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International Newsletter and Forum on Rigid Gas Permeable Contact Lenses, Corneal Shape, Health and Vision |
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Joined Forces?
 The Rotterdam Erasmus Academic Medical Center in the Netherlands has started prescribing atropine to kids who develop myopia at a young age. Studies at the Rotterdam Institute found a severe impact of high myopia on visual performance: one in three high myopes (6D or more and with an axial length of 26mm) has a risk of severe vision loss during his or her lifetime (a VA of less than 0.3). A study from Sydney, presented at the recent ARVO 2016 meeting in Seattle (US), indicated that the reason for vision loss is not always clear (Jong et al, poster #2470). In a group of high myopes (8.7±2.9D) with no obvious retinal pathology, a significant percentage of eyes (35%) had mild visual impairment (VA between <1.0 to ≥0.3) while 1.2% had moderate visual impairment (VA between <0.3 to ≥0.1) and 0.3% showed severe visual impairment (VA <0.1). The Rotterdam protocol calls for three types of action for young myopes to prevent them from becoming highly myopic: pharmaceutical, optical and lifestyle interventions. In addition to atropine, and/or as a stand-alone treatment, optical intervention with dual-focus center-distance soft lenses is prescribed. Orthokeratology could serve the same purpose, being very effective. The only limitation in this regard is that for low myopes (under -2D), the added plus power in the periphery would potentially not be high enough to gain enough peripheral plus with standard orthokeratology treatment. The added benefit of combining contact lenses with atropine would be that loss of accommodation with atropine (much less of an issue with 0.01% than with 1%, but still potentially noticeable) could be countered by the contact lenses - while targeting another myopia controlling mechanism at the same time. Also, an optical treatment may fail in some patients, while atropine treatment works - or the reverse. It may be time to join forces?
Eef van der Worp
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Orthokeratology & Myopia Control
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A New Perspective
Pauline Kang and Helen Swarbrick in Optometry & Vision Science published an article shedding some new light on the effectiviness of orthokeratology in myopia control. To compare peripheral refraction along both the horizontal and vertical retinal meridians before and after orthokeratology (OK) lens wear, 19 young adult myopic subjects (mean age 28±7 years) were fitted with OK lenses in both eyes. Central and peripheral refraction and corneal topography measurements were taken before and after 14 nights of OK. In this study, the OK lenses induced significant changes in peripheral refraction along the horizontal and vertical meridians. Further research is needed, but as peripheral myopia was measured at baseline along the vertical meridian, the results of the study suggest that inducing greater degrees of myopic defocus on to the peripheral retina may be required for effective myopia control, more than habitually experienced.
Kang, Swarbrick - Optometry & Vision Science, March 2016
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Treatment Zone Decentration
 Do eyes with higher amounts of corneal toricity give rise to increased amounts of treatment zone decentration in overnight orthokeratology? The magnitude of treatment zone decentration between eyes with minimally toric corneas (≤1.50DC, LoTor group) and eyes with moderately toric corneas (1.50 to 3.50DC, HiTor groups I & II) after a single overnight wear of spherical orthokeratology lenses were compared. The mean magnitude of treatment zone decentration was 0.48±0.20mm in the LoTor group, 1.06±0.57mm in HiTor group I, and 0.95±0.44mm in HiTor group II. Treatment zone decentration in the LoTor group was significantly different from HiTor group I (p<0.001). Treatment zone decentration was not significantly different between HiTor groups I and II. The magnitude of treatment zone decentration was positively correlated with the amount of baseline corneal toricity (LoTor and HiTor group I combined, p=0.048). In conclusion: yes, eyes with higher amounts of corneal toricity do seem to give rise to increased amounts of treatment zone decentration in overnight orthokeratology.
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Managing the Cone

Mandathara et al from Sydney (AU) looked at the past 20 years of contemporary management modalities for keratoconus (KC). A systematic review of the literature on KC management options for the last 20 years was performed and revealed various flavors of options. A total of 1,147 articles were retrieved; of those, 241 satisfied the inclusion criteria, and 41.1% of them were prospective case series. The higher level of evidence studies (randomized controlled trials or RCTs) were limited to only one intervention: that is, corneal collagen cross-linking (CXL). However, the quality of most RCTs was limited because of performance and detection bias. Contact lenses remain the mainstream of KC management and were associated with reversible and non-sight-threatening complications. Surgical options such as intracorneal segment implantation and phakic intraocular lenses are considered in the visual rehabilitation of contact lens intolerants, and CXL is the only available option to stop or delay the disease progression. Generally, these surgical procedures are associated with transient inflammatory events and permanent sequelae, the paper states.
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First Settlers
Scleral lens fitting is still somewhat in its infancy, or its first settlers' stage. But this study by Esen and Toker sheds some new light on scleral lens settling. Eleven patients (22 eyes) with keratoconus were fitted with mini-scleral lenses with increasingly greater sagittal depths to achieve 3 levels of initial apical clearance: 100 to 200μm (low), 200 to 300μm (medium), and greater than 300 μm (high). Mean settling of the lenses was 26.8±18.8μm (42.7%) at 1 hr, 39.5±26.5μm (62.9%) at 2 hrs, 50.7±31.6μm (80.8%) at 4 hrs, 57.4±34.6μm (91.4%) at 6 hrs, and 62.8±38.4μm (100%) at 8 hrs. The settling rate was significantly lower in the low-apical-clearance group (p=0.01). The smaller-diameter lenses settled more (p=0.03). There was a slight statistically significant increase of 1.3% in central corneal thickness measured with OCT (p=0.03). Central corneal thickness measured with Pentacam at three locations increased slightly (p=0.001). Settling showed significant intrasubject and intersubject variations. In conclusion: the average amount of settling was 62.8μm after 8 hrs, 80% of which occurred during the first 4 hrs. Slight corneal swelling (1.3%) occurred after 8 hrs of wear.
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Anterior Scleral and Conjunctival Thickness
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Diurnal Variation
Relevant to the latter item in terms of scleral lens sinking, or settling, may be the variation in anterior scleral and conjunctival thickness during the day. Read et al from Brisbane (AU) examined 19 healthy young adults (mean age 22±2 years) and measured anterior scleral and conjunctival thickness using anterior segment optical coherence tomography (AS-OCT) at seven measurement sessions over a 24-h period. The thickness of the temporal anterior sclera and conjunctiva were determined at six locations (each separated by 0.5mm) at varying distances from the scleral spur for each subject at each measurement session. They found that both the anterior sclera and conjunctiva undergo significant diurnal variations in thickness over the 24-h period (both p<0.01). The sclera and conjunctiva exhibited a similar pattern of diurnal change, with a small-magnitude thinning observed close to midday, and a larger-magnitude thickening observed in the early morning immediately after waking. The amplitude of diurnal thickness change was larger in the conjunctiva (mean amplitude 69±29μm) compared to the sclera (21±8μm). The conjunctiva exhibited its smallest magnitude of change at the scleral spur location (mean amplitude 56±17μm), whereas the sclera exhibited its largest magnitude of change at this location (52±21μm).
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Have a Safe Landing

Designing a lens with toric peripheries not only improves scleral landing zone alignment, but it also has been shown to improve comfort and increase wearing time. It also may help to reduce excessive tear exchange and, as a result, may help reduce the inflow of tear reservoir debris. Some manufacturers now offer diagnostic lenses with toric peripheries. It may seem overwhelming, but fitting a back toric scleral lens design is actually less complex than it initially appears. It is like fitting an individual scleral lens in different meridians, and then combining that information into one lens. When evaluating the landing zone, it is important to view every quadrant of the periphery in primary gaze. Next, evaluate the lens with the patient viewing in peripheral gaze in each of the four quadrants. In peripheral gaze, scleral landing zones are exaggerated. When compression and/or impingement are observed in peripheral gaze, re-evaluate carefully in primary gaze. If it subsides in primary gaze, only minor modifications to loosen the fit are useful.
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Upcoming Events
- International Congress of Scleral Contacts, July 29, Miami (US)
- ECLSO, 30 Sept-1 Oct, Paris (FR)
- European Ophthalmology Conference, Sept 21-23, Amsterdam (NL)
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- AAO, Nov 9-12, Anaheim (US)
- Specialty Lens Day - Optometric Management, Dec 1-4, Orlando (US)
- Cornea & CL Symposium, Dec 3-4, University of Houston, Houston (US)
- Forum for Scleral Lens Research, Dec 5, TERTC/UHCO, Houston (US)
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I-site is an educational newsletter that is distributed on a monthly basis and provides an update on rigid gas permeable related topics (scientific research, case reports and other publications worldwide). I-site is objective and non-political. Its editor Eef van der Worp, optometrist, PhD, FAAO, FBCLA, FIACLE, FSLS is a lecturer for a variety of industry partners, but is not related to any specific company. Please contact us at: i-site@netherlens.com.
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