Extended dosing regimen for AMD treatment may spur increased use of OCT

Michael S. Ip

Posterior segment imaging and diagnostic technologies, in conjunction with improved pharmacologic management protocols, promise to improve clinical outcomes and mitigate vision loss from retinal disease.

Traditional imaging modalities such as fundus photography and fluorescein angiography continue to be firmly entrenched in the retinal specialist’s armamentarium. However, spectral domain optical coherence tomography (SD-OCT) enables specialists to visualize obscure retinal pathologies in vivid detail.

SD-OCT is useful as a primary or secondary imaging method for a variety of retinal diseases and glaucoma.

Michael S. Ip, MD, said that results of the Comparison of Age-Related Macular Degeneration Treatment Trials (CATT) may spur increased use of OCT in evaluating patients with AMD.

The National Eye Institute initiated CATT in 2008 to compare Avastin (bevacizumab, Genentech) and Lucentis (ranibizumab, Genentech) for AMD treatment.

Visual acuity results for either bevacizumab or ranibizumab administered monthly or as needed were within a one-letter difference on an eye chart, according to a news release from the NEI.

Dr. Ip characterized the longer dosing regimen as an opportunity to use OCT more frequently to track AMD progression between doses.

“I think the results of the CATT trial will result in even more OCT being used in ophthalmology clinics,” Dr. Ip said in a telephone interview. “I get an OCT now on almost every follow-up visit unless I know I’m just going to inject the patient.”

Seenu M. Hariprasad, MD, said OCT is useful in managing AMD with extended dosing protocols.

“The ability of SD-OCT to detect subtle intraretinal or subretinal fluid has really helped in the management of exudative AMD using treat and extend dosing regimens,” Dr. Hariprasad said in an email interview. “We are able to characterize better now than ever in the past subtle vitreoretinal macular disorders that are responsible for vision loss and better plan our approaches to these problems.”

Baseline AMD assessment

In treating AMD, Dr. Ip said he takes a fundus photograph at baseline, documents the exudative nature of AMD and uses fluorescein angiography to confirm the presence of neovascularization.

“In most cases, it’s fairly obvious, clinically, just from your examination and from your photographs,” Dr. Ip said. “Sometimes it’s not so obvious, and you might have a very subtle case and you can detect choroidal neovascularization on angiography when you really couldn’t detect it clinically. Sometimes, fluorescein angiography can still be very useful. So, I will just about always obtain a fluorescein at baseline.”

Dr. Ip said he performs SD-OCT as an ancillary test after initiating pharmacotherapy.

“I don’t get a fundus photograph unless there’s a significant morphologic change such as blood resorbing significantly,” he said. “Then, I might use that as a patient education tool to show them that the blood is going away. But, by and large, OCT remains the mainstay ancillary test.”

Dr. Hariprasad said he favors fluorescein angiography and SD-OCT when evaluating patients with AMD.

Drs. Ip and Hariprasad use the Cirrus spectral-domain OCT (SD-OCT, Carl Zeiss Meditec). Dr. Ip has also used Stratus time-domain OCT (TD-OCT, Zeiss), Topcon’s OCT platform and Spectralis SD-OCT (Heidelberg Engineering).

Diabetic retinopathy and RVO

Dr. Ip said he prefers fundus photography in evaluating diabetic retinopathy at baseline. He said he uses fluorescein angiography in cases where there is a component such as ischemia that may result in vision loss.

“You really can’t determine the level of ischemia or non-profusion. You have to go to the angiogram. So, the angiogram still remains a useful test in our diabetic macular edema patients,” Dr. Ip said.

Seenu M. Hariprasad

Dr. Hariprasad said he uses widefield angiography (Optos) in evaluating proliferative diabetic retinopathy.

In evaluating retinal venous occlusive disease, Dr. Ip said he favors fundus photography at baseline to gauge the degree of morphology, such as hemorrhage, disc swelling and venous engorgement.

OCT is useful in identifying obscure artifacts that may be missed on fundus photographs, Dr. Ip said.

“I think it’s extremely useful to use OCT to determine whether or not there’s retinal thickening or subretinal fluid that can’t be detected clinically. If there is, I think that a zero tolerance for subretinal fluid or retinal thickening in a patient who has responded before to anti-VEGF is probably the right thing to do,” he said. “OCT remains a highly useful tool for retinal venous occlusive disease.”

Dr. Hariprasad said he prefers widefield angiography for assessment of BRVO or CRVO. However, he prefers SD-OCT in cases involving macular edema associated with RVO.

Further improvements to OCT

Future improvements to OCT will likely include increased resolution and speed, Dr. Ip said.

“Improving resolution can help us detect subretinal fluid, retinal thickening or other changes on the OCT with more accuracy,” he said. “We’re truly going to have a zero tolerance for subretinal fluid and retinal thickening. The better the resolution, the better we’re going to be able to determine when to re-treat a patient with pharmacotherapy.”

Portable OCTs would significantly benefit some patients, Dr. Ip said.

“It would be very helpful in clinical terms. For example, you could take an OCT unit to a patient who is hospitalized at the bedside, who may benefit from having an OCT scan,” he said.

Dr. Hariprasad envisioned platforms combining focal laser technologies with en face OCT.

“This would allow precise localization of areas in the macula that need laser treatment and the ability to quantify the degree of macular edema and response to treatment,” he said. “Fluorescein angiography currently helps us with the iris. However, it does not quantify the degree of macular edema.” – by Matt Hasson

• Seenu M. Hariprasad, MD, can be reached at Department of Ophthalmology and Visual Science, University of Chicago, 5841 South Maryland Ave., MC 2114, Chicago, IL 60637; 773-702-3937; email: retina@uchicago.edu.
• Michael S. Ip, MD, can be reached at University of Wisconsin, Fundus Photograph Reading Center, Park West One, 406 Science Drive, Suite 400, Madison, WI 53711; 608-263-2853; email: msip@wisc.edu.
• Disclosures: Dr. Hariprasad is a consultant for Alcon, Allergan, Bayer, Genentech, OD-OS, Optos and Regeneron. Dr. Ip has a research relationship with Allergan and is a consultant for EyeTech, Genentech, NicOx, QLT and Sirion.

Daniel F. Kiernan

SD-OCT technology allows a greater depth of scan and resolution of retinal details. Since subtle areas of intra- or subretinal fluid may be detected with this technology, it may help guide the as-needed or treat-and-extend treatment of AMD, myopic choroidal neovascularization and certain other retinal conditions. The 1 year CATT data suggest that as-needed treatment may be non-inferior to monthly injections for patients with neovascular AMD, which has important economic considerations given the high costs of health care. However, retinal vascular pathologies such as branch and central retinal vein occlusions may have impressive decreases in macular thickness following individual treatments, yet can develop rebound edema with loss of visual function if treatment is deferred solely based on OCT findings of a fluid-free macula. Therefore, eye physicians should carefully review the relevant studies for their patients’ conditions and take long-term data, especially that involving as-needed or treat-and-extend dosing into account when considering whether an intravitreal injection is appropriate. Consultation with a retinal specialist is highly advisable if there is concern about whether or not to treat with an intravitreal injection. However, retinal specialists should not use OCT alone to guide treatment and realize that OCT imaging data are not directly comparable between different macular diseases.

– Daniel F. Kiernan, MD
Illinois Eye and Ear Infirmary, University of Illinois at Chicago
Disclosure: Dr. Kiernan has no relevant financial disclosures.

Detection of RNFL defects

A recent study showed that speckle-noise-reduced SD-OCT, or enhanced SD-OCT, improved the detection of retinal nerve fiber layer (RNFL) defects in glaucoma. Results were published in Ophthalmology.

The retrospective case series included 44 eyes of 44 patients with open-angle glaucoma and localized, wedge-shaped RNFL defects. A control group comprised 35 eyes of 35 healthy subjects.

Enhanced SD-OCT images were captured with Spectralis + HRA. Single-scan images were taken with the RTVue SD-OCT (Optovue) and TD-OCT (Stratus, Carl Zeiss Meditec).

Results showed that 65 RNFL defects were identified on red-free fundus photographs. The circumpapillary RNFL boundaries were clearer on enhanced SD-OCT than on single-scan SD-OCT or TD-OCT. Enhanced SD-OCT was more sensitive in detecting RNFL defects that were not disrupted than were single-scan TD-OCT and SD-OCT. The differences were statistically significant (both P < .0001).

Enhanced SD-OCT was shown to be markedly more sensitive and specific than single-scan TD-OCT or SD-OCT in detecting glaucoma, the authors reported.

Reference:

• Nukada M, Hangai M, Mori S, et al. Detection of localized retinal nerve fiber layer defects in glaucoma using enhanced spectral-domain optical coherence tomography. Ophthalmology. 2011;118(6):1038-1048.