The theory of critical flicker fusion frequency and its application in cataracts

Background:Due to media opacity,it is usually difficult to accurately evaluate the postoperative visual acuity in cataracts patients.As a small and portable tool,the critical flicker fusion frequency(CFF)device reflects the temporal resolution of visual function and has been widely used in clinical research.However,poor understanding of the technique and equipment limitations have restricted its clinical application in China.Main text:There was a decrease in the CFF value in various ophthalmic diseases,indicating that the CFF is sensitive to detect visual functional changes.A number of studies have shown that the CFF test can accurately distinguish patients with simple cataracts from those with cataracts combined with fundus disease,and,as a visual test,it can more accurately predict postoperative visual acuity without being affected by media opacity.This study comprehensive reviews the basic principles of CFF and its application in ophthalmology,especially in cataracts.Conclusions:As one of the tools for dynamic visual function detection,the CFF test could help doctors to assess the possible presence of fundus disease in cataracts patients,especially in eyes with dense cataracts,and more precisely provide a reasonable visual prognosis than other available visual tests.

A GAN-based deep enhancer for quality enhancement of retinal images photographed by a handheld fundus camera

Objective:Due to limited imaging conditions,the quality of fundus images is often unsatisfactory,especially for images photographed by handheld fundus cameras.Here,we have developed an automated method based on combining two mirror-symmetric generative adversarial networks(GANs)for image enhancement.Methods:A total of 1047 retinal images were included.The raw images were enhanced by a GAN-based deep enhancer and another methods based on luminosity and contrast adjustment.All raw images and enhanced images were anonymously assessed and classified into 6 levels of quality classification by three experienced ophthalmologists.The quality classification and quality change of images were compared.In addition,imagedetailed reading results for the number of dubiously pathological fundi were also compared.Results:After GAN enhancement,42.9% of images increased their quality,37.5%remained stable,and 19.6%decreased.After excluding the images at the highest level(level 0)before enhancement,a large number(75.6%)of images showed an increase in quality classification,and only a minority(9.3%)showed a decrease.The GANenhanced method was superior for quality improvement over a luminosity and contrast adjustment method(P<0.001).In terms of image reading results,the consistency rate fluctuated from 86.6%to 95.6%,and for the specific disease subtypes,both discrepancy number and discrepancy rate were less than 15 and 15%,for two ophthalmologists.Conclusions:Learning the style of high-quality retinal images based on the proposed deep enhancer may be an effective way to improve the quality of retinal images photographed by handheld fundus cameras.

The clinical application of critical flicker fusion frequency in demyelinating optic neuritis

Purpose:To investigate the application of critical flicker fusion frequency(CFF)in demyelinating optic neuritis(DON).Methods:A cross-sectional study.A total of 127 eyes in 69 DON patients and 63 eyes in 33 healthy control(HC)groups were included between January 2021 to September 2021 from Department of Ophthalmology,PLA General Hospital.Patients underwent best-corrected visual acuity(BCVA),visual field,optical coherence tomography(OCT),flash visual evoked potential(F-VEP),and CFF examinations.The affected eyes were divided into aquaporins 4(AQP4-),myelin oligodendrocyte glycoprotein(MOG-),and double negative DON according to serum antibody;mild,moderate,severe degree visual impairment according to BCVA
0.5,0.1-0.5,<0.1;and 4 groups:<1,1~<3,3~<6 and>6 months according to time interval from onset to CFF examination.One-way ANOVA was used to perform above subgroup analysis.The correlations between CFF and F-VEP peak time,peak value,BCVA and mean visual filed defect(MD)were analyzed in order via Pearson correlation analysis.Results:he trichromatic values of red,green,and yellow in DON affected eyes were 21.83±9.03,23.66±10.21,24.09±10.77 Hz,respectively,which was significantly reduced compared with the HC group(t=-14.82,-14.22,-14.00;P<0.001).The subgroup analysis showed no significant difference between different antibody subtypes(P=0.914<0.848<0.604),whereas,a significant decrease of CFF trichromatic value was found in severe visual acuity impairment group(P<0.001).There was a significant difference in CFF-trichromatic values at different time points(P<0.001),to be specific,CFF fluctuated under 20Hz within 3 months after onset and tended to be stable around 24-28Hz.Correlation analysis showed that the peak time of F-VEP(r=-0.486,-0.515,-0.526;P<0.001),BVCA(r=-0.640,-0.659,-0.642;P<0.001),were negatively correlated with CFF trichromatic values,MD and CFF were positively correlated(r=0.486,0.453,0.476;P=0.003,0.006,0.004).Conclusions:A significant decrease of CFF value was found in DON-affected eyes,and it has a good correlation with BCVA,MD and latency of F-VEP,and can better reflect the impairment of visual function.

Clinical characteristics of radiation-induced optic neuropathy:A single-center retrospective study

Purpose:To observe the clinical and imaging characteristics of radiation-induced optic neuropathy(RION).Methods:We retrospectively reviewed the clinical data of 43 patients(69 eyes)who were diagnosed with RION at the Chinese PLA General Hospital from 2010 to 2021.Results:The latency from radiotherapy to onset of visual loss ranged from 1 to 132(36.33±30.48)months.Optic disc pallor and optic disc edema were found in 27.0%(10/37)and 8.1%(3/37)of the eyes,respectively,within 2 months.After treatment,the best corrected visual acuity(BCVA)was restored in 24.6%(17/69)of the eyes and the final BCVA improved in 13.0%(9/69)of the eyes.An 82.5%(33/40)of the eyes with magnetic resonance imaging(MRI)showed enhancement of the affected optic nerve,mostly(69.7%)in the intracranial segment,and 36.4%(12/33)of the eyes with expansion and T2-high signals also showed enhancement of the affected optic nerve.The superior retinal nerve fiber layer(RNFL)and the outer circle superior quadrant(OS)of the inner limiting membrane to retinal pigment epithelium(ILM-RPE)layer thinned significantly during the first month.The center of the ILM-RPE layer thickened significantly during the first two months and the inner circle temporal quadrant(IT)of the ILM-RPE layer thickened significantly from the third to sixth month.The RNFL thinned significantly after 6 months except for the temporal quadrant,and the average inner circle superior quadrant(IS)and outer circle of the ILM-RPE layer thinned significantly after 6 months.There was no significant difference between hyperbaric oxygen therapy(HBOT)and high-dose intravenous methylprednisolone(IVMP)therapy in improving BCVA recovery or final BCVA(P>0.05).Conclusions:The structural damage of the RNFL and ILM-RPE layer occurred during the first month,the RNFL showed progressive thinning during the follow-up period,while the ILM-RPE layer showed thinning during the first month,thickening from the third to sixth month,and thinning after 6 months.There was a discrete region of enhancement of the optic nerve,often with expansion and high-T2 signals on MRI.HBOT and high-dose IVMP therapy were hardly effective for treating RION in the non-acute stage.

A comparative study of alteration in retinal layer segmentation alteration by SD-OCT in neuromyelitis optica spectrum disorders: A systematic review and meta-analysis

Background:To evaluate the feature of different retinal layer segmentation in neuromyelitis optica spectrum disorders(NMOSD)with spectral-domain optical coherence tomography(SD-OCT)and to compare it with that in multiple sclerosis(MS),healthy controls(HC),and idiopathic optic neuritis(ION).Methods:We retrieved four electronic databases,including Pubmed,Embase,Cochrane Library,and Web of Science from inception to September 1st,2021.A meta-analysis was performed to compare different retinal layer segmentation thicknesses between patients with or without a history of optic neuritis(ON)in NMOSD and the control group,including patients with MS,HC,and ION.Results:Forty-two studies were included and the interval between the last ON onset and examination was greater than 3 months.Compared with that in HC eyes,the loss of retinal nerve fiber layer(RNFL)and macular ganglion cell and inner plexiform layer(GC-IPL)was serious in NMOSD eye especially after ON.Moreover,compared with that in ION eyes or MS-related-ON eyes,the injury to the peripapillary retinal nerve fiber layer(pRNFL)was severe in NMOSD-related-ON eyes.In addition,the correlation coefficient between pRNFL and prognostic visual acuity was 0.43.However,the one-arm study revealed the inner nuclear layer(INL)was thickened in NMOSDrelated-ON eyes compared with HC eyes.Conclusions:Inclusion of the RNFL and macular GC-IPL is recommended for monitoring disease progression and attention should be paid to changes in the INL.

Differences in the involved sites among different types of demyelinating optic neuritis in traditional MRI examination:A systematic review and meta-analysis

Background:Magnetic resonance imaging(MRI)plays a significant role in assessing optic neuropathy and providing more detailed information about the lesion of the visual pathway to help differentiate optic neuritis from other visual disorders.This study aims to systematically review the literature and verify if there is a real difference in lesion location among different demyelinating optic neuritis(DON)subtypes.Methods:A systematic search was conducted including 8 electronic databases and related resources from the establishment of the database to August 25th,2020.We classified DON into 5 subtypes and divided the visual pathways into five segments mainly comparing the differences in the involved visual pathway sites of different subtypes.Results:Fifty-five studies were included in the analysis,and the abnormal rate was as high as 92%during the acute phase(within 4 weeks of symptom onset).With respect to lesion location,the orbital segment of the optic nerve was the most frequently involved(87%),whereas optic tract involvement was very rare.Involvement of the orbital segment was more common in myelin oligodendrocyte glycoprotein antibody-related optic neuritis(MOGON)(78%)and chronic relapsing inflammatory optic neuropathy(CRION)(81%),while the lesion was found to be located more posteriorly in neuromyelitis optica spectrum disorder-related optic neuritis(NMOSD-ON).With respect to lesion length,approximately 77%of MOG-ON patients had lesions involving more than half of the optic nerve length.Conclusions:MRI examination is recommended for DON patients in the acute phase.In MOG-ON,anterior involvement is more common and the involved length is mostly more than 1/2 of the optic nerve length,whereas posterior involvement,intracranial segment,optic chiasm,or optic tract,is more common in NMOSD-ON.