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Complex Cases Using Corneal Inlays

Jessica Heckman, OD and Y. Ralph Chu, MD

Corneal inlay technology has expanded the realm of surgical near vision correction. New technology comes with new challenges in both the pre- and postoperative care of patients considering these technologies. This chapter will utilize case examples to detail management techniques for surgical selection and planning as well as postoperative management, including inlay implantation in patients with previous refractive surgery, combination laser vision correction with inlay implantation, implantation post–cataract surgery, managing corneal haze, and inlay removal.

INLAY IMPLANTATION IN A REFRACTIVE SURGERY PATIENT

A patient with previous refractive surgery can be considered for an off-label use of corneal inlay technology. Special consideration must be made to locate a previous LASIK flap. Which inlay and implantation technique depends on the age and depth of the old LASIK flap. A KAMRA inlay (CorneaGen) is often the preferred inlay for a cornea with previous LASIK as it is effective and preferred to be implanted deeper in the cornea than the Raindrop inlay (ReVision Optics). The recommended pocket depth for a KAMRA inlay in post-LASIK patients is 200 μm to 250 μm with a minimum of 80 μm below the flap interface,¹ while still maintaining a safe distance above the corneal endothelium of at least 200 μm. Conversely, if a flap is thick and the surgeon feels comfortable lifting, a Raindrop inlay could also be implanted for this patient population. Raindrop inlays have been implanted under flaps as thin as 130 μm.^2,3 However, flap thickness of up to 34% has been shown to have less incidence of haze compared to more superficial flaps.⁴

Case 1: KAMRA Inlay Implantation in a Previous LASIK Patient

A 54-year-old female had myopic LASIK in July 2005 and was looking to decrease her dependence on reading glasses. Her uncorrected distance visual acuity (UDVA) was 20/20 OD, OS, and OU. The manifest refraction in her right eye was 0.00 +0.25 x 107, OS -0.25 +0.25 x 058. Her uncorrected near visual acuity (UNVA) was J6 (Jaeger) OD, OS, and OU. The patient had normal ocular health on slit lamp and fundus examination. The previous LASIK flap was measured on anterior segment optical coherence tomography (OCT) to be 141 μm thick, with a total corneal thickness of 495 μm. (Figure 7-1 shows the OCT image.) The patient had significant improvement in vision with a pinhole occluder over her nondominant left eye and elected to proceed with KAMRA implantation.

The KAMRA inlay was implanted in a femtosecond pocket successfully underneath the LASIK flap at a depth of 250 μm in the patient’s left eye. At this depth, the LASIK flap interface was estimated to be 109 μm above the pocket with 245-μm residual corneal bed. One week status post KAMRA inlay implantation, the surgical eye had a UDVA of 20/25- and J1 near vision with manifest refraction of -1.00 sph. Figure 7-2 shows a picture of KAMRA inlay at 1 week following surgical implantation.

This case example provides a couple of key clinical pearls for the clinician. OCT works very well to locate and accurately measure a previous LASIK flap. In addition, OCT measures total corneal thickness, which is necessary to plan an inlay procedure that is at the recommended distance below the LASIK flap, as well as an appropriate depth for the inlay technology with enough residual tissue bed left in the cornea. The process for achieving optimal vision for a corneal inlay is slower than LASIK. Healing time for corneal inlay technology can often be one of the most important things to emphasize in a previous LASIK patient. The patient’s previous point of reference for ocular surgery healing was much quicker with LASIK, than what will likely be experienced with an inlay.

As an off-label use of corneal inlays, both the KAMRA and Raindrop inlays can be implanted concurrently or consecutively with laser vision correction in patients with either hyperopic or myopic preoperative refractions.2,3,5,6 The ability to combine surgical technology allows the surgeon to optimize a patient’s refraction for inlay implantation to ultimately result in the best outcomes. A mildly myopic refraction of -0.75 diopters (D) remains the widely accepted ideal refraction for a KAMRA inlay.⁷ Conversely, plano to +0.5 D is the generally preferred preoperative refraction for Raindrop implantation.⁸

As was discussed previously, the KAMRA inlay is placed in a femtosecond pocket that is a minimum of 80 μm below the patient’s LASIK interface whether done on the same or different days.¹ Photorefractive keratectomy is also able to be combined with a KAMRA inlay in combination or consecutively. Although photorefractive keratectomy has a longer healing course than LASIK, it eliminates the risk of LASIK flap complications and the risk of flap interface disruption and minimizes postoperative dryness.

Raindrop inlays are often done in combination with LASIK surgery as well. The LASIK flap needs to be adjusted in the inlay eye to the increased thickness required for Raindrop inlay implantation, up to 34% of corneal thickness.⁴ When using inlays off-label in combination with laser vision correction, the clinician must also take care to implant the inlay at recommended depth above the corneal endothelium.

Case 2: Combination Laser Vision Correction With KAMRA

A 52-year-old male presented to our clinic seeking less dependence on reading glasses. His UDVA was 20/20 in each eye with manifest and cycloplegic refraction of +0.50 +0.25 x 063 in his right eye and +0.50 +0.25 x 050 in his left eye. The patient’s UNVA was J10 in his right eye and J8 in his left. Anterior and posterior segment health were normal on examination. The patient had normal topography and his central corneal thickness was 513 μm in his right eye and 517 μm in his left. Figure 7-3 shows the patient’s Pentacam (Oculus) map prior to refractive surgery. The patient’s dominant eye was his left eye. A pinhole occluder was used to simulate vision with a KAMRA inlay. The patient noticed significant improvement in vision at both distance and near vision with the pinhole occluder in combination with a +1.25 loose lens over his right eye. The patient elected to proceed with KAMRA inlay with advanced surface ablation prior to the procedure to target for a -0.75 manifest refraction to optimize patient result.

The patient underwent uncomplicated advanced surface ablation in his right eye to result in the specified myopic target to optimize inlay outcome. The patient then proceeded with a KAMRA inlay 2 months later. The patient’s Pentacam following advanced surface ablation is shown in Figure 7-4. The KAMRA inlay was implanted in a femtosecond pocket at a depth of 250 μm. The next day the patient returned with UDVA OD 20/30, OU 20/20 and UNVA OD J1, OU J1. At 1 week postoperatively, the patient’s UDVA improved to 20/20 in his right eye and his UNVA improved to J1+ with a manifest refraction of -0.75 +0.25 x 137 in the surgical eye.

A 50-year-old female presented to our clinic seeking decreased dependence on both distance and near vision correction. Her UDVA was 20/40 OD, OS, and OU. Her UNVA was J10 OD, J8 OS, and J6 OU. She was wearing “cheaters” for distance vision and stronger cheaters for near vision. Occasionally, the patient would wear a monovision contact lens in her right eye, but not full time as she did not like the degree of blur for distance activities. Her manifest and cycloplegic refraction were +1.50 +0.75 x 065 OD and +1.25 +1.00 x 088 OS with 20/20 acuity. Slit lamp and dilated fundus examination were normal. The patient had normal topography and her central corneal thickness was 538 OD and 527 OS. Figure 7-5 shows the preoperative Pentacam map for the patient’s right eye. The patient elected to proceed with LASIK in both eyes with Raindrop implantation in her right eye. The patient underwent successful LASIK with a plano target for each eye then subsequent Raindrop inlay implantation in her right eye. The flap thickness of the right eye was 170 μm, which provided appropriate depth for Raindrop inlay implantation with adequate residual corneal bed following LASIK ablation.

The first day postoperatively, the patient’s UDVA was 20/50 OD and 20/20 OS. UNVA was J1 OD, J5 OS, and J1 OU. At 6 months postoperatively, the patient’s UDVA was 20/40 OD, 20/20 OS, 20/20 OU, and manifest refraction -1.00 +0.35 x 115 OD and -0.25 OS. The patient’s uncorrected near vision was J1+ OD, J5 OS, J1+ OU. The patient denied needing glasses at any distance. Figure 7-6 shows the patient’s postoperative Pentacam Holladay report. Figure 7-7 shows the Pentacam densitometry, and Figure 7-8 shows a slit lamp image of the patient’s Raindrop inlay 6 months postoperatively.

This patient case shows a successful result with a combined surgical procedure on the same day. Because the ideal refractive error for Raindrop implantation is plano or mildly hyperopic, the patient was targeted for a plano refraction. The pearl to remember when planning a procedure of this nature is to adjust the LASIK flap for the increased thickness required to minimize risk of corneal haze while maintaining appropriate residual corneal bed thickness.

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