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   Table of Contents      
COMMENTARY
Year : 2021  |  Volume : 69  |  Issue : 1  |  Page : 51-52

Commentary: A novel miniaturized visual acuity chart design


Binocular Vision Clinic, Sankara Nethralaya, Unit of Medical Research Foundation, Chennai, India

Date of Web Publication15-Dec-2020

Correspondence Address:
Dr. Jameel Rizwana Hussaindeen
Sankara Nethralaya, Medical Research Foundation, 18, College Road, Nungambakkam, Chennai, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ijo.IJO_2060_20

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How to cite this article:
Hussaindeen JR. Commentary: A novel miniaturized visual acuity chart design. Indian J Ophthalmol 2021;69:51-2

How to cite this URL:
Hussaindeen JR. Commentary: A novel miniaturized visual acuity chart design. Indian J Ophthalmol [serial online] 2021 [cited 2021 Jan 22];69:51-2. Available from: https://www.ijo.in/text.asp?2021/69/1/51/303290



Estimation of visual acuity remains the gold standard outcome measure to assess the vision potentials in Ophthalmology practice. The evolution of visual acuity charts dates back to the 1862 when the Dutch Ophthalmologist Herman Snellen designed an alphanumeric chart that fits within a 5 × 5 grid.[1] The chart later saw improvements in the design and continues to find its place in most eye care practices even after 2 centuries. The known flaws in the Snellen chart led to the development of the standard logMAR-based visual acuity charts[2],[3] such as the ETDRS visual acuity chart[4] which were then validated and continues to be the gold standard testing tool for visual acuity. Though logMAR-based visual acuity estimation has its technical advantages, it has not yet penetrated all eye care practices and the possible reasons include unfamiliar scoring system, perceptions related to the time consuming nature of the measurement and the chart's size.[5] This becomes more relevant in community eye care as the visual acuity tests need to be cost effective, portable, time saving, and also compact. There have been attempts in the past to overcome these difficulties with the development of tests such as the pocket vision screener,[6] modified logMAR,[7] and the reduced logMAR[5] visual acuity test charts.

The standard testing distance for visual acuity has remained 4 meters and beyond for estimating the visual acuity thresholds without ocular accommodation influencing the test results especially in younger population. This paper[8] brings out a new perspective to these attempts by coming out with the mini log MAR that shows reliability and repeatability at a 1 meter testing distance. The MLM deploys tumbling E optotypes scaled to be tested at 1 meters through a +1.00 DS spectacles to account for the dioptric demand. This chart has been validated on an adult sample with a mean age of 31.08 (14.86) years and has shown to be valid compared to the standard logMAR visual acuity estimates. The authors propose a regression equation to predict the visual acuity estimates at 6 meters based on the MLM estimates. The agreement between the calculated visual acuity with the MLM is well within the clinically agreeable limits compared to standard Log MAR visual acuity estimation. It is important to note that the chart has not been validated in the pediatric age group and also for a range of refractive errors. The clinician also needs to be aware of the standard lighting requirements to ensure accuracy of visual acuity testing. The use of the illiterate E optotype has advantages of reducing the cognitive load associated with identifying the optotype as the only variable influencing the measurement is the optotype size.[9] This makes it applicable for testing subjects who are not familiar with alphabets. But the directionality component of the tumbling E needs to be borne in mind when testing subjects who have confusions with orientation, and in the pediatric age group less than 8 years for whom the directionality sense is in the developmental phase. Nonetheless this miniaturized version of the standard logMAR does has its scope in the routine clinical and community vision screening practices for the adult population.



 
  References Top

1.
Snellen H. Letterproeven tot Bepaling der Gezigtsscherpte (PW van der Weijer 1862) cited in Bennett AG. Ophthalmic test types. A review of previous work and discussions on some controversial questions. Br J Physiol Opt 1965;22:238-71.  Back to cited text no. 1
    
2.
Bailey IL, Lovie JE. New design principles for visual acuity letter charts. Am J Optom Physiol Opt 1976;53:740-5.  Back to cited text no. 2
    
3.
Sloan LL. Needs for precise measures of acuity. Equipment to meet these needs. Arch Ophthalmol 1980;98:286-90.  Back to cited text no. 3
    
4.
Ferris FL 3rd, Kassoff A, Bresnick GH, Bailey I. New visual acuity charts for clinical research. Am J Ophthalmol 1982;94:91-6.  Back to cited text no. 4
    
5.
Rosser DA, Laidlaw DAH, Murdoch IE. The development of a “reduced logMAR” visual acuity chart for use in routine clinical practice Br J Ophthalmol 2001;85:432-6.  Back to cited text no. 5
    
6.
Raja M, Ramamurthy D, Srinivasan K, Varadharajan LS. Development of Pocket Vision Screener and its effectiveness at screening visual acuity deficits. Indian J Ophthalmol 2014;62:1152-5.  Back to cited text no. 6
[PUBMED]  [Full text]  
7.
Noushad B, Thomas J, Amin SV. Reliability of a modified logMAR distant visual acuity chart for routine clinical use. Oman J Ophthalmol 2012;5:87-90.  Back to cited text no. 7
[PUBMED]  [Full text]  
8.
Kauser F, Amitava AK, Saxena J, Raza SA, Masood A, Alam MS. Saving space: Comparing mini - logMAR with standard logMAR visual acuity. Indian J Ophthalmol 2021;69:48-51.  Back to cited text no. 8
  [Full text]  
9.
Taylor HR. Applying new design principles to the construction of an illiterate E chart. Am J Optom Physiol Opt 1978;55:348-51.  Back to cited text no. 9
    




 

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