Research Update

Research Update Issue 3

March 2017  

Welcome to IACLE’s monthly research update
Welcome to Research Update, a new resource available to IACLE and BCLA members to support your teaching and practice. Each month we will send you a summary of some of the interesting findings appearing in peer-reviewed journals that month. Our aim is to help you keep up to date with the latest contact lens and anterior eye research, and to locate articles when you want to know more about a particular topic.
More information on Research Update and how to use it in your contact lens teaching here. Access archived issues via Member Login under Research.
Issue 3 – March 2017
The effects of myopia correction on binocular vision are an area of interest for all eye care practitioners and for researchers. In this issue, we take a look at how orthokeratology in young adults, and soft multifocals in children, affect binocular vision function.
In other studies, a research group in Australia investigates spherical aberrations induced by multifocals and their impact on visual performance. We report on a study of anterior and posterior corneal astigmatism of normal and keratoconic eyes. One paper addresses a practical issue of fluorescein volumes and their effect on tear film stability. And a group in Thailand assesses knowledge and behavior in cosmetic CL wearers, and the presence of amoebae in lenses. Finally we also include a study that supports previous work on conjunctival microcirculation in response to CL wear.

Happy reading!

The IACLE Education Team
Journals reviewed in this issue  

  Contact Lens & Anterior Eye Articles In Press
  Optometry & Vision Science 94:394:2
  Cornea 36:4
  Eye & Contact Lens 43:2

Ortho-K vs soft lens wear
To compare near point binocular vision function of young adult myopes wearing orthokeratology (OK) lenses to single-vision soft disposable contact lens (SCL) wearers, Gifford et al retrospectively analysed clinical records of 17 OK wearers (aged 18-30 years). Compared to matched SCL wearers, the OK group were significantly more exophoric and had better accommodation accuracy. More SCL wearers had high lags of accommodation and esophoria than OK wearers. Young adult myopes with specific binocular vision disorders may benefit from OK wear in comparison to single-vision SCL wear.

Cont Lens Anterior Eye 2017. Click here for full text


Accommodation and phoria with multifocals
In this crossover study Gong et al aimed to determine the effect of multifocal contact lenses (MFCLs) on accommodation and phoria in children. Accommodative responses and phorias of 16 myopic children wearing single-vision (SV) and MFCLs (+2.50D center-distance add) were measured at four distances (>3m, 100cm, 40cm, 25cm). The authors found a small decrease in high and low illumination visual acuity, and contrast sensitivity with multifocals. Subjects were more exophoric with multifocals and had decreased accommodative responses at increasing accommodative demands.

Optom Vis Sci 2017;94:3 353-360. Click here for abstract


Spherical aberration and multifocal performance
Fedtke et al investigated the impact of the primary (PSA) and secondary (SSA) spherical aberration on visual performance in 17 presbyopes wearing seven commercial lens types (four center-near MFCLs, one center-distance MFCL, one bifocal, one single-vision control). All test lenses induced significant amounts of PSA. Compared to the control, distance high- and low-contrast visual acuities, and contrast sensitivity, were significantly reduced with all test lenses. The findings may prove useful when designing new or optimizing existing MFCLs.

Optom Vis Sci 2017;94:2 197-207. Click here for abstract


Corneal surfaces in keratoconic eyes
To evaluate and compare power and axis orientation of anterior and posterior astigmatism, Shajari et al retrospectively examined 861 eyes of 494 patients with keratoconus, and 256 eyes of 256 healthy individuals. Magnitude of corneal astigmatism was 3.47±2.10D on the anterior surface and 0.69±0.40D on the posterior surface in keratoconic eyes. In eyes with keratoconus, posterior axis alignment of corneal astigmatism is in line with alignment of the anterior surface in a majority of cases.

Cornea 2017;36:4 457-462. Click here for abstract


Less is more for fluorescein volume
Mooi et al compared tear film break-up time measurements of 41 subjects obtained non-invasively (NIBUT), with those measured following minimal (mTBUT) and conventional volumes (TBUT) of fluorescein instillation. Both NIBUT and mTBUT measurements were significantly longer than TBUT, while there were no significant differences between NIBUT and mTBUT. Both NIBUT and mTBUT measurements demonstrated a larger spread than those of TBUT, although NIBUT and mTBUT did not differ significantly. This suggests that minimising instilled volumes can reduce the impact of fluorescein on clinical measurements.

Cont Lens Anterior Eye. Click here for full text


Cosmetic lenses: knowledge, behavior and contamination
Mahittikorn et al surveyed 100 cosmetic contact lens (CCL) wearers to assess their knowledge and behavior of lens care. Their lenses were also tested for free-living amoeba (FLA) strains. The CCL wearers generally showed a moderate (47%) or good (35%) level of knowledge, and good (51%) or excellent (40%) use of CCLs. Two CCL samples were positive for Acanthamoeba genotype T3 (wearer used saline for treating lenses) or Vahlkampfia (wearer used CCL while swimming). The public should be aware of CCL contaminated with potentially pathogenic FLA that can cause keratitis.

Eye Contact Lens 2017;43:2 81-88. Click here for abstract


Conjunctival microcirculation in contact lens wear
Chen et al determined blood flow velocities and corresponding vessel diameters to characterize the response of the bulbar conjunctival microvasculature to contact lens wear. They used an adapted slit lamp to image the temporal bulbar conjunctiva of 22 healthy subjects before and after 6h of soft CL wear. Average blood flow velocity increased from 0.51+0.20 to 0.65+0.22 mm/sec after 6h of wear. Blood flow velocity distribution showed a velocity increase that correlated with vessel diameter increase from baseline.

Eye Contact Lens 2017;43:2 95-99. Click here for abstract

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