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International Newsletter and Forum on Rigid Gas Permeable Contact Lenses, Corneal Shape, Health and Vision |
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Family Based Practice - Most Suited for Myopia Control?
 Measuring refractive error at 6 years of age may be the best way to predict which children will go on to become myopes, write McGuigan and Hillen in the Ophthalmologist. This statement is primarily based on a study by Zadnik et al published in JAMA Ophthalmology that looked at 'prediction of juvenile-onset of myopia.' The (full access, after registration) article in Ophthalmology also provides a list of risk factors for myopia development (from the CLEERE study). Charles McMonnies in Clinical & Experimental Optometry provides a review article on myopia that also discusses risk factors useful in clinical practice such as (but not limited to): pre-school refraction being emmetropic or myopic, esophoria at near, age of onset of myopia below 9 years of age, low levels of time spent outdoors, reading closer than Harmon distance, at least one myopic parent, myopic siblings, parental tertiary occupation and prone sleeping habits. The author concludes by stating that family-based practice appears to be ideally suited for risk estimation and the clinical application of intervention to control myopia. |
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Optimal Time For (R)GP Fluorescein Evaluation
 The ophthalmic research group at the Life and Health Sciences department of Aston University, Birmingham (UK) examined the optimum time at which fluorescein patterns of (R)GPs should be evaluated. Aligned, 0.2mm steep and 0.2mm flat (R)GPs were fitted to 17 patients. Fluorescein was applied to their upper temporal bulbar conjunctiva with a moistened fluorescein strip, and digital slit lamp images at 10× magnification of the fluorescein pattern viewed with blue light through a yellow filter were captured every 15s. Fluorescein intensity in central, mid peripheral and edge regions of the superior, inferior, temporal and nasal quadrants of the lens were graded subjectively using a +2 to −2 scale. They observed that the stability of fluorescein intensity can start to decline in as little as 45s post-fluorescein instillation; however, the diagnostic pattern of alignment, steep or flat fit is seen in each meridian by subjective observation from about 30s to 3min, indicating that this is the most appropriate time window to evaluate (R)GP lenses in clinical practice. |
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'Scleral Lenses - Where to Start?'
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The Significance of Diagnosis & Age
The purpose of this prospective study was to compare the ease of adoption of a scleral lens device by patients in different age and diagnosis groups. Patients were categorized by age as younger than 60 or 60 years and older and by diagnosis as corneal irregularity or ocular surface disease. There was no significant difference in the number of devices and visits needed between the two age groups or between the corneal irregularity and the ocular surface disease groups. Patients in all groups achieved full-time wear in less than 2 weeks. Average wear time per week did not differ significantly between age or diagnosis groups. Similarly, the time needed for daily insertion and removal during the fitting period, as well as patients' subjective rating of the ease of device insertion and removal, did not differ between age or diagnosis categories. The length of the fitting process was significantly longer in the ocular surface disease group; however, factors not related to ease of adoption of the scleral device may be responsible for this difference.
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Detection, Hydrops & IOP
Screening for keratoconus suspects among candidates for refractive surgery
is the topic of a review paper by McMonnies in Clinical & Experimental Optometry. Screening success may be improved by considering ethnicity; family history of keratoconus; a history of atopy or ocular allergies, in particular; and a history of significant exposure to corneal trauma associated with: abnormal rubbing habits; vocational, leisure or geographically increased exposure to ultraviolet radiation; contact lens wear; or a history of significant exposure to activities that elevate intraocular pressure. These factors may prove useful in estimating the risk of post-surgical ectasia.
In another review paper, in Eye & Contact Lens, McMonnies looks at the mechanisms for acute corneal hydrops and perforation. Acute corneal hydrops and perforation in corneal thinning diseases are the consequences of exposure to distending intraocular pressure (IOP) forces that are in excess of corneal resistance to them, McMonnies writes. Apart from thinning, resistance to these forces may be reduced by disease-related tissue changes, such as corneal scarring - which could lower resistance to IOP. Eye rubbing trauma has sometimes been found to be associated with acute corneal hydrops and with perforation as well. If acute corneal hydrops or perforation occur, faster resolution of edema and wound healing may depend on reducing potentially exacerbating exposures to mechanisms for IOP elevation, McMonnies states.
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Wavefront-guided Optics in Sclerals
A 29-year-old gentleman was referred to our clinic by a local LASIK surgeon who declined to perform LASIK on him because of irregular corneal topographies. Our examination revealed an obvious case of moderate keratoconus in the right eye and mild keratoconus in the left. His unaided visual acuities were 20/60 in the right eye and 20/30 in the left. With 4.5D of astigmatism in the right eye and 2.0D in the left, he was correctable to 20/30 in the right eye and 20/20 in the left with spectacles. Standard scleral lenses with sphero-cylindrical optics to correct the lower-order aberrations resulted in only 20/30 acuity in the right eye. A specially designed LASERFIT lens with wavefront-guided optics improved the quality of vision in his worse right eye to 20/15, while the left eye could identify 20/10 letters. This novel technique and manufacturing process with wavefront-guided optics can result in an additional reduction of the higher-order aberrations in the range of 30%-70% and to improvements in visual acuity of one or more lines over conventional sphero-cylindrical optics. See the full report via the link below.
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Upcoming Events
- ISCLS, Aug 29-Sept 3, St. Gallen (CH)
- Myopie Kongress, 12-13 Sept, Cologne (DE)
- AAO, 7-10 Oct, New Orleans (US)
- ECLSO, 16-17 Oct, Izmir (TU)
- CLMA, 28-31 Oct, Miami (US)
- Cornea CL & Cont Vision Care Symposium, 5-6 Dec, 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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