Proefessor Pat Caroline's session on orthoK at the BCLA
A special session chaired by Professor Pat Caroline (Pacific University) (pictured) focused on orthokeratology, an area of growing interest in the UK if the large number of delegates attending is an indicator. The session brought delegates up to date with some of the latest techniques and data on the long-term safety of the modality.
Professor Caroline opened the session with an overview of where the science is today. Contact lens corneal reshaping had been shown to be a safe and effective technique for patients with moderate degrees of myopia. In this situation, the central corneal epithelium was thinned and the mid-periphery thickened by the technique. More recently, lens designs to correct hyperopes had proved successful. Here the thickness profiles were reversed, with the central area thickened and mid-peripheral thinning. This might have an application in the correction of early presbyopia using a monovision approach.
Helen Swarbrick (University of New South Wales) was introduced as the 'mother of ortho-k', due to her groundbreaking paper in 1998 investigating the aetiology of the process in daily-wear patients. She reported on a study carried out with co-workers in 2003 that confirmed the same process in overnight wear and observed that there was also some thickening of the mid-peripheral stroma but no central stromal thickness change.
Thinning of the central corneal epithelium caused some concerns about the maintenance of epithelial barrier function, which had been linked to a possible role in infection. Dr Swarbrick also demonstrated that pressure and bending theories were inaccurate. A two-night study had shown that, for lenses of identical design made in low Dk and high Dk Boston materials, there was (unsurprisingly) more oedema with the low Dk lens and a greater degree of flattening and more change in refractive error with the high Dk lens.
Pauline Cho discussed the increasing concern over reports of MK with orthokeratology. These reports lacked detailed information and had recently led to bad press on the safety of ortho-k in Hong Kong. She went on to report on a study to evaluate whether there was a change in normal ocular flora as a result of ortho-k. The conclusion was that there was no change, contaminants being generally of a transient nature. The lens case was most frequently the source of contamination.
Dr Cho reiterated the importance of compliance and, in particular, rubbing, rinsing and disinfecting the case. A majority of patients who reported good compliance had little or no contamination of their lenses and accessories. Warnings about contamination improved compliance in some, but not all, patients.
Concluding the session, Professor Brien Holden proclaimed that freedom from day-wear was the most attractive feature of modern ortho-k. Wearing lenses overnight had great attraction: no dryness, no discomfort, no lenses - and it worked! However, he reported that there had been 46 cases of MK in ortho-k users since 2000 and although the rate of infection was no higher than in other extended wear, it was of concern that 30 per cent of these infections had been Acanthamoeba compared to only 3 per cent in other forms of continuous wear.
Interestingly, clinicians had discovered a small ortho-k effect in silicone hydrogel lens wearers presenting for aftercare inadvertently wearing their lenses inside-out. There were now groups investigating the possibility of producing a soft lens for orthokeratology.
Professor Caroline opened the session with an overview of where the science is today. Contact lens corneal reshaping had been shown to be a safe and effective technique for patients with moderate degrees of myopia. In this situation, the central corneal epithelium was thinned and the mid-periphery thickened by the technique. More recently, lens designs to correct hyperopes had proved successful. Here the thickness profiles were reversed, with the central area thickened and mid-peripheral thinning. This might have an application in the correction of early presbyopia using a monovision approach.
Helen Swarbrick (University of New South Wales) was introduced as the 'mother of ortho-k', due to her groundbreaking paper in 1998 investigating the aetiology of the process in daily-wear patients. She reported on a study carried out with co-workers in 2003 that confirmed the same process in overnight wear and observed that there was also some thickening of the mid-peripheral stroma but no central stromal thickness change.
Thinning of the central corneal epithelium caused some concerns about the maintenance of epithelial barrier function, which had been linked to a possible role in infection. Dr Swarbrick also demonstrated that pressure and bending theories were inaccurate. A two-night study had shown that, for lenses of identical design made in low Dk and high Dk Boston materials, there was (unsurprisingly) more oedema with the low Dk lens and a greater degree of flattening and more change in refractive error with the high Dk lens.Pauline Cho discussed the increasing concern over reports of MK with orthokeratology. These reports lacked detailed information and had recently led to bad press on the safety of ortho-k in Hong Kong. She went on to report on a study to evaluate whether there was a change in normal ocular flora as a result of ortho-k. The conclusion was that there was no change, contaminants being generally of a transient nature. The lens case was most frequently the source of contamination.
Dr Cho reiterated the importance of compliance and, in particular, rubbing, rinsing and disinfecting the case. A majority of patients who reported good compliance had little or no contamination of their lenses and accessories. Warnings about contamination improved compliance in some, but not all, patients.
Concluding the session, Professor Brien Holden proclaimed that freedom from day-wear was the most attractive feature of modern ortho-k. Wearing lenses overnight had great attraction: no dryness, no discomfort, no lenses - and it worked! However, he reported that there had been 46 cases of MK in ortho-k users since 2000 and although the rate of infection was no higher than in other extended wear, it was of concern that 30 per cent of these infections had been Acanthamoeba compared to only 3 per cent in other forms of continuous wear.
Interestingly, clinicians had discovered a small ortho-k effect in silicone hydrogel lens wearers presenting for aftercare inadvertently wearing their lenses inside-out. There were now groups investigating the possibility of producing a soft lens for orthokeratology.