Diurnal variations in solar ultraviolet radiation at typical anatomical sites.

OBJECTIVE: Solar ultraviolet (UV) radiation is an important environmental factor that affects human health. The understanding of diurnal variations of UV radiation at anatomical sites may be helpful in developing ways to protect humans from the harmful effects of UV radiation. METHODS: In order to characterize the diurnal variations, the UV exposure values were measured at 30 min intervals by using Solar-UV Sensors and a rotating manikin in Shenyang city of China (41 degrees 51'N, 123 degrees 27'E). Measurement data for four representative days (in each of the four seasons respectively) were analyzed. RESULTS: The diurnal variations in solar UV radiation at the shoulder, the forehead and the chest were similar to those associated with a horizontal control measurement. However, the diurnal variations at the eye and the cheek exhibited bimodal distributions with two peaks in spring, summer and autumn, and a unimodal distribution in winter. The UV exposure peaks at the eye and the cheek were measured at solar elevation angles (SEA) of about 30 degrees and 40 degrees , respectively. CONCLUSION: The protection of some anatomical sites such as the eye from high UV exposure should not be focused solely on the periods before and after noon, especially in the places and seasons with high SEA.

Effects of UVA on TNF-alpha, IL-1beta, and IL-10 expression levels in human keratinocytes and intervention studies with an antioxidant and a JNK inhibitor.

OBJECTIVE: To understand the expressions and transduction pathways of cytokines in ultraviolet (UV)A-irradiated keratinocytes. METHODS: We cultured human keratinocytes of the HaCaT cell line and investigated both mRNA and protein expressions of cytokines in cells that were not irradiated or were exposed to 2.4 J/cm(2) UVA, with or without an antioxidant (beta-carotene) or a c-Jun N-terminal kinase (JNK) inhibitor (SP600125). RESULTS: We demonstrated that the expression levels of tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta were up-regulated in irradiated cells. IL-10 was not detected in non-irradiated cells, but was observed in irradiated cells. JNK was activated in irradiated cells and this could be antagonized by beta-carotene. The UVA-induced up-regulation of these cytokines was also antagonized by beta-carotene. SP600125 inhibited the UVA-induced increase in the expression of TNF-alpha mRNA and protein and in the expression of IL-1beta mRNA. CONCLUSIONS: The results suggest that oxidative stress may be an early intermediate effect in JNK-dependent UVA induction of cytokine expression in human keratinocytes in vitro.

[Study of binocular function in early stage after implantation of multifocal intraocular lens].

OBJECTIVE: To evaluate binocular function in the early stage after implantation of multifocal intraocular lens. METHODS: Three weeks postoperatively, simultaneous perception, fusion, near and far-distance stereoacuity, visual acuity and visual symptoms were observed in 31 cases (46 eyes) with multifocal intraocular lens implantation (MIOL) [MIOL group, in which 16 cases with unilateral implantation (Ms) and 15 cases with bilateral implantation (Md)] and 32 cases (47 eyes) with single-focal intraocular lens implantation (SIOL) [SIOL group, in which 17 cases with unilateral implantation (Ss) and 15 cases with bilateral implantation (Sd)]. RESULTS: All patients obtained simultaneous perception and fusion sense, there was no significantly statistical difference between these two group (P > 0.05). Foveal far-distance stereoacuity was established in 38.7% cases among MIOL group (12/31) and 40.6% in SIOL group (13/32), with no statistically significant difference between these two groups (P > 0.05). Foveal near-distance stereoacuity was established in 41.9% MIOL cases (13/31) and in 15.6% SIOL group (5/32), the difference was statistically significant (P < 0.05). Foveal near and far-distance stereoacuity of either Ms and Md or Ss and Sd revealed no significantly statistical difference (P > 0.05). Two patients (6.5%) with MIOL in only one eye complained glare at night, others were satisfied. The stereopsis visual performance such as the quality of vision during eating, up-and-down stairs was improved in MIOL group [80.6% (25/31)] and in SIOL group [56.2% (18/32)], the difference was statistically significant (P < 0.05). CONCLUSIONS: There is a complete recovery of binocular vision in the early post-operative stage of MIOL implantation as compared with the normal value of aged people. Foveal near and far-distance stereoacuity after bilateral and unilateral implantation of either MIOL or SIOL revealed no statistically significant difference. Foveal near-distance stereopsis acuity of MIOL group was improved more quickly than that of SIOL group. MIOL has distinct advantage in providing whole-distance visual acuity and stereoacuity.

[Hypertonic saline-assisted laser-assisted subepithelial keratectomy for the correction of moderate and low myopia].

OBJECTIVE: To evaluate the effectiveness of hypertonic saline (5% sodium chloride) in execution of epithelial flap in laser-assisted subepithelial keratomileusis (HS-LASEK) for treatment of moderate and low myopia. METHODS: 48 patients (96 eyes) with moderate and low myopia were divided into 2 groups. In Group A (A-LASEK, 22 patients 44 eyes), 20% alcohol was used to create the epithelial flap; in Group B (HS-LASEK, 26 patients 52 eyes), 5% sodium chloride was used to create the epithelial flap. Postoperative visual acuity, refraction power, time of epithelial healing, and haze were recorded. The patients were followed-up for 6 months. RESULTS: The mean time of epithelial healing was (4.52 +/- 0.21) days in A-LASEK eyes, while (3.84 +/- 0.39) days in HS-LASEK eyes, the difference of epithelial healing time between the two groups was statistically significant. Visual acuity in all patients were improved by the surgery, 3 days after operation, visual acuity reached 0.8 or better in 27.3% (12/44) of A-LASEK eyes and 48.1% (25/52) of HS-LASEK eyes, the difference between the two groups was statistically significant (P < 0.05). Two weeks after operation corneal haze was found in 13 eyes (29.5%) of A-LASEK group and 15 eyes (28.8%) of HS-LASEK group, but the grade haze was below 0.5 and had no effect on visual acuity, after 3 months, haze was noted in 10% of eyes in each groups, the difference of corneal haze between the two groups was no statistically significant (P > 0.05). One day after operation 12 eyes (27.3%) of A-LASEK and 6 eyes (11.5%) of HS-LASEK had obvious pain, the difference between the two groups was statistically significant (P < 0.05). CONCLUSION: HS-LASEK is a safe surgery for the correction of moderate and low myopia as A-LASEK, and have a better curative effect than A-LASEK.

[LASEK for the correction of residual myopia and astigmatism after LASIK].

OBJECTIVE: To determine the visual and refractive outcome of LASEK for the correction of residual myopia and astigmatism after laser in situ keratomileusis (LASIK). METHODS: In this prospective study of noncomparative case series, LASEK was performed with minimum of 6 months in 66 eyes (34 patients) that developed myopic regression after LASIK. Mean follow-up was 13.2 months after laser ablation (12 to 18 months). The postoperative symptom, epithelial flap, wavefront aberration, and haze formation were investigated. RESULTS: Postoperative results revealed a reduction in the residual myopia and astigmatism. Higher order aberration was increased postoperatively. No eye lost best corrected Snellen visual acuity. No intraoperative or postoperative complications occurred. CONCLUSIONS: LASEK performed in eyes with myopic regression after LASIK result in an improvement in uncorrected visual acuity.

[Effects of flashing light on ocular growth and development of myopia in pigmented guinea pigs].

OBJECTIVE: To investigate the effects of flashing light exposure on ocular growth and development of myopia in guinea pigs. METHODS: Thirty 4-week-old pigmented guinea pigs were randomly divided into three groups. Animals in group I were reared with the flashing light continuously and lasted for 6 weeks. The flashing frequency was 15 times per minutes and every flash includes 2 seconds light on and 2 seconds dark. Animals in group II and III were reared with normal light on, and the illumination cycle was 12 hours light/12 hours dark in group II and 24 hours light in group III. After 6 weeks, the effects of flashing light on eye development were assessed by cycloplegic retinoscopy, a-scan ultrasonography and eye weight. The histopathology changes of sclera, choroids and retina in posterior pore of the eye were examined using light microscope and transmission electron microscope. RESULTS: At the end of the treatment period, guinea pigs reared in flashing light exhibited -7.00 D myopia, eye axial elongated 0.56 microm, and the weight increased 68 mg. The histopathology examination showed that the posterior sclera fibroblast become more active, the cell number increased, and the place between fibers became larger, the posterior choroids became thinned, and the outer membrane of photoreceptor cells became shorter and irregular, when compared with the control groups. CONCLUSION: Flashing light can promote ocular growth and induce myopia in pigmented guinea pigs.

[Effect of time limited form deprivation on the development of myopia in guinea pigs].

OBJECTIVE: To investigate the effect of time limited form deprivation on the development of form-deprived-myopia (FDM) in guinea pigs. METHODS: Four-week-old guinea pigs (n = 20) were randomly divided into four groups. Group I was used as normal control without any treatment. In group II-IV, unilateral form deprivation was produced with eye patch for 4 weeks. In group II, eye occlusion was fitted continuously. In group III and IV, occlusion was removed each day for 1 or 4 hours. Refractive development was monitored by retinoscopy and A-scan ultrasonography before and after experiment. RESULTS: After 4 weeks, varied degree of axial myopia was developed in the groups II and III with eye occlusion. Continuous form deprivation produced -5.49 D of relative myopia and the fellow eyes produced +0.76 D of relative hyperopia. One hour of unrestricted vision was sufficient to reduce the degree of FDM by about 50%. The eyes allowed 4 hours of unrestricted vision did not result in myopia. CONCLUSION: Long periods of form deprivation can be counterbalanced by quite short periods of unrestricted vision.

[The recovery of binocular vision in the early post-operative stage of senile cataract patient].

OBJECTIVE: To study the recovery of binocular vision and the risk factors that affect the recovery in the early post-operative stage of senile cataract patients. METHODS: Patients undergone extracapsular cataract extraction with intraocular lens implantation (ECCE group) or cataract phacoemulsification with intraocular lens implantation (PHACO group) were examined for their corrected visual acuity, refractive power, simultaneous perception, fusion, near and far-distance stereoacuity. RESULTS: Before operation, the visual acuity was worse in the ECCE group than that in the PHACO group (chi(2) = 9.769, P < 0.05); After operation, the visual acuity between ECCE group and PHACO group was not statistically significant (chi(2) = 0.52 for operated eyes, P > 0.05, chi(2) = 3.52 for non-operated eyes, P > 0.05). The cylinder anisometropia in ECCE group was worse than the PHACO group (chi(2) = 12.496, P < 0.01). All patients obtained simultaneous perception and fusion sense. There was more or less far-distance stereoacuity 83.3% in ECCE group and 94.7% in PHACO group, which was no statistical significant (chi(2) = 1.456, P > 0.05). Foveal near stereoacuity was established in ECCE group (2.8%) and in PHACO group (21.1%), which were statistically significant (chi(2) = 5.029, P < 0.05). CONCLUSIONS: There is incomplete recovery of binocular vision in the early post-operative stage of senile cataract patients. The vision depression, especially monocular depression before surgery and the anisometropia after operation may affect the recovery of binocular vision.

[Comparison of corneal wound healing of photorefractive keratectomy and laser in situ keratomileusis in rabbits].

OBJECTIVE: To compare effects of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) on the cornea and corneal wound healing and to investigate the possible mechanism of corneal haze and myopic regression histopathologically. METHODS: Twenty-four New Zealand white rabbits were allocated randomly to correct -4.00 and -8.00 diopters and were operated with PRK on right eyes and LASIK on left eyes. At 10 days and 1, 3, and 6 months, corneal haze was observed, refraction was evaluated, and 3 rabbits were randomly selected for each time point to be enucleated, and corneas to be bisected. One half of each cornea was evaluated using transmission electron microscopy, and the other half was evaluated using either light microscopy or immunohistochemical staining for collagen type III, IV, fibronectin (FN) and transforming growth factor-beta(1) (TGF-beta(1)). RESULTS: Different degrees of corneal haze and myopic regression were observed after PRK: the higher the desired myopic correction, the heavier the haze. Corneal wound healing response was greater and lasted longer after PRK than after LASIK. Various pathological findings such as epithelial hyperplasia, basal membrane reforming and extracellular matrix deposits were found in the ablation zone and repair mechanisms were still active at 6 months after PRK. Whereas after LASIK, the interface between the flap and stromal bed was transparent except for growing epithelial plugs and lightly proliferating stroma coinciding with the flap margins. After both PRK and LASIK, all corneal cell types were consistently positive for TGF-beta(1) antibody during the corneal wound healing time. TGF-beta(1) antibody positivity decreased as the wound healing approached completion. The histopathological changes of corneal haze and myopic regression are as follows: epithelial hyperplasia, basal membrane immaturity, anterior stromal keratocyte increase and activity, new collagen III production and irregular arrangement thereof, and FN deposition in the extracellular matrix under the epithelium. CONCLUSIONS: Compared with PRK, LASIK ensures refractive stability with quick wound healing and minimal tissue proliferation resulting in a more promising corneal refractive surgery to correct myopia, especially more severe cases of myopia. The corneal wound healing especially the stromal healing is the key to the cause of haze and myopic regression. TGF-beta(1) may be involved in scar formation during wound healing by stimulating expression of collagen III and FN and is believed to be an important regulating factor.