Stefania Iaccarino

Prevalence of corneal astigmatism before cataract surgery in Caucasian patients.

Purpose To analyze and quantify the pattern of corneal astigmatism in patients awaiting cataract surgery to provide information for cataract surgeons and intraocular lens (IOL) manufacturers and to establish the demand for toric IOLs in a hospital. Methods This cross-sectional retrospective study evaluated keratometric (K) values measured by partial coherence interferometry (IOLMaster) in cataract surgery candidates, who were then analyzed and correlated by age and axial length (AL) ranges. Results The study evaluated the K values in 757 eyes of 380 patients with a mean age of 71.9 ± 10.2 years (range 33–96 years). The mean corneal astigmatism was 1.02 ± 0.69 D (range 0.06–4.57 D). It was 1 D or higher in 316 (41.74%) eyes. The mean AL was 23.56 ± 1.35 mm (range 20.53–31.86 mm). Conclusions Our study shows that roughly 50% of the eyes have more than 1 D of astigmatism. The results can help hospitals plan and analyze the amount and costs of using toric IOLs in patients with corneal astigmatism.

Long-term results of corneal collagen crosslinking for progressive keratoconus

PURPOSE To evaluate long-term keratoconus stability after corneal crosslinking (CXL) with riboflavin. METHODS In this prospective study, 57 eyes of 55 patients with progressive keratoconus, consecutively treated with ultraviolet A (UVA) - riboflavin CXL, were examined with the corneal topographer Pentacam, the biometer IOLMaster and the analyzer of corneal biomechanics Ocular Response Analyzer before and during a 24 months follow-up after CXL. RESULTS Twenty-four months after CXL, there was a significant improvement in best corrected visual acuity (BCVA) (P<0.01), a significant decrease in corneal thinnest point (CTP), keratometry readings at the keratoconus apex (K max), and corneal volume (CV) (P<0.01), and a significant increase in axial eye length (AL) (P=0.01). No significant changes in anterior chamber volume (ACV) and depth (ACD), (P=0.8), corneal hysteresis (CH) (P=0.16) and corneal resistance factor (CRF) (P=0.06) were found. However, in the subgroup of patients with decreased K max readings 24 months after treatment, both CH and CRF showed a significant reduction (P<0.01). CONCLUSION In the first month after the procedure, CXL induces a reduction in corneal volume. During the 24 months follow-up the cornea tends to recover its original volume with a persistence of the CXL efficacy.

In vivo human corneal deformation analysis with a Scheimpflug camera, a critical review

Corneal morphological analysis has greatly improved in recent years, providing physicians with new and reliable parameters to study. Moreover, today corneal functional too is a routine analysis, thanks to biomechanical evaluation allowed by an ocular response analyzer (Reichert Ophthalmic Instrument, Depew, NY, USA). Corvis ST (OCULUS Optikgeräte GmbH, Wetzlar, Germany), that relies on the ultrahigh speed Scheimpflug camera, is a new device providing corneal deformation parameters measured ny scanning the cornea response to an air puff; it is an instrument able to measure intraocular pressure too. This device could open up a whole new prospective in screening, detecting and managing corneal diseases, intraocular pressure measurement and in evaluating surgical procedures involving the cornea. This paper provides a comprehensive explanation of Corvis ST measurement principles and parameters and a literature review of scientific studies.

Comparison between Corvis and other tonometers in healthy eyes

PURPOSE To determine the agreement of intraocular pressure (IOP) values in healthy eyes among Goldmann applanation tonometer, dynamic contour tonometer, ocular response analyzer and Corvis. Additionally, to study the relationship between their differences with central corneal thickness (CCT) and corneal curvature (CK). METHODS Seventy-six eyes of 76 healthy subjects were examined. Every subject underwent a complete ophthalmic evaluation, a Pentacam scan and three consecutive IOP measurements with each instrument (DCT, GAT, ORA and CST). IOP measurements provided by each device were compared with each other and the differences between them were correlated with morphological parameters obtained by Pentacam (CCT and CK). Statistical analysis was performed using SPSS software, version 18.0. RESULTS The mean age of enrolled subjects was 36.8 ± 10.6 years old. The mean IOP measurements that were obtained with GAT, DCT, ORA and CST was 15.62 ± 2.33 mmHg, 17.44 ± 2.51 mmHg, 15.99 ± 3.58 mmHg and 17.24 ± 3.44 mmHg respectively. The mean CCT was 543.63 ± 36.15 μm, the mean CK was 43.35 ± 1.23 D. GAT and ORA provided IOP values not showing a statistical difference; CST and DCT IOP measurements did not show a statistical difference whereas CST provided statistically higher IOP values both than GAT and both ORA. CONCLUSIONS According to our data, CST produces IOP values that are notably higher than GAT measures; therefore they cannot be used interchangeably. If CST should be used as the next gold standard, higher IOP values will come to be considered normal.

Intraocular lens power calculation: a challenging case.

Purpose To highlight different methods in calculating intraocular lens (IOL) power in the case of undetectable keratometric (K) readings. Case Report A 54-year-old woman was referred to us for cataract surgery in her left eye. The slit lamp examination revealed the presence of corneal scars that did not allow us to take reliable K readings. To calculate them, the following regression formula was used: The IOL power calculation was performed aiming at a postoperative error = −0.5 diopters. One month after surgery, the uncorrected visual acuity was 20/100 and the best spectacles corrected visual acuity was 20/25 with +1.0 −4 × 180 (−1.0 diopter spherical equivalent). Conclusions This seems to be a reliable method to calculate the IOL power when K readings are undetectable, but to make a definitive statement, prospective studies are needed.

New Scheimpflug camera device in measuring corneal power changes after myopic laser refractive surgery

PURPOSE To assess the accuracy of a combined Scheimpflug camera-Placido disk device (Sirius, CSO, Italy) in evaluating corneal power changes after myopic photorefractive keratectomy (PRK). METHODS Two hundred and thirty-seven eyes of 237 patients that underwent myopic PRK with a refractive error, measured as spherical equivalent, ranging from -10.75 D to -0.5D (mean -4.63 ± 2.21D), were enrolled in this study. Corneal power evaluation using Sirius were performed before, 1, 3 and 6 months after myopic PRK. Mean simulated keratometry (SimK) and mean pupil power (MPP) were measured. Correlations between changes in corneal power, measured with SimK and MPP, and variations in subjective refraction, calculated at corneal plane, were evaluated using Pearson test at every follow up; differences between preoperative and postoperative data were evaluated with the Student paired t-test. RESULTS A good correlation has been detected between the variations in subjective refraction measured at corneal plane 1, 3 and 6 months after myopic PRK and both SimK (R(2) = 0.8463; R(2) = 0.8643; R(2) = 0.7102, respectively) and MPP (R(2) = 0.6622; R(2) = 0.5561; R(2) = 0.5522, respectively) but corneal power changes are statistically undervalued for both parameters (p < 0.001). CONCLUSIONS Even if our data should be confirmed in further studies, SimK and MPP provided by this new device do not seem to accurately reflect the changes in corneal power after myopic PRK.

Intraocular pressure evaluation in healthy eyes and diseased ones using contact and non contact devices

PURPOSE To analyze and compare intraocular pressure (IOP) values measured in healthy subjects (HS), keratoconus (KC) patients and patients that underwent myopic photorefractive keratectomy (REF), using Goldmann applanation tonometry (GAT), dynamic contour tonometry (DCT), ocular response analyzer (ORA) and Corvis ST (CST). METHODS The study included 76 eyes of 76HS, 15 eyes of 15 KC patients and 18 eyes of 18 subjects that underwent REF. Each participant underwent a complete ophthalmic evaluation, IOP measurement with GAT, DCT, ORA and CST. RESULTS HS showed a mean GAT value of 15.62±2.33 mm Hg, a mean DCT value of 17.44±2.51 mm Hg, a mean ORA value of 15.99±3.58 mm Hg and a mean CST value of 17.24±3.44 mm Hg. KC showed a mean GAT value of 15.07±1.83 mm Hg, a mean DCT value of 17.01±1.96 mm Hg, a mean ORA value of 13.58±2.99 mm Hg and a mean CST value of 14.37±1.89 mm Hg. REF showed a mean GAT value of 14.06±1.51 mm Hg, a mean DCT value of 15.12±2.34 mm Hg, a mean ORA value of 16.85±2.4 mm Hg and a mean CST value of 15.57±1.77 mm Hg. CONCLUSION Our data suggest that ORA and GAT could be used interchangeably in HS; GAT, ORA and CST could be used interchangeably in KC patients and that GAT provides lower IOP values compared to the other devices in eyes previously submitted to myopic PRK.

Corneal Anterior Power Calculation for an IOL in Post-PRK Patients.

Purpose After corneal refractive surgery, there is an overestimation of the corneal power with the devices routinely used to measure it. Therefore, the objective of this study was to determine whether, in patients who underwent photorefractive keratectomy (PRK), it is possible to predict the earlier preoperative anterior corneal power from the postoperative (PO) posterior corneal power. A comparison is made using a formula published by Saiki for laser in situ keratomileusis patients and a new one calculated specifically from PRK patients. Methods The Saiki formula was tested in 98 eyes of 98 patients (47 women) who underwent PRK for myopia or myopic astigmatism. Moreover, anterior and posterior mean keratometry (Km) values from a Scheimpflug camera were measured to obtain a specific regression formula. Results The mean (±SD) preoperative Km was 43.50 (±1.39) diopters (D) (range, 39.25 to 47.05 D). The mean (±SD) Km value calculated with the Saiki formula using the 6 months PO posterior Km was 42.94 (±1.19) D (range, 40.34 to 45.98 D) with a statistically significant difference (p < 0.001). Six months after PRK in our patients, the posterior Km was correlated with the anterior preoperative one by the following regression formula: y = −4.9707x + 12.457 (R2 = 0.7656), where x is PO posterior Km and y is preoperative anterior Km, similar to the one calculated by Saiki. Conclusions Care should be taken in using the Saiki formula to calculate the preoperative Km in patients who underwent PRK.

Corneal Biomechanical Changes After Myopic Photorefractive Keratectomy

Abstract Purpose: To study the corneal biomechanical and morphological changes after photorefractive keratectomy (PRK) and the correlation with morphological parameters. Methods: 119 eyes of 75 subjects with a refraction ranging between −0.50 D and −14.50 D (mean = −4.7 ± 2.3 D) were included in this study. The differences in corneal hysteresis (CH) and corneal resistance factor (CRF) one, three, and six months after PRK have been correlated with effective treatment, central corneal thickness (CCT), and corneal volume (CV) variations at any follow-up utilizing the Pearson Index. Differences between preoperative and postoperative values of the analyzed parameters have been checked with Student T test. Results: Both CH and CRF showed a significant (p < 0.01) decrease at one, three, and six months’ follow-up. Conclusion: Our findings suggest that after myopic PRK there is a significant decrease of CH and CRF immediately after treatment that remains stable over the follow-up.

Corneal confocal microscopy alterations in Sjögren's syndrome dry eye

To evaluate light backscattering (LB) in corneal layers in patients with primary Sjögrens syndrome dry eye (SSDE) utilizing in vivo corneal confocal microscopy (IVCM) and to determine the eventual association with the lacrimal functional test values.