Previously, we discussed some general principles when considering cataract surgery in patients with retinal disease.
This month, we provide some practical ideas for those with common specific retinal problems.
Vitrectomy is occasionally performed as a stand-alone procedure, for example, as treatment for proliferative vitreoretinopathy. More commonly, vitrectomy is a step in a more complex retinal surgery, such as a retinal detachment repair or epiretinal membrane peel. No matter the reason, dense nuclear sclerosis (NS) usually begins within weeks of vitrectomy in the phakic patient. While the Vitrectomy for Macular Hole Study showed that about 80% of patients undergoing vitrectomy developed enough nuclear sclerosis within 6 months to require cataract surgery, other studies as well as personal experience indicate that nearly all vitrectomy patients eventually develop visually significant cataract (Feng et al.).
The exact reason why this happens is not completely understood. Some have suggested mechanical trauma. But the most likely explanation is that the oxygen concentration around the lens substantially increases after the removal of the vitreous, which in turn leads to cataract formation. No matter the reason, the dense central NS often results in rapid myopic progression with poor corrected visual acuity when compared with senile NS. The bottom line is that it’s rare for patients to visually tolerate even early post-vitrectomy cataracts, so the cataract is nearly always removed.
Cataract surgery in these patients have three specific risks or uncertainties.
First, vitrectomy causes the loss or weakening of zonules, which, in turn, leads to increased risk of capsular tear and IOL dislocation. Second, the replacement of the firmer vitreous gel with aqueous increases the intraoperative fluctuations during phacoemulsification, which increases the risk of lens fragments. Finally, the prior removal of the more resistant vitreous often leads to a more posterior IOL position and a hyperopic refractive surprise. While many IOL power calculators have the ability to take this latter uncertainty into account, some of us will still target a small amount more myopic than our hoped-for outcome, around -0.50 D or -0.75 D or so.
To summarize, in addition to a hyperopic refractive surprise, be particularly alert for IOL dislocation and lens fragments. These often dense cataracts can mean greater phaco energy is necessary, which also increases these risks along with greater postop inflammation.
Patients with prior retinal detachment repair have cataract surgery risks similar to those who have had vitrectomy, and for good reason: Vitrectomy is nearly always performed as part of retinal detachment repair. Those with a scleral buckle have a couple of specific considerations.
The increased axial length from the buckle increases the uncertainty of the IOL calculation and the risk of globe perforation if an injectable anesthetic is used, so careful and accurate biometry is necessary.
A preoperative macular OCT is mandatory in any patient with a history of wet age-related macular degeneration. These patients are at significant risk for macular edema after cataract surgery, so we like to see at least some response if not resolution of any cystoid macular edema (CME) or subretinal fluid from intravitreal injection treatment prior to scheduling cataract treatment.
The timing of cataract surgery in between intravitreal treatments should be coordinated with the treating retina specialist. As an aside, there is no strong evidence to suggest that cataract surgery either causes or worsens wet AMD.
There was a time when those with severe vision loss from dry AMD were discouraged from having cataract surgery at all. Not any longer. We frequently see significant improvement in mobility from treating both the glare as well as the quality of peripheral vision, even if the central visual acuity remains the same. So, take these on a case-by-case basis.