Central Cone Research Articles

Constraints on the shallow velocity structure of the Lucky Strike Volcano, Mid-Atlantic Ridge, from downward continued multichannel streamer data

The shallow velocity structure of the Lucky Strike segment of the Mid-Atlantic Ridge is investigated using seismic refraction and reflection techniques applied to downward continued multichannel streamer data. We present a three-dimensional velocity model beneath the Lucky Strike Volcano with unprecedented spatial resolutions of a few hundred meters. These new constraints reveal large lateral variations in P wave velocity structure beneath this feature. Throughout the study area, uppermost crustal velocities are significantly lower than those inferred from lower resolution ocean bottom seismometer studies, with the lowest values (1.8–2.2 km/s) found beneath the three central volcanic cones. Within the central volcano, distinct shallow units are mapped that likely represent a systematic process such as burial of older altered surfaces. We infer that the entire upper part of the central volcano is young relative to the underlying median valley floor and that there has been little increase in the layer 2A velocities since emplacement. Layer 2A thins significantly across the axial valley bounding faults likely as the result of footwall uplift. The upper crustal velocities increase with age, on average, at a rate of ~0.875 km/s/Myr, similar to previous measurements at fast-spreading ridges, suggesting hydrothermal sealing of small-scale porosity is progressing at normal to enhanced rates.

The Volcanic Evolution of Cerro Uturuncu: A High-K, Composite Volcano in the Back-Arc of the Central Andes of SW Bolivia

Cerro Uturuncu, southwest Bolivia, is a high-K, calc-alkaline, composite volcano constructed upon extremely thick continental crust approximately 125 km behind the arc-front of the Andean Central Volcanic Zone (CVZ). Eruptive activity occurred between 890 - 271 ka in a single phase of volcanism lasting ~620,000 years. The edifice consists of a central cone and several flank vents where dacitic and andesitic lava flows and domes erupted. Volumes of individual eruptive units range from 0.1 to ~10 km3; the composite volume of Uturuncu is ~89 km3. In this paper, we present new field, petrographic, and geochemical data in an effort to understand the volcanic and magmatic evolution of Uturuncu. Lava flows and domes have a restricted range in whole rock compositions ranging from 61 wt% - 67 wt% SiO2; magmatic inclusions contained within these units have a larger range from 53 wt% - 64 wt% SiO2. Typical phenocryst assemblages are plagioclase > orthopyroxene > biotite >> quartz and Fe-Ti oxides. Pb isotope ratios are characteristic of the southern CVZ by containing high 207Pb/204Pb and 206Pb/204Pb and moderate to high 208Pb/204Pb. Sr and Nd isotope ratios indicate that Uturuncu magmas were modified by high 87Sr/86Sr and low 143Nd/144Nd felsic basement lithology during magma migration and differentiation. In all eruptive units, there is petrographic and geochemical evidence for magma mixing and mingling. In this regard, magma mixing and mingling is considered to be responsible for the small range in lava flow and dome compositions throughout the eruptive history of the center.

Reflection-mode optical-resolution photoacoustic microscopy based on a reflective objective

We developed a new reflection-mode optical-resolution photoacoustic microscopy (OR-PAM) based on the cooperation of a reflective objective and an ultrasonic transducer. The reflective objective is used to produce nearly diffraction-limited optical focusing, and the excited ultrasound waves are then directly detected by an ultrasonic transducer that was placed in the central cone of the objective. This new design avoids the coupling between optical focusing and ultrasound transmission in the reflection mode. Moreover, the proposed system is able to provide lateral resolution of 1.2 μm at 580 nm, penetration depth of 0.9 mm in biological tissues, and a work distance of 6.0 mm. We present in vivo imaging of the microvasculature in mouse ears and in vitro imaging of red blood cells (RBCs), which demonstrate the capability of the system to study microcirculation.

Vertical broad-line region structure in nearby active galactic nuclei

Broad emission lines are emitted in the surroundings of supermassive black holes in the centers of active galactic nuclei (AGN). This region is spatially not resolved. We intend to get information on the structure and geometry of this broad emitting line region (BLR) based on line profile observations. We model the rotational and turbulent velocities in the line-emitting regions based on observed full-width at half maximum line values (FWHM) and {\sigma}_{line} of the variable broad emission lines in four nearby AGN: NGC 3783, NGC 7469, NGC 5548, and 3C 390.3. On the basis of these velocities, we estimate the height of the line-emitting regions above the midplane in context with their distances from the center. The H{\beta} lines are emitted in a more flattened configuration above the midplane in comparison to the highly ionized lines. The H{\beta} lines originate at heights of 0.7 to 1.6 light-days and at distances of 1.4 to 24 light-days with height/distance (H/R) ratios of only 0.07 to 0.5. The highly ionized lines originate at smaller radii than the H{\beta} lines and/or at greater distances above the midplane with H/R values of 0.2 to 1.7. In total, the emission lines do not originate in a thin atmosphere of an accretion disk but rather at very extended regions above an accretion disk. The observed geometries of the line-emitting regions resemble the geometries of accretion disk wind models. Furthermore, the angle of the central opening cone (generated by the emitting regions of the highly ionized lines) is small for those galaxies with slow rotational velocities and increases with the rotation velocity of the central region. The derived geometries of the line-emitting regions of all four AGN are consistent with the geometries that are predicted in outflowing disk wind models.

RP1L1Variants are Associated with a Spectrum of Inherited Retinal Diseases Including Retinitis Pigmentosa and Occult Macular Dystrophy

In one consanguineous family with retinitis pigmentosa (RP), a condition characterized by progressive visual loss due to retinal degeneration, homozygosity mapping, and candidate gene sequencing suggested a novel locus. Exome sequencing identified a homozygous frameshifting mutation, c.601delG, p.Lys203Argfs*28, in RP1L1 encoding RP 1-like1, a photoreceptor-specific protein. A screen of a further 285 unrelated individuals with autosomal recessive RP identified an additional proband, homozygous for a missense variant, c.1637G>C, p.Ser546Thr, in RP1L1. A distinct retinal disorder, occult macular dystrophy (OCMD) solely affects the central retinal cone photoreceptors and has previously been reported to be associated with variants in the same gene. The association between mutations in RP1L1 and the disorder OCMD was explored by screening a cohort of 28 unrelated individuals with the condition; 10 were found to harbor rare (minor allele frequency ≤0.5% in the 1,000 genomes dataset) heterozygous RP1L1 missense variants. Analysis of family members revealed many unaffected relatives harboring the same variant. Linkage analysis excluded the possibility of a recessive mode of inheritance, and sequencing of RP1, a photoreceptor protein that interacts with RP1L1, excluded a digenic mechanism involving this gene. These findings imply an important and diverse role for RP1L1 in human retinal physiology and disease.

Hydraulic design of primary sodium header of a fast spectrum reactor by computational and experimental studies

Computational fluid dynamics (CFD) investigations of flow and pressure distributions in the primary sodium header of fast reactor have been carried out. The focus of the study is to quantify the magnitude of swirl superimposed on main flow and assess its influence on pressure loss in the header and flow mal-distribution among the primary pipes. From compact layout considerations, a spherical shape has been chosen for the header. The static pressure loss coefficient for the basic ‘header-primary pipe’ assembly without any internals is determined to be 7.2. With suitable internal baffles and a central cone this value is reduced to 1.22. The loss coefficients predicted by CFD studies have been validated by conducting experiments on 1:3 scale air models. Following this, an integrated CFD study of header coupled with sodium pump including impeller and diffuser has been carried out. It is seen that the diffuser induces a strong swirl in the fluid entering the header. Due to this swirl, the total pressure loss coefficient in the header-pipe assembly increases by a factor of two, when compared to that without the swirl. The swirl also leads to flow mal-distribution among the two primary pipes to the extent of ±9% from the mean value. This flow mal-distribution is an important input for safety analysis of the reactor for the event of ‘one primary pipe rupture’.

Electromagnetic Super – Compressibility

The dynamic emitter-a nozzle with a disposed along its axis central conic body-is a new engineering decision. The phenomena arising during its work are valuable and prospective both in fundamental science and practical application. During our experiments with this device we have discovered spiral-twisted non-ideal plasma wave structures arising in subsonic and supersonic gas jets flowing from the nozzle with a central cone. We consider very important and prospective the fact that the flow from the dynamic emitter remains almost stable both in shape and power with the distance from the nozzle outlet increasing. For example, the air jet from the nozzle with a central cone can deflect a steel plate of weight 2.55 kg, pending on the 120 mm wire, for about 45 mm at the distance of 400 mm. At this distance the power of the flow from the common conic nozzle is insignificantly low. Also in our experiments we registered phase transitions of air, argon and nitrogen to liquid and solid in the jets at room conditions (temperature of the jet was 285 K, humidity about 5-7%), which is very unusual and provides a lot of practical opportunities. Water vapor flowing from the dynamic emitter creates the mentioned non-ideal plasma structures with increased density of electrons that provides concentration of energy in small volumes (in the nodes of the structure) and high energy radiation (in the experiments there were detected electromagnetic fields up to 1 GHz). The received results can be explained with introducing the concept of electromagnetic super-compressibility which has been the primary aim of our work.

HIGH-FREQUENCY PNEUMATIC LOUDSPEAKER FOR AUDIO BROADCASTING

A high-frequency pneumatic loudspeaker for sound broadcasting is provided, and comprises a housing, silencer exhaust holes, air inlet port, supporting plate, throat canal, central cone, annular nozzle, obstructing ring, and a voice coil and leads. Lower and an upper press plates hold the obstructing ring and the voice coil in position, a magnet having inner and outer magnetic poles is connected therewith, wherein a small gap exists between the obstructing ring and the end of the annular nozzle. This provides the advantages of both air passage area modulation by a sleeve air valve and airstream direction modulation by jet obstruction, reduces airstream consumption, improves air-sound conversion efficiency, and improves structures of an annular air flow-splitter, voice coil and leads. A cooling system is provided to improve high-frequency modulation sensitivity, operation stability, and/or extended fault-free operation time.

Super-Compressibility Phenomenon

Super-compressibility and density jump of high-energy field in gases and in condensed matters are established as source of high density energy field in the nozzle with central cone. The nozzle is resonator and dynamic emitter of the fields in spiraled subsonic and supersonic jets. The values of super-accelerations are estimated as result of internal energy changing and decreasing during adiabatic expansion of the gas. Super accelerations in this field provide high energy radiation in continuous media. These phenomena can serve as basis for creation of new sources of energy.

Outcomes of Corneal Collagen Cross-linking for Keratoconus the Effect of Cone Location

ABSTRACT Aim One-year outcome of corneal collagen cross-linking (CXL) for keratoconus with reference to topographic cone location. Materials and methods Clinical audit of the results of CXL were used. Three hundred and seventy-eight eyes of 225 patients with preoperative and 12-month completed follow-up were included. Cone location was defined by cone location magnitude index (CLMI) using the Keratron scout topography system. The eyes were divided into two groups–central with cone location within 3 mm zone of the topography map and paracentral with cone location between the 3 and 5 mm zones. Results The overall group showed a mean flattening of the CLMI of 1.67 D [preoperative 53.35 ± 5.63 D, 12 months 51.69 ± 4.67 (p = 0.095)]. The flattening in central cone group was 2.67 D [preoperative 54.01 ± 5.3819, at 12 months to 51.341 ± 4.588 (p = 0.016)]. In paracentral cone group the flattening was lesser at 1.73 D [preoperative apex K 52.805 ± 6.382, at 12 months 51.03 ± 4.82 (p = 0.006)]. The difference between groups was statistically significant (p < 0.001). The central cone group showed no significant shift in cone position [preoperative 1.0059 ± 0.24, at 12 months 0.986 ± 0.206 (p = 0.45)]. The paracentral cone group showed a significant mean shift of 1.05 mm in cone location [preoperative 2.224 ± 0.440, at 12 months 1.196 ± 0.529 (p = 0.001)]. Conclusion Cone location has an impact on the results of corneal cross-linking. The paracentral cones show a significant shift toward the center of the cornea and the central cones show a larger flattening. How to cite this article Agrawal V. Outcomes of Corneal Collagen Cross-linking for Keratoconus the Effect of Cone Location. Int J Kerat Ect Cor Dis 2013;2(1):16-19.

Design and Realisation of a Triple Gas Cladding Head for High-power Active Fibre Lasers

This paper addresses the study, design and realisation of a gas cladding head specifically designed for high-power active fibre lasers. The new cladding head has a coaxial architecture and is able to manage three different gases with three different roles in the coaxial cones. From the central cone to the external cone, the roles of the three gases are as follows:-The first gas (inner gas) is used to protect the focusing lens and control the atmosphere of the molten pool in the cladding to protect and change the final cladding proprieties,-The second gas (central gas) is the powder feeder, and-The last gas (outer gas) is used to shield the work area and increase the process efficiency (to avoid wasting the powder).The new laser cladding head is specifically designed to emphasise the active fibre laser characteristics, such as the small divergence of the fibre beam. The new triple gas head was tested in a long experiment in which the cladding of worn dies used in a hot stamping process for automotive components was repaired. The laser source used in the experiment was an IPG Photonics act ive fibre laser (1000-W maximum power, 400-micron delivery fibre). The die was made of H13 steel and had considerable dimensions (approximately 450x300x150 mm3). The worn features of the dies were previously milled, and the cavities were filled via laser cladding with Stellite 21.

Characterizing the Phenotype and Genotype of a Family With Occult Macular Dystrophy

To characterize the phenotype of a white patient with occult macular dystrophy (OMD) and her clinically unaffected family members and to determine whether similar mutations were present in the RP1L1 gene in this family. Occult macular dystrophy is a rare macular dystrophy with central cone dysfunction hidden behind a normal fundus appearance that has been attributed to a mutation in the retinitis pigmentosa 1-like 1 (RP1L1) gene in 4 Japanese families. In this observational cross-sectional study of 1 white family with OMD, patients meeting the clinical criteria for OMD and their family members were evaluated by use of multifocal electroretinography, the Farnsworth D-15 color vision test, automated perimetry, spectral-domain optical coherence tomography (SD-OCT), fundus autofluorescence, and fundus photography. Fluorescein angiography was performed only on the proband. Members of this family were screened for genetic mutations in the RP1L1 gene. In the family studied, the clinically affected proband was noted to have loss of the foveal outer segments and absence of bowing of the inner segment/outer segment junction on SD-OCT scans. In addition, 1 clinically unaffected family member also demonstrated loss of the foveal photoreceptor outer segments and, therefore, decreased bowing of the inner segment/outer segment junction on SD-OCT scans. The fundus autofluorescence images of the eyes of the proband and her family members were normal. Although mutations in the RP1L1 gene have been identified in sporadic and autosomal dominant OMD pedigrees, no mutations in the RP1L1 gene were found in any of the participants. Loss of the outer segments of foveal photoreceptors can be detected and quantified by use of SD-OCT in patients with OMD. Similar findings are present in some clinically unaffected family members and may represent subclinical manifestations of the disease. Although mutations in the RP1L1 gene have been described in several Japanese families with OMD, there were no such mutations in this white family of European descent, which suggests that inherited OMD is a genetically heterogeneous disorder.

Geology, Hydrothermal Activity, and Sea-Floor Massive Sulfide Mineralization at the Rumble II West Mafic Caldera

Abstract Sea-floor imagery, volcanic rock, massive sulfide, and hydrothermal plume samples (δ 3 He, pH, dissolved Fe and Mn, and particulate chemistry) have been collected from the Rumble II West volcano, southern Kermadec arc, New Zealand. Rumble II West is a caldera volcano with an ∼3-km-diameter summit depression bounded by ring faults with a resurgent central cone. Rocks recovered to date are predominantly mafic in composition (i.e., basalt to basaltic andesite) with volumetrically lesser intermediate rocks (i.e., andesite). On the basis of its size, geometry, volcanic products, and composition, Rumble II West can be classified as a mafic caldera volcano. Rumble II West has a weak hydrothermal plume signature characterized by a small but detectable δ 3 He anomaly (25%). Time-series light scattering data though, obtained from vertical casts and tow-yos, do show that hydrothermal activity has increased in intensity between 1999 and 2011. Massive sulfides recovered from the eastern caldera wall and eastern flank of the central cone are primarily comprised of barite and chalcopyrite, with lesser sphalerite, pyrite, and traces of galena. The weak hydrothermal plume signal indicates that the volcano is in a volcanic-hydrothermal quiescent stage compared to other volcanoes along the southern Kermadec arc, although the preponderance of barite with massive sulfide mineralization indicates higher temperature venting in the past. Of the volcanoes along the Kermadec-Tonga arc known to host massive sulfides (i.e., Clark, Rumble II West, Brothers, Monowai, Volcano 19, and Volcano 1), the majority (five out of six) are dominantly mafic in composition and all but one of these mafic volcanoes form moderate-size to large calderas. To date, mafic calderas have been largely ignored as hosts to sea-floor massive sulfide deposits. That 75% of the presently known massive sulfide-bearing calderas along the arc are mafic in composition (the dacitic Brothers volcano is the exception) has important implications for sea-floor massive sulfide mineral exploration in the modern oceans and ancient rock record on land.

Long-Term Decline of Central Cone Function in Retinitis Pigmentosa Evaluated by Focal Electroretinogram

We evaluated long-term changes of central cone-mediated function in retinitis pigmentosa (RP) patients by recording focal electroretinograms (fERG).A cohort of 43 RP patients was followed from 4 to 16 years (average follow-up 9.3 years, average 10 examinations/patient) by recording the fERG response to a flickering uniform red field overlaying the central 18° of visual field (VF). Statistical censoring led to a reduced dataset of 32 patients (autosomal dominant 9, recessive 5, sporadic 5, x-linked 1, Usher II 12), from which long-term decay rates were estimated by global fitting of individual fERG amplitude time-curves.Long-term follow-up of central cone FERG amplitude showed two main features: short-term variability and long-term decline. fERG short-term variability range was 0.14 to 0.2 log units. Mean yearly decay rate of central fERG was 5.6% (95% confidence interval [CI] 4%-7%). Yearly decline depended on inheritance pattern, being significantly greater in autosomal recessive and sporadic compared to autosomal dominant RP. The degree of central cone fERG decline was unrelated to the size of the residual VF.The decline of central cone function is significantly slower than global cone function decline in RP. Central cone fERG loss is independent of residual VF.

RPGR-Associated Retinal Degeneration in Human X-Linked RP and a Murine Model

We investigated the retinal disease due to mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene in human patients and in an Rpgr conditional knockout (cko) mouse model. XLRP patients with RPGR-ORF15 mutations (n = 35, ages at first visit 5-72 years) had clinical examinations, and rod and cone perimetry. Rpgr-cko mice, in which the proximal promoter and first exon were deleted ubiquitously, were back-crossed onto a BALB/c background, and studied with optical coherence tomography and electroretinography (ERG). Retinal histopathology was performed on a subset. Different patterns of rod and cone dysfunction were present in patients. Frequently, there were midperipheral losses with residual rod and cone function in central and peripheral retina. Longitudinal data indicated that central rod loss preceded peripheral rod losses. Central cone-only vision with no peripheral function was a late stage. Less commonly, patients had central rod and cone dysfunction, but preserved, albeit abnormal, midperipheral rod and cone vision. Rpgr-cko mice had progressive retinal degeneration detectable in the first months of life. ERGs indicated relatively equal rod and cone disease. At late stages, there was greater inferior versus superior retinal degeneration. RPGR mutations lead to progressive loss of rod and cone vision, but show different patterns of residual photoreceptor disease expression. Knowledge of the patterns should guide treatment strategies. Rpgr-cko mice had onset of degeneration at relatively young ages and progressive photoreceptor disease. The natural history in this model will permit preclinical proof-of-concept studies to be designed and such studies should advance progress toward human therapy.

A new monozoic tapeworm, Lobulovarium longiovatum n. g., n. sp. (Cestoda: Caryophyllidea), from barbs Puntius spp. (Teleostei: Cyprinidae) in the Indomalayan region

A new caryophyllidean cestode is described from barbs Puntius spp. (Cypriniformes: Cyprinidae), with P. sophore (Hamilton) as its type-host, in the Ganges and Brahmaputra river basins in India and Bangladesh, and a new genus, Lobulovarium n. g., is proposed to accommodate it. The genus belongs to the Lytocestidae because its vitelline follicles are situated in the cortex. It is typified by: (i) a peculiar ovary, which is roughly H-shaped, but with asymmetrical, irregular lobes on its ventral and dorsal sides; (ii) an extensive vitellarium formed by numerous vitelline follicles scattered throughout the cortex; (iii) a long, conical postovarian part of the body with numerous vitelline follicles; (iv) a broadly digitate scolex with a slightly protrusible central cone; (v) a single gonopore (male and female genital ducts open via a single pore and a common genital atrium is absent); and (vi) a small number of testes (< 60). Molecular data (partial sequences of the lsrDNA) indicate that Lobulovarium longiovatum n. sp. belongs among the most basal caryophyllidean cestodes, being unrelated to species from siluriform catfishes in the Indomalayan region. Paracaryophyllaeus osteobramensis (Gupta & Sinha, 1984) Hafeezullah, 1993 (syn. Pliovitellaria osteobramensis Gupta & Sinha, 1984) from another cyprinid fish, Osteobrama cotio (Hamilton), in Uttar Pradesh, India, is tentatively transferred to Lobulovarium as L. osteobramense (Gupta & Sinha, 1984) n. comb. It differs from L. longiovatum by having much smaller eggs (length <50 μm versus >90 μm in L. longiovatum), which are spherical (length/width ratio 1:1 versus 2.5-3:1 in the new species), and the presence of vitelline follicles alongside the ovarian lobes (almost completely absent in L. longiovatum).

Design and Construction of Fly Ash Silo with Inverted Cone

A coal and biomass power plant was built at Maasvlakte near Rotterdam in the Netherlands. For the storage of fly ash which is a residual product of the coal combustion process, a 24 m diameter reinforced and prestressed concrete silo having a height of 65 m was designed. The silo has a central inverted cone composed of precast concrete elements which forces the fly ash to be discharged from eight openings around the perimeter of the silo. This paper presents the process of designing the foundation, the cylinder wall and the central cone and discusses the engineering challenges. It deals with the characterization of the load cases resulting from filling and discharging the silo, and explains the way thermal loads resulting from the high-temperature fly ash were allowed for in the analysis of the structure. Finally, it summarizes the main issues regarding the construction of the silo structure.

Magnetic fields and gas flows around circumnuclear starbursts

Radio continuum observations of barred galaxies revealed strong magnetic fields of ≥ 50 – 100μG in the circumnuclear starbursts. Such fields are dynamically important and give rise to magnetic stress that causes inflow of gas towards the center at a rate of several solar masses per year, possibly along the spiral field seen in radio polarization and as optical dust lanes. This may solve the long-standing question of how to feed active nuclei, and explain the relation between the bolometric luminosity of AGN nuclei and the star-formation rate of their hosts. The strong magnetic fields generated in young galaxies may serve as the link between star formation and accretion onto supermassive black holes. – Magnetic fields of ≥ 160 μG strength were measured in the central region of the almost edge-on starburst galaxy NGC 253. Four filaments emerging from the inner disk delineate the boundaries of the central outflow cone of hot gas. Strong Faraday rotation of the polarized emission from the background disk indicates a large-scale helical field in the outflow walls.

Comparison of visual and refractive outcomes following Intacs implantation in keratoconus eyes with central and eccentric cones

ObjectiveTo compare visual and refractive outcomes after Intacs implantation in keratoconus eyes with central and eccentric cones and to validate the current nomogram used to select Intacs size. DesignComparative study. ParticipantsThe charts of 20 patients in a single practice, who had symmetric (15 eyes) or asymmetric (16 eyes) implants, were retrospectively reviewed. MethodsIntacs were implanted by a single surgeon using a femtosecond laser. Based on Scheimpflug imaging, central and eccentric cone patterns received symmetric and asymmetric Intacs, respectively. Uncorrected distance visual acuity (UDVA) and best-corrected distance visual acuity (CDVA), manifest refraction spherical equivalent (MRSE), and keratometry (K) values were measured pre- and postoperatively. ResultsThe mean improvement in UDVA and CDVA in the symmetric group was 3.8 ± 0.9 and 0.6 ± 0.5 lines, and in the asymmetric group was 3.4 ± 0.7 and 1.8 ± 0.3 lines, respectively. The mean change in manifest refraction spherical equivalent (MRSE), refractive cylinder, and average K in the symmetric group was 2.40 ± 0.71 D, 0.02 ± 0.90 D, and −2.71 ± 0.50 D, and in the asymmetric group was 2.67 ± 1.21 D, 0.05 ± 0.47 D, and −2.35 ± 0.40 D, respectively. In CDVA, asymmetric Intacs showed statistically significant and better results than symmetric Intacs (p = 0.0016). There was no statistically significant difference between the means of symmetric and asymmetric implantation for UDVA, MRSE, average K, or corneal astigmatism (p > 0.05). ConclusionsThe implantation of symmetric and asymmetric Intacs segments in keratoconus eyes with central and eccentric cones, respectively, was found to have comparable visual and refractive outcomes except for CDVA, which improved significantly more in the asymmetric group. This study also demonstrates the validity of the nomogram used.

Phototherapeutic keratectomy versus mechanical epithelial removal followed by corneal collagen crosslinking for keratoconus

ObjectiveTo compare the visual outcomes of patients with keratoconus treated with either phototherapeutic keratectomy (PTK) or mechanical epithelial removal prior to corneal collagen crosslinking (CXL). DesignComparative study. ParticipantsThe records of 34 patients (34 eyes) who had PTK (17 eyes) or mechanical (17 eyes) epithelial removal prior to CXL for keratoconus were reviewed retrospectively. MethodsCXL was performed by 1 of 3 surgeons (G.M., W.B.J., or K.B.). Of the eyes, 17 had undergone mechanical epithelial removal prior to CXL and were consecutively selected, after matching with the 17 eyes in the PTK group, for the variables of procedure date, average keratometry, and pachymetry. All eyes had central cones. Manifest refraction spherical equivalent, sphere, cylinder, best-corrected distance visual acuity, and pachymetry were measured and compared preoperatively and in follow-up. ResultsThe mean change between the pre- and postoperative manifest refraction spherical equivalent for the PTK and mechanical groups was 1.68 ± 0.80 and 0.26 ± 0.90, respectively (p < 0.05). The mean change between pre- and postoperative cylinder for the PTK and mechanical groups was 0.53 ± 0.28 and 0 ± 0.18, respectively (p < 0.05). The mean number of lines of improvement in the PTK and mechanical groups were 0.33 ± 0.82 and −0.58 ± 0.45 lines, respectively (p > 0.05). ConclusionsEarly results suggest that CXL with laser epithelial removal is superior to CXL with mechanical epithelial removal because it reduces refractive error in qualified patients. Although not statistically significant, there was also a trend for PTK CXL patients to have better visual outcomes.