OCT plays key role in cataract surgery workup
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Screening cataract patients with OCT allows surgeons to identify preexisting retinal conditions that can affect IOL choice, calculations and surgical outcomes.
When the only choice of implant technology was a monofocal IOL, cataract surgery was a “one-size-fits-all” procedure, rendering preexisting pathology more or less irrelevant in terms of patients’ operative visual outcomes. Removing the cataract was paramount.
Today, however, premium IOL technology works by splitting light to provide patients with a range of vision — something patients not only expect but demand. Take, for example, a trifocal IOL that uses 50% of available light for distance vision, 25% for near and 25% for intermediate. The presence of any pathology that causes a loss of reception or transmission of light will cause advanced technology lenses to fail catastrophically, resulting in a suboptimal visual outcome. Therefore, it becomes imperative, particularly in the premium channel, that we obtain high-resolution retinal images using OCT to reveal changes not visible using an indirect lens at the slit lamp.
A recent study in the Journal of Cataract & Refractive Surgery confirmed that pre-cataract OCT screening improved patient management (Figure 1). The single-center retrospective study assessed the clinical relevance of routine preoperative spectral-domain OCT for identifying macular pathologies in patients scheduled for cataract surgery. In the 411 eyes evaluated, imaging detected macular pathology in 41% of eyes; nearly half of those (23%) did not have pathology on slit lamp biomicroscopy. Half of abnormal OCTs had macular degeneration, and 28% had epiretinal membranes (ERMs). The investigators reported that OCT imaging changed management for 26% of eyes, resulting in expanded preoperative counseling including advising against a presbyopia-correcting IOL in 28% of cases and a referral to a retina specialist in 8% of cases. Older patients and those with diabetes were significantly more likely to have abnormal macular OCT, the study authors noted.
Source: Farrell C. “Toby” Tyson, MD
Detail in posterior chamber
ERM is a common entity not easily detected on a slit lamp examination. J. Donald M. Gass, MD, reported it to be present in approximately 20% of patients older than 75 years. I image using a Spectralis multimodal SD-OCT by Heidelberg Engineering, which provides detail in the posterior chamber, showing ERMs as well as vitreomacular traction (Figure 2). These vitreous bands could cause traction on the retina once the vitreous is disrupted during cataract surgery, manifesting as cystoid macular edema in the course of the patient’s recovery. Again, such features are not visible on the slit lamp, nor will they show up as a change in the topography.
Anterior chamber OCT
OCT of the anterior chamber also plays a role in targeting the refraction, as we can use it to measure both anterior and posterior corneal curvature to determine total corneal astigmatism and the effect of central corneal power. This allows us to be more accurate with toric IOLs. For patients who have had previous refractive surgery, IOL calculation formulas are less accurate. Being able to plug in central corneal power for the formula, determined by OCT, allows us to consistently hit those more elusive refractive targets.
Is OCT cost-effective?
One barrier to wider adoption of OCT as part of the cataract workup is a lack of reimbursement. According to CMS payment guidelines, screening OCTs are not reimbursed unless a qualifying medical diagnosis is found. A recent analysis sought to determine the cost-effectiveness of OCT in the preoperative evaluation of a base patient considering cataract surgery with a multifocal IOL.
The authors found that approximately 20.5% of patients undergoing cataract surgery may have macular pathologies, of which 11% may not be found during the initial clinical exam. They used a base case of a 67-year-old man with 20/60 vision who underwent evaluation for his first cataract surgery with and without a screening OCT evaluation. For this base case, the researchers wrote, “adjunctive preoperative OCT was cost-effective from a third-party payer and societal perspective.”
Based on a willingness-to-pay threshold of $50,000 per quality of life year, the study estimated 64.4% of patients would agree to the additional cost for an OCT before cataract surgery.
- References:
- Gass JDM. Macular dysfunction caused by epiretinal membrane contraction. Stereoscopic Atlas of Macular Diseases: Diagnosis and Treatment. 4th ed. Mosby; 1997:938-950.
- Leung EH, et al. Ophthalmology. 2020; doi:10.1016/j.ophtha.2020.01.049.
- Weil Y, et al. J Cataract Refract Surg. 2021; doi:10.1097/j.jcrs.0000000000000389.
- For more information:
- Farrell C. “Toby” Tyson, MD, can be reached at Tyson Eye, 3925 Bonita Road, Bonita Springs, FL 34134; email: tysonfc@hotmail.com.
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