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Modern phacoemulsification safe, successful even for high myopes
Preventing forward movement of the vitreous body decreases the chance of retinal complications.
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Treating highly myopic cataract patients is a challenge. Historically, cataract surgery has been associated with retinal detachment in high myopes, but we believe that modern small-incision surgical techniques significantly diminish the risk in uncomplicated cases. Avoiding capsular tears and vitreous loss, maintaining constant anterior chamber depth and implanting foldable posterior chamber IOLs all help in preventing detachment.
On the other hand, Nd:YAG capsulotomy is associated with an increased incidence of retinal detachment, due to changes in the rate of vitreous syneresis and thus retinal traction.
Because of this increased risk, we have moved to a more conservative approach of doing the laser procedure without dilating the pupil and with minimal use of energy.
Patients and methods
Between March 1996 and August 2000 we treated 73 eyes of 40 highly myopic cataract patients using modern phaco techniques and small temporal clear corneal incisions. The mean axial length of our cases was 26.9 mm, ranging from 25.1 mm to 32.2 mm. The mean age was 60 years.
In four cases with symptomatic posterior subcapsular cataracts, we treated retinal peripheral lesions with low argon-laser energy 1 month preoperatively, and in three cases postoperatively in order to reduce the chance of retinal complications. Topical and/or intracameral anesthesia was used in most cases.
All patients received foldable acrylic posterior chamber IOLs with sharp rectangular optic edges (AcrySof MA60AM, Alcon). Four patients received acrylic foldable minus-power lenses (Cornéal ACR 6D). In eight very long eyes we used the Holladay II formula to calculate the IOL power, because it is the most accurate formula for long eyes.
The size of the temporal clear corneal incision made by the 3D diamond knife (Rhein Medical) ranged from 2.9 mm to 3.1 mm. The balanced salt solution bottle was located 40 cm to 50 cm above the eye, not allowing the anterior chamber to become too deep.
The posterior capsule was polished, and in many cases so was the anterior capsule. There was no posterior capsule rupture or vitreous loss during surgery.
Eight eyes had Nd:YAG small capsulotomy for significant posterior capsular opacification without dilating the pupils.
Mean follow-up after capsulotomy was 29 months. We had no cases of clinical cystoid macular edema after the Nd:YAG capsulotomy. No retinal detachment occurred in our cases during the mean follow-up of 49 months.
Discussion
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Forward movement of the vitreous body in turn results in posterior vitreous detachment. Prevention of forward movement — by use of viscoelastics, phaco unit fluidics and small-incision wounds — decreases the chance of retinal complications.
Proper treatment of suspicious retinal degeneration before or after surgery also minimizes the chance of retinal detachment, although there is an opposite argument that prophylactic treatment could impair the vitreoretinal junction.
It should be emphasized that highly myopic eyes are accompanied by low-risk lesions at the periphery of the retina, and they deserve meticulous retinal review and follow-up.
Posterior chamber IOL implantation is also critical, because this IOL maintains a more normal vitreous-capsule interface, which alleviates changes in anterior displacement and traction on the vitreous base.
Acrylic IOLs, because of their sharp edges, also prevent PCO, reducing the need for Nd:YAG capsulotomy.
Although the number of cases in our study is limited, we believe that Nd:YAG capsulotomy performed with an undilated pupil is not a risk factor for retinal detachment, because the opening is too small for forward movement of the vitreous body and resulting retinal traction.
We have also observed over a long period of time that Nd:YAG capsulotomy with an undilated pupil was not a risk for an extensive number of cases of nonmyopic cataract eyes.
Additionally, we now have computer-driven technology and the capability to increase safety and make cataract surgery less traumatic than ever. Older published data notes a chance of retinal detachment of up to 4% after such surgery. But these data include extracapsular as well as phaco cases using different incision sizes, different machines and fluidics.
The latest innovations encourage us to proceed, in a similar way, to clear lens exchange surgery, the only way to permanent refractive surgery for highly myopic eyes.
Conclusion
Modern cataract surgery in highly myopic eyes seems to be a safe and uncomplicated procedure. We attribute this to small incision size, continued maintenance of the anterior chamber, posterior chamber acrylic IOL implantation and, in the case of secondary cataract, a small capsulotomy size with an undilated pupil.
For Your Information:
- Zissis Bisogiannis, FEBO, MD, can be reached at Patr. Joakin 53 St., Athens, 106 76, Greece; phone/fax: +(30) 1-0723-5217; e-mail: zissisbisogiannis@hotmail.com.