Picture of City Hall of Philadelphia

Introduction

Academy 2001 held in historic Philadelphia, looked over by William Penn from the top of City Hall, may have been down in attendance in light of September 11, but certainly not in spirit or quality. The AAO/WCO Joint Symposium on Vision Loss made for an interesting, inspiring mix of personalities and ideas. The Contact Lens Section was, as always, well represented, with over 120 papers and posters presented. FDA approval of both CibaVision Focus Night and Day and Bausch and Lomb PureVision lenses for 30 night continuous wear in 2001 generated much interest, with over 20 paper and posters on the topic.

Hypoxia

Corneal striae observed in low Dk EW.	Microcysts observed in low Dk EW.

2001 saw a resurgence in the number of papers and posters on corneal edema, with the signs and effects featuring strongly. The silicone hydrogels of course perform well, but while no soft toric options are available and some practitioners continue to fit low Dk hydrogels for EW, despite the benefits of silicone hydrogels, the topic is still hot. Topographic swelling was a popular theme and use of the Orbscan featured heavily.

The team at Pacific University found that corneal thickness increased uniformly (across an area measured by Orbscan) in response to overnight lens wear. The same group found that while the minimum figure for Dk/t to achieve no edema beyond that of the eye with no lens, appeared to be between 110 and 175, individual differences are a factor to be considered. Interestingly, there were no differences between powers of -1.00 and -6.00 within lens types. With the release of plus ranges from both companies, results of how the thicker plus lenses measure up will no doubt be available soon.

Inma Perez-Gomez and colleagues from Eurolens Research found that after 6 months of extended wear, corneal thickness differences were consistent with relative Dk/t, but there is a reduction in the posterior stromal cell density that does not appear to be related to Dk/t and may be related to other factors such as the mechanical presence of a lens on the eye.

Oxygen supply to the cornea in different lens combination piggyback systems was investigated by Florkey et al from the University of Ohio. The findings indicated that there was a higher mean oxygen uptake compared to air for PMMA compared to PMMA in combination with either balafilcon or Permalens in dynamic conditions (blinking). Interestingly, blinking did not in itself improve the oxygen supply to the cornea.

Watch out for an up and coming editorial on hypoxia in the next few months!

Clinical Performance

Corneal striae observed in low Dk EW.	Microcysts observed in low Dk EW.

As expected, much interest from our Ellerbrock audience was in the clinical performance of the lenses. This month's editorial, Clinical Performance and Observation: Lens Fitting, by Kathy Dumbleton from CCLR should answer a few questions and provide some helpful tips. Some of the information in the editorial is hot off the presses from a paper authored by Kathy, and presented by Robyn Chalmers in the excellent Monday afternoon Cornea and Contact Lens Section at the Academy.

Impressive long-term results from both Bausch & Lomb and Ciba Vision FDA studies and Noel Brennan's team in Australia were also presented. B&L reported that compared to low Dk EW, there are less microcysts and vascular signs in eyes wearing high Dk. They also found that silicone hydrogel lenses move more than hydrogels but there is no difference in lens deposit and surface wettability. Ciba Vision found that over 6 months of silicone hydrogel CW, corneal health of previously experienced soft lens wearers improves and with new wearers, only minimal signs occur. Noel's team found there was no increase in hypoxic signs such as microcysts, and in fact a decrease in limbal redness over 3 years of CW with silicone hydrogels.

Dryness and Comfort

Many papers and posters this year featured CL related dryness and techniques to observe the tear film and were very popular amongst practitioners. There was standing room only in the Ellerbrock session, "Fitting the Marginal Dry Eye Patient" by Urs Businger from Switzerland.

Robyn Chalmers presented findings that patients' self assessment of dry eye is more efficient than non-directed doctor diagnosis in identifying subjects with increased symptoms late in the day, and found different patterns of symptom reporting for contact lens wearers and non lens wearers; Don Korb et al presented some interesting information on the "lid wiper" phenomenon (marginal tarsal conjunctiva of the superior lid), finding a correlation between staining of the lid wiper (upper lid) and dryness symptoms in contact lens wearers; Anthony Tran et al found reduced tear meniscus in SH lens wear, similar to hydrogel lens wear and lower than in RGP lens wear, postulating this to be due to tear absorption by the soft lenses.

John McNally presented some interesting information on dryness with silicone hydrogel CW, finding that the symptoms of dryness were less frequent and patients were less likely to report dryness as the reason for discontinuing lens wear or for unscheduled lens removals compared to 6NEW of disposable hydrogels.


Deposits

High level of lipid deposit, seen in small percentage of silicone hydrogel lens wearers.

Lipid tends to be the major deposition problem with any silicone containing lens. Fiona Lydon and Brian Tighe found with both types of silicone hydrogel lenses no differences between 6NEW or 30NCW schedules, but individual patients consistently showed front to back surface and left to right eye variability with both lens types. They also found that while lipid profiles were patient dependent, they were also driven by material and surface characteristics.

An interesting paper, although not on silicone hydrogels specifically, was presented by Michel Guillon, confirming contact lenses modify the lipid layer of the tear film, but that with etafilcon A, this is not due to selective absorption of lipids.

Adverse Events

Typical fluoroscein staining observed in Superior Epithelial Arcuate Lesions.	Local Contact Lens Papillary Conjunctivitis.

Debbie Sweeney presented a paper authored by Renee DuToit on compliance, or should I say non-compliance. Relatively high rates of non-compliance were reported, but we always assume that they are probably even higher than this. A higher prevalence of inflammatory events was found for patients with moderate to high reported non-compliance.

In the same session, Noel Brennan presented a paper comparing the occurrence of adverse events in extended wear for different age groups, finding younger patients more susceptible despite no differences in compliance between the age groups. Anecdotally, it has been reported that young males are more prone to adverse events, although this may be linked to smoking, which has been found to be a risk factor in some studies.

Hoehne and Sickenberger found that there was no difference between bacterial colonization of either silicone hydrogel lens types worn up to 28 nights continuously or an increase in bacteria over this time with either lens type.

B&L combined the results of 27 studies and found no events of MK in over 4.700 patients accumulating over 2,200 patient years of data. Mounting a properly controlled scientific study of the prevalence or incidence of MK with High Dk soft lens wear is a huge, but very important task. It requires a very large patient sample to have worn lenses for at least a year. CCLR/CCLRU/CRCERT/LVPEI are attempting to mount such a study with our national and international colleagues as a matter of some urgency.

With the relatively high rates of mechanical adverse events, such as SEALs, ability to measure and/or grade the thickness of the post lens tear film has great significance. The difficulty of assessing the dynamics behind the lens, particularly during blinking makes this area of research especially exciting and groundbreaking.

Noel Brennan's team found grading of the PLTF using specular reflection to be comparable to fluorotometry monitoring of the flushing of 0.1% FITC dextran (high molecular weight fluorescent dye), thus suggesting it as a clinical method of evaluating flow of tears behind a contact lens.

Interferometry techniques were utilized by Nichols and King-Smith from The Ohio State University to assess the pre and post lens tear film in balafilcon lens wear, finding there was considerably larger variability in the pre compared to post lens tear film.

Lydon, Benning and Tighe from Aston Biomaterials Research Unit presented data on the frictional behavior of contact lenses, an exciting area not previously reported on. Modeling the frictional relationship between the lens and the eye, they found that front surface dehydration led to an increase in start up friction between the lens and the eyelid. We look forward to further work particularly relating to mucin balls, lens binding and end of day dryness.

Therapeutic Uses

Research is also encompassing other exciting applications of silicone hydrogels such as piggyback lens and drug release systems.

Kalgard, Jones and Moresoli from the University of Waterloo investigated the uptake/release of Ciprofloxacin (Ciloxan) by both silicone hydrogel lens types and conventional hydrogel lenses. They found that no difference between either silicone hydrogel lens types and conventional lenses in the uptake and statistically, but not clinically significant, less release of the drug, concluding that silicone hydrogel materials are a superior bandage/therapeutic lens choice compared to conventional hydrogel materials.

Conclusion

"Original Eye Doctors of Rock"