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Ultrasound Biomicroscopy of an Implantable Miniaturized Telescope
Arch Ophthalmol. 2001;119:1544-1546.
INTRODUCTION
Age-related macular degeneration (ARMD) is a leading cause of visual loss in adults older than 60 years.1 Once central vision has been seriously jeopardized, visual function can only be improved with optical devices that produce magnification of near and distant images. Koziol et al2 reported the use of a teledioptric lens implant with a high-minus central zone (2.5 mm). When this implant is used in combination with eyeglasses as part of a teledioptric system, the magnified visual field obtained is 2.6 times greater than that achieved using an external telescope (magnification power, x3; focusing distance, 50 cm; magnification power with the aid of external spectacles, x8; visual field, 6,6° equivalent to 20° in the retina). However, the disadvantages found when a combined telescopic system is used still occur. The implantable miniaturized telescope (IMT) (VisionCare Ophthalmic Technologies Ltd, Yehud, Israel) designed by Lipshitz et al3 should partially prevent the discomfort involved when an external or partially external telescope is used. The IMT is mounted on an intraocular lens implant and consists of a glass Galilean telescope (4.4 mm long and 3.2 mm in diameter) installed in a hole centered in a plate-design polymethyl methacrylate intraocular lens (7.0 x 4.75 mm) (Figure 1). The total diameter of the device is 13.5 mm. Implantation of the IMT is performed by widening up to 8 mm the incision after lens phacoemulsification with scleral incision and capsulorrhexis, which theoretically ensures the intracapsular implantation and thus stability and adequate position of the IMT.
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Figure 1. Implantable miniaturized telescope before implantation. Note the plate design of the intraocular lens, with the telescope installed in its center.
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The capacity of ultrasound biomicroscopy (UBM) to study the anterior segment makes it possible to analyze the position of these lenses and to accurately evaluate the relationships between the IMT and the anterior pole structures, ie, the endothelium.4
We present the findings from UBM performed in 2 patients who underwent IMT implantation for ARMD.
Both UBMs were performed using the UBM 840 (50 MHz) (Zeiss Humphrey, Palo Alto, Calif) 1 month after surgery. The patients were scanned by the same examiner (J.G.-F.), with the patient in the supine decubitus position while under topical anesthesia according to the technique described by García-Feijoó et al5 using an orbital cup and a lid speculum. The examinations were videotaped for later study.
Twelve radial hour scans covering the 360° of the angular region were acquired for each eye. The minimum distance to the endothelium was measured and the haptic position was determined. A central scan through the corneal apex was obtained to measure the distance from the IMT center to the endothelium.
Before surgery, a complete ophthalmologic examination was performed, including an endothelial cell count and anterior chamber depth measurement. Both patients gave written informed consent in accordance with the Helsinki Declaration. After surgery, both patients began special training with a low-vision specialist, who refracted the patients following the recommendations of the manufacturer.
Report of Cases
Case 1
A 74-year-old man diagnosed as having dry ARMD underwent IMT implantation in his left eye and experienced no complications. Preoperative best-corrected visual acuity was 20/200 (refraction, +1.75, -0.75 x 95°; addition, +3.0 diopters [D]; and near vision, J10). The patient's endothelial cell count was 2690 cells/mm2; Javal keratometry, 44.25 x 45.25 at 175°; and anterior chamber depth, 3.22 mm. One month after surgery, his best-corrected visual acuity was 20/200; near vision, J10 with +3.0 at 30 cm; and Javal keratometry, 42.5 x 46.5 at 170°.
The UBM images showed that one of the haptics of the IMT was placed in the sulcus (inferotemporal section, 5-hour position), producing a sectorial angular closure (Figure 2 and Figure 3). When the endothelium-IMT measurements were analyzed, the minimum distance in this zone was 1.2 mm. The minimum distance in the 11-hour section was 1.4 mm (Figure 2). The central distance between the lens surface and the endothelium was 1.5 mm. The minimum distance found in the 360° was 1.1 mm.
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Figure 2. Reconstruction of the anterior chamber in patient 1 (3 consecutive scans: 2-7 hours). The inferior haptic is placed in the sulcus and the superior haptic is placed in the capsular bag (H). The double-headed arrows indicate the distances between the endothelium and the implantable miniaturized telescope; INC, incision.
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Figure 3. Partial closure of the angle produced by the haptics (patient 1). The arrow indicates the scleral spur; H, implantable miniaturized telescope haptic; and CB, ciliary body.
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Case 2
A 75-year-old woman diagnosed as having dry ARMD underwent IMT implantation in her right eye and experienced no complications. Her preoperative best-corrected visual acuity was 20/200 (refraction, -0.5, -0.5 x 90°; addition, +3.0 D; and near vision, J16). The endothelial cell count in her right eye was 2344 cells/mm2, Javal keratometry was 44.25 x 43.0 at 30°, and anterior chamber depth was 3.47 mm. One month after surgery, her best-corrected visual acuity was 20/100; near vision, J10 with +2.0 D at 30 cm; and Javal keratometry, 45.5 x 41.5 at 180°.
The UBM images showed that the superior haptic was placed in the sulcus, causing partial closure of the angle (Figure 4), and the inferior haptic was placed in the capsular bag. The minimum distance between the endothelium and an edge of the IMT was 967 µm (superonasal, 11-hour position), the central distance being 1.6 mm. In this case, the IMT inclination was seen more clearly (Figure 5).
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Figure 4. Detail of the implantable miniaturized telescope (IMT) plate (small arrows) and the haptic, which is indenting (large arrow) and tilting the iris upward (patient 2).
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Figure 5. Central section. The implantable miniaturized telescope is shifted in regard to the corneal apex and is slightly inclined (patient 2).
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Comment
Because of the optic characteristics of the lens and its size, significant stability and correct centering is required, and this can only be guaranteed by performing a capsulorrhexis and intracapsular implantation of the IMT. However, although an experienced surgeon in ordinary intraocular lens implantation (M.Z.G.L.) performed the implantations in both patients, one of the haptics was placed in the sulcus. Logically, the distance between the IMT and the endothelium is less in this zone, and a slight tilt of the intraocular lens is produced (Figure 4) that prevents the IMT from having an optimum position from the optical point of view. This fact, together with initial poor visual acuity, could be the reason for the slight objective improvement in patient 2 and the null improvement in the first patient. Nevertheless, at the postoperative follow-up examination, the patients' ability to watch television improved and they reported better orientation at the table (especially patient 2); both patients noticed that their ability to read had improved. Despite this subjective visual improvement, the small distance between the IMT and the cornea could affect the endothelium in the long term. Thus, if patient age and visual expectancy are taken into account, the implantation of these lenses could be justified with adequate selection of the patients, and one of the most important preoperative factors should be the depth of the anterior chamber.
Therefore, because of the IMT morphologic features, we not only should select patients who present a wide anterior chamber but also must make sure that the implantation of the lens is intracapsular to try to increase the distance between the IMT and the endothelium as much as possible. For these reasons, and regardless of their possible functional effectiveness, these implantations present significant surgical challenges and risks, even in the hands of an experienced surgeon.
AUTHOR INFORMATION
Julián García-Feijoó, MD, PhD;
Sonia Durán-Poveda, MD;
Ricardo Cuiña-Sardiña, MD;
Carmen Méndez-Hernandez, MD;
Julián García-Sánchez, MD, PhD;
Miguel Zato Gómez de Liaño, MD, PhD
Madrid, Spain
Corresponding author and reprints: Julián García-Feijoó, MD, PhD, C/ San Francisco de Sales 12 (6°A), 28003 Madrid, Spain (e-mail: mherrerad{at}sego.es).
REFERENCES
1. Vingergling JR, Dielemans I, Hofman A, et al. The prevalence of age-related maculopathy in the Rotterdam Study. Ophthalmology. 1995;102:205-210.
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2. Koziol J, Peyman GA, Cionni R, et al. Evaluation and implantation of a teledioptric lens system for cataract and age-related macular degeneration. Ophthalmic Surg. 1994;25:675-684.
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3. Lipshitz I, Lowenstein A, Reingewirth M. An intraocular telescopic lens for macular degeneration. Ophthalmic Surg Lasers. 1997;28:513-517.
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4. Tello C, Liebmann J, Potash SD, Cohen H, Ritch R. Measurement of ultrasound biomicroscopy images: intraobserver and interobserver reliability. Invest Ophthalmol Vis Sci. 1994;35:3549-3552.
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5. García-Feijoó J, Martín-Carbajo M, Benitez del Castillo JM, García-Sánchez J. Orbital cup: a device to facilitate ultrasound biomicroscopic examination of pars plana and peripheral retina. Arch Ophthalmol. 1997;115:1475-1476.
ABSTRACT
SECTION EDITOR: W. RICHARD GREEN, MD
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