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.
Objective To investigate the refractive changes of ocular measurable factors due to scleral buckling surgery. Methods A total of 86 eyes of successful rhegmatogenous retinal detachment with a higher encircling scleral buckle underwent A-scan and keratometer examination before surgery as well as l week,4 and 12 weeks after surgery.The refractive factors included the depth of anterior chamber,thickness of lens,axial length of eye,corneal curvature and refraction of eye were detected pre- and post-operatively. Results Compared with preoperation,the depth of anterior chamber was decreased significantly at the lst,4th and 12th postoperative week(P＜0.05),while no significant change of the axial length of eye was observed.The thickness of lens was increased significantly and the refractive error was myopic shifted at the lst and 4th week after operation(P＜0.05),but no significant change was observed at the 12th postoperative week.Statistically significant difference was also observed in corneal curvature of central axis in the local bucklele;1 quadrant with encircling group between preoperation and the lst and 4th postoperative week. Conclusions With higher encircling scleral buckle,the refractive change after buckling surgery may be caused primarily by the shallowing of anterior chamber and thickening of lens. (Chin J Ocul Fundus Dis, 1999, 15: 227-229)
Objective To observe visual field outcome and refractive status of patients with retinopathy of prematurity (ROP) treated by laser photocoagulation. Method The data of 39 ROP patients (73 eyes) who received laser photocoagulation were retrospectively analyzed and compared with 13 normal control subjects (25 eyes) whose age and sex were matched with ROP group. There were 24 males (45 eyes) and 15 females (28 eyes) in ROP group, with an average age of (7.0±1.28) years. The first laser treatment was carried out at postnatal age (PA) of (38.74±3.82) weeks, the birth weight (BW) of (1402.33±369.61) g and the number of laser burns was (517.86±277.40). The control group included 7 females (13 eyes) and 6 males (12 eyes), with an average age of (7.17±0.96) years. The age (t=0.691) and gender (χ2=1.425) were comparable between the two groups (P=0.491, 0.233). The data of patients and controls were retrospectively analyzed including best corrected visual acuity, refractive examination, automated perimetry test. The differences of the mean deviation (MD) of visual field and the spherical equivalent (SE) between these two groups were comparatively observed. ROP patients were divided into no VF loss group (MD≤2 dB) and VF loss group (MD＞2 dB), mild VF loss group (MD≤6 dB) and moderate VF loss group (MD＞6 dB) according to the results of automated perimetry test, the differences of gestational age (GA), PA, BW, number of laser burns and SE between these groups were comparatively observed. Results The MD in ROP group and control group were 4.87±5.12 dB and 1.27±3.34 dB, respectively; the difference between the two groups was statistically significant (t=–4.01,P＜0.001). The subgroup analysis showed that BW, number of laser burns, and SE were significantly different between no VF loss group and VF loss group (t=2.074, –1.996, –2.162;P=0.042, 0.026, 0.034); while the GA was not significantly different between these two groups (t=1.973,P=0.052). The difference of PA was not statistical significant different between mild VF loss group and moderate VF loss group (t=2.03,P=0.051) and SE was significantly different between the above two groups (t=3.283,P=0.002). For refractive outcomes, the BW and ROP stage correlated with SE significantly (r=–0.304, –0.387;P=0.015, 0.002). The mean BCVA in ROP group was 0.84±0.23, and 59 eyes (91.2%) with BCVA better than 0.5. Conclusion Laser treatment for ROP tends to have less effect on long term refractive status and VF loss, with good visual outcome.
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 investigate the refractive shift after combined surgery （phacoemulsification, intraocular lens implantation and vitrectomy） by comparing the difference between the predictive and postoperative refractive power.Methods The clinical data of 44 patients (48 eyes) underwent combined surgery (combined group) and 30 patients (50 eyes) underwent cataract surgery (cataract group) were retrospective analyzed. Combined group was further divided into two sub-groups by the kind of tamponade: balanced salt solution group and gas group. Before surgery, axial length and corneal curvature were measured, and the predictive spherical equivalent (PSE) was calculated. Axial length, corneal curvature and actual spherical equivalent (ASE) were measured in six months after surgery. The differences between PSE and ASE were compared between combined group and cataract group, balanced salt solution group and gas group.Results In combined group,the mean PSE was (-0.10plusmn;0.42) D and ASE was（-1.00plusmn;1.10） D, and the difference was significant（t=6.687, P＜0.05）. Patients underwent combined surgery showed a statistically significant myopic shift compared with those underwent simple cataract surgery （t=-3.792,P＜0.05）, the refractive shift of balanced salt solution group and gas group were (-0.76plusmn;0.89） and （-1.19plusmn;0.94） D respectively, and there was no significant difference（t=-1.530,P＞0.05）.Conclusion Combined surgery of phacoemulsification and vitrectomy tends to shift the actual refractive status to myopia.
Objective To verify the changes of optics and refraction of the eyes after retinal detachment surgery with the tamponade of silicone oil in vitreous cavity. Methods The optical calculation was taken as the following by using the parameter of Gullstrand model eye:（1）The refraction of silicone filled eye in non-accommodative status;（2）The refraction of silicone filled eye in non-accommodative status;（3）The aniseikonia analysis when one eye filled with the silicone oil;（4）The IOL power re-calculation． Results （1） Compa red with the normal eye,the eye filled with silicone oil is moved toward high hyperopia of +9．19 D;（2）When corrected,the accommodation amplitude reduced 1.42 D induced by filling silicone oil. Conclusion When eye filled with silicone oil,the change of refractive power tends to be highly hyperopic,the amplitude of accommodation decreased,and the regular IOL power calculation formula is no longer available. (Chin J Ocul Fundus Dis，2000，16：139-212)
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)