Altered Corneal Biomechanics According to the Biomechanical E-Staging in Pellucid Marginal Degeneration.

PURPOSE: The purpose of this study was to investigate corneal biomechanics in pellucid marginal degeneration (PMD) compared with healthy controls using Corvis ST (Oculus, Germany) by using the new biomechanical E-staging (based on the Corvis Biomechanical Factor, the linearized Corvis Biomechanical Index) together with tomographic parameters. METHODS: Corneal biomechanical and topographic data of 75 eyes of 75 patients with PMD and 75 eyes of 75 age-matched and sex-matched healthy controls were investigated. Topographic parameters (K1, K2, Kmax, central corneal thickness (CCT), and Belin/Ambrósio Deviation Index (BAD-D) were evaluated in dependence of and correlated with the biomechanically defined E-stages. Biomechanical parameters were also recorded for the 2 groups. RESULTS: Patients with PMD showed higher K2, Kmax, BAD-D, and Corvis Biomechanical Factor values and a lower CCT compared with healthy controls (P < 0.001). The E-stage was positively correlated with K1, K2, Kmax, BAD-D, and intraocular pressure difference and negatively correlated with CCT. Stage-dependent analysis revealed a significant increase in K1, K2, Kmax (P < 0.001), and BAD-D (P = 0.041) in stage E3 compared with E0 and a significant decrease in stage E2 in CCT (P = 0.009) compared with E0. CONCLUSIONS: This study showed that patients with PMD may have a reduced corneal stiffness compared with healthy controls which worsens with increasing E-stage. Significant changes in topographic parameters were observed at stage E2 for CCT and at stage E3 for K1, K2, Kmax, and BAD-D when compared with stage E0.

Comparison of Two Topical Lubricants on the Corneal Surface Recovery and Patient Discomfort After Photorefractive Keratectomy.

INTRODUCTION: This study aimed to compare the effect of two preservative-free (PF) artificial tears, one containing carboxymethylcellulose (CMC) (control group) vs another containing hyaluronic acid and hydroxypropyl guar (HA + HP-guar) (study group), on the healing of the corneal epithelium and the ocular discomfort after bilateral photorefractive keratectomy (PRK) surgery. METHODS: A total of 68 patients that were scheduled to have PRK to correct myopia were randomized into two groups: 34 patients (68 eyes) in the study group and 34 patients (68 eyes) in the control group. Ocular examinations were performed on postoperative days 1, 4, 7, 30, and 90, evaluating the diameter of the de-epithelized cornea, the fluorescein staining using the Oxford scale, the tear film osmolarity and stability (tear breakup time), and the pain using visual analog scale (VAS). RESULTS: On postoperative day 4, 97% of the study eyes vs 84.4% of the control eyes were completely re-epithelized (p = 0.01). Less ocular pain was observed on postoperative day 3 in the study group (5.0 (3.0-6.0) vs 6.0 (3.5-7.0), p = 0.03). No differences were observed beyond postoperative day 7 in the healing of the corneal epithelium, non-invasive Keratograph breakup time (NIKBUT), and the self-perceived ocular discomfort between the two groups. CONCLUSION: The current study shows faster healing of the corneal epithelium and less ocular pain and discomfort in the first days after PRK with the use of topical lubricants containing HA + HP-guar compared to conventional CMC artificial tears, probably due to the different trophic effect of the aforementioned tears on the corneal epithelial cells. TRIAL REGISTRATION: EudraCT No. 2020-003488-25.

Baseline Characteristics of 1976 Patients With Ectatic Corneal Disorders at a Single Center From 2010 to 2021: A Cross-Sectional Study of the Homburg Keratoconus Center.

OBJECTIVES: The study objective was to analyze the baseline characteristics of keratoconus (KC) patients at the Homburg Keratoconus Center from 2010 to 2021. METHODS: This cross-sectional study included 3,674 eyes, with analysis of demographics, clinical findings, visual function, endothelial measurements, and topographic, tomographic, and corneal biomechanical data from the first visit. RESULTS: Mean patient age was 36.3±13.8 years. The mean uncorrected distance visual acuity in log of minimal angle of resolution was 0.60 (20/80, Snellen equivalent), and the corrected mean was 0.3 (20/40). Of 1976 patients, 48.9% reported eye rubbing. Mean values (ranges) were 49.4±6.3 (36.3-78.0) D for steep keratometry, 462.4±66.0 (48.0-659.0) µm for thinnest corneal thickness, 9.7±8.7 (-0.5 to 88.8) for Belin/Ambrósio enhanced ectasia total deviation, 0.8±0.4 (0.0-1.0) for the Corvis biomechanical index, 0.9±0.2 (0.0-1.0) for the tomographic biomechanical index, 0.1±0.5 (-0.9 to 2.0) for the KC match index, 8.3±1.8 (2.2-17.7) mm Hg for corneal hysteresis, 7.1±2.2 (0.0-17.0) mm Hg for corneal resistance factor, and 2,562.9±326.3 (1,011-3,937) cells/mm2 for endothelial cell density. The average ABCDE KC stage was A2B3C1D1E2. Distance-corrected visual acuity correlated strongly with topometric, tomographic, and biomechanical data ( P <0.001). CONCLUSIONS: This comprehensive description of baseline features of KC patients at a tertiary center provides a reference for further longitudinal and international multicentric studies.

Choroidal thickness as a possible predictor of non-response to intravitreal bevacizumab for macular edema after retinal vein occlusion.

To evaluate outcomes of intravitreal bevacizumab (IVB) treating macular edema (ME) after retinal vein occlusion (RVO) following pro re nata (PRN) regimen and investigate potential predictors of non-response. Retrospective analysis of 126 treatment-naive eyes with ME after RVO. Eyes were treated initially with IVB of 1.25 mg/ml. Therapy was switched in case of non-response. Outcome measures included best-corrected visual acuity (BCVA) and central macular thickness (CMT), which were recorded over 4 years of treatment. BCVA improved significantly during first 2 years. CMT decreased significantly during the 4-year follow-up period. Switching was required in 42 eyes (33%). 34 eyes (26.9%) were switched to steroids, while 8 eyes (6.3%) were switched to other anti-VEGF due to diagnosed glaucoma. Switching occurred after 12.4 ± 8.3 months and an average of 8 ± 4.1 IVBs. Compared with the treatment-responsive group, the treatment-unresponsive group had significantly worse BCVA, higher CMT and subfoveal choroidal thickness (SFCT) at baseline. Treatment IVB following PRN regimen showed significant functional and anatomic improvement in patients with ME after RVO. Switching was required in more than one third of eyes. Higher baseline SFCT could be considered as predictor for non-response to such therapy and thus an indicator of early switching.

Risk Factors for Keratoconus Progression in Children Compared with Young and Middle-aged Adults.

BACKGROUND: To investigate the risk factors for keratoconus progression in children (10 - 18 years old; age group 1) compared to young adults (19 - 35 years old; age group 2) and middle-aged adults (36 - 55 years old; age group 3). PATIENTS/METHODS: Ninety-seven children, 445 young adults, and 342 middle-aged adults underwent total ophthalmic examination including clinical refraction, slit lamp examination, corneal tomography, eye biometry, and biomechanical properties measurements. Comparisons were assessed among three age groups and between progressive and nonprogressive eyes. Logistic regression was applied to determine the potential prognostic factors for keratoconus progression in the three age groups. RESULTS: Univariate logistic regression analysis show that the most prominent factors associated with progression were corneal posterior vertical radius (RVP), eye rubbing (RUB), slit lamp corneal thinning (SLT), contact lens use (CL), and central corneal thickness (CCT) in all age groups. Additionally, the anterior chamber volume (ACV) and keratoconus match index (KMI) were associated with progression in age group 1. Location of the thinnest corneal thickness at the vertical axis (TCTy), distance from apex to the thinnest point (BADISTAPEX), scissor reflection in retinoscopy (SKIAREFLEX), and Vogt striae were associated with progression in age group 2, and TCTy, anterior and posterior asphericity (ASPA and ASPP, respectively), BADISTAPEX, SKIAREFLEX, and Vogt striae were associated with progression in age group 3. The multivariate model with the highest predictability indicated RVP, ACV, and SLT as independent determinants of progression in age group 1 (AUC: 90%, sensitivity: 88.9%, specificity: 90.9%), RVP, ACV, SLT, and SKIAREFLEX in group 2 (AUC: 81.6%, sensitivity 88.5%, specificity: 70.3%), and RVP, SLT, Vogt striae, and CL in age group 3 (AUC: 80%, sensitivity 82.8%, specificity: 73%). CONCLUSION: ACV and KMI seem to play a major role in the progression of pediatric KC compared to adults. This is probably due to different anatomical and biomechanical characteristics of a child's eye globe.

Differential Diagnosis of Keratoconus Based on New Technologies.

Keratoconus (KC) must be distinguished from other corneal ectatic diseases and thinning disorders for stage-appropriate and suitable management of each condition. The most relevant corneal pathologies that may imitate the tomographic KC pattern are pellucid marginal degeneration (PMD), keratoglobus, posterior keratoconus, and Fuchs-Terrien marginal degeneration (FTMD). In moderate cases of KC, differentiation is typically possible using slit lamp examination and corneal tomography with evaluation of the location of the corneal thinning region. In early cases, however, differential diagnosis may be more challenging since the cornea may look relatively normal. In severe cases, the extended area of corneal thinning also complicates differentiation. Biomicroscopic findings cannot always give all the information needed to distinguish KC from related ectatic corneal conditions. The aim of this work is to discuss contemporary techniques and findings to assist physicians to identify the correct diagnosis. Corneal topography has been used in recent decades as the main tool for imaging in ectatic corneal diseases. Moreover, Scheimpflug cameras (corneal tomographers), which analyze both anterior and posterior corneal surfaces, curvatures, pachymetry, elevation data, higher order aberrations, Fourier analysis of keratometric data, and corneal density have become the most promising tools for diagnosis and follow-up of ectatic diseases. A noninvasive air pulse tonometer in conjunction with an ultrahigh-speed Scheimpflug camera complements tomographic findings by analyzing biomechanical corneal properties. Α confocal microscopy system, which is a novel clinical technique for the study of corneal cellular structure, could contribute effectively in the same direction. Moreover, anterior segment optical coherence tomography (AS-OCT) creates cross-sections, which can be generated into a three-dimensional structure to produce corneal epithelial thickness (ET) measurements. ET mapping is increasingly recognized as a sensitive tool for the diagnosis of ocular surface disorders. Combining information of all these systems could lead to a more effective identification and differential diagnosis of ectatic corneal disorders.

Impact of intravitreal ranibizumab, aflibercept and bevacizumab on retinal ganglion cell and nerve fibre layer thickness in Neovascular age-related macular degeneration.

PURPOSE: To compare the effects of monotherapy with intravitreal ranibizumab, aflibercept and bevacizumab on retinal ganglion cell layer (RGCL) and retinal nerve fibre layer (RNFL) in patients with naïve neovascular age-related macular degeneration (nAMD). METHODS: This is a retrospective cohort study with three-groups comparison. 83 patients and 97 eyes on continuous monotherapy with an intravitreal anti-vascular endothelial growth factor (anti-VEGF) were followed for 24 months and divided into three groups according to anti-VEGF (aflibercept: 25 eyes, ranibizumab: 34 eyes, bevacizumab: 38 eyes). Main outcome measures included: RGCL and RNFL thickness, best corrected visual acuity (BCVA), central macular thickness (CMT), macular volume (MV) and the presence of intraretinal fluids (IRF), subretinal fluids (SRF) and retinal pigment epithelial atrophy (RPE-atrophy). All outcome measures were recorded at the time of the first injection, 1 and 2 years after treatment and compared longitudinally and between groups. RESULTS: The mean age was 79 ± 7 years. The RGCL thickness, MV, CMT and the presence of IRF and SRF decreased significantly within all three medication groups (p < 0.05 for all) with no significant difference between groups over the 2-year follow-up period (p > 0.10 for all). The decrease in RNFL thickness was not significant within or between the groups after a 2-year follow-up (p > 0.055 for all). RPE-atrophy increased significantly after 2 years in all three groups (p < 0.028 for all) with no significant difference between groups at all three time points (p > 0.307 for all). BCVA was comparable between the three groups over the 2-year follow-up period (p > 0.22 for all). CONCLUSIONS: Monotherapy with intravitreal aflibercept, bevacizumab and ranibizumab was associated with comparable significant decreases in RGCL thickness, CMT, MV, IRF and SRF in naïve nAMD patients during the first 2 years of treatment. Furthermore, no significant differences either in BCVA or RNFL thickness were observed between the three intravitreal anti-VEFGs during the first 2 years of treatment.

Effect of prostaglandin analogues on the biomechanical corneal properties in patients with open-angle glaucoma and ocular hypertension measured with dynamic scheimpflug analyzer.

PURPOSE: The aim of the study is to evaluate the effect of topical prostaglandin (PG) treatment on the corneal biomechanical properties in treatment-naïve patients with either primary open-angle glaucoma (POAG) or ocular hypertension (OHT) using the Corvis ST device. METHODS: This is an observational study. We analyzed the Corvis ST dynamic corneal response parameters of our database using the newest software available. Thirty-four eyes of 34 patients were included. They were all newly diagnosed and treatment-naïve. Patients were evaluated at baseline and after 6 months of treatment with prostaglandin analogues. Ultrasound pachymetry, Optical Coherence Tomography (OCT) and a 24-2 visual field test were performed in baseline visit. Goldman Applanation Tonometry (GAT-IOP) and Corvis ST dynamic corneal response parameters were registered at baseline and at the 6-month visit. RESULTS: After 6 months of treatment, the IOP decrease (Δ) values obtained with the different tonometers were ΔGAT -6.5 ± 3.7, ΔIOPnct -4.4 ± 5.7 and ΔbIOP -3.8 ± 5.4. The differences between ΔGAT vs ΔIOPnct, ΔGAT vs ΔbIOP, and ΔIOPnct vs ΔbIOP, were statistically significant (p < 0.05 for all comparisons). Statistically significant lower values of the stress-strain index (SSI) (1.77 ± 0.3 at baseline vs 1.54 ± 0.27 at the 6-month visit) were found (p = 0.0002). CONCLUSION: The SSI provided by the Corvis ST seems to decrease significantly after topical prostaglandin therapy. We believe that our results support the hypothesis that topical PG therapy does decrease the corneal stiffness and thus, that the ocular hypotensive effect of these drugs is overestimated if GAT is used for IOP measurement.

The Effect of Antiglaucoma Procedures (Trabeculectomy vs. Ex-PRESS Glaucoma Drainage Implant) on the Corneal Biomechanical Properties.

The aim of this study is to investigate the effect of two antiglaucoma procedures, namely trabeculectomy and Ex-PRESS mini-shunt insertion on the biomechanical properties of the cornea. This is a prospective study. Thirty patients (30 eyes) were included in the study. Nineteen eyes had an Ex-PRESS shunt inserted (Group 1) and 11 had trabeculectomy (Group 2). The examination time points for both groups were one to three weeks preoperatively and at month 1, 6, and 12 postoperatively. Corneal biomechanical properties (corneal hysteresis (CH) corneal resistance factor (CRF)) were measured with the Ocular Response Analyzer (ORA). In group 1, CH was significantly increased at 6 and 12 months compared to baseline values. Corneal hysteresis was also higher at 1 month postoperatively, but this increase did not reach statistical significance. In group 2, the CH was significantly increased at all time points compared to the preoperative values. CRF decreased at all time points postoperatively compared to the preoperative values in both groups. The difference (preoperative values to postoperative values at all time points) of the CH and CRF between the two groups was also compared and no significant differences were detected between the two surgical techniques. Trabeculectomy and the EX-PRESS mini-shunt insertion significantly alter the corneal biomechanical properties as a result of the surgical trauma and the presence of the shunt in the corneal periphery. When compared between them, they affect the corneal biomechanical properties in a similar way.

Comparison of Subthreshold 532 nm Diode Micropulse Laser with Conventional Laser Photocoagulation in the Treatment of Non-Centre Involved Clinically Significant Diabetic Macular Edema.

BACKGROUND: The aim of the study was to investigate the effect of the 532 nm (green) diode subthreshold micropulse laser (SML) in the treatment of non-centre involved clinically significant macular edema (CSME) in comparison to the conventional laser photocoagulation (CLP). METHODS: A total of 60 eyes of patients diagnosed with non-centre involved CSME were randomly divided into two groups. SML photocoagulation was performed in the first group (G1), while CLP in the second one (G2). Central macular thickness (CMT) and best corrected visual acuity (BCVA) were measured prior to treatment and at 3 and 6 months after intervention. RESULTS: G1 participants had significantly better CMT at 6 months after laser application (p = 0.04) compared to G2. Additionally, CMT in both groups was significantly lower 6 months after laser application in comparison to baseline values (G1: p < 0.001, G2: p = 0.002). Moreover, significant improvement was detected 6 months after SML in G1 regarding BCVA compared to values before laser treatment (p = 0.001). CONCLUSION: SML was more effective than CLP in reducing CMT and improving BCVA in patients with non-centre involved CSME. Therefore, it seems that SML can be a good substitute for CLP in DME treatment if confirmed in future studies.

Penetrating deep sclerectomy in primary open-angle and pseudoexfoliative glaucoma.

PURPOSE: To evaluate the outcomes of a new antiglaucoma surgical method, a modification of the standard deep sclerectomy, the penetrating deep sclerectomy. PARTICIPANTS: Patients with medically uncontrolled primary open-angle glaucoma or pseudoexfoliative glaucoma were prospectively, in a consecutive way, enrolled in this study. METHODS: The study was conducted in Glaucoma Unit, Department of Ophthalmology, University of Hospital of Alexandroupolis, Greece, in 29 eyes of 29 patients. In a fornix-based surgical procedure, all eyes underwent the proposed penetrating deep sclerectomy (deep sclerectomy plus trabeculectomy) with the use of mitomycin C applied intraoperatively (0.2 mg/mL for 2 min). The follow-up period was 3 years. Ocular examination was conducted before the operation and at 1, 3, 6, 12, 18, 24, and 36 months postoperatively. RESULTS: The average reduction in intraocular pressure at the end of follow-up was 11.24 (57.88%). The complete success rate (intraocular pressure ⩽21 mm Hg without medication) after 3 years was 58.6%. The qualified success rate (intraocular pressure ⩽21 mm Hg without or with medication) was 75.86%. Postoperatively, the mean number of medication dropped from 3.75 ± 0.89 to 0.89 ± 0.98. Low postoperative complications were recorded. CONCLUSION: During the 3-year follow-up period, penetrating deep sclerectomy presented very positive outcome. The addition of a controlled perforation of the trabeculo-Descemet's membrane in deep sclerectomy, playing the role of an early goniopuncture, seems to ensure a satisfactory outcome and is not associated with additional complications.

Fourier Analysis of Corneal Irregular Astigmatism After Small Incision Lenticule Extraction and Comparison to Femtosecond Laser-Assisted Laser In Situ Keratomileusis.

PURPOSE: Evaluation of spherical component (SC), regular astigmatism (RA), and irregular astigmatism (IA, ie, Asymmetry and Irregularities) 3 years after small incision lenticule extraction (SMILE) and comparison to femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). METHODS: Thirty-two eyes of 21 patients who underwent SMILE for myopia and astigmatism were compared with 32 eyes of 21 patients treated with FS-LASIK. Scheimpflug images were obtained preoperatively and 3 years postoperatively. Fourier analysis of keratometric-derived parameters (SC, RA, Asymmetry, and Irregularities) of the anterior, posterior, and total cornea were evaluated at 4 concentric rings (ring 1, 2 mm diameter; ring 2, 4 mm; ring 3, 6 mm; ring 4, 8 mm) and over the entire 8-mm zone. RESULTS: After FS-LASIK, over the 8-mm zone, the RA and IA of the anterior cornea increased significantly (P ≤ 0.002), whereas SMILE induced an insignificant increase in RA and Asymmetry (P ≥ 0.276) and a decrease in Irregularities (P = 0.770). At the 8-mm zone of the posterior cornea, the Irregularities increased significantly (P = 0.027) after FS-LASIK, whereas SMILE induced no significant changes in the examined variables (P ≥ 0.347). RA and IA of the total cornea increased significantly after FS-LASIK (P ≤ 0.001), whereas SMILE induced an insignificant increase in RA and Asymmetry (P ≥ 0.092) and a significant decrease in Irregularities (P < 0.001). FS-LASIK induced a greater decrease in SC of the total cornea at ring 4 (P = 0.009). CONCLUSIONS: FS-LASIK resulted in a greater increase in RA and Irregularities and greater flattening of the midperiphery of the anterior and total cornea compared with SMILE. The posterior cornea remained unaffected after SMILE, whereas more Irregularities were induced after FS-LASIK over the 8-mm zone.

Impact of light conditions on reading ability following multifocal pseudophakic corrections.

PURPOSE: To examine the impact of light intensity and temperature on reading performance following bilateral pseudophakic multifocal presbyopic correction. PATIENTS AND METHODS: This is a prospective clinic-based trial conducted at the Department of Ophthalmology in the University Hospital of Alexandroupolis, Greece. Three groups of patients were formed (G1: patients with bilateral bifocal implantation, G2: patients with bilateral trifocal implantation, and control group: patients with bilateral pseudophakic monofocal implantation). Reading ability was quantified with the Greek version of MNREAD chart with minimal reading speed at 80 words/min for the following light intensities (25, 50, and 75 Foot-Candles [FC]) and temperatures (3,000, 4,000, and 6,000 K). Preferred light conditions for reading were assessed, as well. ClinicalTrials.gov Identifier: NCT03226561. RESULTS: Control group demonstrated significantly lower reading ability at all light combinations with maximal ability at 75 FC and 6,000 K (0.58±0.18 logMAR). Bifocal group presented a light-dependent reading ability that ranged from 0.45±0.08 logMAR (25 FC and 3,000 K) to 0.40±0.11 logMAR (75 FC and 4,000 or 6,000 K). Trifocal participants presented the best reading ability that was light intensity-independent; however, their performance was reduced at 6,000 K. G1 and G2 preferred primarily intermediate light temperature, while control participants preferred cold light temperature. CONCLUSION: Multifocal pseudophakic corrections improve reading ability; however, they present variable efficacy according to the light conditions.

Efficacy of the travoprost/timolol fixed combination versus the concomitant use of travoprost 0.004% and timolol 0.1% gel formulation.

PURPOSE: To compare the hypotensive effect of travoprost 0.004%/timolol 0.5% fixed combination (TTFC) to the concomitant use of travoprost and timolol 0.1% gel formulation (Trav + Geltim). MATERIALS AND METHODS: Thirty-three patients (62 eyes) were enrolled and divided into two groups. Patients in group 1 (31 eyes) received the TTFC and patients in group 2 (31 eyes) received the concomitant treatment with Trav + Geltim. Patients on previous antiglaucoma treatment discontinued their drops for 2-4 weeks before starting their new treatment (TTFC or Trav + Geltim). The drops were instilled in the evening in group 1 and in group 2, the prostaglandin was installed in the evening, and timolol in the morning. IOP was measured at 1 and 3 months after the initiation of treatment at four time points during the day (09:00, 12:00, 15:00, and 18:00). RESULTS: Both groups showed significant IOP reduction from baseline at all time points at 1 and 3 months. When the two groups were compared, group 2 showed slightly better hypotensive effect that reached statistical significance only at the 18:00 time point at both 1 and 3 months. CONCLUSION: Both the TTFC and the concomitant use of the travoprost/timolol gel showed similar hypotensive effect with the latter being slightly more potent in reducing the IOP.

Corneal Irregular Astigmatism and Curvature Changes After Small Incision Lenticule Extraction: Three-Year Follow-Up.

PURPOSE: To evaluate the long-term changes in anterior and posterior corneal irregular astigmatism and curvatures after small incision lenticule extraction (SMILE). METHODS: Fifty eyes of 28 patients underwent SMILE for myopic astigmatism. All procedures were performed using the VisuMax® femtosecond laser. A Scheimpflug camera was used for preoperative and 3-year postoperative tomography. Anterior and posterior corneal Fourier parameters (spherical component, regular astigmatism, asymmetry, and irregularity) and curvature data were evaluated and compared within 2 subgroups according to the magnitude of the refractive correction (low myopia group: spherical equivalent (SEQ) ≥ -6 D; high myopia group: (SEQ) < -6 D). Associations between all studied parameters were examined. RESULTS: Three years postoperatively, an increase in anterior corneal curvatures and Fourier parameters was detected and the results were strongly correlated with the preoperative SEQ, lenticule thickness, and volume. At the posterior cornea, the flattest radius, corneal astigmatism, spherical component, regular astigmatism, and irregularity decreased only in the high myopia group. A correlation was found between changes in posterior astigmatism and changes in anterior radii (R = 0.349, P = 0.014), SEQ (R = 0.396, P = 0.0049), and lenticule thickness (R = -0.414, P = 0.0031). Moreover, changes in posterior corneal irregularity correlated with the changes in anterior and posterior radii (R = -0.3, P = 0.034, and R = 0.449, P = 0.0012, respectively), changes in preoperative SEQ (R = 0.284, P = 0.0477), and lenticule thickness (R = -0.311, P = 0.0298). CONCLUSIONS: Three years after SMILE, there was a reduction of posterior astigmatism in high refractive corrections. This could result in undercorrection in high refractive treatments. Total irregularities increased despite the compensatory effect of the posterior corneal surface.

Validation of Fourier analysis of videokeratographic data.

PURPOSE: The aim was to assess the repeatability of Fourier transfom analysis of videokeratographic data using Pentacam in normal (CG), keratoconic (KC) and post-CXL (CXL) corneas. METHODS: This was a prospective, clinic-based, observational study. One randomly selected eye from all study participants was included in the analysis: 62 normal eyes (CG group), 33 keratoconus eyes (KC group), while 34 eyes, which had already received CXL treatment, formed the CXL group. Fourier analysis of keratometric data were obtained using Pentacam, by two different operators within each of two sessions. Precision, repeatability and Intraclass Correlation Coefficient (ICC), were calculated for evaluating intrassesion and intersession repeatability for the following parameters: Spherical Component (SphRmin, SphEcc), Maximum Decentration (Max Dec), Regular Astigmatism, and Irregularitiy (Irr). Bland-Altman analysis was used for assessing interobserver repeatability. RESULTS: All parameters were presented to be repeatable, reliable and reproductible in all groups. Best intrasession and intersession repeatability and reliability were detected for parameters SphRmin, SphEcc and Max Dec parameters for both operators using ICC (intrasession: ICC > 98%, intersession: ICC > 94.7%) and within subject standard deviation. Best precision and lowest range of agreement was found for the SphRmin parameter (CG: 0.05, KC: 0.16, and CXL: 0.2) in all groups, while the lowest repeatability, reliability and reproducibility was detected for the Irr parameter. CONCLUSIONS: The Pentacam system provides accurate measurements of Fourier tranform keratometric data. A single Pentacam scan will be sufficient for most clinical applications.

Fourier analysis algorithm for the posterior corneal keratometric data: clinical usefulness in keratoconus.

PURPOSE: To develop an algorithm for the Fourier analysis of posterior corneal videokeratographic data and to evaluate the derived parameters in the diagnosis of Subclinical Keratoconus (SKC) and Keratoconus (KC). METHODS: This was a cross-sectional, observational study that took place in the Eye Institute of Thrace, Democritus University, Greece. Eighty eyes formed the KC group, 55 eyes formed the SKC group while 50 normal eyes populated the control group. A self-developed algorithm in visual basic for Microsoft Excel performed a Fourier series harmonic analysis for the posterior corneal sagittal curvature data. The algorithm decomposed the obtained curvatures into a spherical component, regular astigmatism, asymmetry and higher order irregularities for averaged central 4 mm and for each individual ring separately (1, 2, 3 and 4 mm). The obtained values were evaluated for their diagnostic capacity using receiver operating curves (ROC). Logistic regression was attempted for the identification of a combined diagnostic model. RESULTS: Significant differences were detected in regular astigmatism, asymmetry and higher order irregularities among groups. For the SKC group, the parameters with high diagnostic ability (AUC > 90%) were the higher order irregularities, the asymmetry and the regular astigmatism, mainly in the corneal periphery. Higher predictive accuracy was identified using diagnostic models that combined the asymmetry, regular astigmatism and higher order irregularities in averaged 3and 4 mm area (AUC: 98.4%, Sensitivity: 91.7% and Specificity:100%). CONCLUSIONS: Fourier decomposition of posterior Keratometric data provides parameters with high accuracy in differentiating SKC from normal corneas and should be included in the prompt diagnosis of KC.

The Effect of Corneal Refractive Surgery on Glaucoma.

Laser-assisted refractive procedures have become very popular in the last two decades. As a result, a "generation" of patients with altered corneal properties is emerging. These patients will require both cataract extraction and glaucoma follow-up in the future. Since the glaucoma examination largely depends on the corneal properties, the reshaped postrefractive surgery cornea poses a challenge in the diagnosis, follow-up, and management of the glaucomatous patient. In order to overcome this problem, every patient who is planned to undergo corneal refractive surgery must have a thorough glaucoma examination in order for the ophthalmologist to be able to monitor their patients for possible glaucoma development and/or progression. Some examinations such as tonometry are largely affected by the corneal properties, while others such as the evaluation of the structures of the posterior pole remain unaffected. However, the new imaging modalities of the anterior segment in combination with the most recent advances in tonometry can accurately assess the risk for glaucoma and the need for treatment.

Comparison of the biometric measurements calculated with Zeiss IOL-Master and WaveLight OB-820.

BACKGROUND: The primary objective of this study was to investigate the level of agreement between IOL-Master and OB-820 ocular biometers. MATERIALS AND METHODS: In this prospective randomized case series, we measured the anterior chamber depth (ACD), the axial length (AL), the corneal radii (R1, R2), the ratio of mean corneal radius and spherical equivalent and the corneal astigmatism (cylinder [Cyl]) before and after cataract extraction surgery. RESULTS: Significant differences between pre- and postoperative data were observed for ACD for both biometric devices (P<0.01) and Cyl parameter in IOL-Master. Range and 95% limits of agreement (LoA) were clinically significantly different for AL parameter pre- and postoperatively and for R2 and radius and spherical equivalent postoperatively (P<0.001). The rest of the parameters presented sufficient 95% LoA, which imply good agreement. CONCLUSION: In clinical practice, the IOL-master and OB-820 should not be used interchangeably due to discrepancy in the important AL parameter. Both biometers may provide consistent results regarding Cyl, ACD and R1.

Impact of polyethylene glycol 400/propylene glycol/hydroxypropyl-guar and 0.1% sodium hyaluronate on postoperative discomfort following cataract extraction surgery: a comparative study.

BACKGROUND: Universal postoperative guidelines for cataract extraction surgery are yet to be introduced. Artificial tears are gaining popularity as an additional integral component of the postoperative regime. The primary objective of this study was to explore the impact of two prevalent artificial tear preparations on postoperative discomfort following cataract extraction surgery. METHODS: A total of 180 patients that underwent cataract extraction surgery were randomly divided into three groups according to their postoperative regime: a) Study group 1 (SG1) received a fixed combination of tobramycin and dexamethasone (FCTD) quid for 3 weeks and, additionally polyethylene glycol 400/propylene glycol/hydroxypropyl-guar quid, for 6 weeks, b) Study group 2 (SG2) received FCTD quid for 3 weeks and, additionally 0.1% sodium hyaluronate provided in the COMOD® device quid, for 6 weeks, and, c) Control Group (CG) received only FCTD quid for 3 weeks. The following indexes were evaluated at three postoperative checkpoints: 1) Subjective discomfort index (SDI) derived from four direct 10-scale Likert-type questions that were addressed to the patient and pertained to: a) foreign body sensation (FBS), b) blinking discomfort (BD), c) stinging sensation (SS), d) tearing sensation (TS), 2) Tear break-up time (TBUT), 3) Central corneal thickness (CCT) and, 4) Central Corneal Sensitivity (CCS). RESULTS: Both groups showed increased CCT values at the first examination point and reduced CCS values at all examination points. Furthermore, both SGs had better TBUT times at all examination points compared to CG (CG: 8.86 ± 1.08, SG1: 9.59 ± 1.45, CG2: 9.45 ± 1.33, p < 0.05). BD was significantly better in both SGs only at the 1st week of examination, while SDI values were better until the 3rd week and only borderline better at 6th week. Lastly, no significant differences were detected between SGs, regarding all parameters, at all examination points. CONCLUSION: Polyethylene glycol 400/propylene glycol/hydroxypropyl-guar and 0.1% sodium hyaluronate provided in the COMOD® device seem to be equally efficient in alleviating OSD symptoms following cataract extraction surgery and any of them should be routinely added to the postoperative regime. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: https://clinicaltrials.gov/ct2/show/NCT02558218NCT02558218.