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Decentered multifocal IOLs may be cause of worsened vision
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Decentration of a multifocal IOL is not always obvious and may be the cause of poor vision in patients who had a seemingly normal cataract extraction, according to a presentation by Uday Devgan, MD, at Hawaiian Eye 2015.
Patient example
First, the surgeon must determine the cause of the problem at the slit lamp before performing more detailed examinations.
Devgan, OSN Healio.com/Ophthalmology Section Editor, presented one example in which a 74-year-old patient underwent cataract extraction with implantation of a multifocal lens in the left eye. Immediately after surgery, his uncorrected visual acuity was 20/25 and the IOL was well-centered. Six weeks postoperatively, however, visual acuity decreased to 20/100 with an induced cylinder. Maximum pupil dilation was 4 mm. Tomography and topography were normal, but closer inspection at the slit lamp revealed the decentered IOL.
The IOL decentered and tilted because one haptic was placed in the capsular bag while the other was outside of it. When the capsular bag contracted, it caused the IOL optic to shift out of the visual axis. In this case, the fix was to re-inflate the capsular bag and place both haptics within it.
In other cases, patients with decentered diffractive multifocal lenses may complain of ghosting, or double vision. When that happens, Devgan said he photographs the retina through the IOL.
“Lo and behold, when I take a photograph of the retina through their IOL, I get ghosting, too, of the retinal fundus photo,” he said.
A decentered multifocal IOL. Iris trans-illumination defect caused by the haptic in the sulcus.
Image: Devgan U
IOL tilting
In Z syndrome, or tilting of the IOL into a Z-shaped configuration seen in the first-generation accommodating lenses, irregular capsular contraction can cause the IOL to shift, Devgan said, with such a tilt inducing astigmatism.
In a case with a small rhexis and capsular phimosis, the IOL not only tilts to cause the cylinder, but also moves posteriorly in the eye, therefore inducing hyperopia, he said. The treatment in this case would be a YAG laser lysis of the anterior capsular rim.
In contrast, in posterior capsule fibrosis, fibrotic bands cause the IOL to shift forward, therefore inducing myopia and cylinder. In this case, the YAG laser can be used to perform a small posterior capsulotomy.
“I’ll just tell a patient, if you’re going to get this type of accommodating lens, I will need to do a YAG laser 100% of the time in the first few months after surgery to lock the lens in place,” Devgan said. “I’ll YAG the anterior rim 12 to 6, 3 to 9, and then perform a small posterior capsulotomy, and now that lens is locked in. No fibrotic bands are going to cause the lens to shift. There cannot be an anterior capsule phimosis anymore. It’s ready to go. It will be stable in the long term.”
Further surgery
“Remember only one thing: The IOL isn’t going to recenter itself,” Devgan said. “So, if the lens is decentered to any degree, you’re going to need to go back in the eye and put it back in the appropriate position, and sometimes even exchange these lenses for a simple monofocal lens.”
For these more complicated cases that need further surgery, Devgan said he uses additional documentation to help educate patients and set realistic expectations for the second surgery. These re-operations are more challenging and higher risk than the original cataract surgery.
If a decentered IOL with an open posterior capsule and vitreous prolapse is found, anterior vitrectomy should be performed. The lens is then typically replaced with a monofocal IOL. In worst-case scenarios, decentered IOLs simply have to be explanted if they cannot be fixed, Devgan said. – by Kristie L. Kahl
For more information:
Uday Devgan, MD, can be reached at Devgan Eye Surgery, 11600 Wilshire Blvd. #200, Los Angeles, CA 90025; email: devgan@gmail.com.Disclosure: Devgan reports he is a consultant for Alcon, Bausch + Lomb and Gerson Lehrman; is a stockholder in LensGen and Specialty Surgical; and receives royalties from Accutome.