Light-adjustable Lens Research Articles

Disruptive Innovation and Refractive IOLs: How the Game Will Change With Adjustable IOLs.

The light-adjustable lens is the first Food and Drug Administration (FDA)-approved product from an entirely new category of intraocular lenses (IOLs). The 3-piece foldable silicone light-adjustable lens is implanted through a small incision after phacoemulsification. A slit-lamp-based digital light delivery device is used to adjust and then lock-in the IOL power during the first postoperative month. Up to 4.5 diopters (D) of cylindrical or spherical adjustment can be achieved. This should offer significant advantages in difficult IOL power calculation cases, such as postrefractive eyes. In addition to achieving better refractive accuracy, an adjustable IOL will now allow patients to test and elect a different refractive target postoperatively. This paradigm shift will change how cataract patients choose their refractive objectives, and how ophthalmologists will be able to achieve them. For example, adjustable IOLs may increase the popularity of pseudophakic monovision and bilateral same-day sequential surgery. For those electing adjustable IOL, preoperative patient counseling will change and certain pre- and intraoperative technologies, such as intraoperative aberrometry and digital astigmatic axis marking, would become superfluous.

Astigmatic correction with implantation of a light adjustable vs monofocal lens: a single site analysis of a randomized controlled trial.

To evaluate the light adjustable lens (LAL) vs a standard monofocal lens in achieving target astigmatic refraction and improving postoperative uncorrected distance visual acuity (UDVA). This randomized controlled clinical trial included 40 patients with pre-existing astigmatism and visually significant cataract. Twenty-eight patients received the LAL and 12 control patients received a monofocal intraocular lens (IOL) after cataract extraction at a single institution. The patients with the LAL underwent adjustment by ultraviolet (UV) light postoperatively plus subsequent lock-in procedures and all patients returned to clinic for follow up of study parameters at 6, 9, and 12mo. Manifest refraction, distance visual acuity, and adverse events were recorded at each visit. The mean cylinder before adjustment in eyes with the LAL was -0.89±0.58 D (-2.00 to 0.00 D) and -0.34±0.34 D (-1.25 to 0.00 D) after lock-in (P=1.68x10-8). The mean cylinder in patients with the monofocal lens was -1.00±0.32 D (-1.50 to -0.50 D) at 17-21d postoperatively, which was statistically different from the LAL cylinder post lock-in (P=1.43x10-6). UDVA in the LAL group was 20/20 or better in 79% of patients post lock-in with good stability over 12mo compared with 33% of the control patients with UDVA of 20/20 or better. These results demonstrate that the LAL is more effective in achieving target refractions and improving postoperative UDVA in patients with pre-existing corneal astigmatism than a standard monofocal lens.

A light adjustable lens with injectable optics.

The light adjustable lens (LAL) is an innovative intraocular lens optic composed of partially polymerized macromers with an appropriately bonded photosensitizer. The injectable technology and multifocality associated with the LAL can produce precise refractive correction and, it is hoped, the type of accommodative range that is taken for granted during youth. Combining these technologies with a lens material that behaves like the crystalline lens of 25-year-old could precisely return near and distance vision to older adults.

Newer Intraocular Lenses in Present Day Cataract Surgery

Intraocular lens (IOL) technology has evolved dramatically in recent years with various premium IOLs improving the visual outcome. Toric IOLs with toricity on their posterior surface are able to correct astigmatism but the results depend on the correct axis of placement. Multifocal IOLs have specialized optical properties that can divide light to bring it into focus at more than one point at the same time and are currently the most reliable lenses for attaining both distance and near vision. Accommodating IOLs uses the optic shift principle and depend on the strength of ciliary body for their action. Microincisional IOLs acts by minimizing the surgeon induced astigmatism. Light adjustable lenses allow non-invasive post-operative adjustment of the IOL’s refractive power. Aspheric IOLs reduce the spherical aberrations and provides better image quality and contrast. This is a rapidly evolving field and the future looks promising. *Himanshu Shekhar, Rajesh Sinha

Refractive Results after Implantation of a Light-Adjustable Intraocular Lens in Postrefractive Surgery Cataract Patients

To evaluate whether postoperative refractive power adjustment of a light-adjustable lens (LAL; Calhoun Vision, Inc, Pasadena, CA) improves refractive outcomes in patients who have undergone prior LASIK or photorefractive keratectomy. Retrospective case series. Thirty-four eyes in 21 cataract patients with a mean age of 62.6 ± 9.7 years and a history of myopic corneal refractive surgery were implanted with the LAL during cataract surgery performed at a single clinic in Victoria, Canada. Two weeks after uncomplicated cataract surgery, we used a light delivery device to deliver a spatially resolved 365-nm beam of ultraviolet light to alter the shape of the LAL and hence its refractive power. To obtain the desired refractive change, 1, 2, or 3 adjustments were used. After adjustments, we applied 2 lock-in treatments to the LAL to consume unpolymerized macromeres in the LAL. The final manifest refraction spherical equivalent (MRSE) achieved then was compared with the initial refractive target before LAL implantation. The MRSE to target refraction, mean absolute error of cohort to target refraction, and percentage of cohort within ± 0.25 diopters (D), ± 0.50 D, ± 1.0 D, and more than ± 1.0 D relative to target refraction. The MRSE relative to target refraction after final lock-in was within ± 0.25 D in 74% of eyes, within ± 0.50 D in 97% of eyes, and within ± 1.00 D in 100% of eyes. Mean absolute error was 0.19 D with a standard deviation of ± 0.20 D. In patients with a history of laser refractive surgery, LAL implantation and postimplantation adjustment provide a precise refractive outcome. The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Is There an Endothelial Cell Toxicity of Light-Adjustable Lens UVA Irradiation on the Human Corneal Endothelium?

In cataract and refractive surgery, implantation of a light-adjustable lens (LAL) represents a promising method to noninvasively correct deviation from target refraction. In this method, UVA irradiation is used to induce controlled changes in the form and refraction of the lens. UVA irradiation is known to have a damaging effect on corneal tissue. So far, no studies about the toxicity of LAL treatment on the human corneal endothelium exist. We tested the effect of LAL treatment on human donor endothelium under organ culture conditions. Two pairs of human donor corneas not suitable for transplantation but with good endothelial quality were exposed either to LAL treatment with a target refraction of the maximum adjustable profile for hyperopia with astigmatism (right corneas) or to the white light of the same slit lamp for identical time frames (left corneas). Development of endothelial cell number, morphology and percentage of necrosis was observed. After 6 weeks, histologic analysis was performed. Comparing morphology, cell count, percentage of necrosis, and histologic examination in vitro, no significant differences between right and left corneas could be detected. The maximum dose of UVA irradiation used in LAL treatment was not detrimental for human corneal endothelium in vitro. Further in vivo studies and longer observation periods should be performed for ensuring the safety of LAL treatment as a routine procedure.

The Light Adjustable Lens – A Review

The purpose of this manuscript is to review the design, development and clinical results of the light adjustable lens (LAL). Evolution in techniques, biometry and intraocular lens (IOL) calculation have improved outcomes and increased expectations after cataract surgery. Nevertheless, Imprecise IOL power determinations, pre-existing and surgical-induced astigmatism, and previous corneal refractive surgery continue to limit post-operative uncorrected vision. The LAL was designed to provide a stable, precise correction of refractive errors with a safe, non-invasive post-operative procedure. The concept behind the LAL is based on photochemistry and diffusion. The adjustment occurs when all non-attached solutes equally distribute themselves throughout the optic after irradiation with ultraviolet light that causes the photosensitive macromers to polymerise in the irradiated region. Clinical results have been positive, with the largest series (122 eyes) showing 97 % of patients within 0.25 D of attempted spherical equivalent and 100 % uncorrected vision 20/25 or better. In conclusion, the LAL has demonstrated to be a safe, accurate and reliable method of post-operative, non-surgical correction of residual sphero-cylindrical refractive error.

Combined Correction of Axial Hyperopia and Astigmatism Using the Light Adjustable Intraocular Lens

To determine whether residual spherical and cylindrical errors could be corrected postoperatively using spatially profiled UV light irradiation in patients with axial hyperopia undergoing cataract surgery and implantation of a light adjustable, silicone intraocular lens (LAL). We conducted a prospective, nonrandomized clinical trial. The LALs were implanted in eyes with axial lengths <22.20 mm and were treated with a spatial intensity profile delivered by a digital light delivery device to induce a targeted spherical and cylindrical refractive change postoperatively. Once the desired correction was achieved, the LAL was treated again to lock-in the lens power. We studied 15 eyes of 15 patients with axial hyperopia. The manifest refraction, uncorrected visual acuity (UCVA), and best spectacle-corrected visual acuity (BCVA) were determined with follow-up time of 12 months to determine the achieved refractive corrections and their stability. We measured UCVA, BCVA, achieved versus targeted refractive outcome, and refractive stability with a follow-up time of 12 months. Of 15 eyes, 14 (93%) achieved ± 0.5 diopters (D), and 10 (67%) were within ± 0.25 D of the targeted refractive adjustment up to 12 months postoperative follow-up. Only 1 treated eye showed a change of 0.38 D in manifest spherical equivalent refraction, the remaining 14 eyes showed <0.25 D change between 1 month post lock-in, and at the 3-, 6-, and 12-month postoperative visits. The light-adjustable lens is a promising technology with the potential to reduce the rate of postoperative refractive surprises up to 2 D of spherical and cylindrical errors after cataract surgery. Postoperative refractive errors were successfully corrected with precision and significant improvement in UCVA and without compromising BCVA using the light-adjustable intraocular lens technology. The data demonstrate the stability of the achieved refractive change after the adjustment and lock-in procedures.

Correction of Astigmatism After Cataract Surgery Using the Light Adjustable Lens: A 1-year Follow-up Pilot Study

The management of preoperative and residual astigmatism is critical to obtain optimized uncorrected visual acuity. The aim of this study was to determine whether residual astigmatism could be precisely corrected postoperatively using the Light Adjustable Lens (LAL, Calhoun Vision Inc) and to determine the stability of the adjusted refraction. Ten eyes of 10 patients with cataract and corneal astigmatism between 1.00 and 2.00 diopters (D) were included. After standard phacoemulsification and implantation of the LAL, adjustment and lock-in procedures were completed. Before adjustment and 2 weeks, 6 months, and 1 year after lock-in, a full ophthalmic examination including uncorrected distance acuity (UDVA) and corrected distance visual acuity (CDVA), autorefraction, and manifest refraction was performed. All surgeries, adjustments, and lock-in procedures were performed with no complications. All eyes achieved ±0.50 D of the targeted cylindrical adjustment. Mean spherical equivalent refraction was 0.03±0.84 D before adjustment and -0.06±0.25 D at final follow-up. The cylinder axis remained the same in 60% of eyes and all eyes were stable within 10° rotation at 12-month follow-up. Seven of 10 eyes achieved UDVA of 20/25 or better whereas all eyes achieved UDVA of 20/32 or better. Corrected distance visual acuity remained stable in all eyes. In this pilot study, the LAL proved to be an efficient, predictable, and stable method of managing astigmatism in cataract patients.

Evaluation of the Calhoun Vision UV Light Adjustable Lens Implanted Following Cataract Removal

Evaluation of the Calhoun Vision UV Light Adjustable Lens Implanted Following Cataract Removal

Adjustierung von sphärozylindrischen Refraktionsfehlern bei hyperopen Augen: 6 Monatsergebnisse nach Kataraktchirurgie und Implantation einer lichtadjustierbaren Intraokularlinse

The aim of this study was to determine whether residual spherical and cylindrical errors could be corrected postoperatively in a non-invasive manner using ultraviolet irradiation in patients with axial hyperopia undergoing cataract surgery and implantation of a light-adjustable lens, silicone intraocular lens (LAL) (Calhoun Vision, Pasadena, CA). In a prospective, non-randomised clinical trial at Center for Vision Science, Ruhr University Eye Clinic, Bochum, Germany, 15 eyes of 15 patients with axial hyperopia (less than 22.2 mm) were studied. The manifest refraction, uncorrected visual acuity (UCVA), and best spectacle-corrected visual acuity (BSCVA) were determined with a follow-up time of six months to determine the achieved refractive corrections and their stability. The adjustment and lock-in procedures were well tolerated by patients. Preoperative refraction was in mean + 2.56 D as spherical equivalent, postoperative before adjustment + 1.01 D, one month after lock-in procedure + 0.03 D, after 3 months + 0.12 D and after 6 months 0.0 D (± 0.21 D). 6 months after lock-in all patients reached an uncorrected visual acuity of 20/30 or better, 10 of 15 patients reached 20/25 and 1 patient 20/20. The data demonstrate the stability of the achieved refractive change after the adjustment and lock-in procedures. Postoperative refractive errors were successfully corrected with precision and significant improvement in UCVA and without compromising BSCVA using the light adjustable intraocular lens technology. Our data demonstrate the stability of the achieved refractive change after the adjustment and lock-in procedures. The light-adjustable lens is a promising technology with the potential to eliminate postoperative refractive surprises of up to 2 diopters of refractive and cylindrical error following cataract surgery.

Clinical Results With the Light Adjustable Intraocular Lens After Cataract Surgery

The accuracy of intraocular lens (IOL) calculation is limited by the variation of the measurement of corneal power, axial length, anterior chamber depth, and effective postoperative lens position. Therefore, IOL predictability is limited. The aim of this study was to evaluate the performance of the novel light adjustable lens (LAL, Calhoun Vision). Ten eyes with cataracts (seven patients) were included. After standard phacoemulsification, the LAL was implanted. Two to 3 weeks after surgery, all IOL adjustments had been completed. Preoperatively, pre-adjustment, pre-lock-in, and 1 month post-lock-in, a full ophthalmic examination including objective (autorefraction) and subjective refraction (ie, manifest uncorrected visual acuity [UCVA] and manifest best spectacle-corrected visual acuity [BSCVA]) and topography were performed. All cataract surgeries were performed with no complications. Two weeks after surgery, the mean refraction was +0.78+/-0.79 diopters (D). After adjustment and lock-in, the refraction was -0.07+/-0.21 D. In 4 of 10 eyes, second adjustments were necessary. One month after surgery, all patients were within +/-0.50 D of the intended refraction. Preoperatively, the cylinder was 0.88+/-0.77 D, but was reduced after adjustments to 0.15+/-0.20 D. Mean UCVA was 1.02, and all eyes gained at least two lines on the Snellen visual acuity test (ie, BSCVA) after surgery. The LAL is a new IOL with the ability to correct up to 2.00 D of sphere and cylinder after implantation. Our first clinical results are promising and indicate effective safety and stability.

Evaluation of the Calhoun Vision UV Light Adjustable Lens Implanted Following Cataract Removal

To evaluate the effectiveness of a silicone intraocular lens (IOL) that can be adjusted following implantation using ultraviolet (UV) irradiation. Prospective clinical trial of 40 patients (40 eyes) with visually significant cataract. Participants underwent small-incision phacoemulsification followed by implantation of a light-adjustable, silicone IOL (Light Adjustable Lens [LAL], Calhoun Vision). All patients were required to wear UV-protective eyewear at all times, until final lock-in. Pre- and postoperative clinical parameters included distance visual acuity and manifest refraction. At average 2 weeks postoperative (range: 10 to 21 days), patients were seen and refracted to determine type and magnitude of refractive error needing correction. All patients required an initial adjustment of the LAL, whereas 28 required a second UV treatment and none required a third adjustment. At 4 months postoperative, mean refraction was 0.04±0.37 diopters (D) (range: -0.88 to 0.50 D), mean sphere was 0.24±0.40 D (range: -0.50 to 0.75 D), and mean cylinder was 0.41±0.25 D (range: 1.00 to 0.0 D). Eighty-one percent of eyes gained 2 or more lines of corrected distance visual acuity. The adjustment and lock-in procedures were well tolerated by patients. The Calhoun Vision LAL is a promising technology with the potential to eliminate postoperative refractive surprises of up to 2.00 D of refractive and cylindrical error following implantation.

Klinische 6-Monats-Ergebnisse einer Licht-adjustierbaren Linse

The aim of this study was to evaluate the six-month clinical results of the light adjustable lens (LAL). In 20 eyes of 12 patients with cataract a cataract surgery with implantation of a light adjustable lens has been performed. 2 ¹/₂ weeks after surgery all intraocular lens adjustments were carried out. Preoperatively, immediately before the adjustment procedures and 1 month, 3 and 6 months after the adjustment procedure a complete ophthalmic examination was performed. All cataract surgeries have been carried out without any complications. 2 ¹/₂ weeks after surgery the mean spherical equivalent was + 0.39 D (standard deviation [SD] ± 0.79 D). 6 months after the adjustment procedure the spherical equivalent was -0.07 D (SD ± 0.25 D). 6 months after the adjustment procedure all patients were within ± 0.5 D of intended refraction. Two weeks after surgery the mean cylinder was -0.82 D (SD ± 0.67 D) and was reduced after the adjustments to -0.14 D (SD ± 0.30 D). The light adjustable lens is a new IOL with the ability to correct up to two dioptres of sphere and cylinder after implantation. Our clinical results are promising. Especially the astigmatic correction is very promising, but further clinical investigations with larger patient numbers and longer follow-up are necessary.

Advanced Intraocular Lens Designs

Intraocular lenses (IOLs) have evolved since their introduction and spherical monofocal designs are no longer the only pseudophakic option. IOLs with a toric surface are able to correct astigmatism, but are dependent on the accuracy of placement. Haptic design is very important with toric IOLs as different designs demonstrate different post-operative rotational stability. Multifocal IOLs produce multiple focal points within the eye and so provide the capacity for simultaneous distance and near vision. Various mechanisms for creating these focal points exist, which determine how light is distributed. Accommodating IOLs use the optic shift principle in order to restore the accommodative response. Single and dual optic variations exist; however, the restoration of accommodation has been limited and variable with the current generation of these IOLs. Aspherical IOLs are designed to improve the optical quality of the image created by the IOL. Aspherical correcting IOLs are dependent on their centration and tilt. New phacoemulsification technology allows cataract removal through a sub-2mm incision, and microincisional IOLs can be implanted through these incisions, which results in minimal surgical impact on the cornea. Blue- and violet-blocking IOLs have been introduced, which might help prevent the development of age-related macular degeneration. Light-adjustable lenses are a relatively new technology and allow non-invasive post-operative adjustment of the IOL’s refractive power. This is a fast-moving area of research and development due to the high demands of clinical practice.

Correction of Myopia after Cataract Surgery with a Light-Adjustable Lens

To determine whether residual myopia could be corrected postoperatively using the light-adjustable lens (LAL) technology in patients undergoing cataract surgery and LAL implantation. A prospective clinical study was conducted at Codet Vision Institute in Tijuana, Mexico. The LALs were implanted that would purposely result in myopic errors of up to -1.5 D (diopter). The LAL was treated with a spatial intensity profile delivered by a digital light delivery device to induce a targeted myopic refractive change. Once the desirable myopic correction was achieved, the LAL was treated again to lock-in the lens power. Fourteen eyes of 14 patients were studied. The manifest refraction, uncorrected visual acuity (UCVA), and best- or spectacle-corrected visual acuity (BCVA), were measured with follow up time of 1 to 9 months to determine the achieved refractive corrections and their stability. We measured UCVA and BCVA, achieved versus targeted refractive outcome, and refractive stability with follow up time of 1 to 9 months. Of 14 eyes, 13 eyes (92.9%) achieved 0.25 D of the target refraction at 1 day post lock-in with 100% of the eyes achieving the targeted refractive adjustment within 0.5 D or better with up to 9 months postoperative follow-up. All eyes treated show no change in manifest spherical refraction >0.25 D between 1 day post lock-in, and 3, 6, and 9 months postoperative visits. The data demonstrate the stability of the achieved refractive change after the adjustment and lock-in procedures. The mean rate of change was 0.006 D per month, which is 6 times more stable than that of laser corneal refractive procedures. Residual myopia errors up to -1.5 D were successfully corrected with precision and significant improvement in UCVA and without compromising BCVA using the LAL technology.

A numerical model of light adjustable lens

We model numerically the mechanical effects of UV induced photo-polymerization in elastomeric artificial lens. The elastomer is originated upon cross-linking of a silicone matrix. UV irradiation of one side of the lens polymerizes selectively a photosensitive macromer, causing local variations of its concentration. The subsequent diffusion of macromers from high concentration to low concentration zones modifies the shape of the lens and thus its dioptric power. In vitro experiments on artificial lens showed that the power change is dependent on UV exposure time, irradiation intensity and light pattern. With the aim to define a numerical tool able to predict the dioptric power adjustment as a function of the UV irradiation parameters, we setup a purely mechanic finite element model of the lens, adopting a hyperelastic material model embedded with eigen-deformations. Numerical simulations of axis-symmetric irradiation closely reproduced the experimental results, in terms of both lens geometry and dioptric power, for positive, negative and lock-in corrections.

Correction of Residual Hyperopia After Cataract Surgery Using the Light Adjustable Intraocular Lens Technology

To determine whether residual hyperopia could be corrected postoperatively using the light adjustable lens technology in patients undergoing cataract surgery and light adjustable lens implantation. Prospective, nonrandomized clinical trial. Fourteen eyes of 14 patients were studied. The manifest refraction, uncorrected visual acuity (UCVA), and best-corrected visual acuity (BCVA) were determined with follow-up time to determine the achieved refractive corrections and their stability. Of 14 eyes, 13 eyes (92.9%) achieved +/- 0.25 diopters (D) of the target refraction at one day post lock-in, with 100% of the eyes achieving the targeted refractive adjustment within 0.5 D or better up to six months postoperative follow-up. All eyes treated show no change in manifest spherical refraction >0.25 D between one day post lock-in, and three and six months postoperative visits. The data demonstrate the stability of the achieved refractive change after the adjustment and lock-in procedures. The mean rate of change was 0.006 D per month, which is six times more stable than that of refractive procedures. Residual hyperopia errors in the range of +0.25 to +2.0 D were successfully corrected with precision and significant improvement in UCVA and without compromising BCVA using the light adjustable intraocular lens technology.

Corneal endothelial safety with the irradiation system for light-adjustable intraocular lenses

To assess the safety to the corneal endothelium of the irradiation delivered through a system developed for noninvasive postoperative power adjustments of the Light Adjustable Lens (LAL) (Calhoun Vision). John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. After anesthesia, 12 cats had a light beam of near ultraviolet light (365 nm), with an intensity of 250 mW/cm(2), applied to the central 6.0 mm of the right cornea for 120 seconds. The cats were killed 1 day, 1 week, and 1 and 3 months after light application (3 cats/time point). Their corneas were then removed and evaluated for evidence of morphological damage to the corneal endothelial cells by staining with trypan blue and alizarin red and quantification with a digital imaging program (EPCO system). The overall size and shape of the corneal endothelial cells were qualitatively similar in irradiated and nonirradiated eyes. Four corneas in the irradiated group and 3 corneas in the control group had small areas of cell damage (staining with trypan blue) within the central 6.0 mm. These areas were generally close to corneal folds. The differences in damaged areas between both groups at each time point, as well as the difference considering the overall results in both groups, were not significant (P>.05). Irradiation of cat corneas with the therapeutic dose used to lock in the power of the LAL was not associated with damage to endothelial cells. Further studies are necessary to confirm the absence of damage at the ultrastructural level.

IOL Materials: Manufacturing and More

Purpose: To describe the evaluation of 2 new intraocular lenses (IOLs) manufactured with newly developed materials with special properties. Materials and Methods: Experimental studies with human eyes obtained postmortem, animal models (rabbit and cat), as well as in vitro studies were used to evaluate 2 new IOLs: the Light Adjustable Lens (LAL), and the photochromic lens. Results: The LAL can have its dioptric power adjusted postoperatively, upon light irradiation, in a non-invasive manner. The photochromic lens turns yellow upon exposure to ultraviolet light, otherwise, it remains colorless, eliminating eventual problems with decreased scotopic vision with yellow lenses. Conclusion: The newly developed materials described here have the potential to further influence IOL manufacture.