Cataract Surgery Destabilises Temporary the Tear Film of the Ocular Surface. / Kataraktchirurgie destabilisiert vorübergehend die Benetzung der Augenoberfläche.

BACKGROUND: Symptoms due to dry eye in the form of keratoconjunctivitis sicca (KCS) are often seen after cataract surgery. We investigated the influence of cataract surgery on tear film stability on the ocular surface. MATERIAL AND METHODS: 60 eyes of 60 patients who underwent cataract surgery were included in a prospective study in 2017 at the Eye Hospital in Hanoi (Vietnam National Institute of Ophthalmology). The mean age of the patients was 65 ± 10 years. The phacoemulsification was performed under topical anaesthesia by a clear corneal incision and implantation of a foldable IOL. The parameters for the evaluation of the change of the tear film included subjective patient data using the Ocular Surface Disease Index questionnaire (OSDI), findings of the Schirmer I test, the tear break-up time (TBUT) as well as the tear meniscus height (TMH) measured noninvasively with the Keratograph 5M (Oculus). In addition, conjunctival and corneal changes were examined after vital staining with fluorescein for the cornea and rose bengal for the conjunctiva. Data were collected preoperatively, at 1 week, 1 month and 3 months postoperatively. According to DEWS, the disease is classified into 4 groups: mild, moderate, severe and very severe. RESULTS: One week after surgery, the total score according to OSDI was significantly increased with a total value of 14.4 ± 4.2 (p = 0.001). Schirmer I was 15.8 ± 4.3 mm preoperatively and decreased significantly in the first postoperative week (p = 0.001), before reaching the preoperative level again after three months. TBUT was 12.6 ± 1.5 s preoperatively, decreased significantly to 9.7 ± 1.5 s during the first postoperative week, and normalized to 12.4 ± 1.3 s by the end of the third month. The meniscus height was 0.245 ± 0.055 mm preoperatively, significantly lowered to 0.229 ± 0.057 mm in the first postoperative period and nearly normalised by the third postoperative month to 0.241 ± 0.051 mm. In the first postoperative week, the rate of mild KCS was observed in 30% of patients. At one month, this decreased to 10% and at three months was no longer demonstrable in any patient. CONCLUSION: One of three patients experienced mild KCS after cataract surgery. The symptoms lasted up to three months. This should be taken into account preoperatively and appropriate therapy should be planned.

Serial intraocular lens opacifications of different designs from the same manufacturer: Clinical and light microscopic results of 71 explant cases.

PURPOSE: To report clinical findings and light microscopic results of 71 opacified hydrophilic acrylic intraocular lenses (IOLs). SETTING: Vivantes Klinikum Neukoelln, Ophthalmology Department, Berlin, Germany. DESIGN: Retrospective case series. METHODS: Sixty-three patients (71 eyes) were referred to the clinic because of vision-impairing IOL opacification between December 2012 and September 2016 after routine cataract surgery elsewhere. The explanted IOLs were analyzed with light microscopy at the John A. Moran Eye Center (University of Utah, Salt Lake City, Utah, USA). Medical records were reviewed for visual acuity, comorbidities, and complications. Clinical follow up was 6 months. RESULTS: Seventy-one opacified 1-piece or 3-piece hydrophilic acrylic IOLs (Lentis) of different designs from 2009 to 2012 (LS-502-1, LS-402-1Y, LS 312-1Y, LS-313-1Y, L-402, L-312) were found. Morphological findings were surface, subsurface, or deep calcifications of the IOL material. Explantation was performed 4 years ± 1.2 (SD) after initial phacoemulsification. The mean patient age was 78.6 ± 8.2 years. Ocular and systemic comorbidities were found without statistical correlation: the most frequent were diabetes, uveitis, and glaucoma. The preoperative mean corrected distance visual acuity changed from 0.63 ± 0.47 logarithm of the minimum angle of resolution (logMAR) to 0.20 ± 0.28 logMAR postoperatively (P < .001). CONCLUSIONS: Different designs of IOLs by the same manufacturer, implanted between 2009 and 2012, developed late calcification with significant visual loss after routine cataract surgery. No medical, surgical, or ophthalmologic trigger could be determined. A manufacture issue might be the reason for the opacification.

Trabecular microbypass stents as minimally invasive approach after conventional glaucoma filtration surgery.

PURPOSE: To evaluate long-term efficacy and safety of 2 trabecular microbypass stents in patients with advanced primary open-angle glaucoma (POAG) and insufficient intraocular pressure (IOP) after previous filtration surgery. SETTING: Vivantes Klinikum Neukölln, Augenklinik, Berlin, Germany. DESIGN: Retrospective case series. METHODS: Eyes with uncontrolled and advanced POAG since 2014 were assessed. All eyes previously had at least 1 filtration surgery procedure. The anatomical landmarks and configuration of the anterior chamber angle had to be identified easily. Two iStents were placed nasally into Schlemm canal. RESULTS: The study comprised 42 patients (42 eyes); 18 eyes had 1 previous glaucoma filtration surgery. During the follow-up of 12 months, the mean IOP in cases of primary failure of filtration surgery decreased from preoperative 23.8 mm Hg ± 3.9 (SD) to 15.2 ± 2.7 mm Hg. For cases with more than 1 previous filtration surgery, the mean IOP decreased from preoperative 26.1 ± 5.7 mm Hg to 16.3 ± 3.3 mm Hg. Medications were reduced from 2.7 ± 0.9 to 2.0 ± 1.1. No intraoperative or perioperative complications occurred. CONCLUSIONS: For eyes with previous filtration surgery and medically uncontrolled IOP, the implantation of 2 stents provided a minimally invasive and safe reduction of mean IOP to less than 18 mm Hg at 12 months. The number of medications was also reduced.

Comparison of slit lamp-adapted optical coherence tomography features of fellow eyes of acute primary angle closure and eyes with open angle glaucoma.

PURPOSE: The aim of this study was to assess the possibility of discriminating a narrow and occludable chamber angle by means of digital gonioscopy. METHODS: In a prospective controlled clinical study 40 eyes of 40 patients were enrolled. 20 patients that had suffered acute angle closure glaucoma (ACG) on the fellow eye were compared to 20 patients with open angle glaucoma (OAG). Anterior segment imaging with SL-OCT (Heidelberg Engineering, Heidelberg, Germany) enabled the delineation, by means of automatic signal analysis, of several important parameters of the anterior chamber angle region, which were compared to those revealed from direct contact glass gonioscopy and ultrasound biometry. RESULTS: The anterior segment structures were automatically recognized by the SL-OCT software in 70 % of the ACG patients and in all of the OAG cases (100 %) (p = 0.025). Anterior chamber angle (ACA) was 15.55° ± 6.92° in the ACG group and 34.6° ± 8.9° in the OAG group, whereas angle opening distance (AOD) was 199.55 ± 62.29 µm in ACG and 452.67 ± 123.91 µm in OAG. A good correlation was found in the direct gonioscopic findings (r = 0.85, p < 0.001), but there were significant differences between both groups (p < 0.001). Mean real central anterior chamber depth (rACD) was evaluated to be 1.75 and 2.79 mm in ACG and OAG, respectively, showing a significant difference (p < 0.0001) and the highest (although not statistically significant) sensitivity and specificity above all other parameters tested in discriminating between OAG and ACG eyes. Discrimination criteria revealed a relevant narrowing of the anterior chamber angle region for values below 22° (ACA), 276 µm (AOD) and 2.08 mm (rACD). CONCLUSIONS: Digital gonioscopy by means of SL-OCT allowed a non-invasive and objective imaging of the anterior chamber configuration that could be used as a screening method for narrow and occludable angles. The method could contribute to a timely identification of angle closure and alert clinicians to further determine whether a peripheral iridotomy should be performed.

Diode laser cyclophotocoagulation versus cyclocryotherapy in the treatment of refractory glaucoma.

PURPOSE: The aim of the present study was to evaluate the efficacy of diode laser cyclophotocoagulation (DCPC) and cyclocryotherapy (CCT) in the treatment of refractory glaucoma and compare the postoperative complications and discomfort rates. METHODS: In a prospective, randomized, controlled clinical study, 40 eyes of 40 patients with refractory glaucoma were randomly assigned in 2 groups of 20 eyes each to receive either DCPC or CCT. Patients underwent follow-up examinations on the first 3 days and then 1 week and 1, 3, 6, and 12 months after initial treatment. Complications and discomfort after treatment using a visual pain analogue scale were recorded. RESULTS: In the DCPC group, the mean intraocular pressure (IOP) decreased (p<0.05) from 44.3 ± 16.4 mmHg preoperatively to 24.1 ± 7.6 mmHg, 22.8 ± 5.6 mmHg, and 22.5 ± 5.1 mmHg 3, 6, and 12 months posttreatment, respectively. Regarding the CCT group, the mean IOP was reduced (p<0.05) from 46.5 ± 10.4 mmHg to 26.6 ± 12.2 mmHg, 21.2 ± 7.7 mmHg, and 20.6 ± 5 mmHg at the same time intervals. In the DCPC group, the mean IOP reduction was strongly correlated with the number of laser effects (r = 0.65; p<0.01), but 35% needed retreatments. The mean postoperative pain was 5.6 ± 2.9 (DCPC) vs 5.7 ± 2.3 (CCT) (p = 0.91). No severe complications were observed. CONCLUSIONS: Both DCPC and CCT proved to be safe and effective IOP-lowering methods in patients with refractory glaucoma. Diode laser cyclophotocoagulation should be considered as the primary treatment option in refractory glaucoma using an individual treatment dosage.

Biometric evaluation of keratoconic eyes with slit lamp-adapted optical coherence tomography.

PURPOSE: To evaluate slit lamp-adapted optical coherence tomography for morphological imaging and morphometrical measurements in keratoconic eyes. METHODS: Using slit lamp-adapted optical coherence tomography, we examined 32 eyes of 20 consecutive patients with keratoconus and described morphological attributes of the cornea. Furthermore, in a subgroup of 19 eyes, we measured morphometrical values of the cornea and compared these values with those of an age-matched control group of 19 normal eyes. RESULTS: Of the 32 keratoconic eyes, 23 eyes had marked corneal thinning of less than 450 µm, 18 eyes had central stromal scarring, and 3 eyes had intrastromal cysts from acute hydrops formation. Central corneal thickness was measured as 374 ± 106 µm in the group of 19 keratoconic eyes, compared with 503 ± 127 µm in the control group (P < 0.05); anterior chamber depth was 3.6 ± 0.4 mm versus 3.1 ± 0.4 mm (P < 0.05); anterior curvature mean radius was 7.2 ± 1.2 mm versus 8.6 ± 1.0 mm (P < 0.05); posterior radius was 5.5 ± 0.7 mm versus 6.8 ± 0.7 mm (P < 0.05). CONCLUSIONS: This study provides further validation that anterior segment optical coherence tomography is a reliable method to assess important parameters for diagnosis and therapeutic outcome control of patients with keratoconus. This method may be particularly useful as a safe and well-defined preoperative diagnostic tool before keratoplasty or corneal cross-linking.

Potential use of riboflavin/UVA cross-linking in bullous keratopathy.

BACKGROUND: Collagen cross-linking of the cornea has been shown by us to have an antiedematous effect in the cornea. The aim of the present study was to examine if this effect can be used for the treatment of bullous keratopathy. METHODS: This clinical interventional case series included 3 patients (3 eyes) with bullous keratopathy due to pseudophakia, corneal transplant rejection, and Fuchs' endothelial dystrophy. After dehydration for 1 day using 40% glucose, the central 8 mm of the cornea were abraded and cross-linked with the photosensitizer riboflavin and UVA (370 nm, 3 mW/cm(2)) for 30 min. Optical coherence tomography pachymetry measurements of the central cornea were performed at various time intervals. RESULTS: Corneal thickness was reduced by 90.33 +/- 17.04 microm on average 3 days after cross-linking and by 93.67 +/- 14.22 microm after 8 months. The bullous changes of the epithelium were markedly improved, resulting in loss of pain and discomfort. Visual acuity was significantly improved in the case without prior stromal scarring. CONCLUSIONS: Cross-linking might become another useful tool in the treatment of bullous keratopathy. It is primarily suited for patients with pain symptoms, restricted visual prognosis or to extend the time interval for an upcoming corneal transplantation.

Hydration behavior of porcine cornea crosslinked with riboflavin and ultraviolet A.

PURPOSE: To examine the influence of a new crosslinking treatment on corneal swelling properties that correlate with the degree of crosslinking. SETTING: Department of Ophthalmology, Vivantes-Klinikum Neukölln, Berlin, Germany. METHODS: Twenty freshly enucleated porcine eyes were crosslinked by applying the photosensitizer riboflavin and ultraviolet-A (UVA) light (370 nm, 3 mW/cm2) for 30 minutes. After the eyes were treated and incubated for 24 hours in a moist chamber, 15 eyes were examined by biomicroscopy and optical coherence tomography (OCT); 5 eyes were examined by light microscopy. Five control eyes were included. RESULTS: Using light microscopy, a characteristic swelling pattern with 3 zones was identified in the crosslinked porcine cornea: an anterior intensely crosslinked zone of 242 microm, an intermediate partially crosslinked zone of 238 microm (hydration factor 2.2), and a noncrosslinked posterior zone of 1355 microm (hydration factor 2.7). A condensed OCT signal was demonstrated in the treated portion of the anterior stroma to a depth of 520 microm with a pronounced line at 540 microm, correlating with the combined anterior and intermediate layers after hydration in the histological analysis. In the nonhydrated state of the crosslinked cornea, the anterior zone was deduced to be 242 microm; the intermediate zone, 109 microm; and the posterior zone, 501 microm. Therefore, the maximum depth of the crosslinking effect was 351 microm. CONCLUSIONS: Collagen crosslinking using riboflavin and UVA led to a significant change in the swelling behavior of the anterior stroma, confirming prior findings that the crosslinking effect is strongest in the anterior half of the stroma. Crosslinked cornea did not induce a specific signal on OCT, and OCT is therefore not suited for clinical controls of the crosslinking effect.

Online optical coherence pachymetry to evaluate intraoperative ablation parameters in LASIK.

PURPOSE: The ablation of corneal tissue with the excimer laser can be variable and can lead to miscorrections. The purpose of this study was to evaluate intraoperative ablation parameters during laser-assisted in-situ keratomileusis (LASIK) with online optical coherence pachymetry (OCP). METHODS: In a prospective, nonrandomized, comparative clinical study, the ablation parameters were continuously assessed intraoperatively with online OCP (Heidelberg Engineering, Lübeck, Germany) in 45 myopic and 10 hyperopic LASIK treatments. The central intraoperative ablation values were compared with the calculated values of the excimer laser (ESIRIS, Schwind, Germany) and the postoperative refraction. The ablation process and the ablation rate in mum per layer, time, and dioptric correction were evaluated in myopic corrections. RESULTS: In myopic LASIK treatments, a linear ablation process was measured with a mean correlation coefficient of -0.968 +/- 0.04. The intraoperative ablation rate was, on average, 0.59 +/- 0.17 microm per layer, 1.45 +/- 0.48 microm per second, and 24.63 +/- 7.81 microm per corrected diopter. These values were 28.7% to 29.6% higher (P < 0.001) than the calculated values. There was a significant correlation (P < 0.001) for the ablation rate per layer (r = 0.823), per second (r = 0.869), and corrected diopter (r = 0.892), but no correlation (r = 0.21, P = 0.239) between the measured linear ablation process and the postoperative refraction. During hyperopic LASIK treatments, without ablation of the corneal center, there was a significant decrease (P = 0.005) of the stromal thickness by 18.34 +/- 14.13 microm, which corresponded to a mean corneal dehydration rate of 0.27 microm per second. CONCLUSIONS: Online OCP allowed a clinical evaluation of intraoperative ablation parameters in LASIK. Further studies are needed to assess a possible active control of the excimer laser ablation from these continuous values, which could possibly improve current ablation nomograms.

Continuous measurement of corneal dehydration with online optical coherence pachymetry.

PURPOSE: Online optical coherence pachymetry (online OCP) allows continuous central corneal thickness measurements over time. In this study, the effect of dehydration on corneal tissue was investigated with online OCP. METHODS: Twelve eyes of 11 patients were examined with online OCP, and the central corneal thickness was registered over 5 minutes after insertion of an eyelid speculum. RESULTS: Online OCP measurements revealed no decrease in reproducibility after 5 minutes of dehydration. The initial mean central corneal thickness was 538 +/- 48 microm. After 5 minutes the central corneal thickness decreased to 483 +/- 43 microm (P = 0.001). This corresponded to a mean corneal thinning of 55 +/- 4 microm (10.2%) at a rate of 0.19 microm/s. CONCLUSIONS: Online OCP was suitable for continuous measurements of corneal changes caused by dehydration. These dehydration effects should be particularly considered in refractive corneal surgery.

Imaging interface fluid after laser in situ keratomileusis with corneal optical coherence tomography.

A 41-year-old myopic patient who had laser in situ keratomileusis 6 months earlier was treated for a complete retinal detachment (RD) with proliferative vitreoretinopathy. Surgical treatment consisted of an encircling band, pars plana vitrectomy, and silicone oil filling. Postoperatively, the patient developed marked corneal edema with no increase in intraocular pressure (IOP) as measured by applanation tonometry. Interface fluid was confirmed by corneal optical coherence tomography. Quantification of the corneal structures revealed that corneal edema was in the residual posterior stroma predominantly. The epithelial and flap thickness did not change significantly. The case demonstrated that after vitreoretinal surgery for RD repair, transient corneal endothelial cell dysfunction developed, causing marked edema of the posterior corneal stroma and interface fluid accumulation. However, an increase in IOP cannot be excluded.

Noncontact goniometry with optical coherence tomography.

OBJECTIVE: To assess the value of noncontact goniometry with optical coherence tomography (OCT) compared with current clinical parameters in the evaluation of the anterior chamber angle (ACA). DESIGN: Prospective observational study of 138 eyes of 109 patients. METHODS: The ACA parameters and angle-opening distance (AOD) were measured with slitlamp-adapted OCT goniometry. The iris and scleral thickness and the iris convexity were assessed with OCT. Both ACA and AOD were compared with the clinical parameters of gonioscopy grade, limbal anterior chamber depth (ACD), ultrasonographic central ACD, and lens-axial length (LAL) ratio. RESULTS: Noncontact goniometry with OCT revealed mean +/- SD values of 28 degrees +/- 16 degrees for the ACA and 381 +/- 234 mum for the AOD. The mean +/- SD iris thickness was 369 +/- 84 mum, and the scleral thickness at the scleral spur was 943 +/- 148 mum. There was a significant correlation (P<.001) with the clinical parameters of gonioscopic grading, limbal ACD, ultrasonographic central ACD, and LAL ratio. The sensitivity and specificity of OCT goniometry to detect an occludable angle were 86% and 95% for ACA and 85% and 90% for AOD, respectively. CONCLUSIONS: Noncontact goniometry with OCT was helpful in evaluating the anterior chamber structures and as a screening modality. Goniometry with OCT could improve the noninvasive clinical assessment and treatment of patients with glaucoma.

Influence of cataract surgery on corneal endothelial cell density estimation.

PURPOSE: To assess the effect of cataract surgery on semiautomated human corneal endothelial cell density (ECD) estimation using noncontact specular microscopy. METHODS: In this prospective clinical study, 62 consecutive patients undergoing cataract surgery were studied. To evaluate possible variations of accuracy and agreement under clinical circumstances, the corneal ECD was determined before and after cataract surgery. The parameter ECD (cells/mm) in the central and paracentral cornea was consecutively determined with 2 algorithms available in a noncontact specular microscope [fixed-frame method (FFM) and automatic center method (ACM)]. The postoperative evaluation was performed at 1 day, after 4 weeks, and after 6 months. The accuracy, the relative error, and the 95% limits of agreement (LoA) were determined for both counting methods. RESULTS: The overall group-averaged accuracy was -19.4 cells/mm (0.86%) centrally and -17.3 cells/mm (0.76%) paracentrally. The LoA (95% CI) were within 234 cells/mm (10.4%) and 250 cells/mm (10.9%), respectively. After cataract surgery, a slight decrease in accuracy was noted in the central (2.09%) and paracentral areas (1.76%). The relative error increased from 3.66% to 6.02% centrally and from 4.96% to 6.55% paracentrally. The LoA (95% CI) increased from +/-194 cells/mm to +/-304 cells/mm centrally and from +/-275 cells/mm to +/-322 cells/mm paracentrally. In the later postoperative period, endothelial stabilization improved the accuracy and agreement in ECD estimation. CONCLUSIONS: The estimation of ECD after cataract surgery employing current algorithms was achieved with a clinically acceptable level of accuracy and agreement. However, the analysis of images in the early postoperative period as well as paracentral corneal areas revealed larger variabilities. This revealed that the FFM and ACM counting methods cannot be used interchangeably under all circumstances. The ACM seemed preferable when only low-quality images were available and permitted determination of additional qualitative endothelial cell parameters.

Lamellar keratotomy to correct astigmatism in cataract surgery.

BACKGROUND: For the correction of astigmatism in cataract surgery, several incisional procedures have been developed. In this study, a modification of lamellar keratotomy was evaluated to correct astigmatism in cataract surgery. METHODS: Prospectively 32 eyes of 25 patients with a preoperative astigmatism greater than 1.5 D were studied. All patients were treated with lamellar keratotomy with an incision width of 6 mm and a radial length of 1.5 mm placed at the limbus in the steep meridian. Phacoemulsification and IOL implantation were then performed through a 3.2-mm corneal tunnel incision. After 4 weeks, mean astigmatism, mean corneal power changes, and mean surgically-induced astigmatism derived from vector analysis in the central 3-mm optical zone were determined. RESULTS: The mean astigmatism decreased from 2.75 +/- 0.80 D preoperatively to 1.58 +/- 0.91 D after 4 weeks (P < 0.001). There were no significant changes (P=0.614) of the mean corneal power. The mean surgically-induced astigmatism was 2.59 +/- 1.50 D. The induced changes were more accentuated in superior incisions. In corneal topography, 78% of the treated eyes revealed a characteristic threefold pattern of the mid-peripheral cornea postoperatively, which impaired the corneal optical performance in ray-tracing analysis. CONCLUSIONS: Lamellar keratotomy effectively reduced high preoperative astigmatism in cataract surgery. This surgical approach was combined with a superior, temporal, or oblique corneal incision.

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.

Monitoring corneal structures with slitlamp-adapted optical coherence tomography in laser in situ keratomileusis.

PURPOSE: To monitor corneal structures with slitlamp-adapted optical coherence tomography (OCT) in laser in situ keratomileusis (LASIK). SETTING: Department of Ophthalmology, Vivantes Klinikum Neukölln, Berlin, Germany. METHODS: In this prospective, nonrandomized, comparative clinical case series of consecutive patients who had LASIK for myopia and myopic astigmatism, the corneal structures were studied with slitlamp-adapted OCT at a wavelength of 1,310 nm. The central corneal thickness (CCT) and epithelial, flap, and residual stromal thicknesses were assessed preoperatively, immediately after surgery, on postoperative day 1, and then, on average, after 8, 35, and 160 days. RESULTS: Twenty-five eyes of 13 patients were included. The attempted mean spherical equivalent correction was -6.11 diopters (D) +/- 2.16 (SD) with a mean calculated stromal ablation depth of 92 +/- 24 microm. The CCT was 516 +/- 26 microm preoperatively and 453 +/- 40 microm postoperatively (P<.001). The epithelial thickness increased from 57.0 +/- 7.7 microm preoperatively to 61.0 +/- 7.5 microm postoperatively (P =.04). Imaging of the hyperreflective interface was possible in all patients for up to 15 months. The flap and residual stromal thickness was 211 +/- 28 microm and 344 +/- 48 microm, respectively, immediately after LASIK and 164 +/- 21 microm (P<.001) and 284 +/- 32 microm (P<.001), respectively, on postoperative day 1. There were no further significant changes during the follow-up. The overall mean reproducibility was +/-4.50 microm (coefficient of variation [CV] 0.94%) for CCT, +/-4.99 microm (CV 8.57%) for epithelial thickness, +/-6.25 microm (CV 3.55%) for flap thickness, and +/-7.09 microm (CV 2.42%) for residual stromal thickness. CONCLUSION: Slitlamp-adapted OCT can be used to longitudinally monitor the variable structures of the cornea, epithelium, flap, and residual stroma in LASIK.

Influence of indocyanine green staining on the biomechanical strength of porcine internal limiting membrane.

PURPOSE: Indocyanine green (ICG) has recently been introduced to stain selectively the internal limiting membrane (ILM) of the retina for ILM peeling. The aim of the present in vitro study was to examine the effect of ICG staining on the biomechanical properties of porcine ILM. METHODS: Two parallel 10 x 7 mm strips of central retina were prepared from each of the 40 porcine eyes. 0.005% ICG staining combined with white light illumination for 3 min was performed. Unstained, nonilluminated and 0.1% glutaraldehyde-treated specimens were used as controls. Biomechanical-force elongation measurements were performed using an automated material tester. The absorption spectrum of the ICG solution and the emission spectrum of the light source was measured. RESULTS: After ICG staining of the retina combined with 3 min of illumination, a significant increase in ultimate force by 45% and a decrease in ultimate elongation by 24% was found. Without light exposure, there was no such effect, suggesting a light-dependent process. After 30 min of 0.1% glutaraldehyde treatment, there was an increase in ultimate force by 107% and a decrease in ultimate elongation by 66.6%. The absorption spectrum of the light source was continuous in the range from 400 to 800 nm including the absorption peak of ICG at 700 nm. CONCLUSIONS: ICG staining of the retina including the ILM causes a significant increase in the biomechanical stiffness thereby facilitating ILM peeling. The effect is due to a photosensitizing effect of ICG leading to collagen cross-linking.