Keys to avoiding corneal edema after cataract surgery
Postoperative visual clarity and patient satisfaction depend on corneal clarity.
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There is a “wow” effect from refractive cataract surgery because we can eliminate the lens opacity and address the astigmatism and spherical correction of the eye at the same sitting. This large improvement in vision is amazing, and as surgeons, we all know the joy of happy postoperative patients. However, the visual clarity after surgery depends on the corneal clarity, and any postop stromal edema will result in blurred vision during the initial healing period.
There are key steps to avoiding corneal edema after cataract surgery, which are well known by experienced surgeons. The general principle is to perform a gentler, less invasive and more efficient surgery, while returning the eye to its homeostasis balance by minimizing inflammation and pressure rises. These subtleties may not be as obvious to younger or beginning surgeons, so it is worth reviewing them in detail.
Ophthalmic viscosurgical devices (OVDs) revolutionized cataract surgery many decades ago. These viscoelastic substances allow us to coat and protect the delicate corneal endothelial cells during phacoemulsification. When instilling the dispersive OVD, care must be taken to deliver a wave of viscoelastic as opposed to strings, which will not effectively coat the endothelium (Figure 1). The choice of OVD is also important because a dispersive OVD, which typically has the word “coat” in the name, will tend to stay in position and actually coats the tissues. The cohesive OVDs do not have this same coating ability, and they will not provide as much corneal endothelial protection.
Source: Uday Devgan, MD
The incision for cataract surgery is important because it determines the position of the phaco probe during surgery. The architecture and construction of this phaco incision also determine how easily it will seal. We want an incision that barely nicks the limbal vessels and then provides a good tunnel length (Figure 2). The architecture of the incision should allow for balance between the roof and floor of the incision. And at the end of the case, a great incision will seal well without the need for extensive stromal hydration.
When performing hydrodissection, a significant amount of the viscoelastic will egress from the phaco incision because it is being displaced by the injected balanced salt solution. Just before placing the phaco probe in the eye, we can recoat the corneal endothelium with an additional bolus of dispersive OVD (Figure 3). This will help to protect the central corneal zone, which is most critical for excellent postoperative vision.
Many studies have shown that the amount of ultrasonic phaco energy placed in the eye will, in large part, determine the damage to the delicate corneal endothelial cells. The amount of fluid flowing through the anterior segment also contributes to this because it can wash away the protective viscoelastic. To minimize the phaco energy, we can use a mechanical way to disassemble the nucleus such as the chop technique (Figure 4). We can also operate within the capsular bag, which is farthest away from the corneal endothelium. Employing phaco power modulations and being easy on the foot pedal can help to further minimize the total ultrasonic energy delivered, and that means a clear cornea in the immediate postoperative period.
Residual viscoelastic that is left in the eye can cause a spike in IOP. This high IOP will lead to corneal edema until it is lowered back to a normal physiologic level. The two main sources of retained OVD are behind the IOL optic and in the angle of the eye. Using the sweep method can help remove OVD from the angle, and then advancing the irrigation/aspiration tip to the area behind the IOL optic will allow complete OVD removal (Figure 5). If OVD is left in the eye at the end of the case, using topical pressure-lowering medications can be helpful to blunt the IOP spike in the postoperative period.
With a well-constructed incision, only a mild degree of corneal stroma hydration is needed to seal the incision. This is administered by placing a blunt 27-gauge cannula in the mid-stroma of the cornea and hydrating while moving laterally along the entire width of the incision (Figure 6). This will allow complete sealing of the incision without inducing a significant degree of corneal astigmatism. The older technique of inducing large areas of white stromal hydration at the lateral walls of the incision is not as effective and may actually induce corneal distortion and astigmatism, which will limit the postoperative vision. In addition, this older technique may not achieve adequate sealing at the center of the incision.
These six keys can help surgeons achieve clear corneas and better vision for cataract surgery patients in the proximate postoperative period. It is the difference between before and after vision that amazes our patients, especially if we can deliver this great vision immediately. And that makes seeing patients on postop day 1 so much more fun.
Full video of this case is available at CataractCoach.com.
- For more information:
- Uday Devgan, MD, is in private practice at Devgan Eye Surgery, Chief of Ophthalmology at Olive View UCLA Medical Center and Clinical Professor of Ophthalmology at the Jules Stein Eye Institute, UCLA School of Medicine. He can be reached at 11600 Wilshire Blvd. #200, Los Angeles, CA 90025; email: devgan@gmail.com; website: www.CataractCoach.com.
Disclosure: Devgan reports he owns CataractCoach.com, which is a free teaching website.
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