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Explain
Reading File
Here is a full explanation of this Topcon autorefractor + keratometer printout from an eye clinic:
What This Printout Is
This is an automated eye measurement report generated by a Topcon machine (a combined autorefractor and keratometer). It gives the doctor two types of data:
- REF. DATA - the refractive error of each eye (how much the eye needs glasses)
- KRT. DATA - the curvature of the cornea (front surface of the eye)
Header Information
| Field | Meaning |
|---|---|
| Date/Time | 14 July 2026, 10:40 AM |
| NO. 5133 | Measurement number |
| SN: 4769776 | Serial number of the machine |
| VD: 12.00 | Vertex distance - 12 mm (distance from back of lens to the eye, standard is 12-13.75 mm) |
| CYL: MIX | Cylinder notation format (MIX = mixed, but here means the prescription uses negative cylinder convention) |
| PD: 61.0 | Pupillary distance = 61 mm (distance between the two pupils - used for making glasses) |
REF. DATA - Refraction (Glasses Prescription)
The columns are: S (Sphere), C (Cylinder), A (Axis), and S.E. (Spherical Equivalent)
Right Eye <R>
| Parameter | Value | Meaning |
|---|---|---|
| S (Sphere) | -0.50 | Mild myopia (nearsightedness) |
| C (Cylinder) | -0.25 | Mild astigmatism |
| A (Axis) | 42° | Direction of the astigmatism |
| S.E. | -0.75 | Spherical Equivalent = S + (C/2) = -0.50 + (-0.125) = -0.625, rounded to -0.75 |
Left Eye <L>
| Parameter | Value | Meaning |
|---|---|---|
| S (Sphere) | -0.75 | Mild myopia |
| C (Cylinder) | -- | No significant cylinder detected |
| A (Axis) | -- | Not applicable |
| S.E. | -0.75 | Same as sphere since no cylinder |
Summary: Both eyes have mild myopia (short-sightedness). The right eye also has a small amount of astigmatism. These are low-grade values - this person needs weak distance glasses (or may even be borderline).
KRT. DATA - Keratometry (Corneal Curvature)
This measures the steepness/shape of the cornea. The machine measures two principal meridians (R1 and R2) and calculates the average.
Columns: D (Diopters - power), MM (radius of curvature in millimeters), A (Axis in degrees)
Right Eye <R>
| Reading | Diopters (D) | Radius (MM) | Axis |
|---|---|---|---|
| R1 (flat meridian) | 42.00 D | 8.02 mm | 176° |
| R2 (steep meridian) | 42.50 D | 7.92 mm | 86° |
| AVE (average) | 42.25 D | 7.97 mm | - |
| CYL (corneal astig.) | -0.50 D | - | 176° |
Left Eye <L>
| Reading | Diopters (D) | Radius (MM) | Axis |
|---|---|---|---|
| R1 (flat meridian) | 42.00 D | 8.05 mm | 165° |
| R2 (steep meridian) | 42.50 D | 7.95 mm | 75° |
| AVE (average) | 42.25 D | 8.00 mm | - |
| CYL (corneal astig.) | -0.50 D | - | 165° |
What the keratometry values mean:
- Normal corneal power is roughly 40-47 diopters. Both eyes at ~42.25 D are perfectly normal.
- Normal radius of curvature is ~7.5-8.0 mm. Both eyes are within normal range.
- The corneal cylinder of -0.50 D in both eyes indicates mild regular corneal astigmatism - the cornea is slightly oval rather than perfectly spherical. This is consistent with the refraction data.
- The two meridians (R1 and R2) being close together (only 0.50 D difference) confirms the astigmatism is mild.
Overall Clinical Interpretation
This person has:
- Mild bilateral myopia (both eyes need a weak minus lens for distance vision)
- Low-grade astigmatism bilaterally (more clearly seen in the corneal readings)
- Normal corneal shape with no signs of keratoconus or any corneal pathology
- Normal pupillary distance of 61 mm
The autorefractor findings would typically be used as a starting point for the optometrist/ophthalmologist to perform a subjective refraction (the "which is clearer - 1 or 2?" test) before finalizing the actual glasses prescription. The final prescription may differ slightly from these machine readings.
This patient use glasses with one lens spherical and other cylinder
That makes perfect sense when you look at the data carefully.
Why One Lens is Spherical and the Other is Cylindrical
Left Eye <L> → Spherical lens only
The autorefractor shows:
- S: -0.75, C: (blank), A: (blank)
- S.E.: -0.75
The left eye has no significant cylinder detected by the machine. So the lens prescribed is a simple spherical -0.75 D lens - it corrects only the myopia, with no astigmatism correction needed.
Right Eye <R> → Cylindrical (sphero-cylindrical) lens
The autorefractor shows:
- S: -0.50, C: -0.25, A: 42°
The right eye has both myopia AND astigmatism, so the lens must have:
- A spherical component (-0.50 D) to correct the myopia
- A cylindrical component (-0.25 D at axis 42°) to correct the astigmatism
This type of lens is called a toric lens or sphero-cylindrical lens - it has different powers in different meridians.
Why the Difference Between the Two Eyes?
Look at the keratometry data:
| Eye | R1 | R2 | Corneal Cyl |
|---|---|---|---|
| Right | 42.00 D | 42.50 D | -0.50 D at 176° |
| Left | 42.00 D | 42.50 D | -0.50 D at 165° |
Interestingly, the cornea of both eyes shows the same -0.50 D of astigmatism. However, in the left eye, the lenticular astigmatism (from the lens inside the eye) may be compensating/neutralizing the corneal astigmatism, resulting in little to no net astigmatism at the spectacle plane. This is called compensated or internal astigmatism - not uncommon.
In the right eye, the corneal astigmatism is not internally compensated, so it shows up in the refraction and needs correction in the glasses.
Summary
| Eye | Glasses Lens Type | Prescription |
|---|---|---|
| Right | Sphero-cylindrical (toric) | -0.50 DS / -0.25 DC × 42° |
| Left | Spherical only | -0.75 DS |
This is a fairly common clinical finding - it is perfectly normal to have different lens types in each eye of the same pair of glasses.
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