Where to start? From many meetings I come back 'revived' and full of new ideas. This was certainly the case for this year's American Academy of Optometry (AAO) (with a record number of 5,647 registrants). Let me just pick one topic: higher order aberrations (HOAs) in keratoconus & scleral lenses. Granted, this is actually two topics: but in my defense, highly related. First was a poster by Sepideh Khaef et al on ocular aberrations in keratoconus suspects and in normal subjects. They found that corneal topography (the I-S value) is actually the most informative for early diagnosis of keratoconus. Aberrometry may be useful for advanced or intermediate keratoconus and for follow-up, but in this study aberrometry was less informative compared to topographical data in early stages. Then there was a free paper by Lynette Johns et al on optics in scleral lenses. Spherical optics in prostetic devices correct irregular astigmatism in corneal ectasia; however they correct only (part of) the anterior corneal surface aberrations: the residual HOA remain. Optimizing the optical quality of the front surface, by aspheric surfaces for instance, can improve visual function. Another paper from the Boston Foundation for Sight and the University of Rochester by Geunyoung Yoon et al, presented by Ramkumar Sabesan at the meeting, demonstrated that customized wavefront-guided scleral lens fitting improved visual performance in keratoconic patients. The optical improvements were better, though, than the subjective improvements, and the authors suggested that neural adaptation could play a role. This proves that while all of this is very promising, there is still a long way to go and a lot to learn. We will keep you posted.  

Eye & Contact Lens September 2011

Greg DeNaeyer

A prospective cross-sectional study of 116 keratoconic patients by Rui Hua Wei et al in Singapore looked at the correction method used for their condition. Overall, 67 percent of the study patients used contact lenses, 94 percent of whom were fitted with (R)GP lenses. Proprietary keratoconus designs were used in 75 percent of keratoconus and in 30 percent of keratoconus suspect eyes and were therefore the main mode of treatment for the majority of patients who had not undergone surgery. So contact lenses were the main mode of treatment for the majority of the patients who had not undergone surgery. Interestingly, this is similar to data from other tertiary eye care centers in India (65 percent) and in the United States (75 percent), but lower than the 90 and 97 percent values reported in the United Kingdom, the article reports. Multiple factors contribute to these varying data. The investigators imply that the severity of the disease being managed can be a factor, but also the cost and availability of the lenses may contribute (see link below for full access paper).

Eye & Contact Lens September 2011

Corneal dystrophies represent a dynamic field. With the revolution in molecular genetics, our understanding of corneal dystrophies has changed in the last 15 years as disorders have been mapped and the genes responsible have been identified. This is the introduction to a book on the topic by Lisch and Seits (Karger 2011). The first challenge in this field is the word 'corneal dystrophy' itself - as 'genetic corneal disease' may in fact be a more appropriate term. But the 2005 international committee for classification of corneal dystrophies (IC3D) decided to still adhere to the term, which was first used by Fuchs 100 year ago when he first described the famous condition with his name attached to it as an eponym. The same group of experts also decided on the IC3D classification. In this new classification, all corneal dystrophies have been categorized into four groups. The level to which the gene involved in the condition has been respectively mapped and/or identified is the crucial denominator for this categorization. The book covers this classification in detail, but also has some clinical features such as the chapter on 'The Clinical Landmarks of Corneal Dystrophies,' which lists the conditions involved based on their appearance (e.g. cyst-like opacities, line-like opacities, fleck-like opacities, etc.). It also looks at the histological landmarks in corneal dystrophy and the genetics of corneal dystrophies. It is therefore not a classical clinical textbook on dystrophies, but a great addition for anyone who wants to understand corneal dystrophies. Or should we say genetic corneal disease?

Corneal Dystrophies - Lisch & Seitz 2011