---
title: "init(sphere:cylinder:axis:addPower:baseCurve:diameter:)"
framework: healthkit
role: symbol
role_heading: Initializer
path: "healthkit/hkcontactslensspecification/init(sphere:cylinder:axis:addpower:basecurve:diameter:)"
---

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

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

## Declaration

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

## Parameters

- `sphere`: The correction for farsightedness, measured in doc://com.apple.healthkit/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 doc://com.apple.healthkit/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 doc://com.apple.healthkit/documentation/HealthKit/HKUnit/degreeAngle() units.
- `addPower`: The correction for nearsightedness, measured in doc://com.apple.healthkit/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.