IN THIS ISSUE:
Destined for an Acuity Drop With Age?
Acuity slowly decreases in the later decades of life (e.g., between 50 and 80 years). However, our authors found that, in a fast-changing subset of 50 of the 148 subjects that they followed for 4 years within this age range, it was the change in optical quality metrics that was the most important in accounting for this faster changing subset (four or more letters in the 4-year span). They argue that these fast-changing optical metrics allow the identification of those at risk of being on a fast track to acuity loss.
Editor’s Choice open access
Don’t Crowd Letters Away From My Fovea
Classic research on contour interaction (crowding) in the fovea with high-contrast optotypes guided the design of modern letter charts. But less is known about how crowding affects acuity measurements more peripherally. The authors found that, to avoid the deleterious effects of crowding on acuity, targets at 3- to 10-degree eccentricity require three to four times as much blank space between optotypes compared with foveal targets. Consequently, the use of classical acuity charts may underestimate the acuity in the periphery because of excessive of crowding for that retinal location.
Optimizing IOL Power Calculations
Our authors report that using a single value of refractive index for calculation of corneal power can lead to significant errors in IOL power calculations. They offer a new formula using a variable index obtained through Gaussian optics and applied to the Gullstrand and LeGrand eye models. They believe that they can explain why some IOL power overestimations occur with conventional formulas.
It Is Those “Pesky” Incomplete Blinks and Tear Film Instability
Tear film instability is associated with prolonged VDT viewing. Our authors’ study suggests that although blink rate is reduced in this situation, it is the incomplete blinks that seem to be important in producing tear film instability.
Peripheral Refraction Compared for Single-Vision and Multifocal Contact Lenses
Myopia progression has been related to relative peripheral retinal hyperopic refraction. This raises a question about the extent to which single-vision versus multifocal (MF) soft contact lenses (SCLs) produce changes in peripheral refraction. The authors find that MF SCLs produce relatively less peripheral hyperopic shift at all locations in the horizontal meridian and speculate on how this might relate to reports of less myopic progression with MF SCLs.
African American Corneas More Prolate
In their study using a Pentacam (Oculus), our authors discovered that African American eyes have a more prolate (flattening from center to periphery) corneal asphericity than Caucasian eyes. Their asphericity findings were little influenced by age, sex, or refractive error, with only limited variations being identified. The cornea’s relative asphericity has implications for contact lens fitting, calculation of intraocular lens powers, and refractive surgery.
Linking Comfort and Adverse Events in Contact Lens Wear?
The authors note that the most comfortable contact lens is not free of problems, and the contact lens with minimal problems may not be the most comfortable. The authors analyze retrospective data to try to provide a combined method to evaluate both contact lens comfort and adverse events in a simple way.
Visual Performance for Disposable Contact Lenses
The authors’ study compared the visual performance provided by seven different daily disposable contact lenses for 12 hours. Contact lens characteristics, such as material and water content, may be the cause of some of the differences in visual performance.
Repeatability of Ocular Response Analyzer Metrics
The authors found that the Ocular Response Analyzer demonstrates excellent repeatability for both intraocular pressure and corneal biomechanical measures. Furthermore, they found no significant differences with sex. Their study supports the growing evidence for the reliability of these clinical data.
Portable Tonometers Compared for Patients in the Supine Position
Sometimes, IOP needs to be assessed while the patient is in the supine position. The authors compared four different portable tonometers for this position and found that the agreements between three of them (iCare, Tonopen XL, and Kowa HAT) were clinically acceptable, despite some differences between instruments.
Prophylactic Laser Iridotomy Doesn’t Change Anterior Chamber Depth in Angle Closure Glaucoma Suspects
Laser peripheral iridotomy is a well-known preventive measure against acute primary angle closure (PAC) and is routinely performed in PAC suspect (PACS) eyes. Whether this impacts central anterior chamber depth is controversial. In this interventional case series, the authors, providing some clarification for the literature, found that laser peripheral iridotomy did not affect central anterior chamber depth as measured by Lenstar in PACS.
New Approach to Optimal Correction of Corneal Ectasia
Although the extraction of topographic curvature data as a foundation for gas-permeable contact lens design is well documented, this study is probably the first to describe the extraction of corneal height data to guide hybrid contact lens fitting. Our author suggests a novel technique to optimize efficiency and accuracy in fitting SynergEyes ClearKone lenses using baseline corneal topography-derived data from 73 eyes to predict the lens parameters for the management of corneal irregularity.
Underdiagnosed, Undertreated, and Underappreciated: Demodex at the Ocular Surface
Our authors note that Demodex, “tiny bugs closely related to spiders living in the pores of your face,” is highly underdiagnosed in eye care. Using five patients as examples, they illustrate a clinical diagnostic protocol to detect the mites, which they suggest is highly underdiagnosed, undertreated, and underappreciated at the ocular surface.
Central Serous Chorioretinopathy and Macular Pigment Distribution
Generally, highly symmetrical distributions of macular pigment (MP) are found between eyes of patients. This case report of resolved central serous chorioretinopathy identified asymmetric changes, which corresponded to RPE changes noted in fundus photos. The authors speculate that similar macular pigment changes may occur in other macular conditions in which the sensory retina is affected (e.g., cystoid macular edema and clinically significant macular edema). They do detailed mapping of MP with their customized technique.
Identifying a Rare Yet Troublesome Cause of Elevated IOP
Idiopathic elevated episcleral venous pressure (IEEVP) is a rare condition that can lead to difficult to manage glaucoma. Our authors emphasize the importance of recognizing the association between raised IOP and engorged episcleral veins in the detection and difficult management of IEEVP.
Glaucomatous Atrophy of Retinal Nerve Fiber Layer and Myelination
The authors detail the long-term follow-up of a patient with extensive myelination of the retinal nerve fiber layer in an eye with poorly controlled and progressive glaucoma. For several years, there was profound regression and atrophy of the myelination, illustrating that this condition is not unchanging, as often thought, and that glaucomatous atrophy may involve not only the retinal nerve fiber layer but myelination as well.