Targeting displacement as an indicator of binocular fixation in normal Chinese adults.

Purpose: The stability of fixation is crucial for the development of visual function. In this study, we quantify the deviation of visual target during fixational and saccadic tasks using eye-tracking technology, reflecting the control ability and characteristics of fixational displacement among healthy adults in a convenient method. Methods: One hundred healthy participants aged between 18 and 55 years were recruited in the study. All participants underwent a complete ophthalmic assessment. The eye positions in the fixational and saccadic tasks were documented and analyzed by the Tobii eye-tracking system. Participants were grouped by age and gender. Targeting displacement (TD), defined as the average displacement between visual target and the mean of fixation points corresponding to that stimuli, was used to quantitatively observe fixational displacement in the horizontal and vertical directions. Result: There was a strong reproducibility of TD as an indicator of fixation (ICC 0.812 to 0.891, p < 0.001). The TD in fixational task was significantly smaller than that of the saccadic task (3.884 ± 0.525 vs. 4.484 ± 0.509, p < 0.001) among normal people. Moreover, the difference of TD in the horizontal and vertical meridians was related to the nature of the task: In the fixational task, the TD in horizontal was smaller than that in the vertical (p < 0.001), whereas the TD in horizontal was larger than that in vertical in the saccadic task (p = 0.003). In the different age and gender groups: There was no significant difference between different gender and age groups in fixational task. However, during the saccadic task, males had smaller TD in the vertical direction than females (4.061 ± 0.495 vs. 4.404 ± 0.484, p = 0.002), and the average TD increased with age, mainly in the vertical direction (all p < 0.05). The fixation stability decreased significantly in the group over 50-years-old. Conclusion: By reporting the fixational displacement of different genders and ages in fixational and saccadic tasks, as well as different longitude lines among normal people, our study might provide an objective, quantitative and convenient reference index for the evaluation of fixation stability in visual impairment diseases and aging phenomenon of visual function.

Microvascular changes in macula and optic nerve head after femtosecond laser-assisted LASIK: an optical coherence tomography angiography study.

BACKGROUND: To measure the microcirculation change of macula and optic nerve head before and after femtosecond laser assisted laser in situ keratomileusis. METHODS: In total 45 eyes from 45 subjects, who underwent FS-LASIK during June 2017 to December 2017 in Guangdong Provincial People's Hospital, were recruited in this study. Vessel density in macula and optic nerve head were measured by optical coherence tomography angiography before and after transient elevation in intraocular pressure caused by application of suction ring during surgery. RESULTS: Vessel density (VD) at superficial (SCP) plexus of macular region did not differ after surgery (F(3,132) = 1.41, P = 0.24), while the deep (DCP) plexus of macular region significantly decreased 1 day after surgery (P = 0.001) but returned to its baseline value 1 month postoperatively (P = 0.1). Vessel density of optic nerve head region had no significant changes after surgery (F(2.51,95.18) = 0.6, P = 0.59). CONCLUSIONS: A short-term temporary decrease of vessel density at deep layer of macular region was observed in eyes undergoing FS-LASIK. However, the retinal capillary density went back to preoperative level 1 month after surgery. Therefore, transient IOP spike during FS-LASIK did not cause long-term decline of retinal microcirculation.

Macular and peripapillary vessel density in myopic eyes of young Chinese adults.

BACKGROUND: The aim of this study was to compare the macular and peripapillary vessel densities in eyes of young Chinese adults with different degrees of myopia and to evaluate the association of macular and peripapillary vessel densities with axial length and retinal nerve fibre layer thickness. METHODS: A total of 128 eyes (mild myopia, 42; moderate myopia, 45; severe myopia, 41) underwent optical coherence tomography angiography imaging. Parameters assessed were vessel densities in the superficial capillary plexus and deep capillary plexus of the macular area, peripapillary vessel density, retinal nerve fibre layer thickness, foveal thickness and foveal avascular zone area (mm2 ). RESULTS: Vessel densities in the macular and peripapillary areas as well as peripapillary retinal nerve fibre layer thickness decreased significantly when comparing high myopia to mild myopia. Axial length was significantly associated with vessel density in the macular area (superficial capillary plexus: r = -0.249, p = 0.008; deep capillary plexus: r = -0.398, p < 0.001), peripapillary area (r = -0.204, p = 0.028), foveal avascular zone area (r = -0.309, p < 0.001), and foveal thickness (r = 0.354, p < 0.001). Negative correlations were found between axial length and peripapillary vessel density as well as retinal nerve fibre layer thickness at the nasal superior, nasal inferior and inferior nasal quadrants. CONCLUSION: Varying degrees of myopia affected macular and peripapillary vessel densities as well as retinal nerve fibre layer thickness in young healthy adults. The high myopic group had the lowest vessel density in the superficial capillary plexus, deep capillary plexus of the macular area and the peripapillary area. With increased axial length, macular and peripapillary vessel densities, retinal nerve fibre layer thickness and foveal avascular zone area reduced while foveal thickness increased.

Virtual Reality Assessment Reveals Myopic Regression After ICL Implantation in High Myopia.

PURPOSE: To investigate the correlative factors of vision regression after Implantable Collamer Lens (ICL) surgery from the perspective of binocular vision and to develop a predictive model for the refractive change over the long term. METHODS: This was a prospective study of 30 subjects (60 implants), who underwent ICL surgery at Guangdong General Hospital. Corrected distance visual acuity, uncorrected distance visual acuity, spherical equivalent (SE), axial length and binocular examination using virtual reality were analyzed before, 1 month and 1 year after the surgery. RESULTS: Mean SE was (-12.01 ± 0.86) D preoperatively, (-0.44 ± 0.13)D 1 month postoperatively and (-0.97 ± 0.15)D 1 year postoperatively. The average regression 1 year postoperatively (-0.53 ± 0.25D of SE) was significant (P = 0.01). Mean axial length at the base line and 1 year after the surgery was (28.35 ± 0.39) mm and (28.91 ± 0.57) mm. The regression was correlated with the binocular equilibrium difference (r = 0.553, P = 0.002), and the degree of perceptual eye position shift, especially the horizontal shift (r = -0.620, P = 0.000). The important variables relevant to myopic regression were preoperative horizontal perceptual eye position shift (B = -0.007, P = 0.001) and binocular equilibrium difference (B = 0.146, P = 0.012). CONCLUSION: Perceptual eye position deviation and the binocular equilibrium difference could cause binocular gazing instability, and the unstable retinal image created a 'micro retinal-defocus phenomena', leading to an elongation of the axial length and resulting in myopic regression after ICL surgery.

Assessment of Binocular Imbalance with an Augmented Virtual Reality Platform in a Normal Population.

We examined and analyzed binocular imbalance in a group of randomly selected normal subjects with corrected visual acuity of 0.8 or more in both eyes without ocular diseases, by using augmented virtual reality system. This study will quantify the correlation between binocular imbalance in these normal subjects and various spatial frequencies and temporal frequencies in the integrated binocular stimulation mode. A retrospective study was carried out and data from 97 patients (51 males and 46 females) who were diagnosed with no eye diseases, and with corrected binocular visual acuity of 0.8 or more, were collected. Their binocular visual function, Hirschberg test refraction status, and binocular imbalance were assessed using the quantified visual perception stimulation mode in an augmented virtual reality platform. When normal subjects (with corrected binocular vision of 0.8 or more without ocular diseases) were assessed using the integrated binocular stimulation mode with different temporal and spatial frequencies, a gradual reduction of binocular imbalance could be observed when spatial frequencies were increased. When contrast balance was adjusted, binocular imbalance was more prevalent in the horizontal state compared with the vertical state. This was seen when patients were stimulated by different temporal frequencies in the virtual reality testing mode. 17.53% and 29.90% of participants reached complete binocular fusion under low temporal frequency stimulation and high temporal frequency stimulation, respectively, while binocular imbalance was found in 65.9% and 62.89% of participants who were stimulated, respectively, by low temporal frequency and high temporal frequency. In addition, 16.5% and 7.21% experienced severe binocular imbalance under low temporal and high temporal frequency stimulation, respectively. The integrated binocular stimulation mode under low temporal frequency was more sensitive in detecting binocular imbalance. The status of binocular balance in normal subjects was not the same when stimulated by the augmented virtual reality platform, as many showed varying degrees of binocular imbalance. The results from our clinical study demonstrate that integrated binocular stimulation with different spatial and temporal frequencies enables a more sensitive detection of binocular imbalance, making it a powerful new tool for the diagnosis and analysis of clinical binocular abnormalities. In addition, since more than half of the normal subjects (without eye diseases who has corrected vision of 0.8 or more) exhibited binocular imbalance in our study, we believe that this brief binocular imbalance is likely a transient physiological phenomenon, which is not pathological to visual acuity and function, and should only be seen as pathological when binocular imbalance is prolonged, causing functional deficits such as reading impairment.

Intermittent Exotropia Treatment with Dichoptic Visual Training Using a Unique Virtual Reality Platform.

We evaluated the effect of dichoptic visual training based on a unique virtual reality (VR) platform mounted display in patients with intermittent exotropia (IXT). A total of 25 IXT patients (8 men, 17 women) with a mean age of 12.3 years (range, 5-39 year) were recruited. The Hirschberg test, prism and alternate cover testing (with accommodative targets for fixation at 33 cm in all patients), perceptual eye position (PEP), and stereopsis were evaluated after 1, 3, and 6 months of dichoptic visual neuroplasticity training with a computer-controlled perceptual examination evaluation system. Data collected before and after training were evaluated using SPSS software. After 6 months of perceptual training, a new order stereopsis was established, and eye positions were improved in all 25 patients. After training for 1 and 6 months, the horizontal PEP pixels were much lower than those pretraining, respectively (Δ1-0 = -0.53, p = 0.028; Δ6-0 = -0.80, p = 0.018). There was no statistically significant difference between pretraining and 3 months after training in horizontal PEP (Δ3-0 = -0.29, p = 0.370). There was no significant difference between pretraining and post-training in vertical PEP (p > 0.05). There were significant differences between pretraining and post-training in the cornea's optical reflection and prism diopters (p < 0.01). Dichoptic visual neuroplasticity training based on a VR platform is an effective nonsurgical treatment in patients with IXT. With the VR treatment, the degree of strabismus and stereopsis was improved in IXT patients. Perceptual training with VR can remove obstacles in the visual processing channel and repair defects in visual function. The clinical manifestations of improvement were the decrease in the degree of strabismus and the re-establishment of stereopsis.

Comparison of perceptual eye positions among patients with different degrees of anisometropia.

The aim of this study is to compare the perceptual eye positions (PEPs) among patients with different degrees of anisometropia.A total of 157 patients were recruited into this retrospective study. A detailed ophthalmic examination was conducted on each patient. The degree of refractive errors in the presence of astigmatism was converted into the degree of spherical equivalent (SE). Patients were divided into 3 groups according to the interocular SE difference: severe anisometropia group with interocular SE difference ≥2.50D, mild anisometropia group with interocular SE difference ≥1.00D and <2.50D, and non-anisometropia group with interocular SE difference <1.00D. The vertical and horizontal PEP were measured by a computer-controlled perceptual examination evaluation system. The results obtained from the 3 groups were compared and analyzed.A total of 157 patients were enrolled including 32 patients in the severe anisometropia group, 37 patients in the mild anisometropia group, and 88 patients in the non-anisometropia group. The quartiles of vertical PEP pixels were as follows: 7.50 (5.00, 16.75) in the severe anisometropia group, 5.00 (2.00, 7.50) in the mild anisometropia group, and 5.00 (3.00, 9.00) in the non-anisometropia group, respectively. The vertical PEP pixel was much higher in the severe anisometropia group than that in the other two groups (P < .05). The quartiles of horizontal PEP pixels were as follows: 27.50 (10.75, 67.50) in the severe anisometropia group, 17.00 (7.00, 54.50) in the mild anisometropia group, and 21.50 (11.00, 60.75) in the non-anisometropia group. There were no statistically significant differences among the 3 groups (P > .05).There was an obvious deviation of vertical PEP in patients with anisometropia ≥2.50D, indicating that the instability of vertical PEP might be associated with the development of severe anisometropia.

Biometry and corneal astigmatism in cataract surgery candidates from Southern China.

PURPOSE: To analyze biometry data and corneal astigmatism in cataract candidates from Southern China. SETTING: Guangdong Eye Institute, Guangdong General Hospital, Guangzhou, China. DESIGN: Cross-sectional hospital-based study. METHODS: The axial length (AL), anterior chamber depth (ACD), horizontal corneal diameter (white to white [WTW]), and corneal power (keratometry [K], flat K, steep K) were measured using the IOLMaster system. Ocular biometric data were collected and analyzed between 2007 and 2011. RESULTS: The study comprised 6750 eyes of 4561 consecutive cataract candidates with a mean age of 70.4 years ± 10.5 (SD). The mean AL, ACD, and WTW were 24.07 ± 2.14 mm, 3.01 ± 0.57 mm, and 11.68 ± 0.45 mm, respectively. All values were statistically significantly greater in men than in women (P < .001) and had a significant trend toward a decrease as age increased (P < .001). The mean K value was 44.13 ± 1.63 D. The median corneal astigmatism was 0.90 D (interquartile range, 0.54-1.43). Corneal astigmatism of 1.00 D or greater was found in 2963 eyes (43.9%), and 3590 eyes (53.2%) had against-the-rule (ATR) astigmatism. The axis of corneal astigmatism turned in the ATR direction with age. CONCLUSIONS: This study provides reference data for cataract patients from Southern China. The profiles of ocular biometric data and corneal astigmatism can help improve surgical procedures and intraocular lens design for the Chinese population. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.