Edge Of Lens Research Articles

Characterization of Soft Contact Lens Edge Fitting Using Ultra-High Resolution and Ultra-Long Scan Depth Optical Coherence Tomography

To characterize the edge fitting of soft contact lenses using ultra-high resolution optical coherence tomography (UHR-OCT) and ultra-long scan depth optical coherence tomography (UL-OCT). A total of 20 participants (11 men, 9 women; mean age, 32.3 years) were recruited. Four different types of soft contact lenses were randomly fitted to both eyes of each subject on two separate visits. After 30 minutes, the horizontal meridians of the corneal center, midperiphery, and limbus were imaged by UHR-OCT. UL-OCT imaged each lens in vitro and the ocular surface of a physical model eye. Angle-edged lenses had significantly less conjunctival buildup than did round-edged lenses (P = 0.008). Limbal post-lens tear film gaps were present in 42% of the eyes, with the round-edged lenses having the most at 68%. Similarly, post-lens tear film gaps at the corneal mid-periphery were present in 47% of all eyes, with the round-edged lens having the most at 75%. Mismatches between the lens and the ocular surface were simulated based on UL-OCT images of the in vitro lenses and the model eye. The existence of tear film gaps and touching points were predicted in the simulation. The soft contact lens edge fitting was characterized by the conjunctival buildup and tear film gaps. Different types of contact lenses presented different levels of conjunctival buildup as well as different frequencies of tear film gaps. The findings by UHR-OCT were predicted in the simulation by UL-OCT. The application of these new technologies may open new ways of designing lenses and evaluating their fit.

SU‐E‐T‐298: Re‐Evaluation of Transmissions for a Commercial Tungsten Eye Shield in Electron Beams Using Radiochromic Film

Purpose: To re‐evaluate the transmission factors for a commercial tungsten eye shield used in 6 and 9 MeV electron beams based on the dose to the lens edge instead of the dose at the lens center using radiochromic film Methods: The eye shields have thickness of 2 or 3 mm with a 0.5 mm or 1 mm thick aluminum cap provided to reduce backscatter. The doses to the lens edge were measured at 3 mm depth below the shields and 5 mm from the central axis using Gafchromic® film. The doses were then normalized to the dose to dmax under the same setup without eye shields in place to generate the transmission factors. In contrast, the transmission factors referred by the manufacturer were determined with the lens dose measured at 3 mm depth along the central axis Results: The transmission factors are approximately 10 to 50% higher for a 6 MeV beam and 10 to 20% higher for a 9 MeV beam than the factors referred by the manufacturer. Transmissions are in general larger for smaller eye shields. In addition, one millimeter aluminum caps can increase the transmissions significantly for a 6 MeV beam. Transmission profiles at 3 mm depth in phantom are in the same shape regardless of their sizes. Transmissions at the edge of the shielded area at 3 mm depth were determined Conclusions: For internal eye shields transmission factors determined based on doses to lens edge can be significantly larger than the ones determined based on doses to the center of the lens. Transmission profiles reported here can aid dose estimation in some other situations. Relatively larger eye shields are suggested where clinically acceptable. The 0.5 mm aluminum caps are preferable in a 6 MeV beam.

A Novel Endoscope to Treat Bladder Stone

Purpose: To recommend a novel endoscope, Aihua (AH)-1 stone removal system (SRS), and introduce the structure and function to treat bladder stones. Materials: SRS is composed by illuminant and imaging component, continuous-flow component, a jaw to grab and extract stone, lithotripsy tube, handle, and sheath. The entire device is usually attached to a video camera to provide vision for the surgeon. During surgical procedure, first 26F SRS was inserted into bladder to search stone. Then, stone was grabbed and fixed using jaw, and lithotripsy was performed with holmium laser or pneumatic lithotripter through lithotripsy tube. Fragments could be extracted using jaw through sheath synchronously. If there were more residual small fragments, Ellik evacuator could be connected with sheath to wash out them. Finally, resectoscope was inserted in urethra to perform transurethral resection of the prostate (TURP). Between January 2008 and July 2010, 37 cases of bladder stone with benign prostatic hyperplasia were treated by SRS combined with TURP. The device was designed by Aihua Li, M.D., and manufactured by Hangzhou Tonglu Shikonghou Medical Instrument Co., Ltd. Results: In the experiment in vitro, sphere >60 mm in diameter can be fixed with jaw by occlusive force and downward pressure, sphere <15 mm can be grabbed directly, and sphere <8 mm can be extracted through sheath. Inner diameter of the sheath is 8.2 mm, and it can be connected with Ellik evacuator. The lithotripsy tube is 1.4 mm in inner diameter, by which, holmium laser fiber or pneumatic lithotripter probe can be transited to perform lithotripsy. In the clinical study, the designed multiple functions had been showed in cystolithotripsy. The jaw, like a ring in longitudinal, is located at the front of objective lens and open downward, and the central part still is a circular cavity when it is closed. The lithotripsy tube is located at the lower edge of objective lens, which facilitates fragmentation in direct vision. Two jaw pieces are frame-shaped, which is favorable to grab and fix stone. Two little bars are installed at the far end of jaw so that it can be used to extract stone fragments through sheath as a trawler and more fragments can be extracted at one time. On other hand, Ellik evacuator can be connected with sheath to wash out small fragments. The principle of swing flow is applied in design that makes the device to collect fragments automatically. In stone fragmentation, holmium laser fiber or pneumatic lithotripter probe can be transited through lithotripsy tube to crush stones. Stones in 19 patients were <2 cm, the mean size was 1.36 ± 0.33 (0.7–1.8) cm, and stone removal time was 6.32 ± 4.44 min. Among these patients, those with multiple stones were five (35.71%), the stone number was 3.2 ± 1.30, and mean size was 1.24 ± 0.25 cm. Stones in other 18 patients were >2 cm, the mean size was 3.49 ± 1.32 (2.0–6.4) cm, and stone removal time was 32.88 ± 24.21 min. Among these patients, those with multiple stones were six (37.50%), the stone number was 6.67 ± 6.67, and mean size was 2.51 ± 0.93 cm. TURP was performed first in three patients for urethral stricture or larger median lobe of prostate. No significant complication was found in the surgical procedure. However, a patient with multiple stone who was 97 years old, with a largest stone in 5.8 cm, second lager stone in 2.2 cm, and other 15 stones <2 cm, undergone a second endoscopic procedure at 14 day postoperatively for surgical safety. Conclusion: SRS is a novel endoscope with multiple functions to treat bladder stone. Our study shows that multiple functions such as fixing stone, crushing stone, automatically gathering stone, extracting stone, washing out stone, and continuous-flow can be expected when SRS is applied in cystolithotripsy. Especially, it can be used to automatically collect stone by swirling flow and extract more stones by jaw through sheath at one time, which can effectively reduce stone removal time and surgical damage to urethral mucosa. SRS combined with TURP is an effective and rapid modality to treat bladder stone with benign prostatic hyperplasia.1–6 This minimally invasive endoscopic procedure appears to be safe and efficient, and could expand the range of operating indications on cystolithotripsy. Additional randomized trials comparing other endoscopes are warranted to delineate the best device to manage bladder stone.7–11 No competing financial interests exist. Runtime of video: 9 mins 20 secs

Coastal Caves in Bahamian Eolian Calcarenites: Differentiating Between Sea Caves and Flank Margin Caves Using Quantitative Morphology

Coastal areas on carbonate islands commonly contain two types of caves: sea caves developed by wave erosion processes, and flank margin caves developed by dissolution at the edge of the fresh-water lens. Differentiating sea caves and flank margin caves in coastal settings is important, but can it be done reliably and quantitatively? Current methods use the degree of intricate wall-rock dissolution and the presence or absence of dense calcite speleothems to separate the two cave types. This study reports how analysis of cave maps creates three separate tools to differentiate coastal caves: area to perimeter ratio, entrance width to maximum width ratio, and rectangle short axis to long axis ratio. The study also presents some of the first sea cave data from eogenetic carbonate islands, specifically eolian calcarenites. The morphological and geometrical comparisons between Bahamian flank margin cave and sea cave maps using the three tools allows the two cave types to be statistically differentiated. The Bahamian sea cave data were also compared to sea cave data from California and Maine to demonstrate that Bahamian sea caves have a unique quantitative signature based on the youth and homogeneity of the host eolian calcarenite rock. The Bahamian sea cave data also indicate that sea cave formation may not be solely determined by differential rock weaknesses, as reported in the literature, but may also be a result of wave dynamics such as constructive interference.

Application of optical coherence tomography to automated contact lens metrology

Optical coherence tomography (OCT) is a nondestructive imaging modality with the potential to make quantitative spatial measurements. OCT's noncontact nature, sensitivity to small refractive index mismatches, and micron-scale resolution make it attractive for contact lens metrology, specifically, measuring prism. Prism is defined as the maximum difference in thickness of the contact lens, measured over a full 360 deg of rotation, at a fixed distance from the contact lens edge. We develop and test a novel algorithm that automatically analyzes OCT images and calculates prism. Images are obtained using a Thorlabs OCT930SR OCT system. The OCT probe is fastened to an automated rotation stage that rotates 360 deg in small increments (typically 10 deg) to acquire OCT images of the edge of the contact lens around the entire circumference. The images are 1.6 mm in optical depth (512 pixels) and 2 mm wide (1000 pixels). Several sets of images are successfully analyzed. The prism measured for a toric lens is 42 microm, which is in line with design parameters. Thickness measurements are repeatable with a standard deviation of 0.5 microm and maximum range of 1.8 microm over ten image sets. This work demonstrates the possibility of using OCT to perform nondestructive contact lens metrology.

In Situ Visualization of Tears on Contact Lens Using Ultra High Resolution Optical Coherence Tomography

To demonstrate the capability of directly visualizing the tear film on contact lenses using optical coherence tomography (OCT). Six eyes of three healthy subjects wearing PureVision and ACUVUE Advance soft and Boston RGP hard contact lenses were imaged with a custom built, high speed, ultra-high resolution spectral domain optical coherence tomograph. Refresh Liquigel was used to demonstrate the effect of artificial tears on the tear film. Ultra high resolution images of the pre- and post-lens films were directly visualized when each lens was inserted onto the eye. After the instillation of artificial tears during lens wear, the tear film was thicker. The post-lens tear film underneath the lens edge was clearly shown. Interactions between the lens edges and the ocular surface were obtained for each of the lens types and base curves. With a contrast enhancement agent, tear menisci on the contact lenses around the upper and lower eyelids were highlighted. With hard contact lenses, the tear film was visualized clearly and changed after a blink when the lens was pulled up by the lid. Ultra-high resolution OCT is a potentially promising technique for imaging tears around contact lenses. This successful demonstration of in situ post-lens tear film imaging suggests that OCT could open a new era in studying tear dynamics during contact lens wear. The novel method may lead to new ways of evaluating contact lens fitting.

A liquid lens-based broadband variable fiber optical attenuator

To the best of our knowledge, proposed is the first variable fiber optical attenuator (VFOA) using an electronically controlled variable focus liquid lens. The approach uses the changes in the radius of curvature of the liquid lens edge to enable an electronically controlled optical wedge that produces a varying beam tilt angle. In effect, changing beam tilt within a single mode fiber (SMF) lens free space coupling assembly leads to a polarization independent broadband VFOA design. The demonstrated VFOA experiment shows broadband operation over the 1530–1560 nm C-Band with a 40 dB dynamic range, <0.5 dB resolution, 0.3 dB polarization dependant loss, 4.3 dB fiber-to-fiber optical loss, 3 dB optical bandwidth from 1510 nm to 1700 nm, and switching time of <100 ms. Applications for this VFOA include use in hand held test and measurement equipment.

Miniaturized CMOS Imaging Module with Real-time DSP Technology for Endoscope and Laryngoscope Applications

Miniaturized video camera is a key component in modern medical devices such as endoscopes or other minimally invasive instruments. Here we present a new imaging module which is so small that it can fit through the instrument channels of conventional endoscopes and laryngoscopes. This imaging module includes a 1/18-in. CMOS image sensor and a small integrated lens with field of view of 120°. A Blackfin DSP is used for real-time video processing, including lens distortion compensation, white balance, auto exposure and edge enhancement. The output video signals are displayed on a color LCD monitor. Two white LEDs provide lighting condition. The tip of the imaging module is packaged in a cylinder of diameter 2.5 mm, making many medical applications such as intubation and endoscopy less invasive. It can also be used in machine vision, security and surveillance where small size is important.

Fan-Beam Millimeter-Wave Antenna Design Based on the Cylindrical Luneberg Lens

A new design of two-dimensional cylindrical Luneberg lens is introduced based on TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode propagation between parallel plates, with special focus on ease of manufacturing. The parallel plates are partially filled with low cost polymer material (Rexolite epsiv <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 2.54) to match Luneberg's law. A planar linear tapered slot antenna (LTSA) is inserted into the air region between the parallel plates at the edge of the Luneberg lens as a feed antenna, with fine positioning to the focal point of the Luneberg lens to optimize the antenna system performance. A combined ray-optics/diffraction method is used to obtain the radiation pattern of the system and results are compared with predictions of a time domain numerical solver. Measurements done on a 10-cm Luneberg lens designed for operation at 30 GHz agree very well with predictions. For this prototype, 3-dB E- and if-plane beamwidths of 6.6deg and 54deg respectively were obtained, and the sidelobe level in the E-plane was -17.7-dB. Although the parallel plate configuration should lead to a narrow band design due to the dispersion characteristics of the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode, the measurement results demonstrate broadband characteristics with radiation efficiencies varying between 43% and 72% over the tested frequency band of 26.5-37 GHz. The designed cylindrical Luneberg lens can be used to launch multiple beams by implementing an arc array of planar LTSA elements at the periphery of the lens, and can be easily extended to higher mm-wave frequencies.

Spontaneous oscillations of a sessile lens

When an oil drop is placed on a water surface, it assumes the form of a sessile lens. We consider the curious behaviour that may arise when the oil contains a water-insoluble surfactant: the lens radius oscillates in a quasi-periodic fashion. While this oscillatory behaviour has been reported elsewhere, a consistent physical explanation has yet to be given. We present the results of an experimental investigation that enable us to elucidate the subtle mechanism responsible. Videomicroscopy reveals that the beating behaviour is generated by a subtle process of partial emulsification at the lens edge and sustained by evaporation of surfactant from the water surface.

Determination of the oxygen permeability (Dk) of contact lenses with a fiber-optic luminescent sensor system

An optical sensing system, alternative to current electrochemical techniques, has been developed for determining the oxygen permeability (Dk) of rigid gas-permeable contact lenses. The novel sensor is based on kinetic measurements of the oxygen partial pressure inside a chamber sealed by the sample contact lens, where a thin luminescent O 2-sensitive film is placed. The standard equation for calculating the Dk value of the lens material has been adapted to the optical technique and a fitting procedure of the sensor response has been developed to achieve the maximum accuracy and precision. Unlike the electrochemical techniques, the optical sensor is unaffected by the contact lens thickness and the lens edge and boundary effects. Therefore, the latter does not require lengthy measuring procedures for extracting the actual Dk values. The optical sensor system has been applied to oxygen permeability determinations of commercial contact lenses of nominal Dk values equal to 17 and 36 ANSI units of 10 −11 cm 3 cm/s cm 2 mmHg.

Edinger-Westphal and pharmacologically stimulated accommodative refractive changes and lens and ciliary process movements in rhesus monkeys

During accommodation, the refractive changes occur when the ciliary muscle contracts, releasing resting zonular tension and allowing the lens capsule to mold the lens into an accommodated form. This results in centripetal movement of the ciliary processes and lens edge. The goal of this study was to understand the relationship between accommodative refractive changes, ciliary process movements and lens edge movements during Edinger-Westphal (EW) and pharmacologically stimulated accommodation in adolescent rhesus monkeys. Experiments were performed on one eye each of three rhesus monkeys with permanent indwelling electrodes in the EW nucleus of the midbrain. EW stimulated accommodative refractive changes were measured with infrared photorefraction, and ciliary process and lens edge movements were measured with slit-lamp goniovideography on the temporal aspect of the eye. Images were recorded on the nasal aspect for one eye during EW stimulation. Image analysis was performed off-line at 30 Hz to determine refractive changes and ciliary body and lens edge movements during EW stimulated accommodation and after carbachol iontophoresis to determine drug induced accommodative movements. Maximum EW stimulated accommodation was 7.36 ± 0.49 D and pharmacologically stimulated accommodation was 14.44 ± 1.21 D. During EW stimulated accommodation, the ciliary processes and lens edge moved centripetally linearly by 0.030 ± 0.001 mm/D and 0.027 ± 0.001 mm/D, with a total movement of 0.219 ± 0.034 mm and 0.189 ± 0.023 mm, respectively. There was no significant nasal/temporal difference in ciliary process or lens edge movements. 30–40 min after pharmacologically stimulated accommodation, the ciliary processes moved centripetally a total of 0.411 ± 0.048 mm, or 0.030 ± 0.005 mm/D, and the lens edge moved centripetally 0.258 ± 0.014 mm, or 0.019 ± 0.003 mm/D. The peaks and valleys of the ciliary processes moved by similar amounts during both supramaximal EW and pharmacologically stimulated accommodation. In conclusion, this study shows, for the first time, that the ciliary processes and lens edge move centripetally, linearly with refraction during EW stimulated accommodation. During pharmacological stimulation, the ciliary processes move to a greater extent than the lens edge, confirming that in adolescent monkeys, lens movement limits the accommodative optical change in the eye.

Laser Suture Lysis Through Thick Blebs Using the Blumenthal Lens

Laser suture lysis is commonly performed after trabeculectomy and is titrated to control postoperative flow through the filter to a target intraocular pressure. 1 Originally, the flat edge of a Zeiss 4-mirror lens was used to compress the conjunctiva and Tenon capsule to view the sutures. The Hoskins lens designed for suture lysis improved the view and allowed eyelid elevation for better exposure. The Ritch suture lysis lens was designed to provide good compression and a reasonably wide field of view that helps in locating sutures. 2 Recently, the Blumenthal lens was introduced for suture lysis.

Spectral optical coherence tomography: a new imaging technique in contact lens practice

Spectral optical coherence tomography (SOCT) is a new non-invasive, non-contact, high-resolution technique, which provides cross-sectional images of objects that weakly absorb and scatter light. The aim of this article is to demonstrate the application of SOCT to imaging of eyes fitted with contact lenses. Nine eyes of six different subjects fitted with various contact lenses have been examined with a slit-lamp and a prototype SOCT instrument. Our SOCT system provides high-resolution (4-6 mum longitudinal, 10 mum transversal) tomograms composed of 3000-5000 A-scans with acquisition time of 100-250 ms. The quality of the images is adequate for detailed evaluation of contact lens fit. Design, shape and lens edge position were assessed, and complications of contact lens wear could be visualized. Thickness of the lens, corneal epithelium and stroma as well as the space between the lens and the eye surface have been measured. SOCT allows high-resolution, cross-sectional visualization of the eye fitted with a contact lens. The ability to carry out a detailed evaluation of the fitting relationship between the lens and the ocular surface might be useful in research and optometric practice. SOCT can also be helpful in diagnosis, evaluation and documentation of contact lens complications.

Hyperopic LASIK Following Intracorneal Hydrogel Lens Explantation

To report hyperopic LASIK results after intracorneal hydrogel lens explantation in a bilateral hyperopic patient. Slit-lamp examination showed diffuse corneal opacity around the lens edge and over the anterior lens surface affecting both eyes with uncorrected visual acuity of 0.4 in the right eye and 0.5 in the left eye. The intracorneal hydrogel lenses were explanted, and 6 months later hyperopic LASIK using the Schwind ESIRIS excimer laser (Schwind, Kleinostheim, Germany) was performed after lifting the same flap for the intracorneal hydrogel lens implantation. Six months after hyperopic LASIK, visual acuity recovered to the initial preoperative best spectacle-corrected levels: right eye 0.8 with +1.50 D sphere and left eye 0.9 with +1.00 -0.50 x 90 degrees. Central corneal transparency also fully recovered. Hyperopic LASIK is a possible alternative after intracorneal hydrogel lens explantation in hyperopic eyes.

Non-contact sound speed measurement by optical probing of beam deflection due to sound wave

We report a non-contact and non-invasive method of sound speed measurement by optical probing of deflected laser beam due to normally incident degenerated shock wave. In this study the shock wave from an exploding wire was degenerated to an ordinary sound wave at the distance exceeding 0.23 m. Temporal resolution of the deflected beam signal was improved by passing through an adequate electronic high-pass filter, as a result we obtained a better temporal resolution than that of the acoustic pressure detection by PZT transducer in terms of rising time. The spatial resolution was improved by passing the refracted beam signal into the edge of focusing lens to make a larger deflection angle. Sound speed was calculated by monitoring the time of flight of transient deflected signal at the predetermined position. Sound speed has been measured in air, distilled water and acryl, agreed well with the published values. The sound speed measured in the solution of glycerin, magnesium sulfate (MgSO 4), and dimethylformamide with various mole fractions also agrees within 3% of relative error with those measured in the present work by ultrasonic pulse echo method. The results suggest that the method proposed is to be reliable and reproducible.

Functional and Structural Outcomes Following Lensectomy for Ectopia Lentis

High refractive errors and optical aberrations reduce vision when the lens edge bisects the pupil. We studied outcomes of eyes with ectopia lentis following lensectomy. Charts of 11 consecutive patients with bilateral ectopia lentis who underwent lensectomy-anterior vitrectomy in at least one eye from 1985 to 2004 were reviewed. Eighteen eyes were operated. One eye was excluded due to short-term follow-up (<2 years). Mean age at surgery was 7.7 years (2 to 17 years). Median follow-up after lensectomy was 10 years (range 2 to 16 years). Six eyes were followed for 6 to 10 years, and another six eyes were followed for 11 to 16 years. Patient diagnoses included Marfan syndrome (nine eyes), ectopia lentis et pupillae (three eyes), simple ectopia lentis (two eyes), homocystinuria (two eyes), and sporadic spherophakia (one eye). Preoperative best-corrected visual acuity (BCVA) ranged from 20/60 to light perception, and postoperative BCVA ranged from 20/20 to 20/100 (14 eyes were at least 20/30). Complications included posterior vitreous detachment (two eyes, 12%), glaucoma (one eye, 6%), transient ocular hypertension (one eye, 6%), wound dehiscence with iris incarceration (one eye, 6%), transient vitreous hemorrhage (one eye, 6%), and peripheral anterior synechiae (one eye, 6%). No retina detached. Our cohort of patients with long-term follow-up shows that pars plana lensectomy can be successful in restoring vision when conservative measures fail.

The biomechanics of rigid contact lens removal

The removal of rigid contact lenses from the eye, using the eyelids, is a relatively simple procedure. However, there is a sequence of biomechanical events underlying this procedure which are not well understood. By using high-speed videokeratoscopy (50 Hz), we have shown that during the lid-pull procedure the cornea typically shows a significant increase in with-the-rule astigmatism by an average of 2.19 D (axial power). The average increase in steep K power was 1.22 D (S.D. ±1.05 D) and the average decrease in flat K power was 0.97 D (S.D. ±1.05 D). This change in corneal topography increases the edge lift of the lens at 12 and 6 O’clock locations of the lens, enhancing the removal process. When the subject blinks, as the lid margins reach the lens edge, the lens flexes and the eye retracts by an average of 0.66 mm (S.D. ±0.27 mm). This retraction again enhances the act of lens removal.

Optical coherence tomography assessment of capsule closure after cataract surgery

To develop a technique for documenting and quantifying capsule bend formation in pseudophakic eyes, evaluate when the anterior and posterior lens capsules become completely apposed to the optic, and determine how soon a capsule bend is created at the optic edge of an intraocular lens (IOL) after cataract surgery. Medical University of Vienna, Department of Ophthalmology, Vienna, Austria. This prospective study comprised 33 eyes of 33 patients with age-related cataract who were scheduled to have cataract surgery. All eyes had phacoemulsification with implantation of 1 of 3 types of open-loop IOLs: 1-piece acrylic (SA60AT, Alcon), 3-piece acrylic (AcrySof MA60BM, Alcon), or 3-piece silicone (911A, AMO). Each group included 11 eyes. One and 3 days and 1, 2, 3, and 4 weeks after surgery, contact between the lens capsule and IOL optic as well as capsule bend formation were evaluated using optical coherence tomography (OCT). The postoperative times at which the capsule came into contact with the IOL optic and when the capsule bend formed were determined. One day postoperatively, the mean distance between the anterior capsule and the IOL was 197 microm in the 1-piece acrylic IOL group, 161 microm in the 3-piece acrylic IOL group, and 220 microm in the 3-piece silicone IOL group. The posterior capsule was in contact with the IOL on the same day or earlier than the anterior capsule in 28 patients (85%). Postoperatively, the capsule bend formed at a mean of 10 days in the 1-piece acrylic group, 13 days in the 3-piece acrylic group, and 15 days in the 3-piece silicone group. The short-term reproducibility of the OCT technique was excellent (r = 0.99). Optical coherence tomography produced cross-sectional tomograms of capsule-IOL contact in the early postoperative period. There was no significant difference in the time to capsule bend formation between the 3 IOLs. However, capsule bend formation at the optic edge occurred earlier with the 1-piece acrylic IOL than with the 3-piece silicone IOL.

The effect of lens edge design versus anterior capsule overlap on posterior capsule opacification

Purpose To determine whether lens edge design or anterior capsule overlap on the intraocular lens (IOL) has greater effect on posterior capsule opacification (PCO). Design Retrospective cohort clinical study. Methods Retrospective. SETTING: Academic clinical practice. PATIENT POPULATION: The patient population consisted of 259 uncomplicated surgical patients (259 eyes) with no confounding comorbidity and at least 1 year of follow-up after surgical placement of a silicone or hydrophobic acrylic lens. OBSERVATION PROCEDURES: Digital retroilluminated photographs were taken to ascertain PCO, anterior capsular opacification (ACO), previous neodymium:YAG capsulotomy and degree of anterior capsule overlap on the IOL optic. MAIN OUTCOME MEASURES: PCO, ACO, YAG capsulotomy rate, and anterior capsule overlap on the IOL optic. Results One hundred forty-eight digital images (74 silicone and 74 acrylic) were measurable for both anterior capsule overlap and PCO. Complete 360 degrees of anterior capsule overlap on the IOL was associated with decreased PCO (P = <.001). A significant negative correlation was found between the degree of anterior capsule overlap and PCO (P = <.001). Evaluation of PCO, and YAG capsulotomy rates were similar between acrylic and silicone lenses. Minimal anterior capsule overlap may also be associated with PCO prevention. Conclusions Implanting a lens with complete anterior capsule overlap on the IOL was found to significantly reduce PCO, which advantage appeared to be greater than PCO prevention by a truncated, sharp edge IOL design.