Safety and efficacy of Intacs in Indian eyes with keratoconus: An initial report

Context

In contact lens-intolerant keratoconus patients, intrastromal placement of Intacs is becoming a promising new modality of treatment.

Aims

To study the safety and efficacy of implantation of microthin corneal inserts (Intacs) in Asian-Indian keratoconus patients.

Settings and Design

Retrospective interventional case series, in the cornea and refractive surgery service, at a tertiary care eye hospital in South India, between May 2006 and July 2007.

Materials and Methods

Intacs (Addition Technology, USA) were successfully implanted by mechanically creating tunnels, in 12 eyes of 12 keratoconus patients, who were contact lens-intolerant. The patients (mean age 25.58 years, nine male and three female) had a minimum follow-up of six months. Five patients had severe keratoconus (mean K > 53 D) and nine had central cones.

Results

All patients improved or retained visual acuity. The uncorrected visual acuity (UCVA) improved from a mean value of 0.06, (SD ± 0.08) to 0.19 postoperatively (SD± 0.15) (P= 0.01). The change in mean best corrected visual acuity (BCVA) was from 0.51, (SD ± 0.24), to 0.69, (SD ±0.00) (P = 0.01) postoperatively. The average central keratometry reading was 52.55 D. The change in mean K from 52.84 to 49.16 and 49.15 at one and six months respectively, was statistically significant. We did not have any major intra- or early postoperative complications. Eight of 12 eyes became contact lens-tolerant post-surgery.

Conclusion

The procedure of Intacs implantation appears to be safe and effective in a small group of Indian population at an intermediate follow-up.     

Decision making nomogram for intrastromal corneal ring segments in keratoconus

Purpose:

To create a nomogram for the insertion of intrastromal corneal ring segments (ICRS) (Intacs^® ) in eyes with keratoconus.

Setting:

Tertiary eye care center in South India.

Materials and Methods:

This prospective, non-randomized, interventional case series used a self-designed decision-making nomogram for the selection of ICRS in keratoconus patients based on the centration of the cone, mean refractive spherical equivalent (MRSE), and mean keratometry (Km) values. The 3, 6, and 12 months clinical outcomes were compared to historical controls. Primary endpoints were improvement in uncorrected and best-corrected vision and change in the keratometric values.

Results:

Group A comprised of 52 eyes of 50 patients that followed the nomogram, while Group B comprised of 25 eyes of 23 non-nomogram historical controls matched for baseline parameters. In Group A, the uncorrected distance visual acuity (UDVA) improved from 0.16 ± 0.15 to 0.25 ± 0.16 (P < 0.001), corrected distance visual acuity (CDVA) from 0.58 ± 0.2 to 0.69 ± 0.21 (P = 0.022), MRSE from -5.41 ± 4.94 to -1.71 ± 2.88 (P < 0.001), Km from 51.77 ± 5.45 to 48.63 ± 4.37 (P < 0.001), and astigmatism reduced from 5.86 ± 2.61 to 4.91 ± 2.72 diopters (P < 0.001).In Group B, improvement in the average MRSE was from -6.44 ± 5.32 to -3.26 ± 2.82 (P < 0.013) and in the average Km from 53.64 ± 5.32 to 50.31 ± 5.02 (P < 0.001). Other parameters did not improve significantly. A statistically significant difference was present in the percentage of patients achieving a good clinical outcome between the two groups (P < 0.001; Chi-square).

Conclusion:

The nomogram provides a means to choose the appropriate ICRS, hence improving the outcome in patients with keratoconus.     

圆锥角膜的治疗方法

圆锥角膜(keratoconus,KC)是一种双侧性、进行性角膜基质变薄、前凸且伴进行性视力下降的病理改变,目前国内尚缺乏对该疾病治疗方法的系统性认识.近年来临床上常见的治疗圆锥角膜的方法包括,硬质角膜接触镜、穿透性角膜移植术、板层/深板层角膜移植术、角膜基质内环植入术和角膜交联术以及各种联合手术等.     

核黄素角膜胶原交联治疗早期轻中度圆锥角膜的研究

目的：核黄素角膜胶原交联早期治疗轻度至中度圆锥角膜的预后。

方法：三级眼科诊疗中心的前瞻性研究。共38例47眼轻至中度圆锥角膜接受核黄素角膜胶原交联治疗的患者纳入本研究。术前数据包括参与眼数,视力,眼压,角膜厚度与角膜地形图。术后数据包括最佳矫正视力,眼压,角膜厚度,角膜地形图和术后并发症。

结果：研究包含年龄16～30岁的患者38例47眼。平均术前视力为0.58±0.40 logMAR,术后随访2a显著提高(0.40±0.27logMAR)(P=0.005)。平均术前角膜曲率为50.5±4.6 D,术后显著降低。随访2a平均角膜曲率为48.2±4.1 D(P=0.011)。术后随访2a眼压(15.1±3.0mmHg)较术前(12.9±2.5 mmHg)显著增加(P=0.035)。术前角膜厚度467.9±38.8 μm,术后随访2a(465.0±39.3 μm)明显降低。所有患者均无并发症出现。

结论：早期使用核黄素角膜胶原交联治疗轻至中度圆锥角膜可获得长期的良好视力,而不必等其发展为进展期。     

Photorefractive keratectomy in mild to moderate keratoconus: Outcomes in over 40-year-old patients

Background:Keratoconus is a contraindication for photorefractive keratectomy (PRK). In the recent decade, some efforts have been made to perform PRK in patients with keratoconus whose corneas are stable naturally or by doing corneal collagen crosslinking. These studies have suggested residual central corneal thickness (CCT) ≥450 μm.Aims:The aim was to evaluate the long-term outcomes of PRK in patients with mild to moderate keratoconus in patients older than 40 with residual CCT ≥ 400 μm.Results:A total of 38 eyes of 21 patients were studied; 20 eyes (52.6%) with a grade I and 18 eyes (47.4%) with grade II keratoconus. The mean uncorrected visual acuity, best corrected visual acuity (BCVA), spherical equivalent, cylindrical power and keratometric readings were significantly improved at the final endpoint compared to preoperation measurements (P < 0.001). Two eyes (5%) lost two lines of BCVA at the final visit. No case of ectasia occurred during the follow-up course.Conclusions:PRK did not induce keratoconus progression in patients older than 40 with a grade I/II keratoconus. Residual CCT ≥ 450 μm seems to be sufficient to prevent the ectasia.     

放射状角膜切开术在轻中度圆锥角膜病例中视觉康复的疗效

目的：探讨放射状角膜切开术在轻中度圆锥角膜治疗中光学和视力康复的效果。
　　方法：回顾性分析应用放射状角膜切开术治疗圆锥角膜的病例22例31眼并进行了至少12 mo的随访。测量并分析术前术后裸眼视力,最佳矫正视力,自动屈光计值,角膜曲率,角膜不规则指数以及并发症。
　　结果：在最后一次随访中,平均裸眼视力( logMAR)由0.86±0.34显著提升至0.30±0.29(P<0.0001),平均最佳矫正视力由0.47±0.21提升至0.17±0.23(P<0.0001)。平均角膜曲率由48.69±3.68 D 降低至44.33±3.09 D ( P<0.0001)。自动屈光计测得平均等效球镜值由-5.61±2.85D显著提升至-2.29±1.95D(P<0.0001)。在整个随访过程中,中央角膜厚度和3mm,5mm区域的角膜不规则指数均无变化。术中和术后没有观察到严重并发症。
　　结论：在本组病例中,放射状角膜切开术是轻中度圆锥角膜视觉康复的有效治疗方法。     

Forward-scattered and backward-scattered light in moderate keratoconus

Introduction

To evaluate the backscattered light, objective scatter index (OSI) and retinal straylight in patients with moderate keratoconus and healthy control subjects.

Methods

A prospective observational study was developed with 33 patients in the moderate-keratoconus group (KC) and 34 in the non-keratoconus group (NKC). Corneal densitometry was obtained using Scheimpflug corneal tomography and measurements were expressed in grayscale units (GSU) over four zones within a 12.00 mm diameter around the corneal apex. A straylight meter was used to determine the amount of intraocular straylight under scotopic conditions, and the straylight parameter (LOG(s)) and test duration were recorded. The Optical Quality Analysis System based on the double-pass technique determined the OSI value.

Results

Significant differences were observed between the KC and NKC groups for corneal densitometry (except in the 6–10 mm zone), OSI and retinal straylight. A moderate and significant correlation was found between OSI and retinal straylight LOG(s) (r = 0.52, p = 0.002). Weaker and non-significant correlations were found between corneal densitometry and the other parameters analysed (i.e., OSI, retinal straylight LOG(s) and retinal straylight times).

Conclusions

Backscattered light, retinal straylight and the OSI show clear differences between healthy eyes and those with moderate KC. The changes present in the stages of KC evaluated in the current study (stages II and III according to the Amsler–Krumeich classification) might alter the scattering of the light entering the eye.     

Pentacam眼前节分析仪对散光患者中圆锥角膜和亚临床圆锥角膜的临床研究

目的:Pentacam眼前节分析仪对＞2.0D散光眼患者圆锥角膜和亚临床圆锥角膜的研究.方法:本研究收集散光≥2.0D患者107例201眼.所有的患者进行验光、视力、矫正视力、裂隙灯、眼底镜、传统角膜地形图、Pentacam眼前节分析仪检查.观察包括K1:3mm直径范围水平中央曲率,K2:3mm直径范围垂直中央曲率、角膜前表面最大屈光力(Kmax)、角膜散光(CYL)、角膜最薄处的厚度(MinPachy)、表面变异指数(ISV)、垂直不对称指数(IVA)、圆锥角膜指数(KI)、角膜前表面高度(AE)、角膜后表面高度(PE)等指标变化.并作ROC曲线,对比各组的cutoff值及其敏感指标.Pentacam获得的几个参数分析采用Mann-Whitney U检验.通过ROC曲线分析确定出最佳诊断界点.结果:本研究人群的平均年龄为25.7±6.6岁.前表面Kmax、IVA、KI、AE、PE临床和亚临床组明显高于散光组,角膜最薄处厚度临床和亚临床组明显低于散光组(P＜0.05).Pentacam诊断临床期圆锥角膜的敏感指标(曲线下面积AUC≥0.9),分别为AE、PE、IVA、ISV、KI、Kmax.诊断亚临床圆锥角膜的敏感指标(曲线下面积AUC≥0.9)为PE.结论:研究表明,2D以上散光的人群即使视力正常,也应该进行角膜地形图筛查.Pentacam眼前节分析仪可以提供精准的角膜前后表面解剖信息,尤其是角膜后表面高度测定,对亚临床期圆锥角膜的筛查起重要作用.     

Biomechanical diagnosis of keratoconus: evaluation of the keratoconus match index and the keratoconus match probability

Purpose:  To evaluate the diagnostic capacity of the Ocular Response Analyser’s keratoconus match index (KMI) and keratoconus match probability (KMP) classification in a sample of keratoconus (KC) patients. Methods: Keratoconus match index and KMP from 114 KC eyes, randomly selected from 114 patients with bilateral keratoconus (KCG), were compared with the corresponding ones from 109 normal eyes (CG). Keratoconus match index’s predictive accuracy was assessed by receiver operating curves (ROC). Keratoconus match probability level of agreement was evaluated at the different KC stages of the Amsler–Krumeich classification. Correlations were estimated with topographic keratoconus classification (TKC), keratoconus index (KI), index of surface variance (ISV), vertical asymmetry (IVA), height asymmetry (IHA), height decentration (IHD), minimal radius (Rmin), central corneal thickness (CCT), thinnest corneal thickness (TCT) mean keratometry (Km) and intraocular pressure (IOPg). Results: Mean KMI in KCG and CG was 0.20 ± 0.38 and 0.98 ± 0.25, respectively (p < 0.01). Significant KMI differences (p < 0.01) were detected in different KC groups [range: 0.62 ± 0.38 (KC 1), ?0.62 ± 0.04 (KC 4)]. Significant correlation was detected between KC staging and KMI (r = ?0.56, p < 0.0001). Keratoconus match probability identified 22.03% of the CG eyes as suspect. Moreover, KMP identified 7.01% and 23.68% of the KCG eyes as normal and suspect, respectively. Receiver operating curves analysis for KMI parameter indicated a predictive accuracy of 97.7% (cut‐off point: 0.512, sensitivity: 91.18%, specificity: 94.34%). Conclusions: Keratoconus match index seems to be a reliable index in keratoconus diagnosis and staging. Keratoconus match probability identifies a significant percentage of topographically defined KC and CG eyes as suspect. Diagnostic capacity of these novel indexes needs to be further explored.     

圆锥角膜的诊断

圆锥角膜是一种常见的角膜扩张性疾病 ,在屈光手术就诊者中发病率尤高 ,是许多屈光手术的禁忌证。及早发现圆锥角膜 ,是进行有效防治的基础 ,现就目前圆锥角膜的诊断方法进行了简要论述。     

Treatment of mild to moderate keratoconus with laser in situ keratomileusis

PURPOSE: To evaluate the effectiveness, stability, and complications of laser in situ keratomileusis (LASIK) to treat myopic astigmatism in patients with keratoconus. SETTING: Buzard Eye Institute, Las Vegas, Nevada, USA. METHODS: This study included 16 eyes of 9 patients who had keratometric and/or clinical evidence of keratoconus. Mean age was 45 years, and refraction was stable for at least 2 years. Two treatment approaches were evaluated. RESULTS: Mean preoperative spherical equivalent was -4.23 diopters (D) +/- 2.14 (SD) with a mean steep keratometry of 46.81 +/- 3.07 D. Mean preoperative keratometric cylinder was 3.08 +/- 2.22 D. Mean postoperative keratometric cylinder was 3.00 +/- 4.78 D and mean spherical equivalent, -0.44 +/- 0.86 D. Mean postoperative steep keratometry was 44.12 +/- 7.17 D. Two eyes lost 1 line of best corrected visual acuity (BCVA), 1 eye lost 3 lines, and 2 lost 4 lines. Penetrating keratoplasty (PKP) was scheduled in 3 eyes 1 to 2 years after the primary LASIK. CONCLUSION: The initial visual results appear promising; but longer term results revealed regression of the refractive outcome in some cases. Moreover, despite improvement in the postoperative spherical equivalent and uncorrected visual acuity in most cases, the risk of loss of BCVA and the necessity of performing PKP in 3 cases lead us not to consider LASIK as a primary solution for keratoconus.     

Epidemiology of keratoconus

Prevalence of keratoconus is variable in different parts of the world. Environmental and ethnic factors and the cohort of patients selected for such studies may explain the wide variation in the reported rates. Family history, gender differences, asymmetry in the two eyes, association with ocular rubbing, and natural history of disease are discussed.     

Association of keratoconus with granular corneal dystrophy

A 2-year-old woman presented with a history of reduced vision and foreign body sensation in both her eyes. Ocular examination revealed the simultaneous presence of bilateral keratoconus and granular corneal dystrophy. To our knowledge, bilateral concurrent occurrence of keratoconus and typical granular corneal dystrophy has not been reported previously. In such a case, penetrating keratoplasty performed for keratoconus may also carry the risk of recurrence of the granular dystrophy.     

非角膜地形图引导PRK联合角膜胶原交联术治疗圆锥角膜

目的：评估非角膜地形图引导圆锥角膜患者行光折变角膜切除术(PRK)和角膜胶原交联术(CXL)的视力、屈光度和临床疗效。

方法：术后1mo, 3mo, 6mo and 12mo对34例患者未矫正视力(UDVA)和矫正距离视力(CDVA),平、陡角膜测量读数以及并发症进行评估。

结果：共34例患者平均年龄为23.3±4.0岁。UDVA和CDVA显著提高,且术后1a恢复平稳。通过超过1a的定期随访,T检验显示术前术后值有显著不同(P<0.05)包括视力,球面和柱面变化。Fourier术后图像分析显示轴向位移垂直于术前轴。

结论：非角膜地形图引导PRK联合CXL对于治疗圆锥角膜是一种安全有效的手术选择,能够提高UDVA,CDVA和屈光状态。术后3mo达到稳定状态,与非角膜地形图引导PRK相比,地形图引导的唯一优势可能是通过Fourier术后分析,在某些患者中,球镜和柱镜轴位漂移。     

Clinical detection of unilateral keratoconus

Purpose: To determine the incidence of true unilateral keratoconus on the basis of computerised corneal topography in a group with clinically diagnosed unilateral keratoconus.
Methods: Retrospective review of 295 patients with keratoconus identified 51 patients with a provisional diagnosis of unilateral keratoconus. Thirty-one of these patients were re-examined clinically and 21 patients met the criteria for a clinical diagnosis of unilateral keratoconus. Computerised corneal topographic analysis (Tomey TMS) was then performed.
Results: In a group of 21 patients with clinically diagnosed unilateral keratoconus, computerised corneal topographic analysis identified 14 (67%) patients with bilateral keratoconus and seven (33%) patients with true unilateral keratoconus. Contact lens wear had no significant influence ( P = 0.76) on the topographical diagnosis of keratoconus in the clinically unaffected fellow eye. The estimated incidence of true unilateral keratoconus in the cohort of 295 patients was 4%.
Conclusion: Computerised corneal topography improves sensitivity in detection of true unilateral keratoconus.     

Scanning-slit topography in patients with keratoconus

AIM: To evaluate the anterior and posterior corneal surfaces using scanning-slit topography and to determine the diagnostic ability of the measured corneal parameters in keratoconus. METHODS: Orbscan II measurements were taken in 39 keratoconic corneas previously diagnosed by corneal topography and in 39 healthy eyes. The central minimum, maximum, and astigmatic simulated keratometry (K) and anterior axial power values were determined. Spherical and cylindrical mean power diopters were obtained at the central and at the steepest point of the cornea both on anterior and on posterior mean power maps. Pachymetry evaluations were taken at the center and paracentrally in the 3 mm zone from the center at a location of every 45 degrees. Receiver operating characteristic (ROC) analysis was used to determine the best cut-off values and to evaluate the utility of the measured parameters in identifying patients with keratoconus. RESULTS: The minimum, maximum and astigmatic simulated K readings were 44.80±3.06 D, 47.17±3.67 D and 2.42±1.84 D respectively in keratoconus patients and these values differed significantly (P<0.0001 for all comparisons) from healthy subjects. For all pachymetry measurements and for anterior and posterior mean power values significant differences were found between the two groups. Moreover, anterior central cylindrical power had the best discrimination ability (area under the ROC curve=0.948). CONCLUSION: The results suggest that scanning-slit topography and pachymetry are accurate methods both for keratoconus screening and for confirmation of the diagnosis.     

In-vivo corneal biomechanical analysis of unilateral keratoconus

AIM: To evaluate and compare corneal biomechanical findings measured by ocular response analyzer, topographic and pachymetric findings in patients with unilateral keratoconus patients and healthy controls. METHODS: This is an observational, case-control study. Patients with keratoconus in one eye and forme fruste keratoconus in the fellow eye were compared with sex and age matched with controls healthy subjects. All subjects were evaluated with rotating scheimpflug imaging system. The receiver-operating-characteristic curves were analyzed to evaluate the sensitivity and specificity of the parameters. RESULTS: Twenty-seven patients with keratoconus in one eye and forme fruste keratoconus in the fellow eye were compared with 40 eyes of 40 normal subjects. Corneal hysteresis (CH) was 8.0±1.7 mm Hg in keratoconus group, 8.3±1.6 mm Hg in forme fruste keratoconus group, and 9.8±1.6 mm Hg in control groups (P=0.54 between keratoconus and forme fruste keratoconus groups, P<0.01 between control group and other groups). Corneal resistance factor (CRF) was 7.1±2.2 mm Hg in keratoconus group, 7.8±1.2 mm Hg in forme fruste keratoconus group and 9.9±1.5 mm Hg in control group (P<0.001 between control group and other groups). Using receiver-operating-characteristic analysis, the area under curve values of the parameters to distinguish forme fruste keratoconus from control subjects were: CH (0.768), CRF (0.866). Best cut-off points were 9.3 mm Hg and 8.8 mm Hg for CH and CRF respectively. CONCLUSION: Ocular response analyzer parameters (CH and CRF) are found to be significantly lower in forme fruste keratoconus patients compared to normal control subjects.