Vertical D: a novel topographic pattern in some keratoconus suspects.
OBJECTIVE
To describe a novel topographic curvature pattern, vertical D, which was present in some keratoconus suspects. This pattern was detected retrospectively in 2 patients who developed post-LASIK ectasia and prospectively in 4 patients who had other corneal abnormalities suggestive of keratoconus.


METHODS
Retrospective interventional case series and prospective cross-sectional study.


METHODS
After vertical D topographic curvature patterns were noted in 2 patients (3 eyes) who developed post-LASIK ectasia, 1168 consecutive potential refractive surgical candidates (2336 eyes) evaluated at a refractive center were screened to detect this vertical D pattern.


METHODS
Placido disc-based curvature topography, ultrasound pachymetry, and elevation-based Scheimpflug topography were performed on these patients.


METHODS
Corneal curvature topographic patterns, central keratometry, inferior-superior and nasal-temporal ratios, skewed radial axis value, Humphrey Atlas PathFinder corneal analysis, corneal thickness, and corneal anterior and posterior elevation.


RESULTS
Four additional patients (7 eyes) with vertical D patterns were found (prevalence, 0.34%). In addition to this vertical D pattern, these patients had central corneal thickness < 500 microm and/or posterior corneal protrusion > 20 microm or positive results on keratoconus detection analyses. The 10 eyes with the vertical D pattern had more horizontal (nasal-temporal ratio) than vertical (inferior-superior ratio) curvature asymmetry: 0.98+/-0.04 diopters versus 0.44+/-0.2 diopters (paired t test, P<0.001).


CONCLUSIONS
We propose that vertical D is a novel corneal curvature pattern reflecting horizontal asymmetry that was present in keratoconus suspect patients even if standard keratoconus analyses' results were negative.
Abad
Juan Carlos
JC
Laser Eye Center of Miami, Miami, Florida, USA. jcabad@gmail.com
Rubinfeld
Roy S
RS
Del Valle
Maria
M
Belin
Michael W
MW
Kurstin
Joseph M
JM
D000328:Adult; D003315:Cornea / Q000473:pathology*; D019781:Corneal Topography; D003430:Cross-Sectional Studies; D004108:Dilatation, Pathologic / Q000209:etiology; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000175:diagnosis*; D020731:Keratomileusis, Laser In Situ; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D011446:Prospective Studies; D012189:Retrospective Studies