January 2013 OVS Announces Preview - News from the Editor

Coming in the January 2013 Optometry & Vision Science

Though peripheral refractive error is of interest in attempts to control myopia progression it seems that these two proposed methods are not achieving the same results for peripheral refraction. Our authors found peripheral refractive error showed myopic defocus associated with corneal reshaping but soft bifocal contact lenses did not, possibly due to decentration of soft bifocal contact lenses in peripheral gaze. They suggest that future studies of peripheral defocus during contact lens wear will require more sophisticated methods and that during peripheral autorefraction measurements participants should turn the head, as opposed to just the eyes.

The study finds peripheral astigmatic refraction is different between progressing and non-progressing myopes of the same age, axial length and central refractive error. The authors suggest this finding could help us understand the visually-guided growth mechanism of the eye leading to myopia progression and stabilization. They advocate that new customized optical solutions should account for these differences, in order to achieve myopia stabilization.

It has been shown in animal models that relative peripheral hyperopic defocus can alter central refractive error development and that retinal regions are capable of responding to local defocus signals. It has also been suggested that relative peripheral eye length may be associated with central changes in myopia in children. This study evaluates the all-important question of repeatability of on- and off-axis eye length measurements using a non-contact optical biometer (Lenstar). The authors report Lenstar central and off-axis eye length measurements are very repeatable, though repeatability was not as good 10° nasally on the retina.

Apparently so, but only by a small amount say our authors. They studied the angles between the main axes of the corneal surfaces and the keratometric axis in 407 corneas. The cornea appears to rotate as a solid body in such a way that corneal tip and tilt angles increase with age by about 2 min of arc per year. They note this tiny but significant (p < 0.005) rotation may have an important impact on optical quality as it could cause an important increase of the higher order aberrations of the cornea with age.

Addressing the controversy of just how long after surgery automated refraction becomes stable, the authors found that although corneal swelling may last 2 weeks, stable automated refraction is achieved in one week. They studied the question in a prospective, non-randomized, case series study of 124 consecutive eyes undergoing uneventful cataract surgery. A single experienced surgeon performed all surgeries using the same detailed surgical procedure.

Dry eye patients often complain about fluctuating blurred vision. This may result in a decrease in reading rate in dry eye patients, though this not previously been documented. The authors report a significantly reduced reading rate in dry eye patients compared to control subjects. As the dry eye severity increased, the reading rate decreased. This leads to their suggestion that reading speed may be used to monitor the effects of dry eye treatment.

Patients with Age-Related Macular Degeneration (AMD), and consequent peripheral retinal fixation, view faces with retina capable of only degraded vision. But apparently that is not the only reason that faces are hard to recognize for these patients. The authors found, in a study of AMD patients, that abnormal eye movements may contribute to deficits in face perception.

Our authors believe so. In 10 visually normal asymptomatic participants they measured the accommodative dynamics for a 2D step (2.5↔4.5D) stimulus before and after accommodative and convergence challenges (rapidly oscillating 50cm and 20cm fixation distances in one task and rapidly oscillating accommodation changes of 3D for a 50cm distance in the other). The accommodative system exhibited consistent fatigue effects in steady-state variability and response accuracy.

The retinal area of total spatial summation is known to decrease with light level and has implications for perimetry and target size choice. These changes have been explained in terms of the center-surround antagonism found for white light detection. However no such center-surround (S+/S-) antagonism has been found for the S cone ('blue cone") retinal pathways, raising the question off whether spatial summation decreases with light level increases for targets detected by S cones. The authors report that it does! They suggest that It is possible that these changes arise at the level of the visual cortex where both spatial and S-cone antagonistic receptive fields are known to exist.

Large population-based studies on stereopsis and low literacy are rare. 490 children attending primary (elementary) school in Tasmania, with literacy results below the 10th percentile, completed vision screening. Poor stereopsis, defined as >100 seconds of arc with the Titmus stereocircles, was found in one-sixth of the sample. This subgroup had higher associated signs and symptoms frequencies (e.g. Convergence Insufficiency, migraine, birth prematurity, attention deficit disorder) that deserve further study.

The pathogenesis of chronic glaucoma remains incompletely understood. The authors quantified optic nerve head anatomy using high definition optical coherence tomography in glaucoma patients. They found the optic nerve head in glaucoma involves a thin optic canal nerve fiber layer and peripapillary choroid, as well as a relatively deep distance from disc border to anterior lamina cribrosa. Such morphologic patterns may underlie glaucoma risk and progression in particular optic nerve head phenotypes.

Although the fundus appearance of multifocal vitelliform macular dystrophy (VMD) is quite variable the authors report the optical coherence tomography (OCT) features are relatively uniform. They believe OCT could help the pathological interpretation and facilitate the diagnosis.

New technological breakthroughs with high speed cameras make direct corneal biomechanical measurement possible with dynamic imaging of corneal deformation in response to an air pulse. The authors report corneal deformation parameters (e.g. deformation amplitude) were not only repeatable and reproducible but can also serve as important indicators of corneal biomechanical properties.

Our authors report the case of a 21-year-old female patient, who presented to the ophthalmology department as an emergency presentation due to ocular pain in the left eye that radiated to other areas of the face and neck. The patient suffered from a rare disease (Kindler syndrome) related to a mutation in the gene encoding Kindlin-1, which is an adaptor protein that is expressed by most epithelial cells. Corneal erosion on the left eye was the only significant condition was found. With conventional treatment, the corneal integrity was completely restored.

Toxic Anterior Segment Syndrome (TASS) is an unexpected, severe non-infectious inflammatory response after apparently uneventful intraocular surgery. There are multiple possible etiologies of TASS. However, as in our authors' clusters, specific causes are often not identified. Thorough review of all steps in surgery, processing of equipment and preparation of injectable solutions and materials, and adoption of best practices can prevent additional cases of TASS.

The use of corticosteroids is known to cause an increase in intraocular pressure (IOP). Our authors review a rare case where surgical intervention was required for IOP control secondary to repeated intravitreal implants of Ozurdex®, which was used to treat chronic diabetic macular edema. The efficacy and safety of Ozurdex® was compared to the more common intravitreal triamcinolone.