Satinder Pal Singh Grewal

Corneal collagen crosslinking using riboflavin and ultraviolet-A light for keratoconus

PURPOSE: To evaluate changes in corneal curvature, corneal elevation, corneal thickness, lens density, and foveal thickness after corneal collagen crosslinking with riboflavin and ultraviolet‐A (UVA) light in eyes with progressive keratoconus. SETTING: Grewal Eye Institute, Chandigarh, India. METHODS: Subjective refraction, best corrected visual acuity (BCVA), Scheimpflug imaging, and optical coherence tomography were performed preoperatively and 1 week, 1, 3, and 6 months, and 1 year after crosslinking. RESULTS: There were no significant differences (P > 0.05) in mean values between preoperatively and 1 year postoperatively, respectively, in BCVA (0.22 ± 0.10 and 0.20 ± 0.10), spherical equivalent (−6.30 ± 4.50 diopters (D) and −4.90 ± 3.50 D), or cylinder vector (1.58 × 7° ± 3.8 D and 1.41 × 24° ± 3.5 D). There was no significant difference in mean measurements between preoperatively and 1 year postoperatively, respectively, for central corneal thickness (458.9 ± 40 μm and 455.2 ± 48.6 μm), anterior corneal curvature (50.6 ± 7.4 D and 51.5 ± 3.6 D), posterior corneal curvature (−7.7 ± 1.2 D and −7.4 ± 1.1 D), apex anterior (P = .9), posterior corneal elevation (P = .7), lens density (P = .33), or foveal thickness (175.7 ± 35.6 μm and 146.4 ± 8.5 μm; P = .1). CONCLUSIONS: Stable BCVA, spherical equivalent, anterior and posterior corneal curvatures, and corneal elevation 1 year after crosslinking indicate that keratoconus did not progress. Unchanged lens density and foveal thickness suggest that the lens and macula were not affected after UVA exposure during crosslinking.

Evaluation of subconjunctival bevacizumab as an adjunct to trabeculectomy a pilot study.

PURPOSE To determine whether bevacizumab can reduce bleb failure in patients undergoing first-time trabeculectomy for primary open-angle glaucoma (POAG) or chronic angle-closure glaucoma (CACG). DESIGN Nonrandomized, open-label, prospective, interventional case series. PARTICIPANTS Twelve individuals (7 males; 5 females) with a diagnosis of POAG or CACG, a recorded intraocular pressure (IOP) of more than 21 mmHg (between 10 am and 12 pm), glaucomatous damage on visual field or optic disc, and taking a maximum tolerated dose of IOP-lowering medication. INTERVENTION Unilateral trabeculectomy with subconjunctival injection of bevacizumab (0.05 ml, 1.25 mg) adjacent to the bleb using a 30-gauge needle and tuberculin syringe administered immediately after trabeculectomy. MAIN OUTCOME MEASURES Treatment success (unmedicated IOP of 6 to 16 mmHg inclusive) at 6 months; bleb characteristics according to the Moorfields bleb grading system on days 1, 7, 30, 90, and 180; incidence of postoperative intervention with 5-fluorouracil or mitomycin C; bleb needling; and incidence of and time to surgical failure. RESULTS Mean age was 54.6+/-13.6 years. The mean preoperative IOP was 24.4+/-7.1 mmHg (range, 12-44 mmHg) and the patients were taking an average of 2.7+/-1.6 IOP-lowering medications (range, 1-4). The mean postoperative IOP was 8+/-3.1 mmHg (range, 4-13 mmHg) on day 1, 9.4+/-2.7 mmHg (range, 6-14 mmHg) on day 7, 10.9+/-2.8 mmHg (range, 8-16 mmHg) at 1 month, 10.3+/-2.5 mmHg (range, 7-14 mmHg) at 3 months, and 11.6+/-2.2 mmHg (range, 8-14 mmHg) at 6 months follow-up with no IOP-lowering medications. Preoperative best-corrected visual acuity was 0.70+/-0.3, whereas at 6 months after trabeculectomy, it was 0.66+/-0.3 (P = 0.39). After a mean follow-up of 182 days, of the 12 eyes, a successful trabeculectomy with respect to IOP control was observed in 11 eyes (92%), with an average IOP reduction of 52%. CONCLUSIONS In this pilot study with a small number of subjects, 6-month outcomes suggest that subconjunctival bevacizumab is a potential adjunctive treatment for reducing the incidence of bleb failure after trabeculectomy. FINANCIAL DISCLOSURE(S) The authors have no proprietary or commercial interest in any materials discussed in this article.

Correlation of nuclear cataract lens density using Scheimpflug images with Lens Opacities Classification System III and visual function.

PURPOSE To calculate the average lens density (ALD) and nuclear lens density (NLD) using Scheimpflug images and to determine their correlation with logarithmic minimal angle resolution (logMAR) best-corrected visual acuity (BCVA), contrast sensitivity (CS), and lens grading based on the Lens Opacities Classification System (LOCS) III. DESIGN Cross-sectional observational study. PARTICIPANTS One hundred ten patients with age-related nuclear cataract. METHODS The logMAR BCVA was recorded using Early Treatment Diabetic Retinopathy Study charts and photopic contrast-sensitivity using CSV-1000LV (Vector Vision, Greeneville, OH). Fifty Scheimpflug images (Pentacam, Oculus, Germany) covering 360 degrees of the lens were obtained for 1 eye of each patient after dilation. All Scheimpflug images were exported to ImageJ software (NIH, Bethesda, MD) for analysis wherein the ALD and NLD (using a mask applied to the lens nuclear area) were calculated in pixel-intensity units. Repeatability was determined using coefficient of variation (CoV) and intraclass correlation coefficient (ICC). Lens opacity on slit-lamp images was graded using LOCS III for nuclear opalescence (NO) and nuclear color (NC). MAIN OUTCOME MEASURES We evaluated ALD and NLD on Scheimpflug images and their correlation with NO and NC LOCS III grading, BCVA, and photopic CS. RESULTS The ICC for ALD and NLD were 0.983 and 0.99, respectively; the CoV were 3.92+/-1.76% and 2.57+/-0.74%, respectively. The ALD correlated with NO (r = .774; P<0.001), NC (r = .732; P<0.001), BCVA (r = 0.696; P<0.001), and CS at 3 cycles per degree CPD (P = 0.011), 6, 12, and 18 CPD (P<0.001). The NLD correlated with NO (r = .859; P<0.001), NC (r = .81; P<0.001), BCVA (r = .760; P<0.001), CS at 3 CPD (P = 0.002), 6, 12, and 18 CPD (P<0.001). The NLD had a significantly stronger correlation with BCVA (P<0.05), NO (P<0.01), NC (P<0.01), and CS at 6 CPD (P<0.01) and 12 CPD (P<0.005) compared with ALD. CONCLUSIONS Repeatable 360 degrees lens density measurements were obtained using Scheimpflug imaging. A stronger correlation was observed between NLD and LOCS III grading, BCVA, and photopic CS than with ALD. The NLD is an objective and repeatable method for assessment of lens density, which could be helpful in longitudinal studies monitoring nuclear cataracts.

Repeatability of corneal parameters with Pentacam after laser in situ keratomileusis

Aim: To investigate the coefficient of repeatability (CR) for corneal parameters evaluated with Pentacam after laser in situ keratomileusis (LASIK) in myopic eyes. Design and Setting: Prospective, non-interventional, non-comparative study in an institutional setup. Materials and Methods: Forty eyes of 40 consecutive subjects who had undergone LASIK for myopia were assessed with the Scheimpflug system (Pentacam 70700: Oculus, Wetzlar Germany). The mean of five consecutive measurements of all the corneal parameters was recorded and CR was calculated as standard deviation of the difference from the mean of these repeat measurements divided by the mean response. The statistical significance of the CR was calculated for these parameters at 5% significance level. Results: The best CR was observed for the periphery of the anterior corneal curvature (0.18%) and the least for the horizontal meridian of the posterior corneal curvature (1.29%). Despite being significantly different ( P < 0.001), both the measurements were highly repeatable in post-LASIK eyes. The central, apical and minimal corneal thickness had a CR of 1%, 0.78% and 0.77% respectively. These were equally repeatable ( P >0.323). The CR of the mean radius of curvature of the anterior cornea (0.29%) was significantly better ( P < 0.001) than the posterior corneal curvature (0.57%). Conclusion: The CR for the post-LASIK cornea with Pentacam was the best for the anterior corneal curvature. Significantly, Pentacam has a high degree of repeatability for the posterior corneal curvature, which has a potential for early detection of keratectasia in these eyes. Post-LASIK pachymetry with Pentacam also showed excellent repeatability.

Assessment of central corneal thickness in normal, keratoconus, and post-laser in situ keratomileusis eyes using Scheimpflug imaging, spectral domain optical coherence tomography, and ultrasound pachymetry.

PURPOSE: To compare the central corneal thickness (CCT) in normal eyes, eyes with keratoconus, and eyes after laser in situ keratomileusis (LASIK) using 3 methods. SETTING: Cornea Clinic, Grewal Eye Institute, Chandigarh, India. METHODS: In this study, CCT was measured by sequential Scheimpflug imaging, spectral‐domain anterior segment optical coherence tomography (AS‐OCT), and ultrasound (US) pachymetry. RESULTS: Each of the 3 groups comprised 50 eyes. There were no differences between the 3 groups in age, sex, or intraocular pressure. In normal eyes, CCT was statistically significantly higher by US pachymetry (mean 525.8 μm ± 41.4) [SD] than by Scheimpflug imaging (mean 519.4 ± 40.9 μm) and AS‐OCT (mean 517.9 ± 41.5 μm) (both P<.001). In keratoconus eyes, CCT by US pachymetry (mean 446.4 ± 57.9 μm) was statistically significantly higher than by Scheimpflug imaging (mean 439.6 ± 62.1 μm) (P = .002) and AS‐OCT (mean 441.8 ± 58.4 μm) (P = .007). In post‐LASIK eyes CCT by US pachymetry (mean 462.4 ± 44.7 μm) was significantly higher than by Scheimpflug imaging (mean 457.9 ± 33.6 μm) (P = .012) and AS‐OCT (mean 455.4 ± 43.2 μm) (P<.001). In all groups, CCT measured by Scheimpflug imaging and AS‐OCT was similar. CONCLUSIONS: There was a statistically significant difference between Scheimpflug imaging and US pachymetry and AS‐OCT, with US pachymetry measurements being consistently thicker. Thus, CCT should be interpreted in the context of the instrument used. Financial disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Pentacam Tomograms : A Novel Method for Quantification of Posterior Capsule Opacification

PURPOSE To develop and validate a method to quantify posterior capsule opacification (PCO) in eyes after cataract surgery and intraocular lens implantation using Scheimpflug Pentacam tomograms and compare its validity with slit lamp retroillumination image analysis. METHODS One hundred twenty-four pseudophakic eyes of 124 patients were divided into two groups. Group 1 consisted of 40 eyes with visually significant PCO, and group 2 consisted of 84 eyes without visually significant PCO. Pentacam Imaging was performed after full mydriasis using the 50-scan acquisition protocol, and high-resolution tomograms were reconstructed and analyzed using ImageJ freeware. Retroillumination photographs were captured for group 1 eyes using the Topcon digital slit lamp, and these were analyzed using POCOman software to calculate an aggregate severity grade and percentage PCO value. Correlation coefficients were calculated for PCO values obtained using POCOman and ImageJ. RESULTS Mean PCO percentage value obtained using POCOman software was 23.34 +/- 6.25 U, mean aggregate PCO severity grade was 0.46 +/- 0.28 U, and mean pixel-intensity value using ImageJ was 31.071 +/- 8.26 U. There was a significant positive correlation between the percentage PCO (P = 0.000; r = 0.864) and PCO severity grade (P = 0.001; r = 0.490) obtained for group 1 eyes using slit lamp retroillumination images and PCO pixel intensity obtained using Pentacam tomograms. CONCLUSIONS Retroillumination photographs are the standard for quantifying PCO. Pentacam tomograms are easier to obtain and are free of flash reflections, and they allow for a more objective analysis. The correlation between the two methods demonstrates that ImageJ analysis of Pentacam tomograms is a viable tool for PCO analysis.

Comparison of Scheimpflug imaging and spectral domain anterior segment optical coherence tomography for detection of narrow anterior chamber angles

PurposeTo compare the performance of anterior chamber volume (ACV) and anterior chamber depth (ACD) obtained using Scheimpflug imaging with angle opening distance (AOD500) and trabecular-iris space area (TISA500) obtained using spectral domain anterior segment optical coherence tomography (SD-ASOCT) in detecting narrow angles classified using gonioscopy.MethodsIn this prospective, cross-sectional observational study, 265 eyes of 265 consecutive patients underwent sequential Scheimpflug imaging, SD-ASOCT imaging, and gonioscopy. Correlations between gonioscopy grading, ACV, ACD, AOD500, and TISA500 were evaluated. Area under receiver operating characteristic curve (AUC), sensitivity, specificity, and likelihood ratios (LRs) were calculated to assess the performance of ACV, ACD, AOD500, and TISA500 in detecting narrow angles (defined as Shaffer grade ≤1 in all quadrants). SD-ASOCT images were obtained at the nasal and temporal quadrants only.ResultsTwenty-eight eyes (10.6%) were classified as narrow angles on gonioscopy. ACV correlated with gonioscopy grading (P<0.001) for temporal (r=0.204), superior (r=0.251), nasal (r=0.213), and inferior (r=0.236) quadrants. ACV correlated with TISA500 for nasal (r=0.135, P=0.029) and temporal (P=0.160, P=0.009) quadrants and also with AOD500 for nasal (r=0.498, P<0.001) and temporal (r=0.517, P<0.001) quadrants. For detection of narrow angles, ACV (AUC=0.935; 95% confidence interval (CI) =0.898–0.961) performed similar to ACD (AUC=0.88, P=0.06) and significantly better than AOD500 nasal (AUC=0.761, P=0.001), AOD500 temporal (AUC=0.808, P<0.001), TISA500 nasal (AUC=0.756, P<0.001), and TISA500 temporal (AUC=0.738, P<0.001). Using a cutoff of 113 mm3, ACV had 90% sensitivity and 88% specificity for detecting narrow angles. Positive and negative LRs for ACV were 8.63 (95% CI=7.4–10.0) and 0.11 (95% CI=0.03–0.4), respectively.ConclusionsACV measurements using Scheimpflug imaging outperformed AOD500 and TISA500 using SD-ASOCT for detecting narrow angles.

International values of corneal elevation in normal subjects by rotating Scheimpflug camera.

PURPOSE: To examine whether clinically significant differences exist in corneal elevation data from a sampling of countries worldwide. SETTING: International multicenter. DESIGN: Evaluation of diagnostic test or technology. METHODS: One randomly selected eye of normal adults from 8 countries spanning 6 continents was examined using the Pentacam Eye Scanner. Anterior and posterior elevations were measured at the apex and thinnest point. Differences between countries were assessed by Kruskal‐Wallis. Normative thresholds were defined according to the Tukey method. RESULTS: The study examined 1 eye of 555 patients. Median elevations were similar across countries. Upper limits of normal for collective international data were 3.5 μm, 6.0 μm, 7.5 μm, and 13.5 μm at the anterior apex, anterior thinnest point, posterior apex, and posterior thinnest point, respectively. These and country‐specific thresholds were similar to normal values from previous data; however, country‐specific thresholds flagged additional eyes in China, Egypt, and India. Those thresholds were 4.5 μm at the anterior thinnest point (China and Egypt), 7.4 μm at the posterior apex (India), and 11.0 μm and 12.0 μm at the posterior thinnest point (China and Egypt, respectively). CONCLUSIONS: In general, international variations were clinically insignificant; thus, current screening guidelines maintained their applicability. Notable exceptions were China, Egypt, and India, where country‐specific thresholds may better reflect the test populations and minimize potential false negative results from screening. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned. Additional disclosures are found in the footnotes.

Clinical applications of Scheimpflug imaging in cataract surgery

Since the Scheimpflug principle was first described over a century ago, there has been a great interest among ophthalmologists for the use of Scheimpflug camera in anterior segment imaging. Scheimpflug imaging has since advanced significantly and modern day instruments provide comprehensive imaging and topographic data of the anterior segment. In this article the clinical applications and limitations of Scheimpflug imaging in modern cataract surgery patients are discussed. This article reviews recent work on assessment of lens transparency for cataract grading and integrity, using preoperative lens density measurements to help predict phacoemulsification parameters, its utility in challenging situations like capsular bag distension syndrome and traumatic cataract and assessment of density of the posterior capsule for objectively quantifying posterior-capsule opacification.

Posterior corneal elevation after LASIK with three flap techniques as measured by Pentacam.

PURPOSE To evaluate and compare posterior corneal changes using elevation data obtained from Pentacam (Oculus Optikgeräte GmbH) Scheimpflug imaging in eyes undergoing LASIK with three different modes of flap creation: IntraLase femtosecond laser FS60 (Abbott Medical Optics) (femtosecond group), Amadeus (Ziemer Group AG) mechanical microkeratome (keratome group), or flap formation using 20% alcohol laser epithelial keratomileusis (LASEK) (LASEK group). METHODS Ninety myopic patients (90 eyes) undergoing refractive surgery were recruited. The change in posterior corneal elevation at 21 predetermined points in the central 5-mm area was measured using exported elevation data from the Pentacam before LASIK and 18 months postoperative and was compared among and within three modes of flap creation. RESULTS Mean change in posterior elevation in the central 5-mm area was 5.13±4.16 μm for the femtosecond group, 5.78±4.42 μm for the keratome group, and 6.68±4.72 μm for the LASEK group and was similar among groups (P=.59). Change in posterior elevation before and after LASIK was not significant within any group (P=.342, P=.232, and P=.321 for the femtosecond, keratome, and LASEK groups, respectively). Preoperative spherical equivalent, central corneal thickness, ablation depth, and estimated residual bed thickness did not correlate with change in posterior corneal elevation for the femtosecond, keratome, or LASEK groups (P>.05). CONCLUSIONS Using Pentacam elevation data, there were no significant changes in posterior corneal elevation following LASIK among or within the three methods of flap creation. At 18 months after LASIK, the posterior corneal surface is not displaced anteriorly significantly and is equally stable using these three surgical techniques.