scholarly journals A practical logMAR near reference table for low vision practitioners: Design and applications

2006 ◽  
Vol 65 (4) ◽  
Author(s):  
Alabi O. Oduntan
Keyword(s):  
Visual Acuity ◽  
Low Vision ◽  
Optical Devices ◽  
Visual Performance ◽  
Viewing Distance ◽  
Reference Table ◽  
Standard Values ◽  
Print Size

LogMAR  charts  are  particularly  useful  for visual acuity (VA) measurement for low vision patients  as  they  simplify  conversion  of  non-standard  viewing  distance  visual  acuities  to standard values. Also, the process of predicting various  quantities  involved  in  the  prescrip-tion of optical devices for patients are greatly facilitated.  However, the processes involved in the use of this logMAR principle require series of multiplication and division by the logMAR ratio  of  1.2589.   A  table  computed  and  pre-sented in this article provides easy reference for the conversions and predictions needed for the various quantities at near.  The table (Table 1) is computed using the logMAR scale of 1.2589 in logMAR, M and N notations. The table con-tains VA values between logMAR 1.4 (10M or 80 point) and logMAR 0.18 (1.3M or10 point) in steps of 1.2589 for reduced (non-standard) viewing distances  ranging from 31.8 cm (0.32 m)  to  3.2  cm  (0.03M).    The  table  contains values  which  can  be  used  to  convert  visual acuity values measured at reduced near view-ing distances to standard visual acuity values.  The values also can be used to represent any of  the  quantities  involved  in  the  prescription of optical devices for low vision patients. The use of the table for converting reduced distance VA values to standard values and for predict-ing optical powers and visual performance of low vision patients are discussed with relevant examples. Like all principles based on the log-MAR principles, the table is quite versatile in VA  conversion  and  prediction  of  the  various quantities  such  as  print  size  that  can  be  read by  the  low  vision  patient  when  factors  such as  viewing  distance    or  power  are  varied.

scholarly journals A practical logMAR near reference table for low vision practitioners: Design and applicationd

2006 ◽  
Vol 65 (4) ◽  
pp. 157-162
Author(s):  
Alabi O. Oduntan
Keyword(s):  
Visual Acuity ◽  
Low Vision ◽  
Optical Devices ◽  
Visual Performance ◽  
Viewing Distance ◽  
Reference Table ◽  
Standard Values ◽  
Print Size

LogMAR charts are particularly useful for visual acuity (VA) measurement for low visionpatients as they simplify conversion of non-standard viewing distance visual acuities to standard values. Also, the process of predictingvarious quantities involved in the prescription of optical devices for patients are greatly facilitated.  However, the processes involved in the use of this logMAR principle require series of multiplication and division by the logMAR ratio of 1.2589.  A table computed and presented in this article provides easy reference forthe conversions and predictions needed for the various quantities at near.  The table (Table 1) is computed using the logMAR scale of 1.2589in logMAR, M and N notations. The table contains VA values between logMAR 1.4 (10M or 80 point) and logMAR 0.18 (1.3M or10 point) in steps of 1.2589 for reduced (non-standard) viewing distances  ranging from 31.8 cm (0.32 m) to 3.2 cm (0.03M).  The table contains values which can be used to convert visual acuity values measured at reduced near viewing distances to standard visual acuity values.  The values also can be used to represent any of the quantities involved in the prescription of optical devices for low vision patients. The use of the table for converting reduced distance VA values to standard values and for predicting optical powers and visual performance of low vision patients are discussed with relevant examples. Like all principles based on the logMAR principles, the table is quite versatile in VA conversion and prediction of the various quantities such as print size that can be read by the low vision patient when factors such as viewing distance  or power are varied.

The Effects on Visually Impaired Children of Viewing Fluorescent Stimuli under Black-Light Conditions

1998 ◽  
Vol 92 (5) ◽  
pp. 313-321 ◽  
Author(s):  
S.J. LaGrow ◽  
J-P Leung ◽  
S. Leung ◽  
P. Yeung
Keyword(s):  
Visual Acuity ◽  
White Light ◽  
Visually Impaired ◽  
Low Vision ◽  
Visual Performance ◽  
Light Conditions ◽  
Black Light ◽  
High Acuity ◽  
Impaired Children ◽  
Visually Impaired Children

In this study, 30 children with low vision (divided into a high and a low visual acuity group) were presented with stimuli under four conditions (white stimuli-white light, orange stimuli-white light, white stimuli-black light, and orange stimuli-black light) and were asked to rank their preferences for the four conditions. The goal was to determine the effects of the various combinations of stimuli and lighting on the children's visual performance. The orange stimuli viewed under black light resulted in the best performance overall, benefited the low-acuity group more than the high-acuity group, and was the most-preferred condition for both groups.

scholarly journals An analysis of print sizes of South African newspapers in relation to prescription of reading devices for low vision patients

2005 ◽  
Vol 64 (2) ◽  
Author(s):  
A.O. Oduntan
Keyword(s):  
South African ◽  
Low Vision ◽  
Optical Devices ◽  
Bench Mark ◽  
Specific Knowledge ◽  
Reading Device ◽  
The Mean ◽  
Print Size ◽  
Experience Difficulty ◽  
Reading Aids

One  of  the  aspirations  of  many  low  vision patients is to read newspapers. Many low vision practitioners  use  1M  print  (Snellen  equivalent 6/15 at 40 cm or 6/24 at 25 cm) as the bench-mark for prescribing low vision optical devices for patients who wish to read newspapers. There are certain sections of the newspapers, however, with print sizes that are smaller than 1M, there-fore prescriptions based on 1M print size may present difficulties to the patient. The purpose of this study was to measure the smallest print sizes of  selected  sections  of  South African  newspa-pers. Based on the print size values, advice could be provided for effective prescription of reading devices for low vision patients whose desire is to read all or specific sections of newspapers.  Print  sizes  in  eight  sections  of  38  South African newspapers were measured using a 7x measuring magnifier with graticle. The smallest print sizes in the various sections of the newspa-pers ranged from 0.6 mm or 0.4M  (6/9.5 at 25 cm or 6/6 at 40 cm) to 1.9 mm or 1.3M (6/30 at 25cm or 6/20 at 40 cm). The mean sizes of the various sections of the newspapers ranged from 0.7  ±  0.18M  for  the  advert  section  to  1.12  ± 0.07M in the news section.  Reading device magnification established by using 1M print size as benchmark for prescrib-ing reading aids for low vision patients may not afford  the  visual  capability  needed  to  read  all sections of a newspaper. Such patients, thus may experience difficulty when reading certain sec-tions of newspapers. There is therefore, a need for  low  vision  practitioners  to  have  a  specific knowledge of the print sizes of the section of newspapers  that  the  patient  wants  to  read  and prescribe for them accordingly.

Characteristics of Students Evaluated at a Residential School's Low Vision Clinics, 1981–1991

1993 ◽  
Vol 87 (6) ◽  
pp. 180-182
Author(s):  
M.E. Wilkinson ◽  
I. Stewart
Keyword(s):  
Visual Acuity ◽  
Low Vision ◽  
Optical Devices ◽  
Corrected Visual Acuity ◽  
Best Corrected Visual Acuity

The records of 360 students who are evaluated at the low vision clinics of the Iowa Braille and Sight Saving School over a 10-year period were surveyed to determine the characteristics of this population. The factors that were reviewed included age, sex, ocular condition, best-corrected visual acuity at far and near, and recommended optical devices.

The Experience of a Randomized Clinical Trial of Closed-Circuit Television versus Eccentric Viewing Training for People with Age-Related Macular Degeneration

2017 ◽  
Vol 111 (4) ◽  
pp. 354-368 ◽  
Author(s):  
Susan J. Leat ◽  
Francie Fengqin Si ◽  
Deborah Gold ◽  
Dawn Pickering ◽  
Keith Gordon ◽  
...  
Keyword(s):  
Visual Acuity ◽  
Macular Degeneration ◽  
Vision Loss ◽  
Low Vision ◽  
Reading Speed ◽  
Optical Devices ◽  
Reading Performance ◽  
Age Related Macular Degeneration ◽  
Eccentric Viewing ◽  
Age Related

Introduction In addition to optical devices, closed-circuit televisions (CCTVs) and eccentric viewing training are both recognized interventions to improve reading performance in individuals with vision loss secondary to age-related macular degeneration. Both are relatively expensive, however, either in the cost of the device or in the amount of time personnel need to provide training. In this randomized trial, we compared the effectiveness of these two interventions. Methods Participants with age-related macular degeneration and visual acuity between 6/48 (20/160) and 6/120 (20/400) first received basic low vision care, including optical devices. At the subsequent baseline visit, they undertook a battery of measures including logMAR visual acuity; reading speed and accuracy for text in 1.3M and 1M fonts; reading information on medicine bottles, utility bills, and food packages; the NEI-VFQ; the Geriatric Depression Scale; and a reading inventory questionnaire. They were then randomized to either obtaining a CCTV for home use or eccentric viewing training over the following six weeks. Results Recruitment was more difficult than expected for this population. Of 145 patients referred, 29 met the inclusion-exclusion criteria, 14 were willing to enroll, and 10 completed the trial. For the primary outcome (reading speed for 1.3M print), there was a significant improvement between baseline and outcome for the CCTV group (p = 0.005), but not for the eccentric viewing training group (p = 0.28), and the CCTV group showed significantly greater change (p = 0.04). There was a nonsignificant improvement in reading speed for 1M text and a decrease in the amount of time taken to read utility bill information in the CCTV group. There was a significant improvement in near visual acuity with current glasses with eccentric viewing training. The other measures did not reach statistical significance. Discussion Randomized clinical trials for low vision rehabilitation, particularly in the elderly population with vision loss, are challenging, but such trials are important for the allocation of resources. This trial showed early indications of more impact on reading performance from CCTV than eccentric viewing training.

CLINICAL CHARACTERISTICS AND RESULTS OF CATARACT SURGERY IN THE SMALL PUPIL EYE BY PHACOEMUSIFICATION

2018 ◽  
pp. 79-82
Author(s):  
Van Minh Pham ◽  
Van Nam Phan ◽  
Thi Thu Nguyen
Keyword(s):  
Visual Acuity ◽  
Cataract Surgery ◽  
Clinical Characteristics ◽  
Low Vision ◽  
Sample Selection ◽  
Posterior Chamber ◽  
Good Visual Acuity ◽  
Before And After ◽  
Grade Ii ◽  
Small Pupil

Objectives: To investigate the clinical characteristics of cataract patients with small pupils and to evaluate the result of cataract surgery on the eye have small pupils by phacotechnique. Subjects and methods: Descriptive study, prospective, uncontrolled interventions. Sample selection. The sample size of 70 patients with 70 eyes of cataracts with small pupils was treated by phaco technique and intraocular lens implant within posterior chamber. Follow up to 3 months. Results: 70 eyes, the percentage of men and women was not different from 54.2% (38 male) compared to 45.8% (32 female). The mean age was 80 ± 8.74, from 58 to 99 years. The disease was mainly found in the age group over 70 years old with over 80% (51.5%). Visual acuity before surgery was very poor under 3m CF (count finger) for 68.6% (48/70). Visual acuity over 1/10 was only a small amount with 2.8% (2 eyes). Pseudoexfoliation was the most common reason complications of mydriasis with 32/70 eyes (45.7%) and 22/70 eyes (31.4%) for age. The preoperative pupilarysizewas mostly small with 63/70 eyes (90.0%), non-dilated pupils (7/70 eyes) (10.0%). Average pupil size was 3.34 mm (2 - 4mm). Iris condition: iris atrophy 20/10 eyes (28.6%), iris synechiae 11/10 (15.7%), irregular iris muscle with 51, 4% and good iris muscle accounted for 48.6%. Grade of cataract: Grade III: 31/70 eyes (44.3%), Grade IV: 32/70 eyes (45.7%), Grade II: 5/70 eyes (7.1%) and V:2/70 eyes (2.9%). Pupil expander technique: OVD injection with 42/70 eyes (60%), using iris hook with 23/70 eyes (32.9%). Pupillary size before and after intervention has changed from 3.7mm to 4.48mm. Conclusions: Iris expander techniques have been shown to have good dilated pupils: 60.0% OVD injection, iris hook was 32.9%, other methods 7.1% One-week visibility of good visual acuity was higher than that of postoperative one day (12.2%) and increased at 1 month and 3 months (20.0%). Very good visual acuity was not available and low vision group was 1.4% after 3 months. Key words: cataract surgery; phacoemusification, small pupil

scholarly journals Epidemiological Findings of Refractive Errors and Amblyopia among the Schoolchildren in Hatta Region of the United Arab Emirates

2021 ◽  
pp. 1-7
Author(s):  
Salam Chettian Kandi ◽  
Hayat Ahmad Khan
Keyword(s):  
Visual Acuity ◽  
Visual Field ◽  
United Arab Emirates ◽  
Refractive Error ◽  
Screening Program ◽  
Low Vision ◽  
Refractive Errors ◽  
Vision Screening ◽  
Screening Programs ◽  
School Based

<b><i>Introduction:</i></b> Uncorrected refractive errors and amblyopia pose a major problem affecting schoolchildren. We had previously observed that many schoolchildren in the Hatta region presented to the ophthalmology clinic with uncorrected refractive errors and amblyopia, which led us to undertake this research. As per the WHO, the term “visual impairment” can be “low vision” or “blindness.” Based on the presenting vision, “low vision” is defined for children who have vision of &#x3c;6/18 to 3/60 or having visual field loss to &#x3c;20° in the better-seeing eye. Children defined to have “blindness” have presenting vision of &#x3c;3/60 or corresponding visual field of &#x3c;10°. <b><i>Purpose:</i></b> To estimate the magnitude of uncorrected refractive errors and amblyopia among the schoolchildren aged 6–19 years and to assess the efficacy of school-based refractive error screening programs in the Hatta region of the United Arab Emirates. <b><i>Methods:</i></b> An epidemiological, cross-sectional, descriptive study was conducted on the entire student population studying in the government schools of the region. Those who failed the Snellen visual acuity chart test and those who were wearing spectacles were evaluated comprehensively by the researcher in the Department of Ophthalmology of the Hatta Hospital. Data were entered in the Refractive Error Study in School Children (RESC) eye examination form recommended by the WHO, and were later transferred to Excel sheets and analyzed by SPSS. <b><i>Results:</i></b> 1,591 students were screened and evaluated from the end of 2016 to mid-2017. About 21.37% (<i>n</i> = 340) had impaired vision with 20.9% (<i>n</i> = 333) refractive errors, of which 58% were uncorrected. Among the refractive error group, 19% (64 subjects) had amblyopia (4% of total students). The incidence of low vision was 9.5% and blindness was 0.38%. Low vision was found to be 9.5% and blindness 0.38%, taking in to account presenting visual acuity rather than best-corrected visual acuity for defining low vision and blindness. <b><i>Conclusion:</i></b> A significant number of students were detected to have uncorrected refractive errors among the vision impaired group (59%, <i>n</i> = 197) despite a school-based vision screening program in place. Seventy-eight percent of the amblyopia cases (<i>n</i> = 50) were found to be in the 11–19 years age group. Noncompliance with optical corrections was the reason for the high number of cases. A rigorous vision screening program and refractive services, complimented with awareness among parents and teachers, are recommended.

scholarly journals Comparison of the visual performance of iris-fixated phakic lens and implantable collamer lens to correct high myopia

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Xiao-ling Jiao ◽  
Jun Li ◽  
Zhe Yu ◽  
Ping-hui Wei ◽  
Hui Song
Keyword(s):  
Visual Acuity ◽  
High Myopia ◽  
Optical Quality ◽  
Visual Performance ◽  
Quality Analysis ◽  
Modulation Transfer ◽  
Implantable Collamer Lens ◽  
Good Visual Acuity ◽  
Significant Difference ◽  
Group 6

Abstract Background To compare visual performance between the iris-fixated phakic intraocular len (pIOL) and implantable collamer len (ICL) to correct high myopia. Methods Twenty-four eyes underwent iris-fixated pIOL implantation and 24 eyes underwent ICL implantation. At the 6-month follow-up, the best-corrected visual acuity (BCVA) and uncorrected distance visual acuity (UDVA) were compared between the iris-fixated pIOL and ICL groups. The objective scatter index (OSI), modulation transfer function (MTF) cutoff, and ocular aberrations were performed to evaluate postoperative visual quality between the two groups. Results No significant difference was found in UDVA, BCVA, and spherical equivalent between the iris-fixated pIOL and ICL groups (P > 0.05). Six months after surgery, the following values were significantly higher in the ICL group than in the iris-fixated pIOL group: MTF cutoff, strehl ratio and optical quality analysis system values at contrasts of 9 %, 20 %, and 100 % (P < 0.01). The OSI in the iris-fixated pIOL group was higher than in the ICL group 6 months after surgery (P < 0.01). All high-order aberrations were slightly more severe in the iris-fixated pIOL group than in the ICL group 6 months after surgery, although only trefoil (P = 0.023) differed significantly in this regard. Conclusions Both iris-fixated lenses and ICLs can provide good visual acuity. ICLs confer better visual performance in MTF-associated parameters and induce less intraocular light scattering than iris-fixated pIOLs.

Vision through Various Scuba Facemasks

1974 ◽  
Vol 16 (4) ◽  
pp. 395-405 ◽  
Author(s):  
S. M. Luria ◽  
Steven H. Ferris ◽  
Christine L. McKay ◽  
Jo Ann S. Kinney ◽  
Helen M. Paulson
Keyword(s):  
Visual Acuity ◽  
Optical Properties ◽  
Visual Fields ◽  
Differential Susceptibility ◽  
Visual Performance ◽  
Visual Process ◽  
Hand Eye Coordination ◽  
Size Estimates

The visual performance using five commercially avaible facemasks was compared. Measurements were made of visual fields, visual acuity, stereoacuity, hand-eye coordination, accuracy of distance estimates, and accuracy of size estimates at both near and far distances. In addition, the optical properties of the masks were measured and the susceptibility of each mask to fogging was tested. There were significant differences among the masks for every visual process tested. Some masks were superior for one purpose and inferior for another purpose. For example, the mask which had lenses designed to compensate for the optical distortions found under water improved size and distance estimates and hand-eye coordination, but degraded acuity and stereoacuity. The results were not expplained on the basis of differential susceptibility to fogging.

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