| Abstract |
INTRODUCTION
Presbyopia (aging of accommodation mechanism of the human eye) represents a common problem for people aged over 40-45 years. Many theories have been proposed during the past decades regarding explanation of the pathologic physiology of presbyopia development. The most popular theory of those, states that presbyopia is the result of a progressive reduction of lens ability to accommodate, that worsens with age, due to either lens hardening or degeneration of the ciliary body tissues.
Regardless of the responsible cause, presbyopia reduces the ability of near vision affecting everyday life of individuals.
American studies have reported that in 1998, over 113 millions of Americans were over 45 years old, underlining the effect of presbyopia condition.
A wide variety of procedures have been investigated by ophthalmologists to correct the refractive error. Cornea laser surgery with multifocal patterns or monovision approaches were developed including LASIK, PresbyLASIK,
photorefractive keratectomy (PRK), laser epithelial keratomileusis (LASEK), thin-flap femto-LASIK or sub-Bowman’s keratomileusis (SBK). Conductive keratoplasty (CK), clear lens extraction or cataract surgery using multifocal, pseudo-accommodative intraocular lenses (IOLs) or monovision monofocal IOLs are also some of the techniques that have been used for the treatment of presbyopia.
Cornea laser surgery and CK are minimal invasive methods, but they provoke irreversible changes at corneal anatomy, whereas scleral surgery and clear lens extraction are more invasive techniques.
The necessity to develop a minimal invasive, reversible, and safe surgical technique with an easy learning curve for patients between 45 and 60 years, who could be considered too old for presbyopia corneal laser surgery and too young for lens extraction, led to the development of refractive intracorneal lenses (inlays) (Flexivue™ Micro-Lens) placed underneath cornea inside a pocket in the corneal stroma. The inlays are refractive lenses that have a central zone free of refractive power and a peripheral zone with a standard positive refractive power. The inlays are inserted inside a pocket in the corneal stroma of the non dominant eye, offering two different focal points, one for the far vision and a different for the near vision respectively. The pocket of the cornea is created using a femtosecond laser.
The Flexivue™ Micro-Lens is a transparent, hydrophilic disc with 3 mm diameter and
approximately 15 μm edge thickness. The central 1.6 mm diameter of the disc is plano
and the peripheral zone has an add power. The base power available range from +1.5 D to +3.50 D in 0.25 D increments. At the center of the disc there is a hole of 0.15 mm diameter that permits the transfer of oxygen and nutrients of the cornea through the lens. The lens is implanted inside a pocket of the corneal stroma in the center of the visual axes of the non dominant eye.
The lens has a bifocal optical system which acts as a modified monovision (smart
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monovision). During far vision the rays pass through the central zone of the inlay without refractive effect and will be sharply focused on the retina, whereas the rays which pass through the refractive peripheral zone will be not of focus in front of the retina.
During near vision, the rays which pass through the central zone will be out of focus
behind the retina and the rays which pass through the lens peripheral refractive zone will be focused on the retina. As a result, only the peripheral zone of the lens provides the near vision correction, and affects far vision, whereas the central zone of the lens and the peripheral unaltered part of the cornea do not affect the far vision.
CLINICAL HYPOTHESIS
The working clinical hypothesis for this study is that implantation of the Flexivue™
Micro-Lens into a pocket created by femtosecond laser in the cornea, if correctly placed in the center of the cornea corresponding to the visual axes, will enable the study patients to obtain functional near vision without further correction while maintaining their distance.
PURPOSE OF THE STUDY
The purpose of this study is to evaluate the safety and efficacy of the Flexivue™ Micro- Lens for the treatment of presbyopia with enhanced medication regimen.
STUDY POPULATION
For the study, approximately 10 patients in each group will be enrolled at one location.
To qualify for enrollment in this study, each candidate will be thoroughly evaluated to
ensure that they meet all inclusion criteria and that they do not exhibit any of the
exclusion criteria specified in the study protocol.
METHODS
This prospective, interventional clinical study comprised 47 emmetropic, presbyopes with a mean age of 51.55 years± 4.11 (range 45 to 60 years). The inlay was implanted, centred on the line of sight, inside a corneal pocket created in the non-dominant eye of the patients, using a femtosecond laser. Follow-up time was 12 months. Visual acuity, topography, wavefront aberrometry, contrast sensitivity, structural corneal alterations and questionnaires were evaluated.
STUDY PARAMETERS
Efficacy Measures: Uncorrected near visual acuity.
Safety Measures: Best Corrected near visual acuity, Biomicroscopy
Satisfaction Measures: Patient satisfaction questionnaire
RESULTS
Twelve months after surgery, uncorrected near visual acuity (UNVA) was 20/32 or better in 75% of the operated eyes, whereas mean uncorrected distance visual acuity (UDVA) of the operated eyes was statistically significantly reduced (p&λτ0.001) and mean
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uncorrected distance visual acuity (UDVA) binocularly was not significantly altered (p=0.516).Seventeen patients lost one line of corrected distance visual acuity (CDVA) in the operated eye. Overall higher order aberrations were increased and contrast sensitivity was decreased in the operated eyes. No tissue alterations were found using corneal confocal microscopy. No intra or late-operative complications occurred.
CONCLUSIONS
Intracorneal refractive inlay for presbyopia FlexivueTM Micro-Lens using the femtosecond laser seems to represent an effective and safe method for the corneal compensation of presbyopia in emmetropic presbyopes aged between 45 and 60 years old, twelve months after the implantation.
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Μελέτη της ασφάλειας και αποτελεσματικότητας του ενδοκερατοειδικού διαθλαστικού ενθέματος "flexivue TM micro-lens (Presbia,CA Cooperatief U.A,Netherlands)" για τη διόρθωση της πρεσβυωπίας
