Examination of Afferent Visual System: Visual Acuity and Field
이익성
순천향대학교부천병원 신경과
Examination of Afferent Visual System : Visual Acuity and Field
순천향대학교부천병원 신경과 이익성
Visual Acuity
Visual Acuity
Minimum Angle of Resolution (MAR) Visual acuity = 1/MAR (minutes)
두 점이 떨어져 있다고 인식하는 최소 공간해상도 MAR 이 1분이면 시력을 1.0 으로 표시
Minimal Angle of Resolution
1.5mm 1 minute (1/60 degree) 5 m
측정방법
• 한눈을 가리고 반대편 눈의 시력을 측정(잘 가려졌는지 확인)
• Latent nystagmus: +6.00디옵터 렌즈
• Congenital nystagmus: null point에서 측정
• 0.1 도 못 읽을 경우 앞으로 천천히 걸어오게 하여 시표가 보이
기 시작한 거리에 반비례하여 시력을 표시(5미터 시력표의
0.1 시표를 1미터에서 볼 경우 0.1 X (1/5) = 0.02)
• FC (finger count)
• HM (hand movement)
• LP (light perception)
• NLP (no light perception)
Visual Acuity Notation System
분수(feet) 분수(meter) 소수 logMAR
20/200 6/60 0.10 1.00
20/160 6/48 0.125 0.90
20/125 6/38 0.16 0.80
20/100 6/30 0.20 0.70
20/80 6/24 0.25 0.60
20/63 6/19 0.32 0.50
20/50 6/15 0.40 0.40
20/40 6/12 0.50 0.30
20/32 6/9.5 0.63 0.20
20/25 6/7.5 0.80 0.10
20/20 6/6 1.00 0.00
20/16 6/4.8 1.25 -0.10
20/12.5 6/3.8 1.60 -0.20
20/10 6/3 2.00 -0.30
한천석표준시력표(원거리) Rosenbaum Pocket Vision Screener (36cm)
logMAR분수 소수
ETDRS (Early Treatment of Diabetic Retinopathy Study) 시력표
“Peek Acuity smartphone test is capable of accurate and repeatable acuity measurements consistent with published data on the test-retest
Results of the 8 Pairwise Comparisons of the Right Eye Sh owing Bland-Altman and Pearson Correlation Analysis
“We did not identify a Snellen visual acuity app at the time of study, which could predict a patients standard Snellen visual acuity within one line.”
Visual Field
Normal Visual Field
Nasal – 60 degree Temporal – 90~110 degree Superior – 60 degree Inferior – 75 degree
Techniques for Testing Visual Fields
• Confrontation testing
• Amsler grid
• Perimetry
• (Manual) Kinetic perimetry (Goldmann)
• (Automated) Static perimetry (Humphrey)
Confrontation Testing
• Advantages
• simplicity, flexibility, speed of administration, and ability to be performed in any setting, including at the bedside
• Disadvantages
• lack of standardization, the qualitative nature of the results, and the limited ability to detect subtle deficits and monitor progression or remission of visual loss
• Because it is quick and easy to perform, confrontation visual field should be performed on all patients, regardless of their visual complaints.
Amsler Grid
• beginning and evolution of maculopathies
Manual Kinetic Perimetry (Goldmann)
• Advantages
an extensive or a peripheral defect can be individualized
topographic localization of visual field defects.
• Disadvantages less sensitive maintenance technician training
Automated Static Perimetry (Humphrey)
• Advantages automatic calibration standardized test procedures high sensitivity and specificity reliability checks
quantitative statistical analysis procedures
• Disadvantages prolonged test time increased cognitive demands fatigue
lack of flexibility for evaluating difficult patient populations
24-2 10-2
Before the Testing
• Position of the eyelids
• Refractive correction
• Pupil size
• Visual acuity
Common Artifacts(before and after)
Ptosis
Lens limb artifact
Common Artifacts(before and after)
Improper lens correction
Small pupil size (1mm 3mm)
Reliability Indices
• Fixation loss: < 20%
• False positive errors: < 33% (‘trigger happy’)
• False negative errors: < 33% (fatigue)
• Short-term fluctuation: increased with severe VF defect or fatigue
Unreliable Results (‘trigger happy’)
Plots• Numerical Display (dB, 높을수록 정상, < 0 dB [min])• Gray scale (잘 보이면 흰색)
• Total Deviation: 같은 연령대 정상인의 시야감도 분포 를 기준으로 각 점에서 감도가 얼마나 감소했는지 수 치로 표시(< 5, 2, 1, 0.5 %)
• Pattern Deviation: 전반적인 평균감도저하를 보정하 여 국소적으로 감도가 떨어진 부분을 표시 Global indices
• Mean deviation (MD): 모든 점에서 정상역치에 비해 올라간 정도(정상역치-각 점에서의 역치)의 평군
• Pattern standard deviation (PSD): 모든 점에서 정상역 치에 비해 올라간정도(정상역치-각 점에서의 역치)의 분산
1: Reliability Indices 2: Numerical Display 3: Grey Scale 4: Total Deviation 5: Probability Display 6: Pattern Deviation 7: Global Indices 8: Glaucoma Hemifield Test 9: Visual Field Index
Diffuse loss Mean deviation: -4.40 dB Pattern standard deviation: 1.54 db
Dense localized loss Mean deviation: -1.23 dB Pattern standard deviation: 4.54 db
Mild localized loss
“Trigger happy”
Monocular Field Defects
Central scotoma Inferior arcuate defect Superior altitudinal defect
Bitemporal Hemianopia
Bitemporal Hemianopia Lt. Homonymous Quadruple Sectoanopia
Rt. Homonymous Horizontal Sectoanopia
Lt. LGB in the territory of lateralchorodial artery
