Optometry and Vision Science (OVS) Announces Preview - February 2015
Coming in the February 2015 Optometry & Vision Science
Here are brief highlights. The online and printed copy will be available early-February. E-Publication Ahead-of-Print now available for all these articles at http://journals.lww.com/optvissci
Anthony J. Adams, OD, PhD, FAAO Editor-in-Chief
New LED Color Vision Test for the World?
In a series of 3 papers in this February 2015 OVS issue our authors describe the performance of a new Railways LED Lantern Test (RLLT) already approved and used within Australia, compare it to the Canadian Lantern test, and finally establish its viability as an international test to accompany two lantern tests already accepted internationally. In this first paper they tested its performance for 37 color deficient and 46 color normal participants and then, with appropriate modification, retested it on 106 color normal participants. All 106 color vision normals and most mildly affected color vision deficient pass the modified RLLT at 3m demonstrating adequate color vision for the less demanding railway tasks. If tested at 6m, it essentially reinforces normal color vision as the standard since all color deficient participants failed.
Australian and Canadian Railway Color Vision Lantern Tests Compared
The new Railway LED Lantern Test (RLLT) described for both color defective and color normal participants in our authors’ first paper, is now compared to the Canadian Railways Lantern Test (CNLAN). Both tests pass the international standard for color normals (CIE Color Vision Standard 1, which predates both lanterns, and allows some very mild color deficient observers to pass). Despite the different construction principles, the RLLT and CNLAN have pass/fail levels that are comparable with the Holmes-Wright Type B, which is suggested in the CIE Color Vision Standard 1 but is no longer commercially available.
Lantern Tests Compared for Color Defective Vision
The Commission Internationale de l'Éclairage (CIE) has a Color Vision Standard 2 with two nominated tests for railway signal codes (Farnsworth Lantern (FaLant) and the OPTEC® 900). Neither test uses the railway signal color code of red, yellow and green and only the OPTEC® 900 is commercially available. Our authors compared the performance of these two lantern tests and the new Railway LED Lantern test (RLLT) with 46 color vision normal and 37 color vision deficient observers. Despite the different construction principles, the pass/fail levels of the RLLT, FaLant and OPTEC® 900 are comparable and consistent with the performance of other lanterns suggested by the CIE for Color Vision Standards 1 and 2.
Daily Contact Lens Cleaning, Adverse Events and Extended Wear
Although continuous wear is a convenient mode of lens wear, it is associated with an increased risk of complications most likely related to increased microbial lens contamination and colonization due to lack of daily cleaning. In this proof-of-principle study, our researchers set out to test if daily morning cleaning of lenses, during a 30 day continuous wear schedule did not impact the rate of ocular adverse events. It did not impact it.
Contact Lens Case Contamination is Common
Daily wear of contact lenses requires the use of a contact lens storage case overnight. Lens cases play an essential role in disinfection of contact lenses, however, without proper maintenance, the lens case itself may become contaminated with microorganisms during handling. Contact lens wearers were surveyed and microbial analysis of lens cases was performed. Washing hands with soap and water, air-drying lens cases, and matching of the disinfecting solution with lens case (i.e. from same manufacturer) all helped reduce case contamination.
A Center-Near Multifocal Contact Lens Compared to Monovision
Established presbyopes with a moderate addition (+1.25 to +2D) wore both a single brand multifocal (MF) contact lens (Air Optix Aqua) and a monovision correction over separate randomized two-week wear periods. Despite most acuity measures being statistically better with monovision, the subjective ratings showed only a few significant differences between lens modalities and overall lens preference was not statistically significant. The authors conclude clinical vision measures are not adequate predictors of patient acceptance of MFs in real-world situations.
Esthesiometer Good for Central Cornea But Not for Conjunctiva
Our authors established good repeatabilty of the Cochet-Bonnet esthesiometer for central corneal measures (especially those repeated the same day). By contrast, the repeatability measures for inferior conjunctiva were poor and the authors caution in using the instrument for this purpose.
IOL Power Calculation With Corneas With Having Prior Refractive Surgery
In cataract surgery there is a challenge to figure out what power IOL to use in an eye that has prior PRK or LASIK, when pre-operative data (i.e. K readings) aren't available. An accepted correction for this is known as Saiki’s formula that was derived for LASIK surgery. It uses the posterior corneal power to estimate the presumptive pre-operative corneal power in selecting the IOL power. Our authors compared their new formula, specifically formulated for PRK patients, to Sakai/'s formula, and found that although they were similar (only a small statistically significant difference) the Sakai formula was more variable. Consequently, they caution against using the more variable Sakai formula for these IOL calculations.
LASIK Improves Stereopsis?
In a prospective interventional study of 80 eyes of 40 myopic patients in India, near (40cm) and intermediate (3m) distance stereopsis improved after LASIK surgery. The improvement was unrelated to degree of pre-myopic refractive error.
Aniseikonia Induced by Cataract Surgery
The authors report an initial increase in aniseikonia following cataract surgery consistent with the increased anisometropia. However, as anticipated, the second cataract surgery restored near presurgical anisometropia levels and was associated with better stereopsis. The amount of residual aniseikonia showed substantial variance and could not be predicted from the amount of induced anisometropia.
Microstrabismus and Global Stereopsis
Binocular depth discrimination is reduced in school-aged children with microstrabismus. The reduction is severe when testing with random dot stereograms (RDS) rather than with clinical tests containing visible contours (local stereopsis). Our authors found by increasing the angular size of the RDS stereoscopic stimuli, the stereoacuity of microstrabismic subjects was improved dramatically but not to the level of control participants. They assert that this supports the view that abnormal visual experience prevents the fine stereopsis mechanism from developing.
Role of Visual Motor Skills in Predicting Reading Ability
While visual motor skills play a small role in the acquisition of decoding skills in reading, along with phonological processes, the contribution is small and does not contribute to fluency once decoding skills have been controlled. In short, visual motor integration drops out of the prediction models once more reading and language specific skills are introduced. They conclude that a visual motor integration skill measure will not sufficiently determine if a child has a reading disability.
Simulated Hyperopia and Academic Performance
A relatively low level of simulated bilateral hyperopia (2.5D) impaired children's academic performance on a range of academic-related outcome measures. Sustained near work further exacerbated this effect. The authors acknowledge that to determine the impact of correcting low levels of hyperopia on academic performance in children will require a separate study.
Eyemovements Contribute to Foveal Crowding
Normal observers make more letter miscalls and are less likely to report the correct number of letters when reading long compared to short strings of acuity letters. The authors interpret these observations to indicate that, in addition to contour interaction, inaccurate eye movements contribute to the normal foveal crowding phenomenon.
Inflammation and Keratoconus?
Notwithstanding the presence of numerous inflammatory processes in keratoconus corneas and tears, the traditional classification for this disease as "non-inflammatory" is still used. Our author argues that although the classical criteria for an inflammatory disease are not found in keratoconus, its classification as a quasi-inflammatory (inflammation-related) disease is appropriate. He believes this perspective helps focus attention on the possibility of using anti-inflammatory therapeutic approaches in the treatment and management of keratoconus.
Two in One for Foreign Body and Scar Removal
Coexisting visually significant corneal scars and embedded stromal foreign bodies are usually managed by staged procedures; FB is removed first followed by management of the corneal scar. Here the authors report a quite successful single stage procedure using Femtosecond laser-assisted sutureless anterior lamellar keratoplasty (FALK). They report "To the best of our knowledge, this is the first case report of FALK and foreign body removal performed as a combined procedure with reasonable visual recovery."
Epilepsy and Migraine Systemic Drug Induces Angle Closure Glaucoma
Zonisamide is a relatively new sulfonamide-derivative indicated for epilepsy and used off-label for migraines. While angle closure secondary to systemic medications such as topiramate and other sulfonamide-derivatives is well documented, this is the first case of zonisamide-induced angle closure and myopic shift to be reported. With the increasing use of zonisamide, eye care providers should be aware of its sulfonamide-derivative properties and the risk of secondary angle closure.
Needing all the Tools for Diagnosis
An iris cyst can be a diagnostic challenge. In this case, slit lamp clinical examination revealed a nasal limbal perforation, and B-scan ultrasonography and anterior segment OCT collectively suggested an anterior subluxated lens. This was not the case. In fact it turned out to be a giant iris cyst that was successfully aspirated, leading to good acuity and no cyst recurrence after one year.
Tamoxifen Retinopathy Revealed by OCT
The optimal spectral domain optical coherence tomography (SD-OCT) scan technique depends on the ocular condition being imaged. The authors present a case of tamoxifen retinopathy that highlights the use of high density scanning. This case was initially misdiagnosed, but high density imaging showed the exact retinal layer of the deposits, making the diagnosis clear.