The Light-adjustable Lens to Correct Astigmatism After Cataract Surgery
Aim To determine if residual cylindrical refractive error after cataract surgery can be adjusted using the light-adjustable lens (LAL).
Methods The LAL is a photosensitive silicone intraocular lens whose power can be adjusted post-operatively using UV light at 365 nm. A digital light delivery device (DLD) is used to adjust LAL power in situ to correct residual refractive errors non-invasively. Profiles developed to correct residual cylindrical and spherical errors were tested on five patients, with postoperative toric refractive errors of 1.25–1.75 D. At 2 weeks post-implantation, best corrected visual acuity (BCVA), uncorrected visual acuity (UCVA) and residual refractive errors were measured.
Results Toric error was reduced in each of the patients and refractions remained stable for the 9 month follow-up period. Achieved spherical equivalent manifest refraction (MRSE) was within 0.25 D of targeted emmetropia. All five patients improved their UCVA to ≥20/25 (≤0.1 logarithm of the minimum angle of resolution (LogMAR)) and maintained their BCVA.
Conclusion The LAL can be adjusted postoperatively to correct residual astigmatism.
While use of partial coherence interferometry (IOL Master; Carl Zeiss-Meditec, Jena, Germany) has improved prediction of intraocular lens (IOL) power, residual astigmatism after cataract surgery remains a significant cause of reduced uncorrected visual acuity (UCVA). In a series of 7500 eyes undergoing cataract surgery, Hoffer showed that 1770 (23.6%) had≥1.5 D of corneal astigmatism. Residual astigmatism of as little as 0.75 D can reduce UCVA and cause haloes. Surgical methods to treat astigmatism include corneal and limbal relaxing incisions, toric IOLs (eg, Staar Toric IOL (Staar Surgical, Monrovia, California, USA) and AcrySof toric IOL (Alcon Laboratories, Fort Worth, Texas, USA)), and postoperative laser-assisted keratomileusis (LASIK) or photoreactive keratotomy (PRK) (bioptics). Relaxing incisions can correct low and moderate astigmatic errors, but can be complicated by placement on the incorrect axis, perforation, pain and infection. Toric IOLs are also subject to misalignment, postoperative rotation and limited number of powers. Finally, excimer laser surgery performed in the postoperative period requires a second procedure, often by a different surgeon, since many cataract surgeons do not perform refractive surgery.
An alternative approach to treating astigmatism postoperatively is the light-adjustable intraocular lens (LAL) (figure 1). The LAL contains photosensitive silicone macromers homogeneously dispersed within a silicone matrix that allows the refractive power of the lens to be adjusted postoperatively by the application of spatially profiled near-ultraviolet (UV) light (365 nm). Clinically, the refractive properties of the LAL are adjusted using the digital light delivery (DLD) device (figure 1). The DLD generates the required spatial irradiance pattern using a digital mirror device (DMD; Texas Instruments, Dallas, Texas, USA) and projects it onto the implanted LAL. The versatility of the DMD chip enables customisation of the irradiation profile to correct both sphere and astigmatism, as well as higher order aberrations.
(Enlarge Image)
Figure 1.
(A) The light-adjustable lens (LAL). It has a 6 mm bi-convex optic with modified C-polymethyl methacrylate (C-PMMA) haptics, a square posterior edge, rounded anterior edge, and a posterior UV blocking layer of≤100 μm thick. (B) The digital light delivery (DLD) device. It projects 365 nm UV light onto the LAL for both adjustment and lock-in. The spatial irradiance pattern for adjustment is generated using a digital mirror device that contains an array of approximately 785 000 mirrors.
For correction of astigmatism an irradiation pattern is generated and aligned with the astigmatic axis. We have previously reported on correction of astigmatism in vitro. The objective of this study was to test whether we could correct residual cylindrical refractive error postoperatively in patients undergoing cataract surgery with implantation of the LAL.
Abstract and Introduction
Abstract
Aim To determine if residual cylindrical refractive error after cataract surgery can be adjusted using the light-adjustable lens (LAL).
Methods The LAL is a photosensitive silicone intraocular lens whose power can be adjusted post-operatively using UV light at 365 nm. A digital light delivery device (DLD) is used to adjust LAL power in situ to correct residual refractive errors non-invasively. Profiles developed to correct residual cylindrical and spherical errors were tested on five patients, with postoperative toric refractive errors of 1.25–1.75 D. At 2 weeks post-implantation, best corrected visual acuity (BCVA), uncorrected visual acuity (UCVA) and residual refractive errors were measured.
Results Toric error was reduced in each of the patients and refractions remained stable for the 9 month follow-up period. Achieved spherical equivalent manifest refraction (MRSE) was within 0.25 D of targeted emmetropia. All five patients improved their UCVA to ≥20/25 (≤0.1 logarithm of the minimum angle of resolution (LogMAR)) and maintained their BCVA.
Conclusion The LAL can be adjusted postoperatively to correct residual astigmatism.
Introduction
While use of partial coherence interferometry (IOL Master; Carl Zeiss-Meditec, Jena, Germany) has improved prediction of intraocular lens (IOL) power, residual astigmatism after cataract surgery remains a significant cause of reduced uncorrected visual acuity (UCVA). In a series of 7500 eyes undergoing cataract surgery, Hoffer showed that 1770 (23.6%) had≥1.5 D of corneal astigmatism. Residual astigmatism of as little as 0.75 D can reduce UCVA and cause haloes. Surgical methods to treat astigmatism include corneal and limbal relaxing incisions, toric IOLs (eg, Staar Toric IOL (Staar Surgical, Monrovia, California, USA) and AcrySof toric IOL (Alcon Laboratories, Fort Worth, Texas, USA)), and postoperative laser-assisted keratomileusis (LASIK) or photoreactive keratotomy (PRK) (bioptics). Relaxing incisions can correct low and moderate astigmatic errors, but can be complicated by placement on the incorrect axis, perforation, pain and infection. Toric IOLs are also subject to misalignment, postoperative rotation and limited number of powers. Finally, excimer laser surgery performed in the postoperative period requires a second procedure, often by a different surgeon, since many cataract surgeons do not perform refractive surgery.
An alternative approach to treating astigmatism postoperatively is the light-adjustable intraocular lens (LAL) (figure 1). The LAL contains photosensitive silicone macromers homogeneously dispersed within a silicone matrix that allows the refractive power of the lens to be adjusted postoperatively by the application of spatially profiled near-ultraviolet (UV) light (365 nm). Clinically, the refractive properties of the LAL are adjusted using the digital light delivery (DLD) device (figure 1). The DLD generates the required spatial irradiance pattern using a digital mirror device (DMD; Texas Instruments, Dallas, Texas, USA) and projects it onto the implanted LAL. The versatility of the DMD chip enables customisation of the irradiation profile to correct both sphere and astigmatism, as well as higher order aberrations.
(Enlarge Image)
Figure 1.
(A) The light-adjustable lens (LAL). It has a 6 mm bi-convex optic with modified C-polymethyl methacrylate (C-PMMA) haptics, a square posterior edge, rounded anterior edge, and a posterior UV blocking layer of≤100 μm thick. (B) The digital light delivery (DLD) device. It projects 365 nm UV light onto the LAL for both adjustment and lock-in. The spatial irradiance pattern for adjustment is generated using a digital mirror device that contains an array of approximately 785 000 mirrors.
For correction of astigmatism an irradiation pattern is generated and aligned with the astigmatic axis. We have previously reported on correction of astigmatism in vitro. The objective of this study was to test whether we could correct residual cylindrical refractive error postoperatively in patients undergoing cataract surgery with implantation of the LAL.
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