Optic Edge Research Articles

Correlation between the radial peripapillary capillaries and the retinal nerve fibre layer in the normal human retina

This study aims to provide evidence of the importance of radial peripapillary capillaries (RPCs) by quantitative study of the relationship between the RPCs and retinal nerve fibre layer (RNFL) in normal human donor eyes. The retinal microvasculature in eleven normal human donor eyes was perfused, fixed and labelled after cannulation of the central retinal artery. The retinas were dissected and whole-mounted for confocal microscopy. Six study regions were taken radially from the edge of the optic disc. RPCs from the optic disc edge to a radial distance up to 2.5 mm were imaged and their diameters, inter-capillary distance and volume occupation measured. These were correlated with the study region as well as thickness of the RNFL. It was found that the pooled average diameter of the RPCs in the first 2.5 mm from the optic disk was 8.9 μm. Significant differences in capillary diameter were present in the six regions, with larger diameter RPCs in the superior, inferior and nasal regions, and significantly smaller diameter in the temporal region. RPCs in the arcuate fibre regions extend the furthest from the optic disc, maintained a close inter-capillary distance for a longer distance than other regions, and have the highest RPCs volume occupancy. The RPCs volume was generally correlated with RNFL thickness. In conclusion, a close correlation between RNFL and RPCs presence has been demonstrated which is supportive of their functional reliance/co-dependence. The significantly smaller temporal RPCs may be a result of the greater presence of RPCs in the two bordering arcuate fibre regions and therefore a richer availability of nutrients diffusing from these two regions.

Pseudophakic photopsia – Optical simulations with a model eye to evaluate IOL design and material

AbstractPurpose Photopic phenomena (photopsia) gain in relevance and may become key problems after modern cataract surgery. The purpose of this study is to evaluate potential influencing factors for these optical phenomena using ray tracing techniques in a model eye.Methods A schematic model eye was used for simulations with professional optic design software (ASAP). The crystalline lens was replaced by an intraocular lens implant. We varied the lens’ edge design (edge radius from 0.00 mm (0.05 mm) 0.15 mm), refractive index (1.55 and 1.46), axial and lateral position (each ±0.5 mm), as well as the pupil diameter (2.5, 3.5 and 4.5 mm). Retinal illuminance was simulated for a Ganzfeld perimeter sphere (d=300 mm, 250° field of view) with 107 rays emitting in a Lambertian distribution.Results Positive photopsia could be observed at the central and paracentral nasal visual field originating from total internal reflection at the lens’ optics edge, which becomes more intense with higher refractive index and smaller edge radius or larger peripheral thickness of the lens. Negative photopsia was seen at the far temporal visual field as a gap in illuminance originating by a gap between overlaying light pathways of primary image and direct path. Photopsia is less pronounced with larger pupil size and axial or lateral displacement of the lens.Conclusion Photopsia is not a new phenomenon in pseudophakic eyes, but with lenses with a high refractive index (smaller incision) and sharp optic edges (for prevention of secondary cataract) the intensity of artificial light phenomena and gaps photopsia might become the main reason for patient dissatisfaction after cataract surgery.

Scanning electron microscopic characteristics of commercially available 1- and 3-piece intraocular lenses

To evaluate commercially available 1- and 3-piece intraocular lenses (IOLs) with scanning electron microscopy (SEM). Department of Ophthalmology and Electron Microscopy Center, University Hospital Jena, Jena, Germany. Experimental study. Seven +23.0 diopter IOLs of different design and material and from different manufacturers were chosen for a detailed assessment. Scanning electron microscopy was used at standardized magnifications to assess typical IOL characteristics. The particular focus was the optic edge, the optic surface, the haptic–optic junction, and the haptic. All square-edged IOLs had a curvature radius of less than 10 μm, while the mean optic edge thickness ranged between 216 μm and 382 μm. A 360-degree square-edged boundary was present in all 3-piece IOLs and in a single 1-piece model. Relevant production remnants on the optic edge were observed in 1 case. Regarding the haptic, 3-piece IOLs had uniformly shaped fibers with a mean thickness of 177 μm ± 51 (SD) (range 116 to 220 μm). Chemical adhesives were used to attach the haptic in 1 case, where alterations of the IOL material were observed. In another case, the haptic fiber was press-fitted into the optic, which resulted in bulging of the optic profile. Inspection of surface characteristics showed wavelike patterns in 2 IOLs. Taking clinical relevance into account, all IOLs were of high manufacturing quality. Certain attention was paid in creating a sharp optic edge. Surface irregularities of 2 IOLs were attributed to the manufacturing technique. Methods for implementing the haptic–optic junction were diverse.

Variability between experts in defining the edge and area of the optic nerve head

ObjectiveEstimation of the error rate in the subjective determination of the optic nerve head edge and area. Method(1) 169 images of optic nerve disk were evaluated by five experts for the defining of the edges in 8 positions (every 45°). (2) The estimated areas of 26 cases were compared with the measurements of the Cirrus Optical Coherence Tomography (OCT-Cirrus). Results(1) The mean variation of the estimated radius was ±5.2%, with no significant differences between sectors. Specific differences were found between the 5 experts (p<0.001), each one compared with the others. (2) The disk area measured by the OCT-Cirros was 1.78mm2 (SD=0.27). The results corresponding to the experts who detected smaller areas were better correlated to the area detected by the OCT-Cirrus (r=0.77–0.88) than the results corresponding to larger areas (r=0.61–0.69) (p<0.05 in extreme cases). ConclusionsThere are specific patterns in each expert for defining the disk edges and involve 20% variation in the estimation of the optic nerve area. The experts who detected smaller areass have a higher agreement with the objective method used. A web tool is proposed for self-assessment and training in this task.

Pathologic Comparison of Asymmetric or Sulcus Fixation of 3-Piece Intraocular Lenses with Square Versus Round Anterior Optic Edges

To evaluate the pathologic findings of 3-piece intraocular lenses (IOLs) with asymmetric or sulcus fixation in pseudophakic cadaver eyes, comparing IOLs with square or round edges on the anterior optic surface. Comparative case series with pathology. A total of 661 pseudophakic cadaver eyes, obtained from eye banks within the United States, implanted with different IOLs. Anterior segment scanning of whole eyes with a high-frequency ultrasound system or high-resolution anterior segment magnetic resonance imaging followed by gross examination. Selected eyes were processed for complete histopathologic analysis. Findings from imaging, gross, and histopathologic evaluation that could be related to out-of-the-bag fixation of the lenses. Of 661 pseudophakic cadaver eyes obtained, 13 had 3-piece hydrophobic acrylic IOLs with anterior and posterior square optic edges, and 14 had 3-piece lenses with anterior round edges (13 silicone lenses and 1 hydrophobic acrylic lens) without symmetric in-the-bag fixation. These 27 selected eyes were processed for complete histopathologic analysis. Gross findings in both groups were composed of IOL decentration and tilt, pigmentary dispersion within the anterior segment and on the IOL surface, and iris transillumination defects. Histopathology of the 14 eyes with 3-piece IOLs with round anterior optic edges showed mild focal disruption of the iris pigmented layer and loop protrusion/erosion in the ciliary sulcus. Additional changes observed in the 13 eyes with square anterior optic edge IOLs included iris changes, such as vacuolization, disruption and loss of the pigmented epithelial layers, iris thinning and atrophy, synechiae, and pigmentary dispersion within the trabecular meshwork. One eye also exhibited initial signs of optic nerve disc cupping. In this series, pathologic findings were more severe in eyes implanted with 3-piece IOLs with square anterior optic edges, suggesting that IOLs with round anterior edges are more suitable for sulcus fixation. Proprietary or commercial disclosure may be found after the references.

Posterior capsule opacification after lens implantation: incidence, risk factors and management

Postoperative capsular opacification is a multifactorial physiological consequence of cataract surgery. Opacification involving the central posterior capsule has a significant impact on high- and low-contrast acuity and low-contrast sensitivity. The proliferation, migration and abnormal differentiation of residual lens epithelial cells and fibers in the capsular bag have been implicated in the pathogenesis of posterior capsule opacification (PCO). The incidence and severity of PCO correlates to the use of surgical techniques, intraocular lens optic edge designs and intraocular lens materials. This article summarizes the clinical studies with recommendations for retarding the development of central PCO. These studies will remain critical for future endeavors undertaken for the eradication of PCO.

Intraocular Lens Delivery Characteristics of the Preloaded AcrySof IQ SN60WS/AcrySert Injectable Lens System

To evaluate the delivery characteristics of the AcrySof IQ SN60WS intraocular lens (IOL) injected via a preloaded AcrySert delivery system. Prospective observational case series. setting: This study was carried out in the cataract service of an ophthalmic hospital that serves a large sector of inner-city London. patient population: The study included all patients undergoing routine phacoemulsification procedures with implantation of the SN60WS IOL via the preloaded system over 5 consecutive months. A total of 85 patients (85 eyes) were included in this study. intervention: Phacoemulsification procedures conducted by 7 surgeons were digitally captured. outcome measures: Video recordings of the IOL delivery stage were analyzed by a single observer. Of particular interests were the orientation of the leading haptic and optic on insertion, the degree of intrawound manipulation of the injector, and the time required to satisfactorily deliver the IOL into the capsular bag in a correct orientation. Problems of IOL delivery were also noted. In 38 out of 85 eyes (45%), correct IOL delivery behavior was achieved with the leading haptic orientating to the left of the surgeon and thus did not require any intrawound rotational manipulation of the injector. Forty-seven of the 85 eyes (55%) required additional rotational manipulation of IOL orientation. Other problems recorded were trapped trailing haptic, haptic-optic adhesion, overriding of the plunger over the optic, and trauma to optic edge. The average time to achieve satisfactory IOL position was 47 seconds. IOL power and the grade of the operating surgeon did not appear to influence the event of a misdirected leading haptic. The AcrySof SN60WS/AcrySert system does not appear to meet the expectations of pro-viding a predictable means of IOL delivery.

Variabilidad entre expertos al delimitar el borde y área papilar

ObjectiveEstimation of the error rate in the subjective determination of the optic nerve head edge and area. Method1) 169 images of optic nerve disc were evaluated by five experts for the defining of the edges in 8 positions (every 45°). 2) The estimated areas of 26 cases were compared with the measurements of the Cirrus Optical Coherence Tomography (OCT-Cirrus). Results1) The mean variation of the estimated radius was ±5.2%, with no significant differences between sectors. Specific differences were found between the 5 experts (P <.001), each one compared with the others. 2) The disc area measured by the OCT-Cirros was 1.78 mm2 (SD =0.27). The results corresponding to the experts who detected smaller areas were better correlated to the area detected by the OCT-Cirrus (r=0.77-0.88) than the results corresponding to larger areas (r =0.61-0.69) (P <.05 in extreme cases). ConclusionsThere are specific patterns in each expert for defining the disc edges and involve 20% variation in the estimation of the optic nerve area. The experts who detected smaller areass have a higher agreement with the objective method used. A web tool is proposed for self-assessment and training in this task.

Pathologic Assessment of Complications with Asymmetric or Sulcus Fixation of Square-Edged Hydrophobic Acrylic Intraocular Lenses

One-piece hydrophobic acrylic intraocular lenses (IOLs) are not indicated for sulcus fixation because of complications, such as uveitis-glaucoma-hyphema syndrome. Similar complications may also be observed with 3-piece lenses that have a square optic edge on the anterior surface. The objective of this study was to provide pathologic evidence of complications related to out-of-the-bag fixation of 1- or 3-piece hydrophobic acrylic IOLs with anterior and posterior square optic edges. Comparative case series with pathology. A total of 661 pseudophakic cadaver eyes obtained from eye banks within the United States, implanted with different IOLs. Anterior segment scanning of whole eyes with a high-frequency ultrasound system or high-resolution anterior segment magnetic resonance imaging, followed by gross examination. Selected eyes were processed for complete histopathologic analysis; some of them were explanted before histopathology to allow for direct light microscopic evaluation of the lenses. Findings from imaging, gross, and histopathologic evaluation that could be related to out-of-the-bag fixation of the lenses. A total of 256 eyes were implanted with hydrophobic acrylic IOLs with anterior and posterior square optic edges; 18 of them exhibiting asymmetric or sulcus IOL fixation (six 1-piece and twelve 3-piece IOLs) underwent complete histopathologic evaluation and were compared with the contralateral eyes with symmetric in-the-bag IOL implantation. Pathologic findings were composed of IOL decentration and tilt, pigmentary dispersion within the anterior segment and on the IOL surface, iris transillumination defects, iris changes including vacuolization/disruption/loss of the pigmented layer, iris thinning, and iris atrophy, as well as synechiae and loop erosion in the case of 3-piece lenses. Findings were more significant in comparison with the control contralateral eyes and were particularly evident in relation to the sulcus-fixated haptic in the case of 1-piece lenses. The majority of the eyes with 3-piece lenses showed signs of complicated surgery. This study provides pathologic correlation of complications that were clinically reported in the peer-reviewed literature in relation to sulcus fixation of 1-piece hydrophobic acrylic IOLs. The eyes with 3-piece lenses generally exhibited evidence of complicated surgery; therefore, all pathologic findings in those cases may not be strictly attributed to the out-of-the-bag fixation.

EARLY HISTOLOGIC AND FUNCTIONAL STUDY OF RADIAL OPTIC NEUROTOMY OUTCOMES IN NORMAL RAT EYES

Radial optic neurotomy (RON) has been proposed as a treatment for central retinal vein occlusion. However, it is still under debate whether RON would be an adequate treatment or a dangerous procedure, and persuasive animal studies are lacking. The aim of this study was to analyze the early histologic and functional outcomes of RON in normal rat eyes. Radial optic neurotomy was performed by cutting into the optic nerve edge at the nasal hemisphere, while the contralateral eye underwent a sham procedure. The retinal function was assessed by scotopic electroretinography, and the visual pathway was assessed by flash visual evoked potentials. Intraocular pressure was assessed with a tonometer, the pupillary light reflex was measured after exposing eyes to a 30-second light flash, whereas the optic nerve head structure was examined by histologic analysis. In normal rat eyes, RON provoked minor histologic alterations at the optic nerve head level and a transient decrease in the electroretinography. No changes in visual evoked potentials, intraocular pressure, and pupillary light reflex were observed in rat eyes submitted to RON. To our knowledge, this is the first study describing the early histopathologic and functional consequences of RON in normal rat eyes.

Quantification of Peripapillary Sparing and Macular Involvement in Stargardt Disease (STGD1)

To quantify and compare structure and function across the macula and peripapillary area in Stargardt disease (STGD1). Twenty-seven patients (27 eyes) and 12 age-similar controls (12 eyes) were studied. Patients were classified on the basis of full-field electroretinogram (ERG) results: Fundus autofluorescence (FAF) and spectral domain-optical coherence tomography (SD-OCT) horizontal line scans were obtained through the fovea and peripapillary area. The thicknesses of the outer nuclear layer plus outer plexiform layer (ONL+), outer segment (OS), and retinal pigment epithelium (RPE) were measured through the fovea, and peripapillary areas from 1° to 4° temporal to the optic disc edge using a computer-aided, manual segmentation technique. Visual sensitivities in the central 10° were assessed using microperimetry and related to retinal layer thicknesses. Compared to the central macula, the differences between controls and patients in ONL+, OS, and RPE layer thicknesses were less in the nasal and temporal macula. Relative sparing of the ONL+ and/or OS layers was detected in the nasal (i.e., peripapillary) macula in 8 of 13 patients with extramacular disease on FAF; relative functional sparing was also detected in this subgroup. All 14 patients with disease confined to the central macula, as detected on FAF, showed ONL+ and OS layer thinning in regions of normal RPE thickness. Relative peripapillary sparing was detected in STGD1 patients with extramacular disease on FAF. Photoreceptor thinning may precede RPE degeneration in STGD1.

Pathology of 157 human cadaver eyes with round-edged or modern square-edged silicone intraocular lenses: Analyses of capsule bag opacification

To assess the degree of capsular bag opacification in human cadaver eyes with silicone intraocular lenses (IOLs), specifically comparing the differences between round-edged IOLs and modern square-edged IOLs. John A. Moran Eye Center, University of Utah, USA. Experimental study. The eyes were immersed in 10% formalin on enucleation. They had anterior segment scanning with a very-high-frequency ultrasound (Artemis). After the eyes were sectioned at the equator, gross examination of the anterior segment was performed from the posterior aspect to assess the degree of capsular bag opacification, coverage of the IOL edge by the anterior capsule, and IOL fixation. Selected eyes also had histopathologic examination. Eighty-seven eyes with a 3-piece round-edged IOL, 43 with a 3-piece square-edged IOL, 26 with a 1-piece plate IOL, and 1 with an accommodating IOL design were included in the analyses of capsular bag opacification. Comparison between 3-piece round-edged IOLs and square-edged IOLs showed statistically significant differences in central posterior capsule opacification (PCO) (P=.0001687) and peripheral PCO (P<.0001). In eyes with square-edged IOLs, PCO had a tendency to start in areas without capsulorhexis coverage of the optic. Twenty-one of 26 eyes with a silicone plate IOL had a neodymium:YAG posterior capsulotomy for dense PCO. This first study using pseudophakic human cadaver eyes that includes a significant number of modern 3-piece silicone IOLs with square optic edges confirmed the role of this design in the prevention of PCO. No author has a financial or proprietary interest in any material or method mentioned.

Visual control of walking velocity

Even if optical correlates of self-motion velocity have already been identified, their contribution to the control of displacement velocity remains to be established. In this study, we used a virtual reality set-up coupled to a treadmill to test the role of both Global Optic Flow Rate (GOFR) and Edge Rate (ER) in the regulation of walking velocity. Participants were required to walk at a constant velocity, corresponding to their preferred walking velocity, while eye height and texture density were manipulated. This manipulation perturbed the natural relationship between the actual walking velocity and its optical specification by GOFR and ER, respectively. Results revealed that both these sources of information are indeed used by participants to control walking speed, as demonstrated by a slowing down of actual walking velocity when the optical specification of velocity by either GOFR or ER gives rise to an overestimation of actual velocity, and vice versa. Gait analyses showed that these walking velocity adjustments result from simultaneous adaptations in both step length and step duration. The role of visual information in the control of self-motion velocity is discussed in relation with other factors.

Reduction of Nd:YAG Capsulotomy Rates After Implantation of a Single-Piece Acrylic Hydrophilic Intraocular Lens with 360° Squared Optic Edge: 24-Month Results

Posterior capsule opacification remains a significant problem following cataract surgery. The aim of the study was to evaluate the incidence of symptomatic posterior capsule opacification requiring Nd:YAG capsulotomy in patients who underwent cataract extraction and implantation of the Rayner C-flex 570C intraocular lens (IOL) (Rayner Intraocular Lens, Ltd., Sussex, UK). A retrospective study of 3,461 eyes that underwent cataract extraction and insertion of the Rayner C-flex IOL from January 2004 to December 2005. The cases that received Nd: YAG capsulotomies were evaluated. Over a 24-month period, 3,461 Rayner C-flex IOLs were implanted. Nd:YAG capsulotomy was performed in 58 of these cases. The rate of Nd:YAG capsulotomy was 0.6% at 12 months and 1.7% at 24 months. The mean time to Nd:YAG capsulotomy was 9.3 months (range: 1.3 to 22.7 months). The follow-up period was 5.3 to 29.0 months. The incidence of symptomatic posterior capsule opacification with the Rayner C-flex IOL is low.

WE-C-BRA-09: A Monte Carlo Method for Assessing Targeting Error in an Ophthalmological Stereotactic Radiosurgical Device

Purpose: To propose and demonstrate a Monte Carlo‐based method of assessing the targeting uncertainty of an ophthalmologic‐specific stereotactic radiosurgerydevice that provides a physically realistic assessment of end‐to‐end uncertainty in targeting accuracy. Using this method, the minimum acceptable an ongoing European clinical trial in the treatment of macular degeneration, separation between optic disc (organ at risk) and fovea (target) was calculated for Method and Materials: All sources of uncertainty in targeting were estimated in categories that include mechanical precision, machine alignment, calibration error, patient motion, and biometric uncertainty. These sources were characterized in terms of their magnitude of error as well as the resulting two‐dimensional shape of their uncertainty distribution on the retina, such as Gaussian, constant, or random. Once uncertainties were characterized, sample “treatments” were simulated by choosing a random magnitudes and directions for each source of error. After statistical noise was adequately reduced, an uncertainty distribution resulted that described the probabilistic position of the beam on the retina. Armed with this distribution, the probability that the proximal portion of the optic disc could receive a dose greater than a threshold could be calculated and a patient eligibility criterion defined. Results: Using this technique, a minimum acceptable fovea to optic disc edge distance was calculated for patients eligible for the radiation treatment of macular degeneration using this SRSdevice.Conclusion: For complex, multi‐dimensional systems this method is more straightforward than the traditional Taylor's expansion method of uncertainty propagation. It explicitly takes into account the non‐normal distribution of most input uncertainties and, as the result itself is a multi‐dimensional probability distribution, provides more insight than a single number like a standard deviation. It allows the user to explicitly select an acceptable risk and tailor the operational parameters to achieve that. Conflict of Interest: Research sponsored by Oraya Therapeutics

Pattern of posterior capsule opacification models 2 years postoperatively with 2 single-piece acrylic intraocular lenses

To compare posterior capsule opacification (PCO) in eyes with 1 of 2 models of 1-piece acrylic intraocular lenses (IOLs). Ambulatory surgery center. This paired-eye study evaluated patients who had implantation of a Tecnis AAB00 IOL with a continuous optic edge in 1 eye and an AcrySof SA60AT or SN60AT IOL with an interrupted optic edge in the fellow eye. Exclusion criteria were anterior capsule overlap onto the IOL optic of fewer than 360 degrees, neodymium:YAG laser capsulotomy, postoperative time fewer than 24 months or more than 30 months, pseudoexfoliation, glaucoma, history of iritis, and surgical complications that would affect the assessment of PCO. Posterior capsule opacification was assessed using the Evaluation of Posterior Capsular Opacification (EPCO) system on a scale of 0 (none) to 4 (severe opacity with a darkening effect). In 13 of 14 patients, the eye with the interrupted-edge IOL had a higher EPCO score than the eye with the continuous-edge IOL. The mean EPCO score was 0.39 and 0.08, respectively; the difference was statistically significant (P = .012). The PCO density was greater in eyes with the interrupted-edge IOL, with 35% having an EPCO score of 3 or 4; no eye with a continuous-edge IOL had a score that high. Eyes with an IOL with a continuous 360-degree square edge had significantly less PCO than eyes with an IOL with a square edge that was interrupted at the optic-haptic junction.

Retrospective ultrasound biomicroscopic analysis of single-piece sulcus-fixated acrylic intraocular lenses

To evaluate the anatomic location of the haptic and optic of single-piece sulcus-fixated intraocular lenses (IOLs) and their proximity to the iris and ciliary body using ultrasound biomicroscopy (UBM). Iladevi Cataract & IOL Research Center, Ahmedabad, India. This retrospective study comprised eyes that had primary sulcus implantation of a single-piece IOL. Eyes had an intact anterior capsulorhexis that could provide uniform IOL support and a preoperative anterior chamber depth (ACD) greater than 2.7 mm. The fixation site of the haptics, distance between the optic edge and iris, optic tilt, anterior chamber angle (ACA), central ACD, and ciliary body edema were evaluated by UBM. The time from surgery to UBM examination was 7 to 85 months. Both haptics were in the sulcus in 7 of the 10 eyes, 1 haptic was abutting the iris and the other was in the sulcus in 2 eyes, and both haptics were embedded in ciliary body in 1 eye. The mean distance between the optic edge and iris was 0.16 mm +/- 0.07 (SD), 0.15 +/- 0.03 mm, and 0.38 mm, respectively. The mean ACA was 40.2 +/- 4.5 degrees (range 30.9 to 45.2 degrees), 34.1 +/- 4.5 degrees, and 44.1 degrees, respectively. The mean ACD was 3.47 +/- 0.24 mm, 3.50 +/- 0.23 mm, and 3.57 mm, respectively. No eye had optic tilt or ciliary body edema. Implantation of both haptics in the sulcus was not achieved in all eyes. The haptics and optics remained in close proximity to the posterior iris surface.

Objective analysis of toric intraocular lens rotation and centration

To assess the repeatability of an objective image-analysis technique to determine intraocular lens (IOL) rotation and centration. Six European ophthalmology clinics. Eyes with an Akreos AO aspheric IOL with orientation marks were imaged. A masked observer rated image quality. The axis of rotation was determined from a line bisecting the IOL orientation marks. This was normalized for rotation of the eye between visits using the axis bisecting 2 consistent conjunctival vessels or iris features. The center of ovals overlaid to circumscribe the IOL optic edge and the pupil or limbus were compared to determine IOL centration. Intrasession repeatability was assessed in a subgroup of eyes and the variability of repeated analysis examined. The SD of intrasession repeatability was +/-0.79 degrees for IOL rotational stability, +/-0.10 mm for horizontal centration, and +/-0.10 mm for vertical centration. The SD of repeated-analysis variability of the same image was +/-0.70 degrees, +/-0.20 mm, and +/-0.31 mm, respectively. The mean eye rotation (absolute) between visits was 2.23 degrees +/- 1.84 (SD) (10% >5 degrees rotation) using 1 set of consistent conjunctival vessels or iris features and 2.03 +/- 1.66 degrees (7%>5 degrees rotation) using the mean of 2 sets (P = .13). Poorer image quality resulted in larger apparent absolute IOL rotation (r = -0.45, P<.001). Objective analysis of digital retroillumination images allowed sensitive assessment of IOL rotation and centration stability. Eye rotation between images can lead to significant errors if not taken into account. Image quality is important to analysis accuracy.

Interventions for preventing posterior capsule opacification.

Posterior capsule opacification (PCO) remains the most common long-term complication after cataract surgery. It can be treated by Nd:YAG laser capsulotomy, however this may lead to other complications and laser treatment is not available in large parts of the developing world. Therefore, many studies try to find factors influencing the development of PCO. To summarise the effects of different interventions to inhibit PCO. These include modifications of surgical technique and intraocular lens (IOL) design, implantation of additional devices and pharmacological interventions. We searched CENTRAL, MEDLINE, EMBASE, LILACS in March 2009 and reference lists of identified trial reports. We included only prospective, randomised and controlled trials with a follow-up time of at least 12 months. Interventions included modifications in surgical technique explicitly to inhibit PCO, modifications in IOL design (material and geometry), implantation of additional devices and pharmacological therapy compared to each other, placebo or standard treatment. We extracted data and entered it into RevMan. We compared visual acuity data, PCO scores and YAG capsulotomy rates and performed a meta-analysis when possible. Sixty six studies were included in the review. The review was divided into three parts. 1. Influence of IOL optic material on the development of PCO. There was no significant difference in PCO development between the different IOL materials (PMMA, hydrogel, hydrophobic acrylic, silicone) although hydrogel IOLs tend to have higher PCO scores and silicone IOLs lower PCO scores than the other materials. 2. Influence of IOL optic design on the development of PCO. There was a significantly lower PCO score (-8.65 (-10.72 to -6.59), scale 0 to 100) and YAG rate (0.19 (0.11 to 0.35)) in sharp edged than in round edged IOLs, however not between 1-piece and 3-piece IOLs. 3. Influence of surgical technique and drugs on the development of PCO. There was no significant difference between different types of intraoperative/postoperative anti-inflammatory treatment except for treatment with an immunotoxin (MDX-A) which led to a significantly lower PCO rate. Due to the highly significant difference between round and sharp edged IOL optics, IOLs with sharp (posterior) optic edges should be preferred. There is no clear difference between optic materials. The choice of postoperative anti-inflammatory treatment does not seem to influence PCO development.

Ultrasonic Doppler measurements of blood flow velocity of rabbit retinal vessels using a 45-MHz needle transducer

The purpose of this study is to measure blood flow velocity of rabbit retinal vessels using a 45-MHz ultrasonic Doppler system with a needle transducer. A high-frequency pulsed Doppler system that utilizes a 45-MHz PMN-PT needle transducer was developed to measure retinal blood flow velocity in situ. The pulsed Doppler allowed the differentiation of retinal from choroidal blood flow velocity. The needle transducer was inserted into the vitreous cavity through a 20-gauge incision port to access the retinal vessels. The first phase of the experiment evaluated the reproducibility of the measurements. The second phase measured velocities at four positions from the optic disc edge to the distal part of each vessel in nine eyes for the temporal and six eyes for the nasal portions. The angle between the transducer and the retinal vessel at each site was measured in enucleated rabbit eyes to estimate and compensate for measurement errors. In the first phase, the average measurement error was 5.97 +/- 1.34%. There was no significant difference comparing all eyes. In the second phase, the velocities gradually slowed from the disc edge to the distal part, and temporal velocities were faster than nasal velocities at all measurement sites. This study demonstrated the feasibility of reliably measuring retinal blood flow velocity using a 45-MHz ultrasonic Doppler system with a needle transducer.