Evaluation of Microcirculation at the Optic Nerve Head in Eyes With Keratoconus

Purpose: To evaluate microcirculation at the optic nerve head (ONH) in eyes with keratoconus. Methods: Laser speckle flowgraphy (LSFG) was performed in patients with keratoconus at the International University of Health and Welfare Narita Hospital. Age- and sex-matched control and high myopia groups were selected from screening participants at the Tokyo Kamata Medical Center. LSFG parameters assessed at the ONH included the mean blur rate (MBR) of vascular area (MV), tissue area (MT), and area ratio of bloodstream (ARBS). Values were compared among the three groups, and MV and MT were also analyzed by quadrants. Results: Thirty-one keratoconus eyes, 31 control eyes, and 26 high myopia eyes were analyzed. For overall ONH, MV was lower in keratoconus than in controls (P = 0.040), and MT was lower than in controls and high myopia (both P = 0.014). In quadrant analysis, MV was lower in the superior quadrant than in controls (P = 0.008). MT was lower in the temporal quadrant than in controls (P = 0.022) and high myopia (P < 0.001), and in the nasal quadrant than in controls (P < 0.001) and high myopia (P = 0.031). ARBS was lower in keratoconus than in controls (P = 0.001) and high myopia (P = 0.036). Conclusions: LSFG showed keratoconus eyes had significantly reduced MBR and ARBS at the ONH compared with normal and highly myopic eyes. These findings suggest that keratoconus may involve alterations in ONH circulation, highlighting the need to monitor optic nerve function in clinical practice.