Dr. Priyanka Raj,R17968, Dr. Alka Jha, Dr. Manoj Kumar, Dr.Vireshwar Prasad
| Priyanka Raj, Alka Jha, Manoj Kumar, Vireshwar Prasad |
Abstract
Background: Comparison of refractive error obtained by auto refractometer and streak retinoscopy in children of age group 06-15 years. Material & Method: A clinic based study to compare refractive error obtained by auto refractometer and dilated retinoscopy after using atropine or homatropine, as required, in 50 children of age group 6-15 years. The mean spherical equivalent of the results obtained by both the methods were compared. Results: The refractive error observed by undilated auto refractometry showed a significant myopic shift as compared to the dilated retinoscopy. Also the post mydriatic test showed refractive error more in agreement with the dilated retinoscopy. Conclusion: The refractive error seen by auto refractometer is not a reliable finding in children below 15 years. Thus each and every child of this age group must undergo dilated retinoscopy before prescribing final glass.
Introduction
Refractive conditions are the most prevalent class of disabling visual disorders in the pediatric population.1-3 Uncorrected errors may lead to adverse results like amblyopia and esotropia in children especially in hyperopes,4 so it is imperative to utilize accurate methods of objective refraction when examining young children. Retinoscopy and autorefraction are the most commonly used methods of refraction for children.
Autorefraction is relatively quick and easy to perform so is used by most of us, but its reliability is questionable in pediatric age group. It is seen that there are children having normal visual acuity but the AR shows high refractive error. Therefore cycloplegic retinoscopy is important in this age group. As accommodation in children is very strong, cycloplegic agent is used to inhibit accommodation to calculate actual error. Accurate and well timed management is important for children; so paying a little more time on refraction in these cases may prevent the child from the morbidities.
Material and Methods
It was an institution based study involving 50 children (100 eyes) aged 6 to 15 years. Visual acuity was tested using Snellen’s acuity chart at a distance of 6 meter; slit lamp and fundus examination were also
| Upgraded Department of Ophthalmology – Darbhanga Medical College & Hospital, Laheriasarai, Bihar – India |
performed to see for anterior as well as posterior segment pathology. The exclusion criteria were; child
uncooperative for the examination, mental retardation, any anterior/posterior segment pathology which
can affect visual potential of the child. Automated refraction was performed prior to the administration of cycloplegics. It was followed by cycloplegic conventional retinoscopy and cycloplegic autorefraction. 4% lignocaine drop was instilled prior to administration of cycloplegic to minimize irritation. Homatropine 2% eye drops was used as cycloplegic. The pupillary reflex was assessed before the administration of the drop. Patients were instructed to instill the drop every 10 minutes for three times. Pupillary reflex and dilatation was being checked at half an hour and then at 45 mins. After adequate pupillary dilatation (6mm or more), cycloplegic conventional retinoscopy followed by cycloplegic autorefraction was performed. Conventional retinoscopy was performed with the help of streak retinoscope to determine both spherical and cylindrical measurements. Patient was sited at an arm length distance which approximates to 67 centimeter distance and asked to look at light from retinoscope.
Autorefractor Nidek 600 was used in the study. The child was comfortably seated in front of the Autorefractor, placing his chin at the chin-rest. Instrument was adjusted so that the pupil is concentric with the inner alignment. Measuring unit is moved and fine focused until a clear bright dot appears in the centre. When the bright dot is clearest in the centre, joystick button was clicked for taking reading. Three reading from each eye was taken and the average was taken for final calculation. The measurement in the other eye was done in the similar way. Autorefractor readings were taken both before and after cycloplegic was used. Post mydriatic test was performed for final prescription of glass.
Results
Results were obtained using paired t test. Data collected by non cycloplegic autorefraction, cycloplegic retinoscopy and cycloplegic autorefraction and final acceptance by the child were compared. In this study spherical equivalent, spherical and cylindrical errors were compared.
On comparing mean of spherical equivalent of non cycloplegic autorefraction (mean = -0.25 ± 1.7054) and cycloplegic retinoscopy (mean = 1 ± 2.316), the difference came to be statistically significant (p value <0.001).
There was a significant difference statistically (p value < 0.000418) in spherical power obtained by non cycloplegic autorefraction with mean (0.0525 ± 1.7430) and cycloplegic retinoscopy with mean (1.11 ± 2.3704). On comparing cylindrical power by these two methods there was significant difference with (p value <0.000196).
In case of cylindrical power by non cycloplegic autorefractor mean was (-0.61 ± 0.9047) whereas mean of cylindrical measurement by cycloplegic retinoscopy was (-0.2125 ± 0.5178), and that by cycloplegic autorefractor was (-0.46 ± 0.7668).
On comparing spherical values obtained by cycloplegic retinoscopy and autorefraction under cycloplegia with mean (0.6524 ± 2.20), statistically significant difference was found in sphere with (p value <0.0354) whereas the difference was statistically insignificant for cylinder (p value 0.052), when compared by these two methods.
Mean values and standard deviation are shown in the table 1 and p values in table 2.
Table 1: Descriptive Statistics
| N | Mean | SD | |
| Sphere Autorefraction (Non-Cycloplegic) | 100 | (+) 0.0525 | 1.7430 |
| Cylinder Autorefraction (Non-Cycloplegic) | 100 | (-) 0.6100 | 0.9047 |
| Sphere Cycloplegic Retinoscopy | 100 | (+) 1.1100 | 2.3704 |
| Cylinder Cycloplegic Retinoscopy | 100 | (-) 0.2125 | 0.5178 |
| Sphere Cycloplegic Autorefraction | 100 | (+) 0.6524 | 2.2000 |
| Cylinder Cycloplegic Autorefraction | 100 | (-) 0.4600 | 0.7668 |
N – total number of eyes; SD – standard deviation
Table 2: Significance Level
| P Value | |
| Sphere Cycloplegic Retinoscopy – Sphere Non Cycloplegic Autorefraction | <0.000418 |
| Cylinder Cycloplegic Retinoscopy – Cylinder Non Cycloplegic Autorefraction | <0.000196 |
| Sphere Autorefraction (Cycloplegic) – Sphere Cycloplegic Retinoscopy | <0.035400 |
| Cylinder Autorefraction (Cycloplegic) – Cylinder Cycloplegic Retinoscopy | 0.052000 |
Discussion
The study shows that the autorefraction without cycloplegia clearly showed a myopic shift as compared to cycloplegic retinoscopy and cycloplegic autorefraction. It means that minus power were more minus and plus power were of lower value to that obtained by retinoscopy. This leads to significant underestimation of error, especially in hypermetropes. The result shows statistically significant difference between retinoscopy to that of non cycloplegic autorefractor in case of cylinder as well as sphere. Also readings of spherical power by cycloplegic autorefractor showed significant difference with that of cycloplegic retinoscopy; but less significant as compared to difference in spherical power by non cycloplegic autorefractor to that with cycloplegic retinoscopy. Whereas difference in readings of cylindrical powers by cycloplegic autorefractor to that obtained by cycloplegic rateniscopy was not significant.
Similar results were obtained in a study done by Rajko Pokupec5 & Danijela Mrazovac6 Difference was statistically significant both for sphere (p value = 0.017) and for cylinder (p value = <0.001), when comparison was done between values obtained by non cycloplegic autorefractor and retinoscopy. Difference was also significant when comparison was done between cycloplegic autorefraction and retinoscopy.
Since subjective correction is the gold standard for refraction, results were evaluated on the basis of post mydriatic test also. 93% of cycloplegic retinoscopy spherical correction were within ±0.50D of post mydriatic test values. 86% of readings of sphere by cycloplegic autorefractor were within the same range. Only 53% readings of non cycloplegic autorefractor showed the result within the same range. Table 3 & Table 4 shows the Percentage of measurement of spherical & cylindrical Power in agreement with Post Mydriatic Test.
| Table 3: Percentage of measurement of Spherical
Power in agreement with Post Mydriatic Test
|
Table 4: Percentage of measurement of Cylindrical
Power in agreement with Post Mydriatic Test
|
95% of cycloplegic retinoscopy cylindrical power measurements were within ±0.50D of post mydriatic test values, whereas 91% of cycloplegic autorefraction cylindrical power measurements were within this range. 81% of non cycloplegic autorefractor measurement for cylinder was in this range.
So it clearly demonstrates that post mydriatic test results are more in accordance with the cycloplegic retinoscopy.
S Pedamallu7-8 & K Reddy9-11 in a study found that results of 97% of spherical correction by cycloplegic autorefraction agreed within ± 0.5 D of post mydriatic test values whereas it was 98% in case of cycloplegic retinoscopy and only 52% in case of non cycloplegic auto refraction. Results of cylinder also were similar to those obtained in this study.
Conclusion
Difference in cycloplegic retinoscopy and cycloplegic autorefraction spherical power measurements are statistically significant, though not significant for cylindrical readings. Least reliable measurement was with non-cycloplegic auto refraction. So, it is better to determine correction with cycloplegic retinoscopy only, as it gives best results among all the three. Accurate prescription of power is very much required to avoid potential hazards of amblyopia and strabismus in young children whose whole life will be affected by wrong prescription. Also the academic performance is influenced by the refractive error. So to obtain correct reading, every child must undergo cycloplegic retinoscopy.
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