Optometry and Vision Science (OVS) Announces Preview - June 2013

Surprisingly, our Fry Awardee has found good evidence that it does. More importantly this reflects an unexpected plasticity of the visual cortex quite late in life. Patients with foveal vision loss and a new PRL show experience-dependent plasticity. So, old dogs do learn new tricks! The implication of this experience-dependent plasticity is that perceptual learning might be a useful rehabilitative paradigm in macular degeneration.

Asian countries are particularly concerned about myopia progression because of its unusually high prevalence. Our authors build on the demonstrated reduction of moderate myopia progression's axial length changes with orthokeratology (OrthoK). But little is known for higher myopia levels; no lenses have yet been designed for these patients. The authors have taken a conservative interim approach for high myopes by targeting 4D reduction by OrthoK (partial) combined with daytime spectacle correction of residual refractive error.  Their 2-year single-masked, randomized study showed that this partial (PR) OrthoK effectively slowed myopic progression in high myopes; axial elongation was 63% slower in partial OrthoK treated children compared to children wearing spectacles.

Our authors quantitatively assessed the amount of axis misalignment by determining deviation from the horizontal reference line using a corneal topographer with an anterior segment image. Horizontal meridian limbal marking using a slit lamp microscope showed misalignment by an average of 3 to 7 degrees, and these alignment errors may reduce the effectiveness of astigmatic correction by an average of approximately 10% to 20%.  Obviously, as the authors note, this can be critical when correcting significant astigmatism. Precise preoperative axis marking is important.

Our authors compared epithelial barrier function (EBF) and staining using silicone hydrogel lenses (SH) worn on a daily basis. The corneal EBF of 10 non-lens wearers and 15 age-matched asymptomatic SH contact lens wearers were assessed using fluorophotometry. Staining was measured using biomicroscopy.  Large individual variations in both measures led to a poor correlation between corneal staining and EBF in the contact lens wearers. The authors also compared two different care regimens. They conclude that daily wear of highly oxygen permeable SH lenses increases the corneal epithelial permeability to fluorescein, probably due to increased mechanical effects and that lens-solution interactions can add to this effect.

Bacterial adhesion to contact lenses is believed to be the initial step for the development of several adverse reactions (e.g. microbial keratitis) that can occur during lens wear. This study examined the effect of an application of a combination of commercial proteins on the adhesion of exposed bacteria (Pseudomonas aeruginosa and Staphylococcus aureus) to contact lenses. They found that the lysozyme/lactoferrin combination increased the adhesion to contact lenses for only a single strain of S. aureus 031. No strain of bacteria was influenced by lipocalin presence on lenses, suggesting that these proteins (in isolation) are probably not responsible for increases in adhesion to lenses seen with contact lens wear.

The authors measured the optical properties of five contemporary PALs (Varilux Comfort Enhanced, Varilux Physio Enhanced, Hoya Lifestyle, Shamir Autograph, and Zeiss individual) by direct physical measurement of surface shape. Comfort Enhanced and Physio Enhanced have freeform front surfaces, Shamir Autograph and Zeiss Individual have freeform back surfaces, and Hoya Lifestyle has freeform properties on both surfaces. Their non-optical method can be used to evaluate a PAL by surface height measurements, with the optical properties directly related to its front and back surface design. 

Our authors use a new, integrated, in vivo laser scanning confocal microscopy (LSCM) to evaluate the whole ocular surface (cornea, basal and tarsal conjunctiva, Meibomian glands, lid margins). They use controls and patients with dry eye [primary Sjogren's syndrome (SSI), non-Sjogren's syndrome dry eye (non-SSDE), and Meibomian gland disease (MGD)]. The approach allows the identification of specific abnormality patterns for different types of dry eye. It lends itself to both clinical and research application.

The cornea, the major optical component of the eye, causes of the eye's astigmatism and higher order aberrations. But small sample size, small age range, an unrealistic model of the cornea or attention only on the anterior corneal surface limit prior corneal optics studies. Here age-related changes of the corneal surfaces are studied with a Pentacam Scheimpflug camera on a group of 407 corneas of 211 participants aged from 4 to 79. The authors characterize average corneal surfaces as misaligned general aspheres. Corneal spherical aberration (SA) is higher than total SA for the eye, but both increase with age at a similar rate. As expected the lens partially compensates for the SA of the cornea and does so throughout aging.

The choroid is the source of many vision-threatening diseases. Using enhanced depth imaging optical coherence tomography (EDI-OCT) the authors derived volumetric measurements of the posterior choroid via three-dimensional analysis of the choroid in patients with high myopia. They compared structural differences with non-myopic control participants. The choroidal thicknesses at all 9 regions of clinical interest (defined by the Early Treatment Diabetic Study) in the high myopia group were significantly thinner than those in the normal refractive group. From 20 × 20 degree raster scans, consisting of 25 high-speed line scans, the authors could show quite different relative thickness profiles across the choroid between the highly myopic and the control participants.

People with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) often report problems directing their visual attention and filtering out irrelevant visual information. There is no diagnostic laboratory test or biomarker for CFS. Our authors demonstrate these problems experimentally using the Useful Field of View, a spatial cueing task and visual search measures. Those with ME/CFS were worse than control participants when they had to direct their attention to objects that were presented in the midst of visual distracters. The authors speculate that this vision characteristic might be useful for diagnosis of ME/CFS.

Three rare cases are presented of macular holes coexistent with posterior uveal melanoma. To the best of the authors' knowledge, only 6 cases of macular hole formation coinciding with posterior uveal melanoma have been reported in the past. The possible pathogenesis of a macular hole secondary to uveal melanoma growth is noted, as well as the necessarily difficult strategies to treat uveal melanoma before attempting macular hole repair.

If your patient presented with bloody tears, would you know how to manage and treat that patient? The author documents a rare case of hemolacria, bloody tears, exhibited in a patient with multiple severe systemic diseases. Speculated etiologies are centered on the patient's chronic kidney failure, aggressive anticoagulant therapy, and severely uncontrolled hypertension. The authors' clinical case demonstrates the importance of knowledge of specific ophthalmic testing and proper interdisciplinary referrals necessary to find the underlying cause.

Trichotillomania is characterized by repetitive, compulsive hair pulling that leads to noticeable hair loss. When it involves the eyelashes, topical bimatoprost may be used to treat the loss of the eyelashes (madarosis) by increasing growth. In this case report, a 55-year-old female presented with a long history of eyelash pulling. She began treatment to control the impulses one week prior to her appointment. Management of trichotillomania presents an opportunity for optometrists to collaborate with mental health providers for the betterment of patients. By expediting the lash growth, topical bimatoprost can improve a patient's self-image, reinforce compliance, and play an important adjunctive role in any therapy regimen.

The ubiquitous human ectoparasite demodex (genus) is commonly found burrowed in the eyelash follicles of its host. Generally considered a harmless saprophyte, growing opinion suggests that demodex can be pathogenic. Traditionally, identification of demodex (species folliculorum or brevis) is by microscopic evaluation for the mite on an epilated eyelash. A new simple technique is described. It does not require a light microscope or the pulling of the lash from its follicle and is well illustrated with video clips.

The many psychological factors and other mechanisms for soft contact lens-related end-of-day symptoms of dryness are reviewed by our author.  Quite clearly, apart from tear function, contact lens condition, compliance with lens care instructions, and symptom strength, lens awareness may also be determined by psychological factors such as motivation, high expectations for comfort, and sense of subjective well-being.