Correction of hyperopia with intracorneal implants

Confocal and Histological Features After Poly(Ethylene Glycol) Diacrylate Corneal Inlay Implantation

Purpose

To evaluate the in vivo biocompatibility of photopolymerized poly(ethylene glycol) diacrylate (PEGDA) intrastromal inlays in rabbit corneas.

Methods

Sixty-three eyes of 42 New Zealand rabbits were included. Manual intrastromal pockets were dissected in 42 eyes. PEGDA inlays were obtained using a specifically designed photomask and were inserted in the intrastromal pocket of 21 eyes (inlay group); the remaining 21 right eyes did not receive any implant (pocket-only group). Twenty-one eyes with no intervention were used as controls. In vivo confocal microscopy (IVCM) was performed at every visit. After 2 months, rabbits were sacrificed and corneas removed for histological analysis.

Results

Corneas remained clear in all but two animals, and five cases of corneal neovascularization were seen (P = 0.2). Inlays remained stable without evidence of lateral or anterior migration, and no other complications were observed. No changes in anterior and posterior keratocyte density (P = 0.3 and P = 0.1, respectively) or endothelial cell density (P = 0.23) were observed between groups during the study time by IVCM. On pathology samples, thinning of the epithelium over the inlay area and epithelial hyperplasia over the edges were observed. A polygonal empty space with no evidence of PEGDA hydrogel within the midstroma was seen in the inlay group. Keratocytes were normal in shape and number in the vicinity of the PEGDA implant area.

Conclusions

Photopolymerized PEGDA intrastromal inlays have shown relatively good safety and stability in rabbit corneas. Inlays were biostable in the corneal environment and remained transparent during follow up.

Translational Relevance

The investigated PEGDA is promising for the development of biocompatible intrastromal implants.

Permavision intracorneal inlay after sixteen years. Regression of initial refractive hyperopia

According to the available scientific literature, 77 patients underwent Permavision inlay worldwide, between 2004 and 2007. This study reported about the use of Permavision intracorneal inlay to increase the central corneal curvature and to correct hyperopia. A 32-year-old male patient went to the Tecnolaser Clinic Vision ® facilities for a refractive study. Preoperative refraction without cycloplegia was +6.00 D in the right eye (RE) and +4.00 in the left eye (LE). The surgery was performed for both eyes on December 2, 2003. The Carriazo-Barraquer mechanical microkeratome (Moria) was used to create a 180 μm-thick corneal flap with a diameter of 8.5 mm. After lifting the flap, the corneal inlay was placed centrally above the pupil and the flap was re-positioned. In this case report, the patient reverted to the initial refractive situation. The first refractive regression appeared at twelve-month follow-up. After sixteen years, it was found a decrease in maximum corneal curvature, an increase in mean corneal densitometry percentage, and no important changes in the central corneal thickness. In the reported case, the cornea reverted to its original shape. In the scientific literature, this is the first case report of a non-explanted Permavision inlay after sixteen years.

Small Incision Femtosecond Laser-assisted X-ray-irradiated Corneal Intrastromal Xenotransplantation in Rhesus Monkeys: A Preliminary Study

BACKGROUND

Gamma-ray irradiation could significantly induce widespread apoptosis in corneas and reduced the allogenicity of donor cornea. And the X-rays may have similar biological effects. The feasibility and effects of X-ray-irradiated corneal lamellae have not been assessed yet.

METHODS

Different doses (10 gray unit (Gy), 20 Gy, 50 Gy, 100 Gy) of X-ray irradiated corneal lamellae were collected from SMILE surgery. These corneal lamellae were assessed by physical characterization, hematoxylin and eosin (H-E) staining, Masson's staining, TdT-mediated dUTP nick end labeling (TUNEL), cell viability assay and transmission electron microscopy (TEM). We selected the optimum dose (100Gy) to treat the corneal lamellae to be the grafts. The human grafts and fresh allogeneic monkey corneal lamellae were implanted into rhesus monkeys via the small incision femtosecond laser-assisted surgery, respectively. Clinical examinations and the immunostaining were performed after surgery.

RESULTS

There were no significant changes in the transparency of the corneal lamellae, but the absorbency of the corneal lamellae was increased. According to the H-E and Masson's staining results, irradiation had little impact on the corneal collagen. The TUNEL assay and cell viability assay results showed that 100Gy X-ray irradiation resulted in complete apoptosis in the corneal lamellae, which was also confirmed by TEM observations. In the following animal model study, no immune reactions or severe inflammatory responses occurred, and the host corneas maintained transparency for 24 weeks of observation. And the expression of CD4 and CD8 were negative in the all host corneas.

CONCLUSION

X-ray irradiated corneal lamellae could serve as a potential material for xenogeneic inlay, and the small incision femtosecond laser-assisted implantation has the potential to become a new corneal transplantation surgical approach.

Flap Melting Over Corneal Inlay for Hyperopic Correction

PURPOSE

To report two cases of flap melting over corneal inlays for hyperopic correction several years after implantation.

METHODS

The corneal inlay (+6.00 diopters [D]; PermaVision intracorneal lens; Anamed Inc., Lake Forest, CA) was implanted underneath a LASIK flap in two patients.

RESULTS

Visual acuity and slit-lamp findings of both patients were stable for several years. At 9 years postoperatively, the first patient presented with a sudden loss of corrected distance visual acuity (CDVA) due to partial flap melting over the inlay while the surrounding anterior cornea showed opacification. The inlay was explanted immediately. Three years after explantation, CDVA returned to 1.0. Similarly, the second patient presented 11 years postoperatively with loss of vision, opacification, and partial flap melting. The inlay was explanted. Two years later, CDVA recovered.

CONCLUSIONS

Potentially severe biocompatibility issues of corneal inlays may occur even after several uneventful years. [J Refract Surg. 2018;34(11):775-778.].

Unilateral Keratectasia Treated with Femtosecond Fashioned Intrastromal Corneal Inlay

Purpose:

In this case report, we describe the surgical procedure of corneal inlay preparation and corneal pocket creation using a femtosecond laser system.

Case Report:

A 7-year-old girl who presented with unilateral paracentral corneal thinning underwent the surgical procedure of corneal inlay. Preoperatively, the refraction was +10.00-6.00 × 170. One month after the procedure, astigmatism and hyperopia were decreased and the refraction was +5.00-1.25 × 110.

Conclusion:

Femtosecond laser–assisted pocket creation for the implantation of corneal inlays offers accuracy of pocket parameters, enhancing predictability, resulting in better final outcomes, and improving the safety of the procedure.

Histological and confocal changes in rabbit cornea produced by an intrastromal inlay made of hexafocon A

PURPOSE

The aim of this study was to evaluate biocompatibility of a newly proposed intrastromal inlay in rabbit corneas.

METHODS

Eighteen eyes of 9 New Zealand rabbits were included in this prospective study. An intrastromal pocket was created in both eyes using Melles instruments. Annular intracorneal inlays made of hexafocon A were implanted randomly into the stromal pocket of one eye of each rabbit. Confocal microscopy was performed at each visit during 6-month follow-up. After 6 months, the rabbits were killed and corneal tissues of both eyes were sent for light microscopic studies.

RESULTS

Mild stromal edema was present during the first few days and disappeared afterward with mild haze around the tunnel site in all cases. Deposits around the lamellar channel developed in 3 implanted eyes and in none of the pocket-only eyes. No neovascularization or epithelial downgrowth was present at the incision site in any case. All inlays remained centered and optically clear. In confocal imaging, we observed no significant difference in keratocyte cell density and inflammatory cells between the control pocket-only group and inlay group. In pathological evaluation, there was no difference in the average epithelial thickness between both groups. Descemet membrane and endothelium appeared normal in both groups.

CONCLUSIONS

This study revealed safety and biocompatibility of hexafocon A as an intracorneal inlay in rabbits.

The effect of inlay implantation on corneal thickness and radius of curvature in rabbit eyes

PURPOSE

To study the effect of inlay implantation on corneal shape, assessing the changes using optical coherence tomography (OCT) and a customized image analysis software.

METHODS

Thirteen rabbit eyes were operated on, with positive-powered corneal inlays implanted into 11 eyes and 2 eyes serving as flap-only controls. Cross-sectional OCT images were obtained using Optovue preoperatively, and 1 hour, 1 week, and 1 month postoperatively. Topography maps were obtained preoperatively using Medmont E300. Image analysis software was built to extract corneal thickness and radius of curvature. Anterior corneal radius of curvature values obtained from the OCT images were compared with the corneal topography maps to assess the validity of the method.

RESULTS

Corneal thickness increased more than predicted immediately after the implantation. However, by 1 month, it matched closer to the added thickness of the corneal inlays. An overall pattern of epithelial thinning was observed of up to 25% at 1 month. The anterior corneal surface had steepened up to 15% at 1 month, whereas inconsistent changes for the posterior corneal surface were observed.

CONCLUSIONS

After corneal inlay implantation, an immediate response was observed in the cornea. Corneal swelling because of surgical trauma was the most likely cause for the observed thickening of the cornea up to 1 week. By 1 month, the epithelial layer measured thinner for most eyes. Most of the added thickness was transferred to the central anterior corneal surface, causing steepening at 1 month. The anterior corneal radius of curvature values obtained from OCT images were in broad agreement with Medmont topography.

Long-term follow-up of hydrogel intracorneal lenses in 2 aphakic eyes

We report the outcome of hydrogel intracorneal lens implantation in 2 patients. The lenses were implanted at approximately 50% depth in the cornea to correct high hyperopic refractive errors of 10.5 diopters (D) and 14.0 D, respectively. Both patients were contact lens intolerant and not suitable for intraocular lens implantation. Surgery was performed in 1988, and the patients were followed until early 2010. The patients showed good tolerance for the intracorneal lenses, but both developed opacities around the implant, leading to reduced visual acuity in 1 patient. Long-term patient monitoring is essential since corneal opacities can develop after many years. Removing the implant is not necessary as the lens can easily be rinsed by lifting the corneal cap.

Hydrogel intracorneal inlays for the correction of hyperopia: outcomes and complications after 5 years of follow-up

PURPOSE

To evaluate safety and efficacy of an intracorneal inlay for the correction of hyperopia.

DESIGN

A prospective, nonrandomized, noncomparative, 2-center study.

PARTICIPANTS

Thirty-four hyperopic eyes were implanted with a hydrogel intracorneal inlay (Permavision, Anamed, Lake Forest, CA). Preoperative hyperopia was +3.9 diopter (D; range, +2 to +7). Uncorrected visual acuity (UCVA) was the logarithm of the minimum angle of resolution (logMAR; the decimal logarithm of decimal visual acuity with a minus sign) 0.6 +/- logMAR 1, and best-corrected visual acuity (BCVA) was logMAR 0.1 +/- 0.7.

METHODS

Corneal flaps were created with a mechanical microkeratome (M2 [Moria, Anthony, France] or Amadeus [Advanced Medical Optics Inc, Santa Ana, CA]; 180 microm), followed by inlay implantation onto the stromal bed over the pupillary center and covered by the corneal flap. Follow-up was 5 years.

MAIN OUTCOME MEASURES

We measured UCVA and BCVA; patients underwent, slit-lamp examination, pachymetry, and confocal microscopy. The follow-up was up to 6 years.

RESULTS

The UCVA improved during 3 months and was stable for up to 2 years. There was a loss of > or =2 lines of spectacle-corrected visual acuity in 35% of eyes at 2 years, and a loss of > or =2 lines in 55.5% of the eyes at 5 years. Refractive predictability was poor, with 60% of the eyes having +/-3.00 D of emmetropia. A decentration of the inlay occurred in 29.4%, progressive perilenticular deposits were observed in 88.2%, haze was seen in 73.5%, and the inlay was explanted in 58.8%, with a cumulative survival rate of 58.4%.

CONCLUSIONS

An intracorneal inlay may be an option to treat hyperopia, but the tested inlay caused significant visual loss and scarring and had to be explanted in the majority of cases.

Synthetic corneal inlays

This review is based on the activities of the Vision Cooperative Research Centre (previously Cooperative Research Centre for Eye Research and Technology) Corneal Implant team from 1991 to 2007. The development of a synthetic polymer of perfluoropolyether (PFPE), meeting essential physical and biological requirements, for use as a corneal inlay is presented. Each inlay was placed in a corneal flap created with a microkeratome and monitored over a two-year period in a rabbit model. The results indicate that the PFPE implant shows excellent biocompatibility and biostability. As a result, a Phase 1 clinical trial is being conducted. Three years post-implantation, the PFPE inlays are exhibiting continued excellent biocompatibility. Corneal inlays made from PFPE are biocompatible with corneal tissue in the long term and offer a safe and biologically-acceptable alternative to other forms of refractive surgery.

Design and fabrication of an artificial cornea based on a photolithographically patterned hydrogel construct

We describe the design and fabrication of an artificial cornea based on a photolithographically patterned hydrogel construct, and demonstrate the adhesion of corneal epithelial and fibroblast cells to its central and peripheral components, respectively. The design consists of a central "core" optical component and a peripheral tissue-integrable "skirt." The core is composed of a poly(ethylene glycol)/poly(acrylic acid) (PEG/PAA) double-network with high strength, high water content, and collagen type I tethered to its surface. Interpenetrating the periphery of the core is a microperforated, but resilient poly(hydroxyethyl acrylate) (PHEA) hydrogel skirt that is also surface-modified with collagen type I. The well-defined microperforations in the peripheral component were created by photolithography using a mask with radially arranged chrome discs. Surface modification of both the core and skirt elements was accomplished through the use of a photoreactive, heterobifunctional crosslinker. Primary corneal epithelial cells were cultured onto modified and unmodified PEG/PAA hydrogels to evaluate whether the central optic material could support epithelialization. Primary corneal fibroblasts were seeded onto the PHEA hydrogels to evaluate whether the peripheral skirt material could support the adhesion of corneal stromal cells. Cell growth in both cases was shown to be contingent on the covalent tethering of collagen. Successful demonstration of cell growth on the two engineered components was followed by fabrication of core-skirt constructs in which the central optic and peripheral skirt were synthesized in sequence and joined by an interpenetrating diffusion zone.

Removal of an Intracorneal Hydrogel Implant for Hyperopia After LASIK

PURPOSE

To report a case of intracorneal hydrogel lens implantation for hyperopia after repeat LASIK surgery.

METHODS

A 34-year-old man underwent intracorneal lens implantation following two LASIK procedures for correction of hyperopia.

RESULTS

The decentered intracorneal lens was removed due to ocular pain and inflammation, epithelial ingrowth under the corneal flap, and high order aberrations. Pain and inflammation resolved, and corneal stability was regained > 6 months after removal of the lens.

CONCLUSIONS

Intracorneal lenses may require explantation if previous laser ablative procedures fail to correct refractive errors.

Correction of hyperopia by intracorneal lenses: two-year follow-up

PURPOSE

To assess the safety and efficacy of intracorneal lenses as a surgical alternative for the correction of hyperopia.

SETTING

Al-Azhar University and El Magrabi Eye Hospital, Cairo, Egypt.

METHODS

Twenty-three eyes of 21 patients who had a mean hyperopia of 4.3 diopters (D) +/- 0.71 (SD) (range +2.5 to +6.0 D) received Permavision lenses (Anamed Inc.), which are made of a highly permeable hydrogel with a water content of 78% and a refractive index close to that of corneal tissue (1.376). The Moria M2 microkeratome was used to make a 160 microm corneal flap with a diameter of +/-8.5 mm. The intracorneal lens was placed beneath the flap after minimal interface irrigation.

RESULTS

Clinical examination showed mild corneal edema and a myopic shift during the first week postoperatively. In 17 eyes (73.9%), the postoperative uncorrected visual acuity was similar to the preoperative best corrected visual acuity (BCVA); 1 eye (4.3%) lost 1 line of preoperative BCVA. In 5 eyes (21.7%), various degrees of lens opacification with some degree of corneal haze were seen after uneventful follow-up. Decentration of 0.5 to 1.0 mm was seen in 2 eyes (8.6%), 1 of which had the lens explanted because of significant opacification. Induced astigmatism was evident in 1 eye (-1.5 D). A total of 16 eyes (69.6%) were within +/-0.5 D of target, and 20 eyes (86.9%) were within +/-1.0 D (87%). No flap melting or extrusion of the lens was recorded in 24 months of follow-up. Night halos and glare were reported in 3 eyes; all had a lens diameter of 5.0 mm.

CONCLUSIONS

Intracorneal hydrogel lenses were tolerated relatively well by stromal tissue, providing a reasonably stable and predictable way to correct moderate hyperopia. However, induced astigmatism, stromal opacification, decentration, and night halos and glare occurred in a significant number of eyes. To ensure safety, deep flap cuts are preferred and these eyes should be watched carefully to avoid decentration of the lens in the early postoperative period.

Surgical Correction of Hyperopia

Surgical attempts to correct hyperopia have yielded varying results over the last 130 years. These techniques include the reshaping of the cornea through incisions, burns, or lamellar cuts with removal of peripheral tissue; the addition of central inlays; laser ablations; and the replacement of the crystalline lens. By examining the success of each surgical technique, the refractive surgeon may be able to make an informed decision on its indications and limitations, based on the specific patient's characteristics. Reporting the outcomes and complications of hyperopic surgery will help refine our approach to the management of an increasingly hyperopic and presbyopic population.

Confocal assessment of the corneal response to intracorneal lens insertion and laser in situ keratomileusis with flap creation using IntraLase

PURPOSE

To assess the response of the cornea to hydrogel intracorneal lens (ICL) insertion or laser in situ keratomileusis (LASIK) with IntraLase (IntraLase Corp.) at the cellular level.

SETTING

Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.

METHODS

Twenty patients (29 eyes) were evaluated by in vivo confocal microscopy 1 to 6 months postoperatively: 20 eyes had LASIK with flap creation by IntraLase, and 9 eyes had ICL insertion (8 following IntraLase).

RESULTS

For LASIK with IntraLase, keratocyte activation and/or interface haze was detected in 8 of 20 eyes. The remaining eyes had interface particles but no cell activation. Keratocyte activation was generally limited to a few cell layers adjacent to the interface. However, 2 patients exhibited multiple layers of activation and increased extracellular matrix (ECM) reflectivity (haze) surrounding the interface by confocal microscopy. Both patients also had clinical haze and photophobia. For ICLs, following insertion, 5 of 9 eyes had activated keratocytes adjacent to the implant surfaces. The largest amount of cell activation and ECM haze detected by confocal microscopy was in 2 patients with significant clinical haze. Structures with an epithelioid morphology were detected on some implant surfaces. Epithelial thickness was 33.3 microm +/- 2.3 (SD) in the ICL eyes and 49.2 +/- 6.5 microm in the LASIK with IntraLase eyes.

CONCLUSIONS

Both LASIK with IntraLase and ICL insertion following IntraLase induced keratocyte activation, which may underlie clinical observations of haze in some patients. Intracorneal lens implant also induced thinning of the overlying corneal epithelium.

Photoablative inlay laser in situ keratomileusis (PAI-LASIK) in the rabbit model

PURPOSE

To evaluate the suitability, biocompatibility, and efficacy of a proprietary hydrogel photoablative inlay (PAI) for use during laser in situ keratomileusis (LASIK).

SETTING

Laboratory study, Tulane University Health Sciences Center, New Orleans, Louisiana, USA.

METHODS

Eight rabbits (1 eye each) underwent the PAI-LASIK procedure; 4 eyes had a disk-shaped inlay and 4, a donut-shaped inlay. Preoperatively, the hydrogel material was ablated with a programmed correction of 5.0 diopters of hyperopia or myopia.

RESULTS

The eyes were followed for 1 to 16 months. No eye showed signs of rejection or extrusion of the PAI. There was no significant difference in corneal clarity or the healing rate between eyes with donut-shaped PAIs and those with disk-shaped PAIs. One eye with a donut-shaped PAI had minimal corneal haze. The remaining inlays did not opacify or fracture during ablation.

CONCLUSION

The hydrogel material can be used for the proposed PAI-LASIK procedure.

PermaVision intracorneal lens for the correction of hyperopia

PURPOSE

To evaluate the safety, predictability, and efficacy of sutureless synthetic keratophakia (SSK) with PermaVision intracorneal lens (Anamed) implantation.

SETTING

Ophthalmic Hospital, Rome, Italy.

METHODS

This retrospective study analyzed the refractive outcomes in 10 eyes of 6 patients who had SSK with PermaVision lens implantation for spherical hyperopia (cylinder less than 1.0 diopter [D]). Preoperatively, the mean spherical equivalent (SE) refraction was +4.33 D +/- 1.52 (SD) (range +3.00 to +6.37 D). All procedures were performed using the Hansatome microkeratome (Bausch & Lomb) with a superior hinge except in 1 eye in which the flap was cut using the Amadeus microkeratome (Allergan) with a nasal hinge.

RESULTS

Six months after PermaVision lens insertion, the mean SE refraction was +0.03 +/- 0.36 D (range -0.50 to +0.38 D), the mean uncorrected visual acuity was 0.85 +/- 0.13 (range 0.63 to 1.00), and the mean best corrected visual acuity was 0.99 +/- 0.19 (range 0.63 to 1.25). No eye lost lines of visual acuity. In 1 eye, the lens was acutely decentered and had to be explanted.

CONCLUSIONS

Sutureless synthetic keratophakia with the PermaVision intracorneal lens is a new technique for the correction of hyperopia. It is easy to perform as well as reversible, and the learning curve of the experienced laser in situ keratomileusis surgeon is short. The technique was safe and effective for spherical hyperopia, but longer follow-up and additional cases are needed to draw conclusions about the efficacy of the technique.

Confocal Microscopy of Corneas With an Intracorneal Lens for Hyperopia

PURPOSE

We evaluated short-term results and confocal microscopic corneal changes following intracorneal lens implantation.

METHODS

In six eyes of three patients with hyperopia between +3.00 and +6.00 diopters (D), an intrastromal hydrogel lens (Permavision, Anamed, Anaheim, Calif) was implanted. Mean baseline hyperopia was +3.90 D. Manifest refraction, uncorrected visual acuity, and spectacle-corrected visual acuity were evaluated. We also performed confocal real-time microscopy with a water immersion objective. Corneal optical sections were recorded and reviewed frame by frame. Examinations were done at months 3, 6, and 12 after intracorneal lens implantation.

RESULTS

After surgery, the spherical equivalent refraction was within +/- 0.50 D in 83% (five of six eyes) at 3 months and 100% (six eyes) at 6 and 12 months. Uncorrected visual acuity (UCVA) at 3 months was within 20/40 or better in 67% (four eyes) and in 100% (six eyes) at 6 and 12 months; no eyes had 20/20 or better UCVA at 3 and 6 months. One eye (17%) had 20/20 or better UCVA at 12 months. On confocal microscopy, one eye had an amorphous deposit adjacent to the lens and presumed fibroblastic activity in the same stromal area at 6 months, which was non-progressive up to 12 months.

CONCLUSION

Intracorneal lenses may be a treatment option for correction of spherical hyperopia. Predictability must be improved but results in these six eyes were stable up to 1 year. Confocal miscroscopy confirmed biocompatibility and showed no abnormal changes, except two spots of hypercellularity in one eye.