FP1447 : Single Sweep Retinoscopy- Pediatric eye screening made easy.

Dr. Deepti P, Dr. Lakshmi K S, Dr. Krishna Prasad R, Dr. ANJANA KURI

Aims:

To study the effectiveness of SSRas a refractive screening modality in school going children.

Methods and Material:

Students aged 8-15years were screened for refractive errors in their schools.Children with other eye pathologies interfering with red reflex like corneal opacities and cataract were excluded.A trained ophthalmic personnel performed SSR in both meridian for every child and divided them as ‘against’ reflex(myopia) group & ‘dull with’ reflex(hypermetropia>5D) group and normal with reflex group. All children were subjected to automated refraction(AR) and the 2 readings were compared. The former two groups of children were shifted to the base hospital and the refractive errors were cross verified with cycloplegic refraction and PMT before giving spectacle prescription. The time taken for SSR and AR  reading per child was also noted and compared.

Statistical analysis used:

Descriptive statistics done manually. Statistical analysis of tests is done using medcalc online statistical software¹.

Results:

Of total 1210 eyes, 393(32.47%) eyes showed ‘against’ reflex of which 363(92.36%) were myopes of >1D,p-0.004. 817(67.52%)eyes showed ‘with’ reflex of which 40(4.89%) were hyperopes& 764(93.51%) were myopes<1D,p=0.0025.SSR has a sensitivity of 99.83%,specificity of 52.38%, negative predictive value of 91.67%. Average time taken per child to determine refractive error by automated refraction reading was 65+/-10 sec and that by SSR was 9+/-3 sec and this difference was statistically significant (p<0.001)

Conclusions:

SSR is an economic, easy and quick method to identify those who need further evaluation

Key-words: single sweep retinoscopy, school eye screening, mass screening

Key Messages: Single sweep retinoscopy is a good screening tool for mass school refractive screening

Introduction:

Undiagnosed and uncorrected refractive errors still stands as the most common cause of visual impairment in school going children of India. Vision 2020-right to sight,² a global initiative launched in 1999 stresses on the refractive error correction for which early detection of refractive errors in imperative.At the time, it was estimated that globally there were 1.4 million blind children, twice this number with low vision, and an estimated 500,000 children becoming blind each year.³ A study done by R Dandona et al shows that treatable refractive error causes 33% of childhood blindness.⁴Childhood blindness causes significant economic burden on the family and community. The specific need in school going children are diagnosis of newly developed refractive error or the diagnosis of pre existing undetected refractive error and to treat amblyopia aggressively as the upper age limit is dangerously close in them. Vision assessment has been the traditional screening modality for school going children. But because of increased amplitude of accommodation in children, there can be false negatives with this method. With the advent of photoscreeners and autorefractometers, screening has become more sophisticated. But somewhere in the middle of this inventive era, our humble and modest ‘retinoscope’ has taken a backseat. The skill that we all acquire during postgraduation for accurate retinoscpy is not being regularly put to use in this particular setting.

The objective of this study is to evaluate the accuracy and effectiveness of single sweep retinoscopy for diagnosis of refractive errors in school children.

Subjects and Methods:

This prospective study was conducted by a tertiary care eye hospital in South India from October, 2017 to March, 2018. 1210 school going children aged 8 to 15 years were included in our study.

Exclusion criteria :

• Media opacities like corneal opacity and cataract
• Previous intraocular surgeries

The children were made to stand in a line in a room preferably in their assembly hall and a trained ophthalmic personnel performed single sweep retinoscopy with a streak retinoscope in plano mirror position. The sweep retinoscopy was done in both meridian with accommodation at rest (child looking into distance) for every child and the type of reflex seen from retinoscope was noted.

Based on the reflex, the children were divided into 2 groups.‘against’ reflex(myopia) group and ‘with’ group. The ‘with reflex group were further divided into ‘bright with’ reflex subgroup and ‘dull with’(high hyperopia) reflex subgroup.  All children were subjected to automated refraction and statistical analysis for the single sweep retinoscopy as a screening test was done. The time taken for single sweep retinoscopy and automated refraction reading per child was also noted and compared using T-test with 2 independent variables.

Children in ‘against reflex’ group and ‘dull with’ reflex group were shifted to the base hospital and the refractive errors were cross verified with and cycloplegic refraction and subjective correction before giving spectacle prescription.

Results:

Of total 1210 eyes, 393(32.47%) eyes showed ‘against’ reflex of which 363(92.36%) were myopes of >1D. 817(67.52%)eyes showed ‘with’ reflex of which 40(4.89%) were hyperopes& 764(93.51%) were myopes<1D.Single sweep retinoscopy has a sensitivity of 99.83%,specificity of 52.38%, positive predictive value of 98.33%, negative predictive value of 91.67% and an accuracy of 98.20% in screening refractive errors[table 1 and table 2]. The high values for sensitivity, negative predictive value and accuracy suggests that this is an excellent screening tool.Average time taken per child to determine refractive error by automated refraction reading was 65+/-10 sec and that by single sweep retinoscopy was 9+/-3 sec. A T test with 2 independent variables showed that this difference was statistically significant with p<0.001[table 3 and table 4].

Discussion:Streak retinoscope has been in existence since 1920. It is mere serendipity that it came to existence when Jack C. Copeland, apparently after accidentally damaging the bulb of a Wolff Spot retinoscope when he dropped it and realized the effectiveness of a streak in recognizing astigmatism.⁵ It is nearly 10 decades post the invention now and it still remains a very useful device. In developing countries, every ophthalmologist and optometrist usually owns one. Myopia is a common cause of visual impairment which is usually acquired and nearly always progressive. It rarely occurs before the age of 5 years and new cases appear throughout childhood and adolescence, particularly between the ages of 6 to 15 years.⁶It is relatively easy to identify myopia of more than -1D using retinoscopy as it presents with‘against reflex’.

We have used single sweep retinoscopy to screen refractive errors in children. To the best of our knowledge, this is the first study of its kind. We found several advantages to our test

1. The test has good sensitivity and accuracy making it an ideal screening test
2. It is a relatively easy and simple test to administer
3. It takes less than 15 seconds to screen a child and can potentially screen a large population within a short period as the test does not take long to administer
4. Can be administered using only a streak retinoscope minimizing costs when compared to a autorefractometer or a photoscreener

The limitations of our study are

1. Wide range of inter and intra observer variation
2. Trained ophthalmic personnel with some skill in retinoscopy required
3. Child co-operation varies for looking into distance target (to keep the accomodation at rest)
4. No quantification possible

We suggest that single sweep retinoscopy to be done in all children for refractive screening and the shortlisted myopic and high hypermetropic children be subjected to vision screening instead of vision screening in all children which is currently being followed in all schools of the country. We feel this saves time and increases effiency more effectively. Though further studies are required to evaluate the cost effectiveness and time effieciency of this test as compared with that of photoscreeners.

Conclusions:

In mass screening of school children, using automated refraction is cumbersome, relatively expensive and time-consumingwhen compared with single sweep retinoscopy. Hence sweep retinoscopyis an economic, easy and quick method to identify those who need further evaluation.

References:

1. Schoonjans, F. (2018). MedCalc’s Diagnostic test evaluation calculator. Retrieved from https://www.medcalc.org/calc/diagnostic_test.php
2. Pararajasegaram R. VISION 2020 — The Right to Sight: from strategies to action. American Journal of Ophthalmology, 1999, 128: 359–360.
3. World Health Organization. Global Initiative for the Elimination of Avoidable Blindness. WHO/PBL/97.61.Geneva: World Health Organization; 1999.
4. Dandona R, Dandona L. Childhood blindness in India: a population based perspective. The British Journal of Ophthalmology. 2003;87(3):263-265.
5. Handley, N. (n.d.). Retinoscopes. Retrieved from https://www.college-optometrists.org/the-college/museum/online-exhibitions/virtual-ophthalmic-instrument-gallery/retinoscopes.html
6. R Hose, SandeepSachdeva et al. School eye screening and the National program for control of blindness, Indian Pediatrics, 2009;46:205-210.