Astigmatism Diagnosis 2

January 01, 2018

Equipments:

Phoroptor 1 set, Chart vision 1 set.

Following to the Astigmatism Diagnosis 1, now we come to the fine adjustment for cylinder axis and power,

(Cross cylinder made by +0.25 cylinder power and -0.25 cylinder power, red dot means minus power, white dot means plus power)

First cylinder axis fine adjustment.

Put the +_0.25DC cross cylinder on the right eye, make sure the gear direction same with initial axis 60 degree.

Open the dot chart and turn over cross cylinder, let examinee identity which side vision most clear, if both side same clear, then the axis is finial axis, if no same clear situation, finial axis should be the one most close 180 or 90 degree. in this example, examinee says the first side more clear, stay on the clear first side, red dot close to the left of the gear, then axis add 10 degree to 70 degree, turn over cross cylinder, examine says second side clear, stay on the clear side, red dot close to the left of gear, then cut 5 degree to 65 degree, turn over cross cylinder, examinee says second side more clear, then cut 5 degree to 60 degree, the finial axis is 60 degree.

Now we come to the fine cylinder power adjustment.

Make the cross cylinder axis (red dot or white dot) same with the finial axis (60 degree), turn over the cross cylinder and let examinee identify which side more clear, if red dot side more clear, cylinder power should add-0.25DC, if white dot side more clear, cylinder power should cut-0.25DC, if both side same clear, then the finial cylinder is confirmed, if no same clarity happen, make sure white side clear (means use the smaller cylinder). Spherical power should cut -0.25D if cylinder power add over -0.50D; and if cylinder power minus -0.50DC, spherical power should add -0.25DS. If cylinder power adjust -0.25DC, then no need to adjust spherical power. Now the final is -0.50DC.

Close right eye, open left, operation same as right eye,

Then open both eye, let examinee look red-green chart to adjust the finial spherical power.

Measure PD

Now prescription is confirmed.