BLOG: Suggestions for retina patients undergoing cataract surgery
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.
Perhaps no macular conditions vex those of us in cataract surgery practice as much as epiretinal membranes (ERMs) and vitreomacular traction (VMT). First, ERMs are very common and frequently have little or no impact on visual acuity. However, even early ERMs can cause some minimal metamorphopsia and a subjective difference in vision between each eye. Potential vision testing such as a superpinhole is helpful; even when potential acuity tests good, we caution patients that it’s possible that their vision will not be as good as they hoped because of the ERM. Some forms of potential vision testing can, for reasons that aren’t exactly clear, overestimate postcataract surgery best chart acuity.
Identify the main complaint carefully. Cataract surgery can improve glare but rarely distortion, the latter an indication that the ERM or VMT is the main reason for their visual problem. Finally, patients with ERM have up to five times greater risk for postop CME and are at particular risk of chronic CME, the form that can result in permanent vision loss.
It’s standard of care to include nonsteroidal eye drops, such as bromfenac or ketorolac, as prophylaxis against postop CME in patients with ERM or vitreoretinal adhesion or traction. In fact, it’s a good idea to include NSAID prophylaxis in any patient with retinal conditions that pose higher risk for CME, including prior branch vein occlusion and central retinal vein occlusion.
As an aside, intravitreal steroids, a common treatment for macular edema from retinal vein occlusion, is a significant cause of a rapidly-forming cataract.
Perhaps our most common at-risk patients are those with a history of diabetic retinopathy. Any diabetic macular edema (DME) should be adequately treated prior to cataract surgery, usually with intravitreal anti-VEGF or steroids. Those with proliferative disease, particularly if extensive, deserve particular caution. They are at risk of postop vitreous hemorrhage as well as tractional retinal detachment, so adequate treatment with panretinal photocoagulation should be performed ahead of time.
So, what’s a good schedule of NSAID prophylaxis for CME? The specifics can vary, but most of us recommend at a minimum an NSAID drop four times a day postoperatively for a month. Some suggest starting the NSAID for a week prior to surgery, some continue treatment for longer than a month in particularly high risk diseases. While no real recipe exists, one suggested schedule is the following:
--For patients at low risk (mild ERM, early to moderate nonproliferative diabetic retinopathy without history of DME): Begin 1 drop four times per day of NSAID 1 week prior to cataract surgery. Continue four times per day for 4 weeks.
--For patients at high risk (previous macular edema from diabetic retinopathy or retinal vein occlusion): Same starting time and dosing schedule as the low risk group, but continue for 8 weeks postop.
Risk of postop detachment
Finally, we consider those with increased risk for retinal detachment following cataract surgery, a rare complication by any measure, yet some patients deserve extra caution. Who is at greatest risk? Men younger than 50 years with longer axial lengths. Still, we don’t have preoperative retinal consults on this group unless they have some other identifiable clinical finding that clearly increases the risk.
Not all types of retinal breaks are risk factors for retinal detachment in the phakic patient. Still, any break, even atrophic holes, should be evaluated and probably treated with laser photocoagulation by a retina specialist before cataract surgery.
We know that high myopia is a risk factor for retinal detachment in both the phakic and pseudophakic patient. But the patient with an abnormally short eye – particularly anyone with features of microphthalmia – should get a retinal specialist evaluation as well.
What about lattice degeneration? The truth is that most of our patients with lattice do not get retinal consults prior to surgery unless it is extensive or has features of concern, such as adjacent holes.
While wide-field photography is a great tool for detecting most peripheral retinal conditions, it does have its limitations. Some of the retina just can’t be seen. We always perform a clinical exam with the indirect ophthalmoscope preoperatively in our patients at higher risk for pseudophakic retinal detachment. The ability to see things dynamically – adjusting the spot size, placing the edge of the light across an area of interest, indirect illumination and scleral depression – simply reveals more information than does a static photograph.
Feng H, et al. Clin Ophthalmol. 2014;doi:10.2147/OPTH.S68661vv.