Intraoperative anterior segment OCT provides surgeons with heightened resolution of the structure of the eye and cross-sectional images of the anterior segment to provide extra detail during cataract and complex corneal surgeries.
The enhanced visualization offered with anterior segment OCT gives surgeons a new dimension in surgical planning, Julie M. Schallhorn, MD, told Ocular Surgery News.
“Normally during surgery, we are used to looking from a top-down view with broad light illumination. OCT provides a cross-sectional image that you can see much more easily the depth and configuration of what is happening in the cornea or anterior chamber during surgery,” Schallhorn said.
Anterior segment OCT is similar to having a slit lamp-type view during surgery, which can be “enormously helpful” during cataract and complex corneal surgeries, Schallhorn said. Surgeons can clearly resolve all layers of the cornea.
The imaging technology is helpful for all lamellar keratoplasty procedures and cataracts in patients who have corneal opacities because it can provide better views than visible broad-beam light.
“In the future, as our digital image processing capabilities progress, I imagine OCT will be able to provide real-time depth and guidance information,” Schallhorn said.
The imaging technology provides “unparalleled resolution” to the structure of the eye, which can improve precision during surgery. Surgeons can visualize the delicate tissues of the eye, from discerning the configuration of a scroll in Descemet’s membrane endothelial keratoplasty to seeing the fine fibrous strands in the anterior chamber, she said.
Pachymetry and epithelium mapping are capabilities of preoperative anterior OCT imaging that can augment the intraoperative experience. The technology can provide surgeons with a corneal thickness map and near histologic grade imaging of the epithelium, Schallhorn said during a presentation at Hawaiian Eye 2020.
“So, why is all of this important? It’s important in your keratoconic patients, for example. We know keratoconic corneas have focal thinning, and they also have an epithelial response. The epithelium thins over the cone and thickens over the base,” Schallhorn said in the presentation.
A 2015 study in Ophthalmology showed OCT-based IOL power calculation methods had the smallest variance in IOL power and the smallest mean error in prediction of 0.39 D. An IOL calculator available from the American Society of Cataract and Refractive Surgery features corneal power inputs for OCT. In a separate 2015 study in Ophthalmology, OCT-based IOL formulas had similar mean prediction errors comparable to ORA (Alcon) and the Haigis-L formula.
The preoperative mapping technology is typically available as an add-on for current OCT units, including the Zeiss Cirrus 5000/6000 and the Optovue Avanti/RTVue. The imaging technology is included with the Tomey Casia 2, but the unit is not available in the United States, Schallhorn said.
“I think OCT is incredibly helpful for complex anterior segment surgery. As the technology progresses, I think it will become integral with all our surgeries,” she said. – by Robert Linnehan
- Fram NR, et al. Ophthalmology. 2015;doi:10.1016/j.ophtha.2015.01.027.
- Schallhorn JM. Anterior segment OCT in comprehensive ophthalmology. Presented at: Hawaiian Eye 2020; Jan. 18-24, 2020; Koloa, Hawaii.
- For more information:
- Julie M. Schallhorn, MD, can be reached at Department of Ophthalmology, University of California, San Francisco, 10 Koret Way, San Francisco, CA 94143; email: email@example.com.
Disclosure: Schallhorn reports she is a consultant for Zeiss and Johnson & Johnson.