Presbyopia: Corneal Implants- Latest Research
We were able to locate multiple papers concerned with presbyopia. Much of the research presented here deal with the success and failures of corneal inlay implantation. But some articles are reviews on techniques and practices for addressing presbyopia. This report contains a summary of 20 articles.
We began our investigation with numerous scientific and medical databases looking for published material on the subject of presbyopia. Our inquiry returned numerous results. We have presented a summary of 20 entries in this report.
Presbyopia: Corneal Implants – Latest Research
Safety and Efficacy of an Intrastromal TransForm ™ Corneal Allograft (TCA) for Presbyopia Correction
The study’s objective is to evaluate the safety and effectiveness of intrastromal implantation of the Allotex TransForm corneal allograft (TCA) for improving presbyopic subjects’ near vision. The Allotex TCA is a laser-shaped piece of acellular cornea, sterilized with electron beam radiation. The TCA is placed just beneath Bowman’s layer in an intrastromal flap created by femtosecond laser application.
Correction of Presbyopia: An Integrated Update for the Practical Surgeon
This article is a collection of articles concerning various techniques of presbyopia correction. These methods of correction include optical tools (e.g., spectacles and contact lenses), topical medications, and surgical procedures. The article also includes the authors’ personal experience and their perspective on the future of presbyopia correction techniques.
Refractive Corneal Inlay for Presbyopia in Emmetropic Patients in Asia: 6-Month Clinical Outcomes.
This research is an evaluation of the six-month clinical outcomes of Flexivue Microlens refractive corneal inlay in Asian Emmetropic patients for the surgical compensation of presbyopia. Measures of evaluation include near/intermediate/distant visual acuities, refraction, keratometry, defocus curve, wavefront aberrations, contrast sensitivity, Scheimpflug corneal scanning, endothelial cell density, dry eye test, confocal microscopy scanning, and patient questionnaires. Of the 21 eyes that received inlay implantation, the uncorrected near visual acuity of the operated eyes increased significantly from 0.55 ± 0.22 logMAR preoperatively to 0.25 ± 0.15 logMAR (p<0.05). However, mean bilateral uncorrected distant vision did not change significantly (p=0.90).
Mediators of Corneal Haze Following implantation of Presbyopic Corneal Inlays
This study’s purpose is to identify protein mediators of corneal haze following presbyopic corneal inlay surgery. Tear samples were collected and subjected to quantitative proteomic analysis using iTRAQ. Inlay-associated haze occurred in 35% of eyes. These data represent a starting point for understanding the pathways involved in corneal haze following synthetic inlay implantation.
Long-term Changes in Keratometry and Refraction After Small Aperture Corneal Inlay implantation
This study’s purpose is to assess longitudinal refractive, keratometric, and topographic changes post-KAMRA small-aperture inlay implantation. Uncorrected near visual acuity (UNVA), uncorrected distance visual acuity, manifest refractive spherical equivalent (MRSE), mean keratometry (Km), corneal topography, and surgically induced astigmatism vector analyses were performed on 50 patients preoperatively and at regular intervals postoperatively. An average shift of 0.15 ± 0.63 D (range -1.63 to 2.00 D) occurred between the preoperative baseline and 36 months. The authors conclude that KAMRA inlay may cause an increase in Km compared with baseline measures.
Initial Results With Allograft Corneal Inlays
This is an initial study of sterile allograft corneal inlay, TransForm Allogenic Refractive Lenticules (Allotex) in 10 presbyopic emmetropic patients. Mean preoperative UNVA was 0.67 ± 0.19 logMAR. Mean UNVA had significantly improved by 5 ± 1.88 lines in postoperative follow-up compared to the preoperative examination. A total of five eyes remained unchanged from the preoperative examination, four eyes lost one line, one eye lost two lines, and no eye lost more than two lines of best corrected visual acuity (BCVA).
Corneal Remodeling and Topography Following Biological Inlay implantation with Combined Crosslinking in a Rabbit Model
The purpose of this study is to investigate the refractive changes and tissue responses after implantation of 2.5-mm biological inlays with or without corneal collagen crosslinking (CXL) in a rabbit model. Rotational rheometry demonstrated a nearly two-fold increase in corneal stiffness after CXL pre-implantation. Post-implantation, the CXL-treated inlays saw a gradual reduction in haze (p=0.001), while the untreated inlays preserved their clarity (p=0.75).
This article examines the etiology of presbyopia. The author notes that the condition does not occur suddenly; instead, it is a slow decline. According to the author, there are approximately 100 million emmetropic individuals in the United States. There are multiple approaches to alleviate the symptoms of presbyopia; the author highlights the need for individualized treatment to meet the patient's unique circumstances.
The author asserts that 11% of the world experiences presbyopia, and that figure is expected to double by 2050. However, there are many surgical options for presbyopia. Pseudoaccomodation procedures include presbyLASIK; monovision; corneal inlays; and depth of focus IOLs (multifocal, trifocal, and extended). True dynamic accommodation restorative type procedures include accommodating IOLs, presbydrops, femtosecond lens softening, and scleral procedures.
Adaptation to Brightness Perception in Patients Implanted with a Small Aperture
This study examines the relative perceived brightness in the two eyes of patients implanted monocularly with a small-aperture KAMRA corneal inlay. The authors used a binocular adaptive optics vision simulator to determine the relative perceived brightness. Equalizing transmittance (ET) was found to be greater than expected. The authors conclude that patients’ enhanced brightness perception could probably be attributable to a neural adaptation process.
Imaging the Cornea, Anterior Chamber, and Lens in Corneal and Refractive Surgery
This book chapter is concerned with the use of anterior segment OCT (AS-OCT) in corneal, cataract, and refractive surgery. The authors note that AS-OCT shows great potential for cases involving corneal edema and postoperative control after Descemet’s membrane endothelial keratoplasty (DMEK). The AS-OCT also has potential for application in postoperative posterior chamber Collamer lenses’ vault follow-up and measuring the anterior chamber angle.
Corneal Inlays for Presbyopia Explanted Due to Corneal Haze
This case series involved three patients that required explantation of KAMRA inlays due to postoperative corneal haze. The authors report that all patients had promising results post-implantation. Symptoms developed three to six years after the initial procedure. Patients’ reported improved visual symptoms six months after explantation.
Retrospective Comparison of Visual Outcomes After KAMRA Corneal Inlay Implantation with Simultaneous PRK or LASIK
Simultaneously, 79 patients underwent LASIK/inlay, and 47 patients underwent PRK/inlay. Researchers then measured safety, efficacy, predictability, and stability with primary emphasis on monocular UNVA during follow-up examinations. The authors report that 92% of the LASIK/inlay group and 95% of the PRK/inlay group had a UNVA of 20/40 at the end of the follow-ups (i.e., six months). The authors conclude that Simultaneous PRK/inlay and LASIK/inlay have similar outcomes to emmetropic eyes.
Refractory Interface Haze Developing After Epithelial Ingrowth Following Laser in Situ Keratomileusis and Small Aperture Corneal Inlay Implantation
This study reports the occurrence and management of refractory interface haze after epithelial ingrowth post-implantation of small aperture inlay. The study’s subject underwent combined hyperopic laser in situ keratomileusis and KAMRA corneal inlay implantation to correct presbyopia (sub-clinical anterior basement membrane dystrophy [ABMD]). Epithelial ingrowth developed post-implantation, which required debridement and KAMRA removal. The authors conclude that early surgical intervention is key to haze resolution in these cases.
The More Likely Etiology Behind Suboptimal Results from Corneal Inlays
The authors respond to another article by Ong et al. concerning the explantation of a KAMRA corneal inlay. This article's authors suggest that the underlying cause of failure is the implantation depth of 175 to 180 μm. The authors point to recent studies that suggest ideal KAMRA inlay placement depth is 250 to 350 μm3. They suggest that they can explain the hyperopic shift, haze, and accompanying visual disturbances as a result of the shallower implantation depth.
Evaluation of the Small-Aperture Intracorneal Inlay: Three-Year Results from the Cohort of the U.S. Food and Drug Administration Clinical Trial
The study is of 507 patients with emmetropic presbyopia, aged 40 to 60 years old, and spread across the globe (i.e., North America, Europe, Asia, and Australia). The implanted eyes exhibited 3.5 diopters of defocus range above 20/40. At 36 months, 87.1% of patients had 20/40 or better monocular UNVA, and 93.8% had 20/40 or better binocular UNVA. Implantations performed using a femtosecond laser pocket procedure resulted in improved near vision in monocular and binocular UNVA (90.3% and 94.5%, respectively). The authors conclude that small-aperture corneal inlay was found to be a safe and effective way to improve monocular and binocular near vision.
The authors assert that presbyopia is a global problem affecting billions and is prevalent in as much as 50% of the developing world’s population aged 50 years and over. The condition is even as high as 34% in the developed countries. The authors propose a redefinition of presbyopia due to inconsistencies in definitions of the condition. The authors present and evaluate some strategies for correcting presbyopia as presently defined.
Small Aperture Optics for the Presbyope: Do Comparable Designs of Corneal Inlays and Intraocular Lenses Provide Similar Transmittances to the Retina?
Through ray tracing, the authors seek to show that different stop designs and positions may produce similar axial imagery. The authors further assert that increases in depth of focus, off-axis, and vignetting effects result in different field dependences for the pupil transmittance. The paper discusses the implications of these effects along with the implantation of a stop in one eye.
This piece concerns the construction and composition of a corneal implant. The author discusses the background of presbyopia. The author also covers the implantation procedure in detail.
Persistent Corneal Fibrosis After Explantation of a Small-Aperture Corneal Inlay
The study concerns a case of corneal fibrosis after the implantation of a small-aperture KAMRA corneal inlay. The subject reported vision loss in the left eye six years after implantation. Persistent decreased visual acuity and fibrosis were observed eight months after explantation of the inlay. The authors conclude that long-term monitoring is important to detect late adverse events post-implantation.
We were able to locate 20 articles concerning presbyopia. Many of these articles are studies on corneal implantation, and some study the factors that lead to explantation. Additionally, some articles are reviews of the current literature, strategies, and techniques for correcting presbyopia.