Analyzing corneal asphericity, OCT angiography, and balance control issues in glaucoma patients

Cataract surgery: corneal asphericity affects refractive outcome

When using third-generation IOL power formulas, be sure to take anterior surface corneal asphericity into consideration because it can influence the refractive outcome, according to researchers from Italy and the United States.

More in this issue: Metrics help explain balance issues in glaucoma patients

Reporting in the Journal of Cataract and Refractive Surgery, the researchers conducted a retrospective comparative case series of 115 eyes in 115 consecutive patients, all of which were implanted with the same type of intraocular lens (Acrysof SA60AT, Alcon).

The researchers calculated intraocular lens power using the Haigis, Hoffer Q, Holladay 1, and SRK/T formulas. Asphericity (Q-value) was measured by three different methods: a Placido-disk corneal topographer, a rotating Scheimpflug camera, and a rotating Scheimpflug camera combined with Placido-disk corneal topography All measurements were conducted at 8.0 mm.

By linear regression, the relationship between the error in refraction prediction (as measured 1 month post-surgery) and the Q-value was assessed.

The researchers found that with all of the formulas and devices, there was a statistically significant relationship between the error in refraction prediction and the Q-value with all formulas: A more negative Q-value (prolate cornea) was associated with a myopic outcome in all cases, whereas a more positive Q-value (oblate cornea) was associated with a hyperopic outcome.

To read the abstract of the study, click here.

Next: OCT angiography useful in patients with diabetic retinopathy

OCT angiography useful in patients with diabetic retinopathy

Ophthalmologists may find optical coherence tomography (OCT) angiography clinically useful to evaluate the microvascular status and therapeutic effect of treatments for diabetic retinopathy (DR), according to a prospective study out of Japan published in the American Journal of Ophthalmology.

The researchers noted that microaneurysms and retinal non-perfused areas can be clearly visualized, and the technology also allows each layer of the retinal capillaries to be observed closely. Also, quantitative information on new vessels can be obtained.

More in this issue: Cataract surgery: corneal asphericity affects refractive outcome

Using a high-speed, 840-nm wavelength spectral-domain OCT device (RTVue XR Avanti, Optovue), the investigators scanned 47 eyes of 25 patients who had DR. They detected blood flow using the split-spectrum amplitude-decorrelation angiography algorithm. They also obtained fluorescein angiography (FA) images in all eyes. The scientists compared their ability to visualize microaneurysms, retinal non-perfused areas and neovascularization with that of the en-face OCT angiograms.

The researchers found that, in 42 eyes, FA-detected microaneurysms near the macula showed up as focally dilated saccular or fusiform capillaries on OCT angiograms of the superficial and/or deep capillary plexus. FA-visualized retinal non-perfused areas looked like lesions with no or sparse capillaries on OCT angiograms. In 7 eyes, area measurement of retinal non-perfusion near the macula showed a difference between the extent of non-perfused areas in superficial and deep plexuses. In 4 eyes, researchers could clearly visualize the vascular structures of neovascularization at the optic disc using OCT angiography. They quantified decreases and re-increases of flow in new vessels in an eye treated with anti-vascular endothelial growth factor.

Next: Metrics help explain balance issues in glaucoma patients

Metrics help explain balance issues in glaucoma patients

New metrics developed by a research team with members from the United States, Brazil, and The Netherlands may help ophthalmologists better understand balance control issues in patients who have glaucoma. The cross-sectional study, published in Ophthalmology, presented and validated a novel paradigm that assesses postural reactivity to dynamic visual stimuli using a virtual reality environment.

Using standard automated perimetry, the researchers studied 42 patients who had glaucoma and repeatable visual field defects. The study had 38 control healthy subjects. All participants completed a standard questionnaire about their history of falls.

While wearing stereoscopic head-mounted goggles, the doctors evaluated patients’ postural stability using a force platform as static and dynamic visual stimuli were introduced. “The dynamic visual stimuli presented rotational and translational ecologically valid peripheral background perturbations,” they wrote. The investigators also tested postural stability in a completely dark field so they could gauge somatosensory and vestibular contributions postural control.

The authors measured torque moments around the center of foot pressure on the force platform, and they calculated standard deviations of the torque moments (STD) as a measurement of postural stability; they were reported using Newton meters (Nm). Poisson regression models were used to determine the association with history of falls. Confounding factors included age, gender, body mass index, severity of visual field defect, best-corrected visual acuity and STD on dark field condition.

During both translational and rotational stimuli, study participants with glaucoma had larger overall STD than did controls. Postural metrics obtained during dynamic visual stimuli better explained history of falls compared with metrics obtained in static and dark field condition, the researchers said.. “In the multivariable model, STD values in the mediolateral direction during translational stimulus were significantly associated with a history of falls in patients with glaucoma,” according to the authors.