|Year : 1983 | Volume
| Issue : 7 | Page : 1038-1039
Sato's optometer v/s retinoscopy
SG Ramnarayan Rao
131, K Hanumanthaiah Road, Banglore, India
S G Ramnarayan Rao
131, K Hanumanthaiah Road, Banglore
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Ramnarayan Rao S G. Sato's optometer v/s retinoscopy. Indian J Ophthalmol 1983;31, Suppl S1:1038-9
Optometers are instruments that have been designed to determine the degree of ametropia.
Most of the Optometers are used for objective optometry but the results obtained by them are altered by accomodative activity and pupillary size of the subject.
Sato's Optometer is designed to measure ametropia subjectively. This instrument has been widely used in Japan over the past twenty years. Spherical correction is made is this instrument by turning the knob and cylinder bars are introduced to correct astigmatism.
In this study the results obtained by the use of Sato's Opthometer are sompared with the results of retinoscopy in a series of 100 cases (200 eyes).
The following refinements of subjective testing are included in the Sato's Optometer.
| Methods to induce relaxation of accommodation|| |
1. Fogging Method: This is well known method of inducing the accommodation to relax in the absence of cycloplegia. Convex spheres to the extent of 4.0 or 5.0 is placed in front of the eye and then gradally reduced till maximum visual acuity is reached. With the Sato Optometer testing is started with the scale set at 5 diopters by turning the knob. Test Chart `A' is inserted info the optometer and the knob is turned till the lowest line is clear.
Spherical reading is noted. This procedure is repeated two or three times. In the Optometer a flickering green light is used while performing this test. This also helps to relax accommodation.
2. Tests to assess Astigmatism: In routine practice we are all aware of the use of astigmatic figures such as astigmatic fan for this purpose. In cases of regular astigmatism some lines are clear and those at right angles to these are blurred.
In Sato Optometer Test Chart B` with horizontal and vertical lines is inserted. If both set of lines are equally clear in both positions of 180°sub and at 45°sub then there is no astigmatism.
If one set of lines is clear then astigmatism is present. Test to determine the degree of astigmatism is carried out with patient slightly fogged by adding 0.5 to I diopter lens. The minus cylinders are added starting with higher power in the direction in which the lines are clear till both sets of lines are clear.
In cases where one set of lines is clear at 45°sub , change to Chart `D' with line in all 12. positions hours of a clock and find out what 0' Clock position of the line is clear. Insert cylinder bar in the direction of the time angle till all the lines are clear.
Using both spherical and cylinder together visual acuity is determined by using Chart `E' which denotes visual acutiy besides each line. Spherical power is again adjusted to obtain the best visual acuity. Fogging method is once again used while carrying out this test.
3. Test to verify the Correction used: This test makes use of chromatic aberration of the eye. short blue rays are brought to a focus in front of red rays. Green rays are brought to a focus in front of red rays. Green rays are brought to a focus between the blue and red. Using R &A (Red and Green) Chart in Sato Optometer the power is adjusted till red colour becomes distinct and the green colour is slightly blurred. This is the far point.
Result using Sato's Optometer were obtained by an assistant surgeon and they were compared with my retinoscopy results.
Following criteria were used for evaluation of results. Results were taken to be same in both cases if they were within 0.25 diopter of each other in smaller powers that is less then 4 diopters and within 0.5 diopter of each other in bigger powers that is more than 4 diopters.
Results of 100 cases were recorded and analysed in regard to the age of the patient and sex of the patient as shown in [Table - 1] and [Table - 2].
In the age group 10 years to 20 years 66.6% were correct, in the age group 11 years to 30 years, 68% were correct, in the age group 31 years to 40 years, 71% were correct, in the age group 41 to 50 years, 69% were correct and in the age group 51 years to 60 years, 68% were correct. Thus results are almost the same in all the age groups between 10 to 60 years. In total 68.5% of eyes were correct.,
Out of 100 cases there were 61 males and 39 females. The number of correct results among males was obtained in 82 eyes (67%) out of 122 eyes and the number of correct results among females was obtained in 55 (70%) eyes out of 78 eyes.
Sato's Optometer was found to be useful for preliminary testing by an assistant. It is specially useful in contact lens practice as spherical corrections obtained by this optometer reliable. It is also useful when media are opaque as to not allow retinoscopy.
[Table - 1], [Table - 2]