November 2012 OVS Announces Preview - News from the Editor

Coming in the November 2012 Optometry & Vision Science

Our authors compare three measurement methods on 5 contemporary PALs (Varilux Comfort Enhanced, Varilux Physio Enhanced, Hoya Lifestyle, Shamir Autograph, and Zeiss individual) with plano distance power and a +2.00D add. Contour plots of spherical equivalent power, cylindrical power, and higher-order aberrations in all PALs were generated to compare the differences by measurement method. The authors conclude that while the three methods of measuring the optical properties of PALs were comparable, they were not interchangeable.

The authors use a ‘model blink cell’ in vitro to answer this question affirmatively. Their model device cycled the contact lenses in and out of an artificial tear solution containing trace lipids, allowing the solution to break over the lens surface. They found that both short term sequences (10 hrs) and longer term times (6 days of 14hr cycle plus 10 hr submersion) increased both cholesterol (about 3X) and phosphatidylcholine (about 1.4X) deposition for some of the contact lens materials, compared to total and continuous submersion in the tear solution without air exposure.

A lot, say our authors. Some soft contact lens wearers show solution induced corneal staining (SICS) while others do not. In this study of almost 450 participants, 35% showed SICS when challenged with lenses presoaked in a multipurpose solution. The authors conclude from differences noted between the ‘stainers’ and ‘nonstainers’ that poor tear quality is a pre-disposing factor for SICS.

Tear instability, during blink suppression, produces local optical disturbances corresponding to areas of tear break-up, which are not fully characterized by conventional Zernike modal analysis of aberrations. Additional higher order aberrations and micro-aberrations, termed scatter, provide a significant contribution to image blur following tear break-up.

The visual disability of visually impaired children performing daily tasks appears better characterized by a second version (LVP-FVQ II) of an established self-reporting questionnaire (LVP-FVQ). The second version is effectively able to discriminate between visual disabilities of school children and is valid across age, gender, duration of visual impairment, and location of residence.

Assessing visual acuity in visually impaired patients is critical. Our authors compared two commonly used test options (LEA Numbers Low Vision Book and the Feinbloom visual acuity chart) and compare them to the ‘gold standard’ for visual acuity—the ETDRS chart. For 18 visually impaired participants (including 9 children) each test performed much the same against the ETDRS chart, as was the repeatability of each of the charts, albeit slight less repeatable than the ETDRS chart itself.

While the soft lens-induced changes in the anterior segment layers found by our authors were statistically significant, the clinical significance remains an open question. The change, measured by OCT, was greater for the limbal/scleral region than the peripheral corneal region.

The relatively new multifocal toric contact lens the authors studied is seen as an acceptable option to compensate for both presbyopia and astigmatism. In a crossover design experiment they compared the vision provided by a multifocal toric contact lens to a single vision toric contact lens from the same company (Coopervision); the latter was used with reading glasses.

If the hypothesis that orthokeratology (OK) induces myopic peripheral retinal refractive error, a presumed deterrent to increased axial length growth, then the authors argue that large pupils ought to create effectively more defocus which in turn would further slow myopic axial length increase. Indeed the authors report that large pupil diameters facilitate the OK effect of slowing axial growth in myopia.

The authors are able to come to this conclusion using in vitro objective and subjective methods on excised corneal stroma to determine the refractive index of the anterior and posterior stroma. They were also able to note that dehydration occurred at the same rate both anteriorly and posteriorly. Most important, the determined relationship of hydration to refractive index ought to be useful in improving accuracy and predictability of current models linking stromal refractive index to hydration.

Dry eye syndrome (DES) is a multifactorial condition associated with potential damage to the ocular surface. Recently marketed lubricant eye drops containing gelling agents, directly address the tear film instability or mucus dysfunction in dry eye. This randomized, clinical study provides evidence of safety and efficacy of a lubricant eye drop containing Hydroxypropyl-guar (HP-guar) gelling agent in treating symptomatic dry eye in adult Chinese patients.

Dry eye is a common condition with significant impact on quality of life. The authors conducted a systematic review of seven randomized controlled treatment trials, to assess the effectiveness of lipid-containing lubricants (LCL) on dry eye treatment. They report that most studies have demonstrated the effectiveness of lipid-containing lubricants on improving select signs of dry eye.

Our authors review the pathological and biochemical mechanisms that are likely associated with smoking and age-related macular degeneration (AMD). They urge greater commitment by optometrists to both educate patients on the importance of cessation of smoking as it relates to the mechanisms of AMD and to join smoking cessation health care networks.

Common ophthalmic treatments (e.g. IOLs, corneal refractive surgery, inlay lenses and inlay apertures) have the potential to alter the centration and astigmatism of the eye's optical elements thereby changing the eye's natural chromatic aberration. To understand and evaluate these changes in a clinical environment requires careful definition of terms set in a rigorous mathematical context. Our author proposes general definitions for longitudinal and transverse chromatic aberration that can be applied for systems which, like the eye, may be heterocentric and astigmatic.

Our authors report cycloplegic refractive error data, visual acuity, and amblyopia for about 600 children aged from 2 months to 12 years old in a rural Polish town. The children had not previously been screened. Perhaps not surprisingly, the prevalence of amblyopia was 3 times higher in this unscreened population compared to screened populations and leads to a call for children’ vision care in Poland.

Although aniseikonia is typically optically-induced, it can also occur secondary to a retinal disease or retinal surgical procedure. In a series of cases our author demonstrates that the binocular vision problems that develop can be very debilitating and challenging, but important to treat.

This report emphasizes the importance of addressing the “march of signs and symptoms” and the fact that two separate entities can manifest in neurological disorders. In this case the patient was “cured” of a pituitary adenoma but later presented with changes in both symptoms and signs. Change should stimulate a further investigation of the patient.

Syphilis in today’s society? Yes, it is on the rise and as clinicians the disease must be in our thought process. Again, we are faced with pupillary analysis and our shortcomings in that area. Most of the time this is a test entrusted to the tech and by the time we see the patient the pupil is dilated. There is “new” technology available that can help us with more effective pupillary analysis. Pupillary issues + optic neuropathy + hearing loss = the possibility of neurosyphilis.

Dissociated horizontal deviation is a rare strabismus presentation in which both esotropia and exotropia can manifest in the same patient. The variation appears to be dependent on which eye is fixating. While multiple surgical procedures are reported to help, this report suggests that long-term vision therapy may be of benefit.

Autoimmune disorders and their ocular manifestations are on the rise worldwide. Antiphospholipid Syndrome has the potential to create arterial and venous thrombi and as such should be on the list of differentials in all vaso-occlusive retinopathy…such as branch retinal artery occlusion.

Pituitary tumors are likely to present in a primary care office as vision alteration and a variable visual field defect. Pituitary tumors are the most common neuroendocrine tumor with prolactinomas accounting for up to 40% of these. Early detection can result in very positive patient outcomes, but are often uncovered first in the eye examination because of the subtleties of systemic presentation.