Mensurações do bulbo ocular e cálculo do poder dióptrico de lentes intraoculares em coelhos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Retinoscopia com luz em faixa em cães fácicos, afácicos e pseudofácicos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Mensurações do bulbo ocular e cálculo do poder dióptrico de lentes intraoculares em coelhos (Oryctolagus cuniculus), LINNAEUS, 1758)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliação do erro refracional por retinoscopia com luz em faixa em cães fácicos, afácicos e pseudofácicos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Biometria ocular na espécie Cebus apella

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Ocular dimensions, corneal thickness, and corneal curvature in quarter horses with hereditary equine regional dermal asthenia

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Mensurações do bulbo ocular e cálculo do poder dióptrico da lente intraocular em miniporcos brasileiros

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Testes oftálmicos, biometria ocular e cálculo do poder dióptrico da lente em corujas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Surgical outcomes of isolated lens coloboma with or without cataract among young adults

Objective: To evaluate the visual and refractive outcomes after phacoemulsification surgery in eyes with isolated lens coloboma. Design: Prospective, consecutive case series. Participants: Eighteen eyes with isolated lens coloboma of 13 patients were included in the study. Mean patient age was 13.9 ± 6.5 years. Methods: Patients underwent phacoemulsification surgery, with combined implantation of capsular tension ring (CTR) and intraocular lens. In colobomas of less than 120°, a CTR was used, whereas in colobomas of more than 120°, a Cionni-modified single eyelet CTR was used to achieve better capsular centration. The main outcome measures were uncorrected distance visual acuity, corrected distance visual acuity, refraction, and keratometry. Results: Mean logMAR uncorrected distance visual acuity and corrected distance visual acuity improved significantly from 1.53 ± 0.35 and 1.02 ± 0.47 before surgery to 0.67 ± 0.51 and 0.52 ± 0.49 at the last visit of the follow-up (p < 0.001). Mean refractive cylinder and spherical equivalent decreased significantly from –6.73 ± 1.73 and –6.72 ± 4.07 D preoperatively to –1.40 ± 1.39 and –0.83 ± 1.31 D at the end of the follow-up (p = 0.001 and p = 0.01, respectively). Mean keratometric astigmatism at preoperative and postoperative visits were 1.58 ± 0.97 and 1.65 ± 0.94 D, respectively (p = 0.70). Conclusions: Phacoemulsification with CTR and intraocular lens implantation is an effective and safe option for providing a refractive correction and a significant visual improvement in eyes with isolated lens coloboma.

Estimation of the Central Corneal Power in Keratoconus: Theoretical and Clinical Assessment of the Error of the Keratometric Approach

Purpose: The aim of this study was to analyze theoretically the errors in the central corneal power calculation in eyes with keratoconus when a keratometric index (nk) is used and to clinically confirm the errors induced by this approach. Methods: Differences (DPc) between central corneal power estimation with the classical nk (Pk) and with the Gaussian equation (PGauss c ) in eyes with keratoconus were simulated and evaluated theoretically, considering the potential range of variation of the central radius of curvature of the anterior (r1c) and posterior (r2c) corneal surfaces. Further, these differences were also studied in a clinical sample including 44 keratoconic eyes (27 patients, age range: 14–73 years). The clinical agreement between Pk and PGauss c (true net power) obtained with a Scheimpflug photography–based topographer was evaluated in such eyes. Results: For nk = 1.3375, an overestimation was observed in most cases in the theoretical simulations, with DPc ranging from an underestimation of 20.1 diopters (D) (r1c = 7.9 mm and r2c = 8.2 mm) to an overestimation of 4.3 D (r1c = 4.7 mm and r2c = 3.1 mm). Clinically, Pk always overestimated the PGauss c given by the topography system in a range between 0.5 and 2.5 D (P , 0.01). The mean clinical DPc was 1.48 D, with limits of agreement of 0.71 and 2.25 D. A very strong statistically significant correlation was found between DPc and r2c (r = 20.93, P , 0.01). Conclusions: The use of a single value for nk for the calculation of corneal power is imprecise in keratoconus and can lead to significant clinical errors.

Error induced by the estimation of the corneal power and the effective lens position with a rotationally asymmetric refractive multifocal intraocular lens

AIM: To evaluate the prediction error in intraocular lens (IOL) power calculation for a rotationally asymmetric refractive multifocal IOL and the impact on this error of the optimization of the keratometric estimation of the corneal power and the prediction of the effective lens position (ELP). METHODS: Retrospective study including a total of 25 eyes of 13 patients (age, 50 to 83y) with previous cataract surgery with implantation of the Lentis Mplus LS-312 IOL (Oculentis GmbH, Germany). In all cases, an adjusted IOL power (PIOLadj) was calculated based on Gaussian optics using a variable keratometric index value (nkadj) for the estimation of the corneal power (Pkadj) and on a new value for ELP (ELPadj) obtained by multiple regression analysis. This PIOLadj was compared with the IOL power implanted (PIOLReal) and the value proposed by three conventional formulas (Haigis, Hoffer Q and Holladay). RESULTS: PIOLReal was not significantly different than PIOLadj and Holladay IOL power (P>0.05). In the Bland and Altman analysis, PIOLadj showed lower mean difference (-0.07 D) and limits of agreement (of 1.47 and -1.61 D) when compared to PIOLReal than the IOL power value obtained with the Holladay formula. Furthermore, ELPadj was significantly lower than ELP calculated with other conventional formulas (P<0.01) and was found to be dependent on axial length, anterior chamber depth and Pkadj. CONCLUSION: Refractive outcomes after cataract surgery with implantation of the multifocal IOL Lentis Mplus LS-312 can be optimized by minimizing the keratometric error and by estimating ELP using a mathematical expression dependent on anatomical factors.

Positional accommodative intraocular lens power error induced by the estimation of the corneal power and the effective lens position

Purpose: To evaluate the predictability of the refractive correction achieved with a positional accommodating intraocular lenses (IOL) and to develop a potential optimization of it by minimizing the error associated with the keratometric estimation of the corneal power and by developing a predictive formula for the effective lens position (ELP). Materials and Methods: Clinical data from 25 eyes of 14 patients (age range, 52–77 years) and undergoing cataract surgery with implantation of the accommodating IOL Crystalens HD (Bausch and Lomb) were retrospectively reviewed. In all cases, the calculation of an adjusted IOL power (PIOLadj) based on Gaussian optics considering the residual refractive error was done using a variable keratometric index value (nkadj) for corneal power estimation with and without using an estimation algorithm for ELP obtained by multiple regression analysis (ELPadj). PIOLadj was compared to the real IOL power implanted (PIOLReal, calculated with the SRK-T formula) and also to the values estimated by the Haigis, HofferQ, and Holladay I formulas. Results: No statistically significant differences were found between PIOLReal and PIOLadj when ELPadj was used (P = 0.10), with a range of agreement between calculations of 1.23 D. In contrast, PIOLReal was significantly higher when compared to PIOLadj without using ELPadj and also compared to the values estimated by the other formulas. Conclusions: Predictable refractive outcomes can be obtained with the accommodating IOL Crystalens HD using a variable keratometric index for corneal power estimation and by estimating ELP with an algorithm dependent on anatomical factors and age.

Clinical evaluation of the Shin-Nippon NVision-K 5001/Grand Seiko WR-5100K autorefractor

Purpose. A clinical evaluation of the Shin-Nippon NVision-K 5001 (also branded as the Grand Seiko WR-5100K) autorefractor (Japan) was performed to examine validity and repeatability compared with subjective refraction and Javal-Schiotz keratometry. Methods. Measurements of refractive error were performed on 198 eyes of 99 subjects (aged 23.2 ± 7.4 years) subjectively (noncycloplegic) by one masked optometrist and objectively with the NVision-K autorefractor by a second optometrist. Keratometry measurements using the NVision-K were compared with the Javal-Schiotz keratometer. Intrasession repeatability of the NVision-K was also assessed on all 99 subjects together with intersession repeatability on a separate occasion separated by 7 to 14 days. Results. Refractive error as measured by the NVision-K was found to be similar (p = 0.67) to subjective refraction (difference, 0.14 ± 0.35 D). It was both accurate and repeatable over a wide prescription range (-8.25 to +7.25 D). Keratometry as measured by the NVision-K was found to be similar (p > 0.50) to the Javal-Schiotz technique in both the horizontal and vertical meridians (horizontal: difference, 0.02 ± 0.09 mm; vertical: difference, 0.01 ± 0.14 mm). There was minimal bias, and the results were repeatable (horizontal: intersession difference, 0.00 ± 0.09 mm; vertical: intersession difference, -0.01 ± 0.12 mm). Conclusion. The open-view arrangement of the Shin-Nippon NVision-K 5001 facilitates the measurement of static refractive error and the accommodative response to real-world stimuli. Coupled with its accuracy, repeatability, and capability to measure corneal curvature, it is a valuable addition to objective instrumentation currently available to the optometrist and researcher.

Changes of corneal biomechanics with keratoconus

PURPOSE: To perform advanced analysis of the corneal deformation response to air pressure in keratoconics compared with age- and sex-matched controls. METHODS: The ocular response analyzer was used to measure the air pressure-corneal deformation relationship of 37 patients with keratoconus and 37 age (mean 36 ± 10 years)- and sex-matched controls with healthy corneas. Four repeat air pressure-corneal deformation profiles were averaged, and 42 separate parameters relating to each element of the profiles were extracted. Corneal topography and pachymetry were performed with the Orbscan II. The severity of the keratoconus was graded based on a single metric derived from anterior corneal curvatures, difference in astigmatism in each meridian, anterior best-fit sphere, and posterior best-fit sphere. RESULTS: Most of the biomechanical characteristics of keratoconic eyes were significantly different from normal eyes (P <0.001), especially during the initial corneal applanation. With increasing keratoconus severity, the cornea was thinner (r = -0.407, P <0.001), the speed of corneal concave deformation past applanation was quicker (dive; r = -0.314, P = 0.01), and the tear film index was lower (r = -0.319, P = 0.01). The variance in keratoconus severity could be accounted for by the corneal curvature and central corneal thickness (r = 0.80) with biomechanical characteristics contributing an additional 4% (total r = 0.84). The area under the receiver operating characteristic curve was 0.919 ± 0.025 for keratometry alone, 0.965 ± 0.014 with the addition of pachymetry, and 0.972 ± 0.012 combined with ocular response analyzer biomechanical parameters. CONCLUSIONS: Characteristics of the air pressure-corneal deformation profile are more affected by keratoconus than the traditionally extracted corneal hysteresis and corneal resistance factors. These biomechanical metrics slightly improved the detection and severity prediction of keratoconus above traditional keratometric and pachymetric assessment of corneal shape.