Difference In Pachymetry Research Articles

Analysis of epithelial corneal layer after phacoemulsification

Aims/Purpose: To verify whether changes occur in the epithelial corneal layer after phacoemulsification depending on the number of endothelial cells.Methods: This is a prospective observational study on patients who were going to have cataract removal surgery. The patients were divided into two groups in accordance with their endothelial cell count: one group with more than 1500 endothelial cells and the other with fewer than 1500 cells. We analysed the epithelial layer with the RTVue (Optovue, Fremon, USA) device. The epithelial mapping was performed before surgery, the day after the intervention, a week after the procedure, 1 and 6 months post‐surgery.Results: The epithelial layer was greater in patients who had more than 1500 endothelial cells. This difference was statistically significant at every visit except the day after surgery, when there were no differences between the groups.Conclusions: Immediate postoperative corneal oedema following phacoemulsification affects the cornea irregularly at the sublayer level. Corneal oedema secondary to the cataract removal surgery can affect the epithelial layer, but this is a transient change since a week after surgery this layer showed the same differences as before the procedure. These changes were encountered in the central cornea, without involvement of the incision sites. Patients with fewer endothelial cells showed a lower epithelial layer thickness even though there were no significant statistical differences in pachymetry between the two groups. Possibly this difference is secondary to a higher stromal thickness layer to compensate for such changes.

Role of Corneal Epithelial Measurements in Differentiating Eyes with Stable Keratoconus from Eyes that Are Progressing

To evaluate measures of corneal epithelium in eyes that showed documented signs of keratoconus (KC) progression and compare with stable eyes and healthy controls. Also, to determine the correlation of these epithelial parameters with maximum keratometry (K max) and pachymetry. Prospective, observational, comparative study. One-hundred and fifty eyes from 150 patients. The study included 50 eyes from patients with documented KC progression, 50 eyes with stable KC, and 50 clinically normal eyes to serve as controls. A spectral-domain (SD)-OCT imaging was obtained in all eyes, and mean values were compared between the groups. The correlation of epithelial parameters with K max and thinnest pachymetry was also investigated. For the purposes of this study, the epithelial measures maximum, minimum, superior, and inferior values as well as the difference between the minimum and maximum (min-max) and epithelial standard deviation were considered, obtained from SD-OCT and compared between groups. Measurements of the thinnest point and min-max in pachymetry were also recorded. The only epithelial parameter that presented a statistically significant difference between stable and progressive KC was epithelium min-max. Although stable KC presented epithelium min-max mean values of-18.2 ± 6.6, progressive KC eyes presented mean values of-23.4 ± 10.3 (P < 0.0001). Epithelial maximum (P= 0.16), minimum (P= 0.25), superior (P= 0.28), inferior (P= 0.23), and standard deviation (P= 0.25) values were not significantly different between stable and progressive eyes. Difference min-max pachymetry points in stable (-108.3 ± 33.5) and progressive KC (-115.2 ± 56.0) were not significantly different (P= 0.723). There was no significant correlation between epithelium min-max with corneal thinning (P= 0.39) or K max (P= 0.09) regardless of disease progression. Epithelial measures are useful to identify KC eyes that are progressing; the parameters that measure the difference between min-max epithelium points were significantly different between stable and progressive groups, unlike this difference in pachymetry. Finally, this epithelial parameter seems to be independent of corneal thinning and K max. Proprietary or commercial disclosure may be found after the references.

Pachymetry and Elevation Back Map Changes in Keratoconus Patients After Crosslinking Procedure.

Introduction:The crosslinking (CXL) procedure using the standard Dresden protocol is established as the gold standard for the treatment of progressive keratoconus. Aim:The aim of this paper is to correlate the pachymetry and elevation back map (EBM) changes in the period from 3 to12 months of keratoconus patients after the CXL procedure. MMethods:Forty-four eyes of 34 patients with keratoconus were analyzed after performed standard Dresden protocol CXL procedure. All of them underwent complete preoperative examination with a follow up of 12 months with a focus on pachymetry and EBM changes performed by Oculus Pentacam (Scheimpflug technology) analysis. Results:Pachymetry changed significantly in 12 months post cross-linking, especially in the first 6 months after which it slightly increased. Differences in EBM preoperatively and 12 months postoperatively were not statistically significant. Conclusion:Corneal pachymetry in keratoconus patients decreases after the CXL procedure. Differences in pachymetry preoperatively and 3, 6 and 12 months postoperatively were statistically significant, but the value of corneal thickness increased from the third month to 12 months post-op. Differences in EBM preoperatively and 12 months postoperatively were not still statistically significant, which is good, because the increase in elevation, as one of the signs of progression of the keratoconus - did not occur.

Direct measurement of anterior corneal curvature changes attributable to epithelial removal in keratoconus

To compare the tomography of the corneal epithelium and Bowman layer in eyes with moderate to severe keratoconus before and after epithelial debridement. University hospital tertiary referral center. Prospective case series. Dual-channel Scheimpflug combined with Placido-disk tomography was used to measure the corneal variables in eyes with keratoconus having corneal crosslinking immediately before and after epithelial debridement. The differences in pachymetry, axial keratometry, astigmatism magnitude, asphericity, total corneal power, and spherical aberrations were computed. The study comprised 30 eyes of 30 patients. After epithelial removal, the central (0.0 to 4.0mm) and midperipheral (4.0 to 7.0mm) corneal zones were significantly thinner mean (21μm±14 [SD] and 35±44μm, respectively). The mean anterior axial flat keratometry (K) (+1.71 diopters [D]), steep K (+2.14 D), maximum K (+2.13 D), corneal astigmatism (+1.11 D), asphericity (-0.31), and total corneal power changes (+2.03 D) were significantly different after epithelial debridement. There were no significant changes in posterior corneal flat K or steep K, posterior corneal astigmatism, or posterior asphericity. There were no significant differences in the mean astigmatic axis (anterior or posterior corneal surface) or spherical aberration after epithelial debridement. In eyes with moderate to severe keratoconus, the tomography of Bowman layer was significantly steeper than that of the epithelium; thus, epithelial debridement increased the magnitude of anterior corneal keratometry, astigmatism, and prolateness. These data suggest that the corneal epithelium smooths the underlying Bowman layer irregularity in keratoconus.

Correlation between estimated and measured corneal ablation and refractive outcomes in laser in situ keratomileusis for myopia

To evaluate the difference between the measured and the intended postoperative central corneal thickness (CCT) by optical low-coherence reflectometry (OLCR) for 3 months after myopic laser in situ keratomileusis (LASIK) and correlate it with refractive outcomes. Center for Refractive Therapy, Department of Ophthalmology, Ludwig-Maximilians-University Munich, Germany. The CCT was measured by OLCR before and 6 weeks and 3 months after myopic LASIK. The correlation between the difference in pachymetry and the difference in the measured and planned postoperative refraction was proven by linear regression and Pearson product moment correlation analysis (P<.05). In a subset of eyes with a 7.0 mm optical zone, the effect of the calculated ablation depth on the difference in pachymetry was evaluated. Based on the laser algorithm data, the intended ablation was 100 microm or less in Subgroup 1 and 100 microm or more in Subgroup 2. Forty-three eyes of 25 patients were evaluated, with 25 eyes in the subset. The difference between the measured and intended postoperative CCT was 11.1 microm +/- 8.1 (SD) at 6 weeks and 13.8 +/- 7.5 microm at 3 months. The correlation between this difference and the difference in refraction was poor (r(2) = 0.005 microm and r(2) = 0.009, respectively). With greater ablation depth (Subgroup 2), the difference in pachymetry decreased by 3 months postoperatively. The lack of correlation between differences in the measured and intended CCT and the final refraction shows the complexity of intraoperative variables in LASIK and the effect of individual wound healing.

Pachymétrie cornéenne centrale dans la population pédiatrique par microscopie spéculaire non-contact : à propos de 405 cas

Central corneal thickness has become very important in the interpretation of intraocular pressure. The aim of this study was to correlate pachymetry values in a pediatric population with age, sex, and refraction. To our knowledge, the scientific literature has not reported such information. This prospective study was conducted from May 2005 to November 2006 and included 405 eyes (186 eyes in boys and 219 eyes in girls) in children undergoing a general pediatric ophthalmologic visit. Patient age ranged from 3 to 16 years; three age groups were formed: 3-4 years, 5-9 years, 10-16 years. Objective refraction with cycloplegic was measured using a Nidek ARK 700 A autorefractometer and three refraction groups were formed. Pachymetry measures were taken using the Topcon SP 2000P specular microscopy. Exclusion criteria were a history of ocular surgery, lens wearers, and any disease that could alter the cornea. The mean age was 8.21 +/- 3.55 years, the mean refraction was +1.24 +/- 4.02 D. The mean central pachymetry was 529 +/- 32 microm: 534 +/- 31 microm in the male group and 524+/-31 microm in the female group, establishing a difference in pachymetry with no differences in refraction or age between the two groups. In the refraction groups, we found a significant difference in pachymetry between emmetropic (523+/-33 microm) and hyperopic (533 +/- 31 microm) groups and between hyperopic and myopic groups (520 +/- 32 microm) (p=0.005). There was no difference between emmetropic and myopic groups (p=0.902), nor in pachymetry between age groups (p=0.086). Except for differences found in refraction groups, the results reported herein were similar to those found with the ultrasonic method (the reference method), but they had been obtained under general anesthesia in most studies. Even though this is not the reference method of pachymetry measures, it seems more appropriate for children, because it is reliable, the measurements are taken quickly, they are noninvasive, and they do not cause the child undue stress (noncontact method).

Influence of Final Corneal Thickness in Visual Acuity After Deep Lamellar Endothelial Keratoplasty

To determine if the final corneal thickness after deep lamellar endothelial keratoplasty (DLEK) is correlated in any way with visual performance. One hundred fifty-five consecutive eyes without macular disease underwent DLEK surgery and had pachymetry recorded at 6 months postoperatively. The eyes were grouped according to visual acuity, and pachymetry was correlated between groups: group 1 (20/20, 20/25, or 20/30), n = 38; group 2 (20/40 or 20/50), n = 79; group 3 (20/60, 20/70, or 20/80), n = 30; group 4 (20/100 or worse), n = 8. The mean pachymetry, SD, and range of pachymetry for each group are as follows: group 1, 0.571 +/- 0.080 mm (range, 0.408-0.784 mm); group 2, 0.598 +/- 0.080 mm (range, 0.437-0.816 mm); group 3, 0.605 +/- 0.099 mm (range, 0.454-0.945 mm); group 4, 0.607 +/- 0.120 mm (range, 0.410-0.781 mm). There was no significant correlation between vision and corneal thickness (P = 0.312). There was no statistical difference in pachymetry among all 4 groups (P = 0.323). The influence of pachymetry in visual acuity is not relevant (r = 0.03). The variance in corneal thickness in DLEK does not seem to influence visual results.

Postoperative Corneal Swelling Correlates Strongly to Corneal Endothelial Cell Loss After Phacoemulsification Cataract Surgery

To evaluate postoperative corneal swelling as a predictor of corneal endothelial cell loss after phacoemulsification cataract surgery. Prospective observational case series. Thirty patients planned for routine phacoemulsification cataract surgery were included. Ultrasonic pachymetry and specular microscope endothelial photography of the central and nasal portions of the cornea and Orbscan II slit-scan tomography were performed preoperatively and the day after surgery. The 30 patients were selected from 41 patients based on their increase in central corneal thickness: the first 10 cases with a <5% increase, the first 10 with a 6% to 20% increase, and the first 10 with a > or =20% increase. The same measurements were repeated after 1, 2, and 3 months. The primary outcome measures were corneal endothelial cell loss and increase in pachymetry. Several other parameters were also registered, including age, degree of cataract, visual acuity, phacoemulsification time and energy, total operation time, and the amount of infusion fluid used. The central corneal swelling at postoperative day 1 was strongly correlated with the central corneal endothelial cell loss at 3 months (R(2) = 0.785, P < .001). In this series, with large variations in the corneal swelling at the first postoperative day, the degree of permanent corneal endothelial damage was reflected in the degree of early postoperative corneal swelling. Measuring the difference in pachymetry at postoperative day 1 is a useful way to assess the effects on the corneal endothelium exerted by the phacoemulsification procedure.

Ectasia after LASIK

Ectasia after LASIK

Risk factors for epithelial erosions in laser in situ keratomileusis

Purpose To determine the risk factors for an epithelial defect during laser in situ keratomileusis (LASIK). Setting LASIK Vision, Toronto, Ontario, Canada. Methods In this prospective cohort study, 926 patients (1852 eyes) presenting for LASIK over a 6-month period were evaluated for age, sex, Fitzpatrick Skin Type (FST), eye color, hair color at 3 years of age, facial skin wrinkling, ethnicity (Lancer Ethnicity Scale [LES]), keratometry, Schirmer I reading, corneal thickness, and preexisting signs of corneal epithelial dystrophy. In all patients, LASIK was performed using the Technolas 217 laser (Bausch & Lomb), the Hansatome® microkeratome (Bausch & Lomb), and the same nomogram settings. Results Fourteen percent of patients had significant epithelial fragility. In patients with FST I or II or LES 1 or 2, the relative risk of an epithelial defect was 10 times greater than in other patients; in those older than 40 years, it was 6 times greater than in other patients; in those with lighter hair or eye color, it was 2 to 3 times greater than in patients with darker hair or eyes. There was no significant difference in pachymetry, vertical or horizontal keratometry, or Schirmer readings between eyes with epithelial defects and eyes without. Conclusions The risk of epithelial erosions during LASIK strongly correlated with patients’ skin type and age.