Cataract surgery lowers IOP, medication use
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Patients with ocular hypertension may benefit from cataract surgery, according to findings published in the American Journal of Ophthalmology.
“Studies suggest that cataract surgery lowers IOP, and that this reduction is generally proportional to presurgical IOP. As well, several papers report a decrease in ocular hypotensive medications with cataract surgery,” Steven L. Mansberger, MD, MPH, ophthalmologist at Legacy Health in Portland, Ore., and colleagues wrote. “While these reports are helpful, they rarely examine the change in both IOP and ocular hypotensive medications, nor the changes over a long period of time.”
In a secondary analysis of results from a randomized clinical trial, Mansberger and colleagues analyzed data from 623 participants aged 40 to 80 years from the Ocular Hypertension Treatment Study (OHTS) Medication Group. Of these participants, 92 (n = 149 eyes) underwent cataract surgery in at least one eye during the study, while the remaining 531 (n = 1,004 eyes) did not. All participants had IOP between 24 mm Hg and 32 mm Hg in one eye and between 21 mm Hg and 32 mm Hg in the other, no glaucomatous structural or functional damage at enrollment, and best-corrected visual acuity of at least 20/40 in both eyes.
Researchers compared data from the cataract surgery group after their first postoperative visit with the control group’s corresponding 15th visit. Because the OHTS does not specify the date of this visit, Mansberger and colleagues refer to the visit as the “split date.” The primary outcome was the difference in preoperative and postoperative IOP and the number of classes of ocular hypotensive medications between the cataract and control group over a 72-month period.
Researchers found that cataract surgery decreased the number of ocular hypotensive medications (mean –0.4 medications; P < .005) compared with the control group. At the defined split date, 23% of eyes were free of medication, and 41% of eyes had reduced medication. While the cataract surgery group experienced a decrease in IOP (P < .001), the difference in IOP between them and the control group decreased over time and became non-significant after 12 months.
“This study showed that cataract surgery produced a lowering of IOP for about 1 year after surgery in the medication group of the OHTS and decreased medication burden for a prolonged period. Glaucoma conversion or incidence of primary open angle glaucoma decreased after cataract surgery when considering optic disc as an endpoint, but not for visual field, nor when combining either visual field or optic disc endpoints,” Mansberger and colleagues wrote. “Together, these data suggest modest benefits of cataract surgery (beyond the visual improvement resulting from cataract surgery) in reducing IOP and medication burden when a study-specified target IOP was used.”
Perspective
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“Phaco may be the best MIGS procedure we have …” (Capitena Young et al.).
This bold statement in a recent review paper caught my attention, and has remained in the back (OK, the middle) of my mind for the last 18 months. In the EAGLE Study, lens extraction unequivocally demonstrated its value in the management of angle closure disease, but its role in open angle glaucoma has remained less certain.
Nearly a decade ago, the OHTS showed that phacoemulsification reduced IOP an average of 17%, with the degree of pressure reduction being proportional to pre-surgical level: the higher the IOP, the greater the decrease. In this secondary analysis of OHTS data, Mansberger’s group confirms that cataract extraction decreases both IOP and medication burden, the former more modestly for approximately 1 year, the latter more significantly over at least 6 years.
So, in addition to an improvement in vision, cataract surgery also affords the benefits of decreased IOP (albeit a modest and transient effect), fewer medications (reducing preservative exposure and potentially improving adherence) and enhanced subjective and objective assessment of optic nerve head-retinal nerve fiber layer-retinal ganglion cell structure.
While not a panacea, cataract surgery plays an important role in the management of open angle glaucoma.
Reference:
Capitena Young CE, et al. Curr Opin Ophthalmol. 2020;doi:10.1097/ICU.0000000000000623.
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