The Father of the Corneal Contact Lens
This year’s I-site newsletter opens with a fantastic article – a must-read, if you ask me, for anyone in the industry – about Kevin Michael Tuohy, who was born on 11 July 1921 in New Jersey (US). The first article ever describing the 'Tuohy lens' – the first corneal lens – was published in 1948. Accordingly, the year 2023 represents the 75th anniversary of its introduction and constitutes a timely opportunity to consider its impact as reported in contemporary publications, writes Richard Pearson in this magnificent review article in Contact Lens & Anterior Eye. Following experiments conducted in 1947, on 28 February 1948 an application for a patent was filed on behalf of Kevin M Tuohy for a plastic contact lens without a scleral zone, and this patent was granted on 6 June 1950. Illustrations in the Tuohy patent application show that it had a bi-curve back surface with a total diameter of 11.5mm. Due to the large size of the back-optic-zone diameter, the back-optic-zone radius was fitted 0.30mm flatter than the flattest corneal meridian. Hence, the resultant power of the liquid lens was –1.50D. Soon after its introduction, the following reports were made about the wearing time of the lens: 10 patients who were unsuccessful with scleral lenses wore Tuohy lenses all their waking hours and had discarded their spectacles. The Tuohy lens provided a much longer wearing time than sealed scleral lenses by eliminating Sattler’s veil (corneal edema) as a result of tear circulation. By late 1947, about 12 people in the US had been fitted with Tuohy lenses, and this number rose to 1300 in 1949 and to 75,000 by 1953. Following the introduction of the Tuohy lens, sales of contact lenses in the US increased dramatically from 50,000 pairs in 1946 to 200,000 pairs in 1949. While there were six major contact lens laboratories in the USA in 1950, by 1966 this number had increased to approximately 300 of various sizes. It was undoubtedly the success of the Tuohy lens that was responsible for this. Tuohy should undoubtedly be remembered as ‘the father of the corneal contact lens.’ Thank you, Richard Pearson, for providing this staggering story.
Front Optical Design Matters
Orthokeratology (ortho-k) is not exacty all that 'crisp' anymore: the first Global Orthokeratology Symposium (predecessor of the current Global Specialty Lens Symposium) took place in 2002, and the original ortho-k lens dates from back in the 1970s. But we are still learning. In the last I-site newsletter, Kate Gifford explored updates and upgrades to current ortho-k lens designs, looking at different (smaller) optical zone sizes to improve myopia management efficacy. This paper (link below) explores that topic more, looking at different front optical designs and at higher-order aberrations (HOA) and visual performance at different pupil diameters. The prospective study included subjects randomized to wear spherical base curve-designed ortho-k (SOK) versus aspheric base curve-designed ortho-k (AOK) lenses. Sixty-five participants completed the study. After 3 months of wear, aspheric ortho-k lenses produced a significantly greater spherical aberration compared to SOK lenses; more significance at lower diopters, without sacrificing subjective visual performance. The amount of spherical aberration can potentially make a difference in myopia progression efficacy.
Scleral Lenses
Prescription Habits
From the renowned SCOPE survey group, a report on prescription habits for the management of corneal irregularity and ocular surface disease among scleral lens practitioners appeared in Eye & Contact Lens, broadening the topic a bit and looking at other management options as well. As the first choice for the management of corneal irregularity, scleral lenses (42%) were most frequently considered by the 778 respondents, followed by rigid corneal lenses (20%). For ocular surface disease, lubricant drops are most frequently used first, followed by meibomian gland expression, topical cyclosporine or lifitegrast, topical steroids, punctal plugs, and scleral lenses, respectively. Lubricant drops were the first therapeutic option considered for ocular surface disease by 63% of participants, and 45% ranked scleral lenses as their sixth, seventh or eighth treatment based on median overall rank. Scleral lenses were identified as the first option for management of corneal irregularity more frequently than corneal lenses were. Sclerals are considered for management of ocular surface disease before surgical intervention but after meibomian gland expression, punctal occlusion, and topical medical therapy are attempted.
Factors Affecting Quality of Life
This study from India tried to identify factors affecting the quality of life (QoL) of adults with keratoconus using a questionnaire. In this cross-sectional study, 574 patients with keratoconus completed the 29-item questionnaire. Participants were categorized into four groups: mild (<48D mean corneal curvature); moderate (48-53D); advanced (54-55D) and severe (>55D). Of the participants, 304 (53%), 160 (28%), 26 (4%) and 84 (15%) belonged to the keratoconus groups 1, 2, 3 and 4, respectively. Statistically significant associations were found between activity limitation score and the following measures: visual acuity (VA) in the better-seeing eye; VA in the worse-seeing eye and ocular aberrations in the worse-seeing eye. Statistically significant associations were also found between symptom score and mean corneal curvature in the better-seeing eye. In regression models, female sex was associated with a 21% worse symptom score compared to males, and working people experienced clinically and statistically significantly greater trouble from symptoms compared to those not working. In conclusion: people with keratoconus have poorer QoL in terms of activity limitations if they have poorer VA and greater wavefront aberrations and in terms of symptoms if they are female and employed.
Regional Demographics & Altitude
The aim of this prospective study was to identify the demographic and clinical variations of keratoconus in Saudi Arabia. Six hundred and forty-eight patients (375 male, 273 female; mean age: 27 years) were conducted at 13 central hospitals in all administrate areas of Saudi Arabia. The geographical distribution rate of keratoconus was highest in the mountainous areas. For dry eye, 21.9% and 44.8% of the patients, respectively, reported frequent or occasional dryness, and 13.4% and 48.9% of the patients, respectively, reported frequent or occasional bouts of eye allergy. Furthermore, 17.9% and 61.9% of the patients, respectively, reported that they constantly or sometimes rubbed their eyes. Marriages were endogamous in 53.5% of the patients, and the family history was positive by 56.8%. There was a history of ocular disease in 27% of the patients, and systemic disease was found in 13%. In conclusion, regional demographic and clinical variations of keratoconus in Saudi Arabia were found, and the findings suggest that the different distribution of keratoconic patients between provinces is attributable to genetic and/or environmental factors. Photo by Fabrizio Conti on Unsplash
New Keratoconus Book
Diagnosis & Management
This crisp new book on keratoconus by Luis Izquierdo and Maria Henriquez from Lima (Peru) and Mark Mannis from the US (all MD) states that over the past several decades, our understanding of this disorder has been clarified with new genetic insights, a better understanding of corneal biology and the physical properties of the cornea, and a much more detailed understanding of corneal optics. The next step is to make that clinical. They gathered authorities from around the world to provide a detailed contemporary assessment of the diagnostic and therapeutic options available. In the part on the biomechanics of keratoconus, it becomes clear that moderate and advanced stages of keratoconus are readily recognized, but the identification of milder or subclinical forms of this disease sometimes remains challenging. The advent of refractive surgery increased the need for the diagnosis and characterization of ectatic corneal diseases. Each chapter highlights key concepts. Chapter 8 (Clinical Course) for instance states that the progression of keratoconus is variable and is linked to environmental factors and eye-rubbing habits as well as to multiple genes - but also that to date, there is no consensus on criteria or cutoff values to define progression in keratoconus. Caution should be taken when assessing progression on a single parameter, as measurement predictability drops with increasing severity. The chapter on ‘non-surgical’ management (glasses and contact lenses), written by Melissa Barnett, Karen Lee and Mark Mannis, is relatively small but contains great tables, such as on soft lens options, and practical tips on scleral lens application & removal techniques. In general, it is a worthy contribution for every practice working with keratoconus patients on a regular basis.
An excellent resource with the latest in the field comes from the National Keratoconus Foundation, which has its own newsletter, a doctor finder and a webinar series. The organization’s mission is to increase awareness of keratoconus and to provide information and resources to those living with the disease.
International Forum for Scleral Lens Research
Meet your colleagues at the 6th annual IFSLR meeting to discuss current and future research on scleral lenses. Join Muriel Schornack, Maria Walker, Jan Bergmanson and Daddi Fadel as they moderate sessions being presented by industry experts such as Karen Carrasquillo, Gloria Chiu, Melanie Frogozo, Jennifer Liao, Amy Nau, Boris Severinsky, Christine Sindt and Stephanie Tran. The IFSLR is dedicated to disseminating research regarding scleral lenses to improve our understanding of these devices and to enhance clinical care. The IFSLR will take place January 18, 2023 - prior the Global Specialty Lens Symposium.
Global Specialty Lens Symposium 2023
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. Disclosure: I-site's editor Eef van der Worp, optometrist PhD FAAO FBCLA FIACLE FSLS, receives educational grants from a number of industry partners but is not related to any specific company.