Purpose To investigate the influence of ametropia on stereopsis and its mechanism by using the disparity evoked potential testing. Methods A new set of static random dot stereograms was utilized as a stimulation to elicit the disparity evoked potentials in 21 ametropes and 40 stereo normal subjects. Rezults The P250 wave,which was related to stereoscopic stimulation in ametropes,was recorded in both the ametropes and emetropic stereo normal persons in this series,and the characteristic changes of P250 wave with increasing visual disparity in ametropes were similar to those in normal subjects.The differences of mean amplitudes and latencies of P250 waves between myopes and hyperopes were not significant. Conclusion Ametropia in full correction dose not significanly affect the function of stereopsis. (Chin J Ocul Fundus Dis,1998,14:225-227)
In order to understand how the biomechanical properties of rabbit cornea change over time after corneal ablation, 21 healthy adult rabbits were used in this study, with the left eye as experimental side and the right eye as the control side. Firstly, a lamellar knife was used to remove a portion of the anterior corneal surface tissue (30%~50% of the original corneal thickness) from the left eye of each rabbit, as an animal model simulating corneal refractive surgery. Secondly, postoperative experimental rabbits were kept for one, three, or six months until being euthanized. Strip specimens were produced using their corneas in vitro to perform a uniaxial tensile test with an average loading-unloading rate of approximately 0.16 mm/s. Finally, the visco-hyperelastic material constitutive model was used to fit the data. The results showed that there was a significant difference in the viscoelastic parameters of the corneas between the experimental and the control eyes at the first and third postoperative months. There was a difference in tangential modulus between the experimental and the control eyes at strain levels of 0.02 and 0.05 at the third postoperative month. There was no significant difference in biomechanical parameters between the experimental and the control eyes at the sixth postoperative month. These results indicate that compared with the control eyes, the biomechanical properties of the experimental eyes vary over postoperative time. At the third postoperative month, the ratio of corneal tangential modulus between the experimental and the control eyes significantly increased, and then decreased. This work lays a preliminary foundation for understanding the biomechanical properties of the cornea after corneal refractive surgery based on rapid testing data obtained clinically.
Objective To observe the distribution of macular thickness and its relationship with axial length, gender, refraction status and race in six-year-old children. Methods 1543 six-year-old children from 34 schools in Sydney were randomly selected. The thickness of center macula（CM）, inner macula（IM）and outer macula（OM）were measured by optical coherence tomography（OCT）, the differences of macular thickness between different genders and races were comparatively analyzed. The axial length and refraction status of all children were measured by IOL Master and autorefractor RK-F1 respectively. Results The CM, IM and OM thickness of all those six-year-old children were normally distributed，on average they were 193.6, 264.3 and 236.9 mu;m respectively,the differences were statistically significant（t=0.40,0.08,0.20;P＜0.05）. The CM,IM and OM average thickness was 194.2,264.9,229.0 mu;m for boys and 189.3,262.5,231.5 mu;m for girls respectively. CM and IM thickness of boys were thicker than those in girls（t=0.15,0.11;P＜0.05）. The CM,IM and OM average thickness was 196.0,265.2,237.5 mu;m for White kids,186.0,262.3,236.5 mu;m for East Asia kids and 19.4,263.7,233.8 mu;m for Central East kids respectively. The CM and IM thickness of White and Central East children were significantly thicker than East Asia children (t=0.12,0.15;Plt;0.05）. There was no difference between these three races in OM thickness（t=0.16,P=0.6）. The IM and OM were thinner with longer axial length (Plt;0.05). The CM,IM and OM thickness was thicker with higher hyperopic degrees (Plt;0.05). Conclusions Macular thickness was normally distributed in six-year-old children and was significantly affected by gender, race, axial length and refraction status.
ObjectiveTo observe the changes in refractive status of eyes with idiopathic macular hole (IMH) after vitrectomy and phacoemulsification and IOL implantation (combined surgery).MethodsA retrospective clinical study. From January 2016 to June 2019, 51patients (56 eyes) of IMH who underwent combined surgery at the Tianjin Medical University Eye Hospital. were included in the study. Among them, there were 17 males and 34 females with the average age of 66.79±4.33 years. All the affected eyes underwent BCVA, retinoscopy and axial length (AL) measurement. The IOL power was calculated according to the SRK-T formula and the refractive power (predicted value) was predicted. The average BCVA of the affected eye was 0.20±0.13. The average anterior chamber depth was 2.89±0.28 mm. The average △corneal astigmatism was 0.73±0.43 D, the average AL was 22.92±0.70 mm, the average predicted refractive power was 0.10±0.66 D. All the affected eyes underwent standard transciliary flat part three-channel 25G combined surgery. Six months after the operation, the actual value (actual value) of the diopter after the operation was measured with the same equipment and method before the operation. Paired t test was used to compare the difference between the predicted value and the actual value.ResultsSix months after the operation, the actual value of the refractive power was -0.19±0.64 D. Compared with the pre-operative refractive power, the difference was not statistically significant (t=1.665, P=0.102). The difference between the actual value and the predicted value was －0.33±0.81 D.ConclusionsThe refractive status of the IMH eye undergoes myopia drift after combined surgery. The preoperative IOL power budget can be appropriately reserved for +0.3 D hyperopia.
Cataract combined with retinopathy can seriously affect the vision of patients. Vitrectomy combined with one-stage implantation of multi-focal intraocular lens (MIOL) has been paid more and more attention. The application of MIOL shows potential in improving the visual quality of patients, but its effect is affected by many factors, and refractive drift is a key problem to be solved. At present, the research mainly focuses on cataract patients with high myopia, and further research on other types of retinopathy is needed. In the future, multi-center, large-sample, long-term clinical studies and interdisciplinary cooperation are needed to optimize surgical and management programs to enhance the application effect of MIOL in the treatment of retinopathy and improve the quality of life of patients.
Objective To investigate the characteristic of the multifocal visual evoked potentials(MVEP)and the visual function across the visual field in anisometropic amblyopes and isometropic amblyopes. Methods MVEP from 32 anisometropic amblyopic eyes and 31 control eyes were tested. Results In anisometropic amblyopic eyes,the latencies of MVEP were significantly prolonged．The amplitudes of MVEP were significantly attenuated in the central region of the visual field,and these phenomena gradually reduced with the increase of the eccentricity． Conclusion The visual function of anisometropic amblyopic eyes is reduced more significantly in the central region than in the peripheral region of the visual field. (Chin J Ocul Fundus Dis,20000,16:27-29)