Researchers Decry a “Lack of Unified Criteria” When Defining Keratoconus Progression

Keratoconus progression has been defined in many ways in previous literature, with the majority of studies finding maximum keratometry as the most useful criterion when analyzing the development of this disorder. Photo: Clark Chang, OD, MS, and Tracy Swartz, OD. Click image to enlarge. Keratoconus can advance to severe and debilitating levels over time if not managed or treated properly using lenses or corneal collagen crosslinking (CXL). Investigations of the nuances of this condition have observed patient data in different ways and suggested different methods for creating baselines to use in ongoing monitoring. However, a recent literature review argues that a more accurate representation of how to monitor this corneal disorder needs to be established to improve consistency.Recently, researchers from Peru conducted a systematic review of keratoconus studies to determine which testing methods are most effective in defining progression. Using the keywords “progressive keratoconus” or “keratoconus progression,” they collected a total of 221 articles from multiple databases. Studies were reviewed if the inclusion criteria included keratoconus patients without prior history of surgery and the sample size exceeded 10 eyes. Additionally, duplicated studies, literature reviews, case reports and editorial commentaries were excluded from this review.After analyzing the literature, the researchers discovered over 30 different criteria have variously been used to define progressive keratoconus, and over 52 cutoff points were established to further elaborate upon progression. Three parameters were examined more frequently than others: anterior curvature (86.8% of 221 studies), pachymetry (37.6%) and refraction (32.1%). Under the parameter anterior curvature, maximum keratometry (Kmax) was the most widely used criterion (85.5%). Not only was this a frequently used anterior curvature criterion, but it was used more than all others. A change in refractive astigmatism was the second most used criterion (23.1%). For advice on keratoconus diagnosis, see this recent feature. “Despite Kmax’s shortcomings, this measure is practical and universally used,” said the authors in their article. “Some of the possible reasons why single-point Kmax and one measurement instead of multiple measurements are still being used could be related to the lack of enough literature to confirm the proposed alternatives across platforms, the lack of commercially available tested tools, whether zonal Kmax or epithelial profile, for example, other reasons may include the fact that it is the variable used in most prospective randomized trials and subsequently adopted by many insurance companies, and is the most significant change after CXL.”Other data points suggested how studies favor certain parameters over others. For instance, only 8.1% of studies used a method of measuring posterior curvature as criteria to define keratoconus progression, and no study examined data on corneal aberrations of the corneal epithelium. However, the researchers noted that Scheimpflug imaging and AS-OCT data were used to assess progression in some studies, suggesting that these studies had the technological capabilities to observe other corneal abnormalities.Moving forward, future research should attempt to define keratoconus progression with a more unified approach. As this study suggested, Kmax measurements are highly dependable for research purposes, followed by changes in refractive astigmatism and pachymetry measurements, and conducting full investigations of the cornea using all technology available may provide a more robust definition of progression.Click here for the journal source. Henriquez MA, Larco C, Izquierdo L. Definition of progressive keratoconus: A systematic review. Cornea 2025; 44:11:1341-1351. This article was developed by the editorial staff in conjunction with experts in the field. In the process, AI may have been among the editorial tools used to meet the goals of human editors, who approved all content.