Research Progress of the Application of Hypothermia in the Eye

Hypothermia is widely used in the medical field to protect organs or tissues from damage. Different research fields have different explanations of the protection mechanism of hypothermia. Hypothermia is also widely used in the field of ophthalmology, for example, in the eye bank, the preservation of corneal tissue and the preservation of the eyeball. Low temperature can also be applied to some ophthalmic diseases, such as allergic conjunctivitis, retinal ischemia, and retinal hypoxia. It is used to relieve eye symptoms or reduce tissue damage. Hypothermic techniques have important applications in ophthalmic surgery, such as corneal refractive surgery, vitrectomy surgery, and ciliary body cryotherapy for end-stage glaucoma. Hypothermia can reduce the inflammation of the cornea and protect the retinal tissue. The eyeball is a complex organ, including collagen tissue of the eyeball wall and retinal nerve tissue and retinal blood vessels. The mechanism of low temperature protecting eye tissue is complicated. It is important to understand the mechanism of hypothermia and its applications in ophthalmology. This review introduces the mechanism of hypothermia and its application in the eye banks, eye diseases (allergic conjunctivitis, retinal ischemia, and hypoxia), and eye surgeries (corneal transplant surgery, corneal refractive surgery, and vitrectomy).

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On the Possibility of Expanding Indications for Refractive Correction of Ametropia (4 Clinical Cases)

Ophthalmology in Russia ◽

10.18008/1816-5095-2018-2s-174-178 ◽

2018 ◽

Vol 15 (2S) ◽

pp. 174-178

Author(s):

A. D. Chuprov ◽

Yu. V. Kanyukova ◽

A. E. Voronina

Keyword(s):

Visual Acuity ◽

Retinal Detachment ◽

Refractive Surgery ◽

Corneal Tissue ◽

Ophthalmic Surgery ◽

Refractive Correction ◽

Corneal Opacities ◽

The Right ◽

Clinical Cases

Refractive surgery is a dynamically developing field of ophthalmic surgery, which requires studying new approaches for determining indications and contraindications for refractive surgery.Purpose. To investigate the possibility of expanding indications for refractive surgery in conditions related to contraindications on the example of four clinical cases.Material and methods. The study included 4 clinical cases of photorefractive operations in patients with relative contraindications who underwent refractive surgery (Femto-Lasik, photorefractive keratectomy (PRK), phototherapeutic keratectomy (PTK)).Results and discussion. Follow-up period of patients after Femto-Lasik, PRK and PTK was 1 year. During this period, stabilization of such parameters as intraocular pressure (IOP), progression of diabetic retinopathy, visual acuity was detected on all operated eyes. There were no postoperative complications. In the first clinical example, to avoid flap injury pneumotonometry was performed 72 hours after the surgery. IOP indices differed from preoperative ones and were 15 mm Hg because of the flap cut and the removal of part of the corneal tissue as a result of laser ablation. In the second clinical example, BCVA OU was 1.0 throughout the whole follow-up period. In the third clinical example recurrence of retinal detachment and any formations of new zones of peripheral vitreochorioretinal were not observed. BCVA improved up to 0.9–1.0. In the fourth clinical example, 3 months later, the patient complained for “misting” in the right eye. On examination, subepithelial fibroplasia of the 1st degree was revealed. After the course of treatment, the transparency of the cornea was restored. The data of the diagnostic examination after the surgery at the period of 1 month, 3 months did not differ and corresponded to preoperative ones. Diagnostic examination data 1 year after the operation: visual acuity: OD — 1.0; OS — 0.4 sph + 1.0Dcyl + 1.5Dax 45 = 0.8.Conclusion. The presented clinical examples allow us to reconsider the list of relative contraindications for performing refractive operations for compensated diabetes mellitus, glaucoma, retinal detachment, corneal opacities, as it can be performed safely and effectively with good refractive results.

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Time-varying regularity of changes in biomechanical properties of the corneas after removal of anterior corneal tissue

BioMedical Engineering OnLine ◽

10.1186/s12938-021-00948-7 ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Di Zhang ◽

Xiao Qin ◽

Haixia Zhang ◽

Lin Li

Keyword(s):

Elastic Modulus ◽

Stress Relaxation ◽

Refractive Surgery ◽

Biomechanical Properties ◽

Collagen Fibrils ◽

Uniaxial Tensile ◽

Control Group ◽

Corneal Tissue ◽

Corneal Refractive Surgery ◽

Corneal Biomechanical Properties

Abstract Background The corneal biomechanical properties with the prolongation of time after corneal refractive surgery are important for providing a mechanical basis for the occurrence of clinical phenomena such as iatrogenic keratectasia and refractive regression. The aim of this study was to explore the changes of corneal elastic modulus, and stress relaxation properties from the 6-month follow-up observations of rabbits after a removal of anterior corneal tissue in simulation to corneal refractive surgery. Methods The anterior corneal tissue, 6 mm in diameter and 30–50% of the original corneal thickness, the left eye of the rabbit was removed, and the right eye was kept as the control. The rabbits were normally raised and nursed for 6 months, during which corneal morphology data, and both of corneal hysteresis (CH) and corneal resistance factor (CRF) were gathered. Uniaxial tensile tests of corneal strips were performed at months 1, 3, and 6 from 7 animals, and corneal collagen fibrils were observed at months 1, 3, and 6 from 1 rabbit, respectively. Results Compared with the control group, there were statistical differences in the curvature radius at week 2 and month 3, and both CH and CRF at months 1, 2, and 6 in experiment group; there were statistical differences in elastic modulus at 1, 3, and month 6, and stress relaxation degree at month 3 in experiment group. The differences in corneal elastic modulus, stress relaxation degree and the total number of collagen fibrils between experiment and control groups varied gradually with time, and showed significant changes at the 3rd month after the treatment. Conclusions Corneas after a removal of anterior corneal tissue undergo dynamic changes in corneal morphology and biomechanical properties. The first 3 months after treatment could be a critical period. The variation of corneal biomechanical properties is worth considering in predicting corneal deformation after a removal of anterior corneal tissue.

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The use of lenticular tissue in corneal refractive surgery

Fyodorov journal of ophthalmic surgery ◽

10.25276/0235-4160-2021-1-68-72 ◽

2021 ◽

pp. 68-72

Author(s):

S.V. Kostenev ◽

◽

S.A. Borzenok ◽

V.G. Lee ◽

P.O. Nosirov ◽

...

Keyword(s):

Tissue Engineering ◽

Key Words ◽

Refractive Surgery ◽

Future Research ◽

Corneal Tissue ◽

Corneal Perforation ◽

The Future ◽

Corneal Refractive Surgery

Purpose. To identify the problems of using lenticular tissue, its storage, obtaining cell-free scaffolds in corneal tissue engineering, and the possibility of predicting refraction. The unique advantage of Relex Smile technology is that it is a potentially reversible procedure that allows preserve the extracted lenticules and opens up broad possibilities for the use of lenticules in ophthalmic practice in the future. Research in this area demonstrated the potential for implanted autologous and allogeneic lenticules after creating an intracorneal pocket for treating diseases such as presbyopia, corneal perforation, corneal keratectasia, progressive pterygium, progressive keratoconus. In addition, this article presents the results of recent studies describing protocols for cryopreservation and decellularization of lenticules as the most promising methods in tissue engineering in conditions a shortage of donor's cornea. Key words: Relex Smile, lenticule, implantation, cryopreservation, decellularization, tissue engineering.

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Faculty Opinions recommendation of Topical cyclosporine a treatment in corneal refractive surgery and patients with dry eye.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.718546233.793499173 ◽

2014 ◽

Author(s):

Karl Stonecipher

Keyword(s):

Dry Eye ◽

Cyclosporine A ◽

Refractive Surgery ◽

Corneal Refractive Surgery

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Effect of corneal refractive surgery on accommodative and binocular dysfunctions among civilian pilots in Southwest China

BMC Ophthalmology ◽

10.1186/s12886-021-01855-0 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Ye Wu ◽

Zhen Zhang ◽

Meng Liao ◽

Qi Li ◽

Xue Lin Tang ◽

...

Keyword(s):

Binocular Vision ◽

Refractive Surgery ◽

Visual Symptom ◽

Chi Square ◽

Visual Symptoms ◽

Significant Difference ◽

Symptom Scores ◽

Chi Square Test ◽

Corneal Refractive Surgery ◽

Normal Binocular Vision

Abstract Background To analyze whether corneal refractive surgery (CRS) is associated with the distribution of different accommodative dysfunctions (ADs) and binocular dysfunctions (BDs) in civilian pilots. A further aim was to analyze the percentages and visual symptoms associated with ADs and/or BDs in this population. Methods One hundred and eight civilian pilots who underwent CRS from January 2001 to July 2012 (age: 30.33 ± 4.60 years) were enrolled, the mean preoperative SE was − 1.51 ± 1.15 D (range: − 1.00- − 5.00 D). Ninety-nine emmetropic civilian pilots (age: 29.64 ± 3.77 years) who were age- and sex-matched to the CRS group were also enrolled. Refractive status, accommodative and binocular tests of each subject were performed. Visually related symptoms were quantified using the 19-item College of Optometrists in Vision Development Quality of Life (COVD-QOL) questionnaire. The 19 items were summed to obtain visual symptom scores that might indicate visual dysfunctions. The chi-square test was used to analyze differences in percentages of ADs and/or BDs between the CRS and emmetropic groups. The Mann-Whitney U test was used to compare visual symptom scores between pilots with ADs and/or BDs and pilots with normal binocular vision. Results No significant difference was observed between the CRS and emmetropic groups in the overall prevalence of ADs and BDs (15.7% and 15.2% in the CRS and emmetropic groups, respectively; P = 0.185). ADs were present in 4.63% and 3.03% of the CRS and emmetropic group, respectively. BDs were observed in 11.1% and 12.1% of the CRS and emmetropic group, respectively, yielding no significant differences between the groups in the prevalence of ADs or BDs (AD: P = 0.094; BD: P = 0.105). Pilots with ADs and/or BDs had significantly more visual symptoms than pilots with normal binocular vision (p < 0.001). Conclusions CRS for civilian pilots with low-moderate myopia might not impact binocular functions. ADs and/or BDs commonly occur in both emmetropia pilots and pilots who undergo CRS, and pilots with ADs and/or BDs are associated with increased symptoms. This study confirms the importance of a full assessment of binocular visual functions in detecting and remedying these dysfunctions in this specific population.

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Constitutive Laws for Biomechanical Modeling of Refractive Surgery

Journal of Biomechanical Engineering ◽

10.1115/1.2796033 ◽

1996 ◽

Vol 118 (4) ◽

pp. 473-481 ◽

Cited By ~ 122

Author(s):

Michael R. Bryant ◽

Peter J. McDonnell

Keyword(s):

Finite Element ◽

Material Properties ◽

Refractive Surgery ◽

Fiber Optic ◽

Transverse Isotropy ◽

Constitutive Laws ◽

Finite Element Models ◽

Corneal Refractive Surgery ◽

Best Fit ◽

Membrane Inflation

Membrane inflation tests were performed on fresh, intact human corneas using a fiber optic displacement probe to measure the apical displacements. Finite element models of each test were used to identify the material properties for four different constitutive laws commonly used to model corneal refractive surgery. Finite element models of radial keratotomy using the different best-fit constitutive laws were then compared. The results suggest that the nonlinearity in the response of the cornea is material rather than geometric, and that material nonlinearity is important for modeling refractive surgery. It was also found that linear transverse isotropy is incapable of representing the anisotropy that has been experimentally measured by others, and that a hyperelastic law is not suitable for modeling the stiffening response of the cornea.

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