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Abstract Scleral expansion surgery; Corneal laser surgery with multifocal patterns or monovision approaches; Conductive keratoplasty (CK); and Clear lens extraction or cataract surgery using multifocal, accommodating, or monovision monofocal IOLs are among the techniques that have been used for the treatment of presbyopia. Although Corneal laser surgery and CK are minimally invasive methods, they provoke irreversible changes in corneal anatomy, whereas scleral surgery and clear lens extraction are even more invasive techniques. Presbyopic patients with emmetropia who are between the ages of 45 and 60 years are a particular target group for corneal inlays because they have healthy eyes, usually with excellent distance visual acuity. Many surgeons consider these individuals too old for corneal laser surgery and too young for cataract surgery. Furthermore, these patients are dissatisfied with procedures that leave even minimal damage to their far binocular visual acuity and quality of vision. The corneal inlay being removable, allows the patient to take advantage of future technologies for correcting presbyopia or cataract if needed. If the patient doesn’t like them, they can be easily removed and no further procedure is required to restore them back to their original refractive status. The inlays may enhance near vision, with only a marginal loss of distance acuity depending on the inlay utilised. Because it is a monocular procedure, quality distance vision in the other eye is always maintained, and the patients seem to appreciate that . The inlays were tested and found that there was only a very slight reduction in the mean deviation visual field of 2dB after five years’ follow-up – a time frame that seems quite reasonable to postulate that they are very safe . Page | 95 Another potential problem is that not all patients adapt quickly to their post-inlay vision. For instance, a LASIK procedure followed by Kamra implantation in the nondominant eye of a myopic patient could be performed but after several days the patient may still not be very comfortable with it. However, patients are urged to give it time because there is a process of neuro-adaptation with the inlay. It is a little bit like the IntraCor procedure in this respect – some patients have immediate results after the surgery, but sometimes it takes a few weeks for other patients to adapt to their new vision . Centration is another potential issue with inlays, and some concerns have also been raised about longterm biocompatibility. An electronic alignment system such as that recently introduced for the Kamra inlay, effectively deals with the centration issue and will become the norm for optimal placement of these types of implant. There can be some mild interface reaction that occurs between the implant and the cornea. Some earlier generation hydrogel inlays have been seen 20 years after implantation and they look good with no visually significant scarring. But after removal of the inlay the site where the implant was placed can be seen. That occurs with the Kamra inlay as well, although it does not cause visually significant light scatter or other symptoms. The use of the latest-generation femtosecond laser technology helps to reduce variations in wound healing. Creating the femtosecond pocket or flap atraumatically using the latest laser models resulted in faster visual rehabilitation. The key is to use modern equipment for a smooth ablation and then there is less variability in the wound healing. Page | 96 For optimal outcomes with the Presbylens/Vue+ inlay, it is advised to deliver the inlay in the centre of the pupil, and keep the flap hydrated to avoid microstriae. The importance of aggressive management of dry eye pre- and postoperatively has also been highlighted, as this population tends to have drier eyes. Implantation of corneal inlays is differentiated from simple monovision procedures with laser correction or cataract surgery not just in the procedure’s reversibility but also in its dependence on pupil size. The maximal inlay effect occurs during near vision when the pupil becomes smaller, and it decreases during far vision when the pupil is larger. The phenomenon of “smart monovision” is a unique mechanism of action of the Flexivue Micro-Lens; other inlays have different mechanisms of action, including increasing depth of focus (AcuFocus), and reshaping of corneal curvature (PresbyLens). Even the best technology has its downsides and corneal inlays are no exception. The main disadvantage is that the inlay is a reasonable but not a perfect solution for presbyopia, as only one eye is corrected. With this approach, binocularity is disturbed, at least at near, and patients become independent but not completely free of glasses for near vision. In most doctor’s view, the best candidates for inlays are emmetropic presbyopes with a clear lens, 20/20 uncorrected distance vision and a near add of about+2.00 D. Inlays may also be unsuitable for patients with very high expectations. As with all bifocal or multifocal corrections, retinal image contrast may be reduced in eyes implanted with the Flexivue and Vue+ devices and retinal illuminance may be markedly reduced with the Kamra implant. Page | 97 Corneal inlay technology moved in the direction of hydrogels more than 20 years ago, but problems with corneal biocompatibility and surgical difficulty caused earlier efforts to be unsuccessful. Corneal reaction to the ReVision Optics Vue+ inlay is either absent or mild. About 10% of patients develop a light haze over the inlay about 6 months after implantation. In some cases, this effect gradually disappears by itself, but in others a second round of steroids quickly clears the cornea, and the haze rarely returns. Emmetropic presbyopes are certainly candidates but the largest number of patients who seem to ask for the surgery are presbyopes who are also myopic or hyperopic and may also have astigmatism. Understandably they don’t want to trade far glasses for near glasses. For these patients, the best solution is usually what is called SIM-LASIK (LASIK first to correct their ametropia and then the inlay to deal with their presbyopia). While the demand for presbyopic treatments worldwide is on the increase, patients today are much better informed about the options open to them. There has been a definite shift in the age profile of the typical refractive surgery patient in recent years, from around 35 years about a decade ago to around 45 or 50 years-of-age today. There is no steep learning curve for the surgeon and the surgery can be performed without changing or adding new equipment or software in a modern refractive surgery theatre equipped with a femtosecond laser . Page | 98 To summarize the features & benefits of corneal inlays include Improved Vision (Sharp and clear near vision, Minor or no distance visual acuity change & Quick visual recovery typically within a few days ), Safety (Reversible, safely remove lens for surgeon and patient, Flexibility to remove lens if prescription upgrade is needed or new technology appears, No permanent loss of tissue, Biocompatible with the cornea & Allows for corneal metabolism) as well as Satisfaction(Improves lifestyle, ending the need for reading glasses for daily activities & Cosmetically appealing, lens is invisible to the eye) . Table 4: Summary of corneal inlays for presbyopia |