Refractive Power Of Intraocular Lens Research Articles

Glistening phenomenon in acrylic hydrophobic intraocular lenses – how do perioperative factors and concomitant diseases effect it’s incidence and severity.

The aim: To evaluate the effect of selected perioperative factors and concomitant diseases on glistening of acrylic hydrophobic intraocular lens after phacoemulsification in a prospective study. Material and methods: 252 consecutive patients undergoing phacoemulsification with IOLs AcrySof IQ implantation were enrolled. The relationship between glistening and such factors as time of the surgery, the mean power and time of ultrasound energy, temperature of infusion fluids, type of cartridge, mean power of intraocular lens, trypan blue staining as well as some concomitant systemic and local diseases were analysed. The aforementioned factors were assessed a month 1. and 6. as well as after 1 and 2 years postoperatively. Results: Glistening incidence and severity increased significantly at each follow up. The use of cartridge D during intraocular lens implantation was related with significantly higher incidence of glistening as compared to using cartridge C. Higher refractive power of intraocular lens was related with increased incidence of glistening. Significantly higher intensity of the glistening was assessed in patients who suffered from diabetes. In turn, patients with uveitis presented with statistically lower severity of glistening. There was no association between other analysed factors and glistening. Conclusion: Glistening commonly occurs in patients after phacoemulsification and acrylic hydrophobic intraocular lenses (AcrySof Alcon Labs) implantation. Some intraoperative factors such as refractive power of the lens and smaller diameter of thecartridge were assessed to be significantly correlated. It might indicate that potential damage to the intraocular lens may play a role in development of glistening. Significantly higher severity of glistening was shown in patients with diabetes, which may imply the role of breakdown of physiological intraocular barriers. It is further supported by the demonstrated lower intensity ofglistening in patients uveitis receiving high intensity steroid therapy.

Refractive shift of silicone oil tamponade in pseudophakic eye.

BackgroundRefraction change of silicone oil (SO) tamponade in phakic and aphakic eye has been studied thoroughly; however, it is rarely studied in pseudophakic eye. In this paper we aimed to deduce a theoretical formula predicting refractive shift of silicone oil tamponade in pseudophakic eye and compared it with clinical findings.MethodA theoretical formula was deduced through strict geometric optical principles under the Helmholtz Schematic eye model. Pre/postoperative refractive status of patients who previously underwent phacoemulsification, intraocular lens (IOL) implant, vitrectomy, SO tamponade and required SO extraction was studied.ResultsTwenty-six patients (27 eyes, 13 males and 13 females) were studied. Refractive error of SO-off was -1.88 ± 2.73D, and of SO-in was 2.02 ± 3.90. Refractive shift of SO tamponade was -3.90 ± 1.74D. Refractive shift was significantly associated with refractive power of IOL (r = -0.7903, p < 0.0001, Pearson correlation test) and anterior chamber distance (ACD, r = 0.3840, p = 0.0480, Pearson correlation test). Theoretical refractive shift was -4.10 ± 1.51D, and there was no significant difference between the theoretical and the clinical refractive shift (p = 0.3329, Paired T test).ConclusionsRefractive shift of SO tamponade in pseudophakic eye correlates with refractive power of implanted IOL and ACD, and strong correlation between theoretical formula and clinical findings was detected.Electronic supplementary materialThe online version of this article (doi:10.1186/s12886-016-0243-z) contains supplementary material, which is available to authorized users.

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

Objetivou-se com este trabalho determinar o poder dióptrico da lente intraocular (LIO) em miniporco e as dimensões do bulbo do olho. Foram utilizados 17 miniporcos, sadios, adultos, machos e fêmeas, com peso médio de 70kg. Em todos os olhos foram realizadas a ultrassonografia modo A, a ceratometria e a medida da distância limbo a limbo. O cálculo do poder dióptrico da LIO foi obtido utilizando-se as fórmulas Haigis, Hoffer Q, SRK/T, Holladay I e Holladay II e o software Holladay IOL Consultant(r). Na comparação entre o sexo e a lateralidade do olho, não houve diferença nas variáveis biométricas e poder da LIO. A aplicação das fórmulas (Haigis, Holladay II, Holladay I, SRK/T e Hoffer Q) possibilitou o cálculo do poder da LIO. A Holladay II, fórmula que melhor individualiza o bulbo do olho do miniporco, estima valor dióptrico ao redor de 41 D. Os miniporcos têm potencial como modelo experimental em oftalmologia, relacionado ao seu menor porte e à facilidade no manejo, especialmente em experimentos de longa duração.

Comparison of intraocular lenses from the standpoint of postoperative glare disability

Although implantation of an intraocular lens provides excellent postoperative visual acuity, some factors such as disability glare have attached importance to qualitative evaluation of the visual function of artificial pseudophakia. In order to find out which factor most greatly contributed to glare disability, four types of intraocular lens, convexplano, biconvex anterior more curved, posterior more curved, and equiconvex, were prospectively implanted. The patients were 21 men and 63 women, ranging in age from 39 to 92 years (mean +/- SD = 70.9 +/- 10.1 years). Glare disability, examined by the Titmus Miller-Nadler Glare Tester, was found to be significantly correlated to types of intraocular lens, refractive power of intraocular lens, but not to age of patients or strength of postoperative astigmatism. The lower glare disability index value was found in patients implanted with posteriorly more curved biconvex or equiconvex surface, and within a range of 18.5-22 D compared with those implanted with convex anterior or convex-plano surface, and 22.5 D or more.

Neue Formel zur Bestimmung der Brechkraft intraokularer Linsen

New, simplified formulas for calculating the refractive power of intraocular lenses are presented. These formulas were derived by mathematical methods. With the aid of these formulas it is possible to calculate an emmetropizing lens, residual refraction and desired postoperative refraction. The error in other formulas used for eyes with short axial lengths can be avoided with this new formula, due to its linearity.

A graphic method for determining the refractive power of intraocular lenses

A nomogram has been developed for determining the refractive power of emmetropic intraocular lenses. Individual deviations of optical dimensions from mean values, such as axis length, anterior chamber depth and corneal curvature are used to find a graphical solution. Errors of measurement of optical dimensions are analyzed with regard to their influence on the refractive power of an intraocular lens; errors in measuring the length of the axis have the greatest influence. The nomogram represents a simple method of determining the refractive power of an emmetropic lens. Furthermore, residual refraction can be determined if an intraocular lens of a given power is used or if postoperative ametropia is desired.

Experiences with calculating intraocular lenses

The necessity of calculating the refractive power of intraocular lenses in advance is emphasized and the authors' procedure described: Measurement of corneal radii with the Zeiss ophthalmometer, measurement of the bulb length with the A-Scan method, calculation of refractive power and the desired dioptric aniseikonia with the authors' own pocket calculator program using the formulas cited by Gernet. In 74% of the cases the postoperative difference from the pre-calculated refractions is less than 1 D, in 22% up to 2 D and in 4% up to 3 D.

Nomogramm zur Bestimmung der Brechkraft intraokularer Linsen

A nomogram for determining the refraction of intraocular lenses was developed to define the following diagnoses: emmetropizing lens, residual refraction of a given lens refraction and desired postoperative refraction. The nomogram makes an approximation solution possible to determine the refractive power of intraocular lenses from the basic refraction and the refractive power of the cornea.