The annual American Academy of Optometry meeting is an opportunity for the best minds in optometry to get together and share their research.
In case you couldn’t make it out to Seattle for this year’s meeting, here are just a few of the studies focused on cornea and contact lens care that were presented at Academy 2013 last month.
1. Corneal thickness and volume help identify keratoconus suspects. In a study of 74 patients (22 eyes with keratoconus, 22 eyes with suspected keratoconus and 30 normal eyes), five parameters were examined: anterior curvature, posterior curvature, corneal thickness, anterior chamber depth and corneal volume.
The keratoconic eyes differed from the normals in every parameter, but only differences between the corneal volume and corneal thickness at the center, apex and thinnest point were significant between keratoconus suspects and normal eyes.
This suggests that examining these parameters can help distinguish keratoconus suspects from normal eyes.
Gordon-Shaag A, Millodot M, Salhab I, et al. Anterior chamber characteristics in normal, keratoconus suspect and keratoconic eyes. Poster session presented at AAO 2013.
2. Overcoming common barriers may enhance multifocal lens dispensing. In a study of 102 eye care practitioners, respondents reported increased chair time, lack of available trial lenses and limitation in power range as the most common barriers in dispensing multifocal lenses. Among patients, lack of awareness was the highest barrier.
The major motivators were professional satisfaction and better business proposition, while availability of trials and correct patient selection were reported as the most common enablers.
The study suggests that limitations in power range, as well as the general lack of patient awareness of these lenses must be addressed to increase multifocal dispensing. Also, practitioners who have trial lenses readily available may be more motivated to prescribe multifocal lenses.
Thite N, Shah U, Mehta J, Jurkus JM. Barriers, motivators and enablers for dispensing multifocal contact lenses. Poster session presented at AAO 2013.
3. Contact lenses using molecular imprinting may prove useful in combating ocular infection. A study examined the drug release characteristics and antimicrobial abilities of novel silicone hydrogel materials using poly-hydoxylethyl methacrylate trisiloxylsilane.
The antimicrobial abilities of these novel lenses, which were imprinted with ciprofloxacin 0.3%, were tested in vitro against P. aeruginosa over the course of three days.
The imprinting process extended the release times of ciprofloxacin vs. non-imprinted controls. No viable bacteria were recovered, suggesting this technology may be useful in treating and preventing ocular infections. In vivo performance is being studied in an animal model.
Hui A, Willcox M, Jones L. In vitro evaluation of antimicrobial activity of novel ciprofloxacin releasing silicone hydrogels. Poster session presented at AAO 2013.
4. Soft lens diameter impacts the oxygenation of both the central and peripheral cornea. A study of 15 subjects fitted with three diameters (13.0, 14.0, 15.0mm) of hydrogel lenses examined oxygen uptake of the central and peripheral cornea for each eye and location after five minutes of lens wear vs. a normal, open eye. The uptake rate of each lens diameter was divided by the rates of the normal eye in the same location.
Both the central and peripheral locations showed a significant difference in oxygen uptake.
Significant differences in oxygen uptake were also found between lens diameters, as the corneal oxygen uptake rates (4.59 for the 13mm lens, 4.99 for the 14mm lens and 5.03 for the 15mm lens) demonstrated an increase with increasing lens diameter.
Bastian P, Fink BA, Mitchell GL. Oxygen demands of the central & peripheral cornea associated with the wear of hydrogel contact lenses. Poster session presented at AAO 2013.
5. Center-distance multifocal soft lenses demonstrate a consistent change in peripheral defocus, regardless of the amount of myopia. Peripheral refractive error OD was measured in 25 subjects with spherical soft contact lens-correct refractive error of -0.50 to -6.00 DS.
The subjects were examined while wearing an aspheric single vision soft contact lens, a center-distance multifocal soft contact lens with a +2.50D add and while uncorrected.
A lower minus power in the aspheric single vision modality demonstrated a greater peripheral hyperopic shift than higher power lenses. The multifocal soft contact lenses displayed a consistent peripheral defocus profile across all powers tested.
If myopic peripheral defocus is capable of slowing axial growth in children, center-distance multifocal soft contact lenses are a favorable modality due to their consistent change in peripheral defocus.
Kramer CE, Bernsten DA. The effect of sphere and multifocal soft contact lens power on peripheral defocus. Poster session presented at AAO 2013.
6. Soft keratoconus contact lenses may be viable in rehabilitating corneal warpage. Keratoconus soft lenses offer improved comfort over GPs, while offering adequate visual acuity in many patients with irregular corneas.
A case report examined the capability of these lenses to rehabilitate induced corneal warpage. A 28-year-old patient with a 20-year history of wearing GP lenses was re-fit into soft kerotoconus lenses.
After one month, the subject reported increased lens movement on blink without any reduction in acuity. Results suggest that during the life span (one month) of one pair of soft KC lenses, the cornea is capable of improving without the need to discontinue lens wear.
Following rehabilitation, the patient can be re-fit into a more appropriate lens.
Schlotthauer N. Utilizing keratoconus designed soft contact lenses to rehabilitate corneal warpage. Poster session presented at AAO 2013.
7. A novel ellipto-conical corneal model may improve ocular topography. While soft lenses are widely worn, factors governing their fitting characteristics are still not well understood. This study used a computer model to better understand the fitting characteristics of soft lenses.
The ellipto-conical corneal model was coupled with corneoscleral topography data obtained in a previous study, and was used to calculate lens edge strain as a predictor of lens tightness.
When compared to a simple elliptical model, the ellipto-conical model demonstrated a closer correlation with actual measurements of corneal sagittal height.
Young G, Hall LA, Wolffsohn JS. Mathematical model evaluation of soft contact lens fit. Poster session presented at AAO 2013.
8. The Contact Lens Risk Survey (CLRS) may be a good tool for educating patients on risky contact lens behavior. The CLRS, which assesses 58 patient behaviors regarding contact lens wear and care, was given to 184 subjects, aged 18-25, at five non-clinical locations in the US in autumn 2011. The following summer (2012), a separate group of 45 subjects, aged 18-21, were surveyed.
The CLRS demonstrated good repeatability, as most items scored moderate or better agreement. The researchers believe that the differences between the two studies may be due to the temporal factors, as one the surveys were administered during two different seasons.
The study suggests further education is required to inform patients on ways to lower risks of adverse events.
Lam DY, Richdale K, Chalmers RL, Mitchell GL, Kinoshita BT, Jansen ME, et al. Repeatability of the contact lens risk survey. Poster session presented at AAO 2013.
9. There is a relationship between tear osmolarity and ocular allergy symptoms. Lindsay A. Sicks et al. conducted a study among 18- to 40-year-old subjects with no known anterior segment complications, to examine the relationship between tear osmolarity, ocular allergic symptoms and environmental pollen counts.
Symptoms were evaluated using the OSDI survey, and local pollen counts were recorded each day tear osmolarity was tested.
Over the course of three weeks, a significant inverse relationship between tear osmolarity and pollen levels was seen—as the pollen levels increased, tear osmolarity decreased.
An increase in reflex tearing due to ocular allergens may be responsible for the decrease in tear osmolarity, as the aqueous component of the tear film increases.
Sicks LA, Langr K, Kuntz KR, Budge B, Johnson C. Relationship between tear osmolarity and ocular allergic symptomology. Poster session presented at AAO 2013.
10. A topographer using Hartmann’s principle may be a valuable optometric instrument. Researchers compared a Medmont E-300 topographer to a new prototype using Hartmann’s principle, to measure the apical radius and the numerical eccentricity of nine manufactured surfaces made of PMMA, resembling sample normal human corneal shape parameters.
Each PMMA surface tested had varying apical radii and numerical eccentricities.
There was no statistically significant difference in any measurements between the two modalities, with the prototype Hartmann device showing comparable results to the Medmont E-300.
The Hartmann device may provide optometrists with a useful tool in the future.
Hall JQ, Spors F, Mejia Y, Egan DJ, McNaughton L, Shen J. A comparison of placido and Hartmann topography measurements. Poster session presented at AAO 2013.
Each year, the AAO annual meeting highlights ground-breaking research that improves the quality of clinical care and product development.
The above studies represent just a fraction of the many presentations on display this year. Look for next year’s meeting in Denver, November 12-15, 2014!
