EyeWorld Asia-Pacific December 2017 Issue

patient. It keeps the head fixated using a forehead rest and a chin rest, keeping the patient’s head in the right plane and position. Some slit lamps have their own gauges, so you can use the 90-de- gree and 180-degree references by rotating the slit lamp and mark- ing these areas,” Dr. Srivastava explained. toriCAM toriCAM, developed by Graham Barrett, MD , is one of the most popular toric marking devices currently in use. The free app uses a guidance scope that allows for an easy, user-friendly implementa- tion. toriCAM lets the surgeon de- termine the axis of corneal marks for the right toric IOL alignment intraoperatively and measures the implanted IOL axis at the slit lamp postoperatively. “We have shifted to the tori- CAM in our clinic,” Dr. Srivastava said. “The guidance scope helps us in guidance and navigation automated piloting by using grav- ity and allowing us to use free markings to our advantage. I can make markings on the horizontal 180-degree axis without guidance, and toriCAM will use them as reference points to mark my IOL placement intraoperatively. When using toriCAM, you no longer have to mark at 90 degrees and 180 degrees. You can mark any- where on the cornea and toriCAM will use the mark as a reference point. You take a photo with the app and it will tell you where the mark is and use it as a gauge to mark the toric IOL placement, together with a Mendez degree gauge,” he said. Image guidance systems Digital image guidance systems are an interesting new option in the eye surgeon’s armamentari- um that use anatomic reference points to accurately identify the target axis for toric and multi- focal IOL placement and guide surgery. Dr. Srivastava uses the VERION Image Guided System (Alcon, Fort Worth, Texas), which allows the surgeon to photograph the eye preoperatively and use reference points from the image such as limbal and scleral vessels and features of the cornea and iris to create a digital overlay during live surgery. The target axis is projected into the right micro- scope ocular to guide surgery. The VERION incorporates an eye- tracking navigation system that compensates for eye movements and cyclotorsion. “Many different companies are now offering these types of systems. We use the VERION that uses anatomic data and provides gauges on where to position the toric IOL,” Dr. Srivastava said. “There is a display inside the op- erating microscope that is within the surgeon’s view, and the guid- ance system guides us based on The VERION system helps with intraoperative alignment of the IOL without depending on preoperative or intraoperative manual markings. Source (all): Samaresh Srivastava, DNB the vessels and the iris architec- ture. The toric positioning guid- ance system shows us if we are on or off axis. You do not necessarily need to mark the eye because it is a purely automated procedure and there are no problems associated with the subjective evaluation of marking. We can center the rhexis on the visual axis, which gives us a full overlap and guides us for manual capsulorhexis, if you do not use femto.” iTrace Surgical Workstation “We have found the iTrace Surgi- cal Workstation [Hoya Surgical Optics, Chino Hills, California] very useful because it calculates which model of IOL is right for each patient,” Dr. Srivastava said. “Again, you can use limbal vessels for reference and the machine tells you how many degrees from the reference point to place the IOL. You use the gauges to digital- ly mark two or three points before the IOL is placed and can check the postoperative position. The iTrace offers a toric IOL check and enhancement for after surgery, so if you think your toric IOL is not in the right axis, you can still rotate it by checking aberrometry after surgery.” Intraoperative aberrometry is used in addition to preop biom- etry to minimize refractive error and help determine IOL power se- lection and placement. According to Dr. Srivastava, “Image-guided systems, as of today, are still more reliable than intraoperative aber- rometry in terms of toric position- ing. However, I would not rely on image-guided without a marking backup because sometimes the technology is better in theory than reality.” EWAP Editors’ note: Dr. Srivastava has no financial interests related to his comments. Contact information Srivastava: samaresh@ raghudeepeyeclinic.com 62 EWAP CATARACT/IOL December 2017 Don’t write – from page 61