Perspective of a Refractive Surgery Specialist
Matching the patient with the right technique is the main condition of success.
By Damien Gatinel, MD
The French population follows the global demographic trend of most developed countries—our population is aging. The median age in France is now close to 40, which means that almost half of our population is experiencing some level of presbyopia.
Monovision is one of the first options to consider for treatment of presbyopia. Provided the patient can adapt to it, monovision can lead to total or near total spectacle independence. A successful history of contact lens monovision in a refractive surgery candidate is encouraging; if such a history is absent, I propose a monovision contact lens trial prior to surgery.
The main drawback with monovision is that some patients cannot tolerate it. Particularly, complaints of poor distance vision by emmetropes and low hyperopes are common. It is likely that the culprit in these visual complaints is reduced stereopsis for distance vision. Stereopsis, by definition, requires the fusion of vision in the left and right eyes. Therefore, a reduction in stereopsis cannot be compensated for in one eye. Reduced contrast sensitivity can also hinder visual performance, but mild contrast sensitivity in the non-dominant eye can be tolerated and compensated for with binocular vision.
For nearly 4 years, I have been offering the Kamra corneal inlay (AcuFocus; Figure 1) to my presbyopic patients. The small-aperture inlay improves near and intermediate vision without reducing binocular distance vision1 or stereopsis.2
A corneal inlay can be used in conjunction with laser refractive surgery for distance vision in presbyopic ametropes to provide extended depth of focus and excellent near UCVA in the implanted eye. With that said, matching a patient with the right surgical technique is the main condition for success with refractive procedures. There are broad indications for inlay-related techniques, but respecting contraindications and setting reasonable patient expectations are keys to success.
The Kamra inlay can be implanted using a dual-interface (ie, thin-flap LASIK with inlay insertion into a pocket under the LASIK interface) or with a pocket implantation technique. Depending on the technique chosen, visual recovery can vary. In one study, the mean postoperative near visual acuity across thousands of patients was J2.1 The immediate postoperative impact on distance vision is mild in most cases, and sometimes it is unnoticeable with binocular vision.
Distance vision can initially be affected in patients with dry eye disease, causing patients to lose 1 or 2 lines of BCVA while symptoms persist. Treating the dry eye disease immediately can help patients to reach their full visual potential.
Advantage No. 1: Reversibility. Unlike IOL surgery, implanting a corneal inlay is an extraocular technique. Additionally, the inlay can be removed at any time if necessary. In my experience, when patients consider a choice between a reversible procedure and the permanent removal of their natural lens, their comfort level is greater with the former.
Advantage No. 2: Easy recentration. Proper centration can be challenging for the surgeon performing his or her first implantation cases, but recentration is possible when necessary.
Advantage No. 3: Robust correction. Compared with presbyopic LASIK—another extraocular refractive surgical technique for presbyopia correction—the Kamra inlay technique is less complex and more robust to ocular particularities. The inlay’s mechanism of action is the pinhole effect, and success requires only achieving a slight myopic refraction and proper centration.
The Kamra corneal inlay is not a monovision strategy, and the depth of focus that it achieves is sufficient to compensate for any stage of presbyopia. Some surgeons are skeptical about the eye’s tolerance to inlays implanted into the cornea; however, the Kamra inlay is thin (5 μm) and has multiple perforations, including one large central perforation, that account for its long-term tolerance in the cornea.
With the aging of the population, effective presbyopic treatments have the potential to help boost a practice’s patient base. Presbyopic patients tend to gather and socialize with others their own age, making them excellent ambassadors for your practice. My corneal inlay patients have been pleased with their postoperative outcomes, and I feel that this technology has a secure place in my practice.
Damien Gatinel, MD, is an Assistant Professor and Head of the Anterior Segment and Refractive Surgery Department at the Rothschild Ophthalmology Foundation, Paris. Dr. Gatinel is a member of the CRST Europe Editorial Board. He states that he is a consultant to AcuFocus. He may be reached at tel: +33 1 48 03 64 82; e-mail: firstname.lastname@example.org.
Perspective of a Corneal Surgeon
Be selective of the treatments you offer to emmetropic presbyopes.
By William Power, MD
I propose a corneal inlay in patients from their late 40s up to the age of 60 years who desire correction of presbyopia. For me, the ideal patient is one who has been using reading glasses for several years and in whom hyperopia has now manifested for distance. With bilateral laser vision correction and an inlay placed in the nondominant eye, patients should achieve improvements in near and distance vision. Approximately 75% to 80% of my inlay patients fit the description above, and more than 90% who undergo this combination procedure can read N6 or better without glasses after the inlay is implanted.
The other 20% to 25% of my inlay patients are emmetropic presbyopes. I am more selective in these patients, as they are used to perfect unaided distance vision. In the early postoperative period, distance vision drops by 2 to 3 lines in the implanted eye. By 1 year postoperative, however, distance vision in the implanted eye should improve in most cases to 1 or 2 lines below baseline. I explain to patients that this is the compromise for being able to read and do near and intermediate tasks without glasses.
Emmetropic presbyopes should be assessed carefully to determine whether they can tolerate blur in the nondominant eye. If there is any doubt about their ability to compromise, a corneal inlay is probably not the best procedure.
I test patients’ flexibility by first refracting them until I get their correct manifest distance visual acuity in the phoropter; I tell them this is considered 100%. I then add a 1.00 D prescription lens in their nondominant eye and, while I closely watch their immediate response, I ask them to rate their vision relative to 100%. If the patient tells me it is about 90% to 95%, I know he or she is a good candidate. Anything less than 90% indicates that the patient has difficulty suppressing blur, and I am wary of moving forward with inlay implantation. I complete this evaluation with all of my patients, but it is particularly important with emmetropic presbyopes who are accustomed to good unaided distance vision.
In patients closer to 60 years of age and older, I carefully evaluate their crystalline lens. With any sign of early nuclear sclerosis or cortical lens opacity, I generally recommend a lens-based procedure.
Along with proper patient selection, setting appropriate patient expectations is also key. I tell patients that only 90% of my inlay patients are completely spectacle free—not 100%. In my experience, the majority of patients who need glasses after inlay implantation require them for reading small print in low light or when they are tired.
When counseling a patient about corneal inlays, I always mention the following points.
Point No. 1: There is no guarantee of 100% independence from reading glasses. More than 90% of my patients have what I call reading on the go. That is: they can use computers, their cell phones, and other electronic devices and read small print in good light.
Point No. 2: Do not compare inlay implantation to laser vision correction. Patients should not compare a corneal inlay to uncomplicated laser vision correction, as the latter produces excellent distance vision within 24 hours and the former requires an adaptation period of about 4 weeks.
Point No. 3: Distance vision in the inlay eye may suffer. When patients compare their distance vision in each eye, the inlay eye will perform less well than the noninlay eye. That is normal, and it improves around 6 months postoperatively. At 1 year, there will still be a difference in distance vision between the eyes, but it should not be as noticeable.
Physicians and patients must be aware that there is a compromise in distance vision with corneal inlays; with that said, this modality is the least compromising option for presbyopia correction that I have found. Multifocal IOLs can be fantastic, but associated night symptoms can be a disaster and lens extraction at a young age adds unnecessary risk. The inlay has been shown to cause no reduction in stereopsis, which can be a significant issue with monovision.3
For the first few months following inlay placement, contrast sensitivity can be reduced; however, studies show that, by 6 months, it returns to normal levels.4 Monovision also causes a greater decrease in distance visual acuity than an inlay.5
Inlay implantation is a refractive procedure, and it requires the creation of a pocket or a flap in the cornea. Making some form of entry into the corneal stroma increases the risk of infection. In my experience, the risk for infection after inlay implantation is no greater than it is after LASIK. There is also the possibility of epithelial ingrowth; however, the incidence is extremely low, particularly with the level of control we have over flap and pocket depth and setting with modern femtosecond lasers.
While not technically a complication, if the corneal bed under the flap is not smooth, patients can experience slower visual recovery. However, there has been a global movement among surgeons implanting inlays to shift toward implantation into a pocket rather than under a thick flap. To date, some laser manufacturers have released pocket software specifically designed to support inlay implantation, and others are actively working toward adding this feature to their lasers. There is also research into the timing of dual-interface procedures to see if these enhance postoperative recovery.
To date, I have implanted more than 150 inlays. No patient has developed a wound-healing response or had other complications. Two have reported that they were not happy. One patient never achieved good near or distance vision despite inlay repositioning. The inlay was removed, and the patient has returned to her pre-inlay vision. The other was an emmetropic presbyope who was not happy with distance vision despite having excellent near vision and requested removal of the inlay. He also returned to his preoperative vision. Overall, I find the procedure to be the best option for presbyopic patients in the previously mentioned age group.
William Power, MD, is a Consultant Ophthalmologist at the Royal Victoria Eye and Ear Hospital, St. Vincent’s University Hospital and the Blackrock Clinic in Dublin, Ireland. Dr. Power states that he has no financial interest in the products or companies mentioned. He may be reached at e-mail: email@example.com.
- Grabner G. Corneal inlays for presbyopia. Paper presented at: the ASCRS annual meeting; April 19-23, 2013; San Francisco.
- Linn S, Hoopes PC. Stereopsis in patients implanted with a small aperture corneal inlay. Paper presented at: Association for Research in Vision and Ophthalmology Annual Meeting; May 5-9, 2013; Seattle.
- Fawcett SL. Stereoacuity and foveal fusion in adults with long-standing surgical monovision. J Pediatr Ophthalmol Strabismus. 2001;5:342-347.
- Back A. Factors influencing success and failure in monovision. Int Contact Lens Clin. 1995;22:165-172.
- Durrie DS. The effect of different monovision contact lens powers on the visual function of emmetropic presbyopic patients: An American ophthalmological society thesis. Trans Am Ophthalmol Soc. 2006;104:366-401.