Image quality comparison of two multifocal IOLs: influence of the pupil.

PURPOSE: To evaluate the effect of pupil size on image quality of a sectorial multifocal intraocular lens (IOL), the Lentis Mplus (Oculentis GmbH, Berlin, Germany), and the Acri.LISA IOL (Carl Zeiss Meditec, Jena, Germany). METHODS: The authors measured the MTFs of the Lentis Mplus LS-312 IOL and the Acri.LISA 366D IOL with three different sizes of pupil diameters: 3, 4, and 5 mm. The MTF was calculated from the cross-line spread function recorded with the OPAL Vector System (Image Science Ltd., Oxford, UK) by using fast Fourier-transform techniques. RESULTS: In distance focus, the image quality provided by the Lentis Mplus IOL was better than that of the Acri. LISA IOL with all pupil diameters. In near focus, the MTF of the Acri.LISA IOL was better with a 3-mm pupil, but poor with larger pupils. The aberration effect was equal in both IOLs in distance focus, but in near focus and with a 3-mm pupil, the Acri.LISA IOL was less affected by the aberration than the Lentis Mplus IOL. CONCLUSION: The Lentis Mplus IOL provides better distance image quality than the Acri.LISA IOL, whereas the near image quality of the Acri.LISA IOL is better with small-pupil diameter. The sectorial design makes this IOL more suitable for patients with a pupil diameter greater than 3 mm.

Determination of scattering in intraocular lenses by spectrophotometric measurements.

This study presents a method for measuring scattering in explanted intraocular lenses (IOLs). Currently, determining scattering in IOLs is usually performed by Scheimpflug cameras and the results are expressed in the units used by this apparatus. The method we propose uses a spectrophotometer and this makes it possible to measure the total transmission of the IOL by using an integrating sphere; the direct transmission is determined by the double-beam mode. The difference between these two transmissions gives a value of the scattering in percentage values of light lost. In addition, by obtaining the spectral transmission curve, information about the most scattered wavelengths is also obtained. The IOL power introduces errors when directly measured, particularly with high powers. This problem can be overcome if a tailor-made cuvette is used that shortens the distance between the IOL and the condensing lens of the spectrophotometer when the IOL powers are below 24 diopters. We checked the effectiveness of this method by measuring the scattering of three explanted IOLs from cornea donors. This method, however, does not make it possible to ascertain whether the scattering measured is caused by surface light scattering or internal light scattering.

Effect of the color of the intraocular lens on optical and visual quality.

Purpose: To analyze the optical quality of intraocular lenses (IOL) with an orange (PC440Y) and a yellow (SN60AT) filter, and correlate these results with the visual quality of patients with these implants. Setting: Fisabio Oftalmologνa Mιdica, Valencia, Spain. Design: Randomized prospective study. Materials and Methods: The IOL optical quality was determined using the modulation transfer function (MTF) and the spectral transmission. The visual quality of 87 eyes with cataract (51 with orange filter and 36 with yellow filter) was determined by best corrected visual acuity (BCVA) and contrast sensitivity function (CSF) under photopic and mesopic conditions. To analyze the results, we use a Student's t-test. Results: Orange lens filtered more of the blue spectrum (cut-off wavelength of 370 nm) than the yellow lens (390 nm). The MTF of the yellow lens was better than the orange lens (average modulation of 0.676 for natural and 0.672 for orange). The patients' BCVA was 0.02 + 0.10 logMAR for both lenses. The CSF obtained with the yellow lens was slightly better, although without statistically significant differences (P > 0.05). Conclusions: Both lenses are of good optical quality. The patients' visual quality was similar with both lenses, and optical quality was also similar. The color of the lens does not affect the visual quality of the patient.

Multichannel functional testing in normal subjects, glaucoma suspects, and glaucoma patients.

PURPOSE: To evaluate visual function with a novel multichannel functional test named the ATD Multichannel Functional Test. METHODS: This multicenter study had a prospective and cross-sectional design. A total of 186 eyes were included: 42 with glaucoma, 14 glaucoma suspects due to optic nerve characteristics, 25 ocular hypertensives, and 105 normal eyes. All patients performed standard visual fields (Humphrey 24-2) and ATD with eight stimuli configurations: four achromatic (A), two red-green (T), and two blue-yellow (D). To derive main outcome measures, mean sensitivity, mean defect (MD), and pattern standard deviation (PSD) were calculated and compared among groups and types of stimuli with the Kruskal-Wallis test. The percentage of cases outside normal limits (ONL) was calculated. RESULTS: MD and PSD were significantly different in glaucoma eyes than in normal subjects for all types of stimuli except D-0.5 cycles per degree (cpd)/12Hz. PSD was also lower for normals than for all pathologic groups with A-4cpd/2Hz, A-4cpd/12Hz, D-0.5cpd/2Hz, and T-0.5cpd/2Hz. The highest percentage of ONL cases was obtained with the two low-spatial-frequency chromatic stimuli, with D-0.5cpd/2Hz and T-0.5cpd/2Hz using PSD, which classified as ONL 81.6% and 86.7% of glaucoma eyes, 51.8% and 44.5% of hypertensives, and 72.2% and 41.2% of optic disc suspects, respectively. CONCLUSIONS: ATD assessed different aspects of visual function, and the most sensitive tests to detect glaucomatous damage were the low-temporal-frequency chromatic tests.

Spectral transmission of the human crystalline lens in adult and elderly persons: color and total transmission of visible light.

PURPOSE: To experimentally measure the spectral transmission of human crystalline lenses belonging to adult and elderly persons, and to determine the color and total transmission of visible light of such crystalline lenses. METHODS: The spectral transmission curve of 32 human crystalline lenses was measured using a PerkinElmer 800UV/VIS spectrometer. Total transmission of visible light and the chromatic coordinates of these crystalline lenses were determined from these curves for solar illumination. RESULTS: The crystalline lens that filters UV and its transmission in the visible spectrum decreases with age; such a decrease is greater for short wavelengths. The total transmission of visible light decreases, especially after the age of 70 years, and the crystalline color becomes yellower and saturated. CONCLUSIONS: The great variability existing in the spectral transmission of the human crystalline lens is lesser between the ages of 40 and 59 years, but greater from the age of 60 and older. The decrement in transmittance between these two age groups varies from 40% for 420 nm to 18% for 580 nm. Nevertheless, it is proven that age is not the only parameter affecting crystalline transmission. In the range of 40 to 59 years, age does not bear an influence on total transmission of light, but from 60 years and older it does. Moreover, the light transmitted decreases with age. This total transmission of light is similar to or lower than the amount that the different intraocular lenses transmit, even with a yellow or orange filter. The color of the human lens becomes yellowish and saturated with age.

Modulation transfer function of a toric intraocular lens: evaluation of the changes produced by rotation and tilt.

PURPOSE: To evaluate the changes in optical quality when toric intraocular lenses (IOL) are rotated or tilted and to demonstrate that IOL rotation produces an increasing effect of aberrations. METHODS: Modulation transfer function (MTF) and average modulation were used to analyze the image quality of a toric IOL. The axis of the toric IOL was rotated 5°, 10°, 15°, 20°, 25°, and 30° in successive MTF measurements. The tilt values were 0° to 5°, in increments of 1°, plus a tilt of 15°. Pupil diameters of 3 and 5 mm were used. RESULTS: The MTF decay due to aberrations was more sensitive to rotation than tilt. The main decrement in the average modulation, of approximately 50% in both pupils, occurs when the IOL rotates from 0° to 5°. Between 0° and 1° tilt, the average modulation decreases approximately 25% for both pupils; with tilt >1°, the average modulation remains virtually unchanged. The points representing average modulation versus rotation angle are satisfactorily fitted by an exponential function, R=0.98. Average modulation versus tilt angle provides lower correlation degrees, R=0.91 and R=0.79, for 3- and 5-mm pupils, respectively. CONCLUSIONS: The MTF of the toric IOL decays with rotation and tilt, with greater decrement occurring in rotation from 0° to 5°. An asymptotic value exists in the average modulation decay, meaning that for angles higher than 15°, the average modulation of the toric IOL remains virtually constant.

Residual astigmatism produced by toric intraocular lens rotation.

PURPOSE: To analyze changes in the eye's refractive properties when a toric intraocular lens (IOL) rotates. SETTING: Fundación Oftalmológica del Mediterráneo, Valencia, Spain. DESIGN: Experimental study. METHODS: The matrix definition of astigmatism was used in this theoretical study and compared with another vector representation. Two methods were compared: (1) The cylinder, C, resulting from the addition of 2 cylinders C(1) and C(2) whose axes form an angle a, is obtained by the addition of 2 vectors of values C(1) and C(2) forming an angle 2a; (2) the power matrix, F, of a thin astigmatic dioptric system that decomposes naturally into 3 orthogonal components: the purely spherical part F(nes,) the ortho-astigmatism F(or), and oblique astigmatism F(ob). RESULTS: The residual cylinder was one third of the corneal astigmatism when a toric IOL rotated ±10 degrees when the cylinder values for the cornea (C(1)) and IOL (C(2)) were equal. Nevertheless, in most cases C(1) is greater than C(2); therefore, the residual astigmatism did not change noticeably with small rotations. The angle of rotation, b, which annuls the astigmatism correction, could be obtained from the following: cos(π + 2b) = -r/2, with r being the ratio between the IOL and cornea cylinders. CONCLUSIONS: The 2 methods gave equivalent results. When the IOL cylinder had a value different from that of the corneal astigmatism, a better choice would be a lower, rather than higher, cylinder value to reduce residual astigmatism. In general, toric IOL rotations less than 10 degrees changed the eye's refraction less than 0.50 diopter. Thus, small axis rotations are not an obstacle for satisfactory astigmatism correction with toric IOLs. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Lens opacities in Valencia, Spain.

PURPOSE: To evaluate the most common lens opacities in Valencia (Spain), analyzed by gender, grade, and type of cataracts. The results are compared with other studies performed at other geographical latitudes and on different races. METHODS: A total of 1951 eyes of patients diagnosed with cataracts, aged between 30 and 96 years, were evaluated in accordance with age, gender, type and degree of the cataract, bilaterality, and symmetry of this disease. Lens Opacities Classification System III was used to classify the cataract and the degree was graded as mild or moderate to advanced. RESULTS: The most common type of cataract is corticonuclear in the elderly and subcapsular in younger subjects. The most common are nuclear (28.4%) followed by cortical (6.2%), if combined cataracts are ruled out. There is a greater incidence of cortical cataracts in women (70%) and subcapsular cataracts in men (70%). CONCLUSIONS: The results suggest the existence of a gender factor in cataract formation and coincide with those obtained in similar studies performed in areas at a similar latitude (40º N) and with different race population. The geographical location (intensity and length of exposure to solar radiation) seems to be a determining factor in the formation of a specific type of cataract, more than race, although there are other factors that contribute in the formation of a specific type of cataract.

A simple description of age-related changes in crystalline lens thickness.

PURPOSE: An increase in lens thickness is often described as a linear function of age. However, contradictory opinions exist about whether the lens thickness continues to increase after 50 years of age. Differences in slope exist between this increase in younger and older people, but these findings are inconsistent with the linear behavior of an increase in the lens thickness throughout life. We investigated among different functions, including slope variation, which would be the best to show the relation between lens thickness and age. An available model portraying lens growth could be advantageous in many practical applications. The possibility of differences between sexes in lens thickness growth is also analyzed. METHODS: We evaluated 102 eyes of patients aged between 15 and 84 years: 41 men, 61 women. The biometric measurements were performed with the aid of the OcuScan® (Alcon, USA). RESULTS: Both logarithmic and potential functions provide a good fit for the data (R2 = 0.905 and 0.906, respectively). The results do not show significant differences between men and women in any age range, nor when the data of the whole sample are considered (p = 0.29). CONCLUSIONS: The best fits for the data are both logarithmic and double logarithmic functions. According to this model, lens growth continues throughout life, but after 50 years, age-related thickness variations are lower than statistical variability. No differences were found between the sexes.

Spectral transmittance of intraocular lenses under natural and artificial illumination: criteria analysis for choosing a suitable filter.

PURPOSE: To compare the spectral transmission of different intraocular lenses (IOLs) with either ultraviolet (UV) or blue-light filters, and to analyze the performance of these filters with artificial light sources as well as sunlight. DESIGN: Experimental study. METHODS: The spectral transmission curve of 10 IOLs was measured using a PerkinElmer Lambda 800 UV/VIS spectrometer (Waltham, MA). Different filtering simulations were performed using the D65 standard illuminant as daylight and standard incandescent lamp and fluorescent bulb illuminants. MAIN OUTCOMES MEASURES: Spectral transmittance of the IOLs. RESULTS: All the IOLs studied provide good UVC (200-280 nm) and UVB (280-315 nm) protection, except for one that presented an appreciable window at 270 nm. Nevertheless, both natural and artificial sources have practically no emission under 300 nm. In the UVA (315-380 nm) range the curves of the different IOLs manifested different degrees of absorption. CONCLUSIONS: Not all the UV filters incorporated in different IOLs protect equally. The filters that provide greater photoprotection against UV radiation, even blue light, are yellow and orange. Then, yellow and orange IOL filters may be best suited for cases requiring special retinal protection. The filters that favor better photoreception of visible light (380-780 nm) are those that transmit this radiation close to 100%. Artificial illumination practically does not emit in the UV range, but its levels of illumination are very low when compared with solar light. A possible balance between photoprotection and photoreception could be a sharp cutoff filter with the cutoff wavelength near 400 nm and a maximum transmittance around 100%.

Correlation between optics quality of multifocal intraocular lenses and visual acuity: tolerance to modulation transfer function decay.

PURPOSE: To study the relationship between the optics quality of multifocal intraocular lenses (IOLs) and distance-corrected near, intermediate, and distance visual acuity to determine the degree to which optics quality must change to produce a significant difference in visual acuity. SETTING: Fundación Oftalmológica del Mediterráneo, Valencia, Spain. METHODS: Monocular distance-corrected visual acuity (decimal and logMAR) was measured at 4 m, 70 cm, and 30 cm under photopic and mesopic conditions in eyes with 1 of 3 multifocal IOL models. Visual acuity versus the "average modulation" of the IOL was assessed. RESULTS: The pupil diameter and patient age were similar between the 3 IOL groups (20 eyes each). A difference in average modulation (ie, optics quality) up to 15% did not produce significant differences in mean visual acuity between 2 groups; however, there was a significant difference in mean visual acuity between 2 groups when the average modulation values differed by at least 25%. The slope of the linear correlation between visual acuity and average modulation was 0.018 (r(2) = 0.91) under photopic conditions and 0.024 (r(2) = 0.089) under mesopic conditions. CONCLUSIONS: There was a strong linear correlation between IOL optics quality and visual acuity with distance correction under photopic conditions with a pupil of approximately 3.5 mm in a cohort in which the patient age was controlled. The correlation was similar under mesopic conditions. The eye's tolerance to modulation transfer function decay was approximately 15% of the average modulation value.

Imaging quality of bifocal piggyback intraocular lens versus ReSTOR and TECNIS multifocal lenses.

PURPOSE: The imaging quality provided by a piggyback integrated by a monofocal intraocular lens (IOL) + a bifocal IOL of zero power and +3.75 diopters of addition is compared with the optics quality of a simple multifocal IOL of the same power and addition. METHODS: The imaging quality was evaluated by determining the modulation transfer function (MTF), using an artificial eye simulating in vivo conditions of the anterior chamber, including an artificial cornea and a wet cell containing physiologic solution where the IOL was positioned. The MTFs of the bifocal piggyback for near and distance vision were measured, with pupil diameters of 3 and 5 mm, and compared with the MTFs of an equivalent power of ReSTOR and TECNIS multifocal IOLs measured under the same conditions. RESULTS: The MTFs for distance and near focus of the bifocal piggyback are similar to the MTFs of the ReSTOR and TECNIS multifocal IOLs with the two diameters of pupil. A more accurate comparison, values of average modulation, and Strehl ratio show a greater similitude with ReSTOR than with TECNIS. CONCLUSIONS: The bifocal piggyback system provides a similar imaging quality to that obtained with a ReSTOR multifocal IOL and, like the ReSTOR, provides better performance in distance vision than in near vision, whereas the TECNIS multifocal IOL provides the best performance.

Influence of optic quality on contrast sensitivity and visual acuity in eyes with a rigid or flexible phakic intraocular lens.

PURPOSE: To determine whether the difference in optic quality between 2 types of phakic intraocular lenses (pIOLs) affects visual quality. SETTING: Fundación Oftalmológica del Mediterráneo, Valencia, Spain. METHODS: Before implantation of a pIOL for myopia, all eyes had an examination including corrected (CDVA) and uncorrected (UDVA) distance visual acuity testing, corneal endothelial cell count (ECC), and intraocular pressure (IOP) measurement. The postoperative outcomes, determined at least 1 year after surgery, were CDVA; UDVA; contrast sensitivity function under photopic, mesopic, and mesopic with glare conditions; ECC; IOP; keratometry (Scheimpflug photography); and total ocular aberration (Hartmann-Shack aberrometry). RESULTS: Twelve eyes had implantation of an Artisan pIOL (rigid pIOL group) and 18 eyes, of an Artiflex pIOL (flexible pIOL group). The mean preoperative CDVA was 0.04 logMAR +/- 0.01 (SD) in both groups (P>.5). The mean postoperative CDVA was 0.01 +/- 0.02 logMAR in the rigid IOL group and 0.01 +/- 0.06 logMAR in the flexible IOL group (P>.9). The photopic contrast sensitivity function was better with the rigid pIOL, and the mesopic contrast sensitivity function was slightly better with the flexible pIOL; however, neither difference was statistically significant. CONCLUSIONS: Optic quality, measured by modulation transfer function and evaluated by average modulation, was approximately 13% better with the rigid pIOL than with the flexible pIOL. However, the difference was not enough to affect visual quality. At 1 year, the 2 groups had similar CDVA and contrast sensitivity function values, indicating that other optical or neural factors compensate for differences in optic quality.

Modulation transfer function: rigid versus foldable phakic intraocular lenses.

PURPOSE: To study in a standard eye model the changes in modulation transfer function (MTF) of a monofocal intraocular lens (IOL) when a phakic IOL (pIOL) is placed in the anterior chamber, compare the MTFs of the rigid Artisan pIOL and foldable Artiflex pIOL, and evaluate the temporal evolution of the MTF of the foldable pIOL after the mechanical stress the pIOL undergoes when injected. SETTING: Fundación Oftalmológica del Mediterráneo, Valencia, Spain. METHODS: The MTF values of the IOLs were calculated from the cross-line spread function recorded with the Opal Vector System. The measurements were taken using an eye model following the British and EN-ISO standards with 2.0 mm, 3.0 mm, 4.0 mm, and 5.0 mm pupils. A 28.00 diopter (D) Ophtec monofocal IOL was used as the crystalline lens. The 2 pIOLs were -9.00 D. RESULTS: The MTF of the rigid pIOL was slightly better than the MTF of the foldable pIOL with all pupil sizes. Both pIOLs provided good optics quality when compared with the monofocal IOL. The injection effect of the foldable IOL disappeared after 2 hours. CONCLUSIONS: The MTF of the monofocal IOL was slightly reduced with implantation of a negative pIOL in the anterior chamber. The rigid pIOL provided better optical performance than the foldable pIOL with all pupil sizes, as shown by the MTF values. The decrease in MTF caused by the mechanical stress on the foldable pIOL was nullified after 2 hours with no effect on optical quality.

Clinical magnification and residual refraction after implantation of a double intraocular lens system in patients with macular degeneration.

PURPOSE: To evaluate the efficacy of a standard double intraocular lens (IOL) system (IOL-Vip) in patients with low vision and central scotoma due to macular degeneration and assess the predictability of the residual refraction and magnification. SETTING: Ophthalmology Department, Hospital General Universitario, Valencia, Spain. METHODS: This interventional prospective noncomparative case series comprised 13 consecutive surgical procedures in 10 patients with central scotoma. Follow-up was 12 months. Evaluation included the difference between preoperative and postoperative best corrected visual acuity (BCVA), refraction, position of the IOLs, endothelial cell density, and occurrence of postoperative complications. Residual refraction and eye magnification were calculated using a theory developed in a previous study, and the values were compared with the clinical results. RESULTS: The mean BCVA was 1.37 logMAR preoperatively and 0.68 logMAR 1 year postoperatively. The mean best corrected clinical gain was 44%. There was no statistically significant difference between the clinically evaluated and theoretically calculated residual refractions (P = .17). No intraoperative or postoperative complications occurred. CONCLUSIONS: Implantation of the double IOL system improved BCVA in patients with low vision due to advanced maculopathy. The results were best in myopic patients (long eyes); patients with hyperopia (short eyes) had high residual refraction. The postoperative clinical gain and residual refraction were predictable, showing the feasibility of implanting a customized double IOL.

Image quality with multifocal intraocular lenses and the effect of pupil size: comparison of refractive and hybrid refractive-diffractive designs.

PURPOSE: To analyze the image quality with a refractive and 2 hybrid refractive-diffractive multifocal intraocular lenses (IOLs) in vitro to determine the IOL modulation transfer function (MTF) following the EN-ISO international standard for distance and near vision and to study the IOLs' behavior with different pupil sizes. SETTING: Fundación Oftalmológica del Mediterráneo, Valencia, Spain. METHODS: This study evaluated 4 IOLs: the hybrid refractive-diffractive AcrySof ReSTOR SN60D3 (Alcon) and Tecnis ZM900 (AMO), the refractive ReZoom NXG (AMO), and the monofocal AcrySof SN60WF (Alcon). The MTF was calculated from the cross-line spread function recorded with the OPAL Vector System (Image Science Ltd.) using fast Fourier transform techniques. The artificial eye model simulated in vivo conditions of the anterior chamber and included an artificial cornea and physiological solution, in which the IOLs were positioned. The pupil sizes varied between 2.0 mm and 5.0 mm in steps of 0.5 mm. RESULTS: For distance vision and small pupils (2.0 to 3.5 mm), the refractive IOL provided better image quality than the 2 hybrid IOLs. When the pupil was larger, the distance vision was similar with all IOLs. The 2 hybrid IOLs gave better image quality than the refractive IOL for near vision with any pupil size. With the refractive IOL and pupils smaller than 3.5 mm, near focusing did not occur, resulting in poor image quality. Of the hybrid IOLs, the AcrySof ReSTOR SN60D3 provided better distance image quality and the Tecnis ZM900 provided better near image quality. CONCLUSIONS: The refractive IOL gave better image quality than the hybrid IOLs at distance and with small pupils. With pupils larger than 3.5 mm, the quality was similar. Hybrid IOLs gave significantly better image quality for near vision with all pupil sizes. AcrySof ReSTOR SN60D3 IOLs give better distance vision than Tecnis ZM900 IOLs; the latter gave better near vision. The reference monofocal IOL provided better distance images than any multifocal IOL with all pupil sizes.

Optical analysis to predict outcomes after implantation of a double intraocular lens magnification device.

PURPOSE: To analyze the effect of different optical parameters of the eye on the outcomes of implantation of a double intraocular lens (IOL) magnification device in patients with low vision. SETTING: Fundación Oftalmológica del Mediterráneo, Valencia, Spain. METHODS: The eye's refraction and magnification before and after surgery were evaluated using a theoretical eye model based on paraxial optics approximation. Four parameters on which refraction and magnification are dependent were evaluated: anterior chamber depth (ACD), axial length (AL), mean keratometry (Km), and the distance between the 2 implanted IOLs. The 4 variables were analyzed separately in the first stage. Next, different combinations of ACD, AL, and Km values were studied. The goal was to predict what type of eye (in terms of ACD, AL, and Km values) is suitable for successful implantation of the double-IOL magnification device. RESULTS: Axial length had a significant influence on eye magnification. The Km value mainly affected refraction. The ACD did not influence the success of the procedure. The distance between the 2 IOLs was a decisive parameter in the analysis. CONCLUSIONS: Analysis of optical and biometric eye parameters could guide selection of patients for implantation of the double-IOL magnification device. Eyes with higher AL and Km values (myopic eyes) are the most suitable for this procedure.