Keratoconus is a noninflammatory disease characterized by thinning of the central stroma and anterior corneal protrusion.1 This corneal architectural distortion results in myopia and irregular astigmatism that impair the quality of vision. Keratoconus management is a spectrum of therapy that progresses from no treatment to correction with glasses to contact lenses and finally to surgery. The appropriate treatment depends on the disease and visual requirements. Cases of mild keratoconus are treated with spectacles or contact lenses. Contact lens wear becomes necessary when conic progression increases the degree of irregular astigmatism. Keratoplasty is performed when patients cannot tolerate contact lenses or achieve satisfactory vision with them.
Intraocular images become distorted because of corneal irregular astigmatism in patients with keratoconus (Figure 1). However, the image distortion can be reduced with use of a rigid gas-permeable (RGP) contact lens. When cataract surgery is performed in keratoconus patients, poor visibility due to corneal irregular astigmatism can lead to complications, including posterior capsule rupture and corneal endothelial cell damage. We describe the use of RGP contact lens–assisted cataract surgery to overcome the poor visibility.
After topical anesthesia and sub-Tenon anesthesia are induced with lidocaine 2.0%, an ophthalmic viscosurgical device (OVD) (Healon) is applied to the cornea. An RGP contact lens (Hoya Hard Ex, Hoya Corp.) (7.8 mm base curve, 8.8 mm diameter, 0 diopter power) is sterilized using low temperature (55°C for 210 minutes) ethylene oxide gas sterilization. The RGP contact lens is placed stably in the center of the cornea on the OVD despite corneal irregularity.
A capsulorhexis is created successfully using a 27-gauge bent-tip needle with the RGP contact lens in place. During phacoemulsification without the RGP contact lens, the images are distorted (Figure 2) (Video 1, available at http://jcrsjournal.org). However, the image distortion significantly decreases with use of the RGP contact lens. The intraocular image can be seen clearly and the opacified lenses chopped successfully using a bimanual phacoemulsification procedure as during standard cataract surgery. Phacoemulsification with a torsional oscillation system is performed safely and effectively, and the lens particles are aspirated smoothly in the phaco tip along with the fluidics.
Image distortion is worse without the RGP contact lens while irrigation/aspiration (I/A) is performed in the posterior chamber (Figure 2). The tip of the instrument appears enlarged and crooked without the contact lens; with the contact lens, the view improves markedly. Thus, the residual cortex is clearly visible and removed safely. Visualization of the anterior and posterior capsules is confirmed easily with the contact lens after I/A; however, transillumination is disrupted when the contact lens is removed (Figure 2).
A foldable acrylic intraocular lens (IOL) can be safely inserted through a 2.4 mm sclerocorneal incision using an injector and cartridge, and the IOL is dialed into the capsular bag when the circular capsulorhexis edge is visualized using the RGP contact lens. The RGP contact lens is removed from the cornea using forceps at the end of the procedure.
Rigid gas-permeable contact lens–assisted cataract surgery was performed in 2 patients with severe keratoconus who requested cataract surgery without keratoplasty (Figure 3). In the first patient, the visual acuity improved from light perception to 20/1000 (Figure 3, A and B). In the second patient, the visual acuity improved from 20/667 to 20/100 (Figure 3, C and D). No intraoperative or postoperative adverse events occurred.
In our cases, both patients requested only cataract surgery without keratoplasty. Although corneal crosslinking and intrastromal corneal ring segments are possible treatments for keratoconus patients,3,4 we did not think they were applicable in these cases because the central corneal thicknesses were less than 400 μm and the keratoconus was classified as stage 4 (Amsler-Krumeich classification2).
Cataract surgery in patients with severe keratoconus is challenging because of poor intraocular visibility. We overcame the challenge using an RGP contact lens. Although an OVD can be applied to make the corneal surface smooth during cataract surgery, the RGP contact lens offers an advantage. It can provide an ideal optical surface independent of the corneal surface, whereas the corneal surface coated with only OVD can be irregular because of astigmatism. Therefore, the RGP can offer the best visualization in cases with severe keratoconus. The corneal safety of the RGP contact lens has been established during the many years it has been used for optical correction of keratoconus.5 The RGPs are readily available for use.
Intraocular image distortion and the subsequent lack of visual perspective are the main problems during capsulorhexis, phacoemulsification, and I/A. However, visualization improves with use of an RGP contact lens, which makes it easy to obtain z-axis information. The anterior capsule can be controlled with a 27-gauge bent-tip needle during capsulorhexis with an RGP contact lens in place. For a phaco-chop procedure, the emulsification tip should be used to impale the nucleus and knowledge of the depth of the instrument is very important. For divide-and-conquer techniques, the depth of the emulsification tip is important to divide the nucleus effectively. Use of an RGP contact lens facilitates acquiring information regarding the depth. The degree of image distortion in the same patient depends on the distance between the surgical instruments and the cornea. Distortion was the worst during I/A. Thus, this technique has the greatest effect on image improvement during manipulation in the posterior chamber, including I/A. Improvements in image distortion and visual perspective result in efficient and safe manipulation of the residual cortex. The RGP contact lens also improves transillumination. It is very important to confirm the posterior capsule for safe IOL insertion. We recommend that this technique also be used for this purpose.
Kamei et al.6 reported the effectiveness of an RGP contact lens to protect the cornea from drying during vitrectomy with a wide-angle viewing system. The RGP contact lenses provided visibility similar to or clearer than that obtained with balanced salt solution, an OVD, a vitrectomy contact lens, or a soft contact lens. Because of the ease of use and low cost, an RGP contact lens is ideal for use during vitrectomy with a wide-angle viewing system. This suggests that RGP contact lenses can also be used to protect the cornea from drying during cataract surgery.
The diameter of the RGP contact lens used in the current study was 8.8 mm, which was smaller than the corneal diameter. Because the visual field is limited to the lens diameter in this technique, a larger lens would offer a larger visual field. A lens with an 11.0 mm diameter or larger can be used for this purpose in a future study.
To our knowledge, this is the first description of RGP contact lens–assisted cataract surgery in patients with severe keratoconus. The technique is simple and can be performed by many surgeons. Rigid gas-permeable contact lens–assisted cataract surgery provides excellent visualization during cataract surgery in patients with severe keratoconus. In our 2 cases, the method was safe and effective.
What Was Known
- Cataract surgery in patients with severe keratoconus is challenging because of poor intraocular visibility.
What This Paper Adds
- Rigid gas-permeable contact lens–assisted cataract surgery offers marked improvements in intraocular image distortion, visual perspective, and transillumination during surgery.
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Video 1 The intraocular image is distorted without an RGP contact lens in place; however, the image distortion is significantly decreased with the contact lens. The image distortion is worst during I/A. Although the tip of the instrument becomes enlarged and distorted markedly without the contact lens, the visualization improves markedly with the contact lens in place.