。     

Effect of intracorneal ring segment implantation on corneal asphericity

AIM: To evaluate the visual, refractive and corneal asphericity changes after intrastromal corneal ring segment (ICRS) implantation for visual rehabilitation of keratoconus. METHODS: A total of 42 eyes of 32 patients were included. After creation of intrastromal tunnels of 5.01±0.03 mm inner diameter, 5.71±0.03 mm outer diameter and at 384.21±34.12 μm depth, 1 or 2 ICRS of 150-300 μm thickness and 90°-210° arc length were implanted. Changes in uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refractive errors, mean simulated keratometry readings (SimKavg), anterior and posterior corneal asphericity values (Qant and Qpost, respectively) measured with Scheimpflug topography were evaluated retrospectively. RESULTS: There was a significant improvement in UDVA and CDVA, along with a significant decrease in refractive spherical equivalent (SE), cylinder and SimKavg postoperatively (P<0.001 for all). Mean Qant increased from -1.06±0.48 to -0.57±0.58 postoperatively (P<0.001). Change in mean Qpost was insignificant (P=0.92). Postoperative changes in UDVA and CDVA were not correlated with the postoperative changes in SE and cylinder (P>0.05 for all); but were correlated with the preoperative SimKavg and Qant values (P<0.001 for all). CONCLUSION: ICRS implantation seems to approximate the anterior corneal asphericity of “advanced prolate” shape to “optimal prolate” shape and an “ideal Q value” of -0.46; which may have a role in improved UDVA and CDVA postoperatively, besides decreased refractive cylinder values.     

Clinical effectiveness of intrastromal corneal ring segments among keratoconus patients

AIM: To evaluate the clinical effectiveness of intrastromal corneal ring segments (ICRS) among the patients suffering from keratoconus. METHODS: A retrospective and non-comparative interventional design had been utilized on the basis of postoperative follow-up among 56 keratoconus patients. Visual acuity was significantly assessed during complete ophthalmic examination of the patients. The femtosecond laser had been used to create the corneal tunnels in 15 eyes; whereas, the corneal tunnels were created in 72 eyes mechanically. RESULTS: The ranges and standard deviations had been used to obtain results. It had been revealed through ophthalmic assessment that the mean preoperative uncorrected visual acuity observed was 1.38±0.37 logarithm of Minimal Angle of Resolution. Moreover, a significant improvement was observed postoperatively in visual acuity by 0.58±0.32 during the 4th month. The improvement was also witnessed in the 16th month by 0.48±0.30. CONCLUSION: The implantation of ICRS is an efficient and effective surgical intervention for the treatment of keratoconus. Thus, identified intervention seems to be associated with appropriate visual outcomes and safety after the development of femtosecond as well as mechanical tunnels.     

Orbscan检查仪在准分子激光手术的应用

目的研究Orbscan眼前段系统和普通角膜地形图仪在准分子激光手术前筛查早期圆锥角膜的应用价值。方法选择994例1984眼有做准分子激光手术意向者分观察组和对照组,检查前均停止佩戴角膜接触镜2周以上。对照组:采用TomeⅢ角膜地形仪常态小瞳孔下做角膜地形图。观察组:采用美国博士伦公司新型Orbscan眼前段诊断系统,半暗室状态下测定。结果观察组972眼检出临床前期圆锥角膜19眼,检出率1.95%;对照组1012眼检出临床前期圆锥角膜7眼,检出率0.69%(P<0.05)。结论Orbscan眼前段系统检测是圆锥角膜早期诊断中具有高度敏感性的可靠的定量分析方法,可作为准分子激光屈光手术前筛查的重要检查手段。     

圆锥角膜患者角膜光密度与形态及生物力学的相关性研究

目的:探讨圆锥角膜患者角膜光密度与角膜形态参数及生物力学特性的相关性。方法:回顾性病例研究。收集2020-01/12在郑州市第二人民医院就诊的原发性圆锥角膜患者48例70眼,使用Pentacam眼前段分析系统测量角膜形态,包括角膜前表面中央扁平子午线曲率(K₁)、角膜前表面陡峭子午线曲率(K₂)、角膜前表面中央平均曲率(K_m)、角膜前表面最大曲率(K_max)、角膜前表面高度(ACE)、角膜后表面高度(PCE)、最薄点角膜厚度(TCT),以及圆锥锥顶距角膜顶点的距离(DCA)。测量不同分区不同层次的角膜光密度。使用可视化角膜生物力学测量仪观察角膜形变过程并测量相关参数,包括第一次压平时间(AT₁),第一次压平长度(AL₁),第一次压平速度(V₁),第二次压平时间(AT₂),第二次压平长度(AL₂),第二次压平速度(V₂),最大压陷时间(HCT),最大压陷形变幅度(HCDA...     

近视眼患者角膜直径和角膜曲率的研究

目的探讨近视眼患者角膜直径和角膜曲率的正常值及二者之间的关系。方法对220例(440眼)近视眼患者(年龄17～41岁,男118例236眼,女102例204眼)采用美国Lasersight公司的AstraMax角膜地形图进行角膜前表面摄像,测量3次并获取角膜水平直径(白到白)和角膜前表面平均曲率的平均值,并对这2项参数进行相关的统计学分析。结果本组中角膜直径平均值为(12.00±0.40)mm,男性为(12.12±0.36)mm,女性为(11.86±0.40)mm。角膜曲率平均值为(43.51±1.37)D,男性为(43.10±1.29)D,女性为(43.99±1.31)D。角膜直径和角膜曲率的回归方程为Y=19.060-0.162X(Y代表角膜直径,X代表角膜曲率)。结论男女之间角膜直径存在着统计学差别,男性大于女性;角膜曲率之间亦有统计学意义,女性大于男性。近视眼患者角膜直径和角膜曲率之间存在统计学负相关性,即角膜曲率越高,角膜直径越小。     

Determination of corneal volume from anterior topography and topographic pachymetry: application to healthy and keratoconic eyes

Purpose: To describe a method to measure corneal volume from topography and pachymetry, and test its clinical use on a sample of healthy human subjects and a case of circumscribed posterior keratoconus. Methods: Corneal curvature (PCT 200^® corneal topography system; Optopol Technology SA, Zawiercie, Poland) and ultrasonic topographic pachometry on 25 points (Ophthasonic^® A‐Scan/Pachometer III; Teknar Inc., St Louis, MO, USA) were measured on each of 12 young healthy corneas and one cornea suffering from circumscribed posterior keratoconus. Topography and pachymetry data were used to calculate the coordinates for the corresponding points on the posterior surface of the cornea. TableCurve 3D software (Systat Software Inc., Chicago, IL, USA) was used to fit a surface to those points measured. Integration of the surface fitted to the data points, corresponding to the anterior and posterior corneal surfaces, was used to calculate the volume underneath each of them. Subtraction of volumes underneath anterior and posterior surfaces, taking into account an axial offset equal to the central corneal thickness, rendered corneal volume for the central 6 mm of the cornea. Results: Central corneal thickness ranged from 520 to 630 μm for the healthy corneas. Corneal volumes for this sample analyzed averaged 18.66 ± 1.15 mm³ (range 17.25–20.53 mm³). For the posterior keratoconic cornea, the affected area was located at about 1.5–2 mm from the corneal center on the 135° hemimeridian of the right eye, observed through topographic pachymetry. Calculated corneal volume for the central 6 mm was 16.072 mm³, noticeably lower than those found in the sample without pathology, but within the range for corneas presenting with keratoconus. Conclusions: Corneal volume is a useful parameter for characterising dystrophic corneas and can aid in the detection of rare anomalies which are hardly detected with corneal topography and/or central corneal thickness evaluation. A potentially useful measure of corneal volume can be calculated from anterior corneal topography and topographic pachymetry data. Values obtained are in good agreement with previous studies using corneal tomography techniques. The methodology has been shown to have potential for retrospective analysis of data, or where no access is available to tomographical techniques.     

Mathematical analysis of corneal remodelling after intracorneal ring surgery in keratoconus

AIM: To represent mathematically the intersection between the ectatic corneal geometry and the plane of intracorneal ring implants (ICRS) in order to determine the corneal response to ICRS surgery in keratoconus (KC). Thereafter, to present the concept and early results of a newly derived topography-guided nomogram for ICRS surgery for the treatment of keratectasia. METHODS: The corneal rings plane intersection was modelled to a conic section. Ring effect was the result of: the ring size, position (steep vs flat), location (distance from the geometric centre of the cornea), and the discrepancy between the ring’s curvature and the tunnel’s curvature. Femtosecond laser was used to create the tunnels and the incision sites were chosen according to the nomogram in order to place the thickest ring in the steepest portion of the cornea regardless of the astigmatism axis of refraction. RESULTS: The conic section had a more prolate shape in the steep area of the cornea than in the flat area, depending on the corneal sagittal curvature. Equal ring size had more flattening effect in the steep area than in the flat area. Thick segment should be implanted under the steep portion of the cornea regardless of the cylinder axis of refraction. Single segment in the steep area was sufficient in early and moderate cases of KC. The new nomogram provided more topographic regularity with significant reduction of astigmatism and better improvement in uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA) than the conventional nomogram. CONCLUSION: The newly derived nomogram can produce better results than the conventional nomogram. Moreover, based on this concept, a new nomogram can be integrated into the femtosecond laser software to create topography-guided, customized, elliptical tunnels with modified focal asphericity that allows for customized focal flattening of the irregularly steepened ectatic cornea.     

角膜基质环植入术治疗圆锥角膜的临床疗效

目的：评估角膜基质环植入术治疗圆锥角膜的临床疗效。

方法：这一回顾性对照干预性研究对56例87眼圆锥角膜患者进行手术后随访。所有患者完善眼科检查,评估视力。15眼使用飞秒激光制备角膜隧道。72眼使用机械的方法制备角膜隧道。

结果：所有患者术前裸眼视力1.38±0.37。术后4mo裸眼视力达到0.58±0.32。术后16mo达到0.48±0.30。

结论：角膜基质环植入术是治疗圆锥角膜的有效方法。有效的干预与理想的术后视力相关。飞秒激光角膜隧道制备和机械方法一样安全。     

Computerized corneal topography in a paediatric population with Down syndrome

PURPOSE: To characterize abnormal corneal topographic changes using corneal computerized videokeratography (CVK) in a paediatric population with Down syndrome, and in their parents. METHODS: Prospective, non-randomized clinical trial. Twenty-one children with Down syndrome (mean age 6.9 years) recruited from The Hospital for Sick Children, 18 of their parents, and a paediatric control group of 60 otherwise well children (mean age 9 years), underwent complete ocular examination and CVK using the EyeSys system. Corneal topographic maps were assessed subjectively, and three objective parameters analysed: central corneal power (CP), difference in central corneal power between the two eyes (DCP), and inferior-superior steepening asymmetry (I-S). RESULTS: Corneal curvature in children with Down syndrome was significantly steeper than in the paediatric control population (CP 46.66 vs 42.60 D, P <0.0001), but changes with age paralleled that of the control population. DCP and I-S values were also significantly different from the control population (P <0.0001). 39% of the parents of children with Down syndrome had at least one abnormal parameter. CONCLUSIONS: This study demonstrates that CVK is a useful tool in the ocular assessment of patients with Down syndrome. The findings suggest that this patient population have abnormalities of corneal shape even in the absence of clinical evidence of keratoconus. A greater than expected incidence of abnormal topographic changes was observed in the parents of these patients.     

Comparison of corneal biological parameters between transepithelial and epithelium-off corneal cross-linking in keratoconus

AIM: To evaluate the differences in corneal biological parameters between transepithelial and epithelium-off corneal cross-linking in keratoconus. METHODS: In our prospective clinical trial, 40 patients (60 eyes) with progressive keratoconus were randomized to undergo corneal cross-linking with transepithelial (TE group, n=30) or epithelium-off (EO group, n=30) keratoconus. Examinations comprised topography, corneal biomechanical analysis and specular microscopy at 6mo postoperatively. RESULTS: The keratometer values were not significantly different between the TE and EO corneal cross-linked groups in different periods (each P>0.05). The corneal thickness of the EO group was greater than that of the TE group at 1wk after the operation (each P<0.05). Regarding corneal biomechanical responses, the EO group showed a longer second applanation length than TE group (P=0.003). Regarding the corneal endothelial function, standard deviation of the endothelial cell size, and coefficient of variation in the cell area, the values of EO group were larger than those of TE group at 1wk (P=0.011, 0.026), and the percentage of hexagonal cells in EO group was lower than that in TE group at 1 and 6mo (P=0.018, 0.019). CONCLUSION: Epithelium-off corneal cross-linking may strengthen corneal biomechanics better than TE procedure can. However, the TE procedure with a lower ultraviolet-A irradiation intensity would be safer for corneal endothelial function.     

去上皮快速角膜胶原交联术治疗进展期圆锥角膜

目的：研究去上皮快速角膜胶原交联术(CXL)治疗进展期圆锥角膜的疗效。

方法：回顾性研究。收集2020-04/2021-12就诊于宁夏回族自治区人民医院 宁夏眼科医院行去上皮快速CXL的进展期圆锥角膜患者32例43眼。于术前及术后1、3、6mo行裂隙灯、眼压、裸眼视力、矫正视力、角膜内皮镜、眼前节分析仪Pentacam和可视化角膜生物力学Corvis ST检查,记录手术前后角膜情况、裸眼视力(UCVA)、最佳矫正视力(BCVA)、角膜内皮数、角膜最大曲率(Kmax)、角膜厚度最薄点(TCT)、前后表面K1、K2值、矫正眼内压(bIOP)、第一次压平时间(A1T)、第一次压平长度(A1L)、第一次压平速度(A1V)、第二次压平时间(A2T)、第二次压平长度(A2L)、第二次压平速度(A2V))、最大形变幅度(HCDA)、最大形变曲率半径(HCR)、最大压陷时两峰间距(HCPD)、第1次压平时角膜硬度(SP-A1))值。

结果：术前、术后6mo UCVA(LogMAR)(1.06±0.49、0.78±0.39)和BCVA(LogMAR)(0.48±0.34、0.38±0.29)比较均有差异(P<0.05),角膜内皮细胞比较无差异(2917.39±288.38 vs 2959.19±336.27cells/mm²,P=0.477)。手术前后Kmax、TCT、前表面K1、K2值、后表面K1值比较均有差异(P<0.05),且均在术后1mo升高,术后3mo后恢复至术前水平,而后表面K2值比较无差异。手术前后A1T、HCPD、SP-A1比较差异均有统计学意义(P<0.05),A1L、A1V、A2T、A2L、A2V、HCDA、HCR、bIOP比较无差异(P>0.05)

结论：去上皮快速CXL在术后6mo内能够阻止进展期圆锥角膜进展并且具有一定的安全性。     

AstraMax角膜地形图在准分子激光手术前筛查圆锥角膜的应用价值

目的评价AstraMax角膜地形图在准分子激光手术前筛查圆锥角膜的应用价值。设计病例系列研究。研究对象拟行准分子激光近视矫正手术患者2202例(4382眼),年龄18～45岁,平均(27.0±0.5)岁。方法患者术前行AstraMax角膜地形图检查,以筛选亚临床期圆锥角膜及可疑圆锥角膜。主要指标角膜地形图,角膜中央屈光力、IS值及角膜厚度。结果共筛选出2例(4眼)亚临床期圆锥角膜,占总体的0.09%;发现可疑圆锥角膜5例(8眼),占总体的0.23%。结论AstraMax角膜地形图检查在圆锥角膜的早期诊断中具有简便、快速、准确的优点,是准分子激光术前筛查的重要检查手段。