Retinal images viewed through a small aperture corneal inlay

Abstract

Presbyopia is a visual disability of the ageing eye caused by a loss of accommodation of the crystalline lens (Charman 2008). To treat presbyopia, the Kamra corneal inlay (AcuFocus, Inc., Irvine, CA, USA) was designed with a small aperture, which increases the depth of focus (Yılmaz et al. 2011; Tomita et al. 2012). The inlay is 5 μm thick and incorporates carbon nanoparticles to create a 3.8-mm-diameter opaque sheet with a clear central aperture of 1.6 mm with zero refractive power (Yilmaz et al. 2008). The inlay was reported not to affect the ophthalmoscopic view of the central and peripheral fundus, and high-quality central and peripheral fundus photographs and optical coherence tomographic (OCT) images could be obtained in eyes implanted with the inlay (Casas-Llera et al. 2011). However, it has not been determined how the inlay affects the retinal images when patients require vitreoretinal surgeries in eyes with dark-coloured rings in the centre of the cornea. A 48-year-old woman visited Minatomirai Eye Clinic for symptomatic floaters in the left eye implanted with a Kamra cornea inlay. Routine retinal examination was performed, including a detailed retinal examination with a slit-lamp microscope and a Goldmann three-mirror contact lens (OG3MFA; Ocular Instruments, Washington, DC, USA) after the pupil was dilated by a topical mydriatic drug. Fundus photographs were taken with a retinal camera (Mark2 NW7SF; Topcon Corp, Tokyo, Japan) with a 50-degree angle and fundus images through a three-mirror contact lens with a slit-lamp microscope connected to a video camera mounted on a slit-lamp microscope. The uncorrected decimal distant vision in the left eye of the patient implanted with the inlay was 1.2, and the uncorrected near vision was 0.8. The funduscopic images through the indirect ophthalmoscope and fundus photographed through the inlay were clear (Fig. 1). However, with a slit-lamp microscope, a blurred dark ring was observed through the centre lens of the Goldmann three-mirror contact lens. When the focus was moved to the cornea, the dark ring became sharper and was noticed to originate from the inlay. In the fundus image through the Goldmann three-mirror contact lens, another dark shadow projected on the retina was observed aside of the dark ring, which moved according to the direction of the slit-light beam by shifting a slit-lamp lever and was considered to be a shadow of the inlay. The central lens of the Goldmann three-mirror lens has a flat front surface, and it had the same optical structure as the flat contact lens used for vitrectomy but without endoillumination. The light passes through all parts of the optics of the crystalline lens or the intraocular lens (IOL) within the diameter of the pupil with the flat or prism contact lens system during vitreous surgery or a three-mirror contact lens. This is the reason why a defocused dark ring was observed in the visual field with a three-mirror contact lens. Yılmaz et al. (2011) described two cases that underwent phacoemulsification with IOL implantation with no intraoperative complications 3 and 4 years after the inlay implantation. When vitreous surgery was performed with a flat contact lens and the focus was on the retina, the dark ring was more defocused resulting in a decrease in contrast of the retinal images. To avoid blocking the view of the retina, the eye must be rotated during vitreous surgery. Otherwise, the corneal inlay can be removed before the vitreoretinal surgery. Using a wide-angle viewing system which has a similar optical system as the indirect ophthalmoscope and fundus camera, may be recommended to increase the quality of view.