Changes in ocular flow induced by hypo- and hypercapnia relate to static visual acuity in humans
Keywords:ventilation, CO2, vision, ocular circulation.
AbstractWe investigated whether the change in ocular blood flow, induced by hypo- and hypercapnia, is related to static visual acuity. Eleven healthy subjects (26±5 years) underwent three treatments. A three-treatment three-period crossover design was used. In the hypocapnia treatment (HYPO), the subjects controlled their minute ventilation (VE) to a target of 25 L/min for 6 min. In the hypercapnia treatment (HYPER), the subjects inspired high-fraction CO2 gas (FICO2 = 4%) for 6 min. In the control treatment (CON), VE was not manipulated. We measured choroidal and retinal blood flow by laser speckle flowmetry as ocular blood flow, and static visual acuity using the Landolt C chart. End-tidal partial pressure of CO2 differed significantly among HYPO, HYPER and CON (21±1, 48±1, and 42±1 mmHg, respectively). Retinal blood flow decreased significantly from the baseline in HYPO (-22±5%), but increased significantly in HYPER (+3±9%) compared to CON. Decimal visual acuity was significantly lower in HYPO than in the CON (0.21±0.1 vs. 0.24±0.1 P<0.05). These results suggest that changes in ocular blood flow induced by changes in arterial CO2 partial pressure influences visual acuity.
An Open Access Publication is one that meets the following two conditions:
1. The author(s) and copyright holder(s) grant(s) to all users a free, irrevocable, worldwide, perpetual right of access to, and a license to copy, use, distribute, transmit and display the work publicly and to make and distribute derivative works, in any digital medium for any responsible purpose, subject to proper attribution of authorship, as well as the right to make small numbers of printed copies for their personal use.
2. A complete version of the work and all supplemental materials, including a copy of the permission as stated above, in a suitable standard electronic format is deposited immediately upon initial publication in at least one online repository that is supported by an academic institution, scholarly society, government agency, or other well-established organization that seeks to enable open access, unrestricted distribution, interoperability, and long-term archiving.
Authors who publish with this journal agree to the following terms: 1. Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal. 2. Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal. 3. Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work.