Efficacy of Hyperbaric Oxygen Therapy on Central Corneal Thickness, Intraocular Pressure, and Nerve Fiber Layer in Patients with Type 2 Diabetes: A Prospective Cohort Study

The effect of hyperbaric oxygen therapy on corneal endothelial structure and anterior segment parameters

PURPOSE

To assess the effect of hyperbaric oxygen therapy (HBOT) on corneal endothelial structure and anterior segment parameters in healthy eyes.

METHODS

17 eyes of 17 patients who were scheduled to receive HBOT for other than ophthalmologic indications were investigated in this prospective study. Central corneal thickness (CCT) and corneal endothelial properties were evaluated using a specular microscope. Endothelial cell density (ECD), average cell area (AVG), coefficient of variation in cell size (CV), percentage of hexagonal cells (HEX), CCT, intraocular pressure (IOP), spherical equivalent (SE), axial length (AL) and anterior chamber depth (ACD) values were measured before the HBOT, after the 1st session, and after the 20th session of therapy.

RESULTS

47% of the patients (n = 8) received HBOT because of avascular necrosis, 35% (n = 6) due to sudden hearing loss, 12% (n = 2) for diabetic foot, and 6% (n = 1) for wound infection. The mean IOP was 14,80 mmHg before HBOT, 14,20 mmHg after the 1st session, and 13,73 mmHg after the 20th session. The mean ACD was 3,38 mm before HBOT, 3,34 mm after the 1st session, and 3,16 mm after the 20th session. Although the mean IOP and ACD decreased after HBOT sessions, it was not statistically significant (p > 0.05). A significant reduction was observed in SE values after 20 sessions of HBOT compared to the values measured before HBOT (p = 0,009). The mean ECD was 2572,53 ± 261,51 cells/mm2 before HBOT, 2554,47 ± 236,13 after the 1st session, and 2563,13 ± 226,92 after the 20th session. When the corneal properties measured before and after HBOT sessions were compared, no significant difference was found in terms of CCT, ECD, AVG, CV, and HEX (p > 0.05).

CONCLUSION

We observed no significant change in CCT, corneal endothelial layer properties, and anterior segment morphology after the 1st session, and after the 20th session of HBOT. Although HBOT reduced IOP and ACD, it was not statistically significant. HBOT may lead to a significant decrease in SE values after the 20th session.

Oxygen-Carrying Capacity of Perfluorohexyloctane, a Novel Eye Drop for Dry Eye Disease

Objective

One-hundred percent perfluorohexyloctane (PFHO) is a water-free, preservative-free eye drop approved by the Food and Drug Administration in the United States for the treatment of dry eye disease. PFHO has shown relief of dry eye signs and symptoms in clinical trials and has potent antievaporative action in vitro. The objective of this study was to measure the level of oxygen in PFHO.

Methods

T1 relaxation times (time taken for proton spins to translate from a random alignment to an alignment with the main magnetic field) for fluorine-19 in perfluorohexyloctane were measured using fluorine-19 nuclear magnetic resonance spectroscopy. The level of oxygen was interpolated from published data.

Results

The hydrogen-1 and fluorine-19 nuclear magnetic resonance spectra of PFHO were well resolved and the resonance assignments and intensities were as expected. The T1 values calculated for the CF₃ group resonance in the current study was 0.901 seconds and 1.12 seconds at 25 °C and 37 °C, respectively. The T1 values for the CF₂ group resonances increased by 17% to 24% with an increase in temperature from 25 °C to 37 °C. The mean (SD) partial pressure of oxygen in PFHO was calculated to be 257 (36) mm Hg and 270 (38) mm Hg at 25 °C and 37 °C, respectively.

Conclusions

The current study confirms that PFHO contains a significant amount of oxygen, more so than that calculated for tears in equilibrium with air. Once instilled on the eye, PFHO is not expected to be a barrier to the oxygen necessary for a healthy cornea and may in fact deliver nonreactive oxygen to the cornea to facilitate healing in patients with dry eye disease.

THE EFFECT OF HYPERBARIC OXYGEN THERAPY ON RETINA, CHOROIDAL THICKNESS, AND CHOROIDAL VASCULARITY INDEX

PURPOSE

To determine the acute and cumulative effect of hyperbaric oxygen therapy (HBOT) on retina and choroid tissue in healthy eyes.

MATERIAL AND METHODS

Thirty-five subjects who were planned to undergo HBOT for non-ophthalmologic indications comprised the population of this prospective study. Central macular thickness (CMT), retinal nerve fiber layer (RNFL), and choroidal thickness (CT) (3 points: subfoveal area, 500 µm nasal and fovea temporal) were measured using spectral-domain optical coherence tomography (SD-OCT) before HBOT and half an hour after the 1st and 20th sessions of HBOT. The subfoveal choroidal area was segmented using ImageJ software with the binarization technique on enhanced depth imaging (EDI) OCT images. Choroidal area (CA), luminal area (LA), and stromal area (SA) were calculated. Choroidal vascularity index (CVI) was determined as the ratio between LA and CA.

RESULTS

The right eyes of 35 patients aged between 22 and 59 years were enrolled in the study. The mean CMT values of the patients were 259.36 ± 22.31 µm, 256.94 ± 22.72 µm, and 254.58 ± 23.02 µm before HBOT, after the 1st session, and after the 20th session, respectively. The change in CMT values before and after HBOT was statistically significant (p=0.001). When the patients' RNFL, CT, CA, SA, LA, and CVI changes before and after the HBOT were examined, no statistically significant difference was found (p>0.05).

CONCLUSIONS

Our study is the first to jointly evaluate the effect of HBOT on the vascular and stromal components of the choroid and macula in healthy eyes. Due to its thinning effect on the macula, it can be preferred as an adjunctive and facilitating treatment option in addition to current treatments in patients with macular edema due to retinal vascular disorders.

Corneal Endothelial Cell Changes After Femtosecond Laser-Assisted Cataract Surgery in Diabetic and Nondiabetic Patients

OBJECTIVE

To compare corneal endothelial cell changes after femtosecond laser-assisted cataract surgery (FLACS) in diabetic and nondiabetic patients.

METHODS

This retrospective study included patients with cataract who underwent FLACS performed by a single surgeon between August 2018 and November 2020. Changes in corneal endothelial cell density (ECD), hexagonality, coefficient of variation in cell size (CV), and central corneal thickness (CCT) at baseline and at the 1-month and 3-month postoperative follow-ups were investigated by dividing the patients into diabetic and nondiabetic groups.

RESULTS

We included 75 patients (60% men, mean age: 57.7±11.4 years, range: 27-80 years) in the analysis: 31 diabetic patients (64% men, mean age: 58.7±11.9 years, range: 27-79 years) and 44 nondiabetic patients (56% men, mean age: 57.1±11.3 years, range: 34-80 years). No differences were observed between the two groups as regards preoperative and intraoperative parameters, the mean postoperative ECD, hexagonality, and CV. At 1 month postoperatively, the CCT was significantly greater in the diabetic group (P=0.034); however, at 3 months, there was no significant difference between the two groups (P=0.927).

CONCLUSIONS

Changes in postoperative corneal endothelial cells were comparable between patients with and without diabetes after FLACS. Femtosecond laser-assisted cataract surgery seems to cause less damage to the corneal endothelium in diabetic patients because it uses less phacoemulsification energy.