Short-term effects on ocular variables immediately after hyperbaric oxygen exposures.

PURPOSE: To determine ocular refraction, corneal thickness, corneal radius, corneal power, corneal astigmatism and intraocular pressure in patients before and immediately after repeated hyperbaric oxygen (HBO2) exposures twice a week during six weeks of HBO2 therapy. METHODS: 23 patients received HBO2 therapy at 2.4 ATA for 90 minutes daily in monoplace chambers for six weeks, five days a week. The Topcon TRK-1P instrument was installed next to the hyperbaric chambers to record the ocular measurements. RESULTS: A gross myopic shift developed at -0.95 ± 0.54 D (P ⟨ 0.001) in the right eye and -0.95 ± 0.53 D (P ⟨ 0.001) in the left eye during the six weeks of treatment. Myopic shift reversion, corneal thinning and reduced intraocular pressure appeared as immediate effects after a single HBO2 exposure, but resolved before the patients attended for the next measurement visit. CONCLUSIONS: Ocular variables were influenced by both cumulative and transient short-term effects during the HBO2 therapy. The short-term effects showed that the point of time for performing the ocular measurements after HBO2 exposure might influence the result and must be considered before making relevant comparisons among studies.

Myopic Shift during Hyperbaric Oxygenation Attributed to Lens Index Changes.

PURPOSE: To examine ocular lens parameters and structural changes to elucidate mechanisms underlying the myopic shift and cataract-related changes that occur in some patients during hyperbaric oxygen (HBO) therapy. METHODS: Scheimpflug images (Nidek EAS-1000) of the crystalline lens, measurements of scattered light, objective refraction, keratometry, tonometry, and axial length of the eye were obtained after the first day of HBO therapy and repeated when patients had completed 19 days of the treatment. RESULTS: Significant reduction in mean (± SD) optical density was found in the lens nucleus, -2.8 (± 4.3) units (p = 0.009) and -2.2 (± 4.1) units (p = 0.027) within circular and oval areas, respectively. Significant decrease in mean (± SD) backward scattered light was measured, -0.4 (± 0.8) units (p = 0.022). Mean (± SD) myopic shift was -0.58 (± 0.39) diopters (p < 0.001), whereas cortical optical density, forward scattered light, lenticular parameters, keratometry, tonometry, anterior chamber depth, and axial length of the eye appeared unchanged. CONCLUSIONS: Transient myopic shift reported in patients during HBO therapy is attributed to changes in the refractive index of the lens. No changes in lens curvatures or thickness were found after treatment.

Posterior segment changes of the eye during hyperbaric oxygen therapy.

PURPOSE: To examine central retinal thickness, retinal and vitreo-retinal structures, and ocular blood flow during a standard protocol of hyperbaric oxygen (HBO2) therapy. METHODS: Retinal thickness and color scans of the vitreo-retinal structures were obtained before and after 19 days of HBO2 therapy in 15 patients by optical coherence tomography (OCT). Pulsatile ocular blood flow was measured by ocular blood flow tonometry. Ocular refraction and axial length of the eye were monitored for control. RESULTS: Significant reduction was found in mean retinal thickness, -1.7 ± 1.6 µm (range -3.9 to 1.1 µm) (p < 0.001) in nine subfields within the 6-mm-diameter circle around the central macula. An insignificant decrease in pulsatile ocular blood flow of -19.0 ± 148.8 µl/minute was measured. No morphological changes were seen in retinal and vitreo-retinal structures. A mean myopic shift of -0.62 ± 0.39 D (p < 0.001) developed while axial length of the eye remained unchanged. CONCLUSIONS: A small decrease in central retinal thickness was seen during the study period, but the changes were not correlated to the myopic shift. No significant changes in vitreo-retinal structures or ocular pulsatile blood flow occurred.

Phakic and pseudophakic eyes in patients during hyperbaric oxygen therapy.

PURPOSE: To examine the optical components of phakic and pseudophakic eyes during hyperbaric oxygen (HBO) therapy, and to quantify their relative impact on ocular refractive changes. METHODS: HBO therapy was given to 16 phakic and six pseudophakic patients for 90 min daily at a pressure of 240 kPa, 5 d a week for 20 days. An eye examination was performed on the first day of HBO therapy and repeated when the patients had completed 19 days of the treatment. Refractive error, best-corrected visual acuity, corneal power, radius, thickness and volume, anterior chamber depth, axial length, lens opacity, and intraocular pressure were measured in all patients. Serum glucose, glycosylated hemoglobin, serum electrolytes, and protein were measured in the phakic patients. RESULTS: In the phakic group, a significant myopic shift (≥ -0.50 D) occurred in 26 (81%) single eyes during the treatment. The median myopic shift was -0.63 D (min -0.25 D/max -1.88 D) in the OD, and -0.69 D (min -0.38 D/max -2.25 D) in the OS. No myopic shift appeared in the pseudophakic patients; the median refractive changes were +0.06 D (min -0.13 D/max +0.25 D) in the OD and +0.13 D (min 0.00 D/max +0.25 D) in the OS. Intraocular pressure, serum electrolytes, glucose, and glycosylated hemoglobin remained unchanged. CONCLUSIONS: Myopic shifts occurred in phakic but not in pseudophakic eyes during HBO therapy. The myopic shifts must be attributed to changes in the crystalline lens.

Hypermetropia-succeeded myopia after hyperbaric oxygen therapy.

A 58-year-old man presented with a change in vision during hyperbaric oxygen (HBO) therapy. Subsequent follow-up visits showed a hypermetropic shift, which succeeded the myopic shift after each of two series of HBO treatments. The maximal refractive amplitude was 3.00 D (range -1.37 D to +1.62 D) in the right eye and 2.75 D (range -1.25 D to + 1.50 D) in the left eye. Refraction stabilized after 1.5 years at +0.62 D and +0.50 D to pretreatment values in the right and left eye, respectively. The findings are discussed with regard to possible changes in the structure of the lens.

Ocular refractive changes in patients receiving hyperbaric oxygen administered by oronasal mask or hood.

PURPOSE: The aim of this study was to quantify ocular refractive changes after a standard hyperbaric oxygen (HBO) treatment protocol and to characterize the time period of recovery. PATIENTS AND METHODS: Hyperbaric oxygen therapy was given for 90 min daily at a pressure of 240 kPa for 21 days. Oxygen was administered to 20 patients using an oronasal mask and to 12 patients using a hood. Follow-up examinations were carried out 2-4 days after treatment, and thereafter regularly for up to 10 weeks in both groups. Refraction was assessed automatically and by the monocular subjective refraction method. A subgroup of nine of the 20 patients to whom oxygen was administered by an oronasal mask underwent a separate eye examination, which included crystalline lens opacity measurements and LOCS III gradings. RESULTS: In the patients given oxygen by mask, there was a significant myopic shift in the mean spherical equivalent, which was largest 2-4 days after treatment. The shift was - 0.55 +/- 0.40 D in the right eye and - 0.53 +/- 0.42 D in the left eye. In the patients given oxygen by hood, the largest shift was observed after 12-16 days, and was - 1.06 +/- 0.52 D in the right eye and - 1.10 +/- 0.57 D in the left eye. The refractive changes returned to baseline 6 weeks and 10 weeks after HBO treatment, respectively. No significant changes in crystalline lens transparency were revealed. CONCLUSIONS: The myopic shift after HBO therapy recovers within 10 weeks and may be more pronounced when patients are given oxygen using a hood compared with using an oronasal mask.