Clinical/Topographic Correlations

J. Bradley Randleman, MD; Marcony R. Santhiago, MD, PhD; and William J. Dupps, MD, PhD

Beyond corneal ectatic disorders and findings before and after corneal refractive surgery, there are clinical entities that present with unique, clinically relevant findings where advanced corneal imaging may be of benefit in their evaluation, diagnosis, and management. The following represents a non-exhaustive collection of these conditions: dry eye, corneal scarring following infectious keratitis, epithelial basement membrane dystrophy (EBMD), Salzmann’s nodular degeneration, pterygium, Fuchs’ corneal dystrophy, corneal stromal dystrophies, limbal stem cell deficiency (LSCD), and floppy eyelid syndrome.

SECTION 1: DRY EYE

Mild dry eye typically causes symptoms without clinical findings, but more severe forms of dry eye manifest as surface irregularity that can be seen with clinical imaging. In some instances, dry eye can masquerade as other conditions on isolated clinical imaging devices, and multiple imaging modalities may be beneficial in making the appropriate diagnosis. Placido imaging is more sensitive to tear film alterations and typically provides a more useful analysis of dry eye–related findings than Scheimpflug imaging.

Case note: Because Scheimpflug imaging interpolates curvature data always, there is never any obvious data drop out centrally in curvature maps. This processing can partially mask significant dry eye or other surface alteration because the irregularly irregular pattern that is readily apparent with Placido imaging is difficult to discern in Scheimpflug imaging.

Case note: Surface irregularity will impact keratometry values at the time of surgery. In this case, the surface irregularity was unfortunately not recognized, resulting in inaccurate IOL calculations. After a treatment regimen to regularize the ocular surface, the curvature pattern appeared significantly more normal. The patient proceeded to IOL exchange.

A 37-year-old patient with high myopic astigmatism complained of progressively worsening acuity in both eyes over the past year. The patient had Placido imaging, was diagnosed with keratoconus, and was referred for evaluation.

Case note: In this case, interpretation of Placido imaging in isolation led to an incorrect diagnosis of keratoconus, when the patient in fact had dry eyes. However, tangential curvature on Placido imaging better highlighted the irregularly irregular nature of the dry eyes, while both dual Scheimpflug/Placido and Scheimpflug imaging to some degree masked this finding. In this case, multiple imaging modalities ruled out an ectatic cornea diagnosis but also facilitated a dry eye diagnosis; no imaging modality in isolation was sufficient to reach an accurate diagnosis.

SECTION 2: CORNEAL SCARRING RESULTING FROM INFECTIOUS KERATITIS

Infectious keratitis leads to corneal scarring, the severity of which depends on the extent and location of the infectious process. Many of these cases result from contact lens wear; thus, most patients who suffer from infectious keratitis require some form of refractive correction for best acuity.

SECTION 3: EPITHELIAL BASEMENT MEMBRANE DYSTROPHY

Also termed anterior basement membrane dystrophy, map-dot dystrophy, and Cogan’s microcystic dystrophy, EBMD is a disease process impacting the epithelial basement membrane, Bowman’s membrane, and, occasionally, the anterior stroma in severe cases presenting with duplicated, irregular basement membrane material becoming sequestered within normal epithelial layers, causing irregular linear deposits within the epithelial layers. These irregularities can give rise to irregular curvature and anterior opacities that reduce acuity if located within or near the visual axis, and recurrent erosion symptoms.