Changes in Keratometric Values and Corneal High Order Aberrations After Hydrogel Inlay Implantation

BCLA CLEAR Presbyopia: Evaluation and diagnosis

It is important to be able to measure the range of clear focus in clinical practice to advise on presbyopia correction techniques and to optimise the correction power. Both subjective and objective techniques are necessary: subjective techniques (such as patient reported outcome questionnaires and defocus curves) assess the impact of presbyopia on a patient and how the combination of residual objective accommodation and their natural DoF work for them; objective techniques (such as autorefraction, corneal topography and lens imaging) allow the clinician to understand how well a technique is working optically and whether it is the right choice or how adjustments can be made to optimise performance. Techniques to assess visual performance and adverse effects must be carefully conducted to gain a reliable end-point, considering the target size, contrast and illumination. Objective techniques are generally more reliable, can help to explain unexpected subjective results and imaging can be a powerful communication tool with patients. A clear diagnosis, excluding factors such as binocular vision issues or digital eye strain that can also cause similar symptoms, is critical for the patient to understand and adapt to presbyopia. Some corrective options are more permanent, such as implanted inlays / intraocular lenses or laser refractive surgery, so the optics can be trialled with contact lenses in advance (including differences between the eyes) to better communicate with the patient how the optics will work for them so they can make an informed choice.

Clinical performance of presbyopia correction with a multifocal corneoscleral lens

AIM

To assess the clinical performance of a multifocal corneoscleral lens for the presbyopia correction.

METHODS

A prospective clinical trial of the Onefit™ A multifocal corneoscleral lens was conducted with 40 participants with presbyopia. At 4wk of continuous wear of the corneoscleral lens, changes in the distance, intermediate, and near visual acuity (VA) were evaluated. The safety of the corneoscleral lens, central corneal thickness (CCT), corneal endothelial cell count, binocular stereopsis, tear film break-up time (BUT), corneal staining, corneal edema, corneal neovascularization (NV), and conjunctival hyperemia were examined. In addition, a subjective questionnaire addressing satisfaction (rated from 1 to 5 points) and discomfort (rated from 1 to 5 points) was administered.

RESULTS

Forty participants were enrolled in this study. Six participants were excluded because of poor compliance with lens fitting (n=2) and loss to follow-up (n=4). The mean age of the participants was 53.0±4.9y. At 4wk of continuous wear of the corneoscleral lens, the best corrected far, intermediate, and near VA was 0.08±0.11, 0.10±0.12, and 0.10±0.12 logMAR, respectively. These results were significant improvements over the baseline uncorrected VA (far: P=0.004; intermediate: P=0.004; near: P=0.002). CCT, corneal endothelial cell count, binocular stereopsis, BUT, corneal staining, corneal edema, corneal NV, and conjunctival hyperemia were not significantly different between baseline and after corneoscleral lens use. The average satisfaction scores for fit sensation; corrected far, intermediate, and near VA; and ease of handling were 4.1, 3.4, 3.6, 3.5, and 3.4, respectively. The average discomfort scores for dryness, irritation, foreign body sensation, redness, fogging, and halo were 1.7, 1.8, 1.5, 1.7, 1.7, and 1.3, respectively.

CONCLUSION

Far, intermediate, and near VA are improved in presbyopic patients with the multifocal corneoscleral lens compared to uncorrected baseline VA, without adverse ocular effects. This evidence supports the safety and effectiveness of presbyopia correction with multifocal corneoscleral lenses.

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.

Corneal remodelling and topography following biological inlay implantation with combined crosslinking in a rabbit model

Implantation of biological corneal inlays, derived from small incision lenticule extraction, may be a feasible method for surgical management of refractive and corneal diseases. However, the refractive outcome is dependent on stromal remodelling of both the inlay and recipient stroma. This study aimed to investigate the refractive changes and tissue responses following implantation of 2.5-mm biological inlays with or without corneal collagen crosslinking (CXL) in a rabbit model. Prior to implantation, rotational rheometry demonstrated an almost two-fold increase in corneal stiffness after CXL. After implantation, haze gradually subsided in the CXL-treated inlays (p = 0.001), whereas the untreated inlays preserved their clarity (p = 0.75). In-vivo confocal microscopy revealed reduced keratocyte cell count at the interface of the CXL inlays at week 8. Following initial steepening, regression was observed in anterior mean curvature from week 1 to 12, being most prominent for the non-CXL subgroups (non-CXL: -12.3 ± 2.6D vs CXL: -2.3 ± 4.4D at 90 μm depth, p = 0.03; non-CXL: -12.4 ± 8.0D vs CXL: -5.0 ± 4.0D at 120 μm depth, p = 0.22). Immunohistochemical analysis revealed comparable tissue responses in CXL and untreated subgroups. Our findings suggest that CXL of biological inlays may reduce the time before refractive stabilization, but longer postoperative steroid treatment is necessary in order to reduce postoperative haze.

Presbyopia: Effectiveness of correction strategies

Presbyopia is a global problem affecting over a billion people worldwide. The prevalence of unmanaged presbyopia is as high as 50% of those over 50 years of age in developing world populations, due to a lack of awareness and accessibility to affordable treatment, and is even as high as 34% in developed countries. Definitions of presbyopia are inconsistent and varied, so we propose a redefinition that states "presbyopia occurs when the physiologically normal age-related reduction in the eye's focusing range reaches a point, when optimally corrected for distance vision, that the clarity of vision at near is insufficient to satisfy an individual's requirements". Strategies for correcting presbyopia include separate optical devices located in front of the visual system (reading glasses) or a change in the direction of gaze to view through optical zones of different optical powers (bifocal, trifocal or progressive addition spectacle lenses), monovision (with contact lenses, intraocular lenses, laser refractive surgery and corneal collagen shrinkage), simultaneous images (with contact lenses, intraocular lenses and corneal inlays), pinhole depth of focus expansion (with intraocular lenses, corneal inlays and pharmaceuticals), crystalline lens softening (with lasers or pharmaceuticals) or restored dynamics (with 'accommodating' intraocular lenses, scleral expansion techniques and ciliary muscle electrostimulation); these strategies may be applied differently to the two eyes to optimise the range of clear focus for an individual's task requirements and minimise adverse visual effects. However, none fully overcome presbyopia in all patients. While the restoration of natural accommodation or an equivalent remains elusive, guidance is given on presbyopic correction evaluation techniques.

Biological corneal inlay for presbyopia derived from small incision lenticule extraction (SMILE)

Corneal inlays are a relatively new treatment option for presbyopia. Using biological inlays, derived from lenticules extracted from small incision lenticule extraction, may offer advantages over commercialized synthetic inlays in the aspect of biocompatibility. We conducted a non-human primate study to evaluate the safety, predictability, efficacy and tissue response after autogeneic, decellularized xenogeneic and xenogeneic lenticule implantation. The lenticule implantation effectively resulted in central corneal steepening (simulated keratometric values increased by 1.8–2.3 diopters), central hyper-prolate changes (asphericity Q values changed by −0.26 to −0.36), corneal anterior surface elevation (7.7–9.3 μm) and reasonable effective zone (1.5–1.8 times of the lenticule physical diameter), with no differences among the three groups. Slit lamp microscopy, transmission electron microscopy, confocal microscopy, histology and immunohistochemistry analyses confirmed the biocompatibility of the autogeneic and decellularized lenticules, whereas one eye in the xenogeneic group developed corneal stromal rejection during the study period. Our results showed that lenticule implantation has the potential for the management of presbyopia, and provide the basis for future clinical studies. The decellularization process may increase the potential utilization of lenticules without changing the efficacy.

Comparison of a hydrogel corneal inlay and monovision laser in situ keratomileusis in presbyopic patients: focus on visual performance and optical quality

PURPOSE

To compare the visual performance and optical quality after Raindrop Near Vision Inlay implantation or monovision LASIK for the correction of presbyopia.

MATERIALS AND METHODS

In this retrospective case-series study, patients previously treated in the nondominant eye with monovision LASIK were compared with patients previously implanted with Raindrop Near Vision Inlay. The study enrolled 16 inlay and 15 monovision LASIK patients. Uncorrected near visual acuity, uncorrected distance visual acuity, binocular stereopsis, patient satisfaction, and patient task performance were assessed.

RESULTS

Postoperatively, the mean spherical equivalent was -0.66 D (0.78 SD) for the inlay group and -1.03 D (0.56 SD) for the monovision LASIK group. Monocularly, at uncorrected near distances, 60% of inlay patients and 47% of monovision LASIK patients achieved ≥20/20. Monocularly, at uncorrected far distances, 75% of inlay patients and 40% of monovision LASIK patients achieved ≥20/32 vision. Binocularly, at near distances, 79% of inlay patients and 53% of monovision LASIK patients obtained ≥20/20 vision. All patients achieved ≥20/20 binocularly for distance. On average, inlay patients obtained 98 seconds of arc and monovision LASIK patients obtained 286 seconds of arc for stereopsis. Most (79%) of the inlay patients and 66% of monovision LASIK patients were satisfied with their near vision, while 86% of inlay patients and 67% of monovision LASIK patients were satisfied with their distance vision.

CONCLUSION

Patients receiving corneal inlays demonstrated better near and distance visual acuities, binocular stereopsis, task performance, and satisfaction, when compared to patients treated with monovision LASIK.

Non-lens-based surgical techniques for presbyopia correction

INTRODUCTION

Presbyopia is the most prevalent refractive error. With a progressive aging population, its surgical correction is an important challenge for the ophthalmology community, as well as the millions of patients who suffer from it, and who are increasingly demanding alternatives to its correction with glasses or contact lenses.

MATERIAL AND METHODS

A review is presented with a synthesised discussion on the pathophysiological theories of presbyopia and an updated and analytical description of the non-lens involvement surgical techniques used to treat presbyopia.

RESULTS

Corneal procedures include various types of corneal implants and photo-ablative techniques that generate a multifocal cornea, or monovision. Scleral procedures exert a traction on supralenticular sclera that supposedly would improve the amplitude of accommodation.

CONCLUSIONS

None of the techniques are able to completely eliminate the need for near -vision glasses, but many of them manage to improve the refractive status of the patients. More studies with rigorous and standardised methods and longer follow-up are needed to evaluate the changes in the near vision of the patients, in order to corroborate the real and practical usefulness of many of these techniques.