Clinical trial NCT04424069: OCTA Analysis of Macular and Papillary Perfusion After Refractive Surgery in Myopes
Official title: Optical Coherence Tomography Angiography Analysis of Macular and Papillary Perfusion After Variable Refractive Surgery Methods in Myopic Patients
Study type: INTERVENTIONAL
Overall status: UNKNOWN
Phase: NA
Conditions: Myopia
Perfusion; Complications
Lead sponsor: Tanta University
Sponsor class: OTHER
First posted: 2020-06-09
Enrollment: 100
Sex: ALL
Minimum age (years): 18
Maximum age (years): 35
Standard ages: ADULT
Accepts healthy volunteers: no
Allocation: NON_RANDOMIZED
Intervention model: PARALLEL
Primary purpose: SCREENING

Brief summary: Refractive surgery for correction of myopia is very common nowadays. However, various refractive techniques may be associated with increase in the IOP, especially during flap creation. It is assumed that marked intraoperative IOP increase lead to macular and optic disc head circulation compromise. The purpose of this study is to assess the change of macular and papillary perfusion, using optical coherence tomography angiography (OCTA) imaging of the macula and optic disc of myopic patients before and after various refractive surgery methods.

Detailed description: Myopia is the most prevalent ocular disorder in children worldwide, and one of the major causes of visual deterioration in all age groups. Highest prevalence rates are in East Asian countries (affecting up to 83% of Singaporean teenagers), however, it is very common in all other countries. While mild to moderate myopia usually stabilizes within the third decade, pathological myopia is associated with progressive globe elongation, and development of various macular complications including; foveoschisis, choroidal neovascularization (CNV), myopic macular hole, and myopic vitreomacular traction (VMT).

Refractive surgery has become popular for correcting ametropia including myopia. Most commonly used refractive procedures include corneal refractive surgeries especially laser in-situ keratomileusis (LASIK), and Photorefractive keratectomy (PRK), Phakic Intraocular Lenses (Phakic IOLs) and refractive lens exchange.

In LASIK, the creation of a corneal lamellar flap requires placement of a suction ring on the anterior segment of the eye, which transiently elevates the intraocular pressure (IOP) to levels exceeding 65 mmHg. Experimental studies in animal eyes have found that the IOP can increase to between 80 mmHg and 360 mmHg during this vacuum phase and lamellar cut with the microkeratome. Recent advances utilizing the femtosecond laser may serve as an alternative to the mechanical microkeratome, with a low-pressure suction ring. In studies using porcine eyes, the IOP during the suctioning or laser application phase reached a maximum of 135 mmHg using the femtosecond laser, lower than pressures reached with a traditional microkeratome, but for a longer duration of time. Similarly in refractive lens procedures, intraoperative IOP was found to exceed 60 mmHg.

Intraocular pressure elevation during refractive procedures may cause a reduction in the perfusion of the retina and optic nerve head, posterior displacement of the lamina cribrosa, and a decline in ocular perfusion pressure of the posterior ciliary arteries. Although this IOP elevation is temporary, the potential for ischemic or pressure-induced damage to the optic nerve head and the retinal nerve fiber layer exists.

Optical coherence tomography angiography (OCTA) is a recent noninvasive imaging technique that allows for volumetric visualization of eye vasculature. OCTA has shown promise in better elucidating the pathophysiology of several retinal vascular diseases. Swept-source OCTA uses long wavelength ̰ 1,050nm, which can penetrate through deeper layers of the eye and can traverse opacities of media such as cataracts, hemorrhages and vitreous opacities \[6\]. Optical coherence tomographic angiograms can further be manually or automatically segmented with preprogrammed software to highlight individual layers of the retina, optic nerve head choriocapillaris, and choroid. The user can either analyze en face images extending from the inner limiting membrane to choroid or use automated views to locate a vascular or structural lesion within the retina.

The purpose of this study is to assess the change of macular and papillary perfusion, using optical coherence tomography angiography (OCTA) imaging of the macula and optic disc of myopic patients subject to various refractive surgery methods. We will compare between these methods to evaluate which one is associated with least adverse effect on ocular perfusion. To date no such evaluation has been done using OCTA, because of relatively recent onset of this technology. Traditional imaging methods such as color fundus photography and fluorescein angiography have limited resolution for retinal vasculature that mad such evaluation in the past using these methods not feasible, however, OCTA is very promising for the proper analysis of changes in the ocular perfusion. Results of this study will have significant clinical and practical implications and may change the approach for surgical correction of such patients.

Eligibility criteria: Inclusion Criteria:

1. Age: between 20 - 35 years
2. Patients: who are seeking and fit for refractive surgery
3. Spherical equivalent refractive error: between (-2 to -9 D)

Exclusion Criteria:

1. Maculopathies (hereditary or acquired)
2. optic nerve head pathologies (tilted disc, drusen, optic disc edema, atrophy, etc.)
3. optic neuropathies (demyelinating, infectious, ischemic, etc.)
4. adjusted IOP for central corneal thickness more than 21 mmHg
5. surgery-induced corneal edema
6. dense cataracts that can disrupt images
7. systemic diseases (vasculitis, diabetes mellitus, hypertension, etc.)
8. any previous ocular surgery,
9. patients with bad quality images or complicated surgeries will be excluded

Primary outcomes:
measure: Vessel density from enface OCT angiogram
timeFrame: 6 months
Secondary outcomes:
Other outcomes:
Locations:
city: Tanta
country: Egypt
facility: Ophthalmology Department, Faculty of medicine, Tanta Univeristy
Study officials:
affiliation: Tanta University
name: Rauf A gaber, MD
role: STUDY_CHAIR
References:
citation: Flitcroft DI, He M, Jonas JB, Jong M, Naidoo K, Ohno-Matsui K, Rahi J, Resnikoff S, Vitale S, Yannuzzi L. IMI - Defining and Classifying Myopia: A Proposed Set of Standards for Clinical and Epidemiologic Studies. Invest Ophthalmol Vis Sci. 2019 Feb 28;60(3):M20-M30. doi: 10.1167/iovs.18-25957.
citation: Renones de Abajo J, Estevez Jorge B, Gonzalez Martin JM, Carreras Diaz H, Loro Ferrer JF, Anton Lopez A. Effect of femtosecond laser-assisted lens surgery on the optic nerve head and the macula. Int J Ophthalmol. 2019 Jun 18;12(6):961-966. doi: 10.18240/ijo.2019.06.13. eCollection 2019.
citation: Vetter JM, Schirra A, Garcia-Bardon D, Lorenz K, Weingartner WE, Sekundo W. Comparison of intraocular pressure during corneal flap preparation between a femtosecond laser and a mechanical microkeratome in porcine eyes. Cornea. 2011 Oct;30(10):1150-4. doi: 10.1097/ICO.0b013e318212110a.
citation: Khng C, Packer M, Fine IH, Hoffman RS, Moreira FB. Intraocular pressure during phacoemulsification. J Cataract Refract Surg. 2006 Feb;32(2):301-8. doi: 10.1016/j.jcrs.2005.08.062.
citation: Whitson JT, McCulley JP, Cavanagh HD, Song J, Bowman RW, Hertzog L. Effect of laser in situ keratomileusis on optic nerve head topography and retinal nerve fiber layer thickness. J Cataract Refract Surg. 2003 Dec;29(12):2302-5. doi: 10.1016/s0886-3350(03)00466-8.
citation: Or C, Sabrosa AS, Sorour O, Arya M, Waheed N. Use of OCTA, FA, and Ultra-Widefield Imaging in Quantifying Retinal Ischemia: A Review. Asia Pac J Ophthalmol (Phila). 2018 Jan-Feb;7(1):46-51. doi: 10.22608/APO.201812. Epub 2018 Feb 13.