Intraocular cataract lens replacement and light exposure potentially impact procedural learning in older adults.

Procedural learning declines with age and appropriately timed light exposure can improve cognitive performance in older individuals. Because cataract reduces light transmission and is associated with cognitive decline in older adults, we explored whether lens replacement (intraocular blue-blocking [BB] or UV-only blocking) in older patients with cataracts enhances the beneficial effects of light on procedural learning. Healthy older participants (n = 16) and older patients with post-cataract surgery (n = 13 with BB or UV lens replacement) underwent a randomized within-subject crossover laboratory design with three protocols. In each protocol, 3.5 hr dim-dark adaptation was followed by 2 hr evening blue-enriched (6,500K) or non-blue-enriched light exposure (3,000K or 2,500K), 30 min dim post-light, ~8 hr sleep and 2 hr morning dim light. Procedural learning was assessed by the alternating serial reaction time task (ASRT), as part of a larger test battery. Here, ASRT performance was indexed by type of trial (random or sequence) and sequence-specific (high or low probability) measures. During evening light exposure, we observed a significant effect of the interaction of "group" versus "light condition" on the type of trial (p = .04; p = .16; unadjusted and adjusted p-values, respectively) and sequence-specific learning (p = .04; p = .16; unadjusted and adjusted p-values, respectively), whereby patients with UV lens replacement performed better than patients with BB lens or non-cataract controls, during blue-enriched light exposure. Lens replacement in patients with cataracts may potentially be associated with beneficial effects of blue light on procedural learning. Thus, optimizing spectral lens transmission in patients with cataracts may help improve specific aspects of cognitive function, such as procedural learning.

Sagitta of ophthalmic lenses.

PURPOSE: To propose alternative formulas for the sagitta calculation of ophthalmic lenses. METHODS: Equation factoring. RESULTS: The conventional sagitta formula is algebraically inconsistent when applied to curves with direction-oriented radii. It is possible to correct this problem by factoring it. CONCLUSIONS: The conventional sagitta formula can and should be replaced by unambiguous equations.

[Glasses as Relevant Factor in Expert Opinions]. / Die Brille als Bewertungsfaktor im Gutachten.

Optical correction is an independent factor in expert opinions. It is outlined how this should be considered in different legal areas.

How close are we? An audit of biometry of a tertiary care hospital in Karachi.

OBJECTIVE: To evaluate the accuracy of biometry in the post-op phase of cataract surgery. METHODS: This study was conducted at Liaquat National Hospital, Karachi, from June 2015 to July 2016, and comprised the audit of patients who underwent cataract surgery during the period. Keratometry was done on Haag-Strait manual keratometer and A-scan was done by applanation contact method on SonoMed machine. Theoretic-T formula was used to calculate desired intraocular lens power for all kinds of axial lengths. A single surgeon operated upon the same Alcon Constellation phacoemulsification machine. Postoperative follow-up was done by monitoring auto refraction and visual acuity on days 1, 7, 30 and 90. SPSS 21 was used for data analysis.. RESULTS: Of 244 patients, 121(49.60%) were males and 123(50.40%) were females. There were 123(50.40%) right eyes and 121(49.60%) left eyes. Overall, 132(54.10%) achieved postoperative refraction within ±0.5 D of target and 193(79.10%) within ±1 D of target. Age, gender and laterality had no significant effect on outcomes (p>0.05 each). CONCLUSIONS: Postoperative refraction corresponded quite closely with global recommendations.

In vitro optical quality of monofocal aspheric toric intraocular lenses: effect of cylindrical power.

PURPOSE: To assess the in vitro optical quality of monofocal aspheric toric intraocular lenses (IOLs) as a function of the cylindrical power. METHODS: The in vitro optical quality of the AcrySof IQ Toric IOLs SN6AT2, SN6AT3, SN6AT4, SN6AT5 and SN6AT6 (Alcon Laboratories Inc., Forth Worth, TX, USA) was assessed with an instrument conceived for measuring Zernike's coefficients at 3.0- and 5.0-mm apertures. As a reference, the aspheric monofocal lens AcrySof IQ Aspheric SN60WF (Alcon Laboratories Inc., Forth Worth, TX, USA) was also measured. The area of visibility and cut-off frequency were used to describe the modulation transfer function (MTF) of each lens; meanwhile, the light in the bucket and the diameter of a circular area centred on the point-spread function (PSF) peak that captures 50% of the light energy were used to describe the PSF of each lens. Finally, an image simulation was computed from the Zernike values with reference purposes. RESULTS: Small differences were found on the metrics used for describing the MTF and PSF of the lenses at both tested apertures, but these were not statistically significant (p > 0.05). Furthermore, the image simulation showed that these differences would not have clinical relevance at all. CONCLUSIONS: The optical performance of the AcrySof IQ toric IOLs in terms of MTF and PSF is good and seems to be independent of the cylindrical power and similar to a non-toric aspheric lens.

[Study on the Imaging Quality Evaluation of Aspheric Intraocular Lenses].

The article is to study the objective evaluation method of the imaging quality of aspheric intraocular lens with different design concepts by establishing the model eye which is close to the actual corneal spherical aberration characteristics. Combined with the research data of corneal spherical aberration, the simulated cornea corresponding to Zernike c(4,0) coefficient 0.00 µm, 0.10 µm, 0.20 µm and 0.28 µm was established respectively. The optical quality of the measured simulated corneal lenses basically reached the theoretical design effect, and the deviation between the MTF value and the theoretical design value was equivalent to the MTF test repeatability. The establishment of model eye for artificial lens provides a research tool for the evaluation of aspheric intraocular lens imaging quality.

The clinical depth of field achievable with trifocal and monofocal intraocular lenses: theoretical considerations and proof of concept clinical results.

BACKGROUND: To estimate the depth of field (DOF) achievable with multi-and monofocal intraocular lenses (IOLs) and compare with actual measurements of DOF in cases implanted with a trifocal IOL and biconvex monofocal IOL METHODS: I) Computer simulations were produced to describe the relationship between DOF, pupil size, preoperative ametropia, and retinal blur tolerance limit for a model eye implanted with either multi- or monofocal IOLs. II) Monocular DOF and pupil size were measured under distance viewing conditions between 3 and 6 months postoperative following uneventful cataract surgery. Cases were implanted with either i) trifocal aspheric IOL (n = 36), or ii) biconvex aspheric monofocal IOL (n = 26). DOF was also measured at 0.33 m in cases implanted with i). RESULTS: Simulations revealed significant associations between DOF, pupil size, and retinal blur tolerance limit. The mean (±SD) DOF & pupil sizes were at distance for i)  above 2.59D (0.68) & 3.54 mm (0.377), and for ii) above 1.67D (0.51) & 2.90 mm (0.351), and for i) above 3.16D (0.46) at near. The difference between groups were significant for DOF and pupil size at distance (p < 0.001). DOF was significantly greater at near compared with distance in i) above (p < 0.001). For a pupil size of 3 mm, the simulations produce similar DOF values when the tolerance limit of retinal blur is 10 µ. CONCLUSIONS: The DOF was significantly better after implanting the trifocal IOL compared with the monofocal IOL, and DOF is increased under near viewing conditions. The clinical results are similar to calculated DOF values when the tolerance limit of retinal blur is 10 µ.

In vitro optical quality measurements of three intraocular lens models having identical platform.

BACKGROUND: With recent advances in technology and introduction of new intraocular lens (IOL) models, surgeons today have the opportunity to choose from various optical designs, which can influence the postoperative quality of vision. In our laboratory study, we compared the optical quality of three different IOLs that use the identical platform and are produced by the same manufacturer. The study included two diffractive multifocal IOLs, a bifocal and a trifocal one, as well as a monofocal IOL. METHODS: Three IOL models: monofocal CT ASPHINA 409 M, diffractive bifocal AT LISA 809 M, and diffractive trifocal AT LISA Tri 839MP (Carl Zeiss Meditec AG, Germany) were assessed for optical quality by measuring modulation transfer function (MTF) and Strehl Ratio (SR) values at pupil sizes of 3.0 and 4.5 mm on the OptiSpheric® IOL PRO (Trioptics GmbH, Germany). The United States Air Force (USAF) Target images were also recorded to comfirm the optical performance qualitatively. RESULTS: For far focus at 50 lp/mm and 3.0 mm pupil size, MTF value of the monofocal lens (MTF = 0.798) was 1.8-fold and 2.1-fold better than the bifocal (MTF = 0.446) and the trifocal (MTF = 0.382) IOLs, respectively. For near focus, bifocal IOL (MTF = 0.265) was 1.4-fold better than trifocal IOL (MTF = 0.187), while for intermediate focus, the trifocal IOL (MTF = 0.148) was 1.7-fold better than the bifocal IOL (MTF = 0.086). For the same pupil size, total sum of light loss amounted to 5.2% for the monofocal, 16.0% for the bifocal and 6.0% for the trifocal IOL. For a larger pupil, the amount of light loss increased significantly for the multifocal IOLs. CONCLUSIONS: The monofocal IOL performed the best for far, the bifocal IOL for near and the trifocal IOL for intermediate focus. While the monofocal IOL created the least amount of light loss for both pupil sizes, the trifocal IOL created less than half the amount of light loss than the bifocal IOL for small pupil. For large pupil, however, less light scatter was observed for the bifocal than the trifocal IOL.

Anterior Segment Biometry of the Accommodating Intraocular Lens and its Relationship With the Amplitude of Accommodation.

OBJECTIVES: To evaluate the anterior segment biometry of the Tetraflex accommodating intraocular lens (AIOL) and the contribution of forward movement to the amplitude of accommodation (AMP). METHODS: Patients who underwent phacoemulsification with implantation of Tetraflex AIOLs and control nonaccommodating intraocular lenses were imaged by custom-built, long scan depth spectral-domain optical coherence tomography at relaxed and maximal accommodative states. Anterior segment biometry was performed and correlated with the clinical manifestation including AMP. RESULTS: Patients in the Tetraflex group showed better distance-corrected near visual acuity (logMAR 0.43±0.10 vs. logMAR 0.51±0.10, P<0.05) and greater AMP (1.99±0.58 diopters [D] vs. 1.59±0.45 D, P<0.05) compared with the control group. The measurement of the postoperative anterior chamber depth (ACD) during accommodation showed a forward movement of the AIOLs in 16 eyes (69.6%). Compared with the control group, a greater proportion of cases in the Tetraflex group experienced forward movement (χ test, P<0.001). The AMP in the AIOL group negatively correlated with changes in postoperative ACD during accommodation (r=-0.47, P<0.05), whereas AMP in the control group negatively correlated with postoperative pupil diameter (r=-0.57, P<0.05). CONCLUSIONS: The Tetraflex AIOLs seemed to have a tendency for forward movement; however, the slight forward axial shifts of the Tetraflex AIOL during natural accommodation may not produce a clinically relevant change in optical power.

[Interpretation of the Intraocular Lens Constants for the Haigis Formula]. / Interpretation der Intraokularlinsenkonstanten für die Haigis-Formel.

Background The Haigis formula uses a linear regression with three IOL constants for the prediction of the effective lens position (ELP) of the intraocular lens (IOL), ELP ≈ a0 + a1 ACD + a2 L. It is based on the preoperative anterior chamber depth (ACD) and axial length (L). Material and Methods Differences between IOL constant triplets can be judged based on their statistical measurement uncertainty. To investigate, if the estimation of the average ELP with the help of the average ACD and average L according to 〈ELP〉 ≈ a0 + a1 〈ACD〉 + a2 〈L〉 provides a possible alternative, we have compared both methods. The results based on two different strategies for optimisation of the IOL constants a0, a1, a2 are used for illustration. Results The estimation of the average ELP is suitable for basic categorisation of the IOL constants. The confidence-volumes in shape of ellipsoids based on the statistical measurement uncertainties of the IOL constant optimisations allow a better comparison between IOL constant triplets a0, a1, a2.

[Multiple issues in multifocal intraocular lens].

The occurrence of multifocal intraocular lens (MIOL) is known as an important period in the development of cataract surgery, which can provide a simultaneous vision without the use of spectacles or contact lenses. However, in the current stage, MIOL implantation may also lead to decreased visual acuity and increased risk of photic phenomena, thus in some instance a second procedure to exchange the MIOL is necessary. Optimizing visual outcomes of MIOL implantation and controlling adverse effects has become the focus for ophthalmologists. In the future, a more remarkable, flexible and high cost-effective intraocular lens (IOL), which can mimic human natural crystalline lens, should emerge. (Chin J Ophthalmol, 2017, 53: 244-248).

[Evaluation of the safety and visual quality after implantation of the domestic made aspheric intraocular lens].

OBJECTIVE: To evaluate the safety and efficacy of the domestic foldable one-piece aspheric intraocular lens (IOL, Model: A1-UV) for the treatment of cataract. METHODS: A prospective randomized controlled clinical research were conducted. One hundred and nineteen cases (119 eyes) of cataract patients were randomly assigned to the study group (58 cases) and the control group (61 cases). The study group were implanted with the domestic made aspheric intraocular lens (Model: A1-UV) and the control group were implanted with imported aspheric intraocular lens (Model: SN60WF, Alcon Laboratories, Inc.). The visual acuity and the slit lamp examination were evaluated 1-2 day, 1 week, 1 month, 3 months, 6 months and 1 year postoperatively. In addition, the contrast sensitivity tests were carried out 3 months, 6 months and 1 year postoperatively. Data were analyzed by chi-square test and independent t-test. RESULTS: 100 patients had completed 1 year of follow-up, among which 49 cases were from the study group and 51 cases were from the control group. No severe inflammation or complications associated with intraocular lens were noted in either group within 1 year follow-up. The mean BCDVA, BCNVA, UCDVA, UCNVA(Log MAR) of the study group and the control group were 0.04±0.11, 0.11±0.17, 0.13±0.20, 0.35± 0.19 and 0.07±0.15, 0.15±0.20, 0.18±0.23, 0.41±0.21 at 1 year postoperatively. No statistically significant differences were noted between groups in mean BCDVA, BCNVA, UCDVA, UCNVA (t=-1.39, P=0.166; t=- 1.25, P=0.216; t=-1.06, P=0.292; t=-1.59, P=0.116) at 1 year postoperatively. And there was no significant difference in visual acuity between the two groups (P>0.05) 1-2 day, 1 week, 1 month, 3 months and 6 months postoperatively. The difference of the contrast sensitivity between the two groups was not statistically significant (P>0.05), besides the contrast sensitivity of the study group was significantly better than the control group at 12c/d, 18 c/d under bright light(t=2.18, P=0.031; t=2.67, P=0.009) at 3 months postoperatively. And the mean contrast sensitivity of the study group and the control group at 12c/d, 18 c/d under bright light were 1.31 ± 0.36, 0.86 ± 0.41 and 1.15 ± 0.40, 0.65 ± 0.44 at 3 months postoperatively. CONCLUSION: The safety and efficacy of the domestic made foldable one-piece aspheric intraocular lens (Model: A1-UV) for the treatment of cataract is equivalent to the imported aspheric intraocular lens (Model: SN60WF).

[Reliable UV-light protection in intraocular lenses--scientific rationale and quality requirements]. / Zuverlässiger UV-Schutz durch Intraokularlinsen--Rationale und Qualitätsanforderungen.

Since the late 1980s implantation of UV-blocker intraocular lenses during cataract surgery has become an internationally accepted standard. Last year the Kassenärztliche Vereinigung Bayern (KVB) and statutory health insurance organisations proposed for the first time quality criteria for intraocular lenses (IOL), thereby including exact parameters for the amount of UV light transmission (≤10% at 400 nm). Since then, the discussion has been raised again as to what extent IOLs should filter or block UV light. In this article, exact definitions of spectral subbands within the optical radiation band are given. Today, 400 nm is the internationally accepted standard to distinguish UV light and visible light. Moreover, exposure of the eye to UV radiation is described as well as mechanisms of photooxidative damage to the retina. Comprehensive laboratory and animal experimental studies show that light of short wave lengths, i.e., above all UV light but also blue light, may induce photochemical damage to the retina. Primary sites of such damage are both the outer segments of the photoreceptors and the retinal pigment epithelium (RPE). Physiological protective mechanisms of the eye, such as filtering properties of different ocular media are described in detail. Cornea, aqueous and vitreous absorb UV radiation below 300 nm, while the natural adult lens absorbs UV radiation between 300 and 400 nm. This protection is lost when the lens is removed by cataract surgery and thus should be restored. UV light does not contribute to vision but damages retinal structures. Therefore, UV-blocking intraocular lenses with a 10% cut-off near 400 nm should be implanted during cataract surgery. This ensures sufficient retinal protection after surgery. These theoretical considerations are supported by results from animal and clinical studies.

A ray tracing approach to calculate toric intraocular lenses.

PURPOSE: To quantify the precision of astigmatic correction in routine cataract surgery with toric intraocular lenses (IOLs) and to evaluate the predictability of keratometric and anterior/posterior topographic measurement for the improvement of the overall accuracy. METHODS: Seventy-eight eyes of 56 patients were implanted with toric IOLs. Data acquired by the Lenstar optical biometer (Haag-Streit, Bern, Switzerland) and TMS5 topography (Tomey, Nagoya, Japan) were processed with the ray tracing software Okulix (Tedics, Dortmund, Germany) to predict the residual refraction. Four different inputs were examined: keratometry only, anterior topography, anterior and posterior topography/ tomography, and combination of keratometry only and anterior and posterior topography/tomography. Four weeks postoperatively, the spherical prediction error and the cylindrical prediction error (difference vector between predicted and achieved cylindrical refraction) were determined. RESULTS: Mean absolute error of spherical prediction error was 0.27 diopter (D). Cylindrical prediction errors were 0.57 D (keratometry only), 0.56 D (anterior topography), 0.56 D (anterior and posterior topography/ tomography), and 0.50 D (combination of keratometry only and anterior and posterior topography/tomography). Differences between intraocular lens groups were statistically significant (Friedman test, P < .05). CONCLUSION: The combination of keratometry and anterior and posterior topography/tomography of anterior and posterior surface yielded the best results for toric IOL power calculations.

Imaging quality of multifocal intraocular lenses: automated assessment setup.

PURPOSE: A new technique for the assessment of the optical quality of multifocal intraocular lenses (MIOLs) under monochromatic and polychromatic illumination is presented. METHODS: The system provides, in a totally automated procedure, the modulation transfer function (MTF) of the lens under test for different axial positions of the object. The artificial eye admits different artificial corneas, to optimise the axial resolution in the sampling of the MTF of the MIOL under test, and different pupils, to test the dependence of the optical performance of the MIOL on the eye pupil diameter. RESULTS: The performance and sensitivity of the apparatus is tested with different commercial MIOLs. The through-focus MTF for a refractive MIOL was measured at different moments during the process of hydration of a hydrophilic lens. Next, to show the performance of our proposal, two commercial refractive and diffractive MIOLs were evaluated. CONCLUSIONS: We have designed a precise and robust optical method for testing MIOLs in vitro. The proposed method represents a valuable technical improvement to make the procedure of MIOL evaluation more versatile, efficient and trustworthy.

Alternative methodology for intraocular lens characterisation.

PURPOSE: To present an alternative methodology to characterise intraocular lenses (IOLs) using an optical setup with a Hartmann-Shack wavefront sensor. METHODS: The methodology was inspired by the ANSI Z80.30 Standard, which addresses IOL optical properties and test methods, and aims to simplify the procedure to allow complete IOL characterisation with a reduced number of measurement steps. RESULTS: Seven spherical and three toric IOLs were characterised with the alternative methodology and by commercial equipment. Three spherical IOLs measured with the alternative methodology obtained dioptric spherical errors larger than the tolerance established by the ANSI Z80.30 Standard when compared to the IOLs theoretical designs, probably due to manufacturing deviations. All cylindrical dioptric power measurements were within the Standard tolerance. The longitudinal spherical aberration of the IOLs were measured and 2-dimensional Modulation Transfer Functions (MTF) were calculated in order to complementarily assess manufacturing and design quality. CONCLUSIONS: The alternative methodology allows complete IOL characterisation with a reduced number of steps compared to those required by the Standard ANSI Z80.30, achieving satisfactory results in measurements of IOL dioptric power, spherical aberration, cylindrical power and MTF. Although MTF measurements were not performed with a model eye, they may contain additional relevant information regarding the design of ophthalmic lenses.

[Calculation of intraocular lens power in non-standard clinical situations].

Methods of intraocular lens (IOL) calculation in non-standard clinical situations have been developed and introduced. These include a formula that improves the calculation accuracy in patients with relatively short anterior-posterior axis and another method for eyes after previous radial keratotomy. A comparative clinical evaluation of the proposed methods has been performed. The results indicate good perspectives for their use in ocular surgery.

[Stereoscopic vision evaluation in patients after binocular implantation of different intraocular lens models].

Stereoscopic vision in patients after binocular implantation of different intraocular lens (IOL) models was evaluated. 24 patients (48 eyes) after cataract surgery were enrolled in the study. Follow-up was 12 months. 1st group included 9 patients (18 eyes) after cataract surgery and implantation of Russian trifocal refractive-diffractive IOL MIOL-Record 3. 2nd group included 6 patients (12 eyes) after cataract surgery and implantation of Russian bifocal refractive-diffractive IOL MIOL-Accord 3. 3rd group included 9 patients (12 eyes) after cataract surgery and implantation of Russian monofocal IOL MIOL-2. Stereoscopic vision was evaluated using "Stereopsis" software with 25 cm distance 1 week, 1, 3, 6, 12 months after surgery. Clinical study did not reveal any statistically significant difference between groups (trifocal, bifocal and monofocal IOLs) in terms of stereopsis (p > 0.05). Stereopsis parameters were stable during the whole follow-up period. Clinical study evaluating stereoscopic vision in patients after binocular implantation of different IOLs shows that patients with binocular implantation of bifocal and trifocal IOLs have good and stable stereoscopic vision parameters after surgery at least equal to patients with monofocal IOLs.