Spherical Refraction Research Articles

Correlation between polymorphisms in the MFN1 gene and myopia in Chinese population.

To explore whether genetic variations in the MFN1 gene are associated with low to moderate myopia in Chinese population. The case-control association analysis was used. The study included 100 independent myopia patients (-0.75 D ≤ spherical refraction ≤-8.00 D) and 100 sex-matched healthy controls (with binocular spherical equivalent ranges between -0.50 D and +0.50 D). Four single nucleotide polymorphism (SNP) tags (rs3976523, rs13098637, rs6762399 and rs7618348) were selected for genotyping by direct sequencing. The frequencies of genotypes and their alleles were calculated based on the number of SNP genotypes in each sample. The Chi-square test was used to examine the difference in the frequency between the myopia cases and controls. Genotype distributions in the four SNPs were all in accordance with the Hardy-Weinberg equilibrium; analysis showed that rs13098637 was significantly associated with low to moderate myopia (P=0.003 and empirical P=0.010). There were no statistically significant differences observed for the genotype or allele frequencies of the other three SNPs between the myopia cases and controls in the Chinese population in this study. The current study has revealed that the C allele of rs13098637 in MFN1 had a significant association with low to moderate myopia.

Evaluation of patient visual comfort and repeatability of refractive values in non-presbyopic healthy eyes.

To evaluate the intra-operator repeatability in healthy subjects using the WAM-5500 auto-kerato/refractometer and the iTrace aberrometer, to compare the refractive values and the subjective refraction obtained with both devices and to determine which of these three spherocylindrical corrections allows the subject to achieve the best visual comfort. Forty-two non-presbyopic healthy eyes of 42 subjects were enrolled in this prospective study. Refractive values were compared, evaluating the repeatability, the relationship between the methods and the best visual comfort obtained. Sphere, cylinder and axis results showed good intraclass correlation coefficients (ICC); the highest ICC was obtained using the spherical refraction with the autorefractometer and the aberrometer, achieving levels of 0.999 and 0.998, respectively. The power vector (PV) was calculated for each refraction method, and the results indicated that there were no statistically significant differences between them (P>0.05). Direct comparison of PV measurements using the three methods showed that aberrometer refraction gave the highest values, followed by the subjective values; the autorefractometer gave the lowest values. The subjective method correction was most frequently chosen as the first selection. Equal values were found for the autorefractometer and the aberrometer as the second selection. The iTrace aberrometer and the WAM-5500 auto-kerato/refractometer showed high levels of repeatability in healthy eyes. Refractive corrections with the aberrometer, the autorefractometer and subjective methods presented similar results, but spherocylindrical subjective correction was the most frequently selected option. These technologies can be used as complements in refractive evaluation, but they should not replace subjective refraction.

Biometric and refractive changes after orbital decompression in Korean patients with thyroid-associated orbitopathy.

To determine the biometric and refractive changes after orbital decompression in Korean patients with thyroid-associated orbitopathy (TAO). Retrospective, observational study (between October 2012 and September 2014) was performed. Patients with TAO undergoing orbital decompression for stable proptosis received ophthalmic examinations, including Hertel exophthalmometry, A-scan biometry, autorefraction measures, corneal topography, and wavefront aberration measures, before orbital decompression and again 2 months after surgery. Included in the study were 43 eyes from 23 patients. The mean exophthalmometric value decreased by 4.1 mm 2 months after orbital decompression (P<0.001). On average, axial length (AL) increased significantly by 0.08 mm (P<0.001); specifically, 37 (86%) of the 43 eyes had increased AL. Whereas anterior chamber depth and lens thickness showed no significant changes (P=0.086 and P=0.905, respectively), the mean spherical refraction and spherical equivalent (SE) decreased by 0.35 and 0.48 D, respectively (P=0.008 and P<0.001, respectively). However, cylindrical refraction and axis showed no significant changes (P=0.057 and P=0.218, respectively). The changes in AL and SE were significantly correlated (R=-0.411, P=0.009). Notably, there were no changes in corneal topography or wavefront aberration after orbital decompression. TAO patients who underwent orbital decompression showed myopic refractive change via increase in AL. Possible refractive changes should be considered in cases of TAO complaining of decreased visual acuity after orbital decompression.

Acute effects of caffeine on choroidal thickness and ocular pulse amplitude

Objective: To explore ocular changes in healthy people after caffeine consumption.Methods: This prospective observational study was carried out with students of the Turgut Özal University Medical Faculty from May 15 to 15 December 2014. Enrolled in the study were 17 healthy subjects (n = 17 eyes), with a median age of 24 (IQR 1), ranging between 21 and 26 years. The control group (6 females, 11 males) aged between 23 and 28 (median 25 years [IQR 4.75]). For study, one eye from each participant was randomly selected. To obviate the effect of diurnal variations, tests were performed at the same time of the day (10:00 a.m.–12:00 p.m.). Each subject was given an ophthalmologic examination before the study to exclude those with undiagnosed ocular disease. Version 6.0 Cirrus high-definition optical coherence tomography (HD-OCT) (Carl Zeiss Meditec, Dublin, CA) was used to measure CT at the fovea, and 1500 μm nasal and 1500 μm temporal to the fovea. After baseline OCT measurements, participants were asked to have 200 mg oral caffeine intake or a placebo capsule (200 mg lactose powder). Two further OCT measurements were applied at the first and fourth hours of caffeine intake. All participants also had intraocular pressure (IOP) and ocular pulse amplitude (OPA) measurements recorded before, first and fourth hours of caffeine intake. IOP and OPA were measured using the dynamic contour tonometry (DCT) (Swiss Micro Technology AG, Port, Switzerland).Results: The groups showed no significant difference by means of age, gender, spherical refraction and axial length (p > 0.05). Baseline choroidal thickness measurements of the study and control group showed no significant difference. Oral caffeine intake caused a significant reduction in choroidal thickness compared with baseline, at all three measurement points, (p < 0.05). There were no significant changes in IOP and OPA measurements compared with the baseline values (p > 0.05). The choroidal thickness still continued to decrease for at least 4 h following caffeine intake; whereas, the difference between 1 and 4 h was not statistically significant (p > 0.05). However, choroidal thicknesses, IOP and OPA values of the control group revealed no significant difference at all points when comparing measurements at baseline with 1 and 4 h after placebo intake (p > 0.05).Conclusions: We found no significant change in IOP and OPA following oral 200 mg caffeine intake, while CT significantly decreased, for at least 4 h.

Management of moderate and severe corneal astigmatism with AcrySof® toric intraocular lens implantation – Our experience

PurposeVisual performance following toric intraocular lens implantation for cataract with moderate and severe astigmatism. SettingCataract services, Shroff Eye Centre, New Delhi, India. DesignCase series. MethodThis prospective study included 64 eyes of 40 patients with more than 1.50 dioptre (D) of pre-existing corneal astigmatism undergoing phacoemulsification with implantation of the AcrySof® toric IntraOcular Lens (IOL). The unaided visual acuity (UCVA), best corrected visual acuity (BCVA), residual refractive sphere and refractive cylinders were evaluated. Toric IOL axis and alignment error was measured by slit lamp method and Adobe Photoshop (version 7) method. Patient satisfaction was evaluated using a satisfaction questionnaire at 3months. ResultsThe mean residual refractive astigmatism was 0.57 D at the final follow-up of 3months. Mean alignment error was 3.44 degrees (SD=2.60) by slit lamp method and 3.88 degrees (SD=2.86) by Photoshop method. Forty-six (71.9%) eyes showed misalignment of 5 degrees or less, and 60 (93.8%) eyes showed misalignment of 10 degrees or less. The mean log MAR UCVA at 1st post-op day was 0.172 (SD=0.02), on 7th post-op day was 0.138 (SD=0.11), and on 30th post-op day was 0.081 (SD=0.11). The mean log MAR BCVA at three months was −0.04 (SD=0.76). ConclusionWe believe that implantation of AcrySof® toric IOL is an effective, safe and predictable method to correct high amounts of corneal astigmatism during cataract surgery.

Comparison of Subjective Refraction under Binocular and Monocular Conditions in Myopic Subjects.

To compare subjective refraction under binocular and monocular conditions, and to investigate the clinical factors affecting the difference in spherical refraction between the two conditions. We examined thirty eyes of 30 healthy subjects. Binocular and monocular refraction without cycloplegia was measured through circular polarizing lenses in both eyes, using the Landolt-C chart of the 3D visual function trainer-ORTe. Stepwise multiple regression analysis was used to assess the relations among several pairs of variables and the difference in spherical refraction in binocular and monocular conditions. Subjective spherical refraction in the monocular condition was significantly more myopic than that in the binocular condition (p < 0.001), whereas no significant differences were seen in subjective cylindrical refraction (p = 0.99). The explanatory variable relevant to the difference in spherical refraction between binocular and monocular conditions was the binocular spherical refraction (p = 0.032, partial regression coefficient B = 0.029) (adjusted R2 = 0.230). No significant correlation was seen with other clinical factors. Subjective spherical refraction in the monocular condition was significantly more myopic than that in the binocular condition. Eyes with higher degrees of myopia are more predisposed to show the large difference in spherical refraction between these two conditions.

Effect of Upper Eyelid Blepharoplasty on Vision and Corneal Tomographic Changes Measured By Pentacam

Purpose: The aim of this study is to determine whether any change occurs in corneal astigmatic values measured by a pentacam and any subjective visual acuity changes occurs following the upper eyelid blepharoplasty.Methods: This is a prospective study; 43 eyes of 23 patients with dermatochalasis underwent pentacam and surveyed for blurred vision before, 1 and 3 months after blepharoplasty surgery. In the course of those 3 measurements, both refractive and keratometric data were recorded and analyzed. The changes in refractive sphere, cylinder and cylindrical axis from both preoperative and postoperative readings were compared statistically.Results: Compared to preoperative measurements, 26 eyes (60%) had a measurable increase in corneal astigmatism after the surgery. Increased astigmatism observed by pentacam in the first and the third month after surgery, showed statistically significant results according to Wilcoxon test with (p = 0.028 < 0.05) and (p = 0.048 < 0.05) values, respectively. The mean change in astigmatism was reported as 0.15D. Regarding the astigmatism axis, no significant change was detected; in the 1 month (p = 0.435 > 0.05) and 3 months (p = 0.560 > 0.05) postoperative measurements compared to preoperative values. Two patients (4.34%) reported visual acuity change 3 months after the surgery.Conclusıon: We discovered statistically significant astigmatic changes; however, these were clinically insignificant visual acuity changes in compatibility with prior studies. Patients undergoing blepharoplasty surgery should be advised that this procedure may potentially alter vision. It is also very important to advise the patients to undergo cataract and/or refractive surgery after having upper eyelid surgery that this procedure may induce vision changes.

Accelerated Corneal Collagen Cross-Linking in Thin Keratoconic Corneas

To report the outcomes of accelerated corneal collagen cross-linking in patients with thin corneas (minimum corneal thickness < 400 µm). Thirty-four eyes of 34 patients with a minimum corneal thickness less than 400 µm were included. All patients underwent accelerated corneal collagen cross-linking (irradiance power of 30 mW/cm² at 3 minutes with a total surface dose of 5.4 J/cm²). Uncorrected (UDVA) and corrected distance visual acuity (CDVA), manifest refraction (diopters [D]), and topography were evaluated at baseline and at the 1-, 6-, and 12-month follow-up visit. Endothelial cell density (cells/mm²) was calculated preoperatively and postoperatively at 12 months. The corneal stromal demarcation line was measured using anterior segment optical coherence tomography at 1 month postoperatively. The mean age of all patients (14 women and 20 men) was 23.08 ± 3.90 years (range: 16 to 29 years). UDVA and CDVA increased but not significantly. UDVA improved from 0.67 ± 0.32 (20/93 ± 20/41 Snellen) to 0.56 ± 0.28 logMAR (20/72 ± 20/38 Snellen) (P = .033) and CDVA improved from 0.49 ± 0.19 (20/61 ± 20/30 Snellen) to 0.42 ± 0.19 logMAR (20/52 ± 20/30 Snellen) (P = .009) at the last follow-up visit. The mean spherical and cylindrical refractions did not significantly change (P = .100 and 0.139, respectively). At the last follow-up visit, the flat keratometry decreased from 47.40 ± 2.52 to 46.95 ± 2.48 D, steep keratometry decreased from 51.04 ± 3.71 to 50.62 ± 3.57 D, and apex keratometry decreased from 57.58 ± 4.49 to 56.26 ± 4.47 D (P = .001, = .0019, = .001, respectively) from baseline. The mean endothelial cell density changed from 2,726.02 ± 230.21 to 2,714.58 ± 218.26 cells/mm² at 12 months postoperatively (P =.086). The results of this study revealed that accelerated corneal collagen cross-linking stabilized the progression of keratoconus without a significant endothelial cell density loss during the 12 months of follow-up.

Can the red-green duochrome test be used prior to correcting the refractive cylinder component?

PurposeA primary task of the eye care professional is determining the refraction, or optical correction, of a patient. The duochrome red-green test is a standard tool for verification of the final refraction. Traditionally, it is recommended for use both prior to and subsequent to determining the cylindrical or astigmatic component of the refraction. In order for it to be effective when used before correcting the cylinder it is necessary that the COLC (Circle of Least Confusion) be on the retina. This study examined whether it is necessarily true that the duochrome response in uncorrected astigmatism will be as trust-worthy as it is with corrected cylinders.MethodsThe red-green examination was performed monocularly under the following three conditions: a. fully corrected refraction for the subgroup of eyes that had spherical refractions and for the subgroup of eyes with sphero-cylindrical refractions. b. best sphere-only correction without cylinder correction in sphero-cylindrical eyes c. an induced cylinder error in spherical eyes. The interval between the last “red” response and the first “green” response for the right eyes as a group and separately for the physiological cylinder and induced cylinder correction sub-groups was calculated and compared using a paired, two-tailed t-test.ResultsThe intervals between “red” and “green” responses were not significantly different in the population as a whole and in the uncorrected physiological cylinder and induced cylinder subgroups examined.ConclusionBased on the finding that the interval of red-green equality with fully corrected cylinder and without the cylindrical correction are not significantly different, the red-green duochrome test can indeed be used both before and after cylindrical correction.

Large-diameter deep anterior lamellar keratoplasty for keratoconus: visual and refractive outcomes.

To investigate the difference in clinical outcomes between large-diameter deep anterior lamellar keratoplasty (L-DALK) and standard DALK (S-DALK) for the treatment of keratoconus. 132 patients (132 eyes) from the Zhongshan Ophthalmic Center with a clinical diagnosis of keratoconus were enrolled. The participants were featured by the intolerance to rigid gas-permeable contact lenses or unsuccessful fitting of contact lenses. Using stratified blocked randomisation, eligible eyes were allocated into the L-DALK group or the S-DALK group (66 eyes, respectively). Postoperative uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refractive sphere, manifest cylinder and spherical equivalent refractive error were tested at 6, 12, 18 and 24 months after surgery. After surgery, the L-DALK group had better UCVA and BSCVA than the S-DALK group (p=0.000 and 0.021, respectively). At 24 months, mean BSCVA was 0.17±0.10 logarithm of the minimum angle of resolution (logMAR) (Snellen equivalent, 20/25) in the L-DALK group vs 0.22±0.10 logMAR (Snellen equivalent, 20/32) in the S-DALK group. Differences were observed between the L-DALK group and the S-DALK group in terms of refractive sphere (p=0.015), manifest cylinder (p=0.014) and spherical equivalent refractive error (p=0.034) at any time interval postoperatively. At 24 months, the mean spherical equivalent refractive error was -3.5±3.2 D and -5.2±2.6 D in the L-DALK and S-DALK groups, respectively. L-DALK can reduce the degree of postoperative myopia and manifest astigmatism and improve visual acuity outcomes in keratoconus compared with S-DALK. Chinese Clinical Trial Registry (TRC-13003122).

Evaluation of 12 Myopia-Associated Genes in Chinese Patients With High Myopia

Two recent large-scale genome-wide association studies identified significant associations between myopia and single nucleotide polymorphisms (SNPs) near the PRSS56, BMP3, KCNQ5, LAMA2, TOX, TJP2, RDH5, ZIC2, RASGRF1, GJD2, RBFOX1, and SHISA6 genes. Our study is to examine whether rare variants in these genes contribute to high myopia. Whole-exome sequencing was performed on samples of 298 probands with early-onset high myopia (eoHM; spherical refraction in each meridian ≤ -6.00 [diopters] D in both eyes; age of onset < 7 years) and 195 controls (different forms of retinal degeneration including Leber congenital amaurosis, cone-rod dystrophy, and familial exudative vitroretinopathy). Potential variations in these genes were selected for further validation and comparison to the controls. Moreover, Sanger sequencing was used to evaluate the coding regions and the upstream 800 bps of GJD2 in 395 additional subjects with late-onset moderate to high myopia (loMHM; spherical refraction in each meridian ≤ -4.00 D; age of onset ≥ 7 years) and 403 healthy controls (-0.50 D ± 1.00 D). Exome sequencing of the 298 probands with eoHM identified 25 rare variants that were predicted to affect coding residues. The segregation analysis and the distribution of rare variants between patients and controls did not provide evidence to support their involvement in myopia. Sanger sequencing of GJD2 in an additional 395 subjects with loMHM and 403 healthy controls did not identify myopia-associated variants. We did not find evidence to support the association of myopia with rare variants in these genes, probably due to our limited sample size. Additional studies are expected to validate these results.

Manual Medium Incision Cataract Surgery with Descemet's Stripping Endothelial Keratoplasty: A Novel Triple Procedure.

Purpose. To describe the surgical technique and outcomes of combined Descemet's stripping endothelial keratoplasty and medium incision manual cataract surgery (MICS) in Chinese eyes. Methods. Surgery was performed in 8 eyes of 7 patients (5 females, 2 males). Primary outcomes included success of the surgery and final outcomes. Results. Surgery was performed in patients with Fuchs' endothelial dystrophy and cataract (mean age 75.5 ± 3.64 years). MICS tunnel was used to insert the donor lenticule into the anterior chamber. All surgeries were performed successfully. Graft dislocation was seen in 1 eye requiring repositioning with intracameral sulfur hexafluoride gas on the first postoperative day. Graft rejection was noted in one patient at the end of one year. The mean decimal best-corrected visual acuity improved from 0.1 ± 0.07 to 0.3 ± 0.15. Suboptimal visual acuity in 2 cases was due to radiotherapy-related optic neuropathy (n = 1) and myopic maculopathy (n = 1). The mean target spherical refraction was −1.11 ± 0.17 diopters (myopic) and the mean achieved spherical refraction was 1.18 ± 0.87 diopters (hyperopic) resulting in a mean hyperopic shift of 2.2 diopters. Conclusions. The approach of combined Descemet's stripping endothelial keratoplasty and MICS is a viable surgical technique for cases with endothelial dysfunction and cataract.

Ocular biometry, mathematical estimation and spherical variation after facectomy

Objective: To assess ocular biometric parameters by optical biometry and to observe a possible spherical refractive difference, as well as its variation based on estimated preoperative calculation and the spherical refraction post cataract surgery by phacoemulsification with intraocular lens implant (IOL). Methods: After reviewing 252 electronic medical records between 2013 and 2014, 117 adult patients (189 eyes) were selected.The patients underwent phacoemulsification with foldable IOL implantation by the same surgeon and were examined by IOLMaster® 500.The IOL power was calculated using the Haigis formula.The Wilcoxon test was applied to identify the existence of significant differences (p<0.05) between the spherical expected refraction (SER) and the final spherical refraction (FSR) of the eyes. Results: There were operated 98 right eyes (OD) and 91 left (OS). A calculation of the variation between FSR and SER indicated that 55% of the OD reached results within ± 0.5 diopters (D) and 89% within ± 1D. With respect to OS, 46% achieved results within ± 0.5D and 78% within ± 1D. Conclusion: Optical biometry is a reliable, predictable and reproducible method to estimate the FSR of both eyes.

Structural and Functional Outcomes in Chronic Central Serous Chorioretinopathy Treated with Photodynamic Therapy.

PurposeTo study the retinal pigment epithelium (RPE) and retinal alterations in chronic central serous chorioretinopathy treated with photodynamic therapy, and its correlation with functional parameters such as best-corrected visual acuity (BCVA) and contrast sensitivity (CS).MethodsRetrospective, noncomparative, consecutive evaluation by optical coherence tomography and its correlation with BCVA and CS in 31 eyes of 26 patients.ResultsIn all affected patients, 88.5% were male with a mean age of 42.9 years. The right eye was involved in 64.5% of cases, bilateral in 19% and 73.9% were hyperopic (spherical refraction between 0 and +5.0 diopters). Of these cases, 51.5% had peri-RPE abnormalities, 17.3% hyperreflective substances at RPE, 19.4% RPE atrophy, 55.3% foveolar atrophy, 3.1% pigment epithelial detachment, 5.2% subretinal fluid persistence, 8.3% fibrin deposits, 68.4% photoreceptor inner and outer segment line interruption and 31.1% external limiting membrane interruption.ConclusionsTime evolution and number of outbreaks were related to the decrease in foveal and chorodial thickness and in those with worse BCVA and CS. RPE abnormalities and atrophy were related to the age of onset of symptoms. Photoreceptor elongation has been correlated with poor BCVA and inner and outer segment line destructuring and interruption with poor CS.

Corneal transplantation in keratoconus: Penetrating keratoplasty versus deep anterior lamellar keratoplasty with Melles technique

ObjectivesTo evaluate the effectiveness of deep anterior lamellar keratoplasty (DALK) using Melles technique (technique B) in patients with advanced keratoconus versus a classic technique, penetrating keratoplasty (technique A). MethodologyRetrospective descriptive comparative study between technique A and technique B in homogeneous groups. ResultsBest corrected visual acuity (Snellen test decimal scale) was 0.77±0.32 for group A and 0.62±0.29 for group B, with no statistically significant differences. The mean spherical final refraction in group A was 1.73±5.1 diopters, and the mean spherical equivalent was −3.92±5.1. Technique B group gave values −2.67±4.02 diopters and −4.55±4.08 diopters, respectively, with no statistically significant differences. The residual cylinder after removal of the sutures was 4.47±2.47 diopters for group A and 3.77±1.63 for group B, with no statistically significant differences. ConclusionNo statistically significant differences were found for any of the studied variables when comparing both groups using the t-test for independent samples. More studies on the homogeneity and residual stromal bed thickness could provide the key to determine whether this technique is closer to the visual acuity of penetrating keratoplasty or DALK by a descemet technique.

Macular Thickness Assessed with Optical Coherence Tomography in Young Chinese Myopic Patients

Purpose. To evaluate the variations in macular thickness in young Chinese myopic persons and the association with axial length (AL), spherical equivalence refraction (SE), age, intraocular pressure, and sex. Methods. In total, 133 young Chinese myopic subjects between 18 and 30 years of age were selected. The macular thickness was assessed using third-generation optical coherence tomography. AL, intraocular pressure, and SE were also measured. Results. The mean central foveal thickness was 191.1 ± 15.3 µm. The macula was consistently thinner in women than in men. Central foveal thickness had a significant positive correlation with AL and a negative correlation with SE. In the inner and outer regions, the macular thickness had a positive correlation with SE and negative correlation with AL. Conclusions. The retina was thinner in women than in men. Associated with myopic progression and AL extension, the central foveal thickness increased, while the retinal thickness of the inner and outer regions decreased.

Angle Kappa Measurements: Normal Values in Healthy Iranian Population Obtained With the Orbscan II.

Background:The angle kappa is important in proper centration of corneal ablation in keratorefractive surgery. Orbscan II device is widely used preoperatively in photoablation surgeries and can be used to measure the angle kappa.Objectives:This study aimed to determine the mean angle kappa and its intercepts in healthy young Iranian adults.Patients and Methods:In this cross-sectional study, orthotropic patients (age range, 18-35 years) who were referred to the Khatam Eye Hospital (Mashhad, Iran) were included. Exclusion criteria were as follows: history of any eye deviation or strabismus with or without orthoptic or surgical treatment; any intraocular, corneal, or keratorefractive surgery; contact lens use; any corneal anomaly; any ophthalmic or systemic drug consumption; and hyperopic spherical refraction > + 3.00 diopters (D), spherical refraction > -5.00 D, or cylindrical refraction > 2.00 D. All of the parameters were measured by the same operator through an Orbscan II device.Results:A total of 977 healthy participants who aged 18 to 45 years were included consecutively. The study population consisted of 614 females and 363 males. The average angle kappa was 5.00º ± 1.36º at 240.21º ± 97.17º in males and 4.97º ± 1.30º at 244.22º ± 94.39º in females (P = 0.63). The average horizontal (x-axis) angle kappa was -0.02º ± 0.49º, with a mean of -0.02º ± 0.50º in males and -0.02º ± 0.49º in females (P = 0.93). The average vertical (y-axis) angle kappa was -0.09º ± 0.32º, with a mean of -0.09º ± 0.33º in males and -0.09º ± 0.32º in females (P = 0.74).Conclusions:By using the normal angle kappa determined in this study, pseudodeviations can be identified more precisely in those who might undergo keratorefractive surgery.

Accelerated corneal cross-linking in pediatric patients with keratoconus: 24-month outcomes.

To compare the efficiency and safety of accelerated corneal cross-linking in pediatric patients with progressive keratoconus. In this retrospective interventional case series, 44 eyes of 38 pediatric patients with progressive keratoconus were enrolled. All consecutive patients underwent accelerated corneal cross-linking with settings of 30 mW/cm(2) for 4 minutes, corresponding to a total dose of 7.2 J. The efficacy and safety of the procedure were assessed over a 24-month follow-up period. Mean ± standard deviation age of 10 girls and 28 boys was 15.3 ± 2.1 years (range: 9 to 18 years). Uncorrected distance visual acuity improved significantly from 0.52 ± 0.36 to 0.39 ± 0.26 logMAR (P = .002), and corrected distance visual acuity improved significantly from 0.38 ± 0.24 to 0.30 ± 0.20 logMAR (P < .001). Mean spherical and cylindrical refraction were not significantly altered (P > .001 for both). At the last follow-up visit, the flat keratometry value decreased from baseline from 46.4 ± 3.0 to 46.0 ± 2.9 diopters and the steep keratometry value decreased from 50.6 ± 4.2 to 50.1 ± 4.0 diopters (P < .001 for both). The total higher-order aberrations, coma, and astigmatism II values were also significantly decreased at 24 months after treatment (P < .05 for all). No serious complications were recorded during the follow-up. The findings revealed that accelerated corneal cross-linking halted the keratoconus progression without relevant side effects in pediatric patients over a 24-month follow-up period. Visual acuity, keratometric values, and corneal aberrations also improved.

Trasplante de córnea en queratocono: queratoplastia penetrante versus queratoplastia lamelar anterior profunda con técnica de Melles

ObjectivesTo evaluate the effectiveness of deep anterior lamellar keratoplasty (DALK) using Melles technique (technique B) in patients with advanced keratoconus versus a classic technique, penetrating keratoplasty (technique A). MethodologyRetrospective descriptive comparative study between technique A and technique B in homogeneous groups. ResultsBest corrected visual acuity (Snellen test decimal scale) was 0.77±0.32 for group A and 0.62±0.29 for group B, with no statistically significant differences. The mean spherical final refraction in group A was 1.73±5.1 diopters, and the mean spherical equivalent was −3.92±5.1. Technique B group gave values -2.67±4.02 diopters and −4.55±4.08 diopters, respectively, with no statistically significant differences. The residual cylinder after removal of the sutures was 4.47±2.47 diopters for group A and 3.77±1.63 for group B, with no statistically significant differences. ConclusionNo statistically significant differences were found for any of the studied variables when comparing both groups using the t -test for independent samples. More studies on the homogeneity and residual stromal bed thickness could provide the key to determine whether this technique is closer to the visual acuity of penetrating keratoplasty or DALK by a descemet technique.

Astigmatism among myopics and its changes from childhood to adult age: a 23-year follow-up study.

To study the prevalence of and changes in astigmatism from the onset of myopia at school age. Two hundred and forty myopic schoolchildren (mean age 10.9 years), with no previous spectacles, were recruited during 1983-1984 to a randomized 3-year clinical trial of bifocal treatment of myopia. Three annual examinations with subjective cycloplegic refraction were performed for 237-238 subjects. Subsequent examinations were performed at the mean ages of 23.2 and 33.9 years for 178 and 163 subjects, and the last examination, including data from prescriptions of different ophthalmologists, for 32 subjects. Corneal topography was studied at baseline, at the 3-year follow-up and at the two adulthood follow-ups. Prevalence and changes in refractive astigmatism (RA), in its polar values J0 and J45, and corneal astigmatism (CA) were studied. Mean RA of the right eye increased during follow-up from 0.26 D (SD) ± 0.30 to 0.79 D ± 0.74. Mean CA was 1.07 D ± 0.74 at study end. The prevalence of RA ≥0.25 or ≥1.00 D increased from 54.9 and 3.8% to 83.4 and 34.4%, respectively. The main direction of the axis of RA and its polar value J0 and CA changed mainly through sphericity, from against the rule (ATR) to with the rule during the follow-up. There was a negative correlation between RA and spherical refraction in the ATR group at end of follow-up. Changes in RA were associated with increase in myopia and with changes in CA. The prevalence and mean amount of RA associated with CA increased, and the axis of astigmatism changed among myopics during the 23-year follow-up.