Unexpectedly high corneal flap thickness and ectasia after mechanical LASIK / Espessura inesperadamente alta do flap corneano e ectasia após LASIK mecânico

ABSTRACT LASIK is a refractive surgical procedure in which a corneal flap is created to expose the corneal stromal bed. Preoperative estimation of corneal flap thickness is necessary to calculate the percentage tissue altered in LASIK, an important quantitative risk factor for ectasia. The objective of this study was to assess flap thickness and calculate percentage tissue altered to check if unexpectedly thicker flaps and higher percentage tissue altered could pose as risk factors of ectasia. Four subjects (eight eyes) were submitted to mechanical LASIK in 2009 and 2010. Pre and postoperative clinical and tomographic data were reviewed. Mean preoperative estimated percentage tissue altered was 39.18±1.31%, which was borderline for increased ectasia risk when considering the limit of 40%. However, when considering the postoperatively measured flap thickness, the actual mean percentage tissue altered turned out to be 45.17 ± 4.13%, which was significantly higher than predicted preoperatively (p=0.002). Unexpectedly higher postoperative percentage tissue altered may be responsible for corneal ectasia after mechanical LASIK.

RESUMO A LASIK é um procedimento cirúrgico refrativo, no qual um retalho corneano é criado para expor o leito estromal corneano. A estimativa pré-operatória da espessura do retalho corneano é necessária para calcular o percentual de tecido alterado no LASIK, um importante fator de risco quantitativo para ectasia. O objetivo deste estudo foi avaliar a espessura do retalho e calcular o percentual de tecido alterado para verificar se retalhos inesperadamente mais espessos e percentuais de tecido alterado mais altos poderiam representar fatores de risco de ectasia. Quatro indivíduos (oito olhos) foram submetidos à LASIK mecânica em 2009 e 2010. Dados clínicos e tomográficos pré e pós-operatórios foram revisados. A média de percentual de tecido alterado pré-operatória estimada foi de 39,18±1,31%, limítrofe para risco aumentado de ectasia quando considerado o limite de 40%. No entanto, ao considerar a espessura do retalho medida no pós-operatório, o percentual de tecido alterado médio real foi de 45,17±4,13%, ou seja, significativamente maior do que o previsto no pré-operatório (p=0,002). O percentual de tecido alterado pós-operatóriao inesperadamente mais alto pode ser responsável pela ectasia da córnea após LASIK mecânico.

Corneal Collagen Crosslinking (CXL) for Corneal Ectasia after Small Incision Lenticule Extraction (SMILE). / Korneales Kollagen-Crosslinking (CXL) bei Hornhautektasie nach SMILE (Small Incision Lenticule Extraction).

With an estimated incidence of 0.011%, the SMILE procedure seems to have the lowest risk of postoperative keratectasia among contemporary keratorefractive procedures. Nevertheless, due to the novelty of the procedure as well as the lack of data, no clear superiority over femto-LASIK or PRK can be stated at this time. In this respect, application of the identical tomographic screening criteria previously developed for excimer-based procedures is of paramount importance to minimize the risk of corneal ectasia. As an adjunct to conventional corneal tomography, newer imaging modalities such as OCT-based epithelial mapping should be used for preoperative screening before keratorefractive surgery. Corneal crosslinking is an established treatment modality for post-SMILE keratectasia, which promises high success rates especially in early stages. The present case report illustrates these diagnostic and therapeutic considerations.

Changes in Retinal Vessel Flow after Small Incision Lenticule Extraction.

Objective: In order to analyze changes in retinal vessel flow after small incision lenticule extraction (SMILE). Methods: A total of 32 patients (62 eyes) who underwent SMILE were enrolled in this prospective study. Optical parameters, including vessel density (VD), and perfusion density (PD) of foveal, parafoveal, and perifoveal regions, respectively, were measured before surgery and at 1 day, 1 week, 1 month, and 3 months postoperation. Preoperative parameters and surgical parameters were recorded. Results: Significant decreases in VD and PD on postoperative day 1 were detected in all quadrants, both in 3 mm and in 6 mm regions (P < 0.001). One month after surgery, VD returned to preoperative levels. None of the preoperative and surgical parameters were significantly correlated with the VD and PD fluctuations (all P > 0.05). Conclusion. VD may decrease significantly with regional disparity 1 day after SMILE while recovering at 1 month. Elevation of intraocular pressure due to suction may account for such changes.

Alteraciones estructurales y funcionales en pacientes con ambliopía / Structural and Functional Alterations in Patients with Amblyopia

Objetivo: Determinar los resultados motores post cirugía refractiva corneal con láser de excímero en pacientes miopes con o sin astigmatismo asociado. Método: Se realizó un estudio preexperimental del tipo antes y después, en el que fueron incluidos 81 pacientes (162 ojos) tratados con LASEK-MMC (65 pacientes) o PRK-MMC (16 pacientes) seguidos por tres meses. Se les realizó un examen oftalmológico completo y se evaluaron las siguientes variables: punto próximo de convergencia, la amplitud de convergencia, divergencia y el alineamiento ocular precirugía y poscirugía. Resultados: Con la cirugía se observó un incremento significativo del punto próximo de convergencia (LASEK-MMC: p = 0,000 y PRK-MMC: p = 0,021). La amplitud de convergencia de cerca y de lejos, así como la amplitud de divergencia tendieron a disminuir, pero la diferencia no fue significativa (p > 0,05). Aumentó el porcentaje de pacientes con exodesviaciones de cerca, después de la cirugía LASEK-MMC (26,2 por ciento → 60,0 por ciento, p = 0,000) y de la PRK-MMC (18,8 por ciento → 81,3 por ciento, p = 0,000), y predominaron las heteroforias pequeñas en ambos casos (LASEK-MMC: 52,3 por ciento y PRK-MMC: 75,0 por ciento). Conclusiones: Con la cirugía fotoablativa con láser, aumentaron las exodesviaciones en el posoperatorio, pero se trató fundamentalmente de heteroforias pequeñas, aunque un número reducido de pacientes desarrolló nuevas exodesviaciones(AU)

Objective: To determine the motor results after corneal refractive surgery with excimer laser in myopic patients with or without associated astigmatism. Method: A pre-experimental study of the before and after type was carried out, in 81 patients (162 eyes) treated with LASEK-MMC (65 patients) or PRK-MMC (16 patients) followed up for three months. A complete ophthalmological examination was performed and the variables were evaluated near point of convergence, amplitude of convergence, divergence, and pre-surgery and postsurgery ocular alignment. Results: A significant increase in the near point of convergence was observed with surgery (LASEK-MMC: p = 0.000 and PRK-MMC: p = 0.021). The amplitude of convergence near and far, as well as the amplitude of divergence tended to decrease, but the difference was not significant (p > 0.05). The percentage of patients with near exodeviations increased after LASEK-MMC surgery (26.2 percent → 60.0 percent, p = 0.000) and PRK-MMC (18.8 percent → 81.3 percent, p = 0.000), and small heterophoria predominated in both cases (LASEK-MMC: 52.3 percent and PRK-MMC: 75.0 percent). Conclusions: The laser photoablative surgery increased postoperative exodeviations, but they were mainly small heterophoria, although a small number of patients developed new exodeviations(AU)

Assessment of the correlation of the tear breakup time with quality of vision and dry eye symptoms after SMILE surgery.

PURPOSE: It is well reported that dry eye symptoms can increase after many refractive surgery procedures. This study aims to provide a clinical understanding of the correlation of fluorescein tear film breakup time (FTBUT) with quality of vision (QoV) and dry eye symptoms following small incision lenticule extraction surgery (SMILE). METHODS: Patients electing to have SMILE surgery were subdivided into 2 groups: Group 1 included short preoperative FTBUTs of 3 to 6 seconds (s); Group 2 included long FTBUTs of ≥ 8 s. Uncorrected distance visual acuity, corrected distance visual acuity, manifest refraction, FTBUT, QoV and Ocular Surface Disease Index (OSDI) questionnaires were recorded 1 and 6 months postoperatively. RESULTS: Thirty-nine subjects were included in each group. There was no significant difference in visual outcomes between the 2 groups at both the 1- and 6-month postoperative assessments. FTBUT remained significantly lower in group 1. Oxford staining was initially higher for group 1 at 1 month (P = 0.007), but there was no significant difference at 6 months (P = 0.180). There was no significant difference in QoV or OSDI scores between the 2 groups at both postoperative visits. CONCLUSIONS: Low preoperative FTBUT (3-6 s) does not appear to negatively affect postoperative visual outcomes or results in a greater likelihood of dry eye symptoms and poor ocular surface compared to eyes with a longer preoperative FTBUT. These results suggest that a low preoperative FTBUT does not necessarily increase the likelihood of poor visual acuity, dry eyes symptoms, or poor ocular surface outcomes following SMILE surgery.

Computational study for temperature distribution in ArF excimer laser corneal refractive surgeries using different beam delivery techniques.

Refractive errors are the most common causes of vision impairment worldwide and laser refractive surgery is one of the most frequently performed ocular surgeries. Clinical studies have reported that approximately 10.5% of patients need an additional procedure after the surgery. The major complications of laser surgery are over/under correction and dry eye. An increase in temperature may be a cause for these complications. The purpose of this study was to estimate the increase in temperature during laser refractive surgery and its relationship with the complications observed for different surgical techniques. In this paper, a finite element model was applied to investigate the temperature distribution of the cornea when subjected to ArF excimer laser at a single spot using various beam delivery systems (broad beam, scanning slit, and flying spot). The Pennes bio-heat equation was used to predict the temperature values at different laser pulse energies and frequencies. The maximum temperature increase by ArF laser ([Formula: see text] frequency and [Formula: see text] pulse energy) at a single spot was [Formula: see text] for [Formula: see text] diopter correction ([Formula: see text] of ablation of corneal stroma) using broad beam, scanning slit, and flying spot beam delivery approaches respectively. The peak temperature due to a single pulse was estimated to be [Formula: see text]. Although the peak temperature (sufficient energy to break intermolecular bonds) exists for a very short time ([Formula: see text]) compared to the thermal relaxation time ([Formula: see text]), there is some thermal energy exchange between corneal tissues during a laser refractive surgery. Heating may cause collagen denaturation, collagen shrinkage, and more evaporation and hence proposed to be a risk factor for over/under correction and dry eye.

Cirugía facorrefractiva en la alta miopía y sus complicaciones / Phaco-refractive surgery in high myopia and its complications

La miopía es un grave problema de salud pública por su alta y creciente prevalencia en distintas áreas geográficas. La cirugía facorrefractiva consiste en la extracción del contenido transparente o esclerosado del cristalino y el implante de una lente intraocular, con el objetivo posoperatorio de alcanzar o acercarse a la emetropía. Ha demostrado un resultado predecible y estable en el tiempo, pero no está exenta de complicaciones. Se presenta un paciente de 44 años de edad con antecedentes de oftalmológicos de miopía elevada, glaucoma secundario y cirugía facorrefractiva en ambos ojos, refracción dinámica de -3,50-100 x 200 con agudeza visual mejor corregida de 0,8 por cartilla de Snellen en el ojo derecho y -5,25 -1,25 x 1600 con agudeza visual mejor corregida de 0,6 en el ojo izquierdo. En el examen biomicroscópico se observó afaquia quirúrgica, opacidad de la cápsula posterior con capsulotomía láser central amplia y presencia de vítreo en la cámara anterior en ambos ojos con cifras de tensión ocular elevadas. Se realizó implante secundario de lente intraocular en ambos ojos. La refracción dinámica a los 3 meses fue para el ojo derecho de: -0,50 -0,50 x 400 con agudeza visual mejor corregida de 0,9 por cartilla de Snellen y para el ojo izquierdo de: -1,00 -0,75 x 1600 con agudeza visual mejor corregida de 0,6 por cartilla de Snellen. A los dos años presentó desprendimiento de retina subclínico en el ojo derecho, que fue tratado con terapia láser, y daño glaucomatoso en el ojo izquierdo. Se le realizó trabeculectomía, trabeculoplastia selectiva láser y posteriormente implante de drenaje valvulado en el ojo izquierdo(AU)

Myopia is a serious public health problem, due to its high and increasing prevalence in various geographic regions. Phaco-refractive surgery consists in extraction of the clear or sclerosed content of the crystalline lens and implantation of an intraocular lens with the postoperative objective of achieving or approaching emmetropia. The procedure has shown to obtain predictable results stable in time, but it is not exempt from complications. A case is presented of a male 44-year-old patient with an ophthalmologic history of high myopia, secondary glaucoma and phaco-refractive surgery in both eyes, dynamic refraction of -3.50-100 x 200 with best corrected visual acuity of 0.8 on the Snellen chart in the right eye and -5.25 -1.25 x 1600 with best corrected visual acuity of 0.6 in the left eye. Biomicroscopic examination found surgical aphakia, posterior capsule opacity with large central laser capsulotomy, presence of vitreous in the anterior chamber of both eyes and high ocular pressure values. Secondary intraocular lens implantation was performed in both eyes. Dynamic refraction at three months was -0.50 -0.50 x 400 for the right eye with best corrected visual acuity of 0.9 on the Snellen chart, and -1.00 -0.75 x 1600 for the left eye with best corrected visual acuity of 0.6 on the Snellen chart. At two years the patient experienced subclinical retinal detachment in the right eye, which was treated with laser therapy, and glaucomatous damage in the left eye, for which the treatment indicated was trabeculectomy, selective laser trabeculoplasty, and then valved drainage implantation in the left eye(AU)

Repeatability and comparability of the Galilei-G4 and Cassini in measuring corneal power and astigmatism in normal and post-refractive surgery eyes.

To assess the repeatability and comparability of the Galilei G4 versus the Cassini topographer in post-refractive eyes and in normal eyes, including older patients representative of an initial cataract evaluation. Simulated keratometric (simK), total corneal and posterior corneal power and astigmatism were evaluated in both post-refractive and normal eyes. Repeatability was measured by calculating within-subject standard deviation (Sw), coefficient of variation (CoV), and intraclass correlation coefficient (ICC). Vector analyses and Bland-Altman plots were employed to assess agreement between devices. We studied 32 subjects with a history of refractive surgery and 32 subjects without a history of refractive surgery undergoing cataract surgery. The mean age was 55 ± 18.5 years and the age range was 21.5-91.5 years. In non-refractive and post-refractive eyes, the ICC was > 0.9 (P < 0.001) for all corneal powers and for simK and total corneal astigmatism for both analyzers. The ICC for posterior corneal astigmatism magnitude using the Galilei was 0.62 and 0.67 and for the Cassini 0.55 and 0.38 in normal and post-refractive eyes, respectively. In both post-refractive and normal eyes, the Galilei G4 and Cassini analyzers have high repeatability in simK, total, and posterior corneal power and low repeatability for posterior corneal astigmatism.

Evaluation of postoperative refractive error correction after cataract surgery.

Suboptimal cataract surgery outcomes remain a challenge in most developing countries. In Ghana, about 2 million people have been reported to be blind due to cataract with about 20% new cases being recorded yearly. The aim of this study was to evaluate postoperative correction of refractive errors after cataract surgery in a selected eye hospital in Ashanti Region, Ghana. This was a retrospective study where medical records of patients (aged 40-100) who reported to an eye hospital in Ghana from 2013-2018 were reviewed. Included in the study were patients aged ≥40 years and patients with complete records. Data on patient demographics, type of surgery, intra-ocular lens (PCIOL) power, availability of biometry, postoperative refraction outcomes, pre- and postoperative visual acuity were analyzed. Data of two hundred and thirteen eyes of 190 patients who met the inclusion criteria were analyzed. Descriptive analysis and Chi-square test were carried out to determine the mean, median, standard deviation and relevant associations. The mean ± SD age was 67.21±12.2 years (51.2% were females). Small Incision Cataract Surgery (99.5%) with 100% IOL implants was the main cataract surgery procedure in this study. Pre-operative biometry was performed for 38.9% of all patients on their first eye surgery and 41.5% for second eye surgeries. About 71% eyes in this study were blind (presenting VA<3/60) before surgery; 40.4% had post-operative VA <3/60. Pre-existing ocular comorbidities discovered post- surgery, attributed to suboptimal visual outcomes. More than half (55.3%) of patients did not undergo postoperative refraction due to loss to follow-up. Year of surgery (p = .017), follow up visits< 2months (p < .0001) and discovered comorbidity post-surgery (p = .035) were the factors significantly associated with postoperative refraction. Myopia and compound myopic astigmatism were the dominant refractive error outcomes. The timing of post-operative refraction had a significant effect on postoperative refraction done. These findings indicate a clinically meaningful significance between completion of postoperative care and postoperative refraction done. Consequently, with settings in most developing countries, where less biometry is done, it is appropriate that post-operative refractive services are encouraged and done earlier to enhance the patients' expectations while increasing cataract surgery patronage.

Fórmula Barrett True K en pacientes con catarata operados de cirugía refractiva corneal / The Barrett True-K formula in cataract patients undergoing corneal refractive surgery

Objetivo: Determinar los resultados refractivos en pacientes operados de catarata con cirugía refractiva corneal, según el cálculo del poder dióptrico de la lente intraocular con la fórmula Barrett True K. Métodos: Se realizó un estudio pre-experimental, del tipo antes y después, en el cual fueron incluidos 18 pacientes (31 ojos). En ellos se analizaron variables demográficas y clínicas. La principal variable de salida fue la predictibilidad del componente esférico ± 0,50 D, ± 1,0 D según la longitud axial. Resultados: Fueron estudiados pacientes con un promedio de edad de 59,4 años, predominantemente del sexo femenino (66,7 por ciento). El 77,4 por ciento fue operado con queratotomía radial. Con la cirugía de catarata se produjo una mejora ostensible de la agudeza visual no corregida (mediana preoperatoria: 0,12 y mediana posoperatoria: 0,60). Solo el 9,7 por ciento de los ojos analizados presentó una agudeza visual sin corregir de 20/20 y el 90,3 por ciento de 20/40 o más. La cantidad de ojos con un equivalente esférico de ± 0,50 disminuyó en la medida en que aumentó la longitud axial (corta: 100 por ciento; normal: 57,1 por ciento; larga: 22,7 por ciento), no así la predictibilidad del componente esférico de ± 0,50, que aumentó (corta: 50,0 por ciento; normal: 57,1 por ciento; larga: 63,6 por ciento). Conclusiones: La fórmula Barrett True K resulta útil para el cálculo de la lente intraocular en pacientes operados de catarata y cirugía refractiva corneal previa(AU)

Objective: Determine refractive outcomes in patients undergoing cataract corneal refractive surgery based on intraocular lens dioptric power calculation with the Barrett True-K formula. Methods: A pre-experimental before/after study was conducted of 18 patients (31 eyes). Demographic and clinical variables were analyzed. The main output variable was spherical component predictability ± 0.50 D, ± 1.0 D according to axial length. Results: Mean age was 59.4 years; female sex prevailed (66.7 percent). Of the patients studied, 77.4 percent underwent radial keratotomy. Cataract surgery led to notable uncorrected visual acuity improvement (preoperative mean: 0.12; postoperative mean: 0.60). Only 9.7 percent of the eyes examined had an uncorrected visual acuity of 20/20, whereas 90.3 percent had 20/40 or more. The number of eyes with a spherical equivalent of ± 0.50 fell as axial length rose (near: 100 percent; normal: 57.1 percent; far: 22.7 percent), unlike ± 0.50 spherical component predictability, which rose from near: 50.0 percent; normal: 57.1 percent; far: 63.6 percent. Conclusions: The Barrett True-K formula is useful for intraocular lens calculation in patients undergoing previous cataract and corneal refractive surgery(AU)

Information sources for patients undergoing corneal refractive surgery: results from a cross-sectional patient survey from a single private center in Pola​nd.

PURPOSE: To identify the information sources for patients undergoing laser vision correction. METHODS: Individuals who underwent corneal refractive surgery at a private practice from December 2017 to August 2018 and agreed to complete an anonymous questionnaire were included. The manifest refraction and surgical method was recorded and correlated with the questionnaire results. RESULTS: Data collected from 126 patients (mean age, 32.8 ± 8.6 years; 55.6% women) were analyzed. Of 121 patients, 120 (99.2%) identified the Internet as a source for information on refractive surgery, and 71 of 119 (59.7%) noted that the clinic's website influenced their choice of clinic. Patients with high myopia more commonly used contact lenses and had considered undergoing refractive surgery for a longer time compared with patients with other refractive errors (P < 0.01 and P < 0.01, resp.). Patients with hyperopia were less likely to know their own refractive error (P = 0.02). CONCLUSIONS: In this patient cohort, the Internet was the main source of information for those undergoing refractive surgery.

A new trifocal corneal inlay for presbyopia.

Corneal inlays (CIs) are the most recent surgical procedure for the treatment of presbyopia in patients who want complete independence from the use of glasses or contact lenses. Although refractive surgery in presbyopic patients is mostly performed in combination with cataract surgery, when the implantation of an intraocular lens is not necessary, the option of CIs has the advantage of being minimally invasive. Current designs of CIs are, either: small aperture devices, or refractive devices, however, both methods do not have good performance simultaneously at intermediate and near distances in eyes that are unable to accommodate. In the present study, we propose the first design of a trifocal CI, allowing good vision, at the same time, at far, intermediate and near vision in presbyopic eyes. We first demonstrate the good performance of the new inlay in comparison with a commercially available CI by using optical design software. We next confirm experimentally the image forming capabilities of our proposal employing an adaptive optics based optical simulator. This new design also has a number of parameters that can be varied to make personalized trifocal CI, opening up a new avenue for the treatment of presbyopia.

Comparación entre las mediciones biométricas del IOL Master 500 y el Pentacam AXL en la biometría ocular / Comparison of biometric measurements taken with IOL Master 500 and Pentacam AXL for ocular biometry

Objetivo: Comparar las mediciones biométricas realizadas con el IOL Master 500 y el Pentacam AXL. Métodos: Se realizó un estudio transversal en 99 ojos de 99 pacientes miopes con criterio de cirugía fotoablativa, atendidos en el período de enero del año 2019 a enero de 2020, en el Servicio de Cirugía Refractiva del Instituto Cubano de Oftalmología "Ramón Pando Ferrer". Las variables estudiadas fueron edad, sexo, equivalente esférico y características biométricas preoperatorias (longitud axial, profundidad de la cámara anterior y queratometrías), así como su relación, aportadas automáticamente por el IOL Master 500 y el Pentacam AXL para evitar los factores dependientes del operador. El análisis estadístico se realizó con la Prueba t para datos pareados, utilizando una significación del 95 por ciento. Una diferencia con un valor de p < 0,05 fue considerado estadísticamente significativo. Resultados: El 60,61 por ciento de los pacientes eran de sexo femenino y el 39,39 por ciento del masculino, con una edad promedio de 25,67 ± 4,30 años. Se analizaron 51 ojos derechos y 48 izquierdos. El equivalente esférico medio fue de -3,30 ± 1,53 dioptrías. No hubo diferencia estadísticamente significativa entre los valores biométricos (longitud axial, profundidad de la cámara anterior y queratometrías) obtenidos con el IOL Master 500, en comparación con los del Pentacam-AXL (p > 0,05). Conclusión: Las mediciones biométricas (longitud axial, profundidad de la cámara anterior y queratometrías) obtenidas con el IOL Master 500 y el Pentacam-AXL son similares(AU)

Objective: Compare biometric measurements taken with IOL Master 500 and Pentacam AXL. Methods: A cross-sectional study was conducted of 99 eyes of 99 myopic patients with indication of photoablative surgery attending the Refractive Surgery Service at Ramón Pando Ferrer Cuban Institute of Ophthalmology from January 2019 to January 2020. The variables analyzed were age, sex, spherical equivalent and preoperative biometric characteristics (axial length, anterior chamber depth and keratometries) and the relationship to one another, automatically supplied by IOL Master 500 and Pentacam AXL to avoid operator-dependent factors. Statistical analysis was based on the paired T-test with a significance level of 95%. A difference with a p-value < 0.05 was considered to be statistically significant. Results: Of the patients studied, 60.61 percent were female and 39.39 percent were male; mean age was 25.67± 4.30 years. A total 51 right eyes and 48 left eyes were analyzed. Mean spherical equivalent was -3.30 ± 1.53 diopters. No statistically significant difference was found between the biometric values (axial length, anterior chamber depth and keratometries) obtained with IOL Master 500 versus Pentacam AXL (p > 0.05). Conclusion: Similar biometric measurements (axial length, anterior chamber depth and keratometries) are obtained with IOL Master 500 and Pentacam AXL(AU)

Accuracy of partial coherence interferometry in patients with large inter-eye axial length difference.

BACKGROUND: To determine accuracy of partial coherence interferometry (PCI) in patients with large inter-eye axial eye length (AEL) difference. METHODS: Patients undergoing cataract surgery at two academic medical centers with an inter-eye axial eye length (AEL) difference of > 0.30 mm were identified and were matched to control patients without inter-eye AEL difference > 0.30 mm on the basis of age, sex, and AEL. The expected post-operative refraction for the implanted IOL was calculated using SRK/T, Holladay II, and Hoffer Q formulae. The main outcome measures were the refractive prediction error and the equivalence of the refractive outcomes between the subjects and controls. RESULTS: Review of 2212 eyes from 1617 patients found 131 eyes of 93 patients which met inclusion criteria. These were matched to 131 control eyes of 115 patients. The mean AEL was 24.92 ± 1.50 mm. The mean absolute error (MAE) ranged from 0.47 D to 0.69 D, and was not statistically different between subjects and controls. The refractive prediction error was equivalent between the cases and controls, with no significant difference between the MAE for any formula, nor in the number of cases vs. controls with a refractive prediction error of at least 0.50 D or 1.00 D. CONCLUSIONS: Among eyes in our study population, good-quality PCI data was equally accurate in patients with or without an inter-eye AEL difference > 0.30 mm. Confirmatory AEL measurements using different AEL measuring modalities in patients with a large inter-eye AEL difference may not be necessary.

Intraocular Lens Complications: Decentration, Uveitis-Glaucoma-Hyphema Syndrome, Opacification, and Refractive Surprises.

As cataract surgery has evolved, intraocular lens (IOL) complications are rare. The purpose of this review was to report the incidence, diagnosis, and management of IOL decentrations, uveitis-glaucoma-hyphema (UGH) syndrome, IOL opacifications, and refractive surprises. Literature review was performed by searching PubMed, MEDLINE, EMBASE, and the Cochrane Controlled Trial Database and the reference lists of original studies as well as reviews. Intraocular lens decentrations and dislocations can appear at any time, particularly in patients with predisposing factors such as pseudoexfoliation, prior vitreoretinal surgery, or trauma. Recognizing when they require surgical intervention for UGH or to improve visual function is critical in limiting long-term sequela. Intraocular lens opacifications such as glistenings rarely require intervention, but others, such as subsurface nanoglistenings, calcifications, or discolorations, may require IOL exchange. Finally, despite our best efforts to enhance measurements and IOL calculations, refractive surprises still occur. Intraocular lens complications are uncommon with modern cataract surgery. A number of these complications require proper identification and care to optimize patient outcomes.

Misalignment and tilt effect on aspheric intraocular lens designs after a corneal refractive surgery.

PURPOSE: To numerically evaluate and compare the tolerance to misalignment and tilt of aspheric intraocular lenses (IOLs) designed for three eyes: with standard cornea and with simulated corneas after myopic and hyperopic laser ablation surgery. METHODS: Three aspheric IOLs of +20.00 diopter (D) with different spherical aberration (SA) ([Formula: see text]) values have been designed using a theoretical model eye. Drastic changes on the theoretical eye anterior corneal asphericity have been performed to simulate myopic and hyperopic refractive surgeries. The effect of IOL misalignment and tilt on the image quality has been evaluated using a commercial optical software design for the three eye models. Image quality was assessed from the modulation transfer function (MTF), root mean square (RMS) values of defocus, astigmatism, coma and spherical aberration ([Formula: see text]), and retinal images obtained from a visual simulator using an aleatory optotype of 0.00 LogMar visual acuity (VA). RESULTS: IOL misalignment and tilt reduced MTF values in general, and increased wavefront aberrations errors. Aberration-free IOLs maintained best the MTF values when misalignments were applied, together with good on-axis optical quality. IOLs with negative SA ([Formula: see text]) correction decreased the MTF value under 0.43 for misalignments values higher than 0.50 mm with the three corneas. The effect of misalignment on RMS astigmatism and coma was correlated with the IOL SA ([Formula: see text]) and with the three corneas. CONCLUSIONS: This theoretical study shows that the largest degradation in image quality arises for the IOL with the highest amount of spherical aberration ([Formula: see text]). Moreover, it has been found that the aspherical design has a more influential role in misalignment tolerance than in tilt tolerance.

Research Progress of the Application of Hypothermia in the Eye.

Hypothermia is widely used in the medical field to protect organs or tissues from damage. Different research fields have different explanations of the protection mechanism of hypothermia. Hypothermia is also widely used in the field of ophthalmology, for example, in the eye bank, the preservation of corneal tissue and the preservation of the eyeball. Low temperature can also be applied to some ophthalmic diseases, such as allergic conjunctivitis, retinal ischemia, and retinal hypoxia. It is used to relieve eye symptoms or reduce tissue damage. Hypothermic techniques have important applications in ophthalmic surgery, such as corneal refractive surgery, vitrectomy surgery, and ciliary body cryotherapy for end-stage glaucoma. Hypothermia can reduce the inflammation of the cornea and protect the retinal tissue. The eyeball is a complex organ, including collagen tissue of the eyeball wall and retinal nerve tissue and retinal blood vessels. The mechanism of low temperature protecting eye tissue is complicated. It is important to understand the mechanism of hypothermia and its applications in ophthalmology. This review introduces the mechanism of hypothermia and its application in the eye banks, eye diseases (allergic conjunctivitis, retinal ischemia, and hypoxia), and eye surgeries (corneal transplant surgery, corneal refractive surgery, and vitrectomy).

Medico legal considerations on refractive surgery.

This study is a summary of legal issues that occurred over time in Italy, concerning the evaluation of the professional responsibility of the health damage caused by refractive surgery, also in the light of the diagnostic elements obtained from the new techniques relating to diagnostic tests for preoperative surgical correction of the main ametropia.