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# init(sphere:cylinder:axis:addPower:baseCurve:diameter:)

Creates a new contact lens specification, containing the prescription data for one eye.

```
init(sphere: HKQuantity, cylinder: HKQuantity?, axis: HKQuantity?, addPower: HKQuantity?, baseCurve: HKQuantity?, diameter: HKQuantity?)
```

## Parameters

`sphere`

The correction for farsightedness, measured in [`diopter()`](/documentation/HealthKit/HKUnit/diopter()) units. The range is -10.5 to +6.5.

`cylinder`

Part of the correction for astigmatism. This property measures the strength of the correction in [`diopter()`](/documentation/HealthKit/HKUnit/diopter()) units. The range is -3.0 to 3.0.

`axis`

Part of the correction for astigmatism. This property measures the orientation of the correction in [`degreeAngle()`](/documentation/HealthKit/HKUnit/degreeAngle()) units.

`addPower`

The correction for nearsightedness, measured in [`diopter()`](/documentation/HealthKit/HKUnit/diopter()) units. The range is from 0.25 to 2.5. The right and left eyes should have the same value.

`baseCurve`

Part of the contact’s fit, it measures the curve of the back side of the contact, measured in mm. The range is 7.8 to 9.2 mm.

`diameter`

Part of the contact’s fit, it measures the diameter of the lens, measured in mm. The range is 9 to 15 mm.

---

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