Alisa Sivak, MA, DipEd

Alisa assists the Centre for Contact Lens Research by writing and editing publications, reports, grant applications, and educational communications.

The following is part 2 of a synopsis of the AAO meeting. Part 1 can be found here

Physiological effects

Noel Brennan (Brennan Consultants) set out to model oxygen consumption across the corneal profile underneath powered contact lenses, comparing these figures to the information provided by Dk/t values alone. Using colour-coded maps to illustrate the profile of oxygen consumption Brennan showed how different contact lenses affect the cornea taking into account a variety of conditions, including open and closed eye and wear schedule. Results illustrated the benefits of silicone hydrogel lenses for both DW and CW.

Using a novel fiber optic spectrometer system, James Walsh (Dublin Institute of Technology) and colleagues found that silicone hydrogel lenses have greater UVR blocking capacity at the thicker edge region. This cut UVR exposure by 25% compared to lenses with no UVR blocker, which were transparent across the entire width of the lens. 

Trefford Simpson and colleagues (CCLR) reported that bulbar redness and temperature – measured simultaneously and continuously – both increase immediately following the insertion of a contact lens, regardless of lens material. Unadapted wearers had a more transient response than adapted wearers, indicating that this response changes during adaptation to lens wear. This information may be useful in defining when adaptation to lens wear has occurred physiologically. 

Cristina Schnider compared the overnight corneal swelling and daytime deswelling response to lotrafilcon A, balafilcon A and senofilcon A lenses compared to that with a hydrogel lens and no lens wear. The silicone hydrogel lenses swelled to the same degree as an eye with no lens - statistically less than that induced by the hydrogel lens.

Kathy Dumbleton and colleagues (CCLR) compared central and mid-peripheral corneal thickness in the eyes of 100 participants wearing low- and high-Dk lenses over a 6-month period. This study took into account the cumulative effects of overnight and daytime lens wear. Long-term EW of low-Dk lenses induced a 3.7% increase in central thickness and a 2.8’% increase in mid-peripheral thickness, whereas swelling was lower with the high-Dk lenses (1.1% and 1.4 respectively) and took longer to occur.

Amir Moezzi et al. (CCLR) compared central corneal swelling after 8 hours of sleep in participants wearing a comfilcon A lens in 1 eye and a lotrafilcon A lens in the other eye, and with comfilcon A in 1 eye and no lens in the other. There was no significant difference in corneal swelling when both lenses were worn. Corneal swelling was significantly greater in comfilcon A wearing eyes compared to non-lens wearing eyes.

Meng Lin (UC Berkely School of Optometry) and colleagues discussed the appearance of a ‘conjunctival epithelial flap’ (CEF) which occurs with CW of silicone hydrogel lenses.  This team found that the incidence rate of this flap was 3% with DW – significantly lower than that observed by Lofstrom and Kruse with CW. 

Studies have shown that a change in refractive error can occur in patients who switch from conventional to silicone hydrogel lenses [see Expect the Unexpected-Refitting from Conventional Hydrogels].  Denise Burns-LeGros and colleagues (Nova Southeastern University College of Optometry) refit current HEMA lens wearers with either lotrafilcon A lenses or a new pair of their habitual lenses. Results showed that both groups of subjects experienced no changes in refractive error over 1 month.

Adverse Events

Referring to the results of a 3-year, multi-site clinical trial of lotrafilcon A lenses, Sally Dillehay (CIBA Vision) and colleagues reported that the frequency of adverse and inflammatory events may be lower in practice than previously reported. Out of 317 patients, lens-related adverse events were reported in less than 3% of eyes; inflammatory events were found in 2.7% of eyes; and mechanical events were found in less than 0.2% of eyes. There were no reports of MK. 
 
Loretta Szczotka-Flynn (Case Western Reserve University) and colleagues reported on the probability of remaining free of significant corneal infiltrates over 3 years of CW with lotrafilcon A lenses. Three hundred and seventeen patients were fit with lotrafilcon A lenses for CW and followed for 3 years, with outcome measures including infiltrative events of grade 3 or 4. Only first occurrences were considered.  Five infiltrates (grade 3-4 ) were found within the first year, none in the second year and 3 in the third year. Results showed a 98.2% probability of remaining free of significant corneal infiltrates for up to 2 years with CW of lotrafilcon A lenses, and 96.9% after 3 years.

Fiona Stapleton (Vision CRC) and colleagues reported the results of a prospective study of contact lens-related MK over 1 year in Australia. In 307 cases of contact lens-related MK, there were no significant differences in incidence between EW of silicone hydrogels and conventional hydrogels. EW of contact lenses is associated with a higher risk than DW which is, in turn, associated with a higher risk than DD wear. The annualized incidence of all contact lens-related MK was 5.1 per 10,000 wearers.     

Philip Morgan (Eurolens Research) and colleagues reported on the incidence, morbidity and risk factors leading to keratitis among contact lens wearers in a 12-month, prospective, hospital-based epidemiological study. The annual incidence (cases per 10,000 wearers) of EW of conventional hydrogels (96.4) was much higher than that with silicone hydrogels (19.8): silicone hydrogels have a 5x lower risk of severe keratitis for EW compared with hydrogel lenses. Incidence with EW of both hydrogel and silicone hydrogels was significantly higher than with DW of GP lenses (2.9), daily disposable (4.9), DW hydrogel (6.4), DW silicone hydrogel (0) and EW of GP lenses (0). Other significant risk factors were gender, smoking, relevant health problems and season.   

Johann Ohly and Peter Russo (Loyola University Medical Centre) described a case of P. aeruginosa MK in a 29-year-old silicone hydrogel-wearing resident at LUMC. Onset of symptoms (progressive pain, redness and blurred vision) occurred upon awakening after 24 hours of lens wear and 2 days before presenting for care. This patient exhibited several risk factors for MK (occasional overnight wear with dryness upon awakening, poor lens care hygiene, and smoking). In addition, the pattern of antibiotic resistance of the P. aeruginosa strain was identical to a strain previously identified at this hospital, indicating that exposure to this pathogen may have been a significant risk factor.

Bandage Lenses and Piggyback Combinations

Clare O’Donnel and colleagues (University of Manchester) reported that lotrafilcon B and A lenses work equally well as bandage lenses when it comes to clinical results and subjective symptoms. The lotrafilcon B lenses were associated with a lower score for ‘foreign body sensation’ and higher levels of protein deposits.

Raquel Gil-Cazorla and colleagues (Hospital Oftalmológico Internacional de Madrid) reported that lotrafilcon A and Poly-2-Hydroxietilmetacrilate-cometacrilate glycerol (Equis 60) lenses performed equally well when used as post-LASEK bandage lenses.  Five days post-surgery, the status of the epithelium was statistically better in the eyes wearing silicone hydrogel lenses.

Peter Russo and colleagues (Loyola University Medical Center) reported success in fitting dry eye patients with lotrafilcon A lenses, which were worn continuously with weekly removal for cleaning. Results showed significant improvements in visual acuity and subjective symptoms, with no adverse reactions.

Charles Dominguez and colleagues (Jules Stein Eye Institute) presented the case of a 55-year-old patient who was successfully fit with a piggyback GP-silicone hydrogel lens combination to treat decompensating vertical heterophoria (VH). Fitting with a GP lens is an uncommon technique for addressing VH, but one that can significantly improve functional vision and quality of life for patients unable to adapt to spectacle prism. Piggybacking the GP lens over a silicone hydrogel made lens wear much more tolerable for this patient, who had developed corneal desiccation and lens intolerance with the GP lens alone.

Alan Kwok (New England College of Optometry) and colleagues (Boston University School of Medicine) presented a case in which a piggyback GP-silicone hydrogel combination worked well to address the needs of a 9-year-old patient who had sustained a corneal laceration leading to a ruptured globe and insult to the lenticular capsule. This combination maintained patient comfort while correcting a large amount of refractive error and irregular astigmatism resulting from the injury.