Quantified Histopathology of the Keratoconic Cornea

Abstract

Purpose The present study systematically investigated and quantified histopathological changes in a series of keratoconic (Kc) corneas utilizing a physiologically formulated fixative to not further distort the already distorted diseased corneas. Methods Twelve surgically removed Kc corneal buttons were immediately preserved and processed for light and transmission electron microscopy using an established corneal protocol. Measurements were taken from the central cone and peripheral regions of the host button. The sample size examined ranged in length from 390–2608um centrally and 439–2242um peripherally. Results The average corneal thickness was 437um centrally and 559um peripherally. Epithelial thickness varied centrally from 14–92um and peripherally from 30–91um. A marked thickening of the epithelial basement membrane was noted in 58% of corneas. Centrally, anterior limiting lamina (ALL) was thinned or lost over 60% of the area examined, while peripheral cornea was also affected, but to a lesser extent. Histopathologically, posterior cornea remained undisturbed by the disease. Anteriorly in the stroma, an increased number of cells and tissue debris were encountered and some of these cells were clearly not keratocytes. Conclusions It is concluded that Kc pathology, at least initially, has a distinct anterior focus involving the epithelium, ALL and anterior stroma. The epithelium had lost its cellular uniformity and was compromised by the loss or damage to the ALL. The activity of the hitherto unreported recruited stromal cells may be to break down and remove ALL and anterior stromal lamellae leading to the overall thinning that accompanies this disease.

Recurrence or Re-emergence of Keratoconus – What is the Evidence Telling Us? Literature Review and Two Case Reports

“…31,32 Compared to an age-matched control group, the keratoconic cornea was shown to be thinner across the full width of the cornea, but the difference between normal and keratoconic corneas became smaller toward the limbus. 32 Histopathology demonstrated that the pathological changes seen peripheral to the Fleischer's ring were the same as those observed centrally in the cone, but, again, to a lesser degree.…”

Evaluation of the anterior chamber angle in keratoconus and normal subjects

“…The present data used the same way of grading the degree of KC as Emre and coworkers [16] (i.e., k-values), however, the larger number of KC eyes included by Emre et al may also explain the narrower anterior chamber angle in severe cases of KC found in their study as compared to the present data. It was recently demonstrated that the peripheral cornea was affected by this disease [11,12]. However, both these studies found the peripheral cornea was affected to a lesser degree than the tissue within the Fleischer ring; presumably these peripheral changes were not sufficient to alter the geometry of the angle.…”

“…With KC patients angle estimates using the traditional von Herick's technique may not provide accurate assessment and gonioscopy may provoke undesired corneal trauma and discomfort. The latter is especially the case with the KC diseased corneal structure where the epithelial adhesion apparatus is greatly affected [11]. An evaluation of the anterior chamber angle in KC subjects is most frequently screened during biomicroscopy using van Herick's technique.…”

“…Recently it was established in vivo and histopathologically that the cornea peripheral to Fleischer ring is also affected by KC [11,12]. This research has, as a consequence, suggested that KC is a pancorneal pathology and not a disease restricted to the region of the cone itself.…”

Keratoconus und dessen Behandlung mit Hornhautvernetzung und Kontaktlinsen: ein Überblick

“…Es besteht ein Verlust von stromalen Kollagen-Lamellen und eine gestörte Ausrichtung der Kollagenfibrillen. Verminderte Keratozytendichte zeigt sich insbesondere im zentralen vorderen Stroma [50]. [35,36].…”