Optical Coherence Tomography: Pearls for the Anterior Segment Surgeon

The advent of posterior segment optical coherence tomography (OCT) in the past decade has transformed the evaluation and diagnosis of retinal and optic nerve disease. OCT utilizes noncontact coherence interferometry to provide micrometerresolution images of the retinal pigment epithelium, retina, vitreoretinal interface, and nerve fiber layer. Crosssectional imaging permits detailed analysis, including the assessment of retinal and nerve fiber layer thickness. The ability to produce high-quality images in an efficient, reproducible manner makes OCT an invaluable tool not only for glaucoma and retina specialists, but also for the anterior segment surgeon in the diagnosis and management of optic nerve and posterior-pole disease.

INCORPORATING OCT INTO PRACTICE

Developing a better understanding and appreciation of how and when to utilize OCT in surgical practice will prevent potential pitfalls and sharpen one’s clinical acumen. I have found OCT valuable in the following settings:

• Preoperative cataract evaluation if the cataract does not appear consistent with the patient’s degree of visual loss;
• Preoperative cataract evaluation in the presence of retinal pathology;
• Preoperative cataract evaluation in premium IOL patients; and
• Postoperative evaluation to assess for cystoid macular edema (CME) or underlying retinal pathology.

If the degree of lens opacification does not appear consistent with the patient’s degree of visual loss, I routinely perform OCT testing. Often, this is the case in new patients who have been referred for cataract surgery. During initial evaluation, it is essential to establish the need for and potential benefit of cataract surgery. I have had numerous cases in which underlying, difficultto- visualize retinal pathology was the primary cause of visual loss. Detection of macular disease prior to cataract surgery can help avoid unnecessary surgery. Surgery in this setting may yield limited benefit, thereby resulting in poor patient confidence and patient dissatisfaction. Moreover, the diagnosis of retinal disease instills greater confidence in the patient and the referring doctor.

CASE STUDIES

The following cases highlight the essential role that OCT can play in detecting retinal pathology and avoiding unnecessary surgery.

Case No. 1. A 75-year-old patient was referred by an oculoplastics specialist for cataract surgery. The patient’s visual acuity was 20/25 in the right eye and 20/50 in the left. Both eyes had mild nuclear sclerosis, and a grade 1+ posterior subcapsular cataract was present in the left. The cataract did not appear consistent with the patient’s degree of visual loss. Subsequently, OCT demonstrated a lamellar hole with outer retinal edema (Figure 1). Surgery was deferred, and the patient was referred to a retina specialist for evaluation.

Case No. 2. A 70-year-old patient was referred for cataract surgery. The patient’s visual acuity was 20/30 in the right eye and 20/50 in the left. Both eyes had mild nuclear sclerosis and mild cortical changes. Similar to Case No. 1, the cataract did not appear consistent with the patient’s degree of visual loss. OCT was used to diagnose vitreomacular traction (Figure 2). Surgery was deferred, and the patient was referred to a retina specialist for evaluation.

Case No. 3. A 66-year-old patient was referred by an optometrist for a cataract consult. With correction, the patient’s vision was a slow 20/40 -1 in the right eye and 20/20 in the left. The patient had a mild cortical cataract and mild nuclear sclerosis in both eyes. The dilated exam appeared normal initially but was difficult to perform, as the patient was photophobic and uncooperative. OCT demonstrated elevation of the temporal retina (Figure 3), and funduscopic exam confirmed the presence of a shallow retinal detachment just approaching the fovea (Figure 4).

IN THE PRESENCE OF RETINAL PATHOLOGY

OCT can be useful to assess the degree of retinal pathology in an attempt to ascertain the potential benefit of cataract surgery. This can be helpful in patients with a number of macular diseases including epiretinal membrane and macular degeneration.

In this setting, OCT can be valuable in determining the benefit of cataract surgery alone as compared with the benefit of cataract surgery performed in conjunction with pars plana vitrectomy and membrane peel. For patients with cataracts and clinically significant epiretinal membranes, I perform the cataract surgery first, and a retina specialist then performs the vitrectomy and peel. We have found this combined technique to be effective and satisfying for patients, as they consider it to be only one procedure. Two case studies demonstrate favorable results of an individual and a combined procedure.

Case No. 1. A patient with a history of epiretinal membrane was referred for cataract surgery. OCT demonstrated good foveal contour with no significant thickening (Figure 5). She underwent cataract surgery and achieved a UCVA of 20/25.

Case No. 2. Another patient with a history of epiretinal membrane was referred for cataract surgery. OCT demonstrated marked thickening with loss of foveal contour (Figure 6). She underwent combined cataract surgery with vitrectomy and membrane peel.

PREMIUM IOL PATIENTS

Careful evaluation is crucial in potential multifocal IOL patients. Retinal pathology can lead to poor postoperative contrast sensitivity. A pristine macula is desired for the multifocal IOL patient, and OCT can help us to exclude subtle retinal pathology. Figure 7 demonstrates OCT findings in a patient who was motivated to undergo cataract surgery with multifocal IOL implantation. His clinical retinal exam appeared unremarkable. OCT, however, demonstrated the presence of a small, previously undiagnosed lamellar hole. After a discussion with the patient, a monofocal IOL was implanted.

OCT is a great tool in the postoperative period as well. I have a low threshold for checking for CME in this setting (Figure 8).

CONCLUSION

Overall, OCT is a great tool for the anterior segment surgeon. It is noninvasive, quick, and easy to interpret, and it plays a vital role in my surgical practice in both pre- and postoperative settings.

S. Akbar Hasan, MD, is an Assistant Professor of Ophthalmology at the Mayo Clinic, Department of Ophthalmology, Jacksonville, Florida. He may be reached at tel: +1 904 953 7110; fax: +1 904 953 7040; e-mail: jaxcornea@yahoo.com.