Contact Lens Highlights From Arvo
Studies presented at this year’s Association for Research in Vision and Ophthalmology (ARVO) could have a significant effect on your everyday contact lens practice. Research explored new theories of dry eye and corneal infiltrates, novel uses for RGPs, the rise in ortho-k interest and the latest on which patients can tolerate extended wear lenses. Here are some of the highlights.
Dry Eye and Corneal Complications
In a study that could have far-reaching implications on corneal research, investigators at Casey Eye Institute in Portland looked at long-term changes in lacrimal gland gene expression following corneal trauma.’ They have previously reported alterations in lacrimal gland gene expression in mice using gene arrays following corneal trauma after 24 hours. The study, when extended to 15 days, found three different expressions in gene arrays using a two-color fluorometric technique. Initially down regulation predominated. The results revealed persistent changes in gene expression in the lacrimal gland following trauma to the cornea. This supports the important hypothesis that a corneal feedback mechanism exists and that stress to the cornea unfavorably modifies lacrimal gland function. It also may help to explain some aspects of altered lacrimal gland function and dry eye that occur following corneal surgery, contact lens wear and even blepharitis.
The Schirmer test appears to be a good way of determining the underlying cause of keratoconjunctivitis sicca (KCS) in chronic blepharitis patients. In an attempt to assess tear film parameters associated with KCS in patients with chronic blepharitis, doctors at the University of Texas Southwestern Medical Center in Dallas classified 24 patients with various forms of chronic blepharitis into three groups: hyper-evaporative, hypo-secretory and combined mechanism KCS.’ Investigators assessed tear turnover, tear volume, tear flow, Schirmer test, ocular evaporation and meibomian gland dropout. Remarkably, the Schirmer test was the most positively correlated test with the clinical impression of the type of KCS. The hypo-secretory group had the lowest values. Decreasing tear flow with age was not an unexpected outcome. The clinical impression of the hyper-evaporative group based on difficulty expressing gland secretions and their turbidity correlated well with meibomian gland dropout but not excessive tear evaporation.
The surface treatment process applied to lotrafilcon A lenses may be responsible for increased Acanthamoeba attachment to silicone hydrogel lenses. Doctors at Glasgow Caledonia University in Glasgow, U.K., and the Applied Vision Research Centre, London, compared the attachment rates of Acanthamoeba to five different types of lenses: a commercially available (surface treatment) lotrafilcon A lens (CIBA Focus Night & Day), a lotrafilcon A lens prior to surface treatment, a lotrafilcon A lens with a hydrogel coating surface treatment, a balafilcon A lens (Bausch & Lomb PureVision) silicone hydrogel lens and a conventional hydrogel lens (Vistakon Acuvue).’ They found no significant difference in attachment rates among the commercially available surface treated lotrafilcon A lens, the hydrogel coated lens and the balafilcon A lens. However, attachment to all three was significantly higher than the untreated lotrafilcon A lens and the conventional hydrogel lens. The study concluded commercial treatment and hydrogel coating may induce an increase in Acanthamoeba attachment. (For more on this study, see Page 6).
Today’s RGPs
Researchers at Moorfields Eye Hospital in London set out to assess the effectiveness of rigid gas permeable scleral contact lenses (RGPSCL) used in patients with corneal exposure secondary to eyelid malposition.4 They retrospectively reviewed the records of 12 patients with 15 eyes fitted for with RGPSCLs for eyelid malposition associated with corneal exposure. One eye had ptosis, 11 eyes had lagophthalmos, two had entropion and another had trichiasis. Additionally, five eyes had nerve palsy, four eyes had myopathic ptosis, two eyes had post-radiation keratoconjunctival scarring, one eye had third nerve palsy and one eye had traumatic lid avulsion. Each eye had undergone a mean of two eyelid operations before the fitting. The lenses were well-tolerated, safe and effective, the study concluded.
Patients wearing bifocal RGP contact lenses may be at risk for increasing higher order aberrations. Investigators at Osaka University Graduate School of Medicine in Suita, Japan, compared bifocal RGPs with monofocal contact lenses in 10 presbyopic eyes of five patients.’ Mean astigmatic value was -0.98D. The total higher order aberrations with the monofocal’ was significantly lower than that produced by the bifocals, the study found, and the aberrations increased in correlation with higher add power lenses. Researchers speculated that the increase in coma-like aberration associated with bifocal contact lenses may be due to the decentration of the lens.
Combining a silicone hydrogel lens under an RGP does not appear to affect hypoxia. Investigators at The OSU College of Optometry polarographically measured corneal oxygen uptake rates in 10 eyes wearing various combinations of three lenses: an RGP made from Fluoroperm 151, an RGP made from Fluoroperm 30 and a silicone hydrogel made from’ balafilcon A! Researchers found that the addition of silicone hydrogel did not significantly increase corneal hypoxia with RGPs. The study also found that blinking reduced hypoxia in eyes wearing the Fluoroperm 30 and the soft lens, but not in eyes wearing the Fluoroperm 151 and soft lens-probably due to lid-lens interaction differences.
The Rebirth of Ortho-k
Reverse geometry contact lenses appear to be well tolerated and safe for children. Researchers at the The OSU College of Optometry and the New England College of Optometry in Boston recently completed the pilot study of the Children’s Overnight Orthokeratology Investigation (COOKI). This is the first study to document the safety and efficacy of reverse geometry contact lenses for temporary myopia reduction in children.’ Children between eight and 11 years old were fitted with Paragon CRT lenses and examined in the morning, and at least six hours later, at one day, at one and two weeks, and at one, three and six months. Prior to being fitted, average visual acuity was 20/96. After six months, uncorrected visual acuity was 20/28 in the afternoon and improved by an average of 1.OOD six hours after lens removal. No adverse events were reported, leading researchers to conclude that overnight corneal reshaping is a safe and effective means of temporary reduction of myopia for children. (For more on CRT and orthokeratology studies, see Page 24).
You may not be able to predict the chances of a successful orthokeratology treatment based on an individual’s level of corneal eccentricity. Doctors involved in the multicenter Lenses and Overnight Orthokeratology (LOOK) study tested this theory on 39 right eyes and 38 left eyes, some successfully treated by ortho-k, some unsuccessfully treated! Subjects underwent examinations by corneal topography, LogMAR VA, refraction and slit lamp examination. Linear regression analysis found that there was no significant relationship between baseline eccentricity and the amount of refractive change produced by the ortho-k treatment.
Extended Wear
Several studies focused on contact lens-related dry eye and associated risk factors, as well as reasons for discontinuing lens wear. Oxygen deprivation of the ocular surface during lens wear disturbs normal corneal metabolism, which is thought to alter nerve function and result in diminished sensation. A group in Sydney, Australia, conducted a study of 27 long-term extended wearers of low Dk/t soft lenses to determine whether increasing oxygen transmissibility or cessation of lens wear would lead to a change in corneal or conjunctival sensitivity.’ Participants were asked to cease lens wear one week prior to being refitted with a high Dk/t silicone hydrogel lens. Measurements were then taken after one week of no lens wear and at one, three and six months of high Dk/t lens wear. A linear decrease in corneal sensitivity was evident in this group over the time of the study. The study concludes that factors other than oxygen availability alone are involved in determining the sensitivity of the ocular surface and that no effect was found on the conjunctival sensitivity at any point in time.
Another study aimed to determine the average length of discontinuation of lens wear due to adverse reactions. Researchers conducted a retrospective case review of 282 patients wearing bilateral silicone hydrogel lenses on a 30day extended wear schedule.” They evaluated the subjects at one day, one week, one- and three-month intervals. If patients presented with any adverse reactions, lens wear was suspended until the condition resolved. Most adverse reactions were self-limiting, with lens wear resuming an average of 15 days after corneal inflammation and five days after mechanical complications. Denser infiltrates and deeper staining were associated with longer periods of discontinuation.
A group at CIBA Vision compared two separate clinical trials, one in which 658 subjects wore continuous wear lotrafilcon A lenses for 30 days at a time, and one in which 305 subjects wore extended wear lotrafilcon A lenses for six days at a time.” Subjects wore the lenses for one year and were examined seven times. Researchers defined endpoint inflammatory infiltrative events as corneal infiltrates of greater than grade 3, or infiltrates of any grade with overlying fluorescein staining. Incidence of infiltrative events ranged from 3.4 percent to 5 percent for both modalities, with no significant difference between the two. In other published trials studying daily wear lenses, infiltrative events were less frequent, the study concluded.
Acuity Equals Comfort
The quality of the refraction you give your contact lens patients may also affect the patient’s comfort level. Researchers at the University of New South Wales in Sydney, Australia, evaluated 21 contact lens wearers who were subjected to varying levels of discomfort in one eye while wearing each of three contact lens types: soft hydrogel, silicone elastomer, and rigid gas permeable.” At each discomfort level, investigators imposed three different visual conditions: full refractive correction, full correction with an additional +4.OOD blur, or total occlusion of sight. Subjects rated their discomfort on a scale of 1 to 100. Results showed patients perceived more comfort when their vision was occluded entirely than when it was blurred slightly. Comfort levels were highest with fully corrected soft hydrogel lenses, and lowest with blurred RGPs.
Rare Disease Better Understood
A new study has shed some light on contact lens-associated limbal stem cell deficiency (LSCD), a rare and potentially blinding disease that some argue is underdiagnosed. Investigators at the University of Southern California in Los Angeles found and evaluated six patients with contact lens related LSCD. ” One patient wore hard lenses and six wore soft lenses. Their mean age was 32, and average length of wear was 15 years. All claimed good lens cleaning and replacement protocol. Corneal sensation and tear production were significantly reduced as compared ‘to healthy eyes. Researchers advised that the disease is often overlooked but should be suspected in patients with a combination of chronic keratitis, neovascularization and conjunctivalization, and the conditions only improve slowly-if at all-after lens wear ceases.
References
1. Mathers WD, Dolney A. Cornea Department, Casey Eye Institute, OHSU, Portland, OR. Long term changes in lacrimal gland gene expression following corneal trauma. Abstract 2524.
2. Shine WE, Aronowicz J, Oral D, et al. Ophthalmology Department, UT Southwestern Medical Center, Dallas, TX. Characterization of KCS in patients with chronic blepharitis. Abstract 4767.
3. Tomlinson A, TK Beattie, Seal DV. Attachment of Acanthamoeba to Focus Night & Day (lotrafilcon A) silicone hydrogel contact lenses. Abstract 3687.
4. Parmar ON, Pullum K, Buckley R, Collin R. Moorfields Eye Hospital, London. Rigid gas-permeable scleral contact lenses in eyelid malposition with ocular surface disease. Abstract 3285.
5. Suzaki A, Kuroda T, Ninomiya S, et al. Visual Science, Osaka University Graduate School of Medicine, Suita, Japan. Higherorder wavefront aberrations induced by bifocal rigid gas-permeable contact lens. Abstract 3697.
6. Florkey LN, Fink BA, Mitchell GL, Hill RM. Ohio State University College of Optometry, Columbus, OH. Hypoxic responses to RGP + silicone-hydrogel (SH) combination contact lens systems. Abstract 3674.
7. Walline JJ, Rah MJ, Jones LA. Children’s Overnight Orthokeratology Investigation (COOKI) Pilot Study. Abstract 3288. 8. Jackson JIM, Rah MJ, Jones LA, et al. Baseline corneal eccentricity as a predictor for refractive error change in overnight orthokeratology: results from the LOOK study. Abstract 3289.
9. Golebiowski B, Papas EB, Stapleton F. CRC for Eye Research and Technology, Sydney UNSW, Australia. Ocular surface sensitivity following discontinuation of low Dk extended contact lens wear and refitting with high Dk extended wear. Abstract 3705.
10. Edwards K, Naduvilath T, Tahhan N, et al. Duration of discontinuation from silicone hydrogel extended wear due to adverse responses. Abstract 3706.
11. McKenney CD, McNally J, Chalmers R. Ciba Vision Corp., Duluth, GA. The influence of patient factors and wearing schedule on the rate of corneal inflammatory events among wearers of lotrafilcon A lenses. Abstract 3717.
12. Papas EB, Chan E, Sarian L, Tan J. Does the quality of vision affect the perception of ocular discomfort? Abstract 3694.
13. Jacobson EK, Affeldt JC, Agarwar MR. Contact lens related limbal stem cell deficiency. Abstract 1405.
Contributor: Joseph Shovlin