Normal eyes and eyes with either contact lens warpage or keratoconus were scanned by a Fourier-domain optical coherence tomography (OCT) system. Maps of epithelial thickness and anterior surface mean curvature were generated and converted to deviation maps by subtracting the average maps from a healthy population. The average Epithelial Modulation Index (EMI) value for normal eyes was -0.6±1.0 µm/m. Eyes with keratoconus were characterized by coincident high anterior surface mean curvature and low epithelial thickness, resulting in a high EMI index (manifest keratoconus 103.0±82.9µm/m, subclinical keratoconus 37.0±23.0µm/m and forme fruste keratoconus 7.3±13.2µm/m). The EMI index was closer to normal for eyes with warpage (-1.9±4.0µm/m). The classification accuracy of the index was 100±0% for normal eyes and 99.0±2.0% for eyes with warpage, while it was was 100±0%, 100±0% and 53.1±1.5% for the manifest, subclinical, and forme fruste keratoconus groups, respectively. In conclusion, the investigators believe that OCT and this index are useful in distinguishing eyes with keratoconus from those with contact lens-related corneal warpage. Image: Gustav Poltner

Researchers from Japan measured higher-order aberrations (HOAs) in clinical and subclinical keratoconus (KC). The study included 33, 36, and 26 patients with clinical, topographic (no clinical signs), and pre-topographic (normal topography and no clinical signs) KC and 30 controls without KC. Control eyes and eyes with pre-topographic KC had significantly lower ocular or corneal total HOAs and Zernike vector terms than those with clinical KC and topographic KC, except for ocular tetrafoil between topographic KC and pre-topographic KC and spherical aberration among all groups. The found difference in corneal total HOAs and corneal coma in this study, could serve as a potential tool to discriminate pre-topographic KC from normal control eyes.

One of those questions that remained unanswered for a long time was: What are the inflammatory consequences of wearing scleral lenses? Maria Walker and co-workers shed some important light on this in this review article. Scleral lenses can affect a range of anterior segment structures including the eyelids and also the tear film. The eyelids, consisting of the outer skin layer, the middle tarsal plate and the posterior palpebral conjunctiva, provide physical protection and house the meibomian glands and cilia, which have important and unique functions. Tears consist of a mix of aqueous, mucus and lipidomic components that serve vital functions of lubricity, protection and nourishment to the ocular surface. Both the eyelids and the tear film interact directly with scleral lenses on the eye and can affect but also be impacted by scleral lens wear. This paper provides a review of the anatomy and physiology of the eyelids and tear film, discusses the effects and impacts of the scleral lenses on these structures and identifies areas that require further research.

In some earlier work, Walker et al in Contact Lens & Anterior Eye measured inflammatory mediators in the scleral lens fluid reservoir (FR) in healthy eyes and compared that to basal tear samples. Fifteen normal, habitual soft contact lens wearers were fitted with 14.8mm or 15.4mm scleral lenses, and basal ocular surface tears and FR samples were collected. Levels of interleukin (IL) -4 and -8, matrix metalloproteinase (MMP)-7, -9 and -10 and tissue inhibitor of MMPs (TIMPs) 1-4 were collected. The MMP-9 and MMP-10 values were greater in the FR than in the basal ocular surface tears. After 8h of scleral lens (SL) wear, the median concentration of MMP-9 in the FR and basal tears were 62.7ng/ML and 15.2ng/mL, respectively. Likewise, MMP-10 was significantly greater in the FR compared to in basal tears after 8 hours (25.8ng/mL vs 2.8ng/mL) and after 4 days (2.1ng/mL vs 17.2ng/mL). IL-4 and IL-8 levels were greater in the FR but not significantly. MMP-7 was not affected by scleral lens wear after 8 hours or 4 days. Visual acuity, corneal staining and conjunctival staining did not change; comfort was reduced in SL wear compared to soft contact lens wear. In conclusion: some inflammatory mediators in the scleral lens fluid reservoir were elevated after several hours of SL wear, suggesting potential clinical implications of scleral lens wear that deserve further investigation.