Retina issues could undo even best preparations

For optimized outcomes during cataract operations, check the posterior segment before surgery.

By Logan Brooks, MD, and Andrew D. Hsia, MD

It’s been said that happiness equals outcome minus expectation, and this is certainly true with cataract and retina patients. On occasion, post-cataract surgery patients present to our retina service with unmet visual expectations, and they are surprised to learn that they have macular degeneration or a macular hole. In such patients, a thorough exam and discussion before surgery about their limited visual outcome could have spared a much longer postsurgery talk about why their vision had not improved to their satisfaction.

The posterior segment evaluation of a cataract patient should start with a dilated careful examination of the macula and periphery. If the degree of vision loss does not correlate with the degree of cataract, an OCT should be performed and the patient may need to be referred to a retina specialist. Subtle findings, such as vitreomacular traction or macular thinning from ischemia may be missed without an OCT. The following are common retinal conditions that can affect visual outcome and should be addressed prior to cataract surgery.

Figure 1. OCT of choroidal neovascularization in wet AMD.

Macular degeneration

Cataract surgery improves vision and does not worsen neovascular AMD or increase the need for more anti-VEGF injections.¹ Neovascular AMD patients may not need several injections prior to their cataract surgery. In one study, treatment-naïve, wet AMD patients who were given intravitreal bevacizumab (Avastin, Genentech) at the time of cataract surgery showed significant improvement, suggesting control of the exudative process might not be necessary before cataract surgery.² Also, cataract surgery does not increase the risk of conversion from dry to wet AMD.³

For both wet and dry AMD patients, cataract surgery improves vision even if they have a central scotoma. These patients may note improved peripheral and color vision and “more light” entering their eyes. A monofocal or toric IOL is preferable for advanced AMD patients. Patients with severe central scotomas from AMD may be candidates for the Implantable Miniature Telescope (Vision Care Ophthalmic Technologies, Inc. ).

Macular edema

For patients with diabetic macular edema (DME), vision improved after cataract surgery.⁴ Those with diabetes have a four-times higher risk of developing macular edema after cataract surgery compared to those without the disease. Furthermore, the extent of DME exacerbated by cataract surgery correlates to the degree of diabetic retinopathy.⁵ Several studies have shown that intravitreal anti-VEGF given at the time of cataract surgery improves visual outcomes and lowers the chance of macular edema. Similarly, intravitreal dexamethasone implant (Ozurdex, Allergan) for DME or branch retinal vein occlusion given at the time of cataract surgery improves macular edema and vision.⁶

Similarly, eyes with vein occlusion are at increased risk of cystoid macular edema after cataract surgery.⁷ Because VEGF levels rise after cataract surgery, both types of macular edema should be treated and stabilized prior to surgery. Once stable, a physician can inject an intravitreal anti-VEGF or steroid to reduce postoperative macular edema. This can be done either at the time of cataract surgery or one to two weeks prior.

Postoperative Irvine-Gass syndrome, or pseudophakic cystoid macular edema, usually occurs four weeks after cataract surgery and is commonly treated with topical NSAIDs and steroid. If the syndrome persists after topical therapy, consider employing sub-Tenon’s Kenalog or intravitreal steroid (triamcinolone or dexamethasone or fluocinolone implants).

Mature cataract

An ultrasound should be performed on eyes with mature cataract or hazy cornea precluding a clear view of the retina. As many as 20% of eyes with mature cataracts have posterior segment abnormalities such as posterior staphyloma, retinal detachment or vitreous hemorrhage. In patients younger than 50 years of age, with diabetes, or with a history of trauma, there is a higher incidence of retinal pathology. If there is a question of an intraocular foreign body, both an ultrasound and a CT scan of the orbit should be performed.

Myopia and the retina

Cataract surgery is especially rewarding for patients with myopic eyes because surgeons can correct the refractive error in a single operation. However, cataract surgery in high myopes requires careful preparation due to their higher incidence of retinal pathology. Anisometropia is more common in high myopes because of co-existing posterior staphyloma. Preoperative axial length measurements should be measured with an optical method, because ultrasound is not precise enough to measure the distance to the fovea in the presence of posterior staphyloma. Refer patients with highly myopic eyes to a retinal specialist to evaluate for myopic macular degeneration, foveoschisis or other macular pathology that could limit vision improvement despite optimal cataract surgery. During cataract surgery, the anterior chamber depth may fluctuate greatly. If the anterior chamber collapses suddenly, traction on the vitreous base occurs, which can lead to retinal tear and detachment, so plenty of viscoelastic is recommended.

Figure 2. Retinal thinning from BRAO.

Retinal detachment risk

A peripheral retinal exam involving dilation is mandatory before cataract surgery. High-risk patients include high myopes and those with a history of retinal tears or detachment. Refer these patients to a retinal specialist for a peripheral scleral depressed exam. Retinal tears should be treated, whereas retinal holes and lattice can be observed depending on the presence of other risk factors.⁸ The risk of retinal detachment after cataract surgery is 1%, and after 10 years the risk is 5.5 times higher than someone not undergoing cataract surgery.⁹

Figure 3. Emulsified silicone oil bubbles on IOL.

Figure 4. Vitreomacular traction and macular hole.

In patients with a history of retinal detachment or tear, a monofocal acrylic IOL is preferred over a silicone IOL because it could require silicone oil for retinal detachment repair, which can coat the back surface of a silicone IOL.

Vitreous debris and opacities

Cataract surgery could accelerate the posterior vitreous detachment process, or “unmask” floaters in some patients. Patients with significant vitreous debris and bothersome floaters might be candidates for vitrectomy after cataract surgery. We do not recommend YAG vitreolysis for vitreous debris, as it is unproven and the risk is unnecessary.

Some of the most satisfied retinal patients are those who are finally cured of their floaters after a vitrectomy.

VMT, macular hole and ERM

The use of spectral domain OCT is imperative to rule out small macular holes or edema secondary to vitreomacular traction or epiretinal membrane (ERM).

When cataract surgery accelerates the PVD process, it may cause vitreomacular traction (VMT) to worsen or even progress to macular hole. Cataract surgery carries a five-fold increased risk of postoperative macular edema in eyes with ERM.⁵ The timing of cataract surgery before or after vitrectomy for these conditions remains debatable.

Generally, we perform vitrectomy for VMT, macular hole and ERM prior to cataract surgery, unless the cataract precludes a good view of the macula. OM

REFERENCES

About the Authors
	Logan Brooks, MD, is founder and president of Southern Vitreoretinal Associates. He is a pioneer of internal limiting membrane surgery for macular holes. He is a member of the Retina Society and currently the vice president of U.S. Retina.
	Andrew D. Hsia, MD, is an associate at Southern Vitreoretinal Associates, and practices in Warner Robins and Albany, Ga. E-mail him at drewhsia@gmail.com.