Abnormal Retinal Nerve Fiber Layer Thickness And Macula Lutea In Patients With Alzheimer’s Disease And Mild Cognitive Impairment

Objective:Alzheimer’s disease is a kind of degenerative disease that clinicallycharacterized by progressive cognitive impairment, particular episodic memorydeficit,and decline in learning and executive functions. In the late stage of AD,In thelate stage of AD,the diagnosis is not difficult as a result of apparent symptoms,and notcrucial either since the treatment effect is so limited.which means not only suffering forthe patients but great burden for both their families and our society.Nevertheless,early diagnosis is of great importance.Opticalcoherence tomography(OCT) which is a cheap and non-invasive instrument has the potential to be a newdiagnostic tool for AD.Our study aim to investigate the retinal nerve fiber layer(RNFL)and macula lutea of Alzheimer’s disease(AD) and mild cognitive impairment(MCI)patients by OCT so as to clarify if there are abnormalities and if the abnormalities areconsistent with the severity of dementia.Methods:case-control study.73subjects were included.AD group:25(M/F:11/14);MCI group:26(M/F:16/10);control group:20(M/F:14/6).The patients met criteria forprobable AD set by the National Institute of Neurological and CommunicativeDisorders and Stroke-Alzheimer’s Disease(NINCDS-ADRDA) and Related DisordersAssociation and the Diagnostic and Statistical Manual of Mental Disorders fourthedition (DSM IV) criteria.The MCI patients fulfilled the Petersen criteria.It should benoted that all the AD and MCI patients were newly diagnosed and never had receivedany treatment in case of the influence of medicines.All the subjects underwent completeneurological and physical examination,ophthalmic examination,laboratory examination,neuro-imaging evaluations,and psychometric testings.Finally,all the subjects receivedoptical coherence tomography(OCT) examination to observe the RNFL and maculalutea.Optic Disc Cube200x200scan mode was chosen to derive the ONH parameters, including the horizontal and vertical cup-to-disc ratios,as well as peripapillary RNFLthickness by a non-consecutive360°circular scan with a diameter of3.46mm centeredon the optic disc. When all procedures above finished,256A-scan samples wereextracted by its own software to form the mapping of the RNFL thickness data by thestyles of quadrant-by-quadrant and clock-hour.Macular Cube512x128mode was usedto get data of Cube average thickness,and cube volume.Statistical Package for the SocialSciences (SPSS) was employed to do the statistic analysis,and a p <0.05wasconsidered to be significant.Results:The average age of AD group was74.72,MCI group was73.46,and71.95of control group.There was no statistically significant difference in age and genderbetween groups which were showed in table1.AD group had a lower MMSE score thanMCI group.Data of48eyes from AD group,50eyes from MCI group and39eyes fromcontrol group was credible.The threshold of signal strength was set to be>6.The averageRNFL thickness:the AD group:86.16±9.96μm,the MCI group:93.74±11.15μm,thecontrol group:97.62±6.20μm.The RNFL thickness of AD patients showed a significantreduction in all quadrants and positions as well as the average thickness.The thinningwas statistically significant except in12:00,the nasal quadrant,and three positions whichbelonged to it(2:00,3:00,4:00).The RNFL thickness of AD patients was thinner than thatof MCI patients,and several locations were selectively involved more severely and thesignificance reached to a p<0.05:the mean thickness,inferior quadrant,5:00,6:00,10:00and11:00.When compared with age-matched subjects,MCI patient showed apronounced change which mainly located in the superior quadrant,temporal quadrantand three other positions belonging to them(8:00,10:00,11:00).Only the reductionbetween AD group and control group was statistically significant when we evaluated themacula,and the decreasing of macula in MCI group was not statisticallysignificant.There was no correlation neither between MMSE scores and average RNFLthickness(p＞0.05) nor that between total macular volume and MMSE scores(p＞0.05).Conclusion:there was degeneration of retina in AD and MCI patients which wasmanifested by an reduction of the mean RNFL thickness or selectively decreasing ofdifferent locations.Besides,the AD group had a thinner macular volume.There was nocorrelation neither between MMSE scores and average RNFL thickness nor thatbetween total macular volume and MMSE scores,and that is to say there was nocorrelation between these changes and the severity of dementia.OCT has the chance andpotential to be the early diagnostic and antidiastole method of AD,and it may help reduce the great social pressure that comes along with AD.