Proper specialized instrumentation and a dispersive ophthalmic viscosurgical device are integral to the success of explantation and exchange of multifocal IOLs.
San Francisco-Proper specialized instrumentation and a dispersive ophthalmic viscosurgical device (OVD) are integral to the success of explantation and exchange of multifocal IOLs.
It is important to rule out other causes of the patient's "unsatisfactory" vision, said Dr. Chang, clinical professor of ophthalmology at the University of California, San Francisco, and a private practitioner in Los Altos, CA. Frequently, the patient's dissatisfaction, disappointment, concern, and anxiety may be intensified by the premium cost of the technology.
In the absence of other pathology, the clinician should offer reassurance and allow the patient an adequate period of time for neuroadaptation to multifocal pseudophakic vision, continued Dr. Chang.
Residual refractive error should be carefully sought and treated as well.
"A trial with a contact lens or spectacles can differentiate uncorrected lower-order refractive error from higher-order optical aberrations," he added. "Certainly, spectacles or a contact lens should be tried before deciding to do laser vision enhancement."
Wavefront aberrometry can be used to diagnose corneal higher-order aberrations (HOA) that may be present. These can be subtle but are often present with basement membrane disease, marginal thinning, or prior corneal refractive surgery. In addition to measuring the total ocular HOA, some aberrometry systems (Tracey and Nidek OPD) can separately display and distinguish between corneal and lenticular HOA, Dr. Chang said.
"Clinically, we really need to understand whether any HOA are coming from the cornea or the lens," he said.
Other steps that should be taken before considering multifocal IOL explantation are to treat aggressively any ocular surface abnormalities such as dry eye. Subtle cystoid macular edema or maculopathy should be ruled out with optical coherence tomography. Laser pupilloplasty can be considered if the diffractive optic is poorly centered with the pupil.
If the multifocal IOL appears to be the primary source of visual complaints and the patient is contemplating explanation, Dr. Chang recommended first implanting a monofocal or accommodating IOL in the second eye to determine if halos or ghosting in the first eye become more tolerable. It is important to avoid YAG laser posterior capsulotomy if an IOL exchange might be necessary, he said.
A careful clinical history may help differentiate between a secondary membrane or the multifocal optic as the source of dissatisfaction. If the patient believes that postoperative vision was initially good but then became cloudy, this is consistent with the onset of progressive capsular opacity. That would not be true if the patient feels that vision was problematic starting immediately after surgery.