HThe decision whether to perform concurrent cataract and vitreoretinal surgery depends upon several factors, including the amount of operative stress the eye can endure and whether the cataract impedes visualization during a vitreoretinal procedure. This article shares my viewpoint on the timing of cataract surgery for eyes with a variety of vitreoretinal problems.

THE DIABETIC EYE

Background
I am a cautious surgeon and especially conservative in my approach to diabetic eyes. I often feel that these eyes can only tolerate a limited amount of surgery at one time. Ocular blood flow, which diabetes impairs, is exceptionally important in these eyes.1 Patients with diabetes frequently have incompetent capillaries in the macula, and they have a high propensity for developing macular edema after undergoing cataract surgery (Figure 1). The cataract procedure alone may stress an eye with compromised circulation. Combining cataract extraction with vitrectomy and perhaps injection of silicone oil may impair borderline functioning capillaries. Moreover, after cataract removal and the vitrectomy procedure, inflammation in the capillaries may cause increased macular edema that will impede the restoration of vision.

Timing
Fortunately, diabetic patients rarely require an emergent vitrectomy. They normally suffer traction detachments, rather than rhegmatogenous detachments caused by retinal holes. A traction detachment that occurs in the periphery may be observed and does not always necessitate a vitrectomy.

Nevertheless, complications during vitreoretinal surgery occur because of visualization problems. For that reason, if one of my patients has a dense cataract that will compromise my intraoperative visualization, I will ask the cataract surgeon to remove the lens. If possible, I will then allow the eye to quiet for 6 to 8 weeks before performing the vitrectomy.

A diabetic vitreous hemorrhage usually requires treatment. In such a case, I may only be able to wait a few weeks before performing the vitrectomy, but this period of time still allows some stabilization of the blood-ocular barrier. Cataract surgery and the vitrectomy must be combined when the patient has a visually significant cataract and either a rhegmatogenous retinal detachment or a traction detachment involving the macula. A combined procedure is also necessary in cases of severe cataract coupled with uveitis that requires vitrectomy and for sick patients who may need to undergo all surgeries at one time due to anesthesia risks. In these situations, I prefer that the cataract surgeon extract the lens but wait to implant the IOL until I have completed the vitrectomy.2 A scleral tunnel has a theoretical advantage in such cases owing to self-sealing wound construction and a lesser degree of induced astigmatism during the subsequent procedure. If the surgeon implants the lens immediately following cataract extraction, my view may be distorted by the edges of the IOL or fogging may occur while I perform peripheral laser treatment. In young diabetics, extracting the crystalline lens is frequently unnecessary at the time of vitrectomy. If their eyes require an injection of silicone oil, sometimes a contact lens will provide functional visual acuity through the altered media (usually approximately +5.00 D of hyperopia) until the silicone can be removed.

Approach
Many vitreoretinal surgeons prefer to perform pars plana lensectomies (PPLs). The goal is to leave the anterior capsule undisturbed for later lens placement, which is achievable most of the time. In eyes with a visually significant cataract and a diabetic traction detachment involving the macula and associated with severe proliferative diabetic retinopathy, I personally prefer that the cataract surgeon perform phacoemulsification and insert the IOL via an anterior approach, even if the procedures are combined. An advantage of the anterior approach for cataract extraction is that competent cataract surgeons do not allow lens fragments to enter the posterior segment, as can occur during a PPL. If any fragments do drop into the vitreous, however, vitrectomy follows immediately. This approach results in nicely rounded pupils, fewer posterior synechiae, and excellent in-the-bag placement of posterior-chamber IOLs.

Lens Choice
I advocate the placement of IOLs that are 6 mm or larger in diameter, because smaller lenses can impair retinal visualization. If I dilate the pupil and attempt to perform a vitrectomy or laser treatment around a 5.5-mm lens, it is easy to visually catch the edge of the IOL and experience distortion, which makes surgery more difficult. I also prefer that cataract surgeons implant foldable acrylic lenses, because silicone oil adheres to silicone IOLs.3 PMMA lenses cannot be folded and therefore do not allow the advantages of small-incision cataract surgery, both of which negate the advantage of an anterior approach.

A PPL still requires an anteriorly inserted IOL. For that reason, why not perform phacoemulsification anteriorly and place a small-incision IOL? The amount of surgery is probably equivalent, and an anterior approach positions the lens in the bag away from the iris. Postoperative inflammation occurs frequently in diabetic eyes, and sulcus-fixated lenses may promote synechiae.

Silicone Oil
My frequent use of silicone oil in diabetic eyes is a major component of my argument for separate cataract and vitreoretinal procedures in diabetic patients. I have had patients with silicone oil in place who developed cataracts, and I have found that IOL measurements performed in the presence of silicone oil tend to be less accurate. If a cataract is removed and the IOL measurement and placement are completed prior to the injection of silicone oil, the patient will have a correctly powered IOL already in place when the oil is subsequently removed. It is important, when using silicone oil, to have an anatomical separation between the anterior and posterior segments, such as the crystalline lens or the pseudophakic posterior capsule provides. I feel that zonular disruption may be less extensive with well-performed phacoemulsification from the anterior approach than with a PPL, which will likely disrupt the zonules.

MACULAR HOLE
The movement within the vitreoretinal field is to visually rehabilitate macular hole patients quickly, and most surgeons perform PPLs and vitrectomy simultaneously for that reason. In these cases, I prefer that the cataract surgeon remove the crystalline lens and implant an IOL before I operate. Unlike with diabetic eyes, the presence of an IOL does not hinder my surgical efforts because there is no peripheral pathology I must treat. In these cases, a lens diameter of 5.5 mm or larger will not affect peeling the posterior hyaloid membrane, removing the internal limiting membrane, and placing perfluorocarbon gas.

TRAUMA
Restoring the structural integrity of these eyes is the most important aim, and it may or may not involve extracting the crystalline lens. As with diabetics, these eyes have sustained a great deal of damage, so I feel it is advisable to perform as little surgery as possible during the eye's recovery, provided the retina is not detached, which would necessitate immediate intervention. Injury releases many inflammatory mediators, and both the trauma and the ensuing surgeries are wounds to the eye. If the lens must be extracted, I will remove it, but I stage my subsequent repairs based upon the pathology and attempt to perform as few procedures as possible at one time.

RETINAL DETACHMENT
For a retinal detachment (RD) in the presence of a dense cataract, many vitreoretinal surgeons will perform a PPL in order to improve their visualization. Then, they perform a pars plana vitrectomy (PPV) as a primary detachment repair combined with the placement of silicone oil, air, and/or a scleral buckle. RDs often have an associated vitreous hemorrhage that may complicate visualization of the pathology. Many retinal surgeons believe that an RD with a cataract and vitreous hemorrhage is an indication for combined PPL, PPV, and intravitreal tamponade. The issue is one of urgency. An RD with the macula still attached is fairly urgent. With a diabetic eye, the situation is usually less pressing, so the cataract and vitreoretinal procedures may be separated.

RETINAL TEARS
Giant retinal tears frequently necessitate a PPL and PPV with silicone oil as initial management, and the decision is based upon the individual vitreoretinal surgeon's preference. I still prefer to remove the lens with phacoemulsification and implant an IOL anteriorly instead of performing a PPL and then opening the front of the eye in order to insert the IOL and place it on the shelf. Because an anterior approach is ultimately necessary for IOL placement, why not perform all surgery from there?

CONCLUSION
In the days of large-incision cataract surgery with single-piece PMMA IOLs, a combined PPV and PPL (posterior approach) helped to reduce the wound size, decrease complications from anterior segment wound leakage during PPV, and promote healing. Today, there may be no difference in the healing response with small-incision phacoemulsification and foldable IOL placement (from anteriorly) compared with a PPL, because the surgeon still must insert the IOL through an anterior incision. The different approaches depend on surgeon preference and visualization to prevent complications.

Timing is also the individual surgeon's choice. If possible, I prefer to stage the cataract and vitrectomy procedures in diabetic and traumatized eyes due to the amount of inflammation that multiple, simultaneous procedures at one time incite. Dexamethasone in the infusion fluid is a remarkable advantage in these inflamed eyes.

Mandi D. Conway, MD, is Clinical Professor of Vitreoretinal Surgery and Uveitis for the Department of Ophthalmology at Tulane University in New Orleans. She does not hold a financial interest in any product or company mentioned herein. Dr. Conway may be reached at (504) 988-1122; mconway1@tulane.edu.
1. Krepler K, Polska E, Wedrich A, Schmetterer L. Ocular blood flow parameters after pars plana vitrectomy in patients with diabetic retinopathy. Retina. 2003;23:192-196.
2. Soheilian M, Ahmadieh H, Afghan MH, et al. Posterior segment triple surgery in traumatic eye injuries. Ophthalmic Surg. 1995;26:338-342.
3. Apple DJ, Isaacs R. Silicone oil and silicone lenses: awareness, not condemnation. Eye World. April 1997.