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| Picture of Fort Lauderdale, Florida, USA |
Introduction
It was the diamond anniversary of the Association for Research
in Vision and Ophthalmology conference that was held in Fort Lauderdale
and celebrated by more than 8000 attendees. 75 years of ARVO were
marked by an outstanding collection of scientific presentations,
workshops, symposia and exhibits. Of the over 5000 abstracts reviewed,
54 were contact lens related, and of those 54 about 20% pertained
to silicone-hydrogel lenses. Certainly, the quality of these presentations
was light-years ahead of the quantity!
Presentations
Complications with Extended Wear
Debbie Sweeney from the Cooperative Research Centre for Eye Research & Technology
(CRCERT) at the University of New South Wales (USW), Sydney, Australia,
presented a paper on the factors associated with Contact Lens Induced
Peripheral Ulcers (CLPU). Sweeney and her team observed subjects
who participated in extended wear (EW) trials, having worn 6-night
weekly replacement low Dk or 30-night monthly replacement high
Dk soft lenses. They found that CLPU may be associated with an
array of factors, including ionic lens material, lens contamination
with gram-negative bacteria, tighter fitting high Dk lenses, higher
levels of mucin balls, subjective symptoms of tearing and lower
levels of conjunctival redness. Factors that were not associated
with CLPU in this analysis were age and sex.
Katie Edwards of the Cornea & Contact Lens Research Unit (CCLRU)
performed a retrospective study investigating how long Silicone-Hydrogel
(SH) lens wear was discontinued due to Adverse Events (AE). Participants
of the trial had worn the lenses on 30-night EW schedule. She found
that Corneal Inflammatory Events (CIE) [including CLPU, Contact
Lens Related Red Eye (CLARE) and Infiltrative Keratitis (IK)] caused
longer durations of discontinuation than Mechanical Events (ME)
[including Superior Epithelial Arcuate Lesion (SEAL) and Corneal
Erosion (CE)]. She did not find any differences in length of discontinuation
between different types of CIEs nor between different types of
MEs. The average duration of discontinuation was 15 days with CIEs,
and 5 days with MEs, according to Edward’s poster. The length
of discontinuation with CIEs was correlated with severity rating
of the event, density of infiltrates and depth of corneal staining.
Curtis McKenney from CIBA Vision presented a poster about wearing
schedule influencing the rate of CIEs among Lotrafilcon A (Focus
Night & Day) (FND) lens wearers. According to McKenney the
annual incidence of endpoint corneal inflammatory infiltrative
events, defined as corneal infiltrates of equal to or greater than
grade 3 or infiltrates of any grade with overlying corneal staining,
ranged from 3.4% to 5.0% for the EW modalities. Wearing schedules
were not correlated with the annual incidence rate. In the DW studies
the annual incidence was lower. McKenney concluded that patient
factors should be considered when choosing the right wear schedule
for SH lenses.
John McNally from CIBA Vision and his team tried to shed light
on risk factors and reasons associated with discontinuation of
30N EW. McNally explored risk factors such as gender, age, smoking,
previous lens experience and wearing schedule, history of contact
lens complications, lens power and visual acuity. The background
information was collected at baseline of a multi-centre post approval
evaluation of FND lenses. Participants of the study cited later
discomfort, poor vision, late day dryness and inability to achieve
30N EW as reasons for discontinuation. The conclusion of this presentation
was that risk factors reported at baseline can indicate a wearer’s
chance of success with 30N EW.
Health Benefits with High Dk Lenses
Bill Long presented the results of a 6-month trial with high Dk
SH lenses that he and a team of researchers from several universities
in the USA had conducted. They reported on changes in nine biomicroscopy
signs and ten subjective symptoms. The clinical signs with the
greatest improvements among adapted wearers were bulbar and limbal
redness. Both neophytes and experienced wearers had less frequent
tearing or watering eyes with SH lenses. According to Long, improvements
may be found for a wide range of clinical signs and subjective
symptoms, and the improved supply of oxygen for the cornea may
benefit both ocular health and patient satisfaction.
Ocular Surface Sensitivity
Blanka Golebiowski from the CRCERT investigated ocular surface
sensitivity following refitting low Dk EW lens wearers with high
Dk EW. Measurements of central corneal and conjunctival sensitivity
were performed while participants were still on low Dk EW, then
four times over a period of 6 months with high Dk SH lens wear.
Against expectations Golebiowski measured a decrease rather than
an increase in central corneal sensitivity over the period of observation
and no changes in conjunctival sensitivity over the whole period.
Golebiowski concluded that factors other than oxygen supply must
be involved in influencing the sensitivity of the ocular surface.
Lens Comfort
Initial lens comfort was the subject of a poster presented by Rènée
Du Toit et al from the CCLRU. In a single-masked study Du Toit
investigated initial lens comfort with different soft lens types,
including the two marketed SH lens types, FND and PureVision (PV).
According to Du Toit there was no difference in initial comfort
between the different soft lenses. Silsoft lenses served as a positive
control and turned out to be consistently less comfortable than
all other soft lenses in the trial. Du Toit suggested that the
perception of lens comfort with soft lenses during the first few
moments of lens wear depends on factors other than lens design
or material.
Biochemistry Perspectives
The attachment of Acanthamoeba to different SH lens surfaces, with
and without surface treatment, was investigated by Alan Tomlinson
from the Department of Vision Sciences of the Glasgow Caledonian
University of Glasgow, Scotland. Etafilcon A (Acuvue) was used
as control. According to Tomlinson’s results, the amoebal
attachment to the marketed FND lens may be attributed to the surface
treatment process.
Pseudomonas aeruginosa infection and the molecular analysis of
inflammatory mediators in lotrafilcon A contact lens wearing rats
was the subject of a poster presented by Elizabeth Szliter from
the Anatomy/Cell Biology Department of the Wayne State University
of medic, Detroit, Michigan. Szliter developed an in-vivo animal
model for experimental EW of SH lenses to investigate Pseudomonas
infection in the absence of corneal trauma and to detect corneal
cytokine and chemokine gene expression. She concluded that this
model will allow further testing and analysis of bacterial keratitis
associated with CL wear.
Michelle Senchyna et al from the Centre for Contact Lens Research
(CCLR) of the School of Optometry, University of Waterloo, Canada,
presented a poster on the influence of a H2O2-based versus a polyhexanide-based
Multi Purpose Solution (MPS) in controlling both quantity and conformation
of lysozyme deposited on PV and FND SH lenses. She found that,
no matter what care regimen was used, a significant difference
existed regarding the amount of deposited lysozyme and regarding
the degree to which the lysozyme was denatured between PV and FND,
with PV showing significantly more lysozyme deposited and a higher
percentage of denatured lysozyme than FND.
SH in Piggy Back Systems
Hypoxic responses to RGP + SH combination contact lens systems
was studied by Lindsay Florkey from the Ohio State University College
of Optometry, Columbus, Ohio. Corneal oxygen uptake rates were
measured with several piggy back systems, using balafilcon A lenses
and RGP lenses of different Dk values and thicknesses, and with
RGP lenses alone. Results of the study were that the addition of
the SH lens did not increase corneal hypoxia significantly when
measured statically. When blinking was taken into consideration
(dynamic) hypoxia was reduced in a system with a thinner but lower
Dk RGP lens which Florkey attributed to differences in the lid-lens
interaction. The thicker but higher-Dk RGP lens caused less hypoxia
with and without the SH lens on top, indicating a possible reservoir-effect,
according to Florkey.
Conclusion
These SH presentations of this year’s ARVO meeting are an
excellent demonstration for the wide range of research that is
currently performed concerning SH lenses and extended wear.. Bright
prospects for ARVO 2004!
August 2003
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Synopsis | 
Simone
Bayer, staatl gepr AO, AOM