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Booton GC, Rogerson A, Bonilla TD, Seal DV, Kelly DJ, Beattie TK, Tomlinson A, Lares-Villa F, Fuerst PA, Byers TJ. Molecular and physiological evaluation of subtropical environmental isolates of Acanthamoeba spp., causal agent of Acanthamoeba keratitis. J Eukaryot Microbiol 2004; 51:192-200. [PMID: 15134255 DOI: 10.1111/j.1550-7408.2004.tb00545.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Previous molecular examination of Acanthamoeba spp. has resulted in the determination of distinct genotypes in this genus (designated T1-T12, T14). Genotype T4 has been responsible for the majority of cases of Acanthamoeba keratitis. Here we examine the relative abundance of environmental T4 isolates on beaches and ask whether they have temperature and salinity tolerances that could enhance pathogenicity. Twenty-four Acanthamoeba strains were isolated from beach sand (n = 20), soil (n = 3), and tap water (n = 1) in south Florida. Phylogenetic analysis identified 19 of 24 isolates as T4, the Acanthamoeba keratitis-associated genotype. The remaining isolates were genotype T5 (4) and T11 (1). Nearly all beach isolates were genotype T4, whereas the tap water and soil isolates were mostly T5. All amoebae grew at 0, 1.0, and 2.0% salt and 19 of 20 beach isolates also grew at 3.2%. No soil or tap-water acanthamoebae reproduced at 3.2%. All isolates grew at 37 degrees C and two (T5) at 42 degrees C. Little correlation existed between beach location, salt-tolerance, and genetic relatedness. Overall, the large majority of environmental isolates obtained were genotype T4, suggesting it may be the most common genotype in this environment and could be a potential source of Acanthamoeba keratitis infections.
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Abstract
PURPOSE This study measured evaporation rate, thinning characteristics, and lipid layer changes in the prelens tear film (PLTF) associated with wearing of different soft contact lens materials, in an attempt to determine the biocompatibility of the material with the PLTF. METHODS Twenty habituated contact lens wearers wore five different soft materials in a random order on the left eye at visits separated by at least 24 h. The soft contact lens materials were polymacon (Optima 38), omafilcon A (Proclear Compatibles), phemfilcon A (DuraSoft 2), balafilcon A (PureVision), and etafilcon A (Acuvue). Tear film evaporation rate was measured by a modified Servo Med Evaporimeter and tear thinning time by HirCal grid. Tear film structure, elimination rate, and lens wetting ability were recorded dynamically with a Doane tear film video interferometer and graded according to a new system developed for the study. Baseline measurements were taken of the precorneal tear film before lens insertion, and PLTF was determined 30 min after commencing lens wear. RESULTS No statistically significant differences were found for any of the baseline (precorneal tear film) data. There was also no significant difference in evaporation rate change (analysis of variance) and in tear thinning time (Friedmann) between the five contact lenses. In the PLTF structure grading, omafilcon A had significantly more stable grades than phemfilcon A (Friedmann, p = 0.0033) and polymacon (p = 0.004). In PLTF observation of tear thinning and elimination rate, there was a significantly slower rate of elimination observed for omafilcon A than phemfilcon A (Friedmann, p = 0.0023) and polymacon (p = 0.0023). There was no significant difference in the overall PLTF wetting ability grading between any of the lenses worn. CONCLUSION Generally, all soft contact lens materials significantly and adversely affected tear physiology by increasing the evaporation rate and decreasing tear thinning time. The surface wetting ability of all contact lens materials exhibited no significantly difference irrespective of the special surface treatments. Only in PLTF structure and in PLTF elimination rate were differences found from the conventional low water content materials; omafilcon A was better in PLTF structure and in PLTF elimination.
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Bull L, Sha’Aban J, Tomlinson A, Addison JD, Heydecker BG. Towards Distributed Adaptive Control for Road Traffic Junction Signals using Learning Classifier Systems. APPLICATIONS OF LEARNING CLASSIFIER SYSTEMS 2004. [DOI: 10.1007/978-3-540-39925-4_12] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Tomlinson A, Kyrgiou M, Paraskevaidis E, Kitchener H, Martin-Hirsch P. Does improving communication and information for women increase attendance at colposcopy in an inner city clinic? A randomised controlled trial. EUR J GYNAECOL ONCOL 2004; 25:445-8. [PMID: 15285300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Abstract
PURPOSE To establish whether information leaflets and appointment reminders improve attendance for diagnostic colposcopy. DESIGN & SETTING Randomised controlled trial in an inner city colposcopy clinic. PARTICIPANTS 500 women newly referred to the colposcopy clinic with abnormal cervical screening smear results were randomly assigned to an intervention or control group using computer-generated numbers. INTERVENTION 233 women referred for colpoposcopy were sent a comprehensive information leaflet with their appointment details and additionally were sent reminder letters regarding their appointment 7-10 days prior to their appointment date. CONTROL 267 women were sent the standard basic information prior to their appointment. MAIN OUTCOME MEASURE Attendance and default rates for diagnostic colposcopy. RESULTS Default in the intervention arm was 42 out of 233 (18%) compared with 93 out of 267 (35%) in the control arm. CONCLUSION Improved communication and information in the form of a detailed leaflet and a reminder letter for women with a recently abnormal smear result increased attendance for initial colposcopy assessment.
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Ridder WH, Tomlinson A. The Effect of Artificial Tears on Visual Performance in Normal Subjects Wearing Contact Lenses. Optom Vis Sci 2003; 80:826-31. [PMID: 14688546 DOI: 10.1097/00006324-200312000-00013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE Disruption of the anterior refracting surface of the eye reduces visual performance. In the case of a contact lens wearer, this surface is the prelens tear film. This study determined whether artificial tears stabilize the tear film in contact lens wearers and maintained optimal visual performance for a prolonged period. METHODS Five normal subjects all in good general and ocular health and adapted to contact lens wear were fitted with Acuvue lenses. A temporal, two-alternative, forced-choice paradigm was used to measure contrast sensitivity. The stimuli were vertically oriented sine-wave gratings (between 0.5 and 14 cpd) presented for 16.67 ms. The stimuli were presented at two different times after blink detection: 2 s after blink detection (i.e., before tear layer break-up) or 4 s after tear film break-up. Three conditions were investigated at 4 s after tear layer break-up: (1) without artificial tears added, (2) with Clerz2 (Ciba Vision) instilled, and (3) with Sensitive Eyes (Bausch & Lomb) applied. The artificial tears were instilled at 10-min intervals during the experimental run. RESULTS High spatial frequency contrast sensitivity was found to be reduced after tear film break-up and was not enhanced by either tear solution. CONCLUSIONS This study indicates that there is no effect of Clerz2 or Sensitive Eyes in maintaining or improving visual performance beyond the normal prelens tear film break-up time in normal subjects wearing Acuvue lenses.
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Beattie T, Tomlinson A, Seal D, Grimason A. Attachment of Acanthamoeba to focus night &day silicone hydrogel contact lenses. Trans R Soc Trop Med Hyg 2003. [DOI: 10.1016/s0035-9203(03)80051-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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Beattie TK, Seal DV, Tomlinson A, McFadyen AK, Grimason AM. Determination of amoebicidal activities of multipurpose contact lens solutions by using a most probable number enumeration technique. J Clin Microbiol 2003; 41:2992-3000. [PMID: 12843032 PMCID: PMC165298 DOI: 10.1128/jcm.41.7.2992-3000.2003] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Six multipurpose contact lens solutions [All-in-One, All-in-One (Light), ReNu MultiPlus, Optifree Express, Complete, and Solo-care soft] were tested for their efficacies against Acanthamoeba castellanii trophozoites and cysts by using a most probable number (MPN) technique for amoebic enumeration. Against trophozoites, All-in-One, ReNu Multiplus, and Optifree Express achieved total kill (log reduction of >3) after the manufacturer's minimum recommended disinfection time (MMRDT), with the remaining solutions failing to reach a log reduction of 1. After 24 h of exposure, all solutions proved trophozoiticidal, achieving, with the exception of Complete (log reduction of 3.13), total kill. Against cysts, All-in-One gave a log reduction of >3 within the MMRDT, with all other solutions failing to achieve a log reduction of 1. After 24 h of exposure, All-in-One achieved total kill of cysts (log reduction of 3.74), ReNu MultiPlus gave a log reduction of 3.15, and the remaining solutions reached log reductions of between 1.09 and 2.27. The MPN technique provides a simple, reliable, and reproducible method of amoebic enumeration that depends on simply establishing the presence or absence of growth on culture plates inoculated with a series of dilutions and determining the MPN of amoebae present from statistical tables. By use of this technique, two of the multipurpose solutions tested, ReNu MultiPlus and Optifree Express, demonstrated effective trophozoiticidal activities within the recommended disinfection times; however, only All-in-One proved effective against both trophozoites and cysts over the same time period. This MPN technique, which uses axenically produced trophozoites and mature, double-walled cysts, has the potential to form the basis of a national standard for amoebicidal efficacy testing of multipurpose contact lens disinfecting solutions.
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Craig JP, Tomlinson A, Patterson NS, Reid VEH, McFadyen AK. Tear production measurement, basal or reflex assessment? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003; 506:1159-63. [PMID: 12614045 DOI: 10.1007/978-1-4615-0717-8_163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Tomlinson A, Thai LC, Doane MG, McFadyen A. Reliability of measurements of tear physiology. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003; 506:1097-105. [PMID: 12614036 DOI: 10.1007/978-1-4615-0717-8_154] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/01/2023]
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Pearce EI, Tomlinson A, Blades KJ, Falkenberg HK, Lindsay B, Wilson CG. Effect of an oil and water emulsion on tear evaporation rate. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003; 506:419-23. [PMID: 12613941 DOI: 10.1007/978-1-4615-0717-8_59] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/01/2023]
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Ramnarayan P, Tomlinson A, Rao A, Coren M, Winrow A, Britto J. ISABEL: a web-based differential diagnostic aid for paediatrics: results from an initial performance evaluation. Arch Dis Child 2003; 88:408-13. [PMID: 12716712 PMCID: PMC1719548 DOI: 10.1136/adc.88.5.408] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AIMS To test the clinical accuracy of a web based differential diagnostic tool (ISABEL) for a set of case histories collected during a two stage evaluation. SETTING acute paediatric units in two teaching and two district general hospitals in the southeast of England. MATERIALS sets of summary clinical features from both stages, and the diagnoses expected for these features from stage I (hypothetical cases provided by participating clinicians in August 2000) and final diagnoses for cases in stage II (children presenting to participating acute paediatric units between October and December 2000). MAIN OUTCOME MEASURE presence of the expected or final diagnosis in the ISABEL output list. RESULTS A total of 99 hypothetical cases from stage I and 100 real life cases from stage II were included in the study. Cases from stage II covered a range of paediatric specialties (n = 14) and final diagnoses (n = 55). ISABEL displayed the diagnosis expected by the clinician in 90/99 hypothetical cases (91%). In stage II evaluation, ISABEL displayed the final diagnosis in 83/87 real cases (95%). CONCLUSION ISABEL showed acceptable clinical accuracy in producing the final diagnosis for a variety of real as well as hypothetical case scenarios.
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Beattie TK, Tomlinson A, McFadyen AK, Seal DV, Grimason AM. Enhanced attachment of acanthamoeba to extended-wear silicone hydrogel contact lenses: a new risk factor for infection? Ophthalmology 2003; 110:765-71. [PMID: 12689900 DOI: 10.1016/s0161-6420(02)01971-1] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
PURPOSE To establish if silicone hydrogel (S-H) contact lenses could be a risk factor for Acanthamoeba infection by facilitating the attachment of trophozoites to their surface and transfer to the cornea and to determine the effect Acanthamoeba culture technique, patient wear, and Pseudomonas biofilm coating have on attachment to the S-H lens. DESIGN Experimental material study. PARTICIPANTS AND CONTROLS Attachment to a S-H lens was compared with that of a conventional hydrogel control lens. Sixteen replicates were carried out for both lens types under each test condition. METHODS Unworn S-H (PureVision; Bausch & Lomb, Kingston-Upon-Thames UK) and conventional hydrogel (Acuvue; Vistakon, Johnson & Johnson, Jacksonville, FL USA) lens quarters were incubated for 90 minutes in suspensions of liquid or plate-cultured Acanthamoeba castellanii trophozoites. Unworn, worn, and Pseudomonas biofilm coated S-H and hydrogel quarters were incubated for 90 minutes with plate-cultured trophozoites. MAIN OUTCOME MEASURES Trophozoites attached to one surface of each lens quarter were counted by direct light microscopy. Logarithmic transformation of data allowed the use of a parametric analysis of variance. RESULTS Lens polymer had a significant effect on attachment (P < 0.001), with higher numbers of trophozoites attaching to the S-H lens. Culture technique also had a significant effect on attachment (P = 0.013), with higher numbers of liquid-cultured organisms attaching to both lens types. A significant increase in attachment was demonstrated with worn and Pseudomonas biofilm-coated hydrogel lenses (P < 0.001); however, this difference was not seen with the S-H lens. CONCLUSIONS Acanthamoebal attachment to the S-H lenses was significantly greater than to the conventional hydrogel. Liquid-cultured trophozoites demonstrated a higher affinity for the lenses tested. Wear and bacterial biofilm coating had no effect on attachment to S-H lenses. The increased attachment found with the S-H lens may be an inherent characteristic of the polymer or a side effect of the surface treatment procedure to which the lenses are exposed. It is possible that S-H lenses are at greater risk of promoting Acanthamoeba infection if exposed to the organism because of the enhanced attachment characteristic of this new material.
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Beattie TK, Tomlinson A, Seal DV. Surface treatment or material characteristic: the reason for the high level of Acanthamoeba attachment to silicone hydrogel contact lenses. Eye Contact Lens 2003; 29:S40-3; discussion S57-9, S192-4. [PMID: 12772729 DOI: 10.1097/00140068-200301001-00012] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To determine the reason for the high level of attachment of Acanthamebic to silicone hydrogel (SH) contact lenses. The effect surface treatment has on attachment is determined using silicone elastomer (SE) lenses. METHODS All test lenses were unworn. SH (PureVision), conventional hydrogel (Acuvue), treated SE (Silsoft), and untreated SE (Silsoft) lens quarters were incubated for 90 min with plate-cultured Acanthamoeba castellanii trophozoites. After incubation and rinsing, the trophozoites attached to one surface of each quarter were counted by direct light microscopy. Sixteen replicates were performed for each lens type. Logarithmic transformation of data allowed the use of parametric analysis of variance. RESULTS Lens polymer had a significant effect on attachment (P<0.001), with higher numbers of trophozoites attaching to the SH and SE (treated and untreated) lenses as compared with the conventional hydrogel. No significant difference in attachment was detected between the SH and SE (treated and untreated) lenses. CONCLUSION Acanthamoeba attachment to the SH lens was significantly greater than to the conventional hydrogel. The similarity in attachment to surface-treated and non-surface-treated SE lenses suggests that the increased attachment found with the SH lens may be an inherent characteristic of the polymer rather than an effect of the surface treatment procedure. It is possible that SH lenses are at greater risk of promoting Acanthamoeba infection if exposed to the organism because of the enhanced attachment characteristic of this new material.
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Beattie TK, Tomlinson A, Seal DV. Anti-Acanthamoeba efficacy in contact lens disinfecting systems. Br J Ophthalmol 2002; 86:1319-20. [PMID: 12386105 PMCID: PMC1771370 DOI: 10.1136/bjo.86.11.1319-b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Thai LC, Tomlinson A, Simmons PA. In vitro and in vivo effects of a lubricant in a contact lens solution. Ophthalmic Physiol Opt 2002; 22:319-29. [PMID: 12162483 DOI: 10.1046/j.1475-1313.2002.00042.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE Physical properties and tear film function were investigated for a multipurpose contact lens solution containing the ocular lubricant hydroxypropyl methylcellulose (HPMC). METHODS In the laboratory, wetting properties of multipurpose solutions with and without HPMC, and binding of HPMC to hydrogel lenses in vitro following an overnight soak, were measured. Tear physiology was evaluated in 35 hydrogel contact lens wearers using multipurpose solutions with and without HPMC. Pre-lens tear evaporation rate (TER), tear thinning time (TTT) and tear film structure (TFS) were recorded, and subjective responses were obtained. RESULTS Laboratory measurements indicated improved wetting with the HPMC-containing solution, and continued release of HPMC from lenses after an overnight soak in the solution. Pre-lens TTT was longer (p < 0.001) and pre-lens TFS was improved (p = 0.034) with use of the HPMC-containing solution. Pre-lens TER and subjective comparisons did not demonstrate significant differences. CONCLUSIONS In vitro and in vivo results are consistent with HPMC producing a thicker, longer-lasting layer of fluid on the hydrogel lens, leading to improvements in tear function in contact lens wearers.
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Thai LC, Tomlinson A, Ridder WH. Contact lens drying and visual performance: the vision cycle with contact lenses. Optom Vis Sci 2002; 79:381-8. [PMID: 12086305 DOI: 10.1097/00006324-200206000-00012] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND AND PURPOSE The purpose of this study was to measure the effect of precontact lens tear film break-up on visual performance. METHODS Four asymptomatic soft contact lens wearers had contrast sensitivity measured by a temporal, two-alternative, force choice paradigm combined with a self-paced methods of limits. Stimuli were vertically orientated sine wave gratings (0.5 to 14 cycles per degree [cpd] presented for 16.67 ms. Contrast sensitivity was measured before precontact lens tear break-up by a stimuli presented 2 s after the blink. A post-tear layer break-up measurement taken with the stimuli presented after break-up had been observed by the use of a video camera attached to a Tearscope. RESULTS Contrast sensitivity was found to be reduced following precontact lens tear film break-up for stimuli of 4, 6, and 10 cpd; the data approached significance at 14 cpd. Further reductions in contrast sensitivity were observed for one subject when measurements were continued for 4 s following break-up. CONCLUSIONS Contrast sensitivity is significantly reduced for middle to high spatial frequencies when the precontact lens tear film dries and breaks up. The combination of observations of visual performance immediately following the blink (from earlier experiments) and measurements following tear film break-up in this experiment allows description of a "vision cycle" for contact lens wearers in the interval between blinks. It is suggested that break-up of the precontact lens tear film could account for the complaints of intermittent blurred vision in some contact lens wearers and may provide a stimulus to blinking in these individuals.
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Abstract
In Drosophila, two closely related serpentine receptors, Frizzled (Fz) and D-Frizzled2 (Fz2) are able to act as receptors for the secreted Wnt peptide, Wingless (Wg). In addition to transducing the Wg signal, Fz (but not Fz2) is able to transduce a second, unidentified signal that mediates planar polarity. Much attention has been focused on the structure of the N-termini of the Fz-class receptors and their role in ligand binding. Experiments using techniques of high-level expression have suggested a role for the C-termini in specifying which of the two second messenger systems the receptors are able to activate (M. Boutros, J. Mihaly, T. Bouwmeeste and M. Mlodzik (2000). Science288, 1825-1828). We argue here that experiments involving high level expression of the receptors cannot be adequately interpreted and we have tested the ability of the receptors and chimeric forms when driven at moderate levels to rescue loss of function of the fz and fz2 genes. Under these conditions we find that all receptors tested will function as Wg receptors, but only a subset show the ability to rescue the polarity pathway. The presence of this subset implies that the N terminus is necessary but not sufficient and suggests that the ability to transduce the polarity signal is widely distributed throughout the protein.
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Mills S, Tomlinson A. A reply. Anaesthesia 2001. [DOI: 10.1046/j.1365-2044.2001.02279-21.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Mills S, Tomlinson A. A reply. Anaesthesia 2001. [DOI: 10.1111/j.1365-2044.2001.2279-21.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Oliver KM, O'Brart DP, Stephenson CG, Hemenger RP, Applegate RA, Tomlinson A, Marshall J. Anterior Corneal Optical Aberrations Induced by Photorefractive Keratectomy for Hyperopia. J Refract Surg 2001; 17:406-13. [PMID: 11471997 DOI: 10.3928/1081-597x-20010701-01] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE Photorefractive keratectomy (PRK) for hyperopia requires both a steepening of the central cornea and a flattening of the mid-periphery to achieve its effect and is likely to affect the optical aberrations of the eye. METHODS Nine patients underwent PRK to correct between +2.00 and +4.00 D of hyperopia (first eye treated for each patient) using the Summit Technology Apex Plus excimer laser. Anterior corneal aberrations for pupil diameters of 3, 5.5 and 7 mm were estimated from corneal topography data (TMS-1), assuming a uni-index, single surface cornea. Refractive error was assessed using retinoscopy and standard subjective tests. RESULTS Apart from the intended change in refraction (mean spherical equivalent manifest refraction, +4.60 +/- 1.60 D before surgery and +0.70 +/- 1.60 D at 1 year after surgery), the most significant change was in spherical aberration. Anterior corneal spherical aberration was positive (+1.60 +/- 0.60 D for a 5.5-mm pupil) before surgery and became negative after surgery (-1.80 +/- 1.20 D at 1 year). The change in spherical aberration was related to the achieved change in refractive error. CONCLUSIONS The large change (approximately 3.00 D) in spherical aberration (from positive to negative aberration) has implications for the optical performance of the whole eye, where the effects of lenticular aberration must also be considered.
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