Intraocular lens optic edge design for the prevention of posterior capsule opacification after cataract surgery.

BACKGROUND: Posterior capsule opacification (PCO) is a clouding of the posterior part of the lens capsule, a skin-like transparent structure, which surrounds the crystalline lens in the human eye. PCO is the most common postoperative complication following modern cataract surgery with implantation of a posterior chamber intraocular lens (IOL). The main symptoms of PCO are a decrease in visual acuity, 'cloudy', blurred vision and reduced contrast sensitivity. PCO is treated with a neodymium:YAG (Nd:YAG) laser to create a small opening in the opaque capsule and regain a clear central visual axis. This capsulotomy might cause further ocular complications, such as raised intraocular pressure or swelling of the central retina (macular oedema). This procedure is also a significant financial burden for health care systems worldwide. In recent decades, there have been advances in the selection of IOL materials and optimisation of IOL designs to help prevent PCO formation after cataract surgery. These include changes to the side structures holding the lens in the centre of the lens capsule bag, called IOL haptics, and IOL optic edge designs. OBJECTIVES: To compare the effects of different IOL optic edge designs on PCO after cataract surgery. SEARCH METHODS: We searched CENTRAL, Ovid MEDLINE, Ovid Embase, Latin American and Caribbean Health Sciences Literature Database (LILACS), the ISRCTN registry, ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) up to 17 November 2020. SELECTION CRITERIA: We included randomised controlled trials (RCTs) that compared different types of IOL optic edge design. Our prespecified primary outcome was the proportion of eyes with Nd:YAG capsulotomy one year after surgery. Secondary outcomes included PCO score, best-corrected distance visual acuity (BCDVA) and quality of life score at one year. Due to availability of important long-term data, we also presented data at longer-term follow-up which is a post hoc change to our protocol. DATA COLLECTION AND ANALYSIS: We used standard methods expected by Cochrane and the GRADE approach to assess the certainty of the evidence. MAIN RESULTS: We included 10 studies (1065 people, 1834 eyes) that compared sharp- and round-edged IOLs. Eight of these studies were within-person studies whereby one eye received a sharp-edged IOL and the fellow eye a round-edged IOL. The IOL materials were acrylic (2 studies), silicone (4 studies), polymethyl methacrylate (PMMA, 3 studies) and different materials (1 study). The studies were conducted in Austria, Germany, India, Japan, Sweden and the UK. Five studies were at high risk of bias in at least one domain. We judged two studies to be at low risk of bias in all domains. There were few cases of Nd:YAG capsulotomy at one year (primary outcome): 1/371 in sharp-edged and 4/371 in round-edged groups. The effect estimate was in favour of sharp-edged IOLs but the confidence intervals were very wide and compatible with higher or lower chance of Nd:YAG capsulotomy in sharp-edged compared with round-edged lenses (Peto odds ratio (OR) 0.30, 95% CI 0.05 to 1.74; I2 = 0%; 6 studies, 742 eyes). This corresponds to seven fewer cases of Nd:YAG capsulotomy per 1000 sharp-edged IOLs inserted compared with round-edged IOLs (95% CI 9 fewer to 7 more). We judged this as low-certainty evidence, downgrading for imprecision and risk of bias. A similar reduced risk of Nd:YAG capsulotomy in sharp-edge compared with round-edge IOLs was seen at two, three and five years but as the number of Nd:YAG capsulotomy events increased with longer follow-up this effect was more precisely measured at longer follow-up: two years, risk ratio (RR) 0.35 (0.16 to 0.80); 703 eyes (6 studies); 89 fewer cases per 1000; three years, RR 0.21 (0.11 to 0.41); 538 eyes (6 studies); 170 fewer cases per 1000; five years, RR 0.21 (0.10 to 0.45); 306 eyes (4 studies); 331 fewer cases per 1000. Data at 9 years and 12 years were only available from one study. All studies reported a PCO score. Four studies reported the AQUA (Automated Quantification of After-Cataract) score, four studies reported the EPCO (Evaluation of PCO) score and two studies reported another method of quantifying PCO. It was not possible to pool these data due to the way they were reported, but all studies consistently reported a statistically significant lower average PCO score (of the order of 0.5 to 3 units) with sharp-edged IOLs compared with round-edged IOLs. We judged this to be moderate-certainty evidence downgrading for risk of bias. The logMAR visual acuity score was lower (better) in eyes that received a sharp-edged IOL but the difference was small and likely to be clinically unimportant at one year (mean difference (MD) -0.06 logMAR, 95% CI -0.12 to 0; 2 studies, 153 eyes; low-certainty evidence). Similar effects were seen at longer follow-up periods but non-statistically significant data were less fully reported: two years MD -0.01 logMAR (-0.05 to 0.02); 2 studies, 311 eyes; three years MD -0.09 logMAR (-0.22 to 0.03); 2 studies, 117 eyes; data at five years only available from one study. None of the studies reported quality of life. Very low-certainty evidence on adverse events did not suggest any important differences between the groups. AUTHORS' CONCLUSIONS: This review provides evidence that sharp-edged IOLs are likely to be associated with less PCO formation than round-edged IOLs, with less Nd:YAG capsulotomy. The effects on visual acuity were less certain. The impact of these lenses on quality of life has not been assessed and there are only very low-certainty comparative data on adverse events.

Capsular bag performance of a novel hydrophobic acrylic single-piece intraocular lens: Two-year results of a randomised controlled trial.

PURPOSE: To determine the visual outcome, intraocular lens (IOL) stability and posterior capsule opacification (PCO) rate of a hydrophobic acrylic intraocular lens. SETTING: Vienna Institute for Research in Ocular Surgery, Hanusch Hospital, Vienna, Austria. DESIGN: This double-masked randomised study included patients who underwent standard cataract surgery. METHOD: Patients received either the hydrophobic acrylic IOL (iPure, PhysIOL) or the hydrophobic acrylic control IOL (Tecnis ZCB00, Johnson&Johnson). Subjective refraction, uncorrected and corrected distance visual acuity (UDVA, CDVA), IOL tilt and decentration (Purkinje meter) and PCO intensity using retroillumination images with automated image analysis (automated quantification of after-cataract, AQUA), were evaluated for both groups 2 years after surgery. RESULTS: A total number of 31 patients completed the 2-year follow-up, 16 in the study group and 15 in the control group. The CDVA was 0.0 logMAR (standard deviation - SD: 0.1) for the study IOL and 0.1 logMAR (SD: 0.2) for the control IOL, p = 0.001. The AQUA PCO score for the study group was 2.1 and 1.4 for the control group, p = 0.44. Mean IOL tilt was 2.9° (SD: 1.8) in the study group and 5.0° (SD: 4.5) in the control group, whilst the mean decentration was 0.37 mm (SD: 0.18) and 0.45 mm (SD: 0.3), p = 0.610. CONCLUSION: The studied parameters revealed a good performance for both IOLs. Both IOLs had good CDVA, a small amount of tilt and decentration and none of the patients required laser capsulotomies during the follow-up time of 2 years after surgery.Presented at the 37th ESCRS Congress Paris, France, September 2019.

Variability in angle κ and its influence on higher-order aberrations in pseudophakic eyes.

PURPOSE: To observe the variability in angle κ in pseudophakic patients and assess its correlation with optical biometry measurements and higher-order aberrations (HOAs). SETTING: Hanusch Hospital, Vienna, Austria. DESIGN: Prospective case series. METHODS: This study included patients who had cataract surgery 3 months to 1 year before study recruitment. In all cases, Purkinje meter images were taken. In addition, partial coherence interferometry measurement (IOLMaster) of the axial intraocular lens (IOL) position was performed. In a subgroup of patients, an additional Hartmann-Shack sensor measurement was taken to assess HOAs (WASCA). RESULTS: This study comprised 395 eyes of 349 patients. The mean age of the 210 women and 139 men was 74.1 years ± 8.6 (SD) (range 44 to 91 years). The mean tilt (pupillary axis) and decentration were 3.9 ± 2.3 degrees (range 0.2 to 16.2 degrees) and 0.4 ± 0.2 mm (range 0.0 to 1.7 mm), respectively. The mean angle κ was 5.2 ± 2.6 degrees (range 0.3 to 13.9 degrees), and the mean orientation of this modulus was 189.5 ± 53.2 degrees (range 25.3 to 339.7 degrees). CONCLUSION: The variability in the angle κ was high.

Comparison of intraocular lens decentration and tilt measurements using 2 Purkinje meter systems.

PURPOSE: To evaluate the difference in intraocular lens tilt and decentration measurements with 2 Purkinje meters. SETTING: Vienna Institute for Research in Ocular Surgery, Hanusch Hospital, Vienna, Austria. DESIGN: Prospective evaluation of diagnostic test. METHODS: This single-center study included pseudophakic patients in 2 substudies in which 3 consecutive measurements were performed with 2 Purkinje meters (Spanish and German). In substudy 1, an inexperienced examiner performed all measurements after a short learning period. In substudy 2, all measurements were taken by experienced examiners under direct supervision of the inventors of the devices. RESULTS: Substudy 1 included 53 pseudophakic eyes in which all 53 scans were successful with the Spanish device; however, only 35 measurements (66%) were successful with the German Purkinje meter. The mean tilt measured with the Spanish Purkinje meter was 4.35 degrees ± 2.50 (SD) and 9.20 ± 6.96 degrees with the German Purkinje meter. The mean decentration was 0.44 ± 0.19 mm and 0.74 ± 0.91 mm, (P = .44), respectively. In substudy 2 (29 pseudophakic eyes), the number of successful scans was 29 (100%) and 18 (62%) for the Spanish meter and German Purkinje meter, respectively. The mean horizontal and vertical tilt difference vector between the 2 systems was 4.89 ± 3.24 degrees and 7.57 ± 3.82 degrees, respectively. CONCLUSIONS: Concerning clinical feasibility, the Spanish Purkinje meter had a greater percentage of successful scans than the German device. In addition, this device measured significantly higher tilt values than the Spanish Purkinje meter.

Macular disease detection with a swept-source optical coherence tomography-based biometry device in patients scheduled for cataract surgery.

PURPOSE: To assess the sensitivity and specificity for detecting macular disease with a new optical biometry device with swept-source optical coherence tomography (SS-OCT) used before cataract surgery. SETTING: Hanusch Hospital, Vienna, Austria. DESIGN: Consecutive case series. METHODS: This study included patients with or without macular disease. All patients were scanned using the new biometry device (IOLMaster 700), which allows a 1.0 mm central retinal scan using SS-OCT technology. Also, all eyes were assessed using a dedicated retinal OCT device (RTVue) on the same day. Two experienced examiners and 1 ophthalmology resident graded all scans individually. Sensitivity and specificity for detecting macular disease were assessed, as were the receiver operating characteristic curves. RESULTS: Of the 125 eyes included, 5 were excluded from the analysis, 65 had a macular disease, and 55 were healthy. The sensitivity of the biometry device was moderate (between 42% and 68%), and the specificity was high (89% to 98%). Intraobserver reproducibility for assessing the biometry device was 88.3%. CONCLUSIONS: The biometry device with SS-OCT provided useful information concerning the macula, especially for intraretinal fluid and macular holes. However, it cannot replace a macular OCT device. FINANCIAL DISCLOSURE: None of the authors has a financial or proprietary interest in any material or method mentioned.

Influence of the overall intraocular lens diameter on rotational stability.

PURPOSE: To evaluate the rotational stability of two intraocular lenses (IOLs) of similar design and material but with a difference of 1 mm in overall length. METHODS: In this prospective study patients with age-related cataract were included. An IOL with an overall diameter of 12 mm (ACR6 = small-diameter IOL) was compared to an IOL with an overall diameter of 13 mm (IDEA 613 XC = large-diameter IOL). RESULTS: In total, 60 patients were included in this study. Absolute rotation in the small- and large-diameter groups was 4.4° (SD: 4.0; range: 0.3-17.8) and 3.0° (SD: 2.4; range: 0.1-7.8), respectively. The differences between the two IOLs were not found to be statistically significant. CONCLUSION: The effect of the overall length of an IOL appears to have little impact on early rotation after cataract surgery.

Using continuous intraoperative optical coherence tomography measurements of the aphakic eye for intraocular lens power calculation.

BACKGROUND/AIMS: To include intraoperative measurements of the anterior lens capsule of the aphakic eye into the intraocular lens power calculation (IPC) process and to compare the refractive outcome with conventional IPC formulae. METHODS: In this prospective study, a prototype operating microscope with an integrated continuous optical coherence tomography (OCT) device (Visante attached to OPMI VISU 200, Carl Zeiss Meditec AG, Germany) was used to measure the anterior lens capsule position after implanting a capsular tension ring (CTR). Optical biometry (intraocular lens (IOL) Master 500) and ACMaster measurements (Carl Zeiss Meditec AG, Germany) were performed before surgery. Autorefraction and subjective refraction were performed 3 months after surgery. Conventional IPC formulae were compared with a new intraoperatively measured anterior chamber depth (ACD) (ACDIntraOP) partial least squares regression (PLSR) model for prediction of the postoperative refractive outcome. RESULTS: In total, 70 eyes of 70 patients were included. Mean axial eye length (AL) was 23.3 mm (range: 20.6-29.5 mm). Predictive power of the intraoperative measurements was found to be slightly better compared to conventional IOL power calculations. Refractive error dependency on AL for Holladay I, HofferQ, SRK/T, Haigis and ACDintraOP PLSR was r(2)=-0.42 (p<0.0001), r(2)=-0.5 (p<0.0001), r(2)=-0.34 (p=0.010), r(2)=-0.28 (p=0.049) and r(2)<0.001 (p=0.866), respectively, CONCLUSIONS: ACDIntraOP measurements help to better predict the refractive outcome and could be useful, if implemented in fourth-generation IPC formulae.

Rotational performance and corneal astigmatism correction during cataract surgery: aspheric toric intraocular lens versus aspheric nontoric intraocular lens with opposite clear corneal incision.

PURPOSE: To compare the astigmatism-reducing effect of an aspheric toric intraocular lens (IOL) and an aspheric nontoric IOL with an opposite clear corneal incision (OCCI) in cataract surgery. SETTING: Vienna Institute for Research in Ocular Surgery, Hanusch Hospital, Vienna, Austria. DESIGN: Prospective randomized clinical study. METHODS: Patients with low to moderate corneal astigmatism scheduled for cataract surgery received an aspheric toric IOL (Lentis L-312T) or an aspheric nontoric IOL (Lentis L-312) combined with an OCCI. Keratometry and corneal tomography were performed 1 hour, 1 week, 3 months and 9 months postoperatively. Postoperative residual astigmatism was measured using an autorefractor. Rotational toric IOL stability was analyzed using retroillumination photography. RESULTS: Fifty-five patients were included. Three months postoperatively, the mean reduction in corneal astigmatism was 0.67 diopter (D) ± 0.58 (SD) in the toric group and 0.18 ± 0.52 D in the nontoric-OCCI group. The mean uncorrected distance visual acuity was 0.29 ± 0.30 logMAR and 0.09 ± 0.18 logMAR, respectively (P=.02). The mean refractive astigmatism was 1.02 ± 0.54 D and 0.68 ± 0.52 D, respectively (P=.05). One hour, 3 months, and 9 months postoperatively, the mean absolute IOL misalignment of toric IOLs was 4.99 ± 4.66 degrees, 13.59 ± 11.29 degrees, and 19.90 ± 14.48 degrees, respectively. CONCLUSIONS: The toric IOL tended to rotate significantly postoperatively. Visual acuity was good in both groups. Residual refractive cylinder was significantly lower in the toric IOL group. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Evaluation of factors influencing the remaining astigmatism after toric intraocular lens implantation.

PURPOSE: To evaluate the influencing factors on remaining astigmatism after implanting a toric intraocular lens during cataract surgery. METHODS: In this observational study, consecutive patients with cataract from three different centers who received toric intraocular lenses were included. Keratometry was performed with an optical biometry device preoperatively. The IOLMaster 500 (Carl Zeiss Meditec AG, Jena, Germany) was used in Vienna, Lenstar (Haag-Streit, Köniz, Switzerland) in Castrop-Rauxel, and IOLMaster (Carl Zeiss Meditec AG) in London. Partial least squares regression was used to detect the influence of different parameters on remaining astigmatism. RESULTS: In total, 235 eyes of 200 patients were included. Mean corneal astigmatism measured preoperatively with the optical biometry device was -2.24 ± 0.87 diopters (D) (range: -5.75 to -1.00 D). Mean absolute and vector difference between the aimed for and the postoperatively measured astigmatism were 0.48 ± 0.37 D (range: 0.00 to 2.05 D) and 0.73 ± 0.46 D (range: 0.031 to -2.20 D), respectively (P = .576). Partial least squares regression showed a significant effect of preoperatively measured corneal astigmatism and deviation between preoperative measurements of the cornea on the postoperative (unintended) remaining astigmatism. CONCLUSIONS: The main source of error when using toric intraocular lenses is the preoperative measurement of corneal astigmatism, especially in eyes with low astigmatism. The influence of the postoperative anterior chamber depth on the cylindrical power of toric intraocular lenses and the effect of misalignment on the reduction of the astigmatism-reducing effect can be easily calculated.

Rotational stability of a single-piece toric acrylic intraocular lens: a pilot study.

PURPOSE: To evaluate the visual performance and rotational stability of the Tecnis Toric 1-piece intraocular lens (IOL) during the first 3 postoperative months. DESIGN: Prospective, single-center study. METHODS: In this study, patients with age-related cataract and corneal astigmatism of 1.0 to 3.0 diopters measured with the IOLMaster 500 (Carl Zeiss Meditec AG) were included. Before surgery, rotating Scheimpflug scans (Pentacam HR; Oculus) were performed and the cornea was marked in the sitting position at the slit lamp. Patients received a single-piece toric hydrophobic acrylic IOL (Tecnis Toric; AMO). Immediately and 3 months after surgery, retroillumination photographs were obtained to assess the rotational stability of the IOL. Additionally, Autorefraction (Topcon), subjective refraction, uncorrected and distance-corrected visual acuity, keratometry, and Scheimpflug and ocular wavefront (WASCA, Carl Zeiss Meditec AG) measurements were performed at the 3-month follow-up. RESULTS: Thirty eyes of 30 patients were included in this study. Mean absolute difference between the IOL axis at the 3-month and 1-hour follow-up was 2.7 degrees (standard deviation, 3.0 degrees). The IOL rotation was less than 3 degrees and less than 6 degrees in 62% and 95% of all cases, respectively. CONCLUSIONS: The Tecnis Toric 1-piece IOL is rotationally stable and shows excellent capsule bag performance and refractive outcomes.

Misalignment of a novel single-piece acrylic intraocular lens in the first three months after surgery.

PURPOSE: To evaluate the misalignment of a new single-piece microincisional hydrophobic acrylic intraocular lens (IOL) in emmetropic, myopic and hyperopic eyes within the first 3 months after surgery. SETTING: Vienna Institute for Research in Ocular Surgery, Karl Landsteiner Institute, Hanusch Hospital, Department of Ophthalmology, Vienna, Austria. METHODS: Patients with age-related cataract were included in this prospective study. Each patient received a single-piece microincisional hydrophobic acrylic IOL (AF-1 NY-60, Hoya) in the study eye. Subgroups of emmetropic, myopic and hyperopic eyes were defined according to IOL power calculation. Anterior chamber depth (ACD) measurements were performed with an AC-Master. Tilt and decentration of the IOL were measured with a Purkinje meter. Follow-up assessments were performed 1 h, 3 weeks and 3 months after surgery. RESULTS: Forty-two eyes of 42 patients (21 emmetropic, 10 myopic and 11 hyperopic eyes) were included. The mean ACD 1 h, 3 weeks and 3 months after surgery was 4.597 ± 0.533, 4.483 ± 0.347 and 4.438 ± 0.398 mm, respectively. Differences in ACD between follow-ups and between subgroups were not statistically significant (both p > 0.05). On average, 3 months after surgery IOLs were tilted 0.81 ± 2.86° nasally and 0.70 ± 3.13° inferiorly and decentered 0.06 ± 0.24 mm nasally and 0.15 ± 0.29 mm superiorly. Differences in tilt and decentration were not statistically significant (both p > 0.05). We observed 1 case of severe capsular fibrosis. CONCLUSIONS: The single-piece microincisional hydrophobic acrylic IOL showed good axial stability and only little, clinically not relevant tilt and decentration in the first 3 months after surgery.

Effect of heparin coating of a foldable intraocular lens on inflammation and capsular bag performance after cataract surgery.

PURPOSE: To evaluate the effect of a heparin-coated foldable intraocular lens (IOL) on postoperative flare in high-risk patients. SETTING: Vienna Institute for Research in Ocular Surgery, Department of Ophthalmology, Hanusch Hospital, Vienna, Austria. DESIGN: Randomized clinical trial. METHODS: This study included patients with diabetes mellitus (DM), pseudoexfoliation syndrome (PXF), or both scheduled for cataract surgery in both eyes. One eye received a coated IOL (Polylens EC-1YH PAL) and the other eye, an uncoated control IOL (Polylens EC-1Y PAL). Aqueous flare measurements were taken using a laser flare meter (FM-600, Kowa) preoperatively and 1 hour, 1 day, 3 weeks, and 3 months postoperatively. Visual acuity and anterior (ACO) and posterior (PCO) capsule opacification were assessed, and IOL centration and tilt were measured with a Purkinje meter. RESULTS: Eighty eyes of 40 patients were included in the study; 64 eyes of 32 patients completed the study. The mean flare values (photons/ms) preoperatively and 1 hour, 1 day, 3 weeks, and 3 months postoperatively were 6.98 ± 3.71 (SD), 19.14 ± 18.90, 16.62 ± 25.33, 10.33 ± 9.70, 8.74 ± 4.64, respectively, with the coated IOL and 8.65 ± 5.73, 22.08 ± 16.23, 13.44 ± 13.71, 7.50 ± 4.11, and 7.03 ± 3.70, respectively, with the control IOL. No significant differences were found in flare, visual acuity, ACO, PCO, tilt, or centration between the coated IOL and the control IOL at any timepoint. CONCLUSION: No significant differences in flare or capsule performance were found between the coated IOL and control IOL.

Predicting the postoperative intraocular lens position using continuous intraoperative optical coherence tomography measurements.

PURPOSE: The aim of this study was to assess, if measuring the position of the lens capsule intraoperatively with a continuous intraoperative optical coherence tomography (OCT) device could be useful to improve the prediction of the intraocular lens (IOL) position. METHODS: This prospective study included patients who were scheduled for cataract surgery. A prototype operating microscope with an integrated continuous OCT device was used to measure the anterior and posterior lens capsule position at different time points during cataract surgery. In all cases, a capsular tension ring (CTR) was used to tauten the lens capsule. Partial coherence interferometry was used to measure anterior chamber depth (ACD) immediately before, and 1 hour and 3 months postoperatively. Partial least squares regression (PLSR) was used to assess the influence of different pre- and intraoperatively measured parameters. RESULTS: In total, 70 eyes of 70 patients were included. Mean axial eye length was 23.6 mm (range, 20.6 mm-30.8 mm), mean used IOL power was 22.2 diopters (D; range, 6.0 D-31.5 D). PLSR showed that the anterior lens capsule measured after removing the crystalline lens and after implanting a CTR was a significantly better predictor for the postoperative ACD compared with preoperative ACD measurements. CONCLUSIONS: The main problem of IOL power calculation, the prediction of the IOL position after surgery, could possibly be reduced by using intraoperative lens capsule measurements instead of preoperative ACD measurements. (ClinicalTrials.gov number, NCT01867541.).

Evaluation of 4 corneal astigmatic marking methods.

PURPOSE: To compare 4 devices used to mark the cornea before astigmatism-reducing surgery. SETTING: Hanusch Krankenhaus, Vienna, Austria. DESIGN: Randomized examiner-masked clinical trial. METHODS: Patients were randomly allocated to 1 of 4 groups for preoperative corneal marking in the sitting position. The 4 methods used were marking at the slitlamp with an insulin needle, a pendular marker, a bubble marker, and a tonometer marker. The marks were then documented with a standardized photographic technique, and the rotational deviation and vertical misalignment were assessed. RESULTS: The study enrolled 60 patients. The pendular-marking device showed the least rotational deviation to the reference meridian (mean 1.8 degrees). There was no statistically significant difference between slitlamp marking and pendular marking (P = .05); however, there was a significant difference between the pendular marker and the bubble marker and between the pendular marker and the tonometer marker (P = .01 and P < .01, respectively). The least vertical misalignment was observed with the slitlamp-marking device (mean 0.28 mm). There was no statistically significant difference in vertical misalignment between the 4 groups. CONCLUSIONS: All marking devices showed a slight deviation to the horizontal reference meridian. Because small deviations of the meridian can result in a relevant reduction in the astigmatism-reducing effect with toric intraocular lenses, accurate marking of the cornea before surgery is critical due to the variable cyclotorsion caused by a change from the upright to the supine position. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.