Effect of Ambient Light Exposure on Ocular Fatigue during Sleep

BACKGROUND

To investigate the influence of nocturnal ambient light on visual function and ocular fatigue.

METHODS

Sixty healthy subjects (30 men and 30 women) aged 19 through 29 years with no history of ocular disease were recruited. All subjects spent 3 consecutive nights in the sleep laboratory. During the first and second nights, the subjects were not exposed to light during sleep, but during the third night, they were exposed to ambient light, measuring 5 or 10 lux at the eye level, which was randomly allocated with 30 subjects each. The visual function and ocular fatigue were assessed at 7 a.m. on the 3rd and 4th mornings, using best-corrected visual acuity, refractive error, conjunctival hyperemia, tear break-up time, maximal blinking interval, ocular surface temperature, and subjective symptoms reported on a questionnaire.

RESULTS

Three men and three women subjects failed to complete the study (4 in the 5 lux; 2 from the 10 lux). For the entire 54 subjects, tear break-up time and maximal blinking interval decreased (P = 0.015; 0.010, respectively), and nasal and temporal conjunctival hyperemia increased significantly after sleep under any ambient light (P < 0.001; 0.021, respectively). Eye tiredness and soreness also increased (P = 0.004; 0.024, respectively). After sleep under 5 lux light, only nasal conjunctival hyperemia increased significantly (P = 0.008). After sleep under 10 lux light, nasal and temporal conjunctival hyperemia, eye tiredness, soreness, difficulty in focusing, and ocular discomfort increased significantly (P < 0.05).

CONCLUSION

Nocturnal ambient light exposure increases ocular fatigue. Avoiding ambient light during sleep could be recommended to prevent ocular fatigue.

Effects of a high level of illumination before sleep at night on chorioretinal thickness and ocular biometry

The choroid is affected by many factors. One of the factors, change in illumination has been suggested to influence choroidal thickness. However, the effects of bright light before sleep at night on the human eye are not well established. The purpose of this study was to investigate the effects of a high level of illumination in the evening on ocular measurements. Twenty-seven men with myopia spent seven consecutive nights in the sleep laboratory. During the first two nights, subjects were exposed to light at 150 lux between 20:00 and midnight. Then, for five consecutive nights, they were exposed to ambient light at 1000 lux between 20:00 and midnight. Ocular parameters and their diurnal variations were compared between the two periods and the effects of a high level of illumination were analyzed. After subjects were exposed to 1000 lux of illumination, axial length increased with borderline significance (p = 0.064). Macular volume and retinal thickness did not change. However, subfoveal choroidal thickness after exposure to 1000 lux of illumination (245.37 ± 52.84 μm) was significantly lower than that after 150 lux of illumination (268.00 ± 57.10 μm), (p < 0.001). Significant diurnal variations were found in mean keratometry (p = 0.039), intraocular pressure (IOP, p = 0.003), ocular perfusion pressure (OPP, p < 0.0001), macular volume (p = 0.019), and subfoveal choroidal thickness (p < 0.0001). A high level of illumination had significant effects on only IOP and OPP (p = 0.027 and 0.017, respectively). Bright light exposure before sleep at an intensity as high as 1000 lux reduced subfoveal choroidal thickness in healthy young men. In conclusion, diurnal variation in choroidal thickness can be affected by bright light exposure before sleep.

Esotropia Surgery Considering the Angle under General Anesthesia

PURPOSE

To compare the amount of esotropia corrected by surgery under general anesthesia and in a conscious state in esotropia surgery.

METHODS

The charts of 42 patients who underwent surgery under general anesthesia for correction of esotropia were reviewed. Angle of deviation was measured by the alternate prism cover test in awakened state one day before and after surgery. Under general anesthesia, angle of deviation was measured by Hirschberg or Krimsky test in 5 prism diopters (PD) scale 30 minutes after induction and at the end of the surgery. The amount of the angle of esodeviation corrected by surgery measured in awakened state (A-correction) and under general anesthesia (G-correction) was compared and analyzed to identify significant differences.

RESULTS

The median age was 4.0 years and the median preoperative esodeviation angle was 30.0 PD. The median amount of G-correction of 30.0 PD was significantly different compared with that of A-correction at postoperative day one (p=0.003). However, differences between A-correction and G-correction were not evident at postoperative one week, one month, and final follow-up examination (p= 0.191, 0.215, and 0.396, respectively).

CONCLUSIONS

Esotropia in A-correction was comparable to that in G-correction only at postoperative day one. These results suggest that it is desirable to perform esotropia surgery according to the initial surgical plan of awakened state regardless of the divergence of eye position. When in doubt, it could be useful to confirm whether the actual amount of surgical correction under general anesthesia is consistent with the plan and modifying the surgical dose nomogram.

Demographic features of idiopathic macular telangiectasia in Korean patients

Purpose

To investigate the clinical and demographic features of idiopathic macular telangiectasia (MacTel) in Korean patients since the introduction of spectral domain optical coherence tomography (SD-OCT).

Methods

We reviewed medical records of patients who were diagnosed with MacTel from 2009 to 2013. All patients underwent fluorescein angiography and SD-OCT and were classified as type 1 or type 2 according to the classification system proposed by Yannuzzi.

Results

Over a period of 5 years, 4 (18.2%) patients were diagnosed with type 1 MacTel and 18 (81.8%) patients were diagnosed with type 2 MacTel. All patients with type1 MacTel were male, and their mean age was 51 ± 8.6 years. Among patients with type 2 MacTel, 3 (16.7%) were male, 15 (83.3%) were female, and the mean age was 60 ± 13.6 years. Whereas all type 1 MacTel patients had either metamorphopsia or mild scotoma, of the 18 patients with type 2 MacTel, only 4 (22.2%) had those symptoms, 10 (55.6%) complained of only mild visual impairment, and the other 4 (22.2%) had no symptoms. Intraretinal cystoid spaces were observed in 26 (72.2%) of 36 eyes with type 2 MacTel by SD-OCT. These cystoid spaces had irregular boundaries and did not correspond to angiographic leakages.

Conclusions

Type 2 MacTel was most common in the present study. The wider availability of SD-OCT may have contributed to the diagnosis of type 2 MacTel. Type 2 MacTel may be more prevalent than type 1 in Koreans, which corresponds to the results of Western countries.

Stability of Y-splitting procedure combined with hang-back recession of the rectus muscle in rabbit eyes

BACKGROUND

The Y-splitting procedure has been used both to treat up-shoots and down-shoots in Duane syndrome, and as a substitute for posterior fixation suture. The Y-split is often performed in conjunction with a hang-back recession when a large amount of recession or an adjustable suture is necessary. Herein, we evaluated the stability of Y-splitting hang-back recession in the rectus muscle.

METHODS

Under general anesthesia, a 5-mm hang-back recession of the superior rectus muscle (SR) with Y-splitting was performed in ten eyes from ten rabbits (hang-back group). A conventional recession was performed in the SR of the fellow eye (control group). Six weeks after the procedure, the distance between the original insertion and the recessed SR (recession amount) and the width between the nasal and temporal halves of the SR were measured. These values were compared to the measurements taken at the time of surgery.

RESULTS

The hang-back group had a significantly larger forward displacement than the control group (P < 0.001 for both the nasal and temporal halves). The width change between the nasal and temporal halves was also significantly larger in the hang-back group (4.94 ± 1.32 mm) than in the control group (1.14 ± 0.60 mm, P < 0.001). Additionally, the Y-configuration appeared to be more collapsed in the hang-back group than in the control group.

CONCLUSION

Y-splitting of the rectus muscle may be unstable when it is combined with a hang-back recession. Surgeons should consider this possibility when performing Y-splitting procedures.