Accurate determination of effective lens position and lens-capsule distance with 4 intraocular lenses

Effectiveness of prophylactic capsular tension ring implantation during cataract surgery in highly myopic eyes

PURPOSE

To assess the effectiveness of prophylactic capsular tension ring (CTR) implantation during cataract surgery in highly myopic eyes.

SETTING

Eye and Ear, Nose, and Throat Hospital of Fudan University, Shanghai, China.

DESIGN

Prospective cohort study.

METHODS

Consecutive highly myopic patients treated with cataract surgery were recruited and randomized to undergo CTR implantation or not. The outcomes compared between the 2 groups included axial lens position (ALP), intraocular lens (IOL) decentration and tilt, area of anterior capsule opening, severity of anterior capsular opacification (ACO), and posterior capsular opacification (PCO) at 1 year postoperatively.

RESULTS

A total of 55 highly myopic eyes with CTRs implanted and 55 without were included in the analysis. At 1 year postoperatively, no significant differences were detected between the CTR and non-CTR groups for the mean ALP, IOL decentration, or tilt (all P > .05). However, the CTR group had a significantly larger area of anterior capsule opening (23.62 ± 3.30 mm2 vs 21.85 ± 2.30 mm2, P = .003), and less severe ACO (P = .033) and PCO (PCO-3 mm: 0.06 ± 0.13 vs 0.13 ± 0.20, P = .038; PCO-C: 0.15 ± 0.18 vs 0.25 ± 0.26, P = .026) than the non-CTR group. The corrected distance visual acuity, prediction error, and higher-order aberrations did not differ between the 2 groups (all P > .05).

CONCLUSIONS

In highly myopic eyes, although prophylactic CTR implantation can reduce the severity of capsular contraction and opacification, it does not significantly affect postoperative IOL stability or visual outcomes.

Influence of Capsular Tension Rings on the IOL-Capsule Complex in Patients With Long Axial Length: A Clinical Observation Based on SS-OCT

PURPOSE

To evaluate the influence of a capsular tension ring (CTR) on the intraocular lens (IOL)-capsule complex after cataract surgery in patients with long axial length.

METHODS

This was a prospective study. Patients underwent phacoemulsification and IOL implantation, with or without CTR implantation. Swept-source optical coherence tomography was performed at 1 day, 1 week, 1 month, and 3 months postoperatively to determine the postoperative aqueous depth (PAD), capsular bend index (CBI), and IOL tilt and decentration. Spherical equivalent values were obtained through subjective refraction and autorefraction. Root mean square was adopted to evaluate the indices listed above.

RESULTS

Forty-three patients (56 eyes) were included in the study. Generalized estimating equation analysis of PAD showed a statistical difference between groups (P = .031). The RMS of the change in PAD was smaller in the CTR group than in the non-CTR group during the 3 months after surgery (P = .015). CBI in the CTR group increased more from 1 to 3 months after surgery than that in the non-CTR group (P = .025). The RMS of the change in vertical decentration was smaller in the CTR group than in the non-CTR group during the 3-month follow-up (P = .009).

CONCLUSIONS

CTR implantation can stabilize the axial position of the IOL within the capsular bag after cataract surgery in patients with long axial length without affecting the refractive stability. The formation of capsular bend may be slightly delayed in the early stage after CTR implantation, but it accelerates from 1 to 3 months after surgery. [J Refract Surg. 2024;40(9):e654-e661.].

Effect of capsular tension ring implantation on intraocular lens calculation formula selection for long axial myopia

PURPOSE

The study investigated the effect of capsular tension ring (CTR) implantation on postoperative refractive stability and accuracy of intraocular lens (IOL) formulas for axial length (AL) ≥ 27.0 mm patients.

METHODS

Prospective case series. The eyes of patients underwent phacoemulsification extraction combined with IOL implantation were classified as CTR implantation (A-CTR) and without CTR implantation (B-CON) groups. Refractive outcome and anterior chamber depth (ACD) were recorded at 1 week, 1 month, and 3 months post-operation. Prediction refractive error (PE) and absolute refractive error (AE) of each formula were calculated.

RESULTS

A total of 89 eyes (63 patients) were included and randomized into the CTR (A-CTR) and control groups (B-CON). Comparison of refraction at different postoperative times of the CTR group showed no statistical difference (all P > 0.05). The ACD in the A-CTR group gradually deepened, and that in the B-CON group gradually shallowed (all P > 0.05). The formulas' AE showed statistically significant differences in CTR and CON groups (P < 0.001). The PE of Hill-RBF 2.0 and EVO formulas in the A-CTR group were more hyperopic than that in the B-CON group (all P > 0.05), the other five formulas were more myopic in A-CTR group than that in the B-CON group (all P > 0.05).

CONCLUSION

Patients with 13 mm diameter CTR implantation tended to have stable refraction at 1 week post-surgery and 1 month for those without it. CTR of the 13 mm diameter had no effect on the selection of formulas. Additionally, it is found that Kane and EVO formulas were more accurate for patients with AL ≥ 27.0 mm.

Relationship Between Postoperative Intraocular Lens Shift and Postoperative Refraction Change in Cataract Surgery Using Three Different Types of Intraocular Lenses

Introduction

Understanding the relationship between postoperative intraocular lens (IOL) shift and refractive change is crucial for the accuracy of predicted postoperative refraction (PPR). We assessed the relationships between different IOL fixation methods, haptic designs, and several metrics.

Methods

Single-center, open-label study which included 69 eyes. We preoperatively measured the anterior chamber depth (ACD), lens thickness (LT), axial length (AL), and PPR. AcrySof IQ (n = 27) and FineVision (n = 24) were fixed in the bag, and FEMTIS (n = 18) was fixed in capsulorhexis. At 1 day, 1 week, and 1 month postoperatively, we checked the IOL position and refraction and compared the IOL shift, refraction change, and the margin of error of the predicted PPR (PR-PPR difference). We also analyzed the correlation between postoperative and preoperative variables.

Results

FEMTIS showed the highest stability in terms of IOL shift and refraction. The in-the-bag-fixated IOLs showed a significant forward shift between 1 day and 1 week postoperatively. There were significant differences in the PR-PPR difference between the IOLs. ACD and AL showed significant positive correlations, and LT showed a significant negative correlation with IOL shift and change in PR between 1 day and 1 week, but not between 1 week and 1 month postoperatively.

Conclusion

The relationship between postoperative IOL shift and refraction change varied according to IOLs with different haptic types. Capsulorhexis fixation may be more stable than in-the-bag fixation. Furthermore, preoperative ACD, LT, and AL may be useful factors to predict IOL shift, change in PR, and to a lesser extent the degree of the margin of error in clinical practice. Our findings may improve the accuracy of PPR and refractive outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40123-021-00390-x.

The Relationship Between the Change of Intraocular Lens Position and Capsular Bend After Cataract Surgery

PURPOSE

To explore the relationship between the change in intraocular lens (IOL) position and capsular bend after cataract surgery.

METHODS

Patients underwent phacoemulsification and IOL implantation (Alcon Laboratories, Inc). Patients were divided into two groups based on preoperative axial length: long axial length group (axial length ⩾ 26 mm) and normal axial length group (axial length > 22 but < 26 mm). Swept-source optical coherence tomography was performed at 1 day, 1 week, 1 month, and 3 months after mydriasis to obtain postoperative aqueous depth (PAD) and capsular bend index (CBI). The relationship between CBI and PAD changes was analyzed.

RESULTS

Eighty patients (80 eyes) were included in the study. PAD decreased gradually from 1 day to 1 week and increased from 1 week to 3 months. Mean CBI was moderately positively correlated with PAD changes (r = 0.586, P < .001). The IOL moved forward gradually when the CBI was less than 2.30 and the IOL gradually moved backward when the CBI was 2.30 or greater. The root mean square of the change in PAD was smaller in the long axial length group (0.08 ± 0.04 mm) than in the normal axial length group (0.09 ± 0.05 mm) during the 3 months after surgery (P = .036).

CONCLUSIONS

The position of the IOL was almost stable 1 month after operation, and postoperative capsule adhesion mainly occurred within 1 month. The change in PAD was related to capsule adhesion. The postoperative position of the IOL was relatively stable and capsular bend was relatively slow for the long axial length group over 3 months. [J Refract Surg. 2021;37(5):324-330.].

Correlation of Intraoperative Optical Coherence Tomography of Crystalline Lens Diameter, Thickness, and Volume with Biometry and Age

PURPOSE

To characterize crystalline lens dimensions derived from in vivo spectral-domain optical coherence tomography (SD-OCT) and identify associations among these parameters, ocular biometry, and age.

METHODS

In this retrospective study, lens thickness (LT), lens diameter (LD), and lens volume (LV) were measured intraoperatively using SD-OCT in 293 eyes undergoing lens surgery. Correlations among LT, LD, LV, age, axial length (AL), and anterior chamber depth (ACD) were analyzed. Multiple regression analysis was performed to determine whether a combination of biometric data could predict LD and LV.

RESULTS

Wide variations were observed in LT (3.6-5.7 mm), LD (7.5-11.9 mm), and LV (119.9-312.4 mm³) of aging eyes. Correlations among the 3 lens dimensions were statistically significant (LV-LT: r = 0.785; P < .001; LV-LD: r = 0.696; P < .001; and LT-LD: r = 0.121; P = .039). With age, the correlation coefficients of LT, LD, and LV were 0.526, 0.326, and 0.573, respectively (P < .001). Although there was significant correlation of AL with LT (r = -0.137; P = .002) and LD (r = 0.268; P < .001), it was not significant with LV (r = 0.084; P = .15). Subgroup analysis revealed that 19.8% of long eyes had LD >1 standard deviation (SD) above and that 5.2% had LD <1 SD below the mean LD.

CONCLUSIONS

Dimensions of the aging lens vary considerably and are most accurately characterized by direct measurement of LT, LD, and LV, rather than making assumptions based on AL. These findings challenge historically proposed relationships between LD and AL and represent a normative dataset of contemporary geometric features of the aging lens, possibly aiding in surgical decision making and future developments in lens surgery.

The effect of capsule tension ring on posterior capsule opacification: A meta-analysis

Background

Posterior capsule opacification is one of the most common complications after cataract surgery. Studies have suggested that the introduction of a capsule tension ring might play a critical role in the prevention of capsule opacification, yet quantitative evidence is still lacking. This work consists of a meta-analysis on available data in order to explore the influence of a capsule tension ring on posterior capsule opacification.

Methods

A comprehensive review of the literature on capsule tension ring and posterior capsule opacification was carried out using the Embase, Pubmed, Web of Science, and Cochrane electronic databases. The selected studies included randomized controlled trials, retrospective studies and prospective studies published before June 2020. The studies of interest were selected by two reviewers independently from the included studies. Odds ratios (ORs) and standardized mean differences (SMD) were used in order to assess the association. A fixed-effects model or a random-effects model was applied to combine data according to heterogeneities. Sensitivity analysis was used to assess the heterogeneity of the studies. Publication bias was estimated using the Egger test. Statistical analysis was performed using the stata15.1 software.

Results

The meta-analysis included in total 8 studies involving 379 cases and 333 controls. There was a statistically significant difference of Nd:YAG laser capsulotomy rate (OR=0.241, 95% CI: 0.145, 0.400 I²=42.1%) between the capsule tension ring group and the control group, indicating that the tension ring reduced the Nd:YAG laser capsulotomy rate. Further studies with continuous data also revealed that the use of capsule tension ring was associated with a lower posterior capsule opacification score (SMD = -1.402, 95% CI: -2.448, -0.355 I²=95.0%). The sensitivity analysis suggested that the result of the re-combined analysis did not change notably, indicating that the result was reliable and stable. Both pooled analysis showed no evidence of publication bias.

Conclusion

The findings of this meta-analysis confirmed that capsule tension ring might reduce capsule opacification. Further studies should be made to validate the result.

Effect of the capsular tension ring on refractive outcome after phacoemulsification

Purpose: To evaluate how capsular tension rings (CTR) affect refractive outcomes following cataract extraction by phacoemulsification complicated by zonular instability.

Study design: Retrospective.

Methods: In a retrospective case-control study, the 29 eyes of 29 patients with CTRs were compared with the 29 eyes of patients without zonular instability following routine phacoemulsification, with mean arithmetic refractive prediction error (ArRPE) and mean absolute refractive prediction error (AbRPE) as primary outcome measures.

Results: A comparison of eyes with and without CTRs according to the SRK/ T formula revealed no statistically significant difference in ArRPE (0.52 vs. 0.45 D, p = 0.570) or AbRPE (0.52 vs. 0.55 D, p = 0.799). Postoperative hypermetropic shift occurred in most cases in both groups, although the mean difference between eyes with CTR (22/ 29) and without CTR (25/ 29) was not statistically significant (p = 0.315).

Conclusion: Implanting CTRs did not consistently affect refractive outcomes versus routine phacoemulsification. Results suggest that intraocular lens power can be calculated as usual when CTRs are used.

Abbreviations: CTR = capsular tension ring, ArRPE = arithmetic refractive prediction errors, AbRPE = absolute refractive prediction errors, IOL = intraocular lens, WTW = white-to-white, ACD = anterior chamber depths, AL = axial lengths, RPE = refractive prediction error

Effect of capsular tension ring implantation on capsular stability after phacoemulsification in patients with weak zonules: a randomized controlled trial. CTR implantation in cataract patients with weak zonules

BACKGROUND

The use of capsular tension ring (CTR) implantation to treat cataract patients with weak zonules is still controversial. The aim of this study was to examine the effects of CTR implantation on capsular stability after phacoemulsification in patients with weak zonules, especially patients who have undergone pars plana vitrectomy (PPV) or those who suffer from severe myopia.

METHODS

A total of 42 patients who underwent phacoemulsification and received an intraocular lens (IOL) were randomized to undergo CTR implantation or not. The control and CTR groups were compared in terms of uncorrected distant visual acuity (UDVA), best corrected distant visual acuity (BCDVA), refractive prediction error, the area of anterior capsulorhexis, and IOL inclination angle. Follow-up visits were conducted postoperatively at 1 day, 1 week, 1 month and 3 months. Subgroup analyses were performed based on PPV and severe myopia.

RESULTS

Surgery significantly improved UDVA and BCDVA to similar extents in CTR and control patients, and refraction prediction error was similar between the two groups at all follow-up times. At 3 months after surgery, the area of anterior capsulorhexis was significantly larger in CTR patients than in controls (p = 0.0199). These differences were also significant between the subgroups of patients with severe myopia. Vertical IOL inclination was less within CTR groups at 3 months after surgery, especially in patients with severe myopia (p = 0.0286). At 1 week postoperatively, the proportion of individuals whose posterior lens capsule that had completely adhered to the posterior IOL surface was significantly higher among CTR patients (p = 0.023). No serious surgical complications were observed.

CONCLUSION

CTR implantation can benefit cataract patients with weak zonules by maintaining the shape of the capsular bag, reducing capsule shrinkage and stabilizing IOL inclination.

TRIAL REGISTRATION

Chinese Clinical Trial Registry ChiCTR-INR-17011217 , date of registration April 22, 2017, prospectively registered.

[Algorithm for predicting axial displacement of the optic part of IOL after phacoemulsification]

PURPOSE

To test a prediction algorithm for deflection of the optical part of IOL after uncomplicated phacoemulsification.

MATERIAL AND METHODS

The study included 226 patients (287 eyes) who underwent phacoemulsification with implantation of intracapsular AcrySof IOL. Preoperative examination included IOLMaster, Lenstar LS 900 biometry and Pentacam HR keratotopography. All measurement were repeated one month postoperatively. To determine the tilt and deflection of the IOL's optical part, anterior segment optical coherence tomography (OCT) was performed on Topcon 3DOCT-2000.

RESULTS

OCT data analysis helps identify the slope and deflection of the IOL's optical part relative to the pupil plane. In the previous study we built logistic regression models for predicting the deflection of the IOL's optical part with high predictive quality based on the calculated IOL power and preoperative biometry measurements. When checked with new patient data, the areas under the ROC curves have changed slightly. Large area under the ROC curves with small deviation rates, as well as retention of the level of true positive responses with little increase in false negative responses verify the high quality of the models.

CONCLUSION

Logistic regression models based on the optical power of the implanted IOL, as well as on a combination of preoperative biometry data from IOLMaster and Lenstar LS 900, make it possible to predict the probability of deflection of the optical part of IOL with high reliability and promptly correct the IOL power.

Intraoperative optical coherence tomography measurements of aphakic eyes to predict postoperative position of 2 intraocular lens designs

PURPOSE

To evaluate intraoperative anterior chamber depth (ACD) measurements of the aphakic eye to predict the postoperative ACD and compare 2 intraocular lens (IOL) designs.

SETTING

Hanusch Hospital, Vienna, Austria.

DESIGN

Prospective study.

METHODS

In this prospective study, patients scheduled for cataract surgery received a plate-haptic IOL (Asphina, Carl Zeiss Meditec AG) or an open-loop haptic IOL (ZCB00, Johnson & Johnson). Preoperatively, optical biometry (IOLMaster 700, CZM, or Lenstar, Haag-Streit) was performed. Intraoperatively, a prototype setup was used to perform time-domain OCT scans of the anterior eye segment (Visante connected to OPMI Lumera 200, both CZM). The intraoperative ACD was measured and used to predict the postoperative IOL position. Optical biometry and subjective refraction and autorefraction (RM 8800, Topcon) were performed 2 months postoperatively.

RESULTS

The study comprised 203 eyes of 203 patients. A partial least-square regression model for ACD generated 2 months postoperatively showed that the predictive power of the intraoperative ACD (0.48) was highest followed by the axial eye length (0.45) and then the preoperatively measured ACD (0.30). These findings were confirmed in a bootstrapping model. Regression models combining the preoperative ACD and intraoperative ACD resulted in further significant improvement.

CONCLUSIONS

Intraoperative ACD measurements predicted the postoperative position of open-loop IOLs and plate-haptic IOLs better than preoperative ACD measurements. Combining preoperative and intraoperative ACD measurements further improved the prediction.

Prevention of postoperative capsular bag opacification using intraocular lenses and endocapsular devices maintaining an open or expanded capsular bag

Postoperative capsule opacification is a multifactorial physiological consequence of cataract surgery that remains the most common complication of this procedure. A literature review that included several intraocular lenses (IOLs) and endocapsular devices studied in our laboratory found that devices maintaining the capsular bag in an open or expanded state were associated with improved bag clarity. This observed effect likely occurs secondary to the complex interactions of myriad mechanisms, which include formation of a barrier to lens epithelial cell (LEC) migration, mechanical compression of residual LECs, mechanical stretch at the level of the capsule equator, maintenance of overall bag contour, and enhanced endocapsular circulation of aqueous humor. We review the designs of endocapsular devices and IOLs that minimize the degree of postoperative capsule opacification by preventing capsular bag collapse and discuss the underlying mechanisms that contribute to this phenomenon.

FINANCIAL DISCLOSURE

None of the authors has a financial or proprietary interest in any material or method mentioned.

A study to evaluate whether CTR increases refractive unpredictability between predicted and actual IOL position

BACKGROUND

The surgical management of cataract associated with extensive zonular loss presents a challenge for ophthalmic surgeon. Capsular Tension Ring (CTR) is commonly being used to stabilize the capsular bag in patients with zonular dialysis. CTR helps to avoid capsular collapse and vitreous presentation in AC during surgery and maintains the capsular bag, allowing the circular contour of the capsular bag, allowing intra ocular lens to be easily placed in the bag. The aim of the study was to know if there is any shift of IOL following use of CTR ring.

METHOD

We did a Ultrabiomicroscopy (UBM) examination to find out shift in PCIOL in cases in which CTR ring and compared it with cases without CTR ring.

RESULT

It was found out through UBM in this study that there is actually a posterior shift of PCIOL after use of CTR ring leading to hypermetropic correction needed after surgery.

CONCLUSION

It is suggested that posterior shift of IOL following use of CTR should be kept in mind and the IOL implanted should be of + 1.0 to 2.0 D more than that calculated preoperatively.

Effect of primary posterior continuous curvilinear capsulorrhexis with posterior optic buttonholing on pilocarpine-induced IOL shift

PURPOSE

To assess intraocular lens (IOL) shift along the visual axis induced by ciliary muscle contraction with pilocarpine after cataract surgery and to compare primary posterior continuous curvilinear capsulorrhexis (CCC) and posterior optic buttonholing with IOLs implanted in the bag.

SETTING

Department of Ophthalmology, Medical University of Vienna, Vienna, Austria.

DESIGN

Clinical trial.

METHODS

Eyes with age-related cataract had cataract surgery with implantation of a nonaccommodating IOL (AF-1 YA-60BB). Surgery was performed with primary posterior CCC and posterior buttonholing in 1 eye (study eyes) and with conventional in-the-bag implantation in the contralateral eye (control eyes). After a minimum of 6 months postoperatively, the anterior chamber depth was assessed with partial coherence interferometry before and after application of pilocarpine 2.0% and, after a washout interval of 1 week, before and after the application of cyclopentolate 1.0%.

RESULTS

Forty eyes of 20 patients were enrolled. A slight backward shift of the IOL (+78 μm) in study eyes and in control eyes (+118 μm) was detected after pilocarpine application (both P<.05). No significant difference in IOL shift was found between study eyes and control eyes (P=.19).

CONCLUSIONS

Combined primary posterior CCC and posterior optic buttonholing did not affect IOL shift during pharmacologically stimulated ciliary muscle contraction compared with in-the-bag implanted IOLs. Capsule fibrosis diminished with primary posterior CCC but did not seem to be the only limiting factor in the accommodative IOL shift.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Reproducibility of intraocular lens decentration and tilt measurement using a clinical Purkinje meter

PURPOSE

To determine the reproducibility of intraocular lens (IOL) decentration and tilt measurements with a new Purkinje meter instrument.

SETTING

Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom.

METHODS

After pupil dilation, images of pseudophakic eyes with a plate-style IOL (Akreos Adapt) were obtained using a recently developed Purkinje meter. Intraocular lens decentration and tilt were evaluated by analyzing the captured images using a semiobjective method by marking the reflexes in the images and automatic calculation using a dedicated software program. In study 1, examiner 1 examined the eyes first followed by examiner 2. Ten minutes later, examiner 1 performed a second measurement, after which the intraexaminer and interexaminer reproducibility were determined. In study 2, a Purkinje meter was used to measure pseudophakic eyes with slitlamp finding of clinical IOL decentration, IOL tilt, or both. The results were compared with retroillumination photographs and slitlamp findings.

RESULTS

In study 1, there was high intraexaminer reproducibility for decentration (r = 0.95) and tilt (r = 0.85) and high interexaminer reproducibility for decentration (r = 0.84) and tilt (r = 0.75). In study 2, even in extreme cases of decentration and/or tilt, the Purkinje meter measurements were possible and appeared to correlate well with slitlamp findings.

CONCLUSIONS

Acquisition of images in pseudophakic eyes with the Purkinje meter was simple and rapid. The method was highly reliable for 1 examiner and between 2 examiners.

Intraocular lens stability and refractive outcomes after cataract surgery using primary posterior continuous curvilinear capsulorrhexis

PURPOSE

To evaluate the amount of intraocular lens (IOL) decentration and refractive changes after cataract surgery using posterior continuous curvilinear capsulorrhexis (PCCC).

DESIGN

Prospective comparative case series.

PARTICIPANTS

We included 86 eyes of 77 patients who had cataract surgery using PCCC (the PCCC group), and 79 eyes of 68 patients treated without PCCC (the control group).

METHODS

Foldable IOLs with polymethylmethacrylate haptics (VA-60BB, Hoya Corporation, Tokyo, Japan) were implanted in both groups. The best-corrected visual acuity (BCVA) was assessed. Automated refractokeratometry, Scheimpflug imaging (Pentacam; Oculus, Wetzlar, Germany), and slit-lamp photography with retroillumination were performed at each follow-up visit over 6 months. The axial shift of each IOL was measured as the distance between the corneal endothelium and the anterior surface of the IOL on Scheimpflug images. The horizontal shift was assessed as the distance between the geometric center of the IOL and the centers of the pupil and the limbus.

MAIN OUTCOME MEASURES

Best-corrected visual acuity, horizontal and axial shift of the IOL, and automated refraction.

RESULTS

There was no difference between the 2 groups in the mean BCVA before surgery and at any postoperative follow-up. The mean horizontal shift of the IOL after 6 months was 0.25 ± 0.14 mm for the pupil and 0.31 ± 0.17 mm for the limbus in the PCCC group (P = 0.315), and 0.26 ± 0.09 mm and 0.31 ± 0.13 mm, respectively, in the control group (P = 0.115). These were not different from the measurement on the postoperative day 1 (P = 0.515, P = 0.263, P = 0.421, and P = 0.875, respectively). At each follow-up visit over 6 months, there was no difference in the horizontal shift between the 2 groups (P > 0.05). The IOL shifted insignificantly in the PCCC group (-0.08 ± 0.24 mm anterior shift), but the shift was significant in the control group (-0.42 ± 0.27 mm anterior shift; P = 0.009). The mean postoperative refractive shift 6 months after surgery compared with refraction on the first day after surgery was -0.16 ± 0.67 diopter (D) in the PCCC group and -0.60 ± 0.70 D in the control group (P = 0.042).

CONCLUSIONS

During cataract surgery, PCCC is useful to stabilize and minimize postoperative refractive changes. The IOL displacement attributable to capsular contraction is less when cataract surgery involves PCCC.

Optical coherence tomography - development, principles, applications

This paper presents a review of the development of optical coherence tomography (OCT), its principles and important applications. Basic OCT systems are described and the physical foundations of OCT signal properties and signal recording systems are reviewed. Recent examples of OCT applications in ophthalmology, cardiology, gastroenterology and dermatology outline the relevance of this advanced imaging modality in the medical field.

Bilateral intraocular lens subluxation secondary to haptic angulation

An 82-year-old man had uneventful phacoemulsification with bilateral implantation of a hydrophilic acrylic, single-piece intraocular lens (IOL) (ACR6D SE, Laboratoires Cornéal). Five years later, simultaneous and bilateral IOL subluxations occurred. In both eyes, the subluxation was situated on the side of one haptic that had moved forward (temporal area in the right eye and superior area in the left eye). In the right eye, the haptic-capsular bag was entrapped by the pupil and produced endothelial damage. A transscleral suture was placed over and under the subluxated haptic through the anterior and posterior capsules to capture the haptic. The haptic was then sutured to the sclera. No postoperative complications developed. We hypothesize that 10-degree angulated and broad haptic junctions can lead to zonular damage and IOL subluxation.

Intraocular pressure rise after primary posterior continuous curvilinear capsulorhexis with a fixed dorzolamide–timolol combination

PURPOSE

To assess the safety, in terms of the intraocular pressure (IOP), of cataract surgery with primary posterior continuous curvilinear capsulorhexis (PPCCC) and a postoperative dose of a fixed dorzolamide-timolol combination and evaluate the effect of intraocular lens (IOL) haptic angulation.

SETTING

Department of Ophthalmology, Medical University of Vienna, Vienna, Austria.

METHODS

In this prospective randomized double-masked bilateral study, 88 eyes of 44 consecutive patients with age-related cataract were included in an intraindividual comparison study. All patients had standardized cataract surgery with PPCCC and IOL implantation in the capsular bag followed by a postoperative dose of a fixed dorzolamide-timolol combination. Patients were randomly assigned to receive an ACR6D SE IOL (Laboratoires Cornéal) in 1 eye and a Centerflex (C-flex) 570C IOL (Rayner Surgical GmbH) in the contralateral eye. The IOP was measured at baseline and postoperatively at 6 and 24 hours as well as 1 week.

RESULTS

Intraindividual comparison showed statistically significantly higher IOP measurements in the C-flex 570C nonangulated IOL group than in the ACR6D SE angulated IOL group at 24 hours (P = .003) and 1 week (P = .043). The highest IOP spikes (34 mm Hg) were at 6 hours in 2 eyes with a C-flex 570C IOL. The ACR6D SE group had statistically significant changes in IOP between preoperative and all postoperative time points. In the C-flex 570C group, the only statistically significant change in IOP was between preoperatively and 6 hours postoperatively.

CONCLUSIONS

Cataract surgery with PPCCC was safe in terms of the postoperative IOP course. Haptic angulation slightly decreased the overall IOP rise and the incidence of IOP rises above 30 mm Hg.

Anterior capsule cover and axial movement of intraocular lens

PURPOSE

To measure optic shift (OS) of a single piece monofocal intraocular lens (IOL) with varying relationships between anterior capsule cover and IOL optic.

METHODS

This is a prospective randomized masked study of 150 eyes undergoing phacoemulsification. Eyes received either option: 360 degrees total capsule cover (group I); partial cover (group II); or no cover (group III). OS was calculated as difference in anterior chamber depth after administration of cyclopentolate 1% and pilocarpine 2% on IOLMaster at separate visits at 6 months follow-up. Subsequently, using retro-illumination photographs, percentage area of capsule cover was calculated. OS within and between groups I and II was analyzed. The impact of one quartile change in area of capsule cover on percentage change in OS was measured for both groups. Unpaired t-test, correlation, and regression were applied.

RESULTS

In groups I, II, and III, mean age of patients was 56.68+/-6.38, 57.09+/-7.34, 59.15+/-6.35 years, respectively; mean OS (mm) was 1.25+/-0.28, 1.20+/-0.24; 0.95+/-0.26 (P=0.013), respectively; and percentage area of capsule cover (%) was 47.35+/-10.48, 33.83+/-10.11, 0.16+/-0.13 (P=0.001), respectively. Mean percentage area of capsule cover in group I vsgroup II was significant (P=0.001). OS was 1.22+/-0.26 mm in groups I and II (combined) vs0.95+/-0.26 mm in group III (P=0.004, (0.06, 0.33)). OS in group I vsgroup II was not significant (P=0.46). Correlation coefficient was r=0.38 (P<0.001). With every increment on quartile (a quartile is any of the three values which divide the sorted data set into four equal parts, so that each part represents one-fourth of the sample or population) class of area of capsule cover the OS increased by 0.12 mm.

CONCLUSION

The OS differed significantly between total and partial cover groups combined vsno cover group.

Effects of change in intraocular pressure on axial eye length and lens position

PURPOSE

To quantify the biometric changes of ocular dimensions with mechanical elevation of intraocular pressure (IOP) in vivo, to get a better understanding of the elastic properties of the human ocular structures that may play a role in the pathogenesis of various diseases such as myopia or glaucoma.

METHODS

Changes in IOP were induced by a suction cup in 18 eyes under cycloplegia. Axial eye length (AEL) and anterior chamber depth (ACD) were measured with non-invasive laser interferometry during elevation of the IOP 10 and 20 mmHg over baseline values and after a 10-min resting period.

RESULTS

IOP elevation of 10 and 20 mmHg respectively caused a significant increase of AEL of 23 mum (95% confidence interval: 14-34 microm) and 39 microm (confidence interval (CI): 28-51 microm). After mechanical oculopression, which resulted in an IOP reduction of -5.1 mmHg (CI: -6.3 to -4.0 mmHg) vsbaseline, a significant shortening of -7 microm (CI: -13 to 0 microm) was observed. The change in AEL correlated with the change in IOP (r=0.66, P=0.005). Furthermore, a significant increase in ACD of 30 microm (CI: 24-36 microm) was detected with IOP reduction after oculopression, but no change was seen during IOP elevation.

CONCLUSIONS

Biometric changes of the human eye as a response to IOP changes were assessed in vivo. The correlation between change in AEL and IOP found emphasizes the need of in vivoocular rigidity measurements in the human eye.

Routine posterior optic buttonholing for eradication of posterior capsule opacification in adults: report of 500 consecutive cases

PURPOSE

To study the efficacy of posterior optic buttonholing (POBH) through a primary posterior capsulorhexis (PPCCC) to preserve full capsular transparency, and its potential as a routine alternative to standard in-the-bag implantation of sharp-edged optic intraocular lenses (IOLs).

SETTING

Department of Ophthalmology, Medical University of Vienna, Vienna, Austria.

METHODS

After standard cataract removal, a PPCCC 4.0 to 5.0 mm in diameter was performed and the optic of a 3-piece IOL buttonholed posteriorly. One third of the eyes additionally had extensive anterior capsule polishing. All surgeries were performed under topical anesthesia.

RESULTS

The first 500 consecutive surgeries were evaluated. In 11 eyes, POBH was not performed as planned. In 4 cases, anterior capsulorhexis fixation of the optic was used as an alternative. In the early series, vitreous entanglement was seen in 5 eyes, of which 1 case prompted translimbal anterior vitrectomy. No case of cystoid macula edema was observed. One case of peripheral retinal detachment in a highly-myopic eye 4 months postoperatively appeared to be unrelated to the surgery. All lenses were well-centered without tilt, and both capsule leaves remained clear especially after additional polishing.

CONCLUSION

Posterior optic buttonholing precludes lens epithelial cells from accessing the retrolental space. The sandwiched posterior capsule blocks optic contact and thus fibrosis of the anterior capsule. Posterior optic buttonholing avoids after-cataract independent of optic edge design. Anterior capsule polishing adds to its efficacy by excluding any residual fibrosis. Surgery under topical anesthesia was well-controlled and safe. Posterior optic buttonholing may become a routine alternative to standard in-the-bag IOL implantation when supported by a longer follow-up.

A comparison of accommodation amplitudes in pseudophakic eyes measured with three different methods

PURPOSE

To compare the accommodative amplitudes with three different methods in pseudophakic eyes with different types of intraocular lenses (IOLs).

METHODS

Fifty-one pseudophakic eyes of 44 patients (age: 72.02+/-8.53 years) were studied. One of two different types of IOL were implanted (N=30, three-piece Alcon Acrysof MA60AC and N=21, one-piece Alcon Acrysof SA60AT) in-the-bag after standard phacoemulsification. The time of the examinations was 13.85+/-7.35 months postoperatively. We measured the amplitude of accommodation with three different methods: (1) subjective minus-lenses-to-blur method; (2) a new optical device (ACMaster, Carl Zeiss, Jena, Germany) using partial coherence interference (PCI) technique under physiological stimulus; and (3) objective anterior chamber depth measuring with a standard A-scan ultrasonic device (Ultrascan Imaging System, Alcon Laboratories, Forth Worth, TX, USA) before and after pharmacological relaxation of ciliary muscle.

RESULTS

We measured -0.83+/-0.63 D amplitude of accommodation with subjective minus-lenses-to-blur method. The IOL position did not change significantly during physiological accommodation effort measured with PCI method (-0.026+/-0.134 mm). The change in the IOLs position between near fixating and after ciliary muscle relaxation was -0.18+/-0.28 mm measured with ultrasound. There were no significant differences between values of one-piece and three-piece IOL groups.

CONCLUSION

The amplitude of accommodation measured by subjective and objective methods are different and are not comparable with each other. We did not observe any difference between values of examined two types of IOLs.

Pharmacological-induced Haptic Changes and the Accommodative Performance in Patients With the AT-45 Accommodative IOL

PURPOSE

To investigate the accommodative performance of the AT-45 (eyeonics Inc, Aliso Viejo, Calif) using three-dimensional ultrasound biomicroscopy.

METHODS

The AT-45 haptic region was visualized in vivo 1 month after surgery in four patients using an in-house developed three-dimensional ultrasound biomicroscope. Haptic changes, axial shift, and accommodation amplitude were determined under pharmacologically induced accommodation.

RESULTS

The angulation, depending on the accommodation state, could be distinguished and analyzed. In vivo a mean change in haptic angulation of 3.3 +/- 3.3 degrees (range: 0 degrees to 7 degrees) and a mean forward shift of 0.13 +/- 0.08 mm (range: 0.05 to 0.2 mm) were observed for the AT-45 using pharmacologically induced accommodation. A mean accommodative amplitude of 0.44 +/- 0.24 diopters (D) (range: 0.25 to 0.75 D) was found using a Hartinger coincidence refractometer.

CONCLUSIONS

Minimal angulation changes and axial movements of the AT-45 have been demonstrated using pharmacological stimulation and objective measurement methods. The mechanical performance of the AT-45 in these eyes does not appear to provide the range of accommodation necessary for close work.

Evaluation of biometric methods for measuring the anterior chamber depth in the non-contact mode

PURPOSE

High-resolution biometry of the anterior ocular segment is now becoming more and more important against a background of refractive surgery and the evaluation of potentially accommodative lens replacement materials. The aim of this study was a systematic investigation of the currently available non-contact methods for measuring the anterior chamber depth (ACD).

METHODS

The ACDs of 50 phakic eyes of 27 patients aged between 19 and 59 years were measured with the IOL-Master (Zeiss), the AC-Master (Zeiss), the Pentacam (Oculus) and slit-lamp pachymetry by Jaeger (Haag-Streit).

RESULTS

The median anterior chamber depth in the investigated eyes was 3.63 mm for the IOL-Master (minimum 2.88 mm, maximum 4.22 mm), 3.802 mm for the AC-Master (2.816 mm-4.373 mm), 3.915 mm for the Pentacam (minimum 2.994 mm, maximum 4.614 mm) and 3.75 mm for Jaeger (2.887 mm-4.29 mm). With a probability of error of alpha=0.05 there were no significant differences concerning the ACD between the methods of Jaeger and AC-Master, Jaeger and IOL-Master, or Pentacam and AC-Master (Wilcoxon and Wilcox). The intra-individual variability was +/-5.4 microm for AC-Master, +/-12.7 microm for Pentacam, +/-24.5 microm for IOL-Master and +/-41.2 microm for Jaeger. The maximum method-dependent difference in ACD determination was 285 microm.

CONCLUSIONS

All the methods allow non-contact biometry, but the results might differ due to measuring principles inherent to the system, experience of the examiner and compliance of the patient. Partial coherence interferometry with the AC-Master offers the advantage of measurement exactly along the optical axis with the highest reproducibility and patient compliance.

Pilocarpine-induced shift of an accommodating intraocular lens: AT-45 Crystalens

PURPOSE

To measure the shift of an accommodating plate-haptic intraocular lens (IOL) along the visual axis induced by ciliary muscle contraction after application of pilocarpine.

SETTING

Department of Ophthalmology, Medical University of Vienna, Vienna, Austria.

METHODS

Fifty-four eyes of 28 patients with age-related cataract comprised this prospective study. Each patient received an AT-45 silicone accommodating IOL (Crystalens, Eyeonics Corp.) after standardized cataract surgery. In a subgroup of 24 eyes, capsular bag fibrosis was reduced by extensive polishing of the anterior capsule with a slit cannula. Assessment included measurements of anterior chamber depth, assessed with partial coherence interferometry, before and after application of pilocarpine 2% and evaluation of near visual acuity 1 month and 3 months postoperatively.

RESULTS

A slight backward shift of the IOL of 151 mum in the nonpolished group (P < .001) and 122 mum in the polished group (P < .005) could be detected after application of pilocarpine. Polishing the capsule did not influence IOL shift. The median near visual acuity with distance correction 1 month and 3 months postoperatively was J5 and J4, respectively, in the nonpolished group and J6 at both times in the polished group.

CONCLUSIONS

Pilocarpine induced a counterproductive active backward shift of the AT-45 IOL. Polishing of the capsular bag had no impact on accommodative ability. The reading performance of patients with the AT-45 IOL patients at 1 and 3 months was not significantly different from that of with a standard IOL under similar testing methods.

Comparison of pilocarpine-induced and stimulus-driven accommodation in phakic eyes

With the recent introduction of potentially accommodative intraocular lenses (IOL), there is a need for methods to evaluate their accommodative potential. In most studies assessing IOL movement, pilocarpine is used to stimulate contraction of the ciliary muscle. The aim of this study is to determine if pilocarpine-induced ciliary muscle contraction is comparable to physiological stimulus-driven accommodation in young and presbyopic subjects. Ten emmetropic young subjects (23-25 years) and 11 emmetropic presbyopic subjects (51-62 years) were included in this study. Anterior chamber depth (ACD) and lens thickness (LT) were assessed with partial coherence interferometry (PCI). A moveable stimulus was coupled to the PCI equipment for measurement of biometric lens changes. ACD was measured with the stimulus at infinity and then at the subjects individual nearpoint, and after application of two drops of 2% pilocarpine. In young subjects, there was no significant difference in lens change between nearpoint and pilocarpine stimulation. Presbyopic subjects showed no relevant lens change when accommodating at the nearpoint, however, under pharmacologically induced ciliary muscle contraction with pilocarpine, there was a significant forward shift of the anterior and posterior lens pole, leading to a translational forward lens shift of about 150 microm. This study demonstrates that pilocarpine acts "physiologically" in young phakic subjects, but is a "superstimulus" in presbyopic phakic subjects. Therefore, IOL movement may be overestimated when using pilocarpine to stimulate accommodation.

Experimental evaluation of the Corneal Concept 360 intraocular lens with the Miyake-Apple view

PURPOSE

To evaluate a new single-piece, hydrophilic acrylic intraocular lens (IOL) designed to keep the anterior capsule away from the IOL optic, create the effect of a capsular tension ring, and prevent posterior capsule opacification (PCO).

SETTING

John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.

MATERIALS AND METHODS

Four Concept 360 IOLs (Corneal Laboratoire) were implanted in 4 human cadaver eyes of various sizes (Miyake-Apple technique). Lens centration, ovalization of the capsular bag and capsulorhexis opening, distance between the anterior optic surface and the anterior capsule and between the posterior optic surface and the posterior capsule, as well as presence of capsular striae were evaluated. The capsular bag was stained with trypan blue, and the ophthalmic viscosurgical device (OVD) was stained with fluorescein to enhance visualization.

RESULTS

In each eye, the lens conformed to the capsular bag with precise centration. No ovalization or distortion of the capsular bag or the capsulorhexis and no posterior capsule striae were observed. Measurements of the capsulorhexis diameter before and after IOL implantation were the same. The anterior capsule remained at distance from the anterior optic surface for 360 degrees, and tight contact between the posterior optic edge and the posterior capsule was observed.

CONCLUSIONS

Use of the Miyake-Apple technique is useful in the evaluation of new IOL designs in experimental studies. Design features of the Concept 360 IOL are likely to decrease the outcome of postoperative capsular bag opacification. Long-term clinical studies are necessary to confirm these findings.

3D-ultraschallbiomikroskopische Untersuchungen zur Differenzierung der Haptiken von potenziell akkommodationsf�higen Intraokularlinsen

PURPOSE

The principal ability of potentially accommodative IOLs is based on an axial shift of the IOL optics induced by the ciliary body action in interaction with a reversible change in haptic angulation. The aim of this study was to investigate the accommodative performance of this new IOL generation.

METHOD

The authors have designed a test device to study IOL performance experimentally. These results were extrapolated to the in vivo situation in patients with accommodative implants.

RESULTS

The 3D high-resolution presentation of the anterior segment of the eye allows a separation of the IOL haptic elements. In vitro and in the selected in vivo cases a change in haptic angulation <10 degrees in combination with a maximal IOL shift of 0.5 mm was found.

CONCLUSIONS

The simulation model used in combination with 3D ultrasound biomicroscopy provides information about the potential of accommodative IOL designs. Conclusions corresponding to changes in haptic angulation during accommodation can be drawn and applied to the in vivo situation.

Stimulus-driven versus pilocarpine-induced biometric changes in pseudophakic eyes

PURPOSE

Most trials that study the lens movement of accommodative intraocular lens (IOLs) use pilocarpine to stimulate ciliary muscle contraction. The aim of this study is to assess in vivo whether a more physiologic, stimulus-driven accommodation is comparable to pilocarpine-induced IOL movement.

DESIGN

Controlled patient- and examiner-masked clinical trial.

PARTICIPANTS

The study population included 38 eyes with accommodative IOL implants (1CU) and a control group of 28 eyes with conventional open-loop IOLs.

METHODS

A high-precision biometry technique, partial coherence interferometry, was used to measure IOL position. Anterior chamber depth was measured during physiologic (near point) and pharmacological (pilocarpine 2%) stimulation. In a subgroup of 14 1CU eyes, IOL position was determined repeatedly within 90 minutes after pilocarpine administration. A different subgroup was investigated as to the effect of cyclopentolate on IOL position. Best-corrected distance visual acuity (VA), best-corrected near VA, and distance-corrected near VA (DCNVA) were assessed using logarithm of the minimum angle of resolution charts.

MAIN OUTCOME MEASURES

Anterior chamber depth change under pilocarpine and near-point-driven accommodation.

RESULTS

Near-point accommodation did not induce movement of either the accommodating 1CU or the control IOLs. Pilocarpine induced a 201+/-0.137-mm anterior movement of the 1CU IOL (P<0.001), compared with no movement within the control IOL groups (P>0.05). There was no significant (P>0.05) difference in DCNVA between the accommodative and open-loop IOLs. No correlation between near point- or pilocarpine-stimulated IOL movement and DCNVA was found. Concerning the time course of movement after pilocarpine administration, most of the 1CU IOLs showed some movement 30 minutes after application. Cyclopentolate-induced ciliary muscle relaxation caused a posterior IOL movement, as compared with the relaxed state, when focusing on a distant target.

CONCLUSION

Pilocarpine-induced ciliary muscle contraction seems to overestimate IOL movement relative to a monocular near-driven stimulus. Therefore, concerning IOL movement, pilocarpine may act as a superstimulus and may not adequately simulate daily life performance of accommodative IOLs. However, it may be helpful to evaluate the maximum potential of an accommodating IOL.

Change in IOL position and capsular bag size with an angulated intraocular lens early after cataract surgery

PURPOSE

To investigate the axial movement in the first postoperative week and the influence of capsular bag size with an angulated, 3-piece, open-loop, acrylic intraocular lens (IOL).

SETTING

Department of Ophthalmology, Medical University of Vienna, Vienna, Austria.

METHODS

Twenty-nine eyes of 29 patients with age-related cataract were included in this study. In study 1, an open-loop, 3-piece IOL (AR40e, AMO) was implanted in a standardized fashion in 15 eyes of 15 patients. In study 2, before IOL implantation, a capsular tension ring (CTR) was inserted (14 eyes of 14 patients). Anterior chamber depth (ACD) was assessed with partial coherence interferometry 2 hours; 1, 3, and 5 days; 1 week; and 1 month postoperatively. The capsular bag diameter (CBD) was assessed using gonioscopic measurement of the eyelets of the CTR 1 day, 1 week, and 1 month postoperatively.

RESULTS

In the first postoperative week, there was a significant mean forward movement of -196 microm +/- 117 (SD) (P < .005) in study 1 and -139 +/- 97 microm in study 2 (P < .005). These movements correspond to refractive changes of -0.31 diopter (D) and -0.20 D, respectively. The movement was linear in the first 5 days after surgery. Different patterns of early postoperative movement were seen, illustrating interindividual variability. A significant correlation of 0.67 (P < .05) was found between the change in ACD and CBD.

CONCLUSIONS

A linear forward movement of the IOL during the first postoperative week was followed by a relatively stable IOL position. Loss of haptic memory seemed to be the most likely cause. Myopic eyes with large capsular bags showed less IOL shift in the early postoperative period than hyperopic eyes with smaller capsular bags.

Biometry and intraocular lens power calculation

This article surveys the literature of 1 year, between July 2003 and August 2004, on the topic of biometry and intraocular lens power calculation for cataract surgery. There is an increasing demand for low postoperative refractive error with rising patient expectations, especially with patients who have already undergone refractive surgery, and with developing intraocular lens technologies such as multifocal, accommodating, or toric intraocular lenses. Optical biometry has become an invaluable tool for axial length measurement, especially for a setting with a less experienced biometrist. Introduction of ray tracing for power calculation and new methods of dealing with power calculation in eyes that have undergone previous refractive surgery seem promising. New intraocular lens designs that allow adjusting the axial optic position and therefore the effective refractive power of the intraocular lens have been evaluated in animal studies.

Accommodative intraocular lenses: current status

PURPOSE OF REVIEW

The possibility of using a monofocal IOL with accommodative ability allows refractive cataract surgery with a clearly decreased potential of photic phenomena. Three IOLs of different designs and materials have demonstrated accommodative ability, but the degree of accommodative amplitude has been reported to different extents and variabilities. The plate-haptic CrystaLens has a hinged design that might permit forward movement of the optic as a result of pressure changes in the vitreous cavity. The 1CU has modified haptics that bend in the bag as the lens capsule contracts, which are supposed to cause anterior displacement of the lens optic. With the dual-optic one-piece Synchrony, springlike haptics separate a high-plus anterior lens from a posterior minus lens. With accommodative effort, the capsular bag expands and the springs express kinetic energy, which might allow the optics to separate as the anterior lens moves forward.

RECENT FINDINGS

This article seeks to clarify and distinguish the concepts of true accommodation and pseudo accommodation. Current designs of accommodative IOLs are supposed to work by the focus-shift principle to allow true pseudophakic accommodation. Studies that biometrically assessed optic shift found no or only low amplitudes of forward movement. The amount of forward movement, if present, was highly variable between patients. To date, most studies present psychophysical data for the proof of concept, which alone seems insufficient. Capsule bag performance and posterior capsule opacification with accommodative IOLs seem worse than those with standard intraocular lenses.

SUMMARY

The potential clinical benefits of accommodative IOL technology for both cataract patients and refractive patients may place accommodative IOLs in a competitive position with multifocal IOL technology.

Potentially Accommodating Intraocular Lenses - An In Vitro and In Vivo Study Using Three-dimensional High-frequency Ultrasound

PURPOSE

To investigate the accommodative performance of new intraocular lenses (IOL) using the advantages of three-dimensional ultrasound biomicroscopy.

METHODS

An in vitro simulation device was designed to study IOL performance using an artificial capsular bag and a stretching device. The haptic region of the Akkommodative 1CU (HumanOptics AG) and CrystaLens AT-45 (Eyeonics Inc) was visualized in vitro in three dimensions, using an in-house developed three-dimensional ultrasound biomicroscope. The in vitro results were used to describe the in vivo situation in four patients with accommodative implants.

RESULTS

The haptic position and angulation in consideration of the accommodation state was distinguished and analyzed. In the simulation model, a maximal angulation change of 4.5 degrees and 4.3 degrees and a maximal forward shift of 0.33 mm and 0.28 mm was observed for the AT-45 and 1CU, respectively. In vivo, a change in haptic angulation <100 and a maximal forward shift of 0.50 mm was observed for the 1CU. These changes correspond to a theoretical approximate value of 0.50 diopters.

CONCLUSIONS

The in vitro simulation device examined with three-dimensional ultrasound biomicroscopy provided information on the accommodative performance of these potentially accommodative IOL designs. Using three-dimensional ultrasound biomicroscopy, corresponding changes in haptic angulation during pharmacological-induced accommodation were observed.

Predicting postoperative intraocular lens position and refraction

PURPOSE

To predict the postoperative IOL position and refraction as accurately as possible independent of individualization of the parameters.

SETTING

Universitats-Augenklinik, Mainz, Germany, and Vienna, Austria.

METHODS

One patient cohort (189 eyes, Vienna) was used to calibrate the prediction method, which was then applied to a second cohort (65 eyes, Mainz). All calculations were based on consistent numerical ray tracing of the pseudophakic eye using the original manufacturer's intraocular lens (IOL) data (radii, thickness, refractive index). A new algorithm to predict IOL position was developed. Ultrasound (US) axial lengths were calibrated relative to partial coherence interferometry (PCI). Corneal radii extracted from topography were checked against radii measured with the IOLMaster (Zeiss) and by Littmann keratometry.

RESULTS

Zero mean prediction errors for IOL position and refraction were obtained without adjusting the parameters and with PCI lengths or US lengths calibrated relative to the PCI values. There was no significant loss of accuracy of US data compared to PCI data. Corneal radii extracted from topography were slightly but statistically significantly different from the Littmann values, and they were more accurate than the latter with respect to prediction error. The measured mean central IOL position (distance from posterior corneal surface) for all IOL types was 4.580 mm, a value very close to the mean recalculated from A-constants (4.587 mm). The difference in the individual central IOL position relative to the mean value depended only linearly (ie, no higher orders such as square or cubic are needed) on axial length, with the mean central IOL position as a free parameter. This parameter should be 4.6 +/- 0.2 mm (the same value as independently measured or recalculated) to obtain zero steepness of the prediction error as a function of axial length, producing zero bias for long and short eyes.

CONCLUSIONS

Calculation errors from formulas and confusing adjusting parameters can be avoided if calculations and measurements are performed on a clear and simple physical basis. Nevertheless, an individual prediction error, typically 0.5 to 1.0 diopter, seems to be unavoidable.