Myopia prevalence is rising globally and high myopia is associated with sight-threatening complications such as macular degeneration, choroidal neovascularization, and retinal detachment. Characteristic structural changes in myopia include axial elongation and mechanical thinning of the choroid and retina, and studies have also reported reduced retinal perfusion in highly myopic eyes. Optical coherence tomography angiography (OCTA) provides noninvasive, high-resolution structural and vascular imaging of posterior segment layers and can distinguish choroidal and retinal blood flow without dye injection. This study applied OCTA to a rat lens-induced myopia (LIM) model to quantify axial length, choroidal and retinal layer thicknesses, and inner retinal blood flow, aiming to inform mechanistic research and translational imaging biomarkers for early detection of myopia-related retinal lesions.
Twenty SPF Sprague–Dawley rats (age 21 days; 65–75 g; equal males and females) were purchased and housed under standard barrier conditions with a 12-hour light/dark cycle, temperature 22 ± 1°C and humidity 55 ± 5%. After a 7-day acclimation period and exclusion of animals with ocular abnormalities, rats were randomly assigned to a lens-induced myopia (LIM) group or normal control (NC) group. The study had institutional approval from the Animal Ethics Committee of the Second Affiliated Hospital of Liaoning University of Traditional Chinese Medicine and reported the experimental animal license.
In the LIM group, under intraperitoneal sodium pentobarbital anesthesia, a −5 diopter (−5D) defocus lens (≈1.7 cm diameter) was sutured around the periocular skin of the right eye using 5−0 polyester braided suture, covering the eye without contacting the globe or impairing blinking. The periocular skin was disinfected and topical tobramycin-dexamethasone drops were applied to the suture site postoperatively to prevent infection. The lens was inspected daily and cleaned or re-secured as needed to maintain constant defocus. Eyes that developed media opacity during the experiment were excluded. The lens was maintained for 8 continuous weeks. In both LIM and NC groups, the right eye served as the experimental eye and the left eye as an internal, untreated control.
After 8 weeks, animals were anesthetized and pupils dilated using compound tropicamide. Axial length (AL) was measured with the Intalight Saiwei Ruyi Panoramic Eye OCT in the AS Cube 16 mm × 16 mm scanning mode. AL was defined as the distance from the high-reflective anterior corneal surface signal to the retinal pigment epithelium (RPE) high-reflective signal. Each measurement was performed three times by the same operator and averaged. The study used OCT cross-sections through the optic disc for biometric reference.
Choroidal images were obtained using a 33 Line R16 scan pattern to capture horizontal cross-sections through the optic disc. Three concentric circles (2 mm, 4 mm, 6 mm diameters) centered on the optic disc provided reference locations. Choroidal thickness (CT) was measured from the RPE to the inner scleral border at six points on nasal and temporal meridians located at 1,000 μm, 2,000 μm, and 3,000 μm from the optic disc center.
Retinal thickness measurements used the same 33 Line R16 horizontal scans and concentric ring layout. The inner retinal layer (IRL) was defined from the inner limiting membrane (ILM) to the outer plexiform layer (OPL); the outer retinal layer (ORL) was defined from the inner edge of the OPL to the RPE. Thicknesses for IRL, ORL, and whole retina were measured at the same six nasal and temporal points (1,000 μm, 2,000 μm, 3,000 μm).
OCTA segmentation permitted quantification of blood flow density in the inner retinal layer. The instrument’s posterior-segment angiography capability was used to generate vascular density maps of the inner retina for comparison between LIM and NC eyes. The study analyzed intraretinal perfusion metrics and compared values across groups.
Following 8 weeks of lens-induced defocus, LIM eyes showed longer axial length compared with normal control eyes. OCTA-derived structural measures demonstrated decreased choroidal thickness and thinning of the inner, outer, and whole retinal layers in LIM eyes at the measured nasal and temporal points. In addition, inner retinal blood flow density assessed by OCTA was reduced in the LIM group. The authors report that most intergroup differences reached statistical significance using t-tests. The manuscript includes figures and supporting data for the numerical results; specific numeric thickness and perfusion values were provided in the original article’s figures and tables.
Using noninvasive OCTA imaging, the study identified three consistent features of the LIM rat model: axial elongation, choroidal and retinal thinning, and decreased inner retinal perfusion (retinal hypoperfusion). These observations align with reported human myopia morphological changes and suggest that structural stretching of the posterior segment is accompanied by vascular alterations detectable by OCTA. The authors highlight OCTA’s value for longitudinal, high-resolution monitoring of ocular structural and vascular changes in experimental myopia and propose OCTA-based metrics as candidate translational biomarkers for early screening of myopia-related retinal lesions.
The work supports use of OCTA to noninvasively quantify choroidal and retinal structural and blood flow changes in an animal myopia model. These imaging biomarkers may be translatable to clinical screening and early detection of retinal changes associated with progressive or high myopia, facilitating studies of pathogenesis and preventive strategies.
The presented excerpt describes experimental design, imaging methods, and reported directional outcomes (elongation, thinning, hypoperfusion). Exact numerical results, variance estimates, and detailed p values are reported in the full manuscript figures and supporting files but were not transcribed in the provided source excerpt. The article states that all relevant data are available within the manuscript and supporting information. No external funding or competing interests were declared.