A recent study notes that 15% to 22% of patients with chronic graft-vs.-host disease (GVHD) who undergo cataract surgery rely on scleral lenses, and after surgery, they’re are expected to resume their scleral lens wear within about one week, regardless of visual outcome.
Currently, there’s no reliable approach to achieving satisfactory vision: obtaining a manifest refraction before cataract surgery is difficult in this population because the ocular surface deteriorates dramatically upon removal of the scleral lens. Furthermore, many cataract surgeons select refractive targets assuming the patient will replace their scleral lenses postoperatively, but this is usually not the case. Replacing scleral lenses is financially burdensome and can cause unnecessary delays to vision recovery while waiting for a prescription change.
A Unique Scleral Lens Population
This study focused on three patients, all of whom were diagnosed with hematologic malignancies and receive allogenic hematopoietic stem cell transplantations (HSCT). Although this is a potentially curative therapy for some, it also increases a patient’s risk for graft-v.-host disease (GVHD), which affects 30% to 60% of patients after allogenic HSCT.
Ocular GVHD compromises ocular surface integrity, leading to significant issues such as poor vision, ocular irritation, pain, photophobia, corneal ulceration, melt and even perforation. Therapeutic scleral lenses can help to alleviate these symptoms by expanding the precorneal tear film within the lens vault and supporting the corneal epithelium. These custom prostheses, however, are quite expensive and their availability varies from region to region. Thus, researchers are on a quest to find a way to help these patients stay in their lenses after cataract surgery without the need to replace them.
In the study, the authors propose a novel approach to reverse-calculate the refractive aim in patients with well-fitted, properly over-refracted scleral lenses. They say this will maximize the immediate post-op refractive outcome without the need to replace the lens and cause undue financial stress and delays in vision recovery.
In this retrospective single-surgeon study, the researchers determined the target refraction for the intraocular lens by considering the effective scleral lens system power. They calculated this by adding the known scleral lens spherical power to the difference between the scleral lens base curve and the average keratometry value.
Six eyes of three patients with ocular GVHD who wore scleral lenses underwent cataract surgery with this refractive calculation. Postoperatively, all patients achieved corrected visual acuities of 20/30 or better while wearing their original scleral lenses at the follow-up visit one week later. All six eyes resumed full scleral lens use a week after cataract surgery and no patients required scleral lens replacement.
The authors noted that all six eyes were moderately myopic or near emmetropic before cataract surgery. They said that targeting a refraction in this range is practical because it’s compatible with necessary daily activities, such as the insertion and removal of scleral lenses. “If the preoperative refractive state is hyperopic or highly myopic, it could be beneficial to reestablish a more practical refractive outcome for best uncorrected near and intermediate vision,” they wrote.
This particular approach to reverse-calculating the target refraction relies heavily on the assumption that the scleral lenses are well-fitted and properly over-refracted. Additionally, the authors stressed the importance of performing biometry or autokeratometry efficiently and immediately after scleral lens removal.
“Such an approach also solves the dilemma of whether to fit scleral lenses in patients with visually significant cataracts requiring urgent ocular surface protection, knowing that they will likely need to be replaced after cataract surgery,” the authors wrote.
Ma KK and Luo ZK. Novel method to determine target refraction in cataract surgery for patients dependent on therapeutic scleral lenses. Eye Contact Lens. October 1, 2020. [Epub ahead of print].