Long-term prevention of capsular opacification after lens-refilling surgery in a rabbit model.

PURPOSE: To reduce capsular opacification by a peri-surgical treatment of the lens capsule with drugs in an in vivo rabbit model. Lens-refilling surgery is a potential therapeutic intervention to treat patients with a cataract lens. The lens material is replaced with an injectable (bio)polymer that retains the natural mechanical and optical lens properties, therewith allowing accommodation. The occurrence of capsular opacification mediated by lens epithelial cells negatively affects accommodation and vision and should be avoided in this lens restoration approach. METHODS: An in vivo rabbit animal model was used with lens replacement with a silicone-based gel-like polymer and concurrent treatment of the lens epithelium with drugs. A case-study approach was applied as both drug combinations and implantation times were varied. The following drugs were investigated for their potential to prevent capsular opacification long-term: actinomycin D, methotrexate, paclitaxel and Tween-20. All were administered in a hyaluronic acid vehicle. The rabbits were clinically followed for periods up to 4 years postimplantation. Eyes, corneas and lenses were analysed post-mortem using MRI and confocal microscopy. RESULTS: Treatment combinations containing actinomycin D generally led to the least appearance of capsular fibrosis. The use of Tween-20 or paclitaxel without actinomycin D resulted in much earlier and pronounced fibrotic responses. The aspect of capsular opacification was highly variable in individual animals. Application of the drugs in a hyaluronic acid vehicle appeared to be a safe method that spared the corneal endothelium. CONCLUSION: The feasibility of long-term prevention of fibrosis over a period of more than 4 years has been demonstrated in lens refilling in the rabbit model.

Prevention of capsule opacification after accommodating lens refilling: pilot study of strategies evaluated in a monkey model.

PURPOSE: To test 2 strategies to prevent capsule opacification after accommodating lens refilling in a rhesus monkey model. SETTING: Animal laboratory and laboratory of European university medical centers. DESIGN: Experimental study. METHODS: Six rhesus monkeys had refilling of the lens capsular bag. In the first strategy, before it was filled with a silicone polymer, the capsular bag was treated with noncommercial sodium hyaluronate 1.0% containing cytotoxic substances. In the second strategy, the capsular bag was filled with clinically used sodium hyaluronate 1.0% (Healon) after treatment with actinomycin-D. Slitlamp inspection was performed during a follow-up of 40 to 50 weeks. After enucleation, magnetic resonance images were obtained and confocal fluorescence imaging was performed. RESULTS: Using the first strategy, capsule opacification developed in all eyes. Using the second strategy, 1 monkey did not develop capsule opacification after a 9-month follow-up. In a second monkey, the lens capsule remained clear for 3 months, after which the hyaluronate refill material was exchanged with a silicone polymer and capsule opacification developed. Combining these results with those in a previous study, the difference in opacification between silicone and sodium hyaluronate as refilling materials was statistically significant (P<.01). CONCLUSIONS: That no capsular bag fibrosis occurred in the presence of hyaluronate suggests that the properties of hyaluronate are the reason that remaining lens epithelial cells do not develop into fibrotic cells. The choice of a suitable lens-refilling material prevents the development of capsule opacification. FINANCIAL DISCLOSURE: Mr. Terwee was an employee of Abbott Medical Optics B.V. during the study period. No other author has a financial or proprietary interest in any material or method mentioned.

Rostock Glare Perimeter: a distinctive method for quantification of glare.

PURPOSE: Disability glare induced by headlights of oncoming cars has been associated with reduced quality of vision. This study aimed at developing the Rostock Glare Perimeter to quantify dysphotopsia effects under simulated realistic conditions. METHODS: Sixty phakic subjects of different ages were dazzled by a bright light source centered at a projection screen 3.30 m away from the subject's eye. Using a projected marker moving outward from the screen center with angular steps of 0.25° in 12 directions, the area where the subject cannot distinguish the white spot from the glare effects of the light source was determined. A corresponding mean radius in a field angle relative to the subject's eye was defined as a measure for disability glare. Monocular and binocular measurements were performed, and a separate repeatability and reproducibility study was executed to determine the precision of the Rostock Glare Perimeter. RESULTS: A significant mean positive correlation of disability glare with age (r = 0.534, p < 0.001) was found. The disability glare ranged from 0.33° to 1.8°, and a strong (r = 0.93, p < 0.0002) binocular summation effect was found. The repeatability and reproducibility limit of the Rostock Glare Perimeter method is 0.14° for 95% confidence interval. CONCLUSIONS: The Rostock Glare Perimeter method is sensitive to detect age-related disability glare differences and to find binocular summation for disability glare in a healthy population for small field angles with high angular resolution. These findings suggest that the Rostock Glare Perimeter method is a helpful device to quantify symptoms of glare.

Prevention of capsular opacification after accommodative lens refilling surgery in rabbits.

Silicone gel-like polymers have been proposed to replace the cataractous lens and therewith restore both vision and accommodation. Lens replacement is associated with opacification of the capsular bag due to the lens epithelial cell response. In this study, the in vivo effectiveness of a 5 min treatment with actinomycin D and/or cycloheximid to prevent the development of capsular opacification after filling the capsular bag with a silicone polymer as an accommodating lens was studied. It was found that treating the inside of the capsular bag with a solution containing actinomycin D reduced the development of visible capsular opacification for three months. In some animals, the lens capsules were completely clear, indicating the potential of this method. Side effects of the treatment in the form of visible cornea opacification occurred and ranged from mild to severe in some animals, while in other animals no toxicity occurred. This indicates that a safe application of the cytotoxic substances is feasible. In view of the side effects and the fact that not all lens capsules of the animals treated with actinomycin D were clear, improvements in the methods used are necessary and seem to be possible.

In vivo 7.1 T magnetic resonance imaging to assess the lens geometry in rabbit eyes 3 years after lens-refilling surgery.

PURPOSE: To evaluate the utility of high-resolution magnetic resonance imaging (MRI) in assessing the normal and refilled lens geometry in rabbits after lens-refilling surgery. SETTING: University of Rostock, Rostock, Germany. DESIGN: Experimental study. METHODS: High-resolution ocular MRIs were acquired (7.1 T ClinScan) using a 2-channel coil with 4 coil elements and T2-weighted turbo spin-echo sequences (slice thickness 700 µm, field of view 40 mm × 40 mm) in rabbits after lens refilling surgery combined with intraoperative treatment to prevent lens epithelial cell proliferation. Single slices were used to assess the refilled lenses 3 years postoperatively. RESULTS: The entire geometry (cross-sectional area, radius of curvature, axial and equatorial diameters) of the crystalline and refilled lenses was visualized by in vivo 7.1T MRI 3 years postoperatively (in-plane resolution: 125 µm × 125 µm). In refilled eyes, the capsule and the homogenous silicone polymer remained in close contact with no visible interface. The dimensions of the refilled lens were significantly smaller than those of the crystalline lens of the contralateral eye. CONCLUSIONS: High-resolution MRI allows in vivo visualization and analysis of the spatial arrangement of the lens in rabbit eyes after lens refilling surgery and overcomes a number of major limitations in the quantitative evaluation of the lens shape. Further efforts are required to optimize the amount of polymer injected during lens refilling to achieve a predictable refractive outcome after lens refilling surgery. FINANCIAL DISCLOSURE: Drs. Stachs, Langner, Sternberg, Martin, Schmitz, Hosten and Guthoff have no financial or proprietary interest in any material or method mentioned. Additional financial disclosure is found in the footnotes.

Drug-induced secondary cataract prevention: experimental ex vivo and in vivo results with disulfiram, methotrexate and actinomycin D.

BACKGROUND/AIMS: A clinical approach to prevent secondary cataract after lens implantation involves the intraocular application of pharmacological agents. The goals of our study were to develop an ex vivo model to test the drug effectiveness for lens epithelial cell ablation from the basal membrane and to verify the data in rabbit intraocular lens implantation experiments. METHODS: Human capsular rhexis specimens were incubated with drugs and the residual cells were differentiated by use of the Live-Dead assay and quantified by staining with Hoechst dye. After phakoemulsification of rabbit eyes and before intraocular lens implantation, capsular bags were filled with drug-loaded hyaluronic acid for 5 min. RESULTS: An ex vivo model was established which allows the testing of drugs on lens epithelial cell ablation. Drug treatment reduced the number of viable cells on the specimens drastically, ranging between 0.44 ± 0.53% (6.0 ± 7.3 cells/mm²) for disulfiram, 0.27 ± 0.50% (3.7 ± 6.9 cells/mm²) for methotrexate and 0.07 ± 0.19% (0.1 ± 0.27 cells/mm²) for actinomycin D. Rabbit eyes treated with a mixture of methotrexate/actinomycin D showed no posterior capsule opacification at 4 months and a low opacification 6 months postoperatively. Without drug treatment low opacification starts 6 weeks postoperatively. CONCLUSIONS: The drug screening in the described ex vivo model can help to reduce the number of preclinical studies for secondary cataract prevention. The successful ex vivo cell ablation by methotrexate/actinomycin D was confirmed by a delayed in vivo secondary cataract formation.

7.1 T MRI to assess the anterior segment of the eye.

PURPOSE: Visualization of the anterior segment and biometric evaluation of the entire crystalline lens pose significant challenges for imaging techniques because of tissue-induced distortion artifacts. The present study was conducted to demonstrate the advantages of high-resolution magnetic resonance imaging (micro-MRI) for visualizing the anterior segment. METHODS: High-resolution MR ocular images were acquired on an ultra-high-field MR unit using a two-channel coil with four coil elements and T(2)-weighted turbo spin echo sequences ex vivo in pig, rabbit, monkey, and human donor eyes and in vivo in rabbits. Tissue heating, reproducibility, and signal-to-noise ratio were investigated in vivo. Monkey eye lens thickness (LT) was also measured using A-scan ultrasonography (US). RESULTS: Anterior segment details of phakic eyes were obtained ex vivo (pig, rabbit, monkey, and human donor eyes) with pixel matrix size 512 × 512 (in-plane resolution 80 × 80 µm) and in vivo (rabbit eyes) with pixel matrix size 320 × 320 (in-plane resolution 125 × 125 µm). Complete quantification of lens dimensions as they correlate with the sulcus-sulcus and angle-angle plane can be performed. In LT determinations in monkey eyes, no significant difference was detected between micro-MRI and A-scan US (P > 0.05, Mann-Whitney U test). Biometric analysis of one pseudophakic monkey eye confirmed the absence of relevant distortion artifacts. CONCLUSIONS: Micro-MRI allows ex vivo and in vivo visualization and quantification of the spatial arrangement of the anterior eye segment. Imaging of the retroiridian region, including the entire crystalline lens, overcomes a number of major limitations in the quantitative evaluation of the anterior segment.

Relationship between contrast sensitivity and spherical aberration: comparison of 7 contrast sensitivity tests with natural and artificial pupils in healthy eyes.

PURPOSE: To find a contrast sensitivity test that can be used clinically to evaluate interventions aimed at minimizing spherical aberration and determine the circumstances under which these tests should be performed. SETTING: Laboratory of Experimental Ophthalmology, University of Groningen, Groningen, The Netherlands. METHODS: Contrast sensitivity tests were performed using 2 experimental designs. Design 1 was with a natural pupil under mesopic and photopic conditions. Design 2 was with a 5.0 mm artificial pupil after cycloplegia under photopic conditions only. Two computerized tests (vertical sine-modulated gratings [VSG] and Holladay circular sine-modulated patterns [HACSS]) and 5 chart tests (Pelli-Robson, acuity-measuring letter charts at low contrast [2.5% and 10%], VectorVision, and edge contrast sensitivity) were used. Spherical aberration was assessed with a Hartmann-Shack wavefront analyzer. RESULTS: Forty-nine healthy subjects aged 20 to 35 years (n = 24) and 55 to 70 years (n = 25) participated. Design 2 showed a significant relationship between contrast sensitivity and spherical aberration with the HACSS at 3 cycles per degree (cpd) (P = .03) and 6 cpd (P = .01) and with the VSG at 6 cpd (P = .01). Design 1 yielded no significant relationships. CONCLUSIONS: Using an artificial pupil, a relationship between contrast sensitivity and spherical aberration was established with the VSG and HACSS tests but not with the chart tests. No test showed a relationship using natural pupils under either lighting condition. Chart tests are unsuitable for uncovering contrast sensitivity differences related to differences in spherical aberration, as typically found in healthy phakic eyes.

Development of a ciliary muscle-driven accommodating intraocular lens.

PURPOSE: To develop a ciliary muscle-driven accommodating intraocular lens (IOL) that has a large and predictable range of variable power as a step toward spectacle independence. SETTING: Department of Physics and Medical Technology, VU University Medical Center, Amsterdam, The Netherlands. METHODS: A concept IOL that has a rotating focus mechanism and a mechanical frame that can operate within the range of ciliary muscle contraction of a typical 60-year-old human eye was designed. Prototypes were made to test the IOL's mechanical performance in an enucleated pig's eye using a laboratory lens-stretching device that mimics the action of the human ciliary muscle. Changes in focal length during stretching were measured by laser-based ray tracing and a videocamera system. To rotate the 2 lenses in the IOL with variable optical power, a frame that allows the displacement and force of the ciliary muscle to be transferred by the capsular bag was designed. RESULTS: Ray tracing showed that the modulation transfer function (MTF) of the IOL in different accommodative states did not deviate to a great extent from the MTF of a monofocal IOL. During stretching experiments, the prototype IOL achieved 8.0 diopters of accommodation. CONCLUSIONS: Evaluation of an accommodating IOL that meets the requirements for a spectacle-independent solution to presbyopia showed that the mechanical and optical designs must be further optimized to improve optical quality and functionality.

Visualization of the retinal image in an eye model with spherical and aspheric, diffractive, and refractive multifocal intraocular lenses.

PURPOSE: To present a method that visually demonstrates how spherical, aspheric, diffractive, and refractive multifocal intraocular lenses (IOLs) process light received from the cornea. METHODS: Monochromatic green light was projected through an Average Cornea Eye (ACE) Model with a cornea in front of the IOL. The model simulates a human cornea with average spherical aberration and visualizes the converging bundle of light leaving the IOL. Additionally, a US Air Force target was projected through the model, and the projected (retinal) image was captured. Various IOLs of differing designs were evaluated using this test setup. Multifocal IOLs included the aspheric diffractive Tecnis ZM900 and ZMA00 lenses; the refractive ReZoom NXG1 lens; the spherical AcrySof ReSTOR SA60D3 apodized diffractive lens; and the spherical diffractive CeeOn 811E lens. Monofocal IOLs included the spherical CeeOnEdge 911A IOL and the aspheric SofPort LI61AO, AcrySof IQ SN60WF, and Tecnis Z9000 and ZA9003 IOLs. RESULTS: The light paths of the different diffractive and refractive multifocal IOLs showed the variations in the processing of incoming light, illustrating the functional differences of IOL concepts. The US Air Force target projections in the ACE Model gave an impression of the functional optical quality of the different lenses. The value of this visualization method was demonstrated by comparing the results with modulation transfer function measurements. CONCLUSIONS: This visualization technique furthers the understanding of the working principles and quality of the retinal images produced by different mono- and multifocal IOLs.

Changes in spherical aberration after lens refilling with a silicone oil.

PURPOSE: It may be possible to restore accommodation to presbyopic human eyes by refilling the lens capsular bag with a soft polymer. In the present study, optical changes were measured that occurred in a pig eye model after the refilling of the capsular bag. METHODS: The optical power and spherical aberration in 10 isolated pig lenses were measured under different conditions. They were first determined by using a scanning laser ray-tracing technique over an effective pupil size of 6 mm. Second, the contours of the anterior and posterior lens surface were photographed, and a mathematical ray-tracing was performed by using a polynomial fit through the digitized surface contours, to determine optical power and spherical aberration. Third, the lenses were refilled with a silicone oil until their preoperative lens thickness was reached, and scanning laser ray-tracing, contour photography, and mathematical ray-tracing were repeated. Comparisons between the measurements were made to determine how the change from a gradient refractive index to a homogeneous refractive index influenced spherical aberration. The influence of the change in lens contour on spherical aberration after lens refilling was also studied. RESULTS: The natural lenses had a higher lens power than the refilled lenses (49.9 +/- 1.5 D vs. 36.8 +/- 1.5 D; P < 0.001). Moreover, there was a change in sign from negative spherical aberration before lens refilling (-3.6 D) to positive spherical aberration after lens refilling (7.9 D; P < 0.001). The comparison between scanning laser ray-tracing of the natural lens and mathematical ray-tracing of the photographed surface contours of the natural lens to determine the effect of refractive index substitution (i.e., replacement of a gradient refractive index by a homogeneous refractive index) showed a significant change in spherical aberration from -3.6 +/- 2.0 to 11.0 +/- 2.1 D (P < 0.001). The change in lens contour did not result in a significant change in spherical aberration (P = 0.08) before and after lens refilling with an equal refractive index. CONCLUSIONS: The lower lens power of refilled pig lenses compared to natural lenses was due to the lower refractive index of the refill material. Refilling pig lenses with the silicone oil used in this study resulted in an increase in spherical aberration. This increase was mainly caused by the change from a gradient refractive index to a homogeneous refractive index. The change in lens curvature after lens refilling did not result in an increase in spherical aberration. The influence of lens refilling on spherical aberration of human lenses must be determined in similar experiments in human eyes.

Development of an accommodating intra-ocular lens--in vitro prevention of re-growth of pig and rabbit lens capsule epithelial cells.

Cataract surgery is routinely performed to replace the clouded lens by a rigid polymeric intra-ocular lens unable to accommodate. By implanting a silicone gel into an intact capsular bag the accommodating properties of the natural lens can be maintained or enhanced. The implantation success of accommodating lenses is hampered by the occurrence of capsular opacification (PCO) due to lens epithelial cell (LEC) growth. In order to prevent LEC proliferation, a treatment regime using actinomycin D, cycloheximide and water was developed. The effectiveness of treatment was analyzed using an in vitro, MTT-based cell culture system and an ex vivo pig eye model in which the implanted lens-in-the-bag is cultured as a whole. LEC were exposed to treatment solutions for 5 min, then the cells were allowed to recover and to re-colonize the substratum. MTT conversion by cells was transiently inhibited by cycloheximide dissolved in water and by water alone. Exposure to actinomycin D resulted in a lasting inhibition of MTT conversion and consequently cell proliferation. These in vitro data could not be fully reproduced in the ex vivo pig eye model due to essential differences between both models. Treatment with actinomycin D containing solutions, however, resulted in a nearly complete absence of cells on the capsular wall. The pig eye model is a promising approach to further evaluate the effects of peri-surgical treatment during the accommodating intra-ocular lens implantation.

Accommodative lens refilling in rhesus monkeys.

PURPOSE: Accommodation can be restored to presbyopic human eyes by refilling the capsular bag with a soft polymer. This study was conducted to test whether accommodation, measurable as changes in optical refraction, can be restored with a newly developed refilling polymer in a rhesus monkey model. A specific intra- and postoperative treatment protocol was used to minimize postoperative inflammation and to delay capsular opacification. METHODS: Nine adolescent rhesus monkeys underwent refilling of the lens capsular bag with a polymer. In the first four monkeys (group A) the surgical procedure was followed by two weekly subconjunctival injections of corticosteroids. In a second group of five monkeys (group B) a treatment intended to delay the development of capsular opacification was applied during the surgery, and, in the postoperative period, eye drops and two subconjunctival injections of corticosteroids were applied. Accommodation was stimulated with carbachol iontophoresis or pilocarpine and was measured with a Hartinger refractometer at regular times during a follow-up period of 37 weeks in five monkeys. In one monkey, lens thickness changes were measured with A-scan ultrasound. RESULTS: In group A, refraction measurement was possible in one monkey. In the three other animals in group A, postoperative inflammation and capsular opacification prevented refraction measurements. In group B, the maximum accommodative amplitude of the surgically treated eyes was 6.3 D. In three monkeys the accommodative amplitude decreased to almost 0 D after 37 weeks. In the two other monkeys, the accommodative amplitude remained stable at +/-4 D during the follow-up period. In group B, capsular opacification developed in the postoperative period, but refraction measurements could still be performed during the whole follow-up period of 37 weeks. CONCLUSIONS: A certain level of accommodation can be restored after lens refilling in adolescent rhesus monkeys. During the follow-up period refraction measurements were possible in all five monkeys that underwent the treatment designed to prevent inflammation and capsular opacification.

Artificial crystalline lens.

If presbyopia is caused by hardening of the crystalline lens, replacing it with a material with mechanical properties similar to the young crystalline lens should restore accommodative ability. Such a silicone material has been developed. Refilling the capsular bag with this material results in 3 to 5 D of accommodation in primates in response to pilocarpine.

Comparison of the accommodation theories of Coleman and of Helmholtz by finite element simulations.

PURPOSE: The accommodation process of the human eye is still a controversial subject. Coleman assumes that the lens, together with the zonula fibers, forms a diaphragm which is held in a catenary shape due to the pressure difference between the aqueous and vitreous body of the lens. The aim of the paper is to compare the results of two simulations (according to the Helmholtz and to the Coleman theories) with ultrasonographic data. METHODS: An axisymmetric static finite element model of the lens was generated using the literature data for geometry, material properties and loads. The refractive power of the lens was calculated for two different ages (29 and 45 years). RESULTS: The application of a pressure to the posterior lens surface did not yield an increase in refractive power change during accommodation. Rather a decrease in accommodation related refractive power was found. CONCLUSIONS: Physiologically relevant refractive power changes are obtained by a simulation in accordance with the Helmholtz theory. A simulation in accordance with the Coleman theory does not yield physiological values of refractive power change.

Relation between injected volume and optical parameters in refilled isolated porcine lenses.

PURPOSE: This study was performed to elucidate the correlation between added lens refill material and enhanced lens power as well as the correlation between lens refilling volume and accommodative amplitude as determined by equatorial stretching of ex vivo refilled pigs' lenses. METHODS: Nine porcine lenses were refilled with increasing amounts of silicone oil. After each refill step, the lens power, the lens power change, and the lens thickness were measured both in the relaxed state and with a 3-mm larger ciliary body diameter. In addition, the spherical aberration of the refilled lenses was also quantified. RESULTS: Injection of 0.04 mL silicone material into the relaxed lens enhanced the lens power by 1 D. A 0.54-mm increase of the lens thickness in relaxed lenses added 1 D to the lens power. Increasing the lens refilling volume decreased the lens power changes measured at 3-mm ciliary body stretch. Spherical aberration was positive in the refilled lenses and increased with increasing lens refilling volume. CONCLUSION: The correlation found between the refilling volume and the lens power (0.04 mL D(-1)), as well as the correlation between the lens thickness and the lens power (0.54 mm D(-1)), might be important factors to be controlled in conjunction with surgery, as these also determine the lens power in the presence of this refill material. An increasing lens filling volume is associated with decreasing accommodative amplitude. The positive spherical aberration of refilled porcine lenses presents a sharp contrast to the negative aberration of natural pigs' lenses. Different lens contours and the transition from a gradient to a homogeneous refractive index might be responsible for this change in spherical aberration.

Effect of infusion bottle height on lens power after lens refilling with and without a plug.

PURPOSE: To evaluate the influence of intraoperative infusion bottle height on the power of refilled pig lenses. SETTING: Research Laboratory, Pharmacia Intraocular Lens Manufacturing Plant, Groningen, The Netherlands. METHODS: This study comprised 2 groups of pig eyes. In 1 group, the lens was refilled with silicone oil using a plug to close the capsulorhexis; in the other group, no plug was used. The anterior chamber depth, lens thickness, and vitreous chamber depth were measured by A-scan ultrasound. The total refraction was measured with a Hartinger refractometer. Measurements were performed with the infusion bottle at 0 cm, 25 cm, 50 cm, 75 cm, and 100 cm above eye level. Calculations using a model eye were performed to evaluate the change in lens power based on empirical data. RESULTS: The mean change in the power of refilled lenses caused by varying the height of the infusion bottle was 1.8 diopters. Lenses refilled with a plug had a thickness similar to that of natural lenses. Lenses refilled without a plug were significantly thinner (P<.05). The power of lenses refilled with a plug was significantly higher that of lenses refilled without a plug (P<.05). CONCLUSIONS: During lens refilling, infusion bottle height influenced the resulting lens power. Using a plug to close the capsulorhexis resulted in refilled lens dimensions similar to those of the natural lens.

Polymer refilling of presbyopic human lenses in vitro restores the ability to undergo accommodative changes.

PURPOSE: Because presbyopia is thought to be accompanied by increased lens sclerosis this study was conducted to investigate whether refilling the capsule of the presbyopic human lens with a soft polymer would restore the ability of the lens to undergo accommodative changes. METHODS: Accommodative forces were applied to natural and refilled lenses by circumferential stretching through the ciliary body and zonular complex. Nine natural lenses and 10 refilled lenses from donors ranging in age from 17 to 60 years were studied. Two refill polymers with a different Young's modulus were used. The lens power was measured by a scanning laser ray-tracing technique, and lens diameter and lens thickness were measured simultaneously while the tension on the zonules was increased stepwise by outward pull on the ciliary body. RESULTS: In the natural lenses the older lenses were not able to undergo power changes with stretching of the ciliary body, whereas in the refilled lenses, all lenses showed power changes comparable to young, natural lenses. The refilled human lenses had a higher lens power than the age-matched natural lenses. The Young's modulus of the polymers influenced the lens power change when measured with the ciliary body diameter increased by 4 mm. CONCLUSIONS: Refilling presbyopic lenses with a soft polymer enabled restoration of lens power changes with mechanical stretching. Because sclerosis of the lens is an important factor in human presbyopia, refilling the lens during lens surgery for cataract could enable restoration of clear vision and accommodation in human presbyopia.

Monitoring accommodative ciliary muscle function using three-dimensional ultrasound.

BACKGROUND: Our objective was to develop a three-dimensional high-resolution ultrasonic imaging technique to be utilized for in-vivo characterization of the ciliary body and the posterior iris. The benefit of this imaging in enhancing the quantification of the configurational changes in the ciliary body during accommodation is demonstrated. METHODS: Sequential ultrasound biomicroscopic images of the ciliary body region were obtained with a computer-controlled scanning device designed for use with a standard ultrasound biomicroscope for 3D imaging. Custom-made software allows online data collection, data analysis and 3D reconstruction in conjunction with commercially available VoxelView software. RESULTS: The three-dimensional presentation allows a close approximation of the ciliary muscle inside the ciliary body in vivo. We are able to distinguish and to analyze the changes in the muscle contour in different accommodation states. During accommodation a shift in the ciliary muscle center of gravity in a range of 0.04-0.26 mm (mean 0.13+/-0.06 mm) in the direction of the lens equator, with an interindividual variation and a small decrease with age, was observed. CONCLUSIONS: High-resolution ultrasound is a well established technique for in-vivo investigation of the anterior segment. Three-dimensional ultrasound biomicroscopy allows an assessment of the individual ciliary muscle activity in consideration of the ciliary processes. In combination with a contour analysis tool we improved the muscle contour determination during different accommodation states. The investigation showed an activity of the ciliary muscle in young volunteers as well as those of presbyopic age.