Hyperopic Eyes Research Articles

Comparison of ocular biomechanical response parameters in myopic and hyperopic eyes using dynamic bidirectional applanation analysis

To compare differences in the ocular biomechanical response in myopic and hyperopic eyes. London Vision Clinic, London, United Kingdom, The Ohio State University, Columbus, OH, United States. Retrospective study. The study population included myopic and hyperopic patients evaluated preoperatively for refractive surgery at the London Vision Clinic between June 2006 and May 2008. Biomechanical response parameters from the dynamic bidirectional applanation device (Ocular Response Analyzer) were analyzed using custom software for signal analysis, including corneal hysteresis (CH) and 10 other output parameters. Hyperopic eyes were compared with myopic eyes first matched for age and pachymetry and then matched for age, pachymetry, and corneal-compensated intraocular pressure (IOPcc). Nonpaired t tests were performed (P<.05) to compare parameters in the 2 groups. Consecutive patients included 2608 eyes with 1623 myopic eyes and 787 hyperopic eyes that met enrollment criteria. A significant correlation (P<.0001) was shown between CH and age (negative), pachymetry (positive), and IOPcc (negative). The first match included 473 eyes in each group, and the second match included 260 eyes in each group. When matching for age and pachymetry only, certain parameters implied that hyperopic eyes were stiffer, while others implied that myopic eyes were stiffer, but IOPcc was significantly greater in the myopic group. The second match, which also controlled for IOPcc, showed that all biomechanical parameters implied that hyperopic eyes were stiffer. Hyperopic eyes demonstrated stiffer response parameters than myopic eyes. Intraocular pressure was demonstrated to be a confounding factor when evaluating ocular biomechanical parameters. Proprietary or commercial disclosures are listed after the references.

DETERMINATION OF VALIDITY OF CORNEAL THICKNESS MEASUREMENT BETWEEN ULTRASOUND PACHYMETRY (US), SCHEIMPFLUG IMAGING (PENTACAM, OCULUS) AND SCANNING-SLIT TOPOGRAPHY (ORBSCAN II, BAUSCH & LOMB) IN HYPEROPIC EYES AFTER LASEK SURGERY

Background and Aim: To determine the validity in central corneal thickness (CCT) peripheral corneal thickness (PCT) measured by Scheimpflug imaging (Pentacam, Oculus) and scanning-slit topography (ORBSCAN II, Bausch & Lomb) with that by gold standard method of ultrasound (US) in Hyperopic eyes after LASEK surgery . Materials and Methods: the present study which was based on descriptive and analytic census that carried out in hyperopic patients who undergone LASEK eye surgery in Farabi eye hospital in 2012 and collection of samples lasted for 9 months. The subjects were inspect by ultrasound (US), Scheimpflug imaging ( Pentacam ,Oculus) and scanning-slit topography (ORBSCAN II, Bausch & Lomb) .statistical analysis of collected data was performed using SPSS software version 18 and T-2test method. Results: CT and PCT were evaluated in 28 eyes. CCT measured by Orbscan II had good correlation with those measured by ultrasound pachymetry(r=0.083 and p<0.05) also Orbscan II had good correlation in CCT measurement with Pentacam HR (p<0.05 and r=0.072).PCT measured by Pentacam HR had good correlation with those ultrasound pachymetry readings and there is no considerable discrepancy between two method. Orbscan II had good correlation in superior, inferior and temporal corneal thickness but there was considerable discrepancy in nasal corneal thickness measured by Orbscan II with those of ultrasound pachymetry (sig=0.01, t=-2.74, p<0.05). Conclusion: Pentacam HR and ORBSCAN II showed good correlation with US in CCT measurement but in PCT measurement Pentacam HR had better correlation comparing with ORBSCAN II for hyperopic patient after LASEK refractive surgery Key Words: hyperopia, Pentacam HR, ORBSCAN, LASEK, Ultrasound

Effect of Axial Length on Retinal Nerve Fiber Layer Thickness in Children

To investigate the effect of axial length on peripapillary retinal nerve fiber layer (RNFL) thickness in myopic, hyperopic, and emmetropic eyes in children by Cirrus HD spectral-domain optical coherence tomography (OCT). Subjects were divided into 3 groups according to their refractive status: myopic (n = 36), emmetropic (n = 30), and hyperopic (n = 28) eyes. The RNFL thickness measurements were taken from the superior, inferior, nasal, and temporal quadrants in the peripapillary region by Cirrus HD OCT. Axial length was also determined for each patient. The myopic eyes had thinner average RNFL and RNFLs of temporal, superior, nasal, and inferior quadrants than the hyperopic eyes (p1<0.001, p2 = 0.004, p3 = 0.011, p4 = 0.006, p5 = 0.033, respectively). In addition, average peripapillary RNFL thickness and RNFL thicknesses of all quadrants had significant negative correlations with axial length. On the other hand, after applying modified Littmann formula for correction of magnification effect, the differences among the 3 groups disappeared (all p>0.05). We have shown that axial length and accordingly refractive status influenced peripapillary RNFL thickness measurements by Cirrus HD OCT in children. Therefore, to make a correct diagnosis of glaucoma or other optic neuropathies in children, either axial length-induced magnification effect should be corrected by ophthalmologists or the current Cirrus HD OCT database should be revised taking axial length into consideration.

Comparison of monochromatic aberrations in young adults with different visual acuity and refractive errors

To compare the monochromatic aberrations in a large cohort of 20-year-old Australians with differing levels of visual acuity and explore the relationship between these aberrations and refractive error. Lions Eye Institute, Perth, Western Australia, Australia. Cross-sectional analysis of a population-based cohort. Monochromatic aberrations were measured using a Zywave II wavefront aberrometer with natural pupils in a dark room. The logMAR corrected distance visual acuity (CDVA) was measured monocularly under normal illumination. Cycloplegic autorefraction was also performed. The study enrolled 2039 eyes of 1040 participants. Data from 1007 right eyes were analyzed. The median CDVA and spherical equivalent were -0.06 logMAR (interquartile range [IQR], -0.10 to 0.00) and +0.25 diopters (D) (IQR, -0.38 to 0.63), respectively. The median 6.0 mm higher-order aberration (HOA) was 0.58 μm (IQR, 0.44 to 0.79). Coma-like aberrations and 3rd-, 4th-, and 5th-order HOAs were significantly different between subjects with a CDVA of -0.10 logMAR or better and those with a CDVA worse than -0.10 logMAR. Fourth-order aberrations Z(4,-4) (P=.024) and Z(4,-2) (P=.029) and 2nd-order aberration Z(2,0) (P<.001) differed significantly between myopic eyes, emmetropic eyes, and hyperopic eyes. Subjects with higher myopia had slightly higher total HOAs. The HOAs in this population were marginally higher than previously reported values. The findings confirm there is a difference in monochromatic aberrations between different vision and refractive groups. Results in this study will benefit decision-making processes in the clinical setting.

Ocular Monochromatic Aberrations in a Rural Chinese Adult Population

To investigate the distribution of monochromatic aberrations in a rural Chinese adult population and the possible effect of aberrations on the development of refractive error. A total of 404 Chinese adults who grew up in rural Yongnian County, Handan City, Northern China, were included. Monochromatic aberrations of left eyes were measured using iTrace Dynamic Laser Refraction at 5.0-mm pupil size without cycloplegia. Mean age of all participants was 49.9 ± 10.5 years (range, 31 to 86 years). Mean spherical equivalent was 0.22 ± 1.14 diopters (D) (range, -7.06 to +3.62 D). With age, the refraction demonstrated a significant hyperopic shift (r = 0.25, p < 0.01). Oblique trefoil (C3), vertical coma (C3), horizontal coma (C3), and spherical aberration (SA) (C4) significantly differed from zero (-0.065 ± 0.133 μm, -0.043 ± 0.161 μm, +0.070 ± 0.115 μm, and +0.058 ± 0.082 μm, respectively). Total root mean square values of higher-order aberrations (HOAs) were 0.296 ± 0.147 μm, with predominant ones of coma (0.180 ± 0.115 μm), trefoil (0.151 ± 0.116 μm), and SA (0.081 ± 0.060 μm). Root mean square values of total HOAs, coma, trefoil, SA, and third- to seventh-order aberrations significantly increased with age (p < 0.01). Total HOAs, SA, coma, and trefoil were not significantly different between hyperopic, emmetropic, and myopic eyes after adjusting for age (p = 0.26, 0.15, 0.24, and 0.28, respectively). Zernike coefficient of SA showed a significant difference between hyperopic (0.076 ± 0.086), emmetropic (0.056 ± 0.079), and myopic (0.028 ± 0.088) eyes (p = 0.00). Ocular refraction in rural Chinese adults showed significantly hyperopic shift with age. Magnitudes of HOAs in rural Chinese adults were similar to that of other populations and significantly increased with age but showed no differences in myopic, emmetropic, and hyperopic adults. The existence of HOAs is not, in itself, sufficient to account for the myopia epidemic in China.

Misalignment of a Novel Single-Piece Acrylic Intraocular Lens in the First Three Months after Surgery

Purpose: To evaluate the misalignment of a new single-piece microincisional hydrophobic acrylic intraocular lens (IOL) in emmetropic, myopic and hyperopic eyes within the first 3 months after surgery. Setting: Vienna Institute for Research in Ocular Surgery, Karl Landsteiner Institute, Hanusch Hospital, Department of Ophthalmology, Vienna, Austria. Methods: Patients with age-related cataract were included in this prospective study. Each patient received a single-piece microincisional hydrophobic acrylic IOL (AF-1 NY-60, Hoya) in the study eye. Subgroups of emmetropic, myopic and hyperopic eyes were defined according to IOL power calculation. Anterior chamber depth (ACD) measurements were performed with an AC-Master. Tilt and decentration of the IOL were measured with a Purkinje meter. Follow-up assessments were performed 1 h, 3 weeks and 3 months after surgery. Results: Forty-two eyes of 42 patients (21 emmetropic, 10 myopic and 11 hyperopic eyes) were included. The mean ACD 1 h, 3 weeks and 3 months after surgery was 4.597 ± 0.533, 4.483 ± 0.347 and 4.438 ± 0.398 mm, respectively. Differences in ACD between follow-ups and between subgroups were not statistically significant (both p > 0.05). On average, 3 months after surgery IOLs were tilted 0.81 ± 2.86° nasally and 0.70 ± 3.13° inferiorly and decentered 0.06 ± 0.24 mm nasally and 0.15 ± 0.29 mm superiorly. Differences in tilt and decentration were not statistically significant (both p > 0.05). We observed 1 case of severe capsular fibrosis. Conclusions: The single-piece microincisional hydrophobic acrylic IOL showed good axial stability and only little, clinically not relevant tilt and decentration in the first 3 months after surgery.

Flap characteristics, predictability, and safety of the Ziemer FEMTO LDV femtosecond laser with the disposable suction ring for LASIK

The outcomes of laser-assisted in situ keratomileusis (LASIK) operations performed with the Classic FEMTO LDV femtosecond laser using the plastic single-use suction ring (Ziemer Ophthalmic Systems) and the Allegretto Wave Concerto 500 Hz excimer laser (Wavelight AG) are presented in terms of accuracy, predictability, and safety of the operation. A FEMTO LDV plastic suction ring was used for flap creation in 342 eyes of 179 patients. The intended flap thickness was 90 μm. The size of the suction ring varied from 9.0 to 10.0 mm. Flap dimensions were measured and correlated to preoperative characteristics. Mean flap thickness was very constant, 89.6 ± 2.0 μm (range 84-97). In 163 bilateral operations, the second flap was 1.1 μm thinner than the one cut first (P<0.0001). Mean flap diameter was 9.4 ± 0.2 mm (range 8.1-9.9). Mean hinge length was 3.9 ± 0.2 mm (range 3.0-4.2). In hyperopic eyes, flap thickness correlated negatively with keratometric power K1 and flap diameter. In hyperopic eyes, flap diameter correlated positively with spherical equivalent refraction and with keratometric power K1 as well as hinge length both in myopic and hyperopic eyes. Complications were reported in 12 (3.5%) eyes. Complications were very mild and none of them prevented further refractive laser treatment. Two Snellen lines of corrected distance visual acuity were lost in one (0.3%) eye. The FEMTO LDV plastic single-use suction rings yielded accurate and reproducible flaps and were safe for the creation of thin corneal flaps.

Ciliary Muscle Thickness in Anisometropia

The purpose of this study was to investigate the relationships between ciliary muscle thickness (CMT), refractive error, and axial length both across subjects and between the more and less myopic eyes of adults with anisometropia. Both eyes of 29 adult subjects with at least 1.00 D of anisometropia were measured. Ciliary muscle thickness was measured at the maximum thickness (CMTMAX) and at 1.0 (CMT1), 2.0 (CMT2), and 3.0 mm (CMT3) posterior to the scleral spur, and also at the apical region (Apical CMTMAX = CMTMAX - CMT2, and Apical CMT1 = CMT1 - CMT2). Multilevel regression models were used to determine the relationship between the various CMT measures and cycloplegic refractive error or axial length, and to assess whether there are CMT differences between the more and less myopic eyes of an anisometropic adult. CMTMAX, CMT1, CMT2, and CMT3 were negatively associated with mean refractive error (all p ≤ 0.03), and the strongest association was in the posterior region (CMT2 and CMT3). Apical CMTMAX and Apical CMT1, however, were positively associated with mean refractive error (both p < 0.0001) across subjects. Within a subject, i.e., comparing the two anisometropic eyes, there was no statistically significant difference in CMT in any region. Similar to previous studies, across anisometropic subjects, a thicker posterior region of the ciliary muscle (CMT2 and CMT3) was associated with increased myopic refractive error. Conversely, shorter, more hyperopic eyes tended to have thicker anterior, apical fiber portions of their ciliary muscle (Apical CMTMAX and Apical CMT1). There was no difference between the two eyes for any CMT measurement, indicating that in anisometropia, an eye can grow longer and more myopic than its fellow eye without resulting in an increase in CMT.

GABAergic Agents Modify the Response of Chick Scleral Fibroblasts to Myopic and Hyperopic Eye Cup Tissues

Purpose: GABA antagonists inhibit experimental myopia in chick and GABA receptors have been localized to chick sclera and the retinal pigment epithelium (RPE). The RPE and the choroid alter scleral DNA and glycosaminoglycan (GAG) content in vitro; opposite effects have been observed for tissues from myopic and hyperopic eyes. The aim was to determine the effect of GABAergic agents on the DNA and GAG content of chick scleral fibroblasts directly and in co-culture with ocular tissues from myopic and hyperopic chick eyes.Materials and Methods: Primary cultures of fibroblastic cells expressing vimentin and α-smooth muscle actin were established. GABAergic agents were added separately (i) to the culture medium of the scleral cells and (ii) to the culture medium of the scleral cells with the addition of posterior eye cup tissue (retina, RPE, retina + RPE, choroid + RPE) to cell culture inserts. Ocular tissues were obtained from chick eyes wearing + 15D (lens-induced hyperopia, LIH) or −15D lenses (lens-induced myopia, LIM) for three days (post-hatch day 5–8) (n = 12). GAG and DNA content of scleral fibroblasts were measured.Results: GABA agents had a small direct effect on scleral cell GAG and DNA content but a larger effect was measured when GABA agents were added to the culture medium with myopic and hyperopic RPE and choroid + RPE tissues. GABA agonists increased (p = 0.002) whereas antagonists decreased (p = 0.0004) DNA content of scleral cells; effects were opposite for scleral GAG content. GABA agents significantly altered the effect of both LIM and LIH tissues (p = 0.0005) compared to control; the effects were greater for LIM tissue versus LIH tissue co-culture (p = 0.0004).Conclusion: GABAergic agents affect the DNA and GAG content of scleral fibroblasts both directly and when co-cultured with ocular tissues. GABA antagonists that prevent myopia development in chick model could act via a scleral mechanism utilizing the RPE/choroid.

Influence of Axial Length on Peripapillary Retinal Nerve Fiber Layer Thickness in Children: A Study by RTVue Spectral-Domain Optical Coherence Tomography

Purpose: To evaluate the influence of axial length on peripapillary retinal nerve fiber layer (RNFL) thickness in myopic, hyperopic and emmetropic children eyes by RTVue optical coherence tomography (OCT).Methods: One hundred twenty eyes of 120 children including 40 myopic, 40 emmetropic and 40 hyperopic eyes were enrolled in the study. Peripapillary RNFL thickness measurements were performed using spectral-domain RTVue OCT (Optovue, Fremont, CA). RNFL thickness parameters were obtained from all octametric sections: upper temporal (TU), superotemporal (ST), superonasal (SN), upper nasal (NU), lower nasal (NL), inferonasal (IN), inferotemporal (IT) and lower temporal (TL). Spherical equivalent refractive error was determined via cycloplegic auto-refraction (Topcon, Tokyo, Japan). The axial length was measured using IOLMaster (Carl Zeiss MEDITEC). Littmann formula was used for correction of axial length-related ocular magnification effect.Results: Peripapillary RNFL thicknesses were significantly different among the three groups in all sectors except for NU and IT sectors. RNFL thicknesses in all sectors except for TU and TL sectors had significant negative correlations with axial length. However, these differences (excluding TU and TL sectors) and correlations disappeared after correction of magnification effect.Conclusion: In conclusion, axial length influences peripapillary RNFL thickness as measured by RTVue OCT. However, this appears to be due to the ocular magnification effects associated with axial length and can be corrected for with the application of the Littman formula.

Prevalence of myelinated retinal nerve fibres in adult Indians: the Central India Eye and Medical Study

To determine the prevalence of myelinated retinal nerve fibers in the adult Indian population. The Central India Eye and Medical Study performed in rural Central India included 4711 participants aged 30+ years. The participants underwent a detailed ophthalmic and medical examination. Readable fundus photographs were available for 8645 eyes of 4485 (95.2%) subjects. Myelinated retinal nerve fibers were detected in 52 eyes (46 subjects) with a prevalence rate of 0.58±0.08 per 100 eyes [95% confidence interval (CI): 0.42, 0.74] and 1.03±0.15 per 100 subjects (95%CI: 0.73, 1.32). Prevalence of myelinated retinal nerve fibers was significantly associated hyperopic refractive error (p=0.008; OR: 1.31; 95%CI: 1.07, 1.59). It was not significantly associated with age (p=0.11), best corrected visual acuity (logMAR; p=0.33), intraocular pressure (p=0.09), amount of nuclear cataract (p=0.93), optic disc area (p=0.60), presence of glaucomatous optic nerve atrophy (p=0.62), and early age-related macular degeneration (p=0.53). Myelinated retinal nerve fibers are present in about 10 out of 1000 adult Indians in rural Central India, with a higher prevalence in hyperopic eyes. Prevalence of myelinated retinal nerve fibers was not associated with age, visual acuity, glaucoma and macular degeneration.

The Effect of Procedure Room Temperature and Humidity on LASIK Outcomes

To determine whether procedure room temperature or humidity during LASIK affect refractive outcomes in a large patient sample. Retrospective cohort study. A total of 202 394 eyes of 105 712 patients aged 18 to 75 years who underwent LASIK at an Optical Express, Inc., location in their United Kingdom and Ireland centers from January 1, 2008, to June 30, 2011, who met inclusion criteria. Patient age, gender, flap creation technique, pre- and 1-month post-LASIK manifest refraction, and ambient temperature and humidity during LASIK were recorded. Effect size determination and univariate and multivariate analyses were performed to characterize the relationships between LASIK procedure room temperature and humidity and postoperative refractive outcome. One month post-LASIK manifest refraction. No clinically significant effect of procedure room temperature or humidity was found on LASIK refractive outcomes. When considering all eyes in our population, an increase of 1°C during LASIK was associated with a 0.003 diopter (D) more hyperopic refraction 1 month postoperatively, and an increase in 1% humidity was associated with a 0.0004 more myopic refraction. These effect sizes were the same or similar when considering only myopic eyes, only hyperopic eyes, and subgroups of eyes stratified by age and preoperative refractive error. Neither procedure room temperature nor humidity during LASIK were found to have a clinically significant relationship with postoperative manifest refraction in our population.

Laser in situ keratomileusis in United States Naval aviators

To evaluate the safety and efficacy of femtosecond-assisted wavefront-guided laser in situ keratomileusis (LASIK) as well as higher-order aberrometric changes in a population of active-duty United States Naval aviators. Navy Refractive Surgery Centers, San Diego, California, and Portsmouth, Virginia, USA. Prospective noncomparative 2-site study. In this study of femtosecond-assisted wavefront-guided LASIK, 3 groups were differentiated according to the refractive status: myopia, mixed astigmatism, and hyperopia. Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refraction, mesopic low-contrast CDVA, higher-order aberrations (HOAs), and patient satisfaction were evaluated during a 3-month follow-up. The study enrolled, treated, and included for analysis 548 eyes with myopia, 60 eyes with mixed astigmatism, and 25 eyes with hyperopia. The UDVA was 20/20 or better in 98.3% of eyes with myopia and mixed astigmatism at all postoperative visits and in 95.7% of hyperopic eyes 3 months postoperatively. The gain in CDVA was 1 or more lines in 39.2%, 41.1%, and 30.4% of myopic, mixed astigmatic and hyperopic eyes, respectively. Loss of 2 lines of CDVA after surgery occurred in 2 myopic eyes (0.4%). At 3 months, a mean change of +0.03 μm ± 0.10 (SD) and +0.05 ± 0.08 μm was observed in higher-order root mean square and primary spherical aberration, respectively. Of the patients, 95.9% said they believed that LASIK had helped their effectiveness as Naval aviators and 99.6% would recommend the same treatment to others. Femtosecond-assisted wavefront-guided LASIK was an efficacious and safe option for refractive correction in Naval aviators, enabling a quick return to flight status. Drs. Tanzer and Schallhorn are consultants to Abbott Medical Optics, Inc. No author has a financial or proprietary interest in any material or method mentioned.

Central Versus Thinnest Pachymetry of the Cornea and Thinnest Point Vector Length

To quantify the difference in corneal thickness between the central and thinnest point (ΔCCT-TPCT) and the distance between the center of the cornea and its thinnest point (TPCT vector length) and to explore the impact of ocular side, refractive state, age, and sex. Multicenter, retrospective, cross-sectional study. Medical records of 8054 eyes of 4027 refractive surgery candidates were reviewed. The correlation between ΔCCT-TPCT and TPCT vector length (Pentacam) and the variables refractive state, age, and sex were assessed. Spearman correlations, t tests, analysis of variance, analysis of covariance, and multiple regression models were used. ΔCCT-TPCT was higher in the left eyes of myopic (3.03 ± 2.29 µm) and hyperopic (4.97 ± 3.19 µm) subjects compared with myopic (2.39 ± 2.28 µm) and hyperopic (4.77 ± 3.97 µm; P < 0.05) right eyes. ΔCCT-TPCT was higher in hyperopic than in myopic (P < 0.001) eyes. TPCT vector length was 0.62 ± 0.28 mm for the right eye and 0.69 ± 0.24 mm for the left eye (P < 0.001). TPCT vector length tended to increase with advancing age. Age had the strongest independent effect on TPCT vector length in myopic (η = 0.018; P < 0.001) and hyperopic (η = 0.028; P = 0.006) right eyes. No difference was observed between male and female subjects. The correlations between ΔCCT-TPCT and TPCT vector length were strong (r > 0.8; P < 0.001). As a result of the significant differences found, normative data on ocular side, refractive state, and age should ideally be incorporated into ΔCCT-TPCT and TPCT vector length reference values.

Relative peripheral refraction in children: twelve‐month changes in eyes with different ametropias

To determine the peripheral refraction of children with different types of ametropias and to evaluate the relationship between central refractive changes, baseline relative peripheral refraction (RPR) and changes in RPR over a 12-month monitoring period. Cycloplegic central and peripheral refraction were performed biannually on the right eyes of children aged 6-9 for 12 months, using an open-view autorefractor. Peripheral refraction were measured along 10°, 20° and 30° from central fixation in both nasal and temporal fields. Refractive data were transposed into M, J0 and J45 vectors for analyses. RPR was determined by subtracting the central measurement from each peripheral measurement. Hyperopic eyes showed relative peripheral myopia while myopic eyes had relative hyperopia across the central 60° horizontal field at baseline. Emmetropic eyes had relative myopia within but showed relative hyperopia beyond the central 30° field. However, there was no significant correlation between central refractive changes and baseline RPR or between changes in central refraction and RPR over twelve months in any refractive groups. Correlations between changes in PR and central myopic shift were found mainly in the nasal field in different groups. In the subgroup analysis on the initially emmetropic and the initially myopic groups, the subgroups with faster myopic progression did not have significantly different RPR from the subgroups with slower progression. The RPR pattern of the initially emmetropic and the initially myopic groups became more asymmetric at the end of the study period with a larger increase in relative hyperopia in the temporal field. RPR patterns were different among hyperopic, emmetropic and myopic eyes. However, baseline RPR and changes in RPR cannot predict changes in central refraction over time. Our results did not provide evidence to support the hypothesis of RPR as a causative factor for myopic central refractive changes in children.

The Accuracy of the Double-K Adjustment for Third-Generation Intraocular Lens Calculation Formulas in Previous Keratorefractive Surgery Eyes

To evaluate the effect of the double-K (DK) modification on third-generation formulas. Thirty-eight previously myopic and 24 previously hyperopic eyes that underwent phacoemulsification with intraocular lens (IOL) insertion after Laser in situ keratomileusis (LASIK) were evaluated. Pre-LASIK refraction and keratometry, post-LASIK topography, axial length (AL), IOL type and power, and 1-month postphacoemulsification refraction were recorded spherical equivalent after phacoemulsification (SE(postphaco)). Measured corneal power was adjusted using published and validated methods for postmyopic and posthyperopic LASIK. For each eye, and using SE(postphaco), different DK-IOL formulas were used to calculate the corresponding IOL power, the outcome measure, which was compared with the implanted IOL. DK-Holladay 1 yielded the highest Pearson correlation coefficient (PCC), 0.955 for myopes and 0.943 for high myopes (AL>26 mm). Mean error (ME) and mean absolute error (MAE) for myopes for DK Sanders-Retzlaff-Kraff theoretical formula [DK-SRK/T] were 0.44±0.84 D and 0.75±0.61 D for DK-SRK/T compared with -0.04±0.67 D and 0.52±0.40 D for DK-Holladay 1 (P<0.001 and P=0.016, respectively), and 0.03±0.88 and 0.64±0.58 for DK-Hoffer Q. For high myopes, ME and MAE were 0.75±0.81 D and 0.84±0.69 D for DK-SRK/T, and -0.05±0.74 D (P<0.0001) and 0.57±0.45 D (P=0.019) for DK-Holladay 1. About 29% of DK-SRK/T eyes with large AL had MAE>1.5 D, compared with 0% for DK-Holladay 1 and 14% for DK-Hoffer-Q. Eyes with previous hyperopic LASIK faired similarly for all formulas, with similar PCCs, and only 8% in each category with MAE>1.5 D. DK-SRK/T overestimates IOL power in eyes with large AL, especially with concomitant steep pre-lasik keratometry. Among third-generation formulas, DK-Holladay 1 seems more accurate to use in postmyopic LASIK eyes.

Secondary piggyback implantation versus IOL exchange for symptomatic pseudophakic residual ametropia

To evaluate the safety and efficacy of implanting a secondary IOL in comparison with IOL exchange to correct residual spherical refractive error after cataract surgery. This prospective case series included 23 pseudophakic eyes of 23 patients. They were divided into two groups: group I included 12 eyes for whom secondary piggyback IOL implantation in the ciliary sulcus was done, and group II included 11 eyes for whom IOL exchange was done. The mean follow up was 18 ± 4.2months and 20 ± 3.6months in groups I and II respectively. The visual and refractive outcomes were evaluated, and any intraoperative or postoperative complications was recorded. The mean spherical equivalent in group I (secondary piggyback implantation), was reduced from -6.2 ± 2.2 diopters preoperatively to -0.28 ± 0.59D postoperatively in myopic eyes and from 4.79 ± 1.02D to 0.03 ± 0.74D in hyperopic eyes. Ninety-two percent of eyes were within ±0.5D of intended correction. In group II (IOL exchange), the mean SE was reduced from -5.88 ± 3.1D preoperatively to 0.16 ± 1.09 D postoperatively in myopic eyes and from 5.05 ± 0.93D preoperatively to 0.11 ± 0.69D postoperatively in hyperopic eyes. Eighty-two percent of eyes had postoperative SE within ± 0.5D of the intended correction. UCVA improved significantly in both groups. Rupture of the posterior capsule occurred in one eye in group II. Only one eye in group II lost one line of BCVA. Secondary piggyback implantation in the ciliary sulcus is an effective, safe, and easy treatment for a pseudophakic ametropia.

Anterior segment study with the pentacam scheimpflug camera in refractive surgery candidates

Purpose:The purpose of this study was to evaluate the anterior segment measurements according to refractive status in a sample of the Iranian population.Setting:Rassoul Akram Hospital, Tehran University of Medical Sciences.Material and Methods:In this study, refractive surgery candidates were assigned according to the refractive error to one of three groups : emmetropia, myopia, and hyperopia. Myopic eyes were further divided to four subgroups : simple myopic group, simple myopic astigmatism group, high myopic group, and high myopia with astigmatism group. Anterior segment measurements with the Pentacam Scheimpflug system were performed in the right eye of all subjects.Results:The study sample was comprised of 283 subjects with a mean age of 29.1 ± 7.5 (standard deviation) years. Mean keratometry reading, Anterior chamber depth (ACD) and volume measurements were significantly higher in the myopic group and mean keratometry reading and anterior chamber angle measurements were significantly lower in the hyperopic group (P < 0.05, all comparisons). Maximum anterior elevation (AEmax) and maximum posterior elevation (PEmax), Q value, progression index, minimum corneal thickness, and corneal volume measurements were similar for all groups (P > 0.05, all comparisons). In the myopic subgroups, AEmax and PEmax and maximum keratometry (Kmax) were significantly higher, and ACD was lower in the astigmatic groups (P < 0.05, all comparisons). The Q value was less negative in low myopia (P < 0.05).Conclusions:Myopic eyes had steeper corneas than hyperopic eyes and anterior chamber measurements were significantly higher in the myopic eyes. In myopic eyes, AEmax and PEmax and Kmax measurements were higher, and ACD measurements were lower in the astigmatic groups.

Comparative effects of posterior eye cup tissues from myopic and hyperopic chick eyes on cultured scleral fibroblasts

The role of individual ocular tissues in mediating changes to the sclera during myopia development is unclear. The aim of this study was to examine the effects of retina, RPE and choroidal tissues from myopic and hyperopic chick eyes on the DNA and glycosaminoglycan (GAG) content in cultures of chick scleral fibroblasts. Primary cultures of fibroblastic cells expressing vimentin and α-smooth muscle actin were established in serum-supplemented growth medium from 8-day-old normal chick sclera. The fibroblasts were subsequently co-cultured with posterior eye cup tissue (full thickness containing retina, RPE and choroid) obtained from untreated eyes and eyes wearing translucent diffusers (form-deprivation myopia, FDM) or −15D lenses (lens-induced myopia, LIM) for 3 days (post-hatch day 5–8) (n = 6 per treatment group). The effect of tissues (full thickness and individual retina, RPE, and choroid layers) from −15D (LIM) versus +15D (lens-induced hyperopia, LIH) treated eyes was also determined. Refraction changes in the direction predicted by the visual treatments were confirmed by retinoscopy prior to tissue collection. Glycosaminoglycan (GAG) and DNA content of the scleral fibroblast cultures were measured using GAG and PicoGreen assays. There was no significant difference in the effect of full thickness tissue from either FDM or LIM treated eyes on DNA and GAG content of scleral fibroblasts (DNA 8.9 ± 2.6 μg and 8.4 ± 1.1 μg, p = 0.12; GAG 11.2 ± 0.6 μg and 10.1 ± 1.0 μg, p = 0.34). Retina from LIM eyes did not alter fibroblast DNA or GAG content compared to retina from LIH eyes (DNA 27.2 ± 1.7 μg versus 23.2 ± 1.5 μg, p = 0.21; GAG 28.1 ± 1.7 μg versus. 28.7 ± 1.2 μg, p = 0.46). Similarly, the choroid from LIH and LIM eyes did not produce a differential effect on DNA content (DNA LIM 46.9 ± 6.4 versus LIH 51.5 ± 4.7 μg, p = 0.31). In contrast, scleral fibroblast DNA was greater in co-culture with RPE from LIM eyes than the empty basket and DNA content less for co-culture with RPE from LIH eyes (LIM: 72.4 ± 6.3 μg versus empty basket: 46.03 ± 1.0 μg; p = 0.0005 and LIH: 27.9 ± 2.3 μg versus empty basket: 46.03 ± 1.0 μg; p = 0.0004). GAG content was lower with RPE from LIM eyes (LIM: 27.7 ± 0.9 μg versus empty basket: 29.5 ± 0.8 μg, p = 0.021) and was higher with RPE from LIH eyes (LIH: 33.7 ± 1.9 μg versus empty basket: 29.5 ± 0.8 μg, p = 0.010). Choroid from LIM eyes induce a relative increase in scleral GAG content e.g. (LIM: 32.5 ± 0.7 μg versus empty basket: 29.5 ± 0.8 μg, p = 0.0004) while, choroid from LIH eyes induced a relative decrease in scleral GAG content (LIH: 18.9 ± 1.2 μg versus empty basket: 29.5 ± 0.8 μg, p = 0.0034). GAG content of cells in co-culture with choroid from LIM versus LIH treated eyes was significantly different (32.5 ± 0.7 μg versus 18.9 ± 1.2 μg respectively, p = 0.0002). In conclusion, these experiments provide an evidence for a directional growth signal that is present (and remains) in the ex-vivo RPE/choroid, but that does not remain in the ex-vivo retina. The identity of this factor(s) that can modify scleral cell DNA and GAG content requires further research.

Laser in situ keratomileusis for high astigmatism in myopic and hyperopic eyes

To evaluate outcomes after laser in situ keratomileusis (LASIK) in highly astigmatic myopic and hyperopic eyes. University eye clinic. Retrospective case series. Eyes with more than 2.0 diopters (D) of astigmatism were identified from patient records. The mean preoperative cylinder was -3.92 D ± 0.82 (SD) in myopic eyes and -4.42 ± 1.10 D in hyperopic eyes. Patients were examined preoperatively and 3 months postoperatively. Laser in situ keratomileusis was performed with a Visumax femtosecond laser and a MEL-80 excimer laser. Preoperative and postoperative refractions were converted to polar values. Induced torsion and achieved correction of sphere and cylinder were determined. After 3 months, the mean sphere was 0.48 ± 0.68 D in myopic eyes and the mean cylinder -0.97 ± 0.52 D. Spherical equivalent (SE) correction was 0.05 ± 0.42 D from target. Astigmatism was 0.77 ± 0.62 D undercorrected (P<.01), and the mean induced torsion was -0.18 ± 0.51 D (P=.02). Astigmatic undercorrection was 21% of the intended correction. In hyperopia, the mean 3-month refraction was 0.79 ± 0.83 D in sphere and -1.38 ± 0.90 D in cylinder. The SE refraction was -0.01 ± 0.71 D from target. Astigmatism was 1.17 ± 0.81 D undercorrected (P<.01), with no significant torsion. Intended and achieved astigmatic corrections were correlated, with astigmatism being 28% undercorrected. Laser in situ keratomileusis in highly astigmatic eyes precisely corrected SE refraction but led to astigmatic undercorrection, particularly in hyperopia. Little to no torsion of the cylinder axis was induced.