Optical coherence tomography to assess intrastromal corneal ring segment depth in keratoconic eyes

PURPOSE: To investigate intrastromal corneal ring segment depth with a high-speed corneal optical coherence tomography (OCT) system. SETTING: Doheny Eye Institute, University of Southern California, Los Angeles, California, USA. METHODS: A prospective observational case series comprised 4 eyes of 4 patients receiving Intacs intrastromal corneal ring segments (Addition Technology, Inc.) for keratoconus. Optical coherence tomography (OCT) was performed between 7 days and 43 days after implantation. RESULTS: The slitlamp impression of intrastromal corneal ring segment implantation depth did not correlate well with OCT measurements (r(2) = 0.68). The fractional implantation depth was correlated with several surgical variables using a stepwise multivariate regression model, and 2 statistically significant correlations were found. The position of the distal portions of the ring segments was shallower than that of the portion closer to the insertion site (P = .003). Segments placed in the inferior cornea (P = .008) experienced more distal shallowing. Shallower depth was associated with greater fractional anterior stromal compression (P = .04). CONCLUSIONS: Shallower placement of intrastromal corneal ring segments may result in more complications, such as epithelial-stromal breakdown and extrusion, because of the greater anterior stromal tensile strain. The distal and inferior portions of intrastromal corneal ring segments tended to be placed at a shallower depth. Optical coherence tomography provided precise measurement of ring segment depth and may help identify implants that pose a greater risk for depth-related complications.     

Intraocular pressure measurement in patients with instrastromal corneal ring segments.

PURPOSE: To study the measurement of intraocular pressure after implantation of Intacs (ICRS) intrastromal corneal ring segment, a device that is positioned circumferentially in the peripheral corneal stroma to correct myopia. The device changes the corneal curvature by shortening arc length. Since the ring segments are made of polymethylmethacrylate, this may cause localized changes in corneal elasticity so intraocular pressure measurement may be affected. METHODS: We measured the intraocular pressure of 12 eyes in which the ICRS had been in place longer than 6 months. We used Goldmann applanation and Tono-Pen tonometers over the central corneal and the paracentral corneal areas. We also measured the intraocular pressure with the Tono-Pen applanated directly over the intrastromal corneal ring segments. RESULTS: The resulting intraocular pressure measurements were similar for the Tono-Pen tonometer readings over the central cornea, paracentral cornea, and the Goldmann applanation tonometer readings over the central cornea (P < .01). Our measurements using the Goldmann applanation tonometer on the paracentral corneal area showed artificially elevated intraocular pressure in the 40 to 60 mmHg range. We were not able to obtain consistent results when we measured the intraocular pressure using the Tono-Pen on the corneal area directly overlying the intrastromal corneal ring segment implants. CONCLUSION: Consistent intraocular pressure measurements on eyes with the ICRS can be obtained with the Goldmann applanation tonometer over the central corneal area or with the Tono-Pen tonometer over the central or paracentral corneal areas.     

Intrastromal corneal ring segments in a patient with previous laser in situ keratomileusis

PURPOSE: Intrastromal corneal ring segments (ICRS; Intacs) were inserted in a patient with residual myopia of -3.375 D (spherical equivalent) 10 months after laser in situ keratomileusis (LASIK). METHODS: A standard intrastromal corneal ring segment implantation technique was used with the addition of intraoperative ultrasonic pachymetry in 4 quadrants at the 7-mm zone to insure adequate stromal thickness for segment insertion. RESULTS: Four months after ICRS surgery and 14 months after LASIK, the patient had uncorrected visual acuity of 20/20 and a cycloplegic refraction of plano -1.00 x 23 degrees. CONCLUSION: Implantation of intrastromal corneal ring segments in an eye with previous LASIK resulted in additional corneal flattening with a decrease in residual myopia and improved uncorrected visual acuity.     

Optical coherence tomography imaging in keratoconus

Optical coherence tomography (OCT) is being increasingly used as a tool in the diagnosis and management of keratoconus. While elevation‐based topography remains essential, there is an expanding role for cross‐sectional OCT imaging in the diagnosis of the disease. Images and measurements of corneal thickness, and in particular, epithelial thickness, may be important in diagnosing early cases, and following procedures such as intrastromal corneal ring segments, corneal transplants and corneal collagen cross‐linking.     

Evaluation of granular corneal dystrophy with optical coherent tomography

OBJECTIVE: To determine the intrastromal layer of corneal deposits in granular corneal dystrophy (GCD). DESIGN: Investigative case report. METHODS: A 32-year-old woman with bilateral decreased vision because of corneal deposits was examined with cross-sectional scans using optical coherence tomography (OCT). RESULTS: Visual acuity was 20/100 OU. Multiple confluent gray-white patches with an irregular shape were seen in the corneal stroma, leading to a diffuse opacification. OCT disclosed multiple hyperreflective dots in the anterior and deeper stromal layers. CONCLUSION: When severe corneal opacities obscure the clinical differentiation between anterior and deep infiltrates, OCT may determine the layers of the accumulation and select an appropriate surgical procedure.     

Imaging scleral expansion bands for presbyopia with optical coherence tomography

A 57-year-old woman was treated for mild presbyopia with implantation of scleral expansion bands (SEB). Although near vision was temporarily restored, the effect dissipated after 1 year. Slitlamp-adapted optical coherence tomography (OCT) at 1310 nm allowed precise cross-sectional visualization of the hyporeflective intrascleral segments. The OCT method provided precise images of the segment depth and thickness, the scleral thickness at the scleral spur, the anterior chamber angle, and the angle-opening distance. Intrascleral tilting of 1 segment was seen; this required removal of the SEB because of marked foreign-body sensation. Noncontact, slitlamp-adapted OCT can be used to evaluate scleral changes after SEB implantation.     

Corneal optical coherence tomography before and immediately after excimer laser photorefractive keratectomy

PURPOSE: To investigate the representation of the corneal structure with optical coherence tomography before and immediately after excimer laser photorefractive keratectomy. METHODS: Twenty-four eyes of 24 patients with myopia and myopic astigmatism were prospectively studied. The corneal thickness and the corneal profile were assessed with slit-lamp-adapted optical coherence tomography preoperatively and immediately after excimer laser photorefractive keratectomy. RESULTS: The attempted mean spherical equivalent of the refractive corrections was -6.7 +/- 3.6 (mean +/- SD) diopters with a mean calculated stromal ablation depth of 91 +/- 38 microm. The corneal optical coherence tomography was reproducible in all patients, demonstrating a mean decrease of central corneal thickness after epithelial debridement and excimer laser photorefractive keratectomy of 118 +/- 45 microm. The comparison of the calculated stromal ablation depth and the corneal thickness changes determined by corneal optical coherence tomography revealed a significant linear relationship with a correlation coefficient of 0.88 (P <.001). The flattening of the corneal curvature was confirmed in all patients with the optical coherence tomography system and correlated with the attempted refractive correction (r =.82, P <.001). CONCLUSIONS: The slit-lamp-adapted optical coherence tomography system presented in this study allowed noncontact, cross-sectional, and high-resolution imaging of the corneal configuration. This initial clinical evaluation demonstrated that corneal optical coherence tomography could be a promising diagnostic modality to monitor corneal changes of thickness and curvature before and after excimer laser photorefractive keratectomy.     

Imaging and quantification of calcified corneal lesions with optical coherence tomography

PURPOSE: The purpose of this study was to image and quantify calcified corneal lesions with optical coherence tomography (OCT) and to evaluate this diagnostic method to assess this corneal disease. METHODS: In a clinical study 15 eyes of 14 patients with calcified corneal lesions in the anterior portions of the cornea were assessed with slit-lamp biomicroscopy and slit-lamp-adapted OCT. The qualitative and quantitative optical changes were compared with the clinical findings. RESULTS: In corneal OCT all calcified lesions revealed marked hyperreflective changes that correlated well with macroscopic findings. Dense calcified lesions resulted in partial or complete shadowing of the posterior corneal structures. The thickness values for the hyperreflective calcified lesions ranged from 27 to 344 microm. CONCLUSION: Noncontact slit-lamp-adapted OCT may be of value in assessing calcified corneal lesions. Corneal OCT could also be used to precisely measure the depth of these corneal processes and evaluate treatment modalities.     

Identification and localization of multiple intrastromal foreign bodies with anterior segment optical coherence tomography and ocular Pentacam

To report the clinical aspects and the imaging of a patient with intrastromal glass foreign bodies after a road traffic accident using both anterior segment optical coherence tomography (OCT) and ocular Pentacam. A detailed case report was made of the use of anterior segment OCT (AS-OCT) and ocular Pentacam to evaluate intrastromal foreign bodies. AS-OCT and Pentacam were valuable non-invasive tools in identification, localization and monitoring patients with intrastromal foreign bodies. This report demonstrates that AS-OCT and ocular Pentacam are effective and necessary procedures for both the diagnosis and follow-up of intracorneal foreign bodies.     

Management of corneal ectasia after laser in situ keratomileusis with INTACS

PURPOSE: To evaluate the safety and efficacy of intrastromal corneal ring segments (ICRS, INTACS, Keravision) for the correction of corneal ectasia after laser in situ keratomileusis (LASIK). METHODS: In this prospective, noncomparative case series, INTACS were implanted in three eyes (two patients) that were ectatic after LASIK. Mean follow-up was 8.7 months (range, 8 to 10 mo). RESULTS: No intraoperative complications occurred. After INTACS implantation, uncorrected visual acuity ranged from 20/20 to 20/25 at 6 months and remained stable until 9 months. Mean postoperative spherical equivalent refraction was 0.50 D at 1 month and no significant changes appeared up to 9 months after INTACS implantation. After INTACS implantation, no eye lost any lines of Snellen spectacle-corrected visual acuity and two eyes gained from one to two lines. There was an increase in topographical regularity in all three eyes. CONCLUSION: Implantation of INTACS in eyes with corneal ectasia after LASIK resulted in good refractive outcome, absence of complications, and improvement in visual acuity.     

Recent advances in ophthalmic anterior segment imaging: a new era for ophthalmic diagnosis?

Anterior segment imaging is a rapidly advancing field of ophthalmology. New imaging modalities, such as rotating Scheimpflug imaging (Pentacam-Scheimpflug) and anterior segment optical coherence tomography (Visante OCT and Slit-Lamp OCT), have recently become commercially available. These new modalities supplement the more established imaging devices of Orbscan scanning slit topography and ultrasound biomicroscopy (UBM). All devices promise quantitative information and qualitative imaging of the cornea and anterior chamber. They provide a quantitative angle estimation by calculating the angle between the iris surface and the posterior corneal surface. Direct angle visualisation is possible with the OCT devices and UBM; they provide images of the scleral spur, ciliary body, ciliary sulcus and even canal of Schlemm in some eyes. Pentacam-Scheimpflug can measure net corneal power, a feature particularly useful for cataract patients having undergone previous corneal surgery. Anterior segment OCT can measure corneal flap depth following LASIK and anterior chamber width prior to phakic intraocular lens implantation. The arrival of the new imaging devices may herald the dawn of a new era for ophthalmic diagnosis, particularly in view of the ease and non-contact nature of examination.     

Photorefractive keratectomy after intrastromal corneal ring segment explantation

PURPOSE: To describe a case of photorefractive keratectomy after removal of intrastromal corneal ring segments from the cornea. METHODS: During United States Food and Drug Administration Phase III Trials for intrastromal corneal ring segments (ICRS), the implanted segments were removed from the cornea of the right eye of a patient because of dissatisfaction with glare, halos, and fluctuating vision. Ten months after ICRS explantation, the-patient underwent a photorefractive keratectomy procedure to the same eye. RESULTS: One month after removal of the ICRS, the patient's manifest refraction was within +/- 0.50 diopters of his original manifest refraction. Photorefractive keratectomy was planned to the same eye 6 months later. At the first attempt, the epithelium could not be removed with the laser and scrape technique, and residual epithelium was noted at the vertical meridian (12 o'clock) corneal incision site, which had been used for ICRS surgery and explant; therefore, the procedure was aborted. At the second attempt, with a mechanical epithelial brush (AMOILS Epithelial Scrubber; Innova, Inc, Toronto, Canada), the epithelium was removed with ease. After this, photorefractive keratectomy was done without difficulty or complication. At his most recent 8-month postphotorefractive keratectomy examination, the patient had an uncorrected visual acuity of RE: 20/16, with a manifest refraction of -0.75 to 0.75 x 170 degrees, a faint haze at the site of the stromal channel, and a small scar at the incision site on slit-lamp examination. CONCLUSIONS: Intrastromal corneal ring segments can be readily removed from the cornea, if required. In this case, the refraction returned to its preoperative state soon after the explant procedure and remained stable over time. Photorefractive keratectomy was performed as a secondary refractive surgical procedure after the removal of ICRS without difficulty or complication. However, removal of the epithelium is probably best accomplished with the use of an epithelial brush, considering the changes in the epithelial adherence in a postsurgical cornea. Further studies are required to establish the safety and efficacy of secondary refractive surgical procedures after ICRS explantation.     

Untersuchungen der Hornhaut mittels optischer Kohärenztomographie

Introduction. This study evaluated the clinical use of optical coherence tomography (OCT) for two-dimensional representation of the cornea. Patients and methods. Noncontact slitlamp-adapted OCT was used in selected cases to evaluate pathologically altered corneas and to measure the central corneal thickness and curvature. Results. OCT provided correlation between differences in reflection and morphological changes. Scar tissue resulted in hyperreflective light scattering, wheras cystic lesions were hyporeflective. Precise biomorphometry also allowed representation of intrastromal and retrocorneal changes. Central corneal thickness measured by OCT yielded reproducible values and corneal curvature could be calculated from the optical signals of the corneal surface. Conclusions. OCT provides high-resolution representation of the cornea and exact evaluation of its morphology, thickness, and curvature. Due to the noncontact, simple, and rapid examination using the slitlamp the corneal OCT method is a promising additional diagnostic modality.     

Evaluation of anterior and posterior surfaces of the cornea using a dual Scheimpflug analyzer in keratoconus patients implanted with intrastromal corneal ring segments

AIM: To evaluate corneal parameters measured with a dual Scheimpflug analyzer in keratoconus patients implanted with intrastromal corneal ring segments (ICRS). METHODS: Fifty eyes of 40 keratoconus patients had Ferrara ICRS implantation from November 2010 to April 2014. Uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), refraction, keratometry, asphericity, elevation, pachymetry, root mean square (RMS), spherical aberration and coma were studied. All patients were evaluated using a dual Scheimpflug system. RESULTS: The mean follow-up time after the procedure was 12.7mo. The mean UCVA improved from 0.82 to 0.31 (P<0.001); the mean BCVA improved from 0.42 to 0.05 (P<0.0001), the mean spherical refraction changed from -3.06±3.80 D to -0.80±2.5 D (P<0.0001) and the mean refraction astigmatism reduced from -4.51±2.08 D to -2.26±1.18 D (P<0.0001). The changes from preoperative to postoperative, in parameters of the anterior and posterior surface of the cornea, were statistically significant except the elevation posterior at the apex of the cornea and posterior asphericity. CONCLUSION: The implantation of Ferrara ICRS induces changes in both anterior and posterior surfaces of the cornea.     

Optical coherence tomography for evaluation of anatomical changes in the cornea after laser in situ keratomileusis

PURPOSE: To examine the use of optical coherence tomography (OCT) in evaluating anatomical changes after laser in situ keratomileusis (LASIK) and complications related to the interface and corneal flap. SETTING: Istanbul University Eye Research Center and Department of Ophthalmology, Cerrahpasa Medical School, Istanbul, Turkey. METHODS: Eleven eyes of 11 patients who had myopic LASIK were included in the study. Mean age of the 7 men and 4 women was 29.4 years +/- 6.9 (SD). Cases analyzed included uneventful LASIK (4 eyes), epithelial ingrowth (5 eyes), and flap striae (2 eyes). Corneas were examined by OCT (Humphrey Systems). RESULTS: Optical coherence tomography resolved corneal flap and residual stromal layers in all cases. The mean thickness of the corneal flap and residual stroma was 138.2 +/- 16.5 microm and 321.7 +/- 32.1 microm, respectively. Interface between the corneal flap and residual stroma was shown by OCT. Optical coherence tomography revealed that the eye with flap striae had flap displacement undetected by biomicroscopy. Epithelial ingrowth was shown as a highly reflective area. CONCLUSION: Optical coherence tomography appears to be a promising method for evaluating anatomical changes in the cornea after LASIK.     

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.     

Aspergillus fumigatus keratitis following intracorneal ring segment implantation

ABSTRACT: BACKGROUND: Fungal keratitis has been rarely reported following intracorneal ring segment (ICRS) inmplantation. This paper aims to report a case of fungal keratitis with aspergillus fumigatus following ICRS implantation for correction of keratoconus. METHODS: A retrospective chart review was done. Data including demographics, clinical history and presentation, microbiological analysis as well as clinical management were recorded. RESULTS: A 34 year old male presented with pain, photophobia, redness and decreased vision in his right eye ten days after ICRS implantation for correction of keratoconus. Slit-lamp examination showed chemosis, ciliary injection, corneal abcess with ill defined edges and hypopyon. Microbiological analysis and culture of the corneal scrapes were positive for aspergillus fumigatus. The patient did not respond to medical treatment and ended up with corneal transplantation. CONCLUSION: Although rare, fungal keratitis is a serious vision threatening complication that can complicate intrastromal ring implantation. Prompt and aggressive treatment is essential to prevent irreversible reduction of vision.     

Intracorneal ring segments for correction of myopia. Results of microsurgery technique

Background and objective. Since May 1998, small incision instruments for the implantation of intrastromal corneal ring segments (ICRS) are available enabling incisions only 1.2 mm in width instead of 1.8 mm to be made. After a follow-up period of 22 months in the conventional group and 8 months in the small incision group, the results of both groups were compared. Patients and methods. Since April 1997, 73 intrastromal corneal ring segments have been implanted, the first 43 ICRS implantations in 29 patients were performed using the conventional technique, the next 30 ICRS implantations in 22 patients were performed with the small incision technique. The average preoperative myopia was ?3.5 D. Results. After 6 months, 66.7% of the patients of both groups achieved the refraction target ±0.5 D. Even on the first postoperative day, the final refraction is achieved and shows stability for 1 year without regression. After 6 months, 80% of the conventionally operated patients and 77.8% of the patients operated on with the small incision technique showed an uncorrected visual acuity of 1.0 or better. With the small incision technique the preparation of the corneal dissection channel in 2/3 corneal stromal depth is significantly easier and can be carried out more safely.. Perforations towards the inner or outer surface of the cornea can be practically excluded. Due to the smaller superficial wound in contrast to the conventional technique, a corneal suture is not necessary. Stromal depth of implantation was more than 50% and in both groups no decentration of 1.0 mm or more occurred. Conclusions. The small incision technique increases the intraoperative safety in the dissection of the stromal lamellae in the correct level. Both techniques are comparable with regards to visual acuity and refraction. The smaller corneal wound does not need a corneal suture. Because of these advantages we have completely switched our technique to the small incisions.     

Continuous monitoring of corneal thickness changes during LASIK with online optical coherence pachymetry

PURPOSE: To assess the continuous intraoperative monitoring of central corneal thickness (CCT) changes during laser in situ keratomileusis (LASIK) using online optical coherence pachymetry (OCP). SETTING: Department of Ophthalmology, Vivantes Klinikum Neukolln, Berlin, Germany. METHODS: In this prospective nonrandomized comparative clinical case series of consecutive patients, 32 eyes having LASIK for myopia, myopic astigmatism, or hyperopia were continuously monitored intraoperatively in real time with online OCP integrated into a clinical excimer laser. The intraoperative values were compared to the postoperative flap and residual stromal thicknesses measured with corneal optical coherence tomography (OCT) as well as the calculated myopic ablation depth. RESULTS: Continuous monitoring with online OCP enabled intraoperative visualization of the CCT changes during LASIK. The CCT, flap thickness after the microkeratome pass, time-resolved ablation, and residual stromal thickness were assessed. Intraoperatively, the mean flap thickness was 135 microm +/- 38 (SD) and the mean residual stromal thickness, 286 +/- 59 microm. The mean intraoperative flap and residual stromal thickness values were 43.7 microm and 15.4 microm lower, respectively, than the postoperative values assessed with corneal OCT (P<.001 and P=.005, respectively). The optically determined myopic ablation depth was 118 +/- 37 microm, which was 28 microm higher than the nominal ablation depth. There was a significant correlation (P<.001) between the postoperative flap (r=0.79) and residual (r=0.88) thickness measured with corneal OCT as well as the calculated myopic ablation depth (r=0.95). CONCLUSIONS: Intraoperative online OCP could be an important safety feature to monitor the flap and residual stromal thicknesses during LASIK. The individual ablation depth and possible dehydration effects were also monitored continuously.     

虹膜夹型人工晶状体矫正高度近视的前节OCT检查分析

目的:使用前节OCT分析高度近视植入虹膜夹型人工晶状体后眼内的结构变化。方法:植入前房晶状体矫正高度近视6眼(11.5D至22.0D),使用前节OCT采集前节图像测量术前前房深度,术后人工晶状体与角膜内皮间距离(内皮—晶状体距离),人工晶状体与正常晶状体间距离。结果:术前前房深度为3.27～3.91mm,术后内皮—晶状体距离为2.07～2.24mm。人工晶状体后表面与正常晶状体间的距离为0.82～1.32mm。图像显示虹膜色素层没有明显改变。结论:前房深度较术前减少36.1%～44.6%。前节OCT对于检测虹膜夹型前房晶状体的位置有帮助。