OCT screening needed before cataract surgery
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Examining the retina, particularly the macula, before cataract surgery is important to set appropriate patient expectations and aid in IOL selection.
With a beautiful cataract surgery, we only get a great picture if the macula is normal and healthy. With OCT, we can examine the macula in high resolution before cataract surgery. This is important because the cataract may not be the sole cause of visual impairment.
Source: Uday Devgan, MD
OCT makes it easy to identify subtle macular changes that may not be apparent when the fundus is examined clinically. Using the principle of optical interferometry, these devices acquire sharp, high-resolution views of the retina even when there is media opacity.
There are some important and relatively common retinal conditions that should be identified before planning phacoemulsification surgery. As a cataract surgeon, we need to screen for macular degeneration, epiretinal membranes, vitreomacular traction and more.
Macular degeneration
Consider the following case: Our patient arrives for preoperative evaluation with 20/80 best corrected vision that does not improve with pinhole. She has a visually significant cataract with moderate nuclear sclerosis and an unremarkable fundus exam with a somewhat hazy view of the retina. Cataract surgery is recommended, which she undergoes without complication. Postoperatively, she achieves 20/40 best corrected vision. At this point, careful macular exam shows subtle pigmentary changes and some drusen. When the OCT is taken, it shows a fibrovascular pigment epithelial detachment without retinal edema, which accounted for her suboptimal visual outcome.
Patients with macular degeneration, whether the dry or the wet form, can have an insidious course of disease without the classic presentation of metamorphopsia and blurry vision. Even dry macular degeneration can be associated with localized dysfunction of the retinal photoreceptors and can account for several lines of vision loss. Paracentral focal areas of atrophy can be difficult to discern in a blonde fundus. These changes can easily be overlooked, and the visual decline may be inappropriately attributed to the cataract. It may be beneficial to perform an OCT if there is any doubt of drusen or pigmentary changes or if the view from the cataract is sufficiently poor to preclude fine macular exam.
Epiretinal membrane
Epiretinal membrane (ERM) is a relatively common entity with an incidence of about 7% in the general population; it increases with age and may affect 20% of patients after the age of 70 years. It can be a subtle macular finding that is easily missed on routine exam. Again, this is a chronic disease that can account for mild to even severe vision loss. Patients can have asymmetric disease with one eye much worse than the other. ERMs can be associated with visual distortion, cystoid macular edema, reduced contrast sensitivity and even lamellar retinal holes.
Even if the ERM is deemed to be mild, these patients are at a higher risk for postoperative cystoid macular edema even if the cataract surgery itself is perfectly performed. These patients are also less than ideal candidates for a multifocal IOL or those using IOL modifications to increase the depth of focus. An acrylic monofocal IOL may be a wise choice in these patients, particularly if there is a chance that the patient will need a future pars plana vitrectomy.
In the above case, the patient was found to have 20/30 best corrected vision after cataract extraction with significant metamorphopsia, noting that straight lines like doorways looked crooked. She was subsequently referred to a retina specialist who performed vitrectomy and membrane peeling. Because ERM is a surgical disease, preoperative cataract planning should make provisions for staged surgical repair with a vitreoretinal surgeon.
Vitreomacular traction
The age range for development of posterior vitreous separation and cataract overlaps. A portion of these patients develop vitreomacular traction, which can be completely funduscopically occult. It is caused by a mismatch in timing between liquefaction of the vitreous jelly and separation of the vitreous face from the retina. Because cataract surgery itself can be associated with posterior vitreous detachment, it is important to identify this disease before taking your patient to the operating room. Remember, with cataract surgery, we are removing a cataract that is about 4 mm thick and replacing it with an IOL that is approximately 1 mm thin. This means that we can expect the vitreous to shift in the postop period. There are different ways to address vitreomacular traction, including vitrectomy and simply waiting for self-resolution, and patients can have an excellent visual outcome.
The strength of OCT testing is that while the above three diseases are subtle on clinical exam, they are all quite obvious on the OCT image. Your patient is going to benefit from cataract surgery, but it is important to set their postoperative expectations in light of these concurrent diseases. It is far better to refer patients for evaluation by a retina specialist before their cataract operation rather than rushing them to seek treatment secondarily. Remember the saying that if you detect a problem ahead of time, you are seen as brilliant for predicting it; however, if you only recognize the problem after it has occurred, you are likely to be blamed for causing it.
We routinely get an OCT image of the macula for all cataract preoperative patient consultations, noting that the majority of the time there is no pathology evident. The few times that we detect a macular condition that may limit the results of cataract surgery, it sends the message that it is definitely worth screening our patients.
For a video of this case, please visit https://cataractcoach.com/?s=OCT.
- For more information:
- Uday Devgan, MD, in private practice at Devgan Eye Surgery and a partner at Specialty Surgical Center in Beverly Hills, California, can be reached at devgan@gmail.com; website: www.CataractCoach.com.
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