OD reports practice’s success with corneal inlay
15 June 2017
The keys to success with the Raindrop Near Vision Inlay are patient selection and evaluation of ocular surface, centration and inflammation, he said.
The use of corneal inlays for the surgical correction of presbyopia is an exciting new technology for optometry, ophthalmology and, especially, for the presbyopic patient.
The Raindrop Near Vision Inlay (ReVision Optics, Lake Forest, Calif.) – and similar technology – is changing our clinical approach, resulting in a paradigm shift from the decades of monovision contacts or monovision laser correction for presbyopic patients.
All corneal inlays for presbyopia treatment have some distinct advantages over contacts and monovision laser correction. These inlays maintain good distance vision while providing intermediate and near vision, often with virtually no visual compromise.
The corneal inlays have no refractive “shelf life” for the accommodative functional loss associated with the aging process. For most patients, it will be “set it and forget it” until the patient reaches cataract age. Another advantage provided by the inlay is that it is removable without compromising the cornea structure. They can be removed with relative ease, with minimal to no loss of best corrected visual acuity.
In June 2016, the Raindrop Near Vision Inlay because the second corneal inlay to receive FDA approval. The Kamra Inlay (AcuFocus, Irvine, Calif.), which utilizes a pinhole principle to increase depth of focus, was approved in 2015.
The Raindrop, like the Kamra, has no refractive power, but increases depth of focus by producing a hyperprolate central cornea. It is made of a permeable hydrogel material, which has been shown to provide good oxygenation and glucose delivery to the cornea, thus providing good homeostasis and biocompatibility.
The Raindrop inlay is transparent and has an index of refraction closely matching the human cornea. It has a 2.0 mm lenticule width, is 32 microns thick centrally and tapers to 10 microns peripherally.
All corneal inlays are placed in the nondominant eye with the aid of a femtosecond laser creating either an intrastromal pocket or corneal flap. The surgical approach is dictated by the manufacturer’s recommendations. The placement depth of each corneal inlay is based upon the mechanism of action and optical principles and is different for the Kamra and the Raindrop.
The Raindrop inlay is placed on the stromal bed, under the femtosecond laser-created corneal flap, which is 8.0 mm in diameter and 30% of the central cornea depth. This anterior placement of the Raindrop induces a surface corneal change resulting in a multifocal cornea. The inlay changes the cornea through space occupation, producing anterior stromal bowing and epithelial remodeling.
Pupil constriction that occurs during accommodative effort combined with the steeper central cornea creates a pseudo-accommodation effect resulting in improved near vision.
The clinical indications for the Raindrop Inlay are: presbyopic patients between the ages of 41 and 65 years old with a manifest refraction spherical equivalent of +1.00 D to -0.50 D with less than -0.75 D of refractive cylinder. The patient should be using about a +1.50 D add. Patients should have at least 500 microns of central corneal thickness, which allows the recommended minimum 150-micron flap to be created.
It is important for the patient’s ocular surface to be healthy. A dry corneal surface will compromise the visual results. The Raindrop inlay is contraindicated in patients with severe dry eye, autoimmune disease and abnormal corneal topography and is not recommended for prior LASIK or PRK patients. If ocular surface issues are present, such as preexisting dry eye requiring lid therapy, this should be addressed, discussed and treated. If the patient responds to treatment, surgery can be considered.
Clinically, for patients to better understand what the Raindrop inlay vision may be like, the use of a trial multifocal soft contact lens in the nondominant eye can optically simulate the inlay. Assuming the patient undergoes neuro-adaptation and has visual tolerance, surgery can be further discussed. The PureVision (Bausch + Lomb) with plano power and a high add is an excellent choice for this. A positive contact lens trial is a good indication that the patient will be satisfied.
At day 1 post-op, the Raindrop patient’s uncorrected distance vision acuity will be compromised. Thus, the patient will not experience the “wow” factor that is often seen with LASIK. Our results show an average of 20/100 at day 1. However, most patients will experience the wow factor when their excellent near vision is demonstrated. At near, it is not uncommon for a patient to read 20/25 at 8 inches day 1. This over-response at near point is normal, and the effect at near will lessen over the next few weeks. As the near focal distance increases, a concomitant improvement of uncorrected distance vision occurs.
Postoperatively, the corneal inlay can be evaluated with the use of corneal topography. Clinicians will observe the dramatic surgical corneal effect of the inlay. The Kmax measurements change dramatically from the preoperative Kmax value. The hyperprolate cornea is created by the Raindrop inlay.
The Raindrop inlay centration is crucial for optimal results and needs to be evaluated at the slit lamp by retro-illumination postoperatively. This evaluation can be accomplished by having the patient cover the dominant eye and look straight at the slit lamp light beam, then rotating the slit lamp beam to the side and retro-illuminating the inlay to assess centration in relationship to the center of the pupil.
Early in the postoperative period the Raindrop inlay can be difficult to see due to its transparency, so retro-illumination is key. The most common area of decentration is inferior and nasal. If this is observed, the patient should return to surgery for inlay repositioning. Symptoms of inlay decentration include poor vision at near and monocular diplopia. It is important to avoid Alphagan (brimonidine, Allergan) usage postoperatively because this antiglaucoma medication has been shown to have caused flap slippage and inlay decentration.
At 1 month, the postop distance visual acuity continues to improve to an average of 20/25, uncorrected, in our first 17 cases. The near point visual acuity continues to extend and at 1 month is optimized at 16 inches. Corneal topography is used at 1 month to further evaluate inlay centration, and Kmax is used as a reference point for refractive effect. On slit lamp exam, it is normal for the Raindrop inlay to be clear with a faint white circle around the peripheral edge.
Postop medications include a standard topical fluoroquinolone four times a day for 1 week. Additionally, a strong tropical steroid such as Durezol (difluprednate 0.05%, Alcon) is used and tapered over a 1-month period. Clinically, avoid all topical drops that contain BAK, including artificial tears, because this preservative can cause an inflammatory response to the inlay and corneal epithelial toxicity.
ReVision Optics recommends a mild topical steroid such as Lotemax (loteprednol etabonate 0.5%, Valeant) for the second and third month. In our practice, we recommend the use of a mild steroid once a day for 6 months for long-term inflammatory control. Inflammation is an issue with all corneal inlays, and the off-label use of mitomycin-C in the future may prove to be another pharmacological tool in controlling postop inlay inflammation.
At 6 months and beyond, most patients experience a stable refraction, and uninterrupted functional range of vision at distance, intermediate and near should be observed. The inlay should be well centered and clear. However, late postop inflammation can occur, typically after 6 months. Clinically, haze will be seen on the peripheral edges of the inlay, which is an indication of a corneal inflammatory response.
Characteristics of Raindrop inlay inflammation include an increase in blur or loss of distance vision, but a decrease in focal point at near, an improvement of near vision or a myopic shift. Educate your patients to return to the clinic if they notice a blur at distance and a shift at near. The quicker the inflammatory response is detected the better the treatment.
The Pentacam (Oculus), with cornea densitometry software, can help detect an early inlay inflammatory response even before it is seen on the slit lamp exam. Additionally, evidence of inflammation maybe apparent on topography, with an increase in postoperative Kmax.
The recommended treatment for an inflammatory response is Durezol with a tapered dosage: four times daily for 1 week, three times daily for 1 week, twice daily for 1 week, once daily for 1 week and 2 additional months of Lotemax twice daily for 1 month, then once daily for 1 month. If inlay inflammation is recurrent and not resolving, explantation is recommended. According to Jeffery J. Machat, MD, speaking at the Caribbean Eye meeting, Cancun, Mexico, in February, since the Raindrop launch and commercialization in the U.S. there have been no published reports of post-market explantation.
However, the current labeled explantation rate for the Raindrop inlay is 3.7% using current surgical guidelines. This is a significant improvement over previous explantation rates of up to 10% first reported with earlier techniques. Removability without visual compromise is one of the advantages of corneal inlays for patients and surgeons.
In conclusion, our overall clinical results and patient satisfaction with the Raindrop Near Vision Inlay have been positive. The four most important clinical pearls for optometric inlay comanagement are patient selection, ocular surface management, inlay centration evaluation, and inflammation detection and control.