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PURPOSE: To determine optimal objective, machine-derived variables and variable combinations from Scheimpflug and spectral-domain (SD) OCT imaging to distinguish the clinically unaffected eye in patients with asymmetric keratoconus (AKC) from a normal control population. DESIGN: Retrospective case-control study. PARTICIPANTS: Thirty clinically unaffected eyes with no physical findings on slit-lamp examination, no definitive abnormalities on corneal imaging, and corrected distance acuity of 20/20 or better from 30 patients with highly AKC eyes and 60 eyes from 60 normal control patients who had undergone uneventful LASIK with at least 2 years of stable follow-up (controls). METHODS: Scheimpflug and SD OCT imaging were obtained in all eyes, and receiver operating characteristic (ROC) curves were generated to determine area under the curve (AUC), sensitivity, and specificity for each machine-derived variable and variable combination. MAIN OUTCOME MEASURES: Distinguishing AKC eyes from controls as determined by AUC, sensitivity, and specificity. RESULTS: No individual machine-derived metric from Scheimpflug or SD OCT technology yielded an AUC higher than 0.75. Combining 5 Scheimpflug metrics (index height decentration [IHD], index vertical asymmetry [IVA], pachymetry apex, inferior-superior value, and Ambrosio's Relational Thickness Maximum [ARTmax]) yielded the best Scheimpflug results (AUC 0.86, sensitivity 83%, specificity 83%). Combining 11 SD OCT thickness metrics (minimum-median, temporal outer, superior nasal outer, minimum, epithelium minimum-maximum, epithelial standard deviation, superior inner, superior outer, superior temporal outer, superior nasal inner, central) yielded the best SD OCT results (AUC 0.96, sensitivity 89%, specificity 89%). Combining 13 total Scheimpflug/SD OCT metrics yielded the best results overall (AUC 1.0, sensitivity 100%, specificity 100%). The most impactful variables in combined models included epithelial thickness variability and total focal corneal thickness variability from SD OCT and anterior curvature and topometric indices from Scheimpflug technology. No posterior corneal metrics were impactful in modeling. CONCLUSIONS: Individual machine-derived metrics from Scheimpflug and SD OCT imaging poorly distinguished normal eyes from minimally affected eyes from patients with highly AKC. Combined SD OCT metrics performed better than combined Scheimpflug metrics. Combining anterior curvature and asymmetry indices from Scheimpflug with regional total thickness and epithelial thickness variability metrics from SD OCT clearly distinguished the 2 populations. Posterior corneal indices were not useful in distinguishing populations.
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Córnea/patología , Topografía de la Córnea/métodos , Queratocono/diagnóstico , Tomografía de Coherencia Óptica/métodos , Adolescente , Adulto , Área Bajo la Curva , Estudios de Casos y Controles , Paquimetría Corneal , Femenino , Humanos , Queratocono/cirugía , Queratomileusis por Láser In Situ , Masculino , Persona de Mediana Edad , Curva ROC , Estudios Retrospectivos , Adulto JovenRESUMEN
PURPOSE OF REVIEW: This article describes different strategies for corneal measurements and/or intraocular lens (IOL) calculations and proposes a systematic approach for IOL selection in patients who have undergone laser corneal refractive surgery. RECENT FINDINGS: Corneal measurements and IOL calculations cannot be obtained accurately with the standard measuring technologies and formulas in patients with history of laser corneal refractive surgery; therefore a variety of methods and formulas, some of which required prerefractive surgery data, have been proposed to improve the accuracy of measurements and calculations. Formulas that do not rely on prerefractive data seem to be as accurate as those that do; therefore the lack of prerefractive data no longer presents an obstacle for accurate IOL selection in these patients. SUMMARY: Postrefractive patients undergoing cataract extraction and IOL implantation should have corneal measurements and IOL calculations that take into account and compensate for the limitations in accurate measurements and calculations. IOL selection should also aim to compensate for induced spherical aberration according to the ablation pattern.
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Biometría , Cirugía Laser de Córnea , Lentes Intraoculares , Óptica y Fotónica , Longitud Axial del Ojo/anatomía & histología , Córnea/fisiología , Aberración de Frente de Onda Corneal/fisiopatología , Humanos , Implantación de Lentes IntraocularesRESUMEN
PURPOSE: To evaluate changes in corneal epithelial and stromal thickness after corneal collagen cross-linking (CXL) in eyes with keratoconus and postoperative corneal ectasia using spectral-domain optical coherence tomography (SD-OCT). METHODS: Anterior segment SD-OCT (RTVue-100; Optovue, Inc., Fremont, CA) was used to compare regional corneal epithelial and stromal thickness in eyes with keratoconus and ectasia before CXL and 1 and 3 months after CXL. The anterior surface of the cornea, epithelium-Bowman's layer interface, and posterior reflective surface were used as anatomical landmarks to measure epithelial and stromal thickness, respectively. Regional thickness was assessed centrally and at 21 points 0.5 mm apart across the central 6 mm of the corneal vertex in the horizontal and vertical meridians. RESULTS: Thirty-one eyes from 30 patients were evaluated, including 17 eyes (17 patients) with keratoconus and 14 eyes (13 patients) with ectasia. Preoperatively, a highly irregular epithelial thickness profile and distribution was observed in both groups. After CXL, epithelial thickness was significantly thinner 2.5 and 2 mm below and 1.5 mm above the corneal apex (49.26 ± 5.69 µm; range: 43 to 62 µm), and 2.5 and 1 mm nasal and 2 mm temporal to the corneal apex (46.66 ± 4.53 µm; range: 39 to 57 µm) compared to preoperative values (P < .05 for all measurements). Epithelial thickness standard deviations were significantly lower (by 3 to 6 µm) 3 months after CXL, compared to ranges before CXL in both the vertical and horizontal meridians for keratoconus and ectasia (P = .048). No significant differences were found between epithelial remodeling in keratoconus and corneal ectasia (P = .98). No significant or consistent stromal changes were found for either group. CONCLUSIONS: Significant epithelial remodeling occurs after CXL in eyes with keratoconus and corneal ectasia, creating a similar, more regularized thickness profile in all meridians in the early postoperative period. This pattern of remodeling may facilitate interpretation of corneal curvature and thickness changes after CXL and may be related to visual acuity after CXL.
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Colágeno/metabolismo , Sustancia Propia/fisiología , Reactivos de Enlaces Cruzados/uso terapéutico , Epitelio Corneal/fisiología , Queratocono/tratamiento farmacológico , Tomografía de Coherencia Óptica , Dilatación Patológica/tratamiento farmacológico , Dilatación Patológica/fisiopatología , Humanos , Queratocono/fisiopatología , Fármacos Fotosensibilizantes/uso terapéutico , Estudios Prospectivos , Refracción Ocular/fisiología , Riboflavina/uso terapéutico , Resultado del Tratamiento , Rayos Ultravioleta , Agudeza Visual/fisiologíaRESUMEN
PURPOSE: To assess corneal microarchitecture and regional epithelial thickness profile in eyes with keratoconus, postoperative corneal ectasia (ectasia), and normal unoperated eyes (controls) using spectral-domain optical coherence tomography (SD-OCT). METHODS: Regional corneal epithelial thickness profiles were measured with anterior segment SD-OCT (Optovue RTVue-100, Optovue Inc., Fremont, CA). Epithelial thickness was assessed at 21 points, 0.5 mm apart, across the central 6-mm of the corneal apex in the horizontal and vertical meridians. RESULTS: One hundred twenty eyes were evaluated, including 49 eyes from 29 patients with keratoconus, 32 eyes from 16 patients with ectasia, and 39 eyes from 21 control patients. Average epithelial thickness at the corneal apex was 41.18 ± 6.47 µm (range: 30 to 51 µm) for keratoconus, 46.5 ± 6.72 µm for ectasia (range: 34 to 60 µm), and 50.45 ± 3.92 µm for controls (range: 42 to 55 µm). Apical epithelial thickness was significantly thinner in eyes with keratoconus (P < .0001) and ectasia (P = .0007) than in controls. Epithelial thickness ranges in all other areas varied widely for keratoconus (range: 21 to 101 µm) and ectasia (range: 30 to 82 µm) compared to controls (range: 43 to 64) (P = .0063). CONCLUSION: SD-OCT demonstrated significant central and regional epithelial thickness profile differences between keratoconus, ectasia, and control eyes, with significant variability and unpredictability in ectatic eyes. This regional irregularity may necessitate direct epithelial thickness measurement for treatments where underlying stromal variations may be clinically relevant, including corneal collagen cross-linking or topography-guided ablations.
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Epitelio Corneal/patología , Queratocono/patología , Tomografía de Coherencia Óptica , Paquimetría Corneal , Dilatación Patológica/patología , Células Epiteliales/patología , Epitelio Corneal/anatomía & histología , Humanos , Complicaciones Posoperatorias , Valores de ReferenciaRESUMEN
PURPOSE: To comprehensively review the available published literature for cross-linking in the pediatric population. METHODS: Review of the literature published in English in PubMed. RESULTS: Two hundred ten publications were considered. One hundred fifteen were considered relevant to this review. CONCLUSIONS: Studies of cross-linking in pediatric patients are sparse, with relatively short follow-up times, and mostly on small groups of patients. Treatment with cross-linking halts progression of keratoconus in the pediatric population, and early treatment seems to be cost-effective compared with later penetrating keratoplasty. Long-term effects and regression rates remain unclear, and further studies are needed in this population.
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Reactivos de Enlaces Cruzados/uso terapéutico , Queratocono/tratamiento farmacológico , Fotoquimioterapia/métodos , Fármacos Fotosensibilizantes/uso terapéutico , Riboflavina/uso terapéutico , Niño , Colágeno/metabolismo , Sustancia Propia/metabolismo , Humanos , Rayos UltravioletaRESUMEN
FS-assisted LASIK has become the preferred method for LASIK flap creation due to the precision, accuracy, and reproducibility of the flap creation. Thinner, planar flaps may help prevent cases of post-LASIK ectasia and may have a superior refractive outcome. However, FS flap creation has several unique complications that require early recognition and optimal timely management for the best visual outcomes.
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Complicaciones Intraoperatorias/etiología , Queratomileusis por Láser In Situ/efectos adversos , Complicaciones Posoperatorias/etiología , Enfermedades de la Córnea/etiología , Humanos , Queratomileusis por Láser In Situ/métodos , Láseres de Excímeros/efectos adversos , Trastornos de la Visión/etiologíaRESUMEN
PURPOSE: To compare central, regional and relational corneal thickness values obtained with multiple technologies in normal patients and to determine their equivalence and interchangeability. METHODS: Retrospective analysis of 100 eyes from 50 patients evaluated by ultrasound pachymetry (Pachette II), scanning-slit (Orbscan II), Scheimpflug (Pentacam HR) and spectral-domain ocular coherence tomography (OCT) (RTVue-100) obtained as average values (OCT-A) and point measurements (OCT-P). Measurements included central corneal thickness (CCT) for all technologies and thinnest corneal thickness for scanning-slit, Scheimpflug and OCT. Peripheral thickness measurements were obtained at the 3â mm radius in the superior (S), nasal (N), inferior (I) and temporal (T) regions. RESULTS: CCT values were: 563.9±36.1µ ultrasound, 570.9±36.1µ scanning-slit, 552.8±33.8µ Scheimpflug, 550.5±32.7µ (OCT-A), 549.4±32.7µ (OCT-P). Ultrasound and scanning-slit were significantly different from each other (p<0.0001), and both were significantly different from all other devices (p<0.0001), while Scheimpflug was similar to OCT-A and OCT-P (p=0.4). Differences between CCT and thinnest corneal thickness were significantly different from all technologies except scanning-slit and OCT-A. For peripheral values, almost all locations' measurements were significantly different from one another (p<0.0001). Superior-inferior values and ratios were also significantly different from one another for almost all devices with no consistent patterns detectible. CONCLUSIONS: There are significant clinically relevant differences between regional and relational thickness measurements obtained with ultrasound, scanning-slit, Scheimpflug and OCT devices. Screening metrics devised for one system do not appear directly applicable to other measurement systems.
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Córnea/anatomía & histología , Paquimetría Corneal/métodos , Fotograbar/instrumentación , Tomografía de Coherencia Óptica/instrumentación , Adulto , Córnea/diagnóstico por imagen , Topografía de la Córnea , Femenino , Humanos , Masculino , Persona de Mediana Edad , Reproducibilidad de los Resultados , Estudios Retrospectivos , Tomografía de Coherencia Óptica/métodos , Ultrasonografía , Adulto JovenRESUMEN
OBJECTIVE To estimate and compare the incidence of operable cataract and the desired cataract surgery rates required to eliminate cataract-related visual impairment in several Latin American settings. METHODS We obtained raw data on age-specific cataract prevalence from standardized population-based surveys. We used the data in a previously described model to estimate the incidence of operable cataract at 11 sites in 10 countries across Latin America. Age-specific incidence rates were then multiplied by corresponding population data to calculate the desired cataract surgery rates needed to eliminate cataract-related visual impairment in eyes in each country. Age-standardized incidence was also calculated to explore potential non-age-related differences in incidence among the countries. RESULTS The desired cataract surgery rates ranged from 3441 to 8935 in the 11 sites. Much of the variation was owing to differing age structures, but there may be important variation in age-specific incidence rates as well. CONCLUSIONS Age structure has a major effect on the number of cataract surgeries needed in different countries of Latin America, and it is essential to consider this when planning cataract surgical services. Potential differences in non-age-related risk factors for cataract among different populations also deserve further study.
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PURPOSE: To compare visual acuity and higher-order aberrations (HOAs) after wavefront-guided and wavefront-optimized laser in situ keratomileusis (LASIK). METHODS: This retrospective study comprised refraction-matched myopic eyes that had wavefront-guided (Visx Star S4 laser) or wavefront-optimized (WaveLight Allegretto Wave laser) LASIK targeted for emmetropia. Preoperative and postoperative manifest refraction spherical equivalent (MRSE), uncorrected (UDVA) and corrected (CDVA) distance visual acuities, and preoperative and postoperative HOAs were compared. RESULTS: Preoperatively, there were no significant differences between the wavefront-guided and wavefront-optimized groups in age, sex, corneal thickness, MRSE, or HOAs (all P>.05). The mean MRSE was -2.88 diopters (D) +/- 2.6 (SD) and -2.96 +/- 2.6 D, respectively, preoperatively and -0.01 +/- 0.25 D and -0.02 +/- 0.33 D, respectively, postoperatively; 96% of all eyes were within +/-0.50 D of emmetropia postoperatively. There were no differences in UDVA, CDVA, MRSE, or HOAs between groups (all P>.05). The UDVA was 20/20 or better in 85% of eyes in the wavefront-guided group and 86% of eyes in the wavefront-optimized group. All eyes had 20/25 or better CDVA postoperatively; no eye lost 2 lines of CDVA. Fourteen eyes were converted from wavefront-guided to wavefront-optimized treatment because of poor limbal ring alignment (8 eyes), a wave scan not consistent with the manifest refraction (5 eyes), and no iris registration (1 eye). CONCLUSIONS: Wavefront-guided LASIK and wavefront-optimized LASIK produced equivalent visual outcomes and no differences in HOAs. Wavefront-guided treatment could not be performed in many eyes because of difficulties during wavefront measurement.
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Queratomileusis por Láser In Situ/métodos , Láseres de Excímeros/uso terapéutico , Miopía/cirugía , Agudeza Visual/fisiología , Adolescente , Adulto , Aberración de Frente de Onda Corneal/prevención & control , Femenino , Humanos , Masculino , Persona de Mediana Edad , Refracción Ocular/fisiología , Estudios Retrospectivos , Resultado del Tratamiento , Adulto JovenRESUMEN
PURPOSE: To determine which of 3 methods for measuring preoperative refractive error yields the best refractive outcomes after wavefront-guided (Visx Star S4) or wavefront-optimized (WaveLight Allegretto Wave) excimer laser in situ keratomileusis (LASIK). SETTING: Emory Eye Center and Emory Vision, Emory University, Atlanta, Georgia, USA. METHODS: This retrospective analysis of LASIK, performed from June to December 2007, analyzed sphere, cylinder, and spherical equivalent (SE) refractions generated from 3 methods (manifest refraction, aberrometer autorefraction [CustomVue WaveScan], corneal analyzer autorefraction [Nidek ARK-10000 OPD]), actual programmed treatment, and absolute deviation from ideal treatment (deviation) for each technique. RESULTS: In the wavefront-guided group (63 eyes, 33 patients), manifest refraction and aberrometer autorefraction generated similar deviation for sphere and SE; both were significantly better than corneal analyzer autorefraction (P= .02 and P= .03, respectively). Aberrometer autorefraction generated less cylinder deviation than the other methods (both P= .003). In the wavefront-optimized group (61 eyes, 36 patients), manifest refraction generated less deviation for sphere and SE than aberrometer autorefraction or corneal analyzer autorefraction (sphere: P= .005 and P= .009, respectively; SE: P= .005 and P= .002, respectively). Manifest refraction and aberrometer autorefraction cylinder generated similar deviation, while aberrometer autorefraction was less than corneal analyzer autorefraction (P= .041). CONCLUSIONS: Overall, manifest refraction was most accurate in generating postoperative emmetropia with both laser treatments; however, aberrometer autorefraction produced the least cylinder deviation for wavefront-guided treatment. Corneal analyzer autorefraction produced the least accurate results with both lasers.
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Córnea/fisiopatología , Queratomileusis por Láser In Situ/métodos , Láseres de Excímeros/uso terapéutico , Miopía/fisiopatología , Refracción Ocular/fisiología , Adulto , Córnea/cirugía , Femenino , Humanos , Masculino , Persona de Mediana Edad , Miopía/cirugía , Cuidados Preoperatorios , Estudios Retrospectivos , Colgajos Quirúrgicos , Resultado del Tratamiento , Pruebas de Visión/instrumentación , Agudeza Visual/fisiologíaRESUMEN
PURPOSE: To analyze the changes in higher-order aberrations (HOAs) that occur after wavefront-optimized photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). SETTING: Emory Eye Center and Emory Vision, Atlanta, Georgia, USA. METHODS: This retrospective analysis comprised eyes that had PRK or LASIK from June 2004 through October 2005. Postoperative outcome measures included 3-month uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest refraction spherical equivalent (MRSE), changes in the root mean square (RMS) and grouped coefficient HOAs (microns) measured with a corneal analyzer, and subjective assessment of visual aberrations. RESULTS: One hundred consecutive eyes of 54 patients had PRK, and 100 contemporaneous consecutive eyes of 71 patients had LASIK. The PRK and LASIK populations were similar in general demographics, preoperative HOAs, and postoperative UCVA and BSCVA. The mean MRSE was slightly hyperopic after PRK (mean +0.11 diopters [D]) and slightly myopic after LASIK (mean -0.19 D) (P< .0001). There were no statistically significant changes in RMS or grouped coefficient HOA values after PRK or LASIK, nor were there significant differences in postoperative RMS or grouped coefficient HOA values between PRK and LASIK. One percent of PRK and LASIK patients reported a subjective increase in postoperative visual aberrations; 5% reported a subjective improvement postoperatively. CONCLUSIONS: Wavefront-optimized excimer laser surgery did not induce significant HOAs after PRK or LASIK. The 2 techniques were equally efficacious and had equivalent postoperative HOA profiles.