Intracorneal ring segment, phakic IOL implantation enable keratoconus management without keratoplasty

A physician describes a therapeutic bioptics approach to treating keratoconus that avoids corneal transplantation.

Thomas John

Keratoconus treatment is an integral part of most ophthalmic practices. Keratoconus is noninflammatory, bilateral corneal ectasia in which corneal thinning and protrusion induce irregular astigmatism and myopia, resulting in visual degradation. This progressive disorder has an incidence in the general population of about one in 2,000.

Although keratoconus is diagnosed in a clinical setting, it has typical histopathologic features including breaks in the Bowman’s layer, iron in the epithelial basement membrane and stromal thinning. Clinically, other conditions that need to be ruled out are keratoglobus and pellucid or Terrien’s marginal degeneration. Keratoconus is usually an isolated condition but may be associated with Down syndrome, mitral valve prolapse and Leber’s congenital amaurosis. While the etiology of keratoconus remains elusive, genes appear to play a major role, and research seems to point toward increased keratocyte apoptosis, imbalance in proteinase inhibitors, degradative enzymes and the interleukin-1 system.

A stepladder approach to visual rehabilitation of keratoconus patients includes eyeglasses, contact lenses and finally surgical intervention — namely, deep anterior lamellar keratoplasty or penetrating keratoplasty, especially when the keratoconus is associated with full-thickness, central or paracentral corneal scar. Newer therapeutic modalities include corneal collagen cross-linking to stabilize an otherwise often progressive disease process, particularly in younger patients. Intracorneal ring segments such as Intacs (Addition Technology) and Kerarings (Mediphacos) offer yet another therapeutic avenue.

In this column, Dr. Ambrósio describes a “therapeutic bioptics” approach by combining Kerarings with a phakic IOL to manage advanced keratoconus to avoid corneal transplantation. Further clinical investigations are warranted to evaluate the long-term validity, safety and usefulness of this newer surgical approach.

Thomas John, MD
OSN Surgical Maneuvers Editor

by Renato Ambrósio Jr., MD, PhD

A 37-year-old female nurse was referred for a second opinion and surgical management of keratoconus. She had no eyeglasses and developed an intolerance to contact lenses, mainly in the right eye, over the past year. She was seeking alternative treatments to the lamellar or penetrating keratoplasty recommended by previous ophthalmologists.

Clinical findings

Uncorrected distance visual acuity was counting fingers at 10 cm in the right eye and counting fingers at 2 m in the left eye. Manifest refraction revealed best corrected visual acuity of 20/200 in the right eye and 20/40 in the left eye, with –6.00 –4.75 × 25 in the right eye and –6.25 –2.00 × 89 in the left eye facilitated by ocular wavefront using a single-laser-beam ray-tracing approach (iTrace, Tracey Technologies). IOP was normal in both eyes with an unstable tear film, presence of mild inferior corneal punctate epitheliopathy and mild tarsal conjunctival papillae. Inferotemporal corneal thinning with an incomplete paracentral Fleischer ring and exacerbated corneal nerves were observed in both eyes. A positive Munson’s sign was noted in the right eye. No epithelial or subepithelial scarring or striae were present.

Axial curvature maps from Placido-disk-based corneal topography revealed findings in both eyes similar to those of rotating Scheimpflug tomography with a Pentacam HR (Oculus). Inferior corneal steepening was more pronounced in the right eye, with steepest keratometric readings of 56 D in the right eye and 55 D in the left eye. Central and minimal corneal thickness was 421 µm and 392 µm in the right eye and 453 µm and 388 µm in the left eye (Figures 1 and 2). Schirmer’s test with topical anesthesia at 5 minutes revealed 8 mm and 9 mm of wetting in the right and left eyes, respectively.

Figure 1. Pentacam corneal front curvature (axial or sagittal) maps in both eyes.

Figure 2. Scheimpflug images of both eyes. Images: Ambrósio R

We discussed the diagnosis of keratoconus and contact lens intolerance related to overlapping tear film dysfunction and chronic allergic conjunctivitis. Lamellar and penetrating keratoplasty were discussed and considered as last options. Other surgical approaches for keratoconus were discussed. Inferior punctal plugs were implanted in both eyes. Eyeglasses were prescribed, and the patient was advised not to wear contact lenses for the next several weeks. She was started on artificial tears, topical anti-allergic drops and oral nutritional supplementation with omega-3 essential fatty acid.

Intracorneal ring segment implantation

The patient returned 1 month later with significant symptomatic improvement in both eyes and visual improvement in the left eye with glasses, but she requested surgery in the right eye. Keraring implantation assisted by IntraLase iFS laser (Abbott Medical Optics) was performed in the right eye. An SI-6 model Keraring with 210° arc length and 200 µm segment was chosen due to the relatively thin cornea and according to the philosophy of regularizing corneal shape rather than aiming for sphere correction. The incision length was 1.1 mm. The incision axis was 120°, with the upper ring segment edge at the limit (ie, 130°) for the depressed lake on the enhanced front elevation map (Figure 3, red arrow) and reaching the end limit of the depressed lake (Figure 3, blue arrow). IntraLase iFS was set for lamellar ring dissection at a depth of 300 µm, inner diameter of 5 mm and external diameter of 5.9 mm. Energy was optimized according to manufacturer recommendations at 1.4 mJ for the lamellar ring dissection and 1.1 mJ for the entry cut.

Figure 3. Belin/Ambrósio enhanced ectasia display of right eye.

Phakic IOL implantation

The patient reported noticing significant improvement in her vision quality. One month after surgery, uncorrected distance visual acuity was 20/100 in the right eye. The curvature map was more regular after surgery. The applanation effect of the ring segment was observed on the differential map (Figure 4). Manifest refraction spherical equivalent was –6.50 D, with a visual acuity of 20/25. The topographic and refraction statuses were confirmed as stable about 12 weeks after the intracorneal ring segment procedure. Considering the normal endothelial cell count (2,905 cells/mm²) and anterior chamber depth of 3.2 mm from the endothelium, a phakic IOL was considered.

The AcrySof Cachet (Alcon) was implanted in the right eye with no complications. At 4 hours postop, uncorrected distance visual acuity was 20/40, and the patient experienced mild discomfort in the right eye. The eye was quiet, with the phakic IOL in good position (Figure 5). IOP was 30 mm Hg in the right eye. A paracentesis was performed to egress aqueous humor, which reduced the IOP to 15 mm Hg. The Ocular Response Analyzer (ORA, Reichert) revealed similar IOP findings (Figure 6). At 1 year after phakic IOL implantation, uncorrected distance visual acuity was 20/30+, best corrected to 20/25 with –0.25 –0.75 × 16 in the right eye. The eye was quiet, and the intracorneal ring segments and phakic IOL were stable (Figure 7), with no signs of inflammation. Endothelial cell count was 2,795 cells/mm².

Figure 4. After Keraring implantation (a), preop (b), subtraction map (c) and tomogram based on Scheimpflug images identifying the intracorneal ring segments (d).

Figure 5. Slit lamp image taken 4 hours after phakic IOL implantation.

Figure 6. ORA signal and metrics 4 hours after phakic IOL implantation before (a) and after (b) paracentesis opening for draining aqueous humor.

Figure 7. Scheimpflug image after intracorneal ring segment and phakic IOL implantation.

Therapeutic bioptics

This case illustrates the significant improvement in keratoconus surgical management related to refractive surgery. Deep anterior lamellar keratoplasty is a preferred option for most keratoconus cases, with significant advantages over PK. However, non-transplantation options should be considered. Corneal cross-linking is a procedure that aims to stabilize the progression of ectasia while improving unpredictable vision. Custom surface ablation with corneal cross-linking as described in the Athens protocol is an alternative to intracorneal ring segments to regularize the cornea. Either procedure should be considered to regularize the cornea and reduce the irregular astigmatism. Myopia correction should not be the goal of the surgeon when planning such treatments.

In this case, according to the Mediphacos nomogram aiming for refractive correction, a Keraring SI-5 with 210° of arc length and 300 µm thickness would be advised. Typically a 50 µm thicker segment is advised for the SI-6. However, due to the relatively thin cornea and the philosophy of regularizing corneal shape rather than aiming to correct lower-order aberrations, a thinner segment was chosen. A phakic IOL after the corneal procedure may be a preferred approach to treat lower-order aberrations. The term “therapeutic bioptics” may be appropriate for describing this combination of corneal and intraocular surgery for postponing and/or avoiding corneal transplantation.

References:

• Alfonso JF, Lisa C, Fernández-Vega L, Madrid-Costa D, Poo-López A, Montés-Micó R. Intrastromal corneal ring segments and posterior chamber phakic intraocular lens implantation for keratoconus correction. J Cataract Refract Surg. 2011;37(4):706-713.
• Khan MI, Injarie A, Muhtaseb M. Intrastromal corneal ring segments for advanced keratoconus and cases with high keratometric asymmetry [published online ahead of print Nov. 4, 2011]. J Cataract Refract Surg. doi:10.1016/j.jcrs.2011.07.031.
• Knorz MC, Lane SS, Holland SP. Angle-supported phakic intraocular lens for correction of moderate to high myopia: Three-year interim results in international multicenter studies. J Cataract Refract Surg. 2011;37(3):469-480.
• Kohnen T, Klaproth OK. Three-year stability of an angle-supported foldable hydrophobic acrylic phakic intraocular lens evaluated by Scheimpflug photography. J Cataract Refract Surg. 2010;36(7):1120-1126.
• Kubaloglu A, Sari ES, Cinar Y, Koytak A, Kurnaz E, Ozertürk Y. Intrastromal corneal ring segment implantation for the treatment of keratoconus. Cornea. 2011;30(1):11-17.
• Sedaghat M, Ansari-Astaneh MR, Zarei-Ghanavati M, Davis SW, Sikder S. Artisan iris-supported phakic IOL implantation in patients with keratoconus: a review of 16 eyes. J Refract Surg. 2011;27(7):489-493.

• Renato Ambrósio Jr., MD, PhD, is the director of cornea and refractive surgery at the Instituto de Olhos Renato Ambrósio, Visare Personal Laser and Refracta-RIO; founder and scientific coordinator of the Rio de Janeiro Corneal Tomography and Biomechanics Study Group; and associate professor of ophthalmology at the Pontifícia Universidade Católica in Rio de Janeiro and Federal University of São Paulo. He can be reached at 55-21- 2274-5694; email: dr.renatoambrosio@gmail.com.
• Edited by Thomas John, MD, a clinical associate professor at Loyola University at Chicago and in private practice in Oak Brook, Tinley Park and Oak Lawn, Ill. He can be reached at 708-429-2223; fax: 708-429-2226; email: tjcornea@gmail.com.
• Disclosures: Dr. Ambrósio is a consultant to Oculus. Dr. John has no relevant financial disclosures.