title: Relationship between functional and structural retinal changes in myopic eyes.
abstract: BACKGROUND
  The aim of this study was to investigate the retinal structure in different grades of myopia and correlate it with the functional changes detected with multifocal electroretinogram (mf-ERG) and try to show the most important determining factors.
  
  
  METHODS
  The study included 80 participants divided into four groups according to their spherical equivalent refractive error, namely, emmetropia (within ± 0.50 D), mild myopia group (greater than -0.50 to -3.00 D), moderate myopia group (more than -3.00 to -6.00 D) and high myopia group (greater than -6.00 D). Full ophthalmologic examination was performed for all participants, including visual acuity (VA), slitlamp examination, Goldmann applanation tonometry, indirect ophthalmoscopy, axial length (AL) measurement, retinal nerve fibre layer thickness assessment and mf-ERG stimulation.
  
  
  RESULTS
  Axial length was significantly higher in myopes than emmetropes; also it was higher the greater the degree of myopia. There was a reduction in the amplitude and prolongation of implicit times of mf-ERG in myopia. Also P1 implicit time of the mf-ERG response was prolonged the greater the degree of myopia. The retinal nerve fibre layer was significantly thinner in myopic groups than the emmetropic group. The thinning of the retinal nerve fibre layer increased the more the degree of myopia. Multiple regression analysis of myopic patients showed that AL is the most important determinant of most of the mf-ERG five-rings retinal response density (RRD), mf-ERG four-quadrant (Q) RRD, most of the five-rings P1 amplitude and all five-rings latencies. The most important determinant factors of mean Q RRD were VA, AL and retinal nerve fibre layer thickness.
  
  
  CONCLUSIONS
  The retina of the myope is subject to both structural and functional alterations compared to that of the emmetrope. Significant correlations exist between the functional and structural changes and can be explained on bases of longer AL and increasing myopic refraction.
authors.affiliation: Department of Ophthalmology, Ain Shams University, Cairo, Egypt.
authors.forename: Zafer Fahiem
authors.initials: ZF
authors.lastname: Ismael
authors.affiliation: Department of Ophthalmology, Ain Shams University, Cairo, Egypt.
authors.forename: Amany Abd El-Fattah
authors.initials: AAE
authors.lastname: El-Shazly
authors.affiliation: Department of Ophthalmology, Ain Shams University, Cairo, Egypt.
authors.forename: Yousra Ahmed
authors.initials: YA
authors.lastname: Farweez
authors.affiliation: Department of Ophthalmology, Ain Shams University, Cairo, Egypt.
authors.forename: Marwa Mahmoud Mohammed
authors.initials: MMM
authors.lastname: Osman
mesh_terms: D000293:Adolescent; D000328:Adult; D058452:Axial Length, Eye / Q000503:physiopathology*; D004596:Electroretinography; D058453:Emmetropia / Q000502:physiology*; D005260:Female; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D008297:Male; D009216:Myopia / Q000145:classification / Q000503:physiopathology*; D009412:Nerve Fibers / Q000473:pathology; D012160:Retina / Q000503:physiopathology*; D012165:Retinal Ganglion Cells / Q000473:pathology; D014065:Tonometry, Ocular; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult
keywords: axial length; degrees of myopia; mean Q retinal response density; multifocal ERG
  ; retinal nerve fibre layer; retinal response density