A standard mouse requires a level of dexterity that not everyone has:

• Being able to move the mouse accurately through large and small distances.
• Repetitive finger pressure to click a button or spin a wheel.
• Stretching to where the mouse is situated, often well to the right of the keyboard.

Even if someone has the dexterity, continuous movements of these types may cause a repetitive strain injury (RSI) that makes further use of the mouse impossible.

Hence there is continuous innovation in developing alternatives to the mouse. The latest I have seen is the LightIO Starfish http://www.lightio.com.

To operate, a user points an infrared penlight at a small receiver box that contains sensors. Most of the sensors are distributed in two concentric circles and look like a starfish. When a sensor is activated the cursor moves in the direction on the circle, the inner ring is for fast movements and the outer ring for slower more accurate (pixel by pixel) movements. Other sensors provide mouse clicks, scrolling and drag-and-drop functions.

This novel approach should be ideal for people who can make small accurate movements with their hand but finds finger movements, especially repetitive movements, difficult or painful.

The forces needed to operate the penlight is less than that needed for writing with a pen as there is no friction. The repetitive pressures of the fingers are completely eliminated.

To move the cursor, the penlight is kept pointing at one hole and the hand is actually resting. To start and stop the cursor moving the penlight is moved on and off the hole, which is a movement of only a few millimetres. This means that the amount the hand has to be moved is considerably less than a standard mouse and therefore less strain is put on the hand.

The Starfish can be placed anywhere: hanging beneath the keyboard, resting on the user's lap or besides the screen, as long as the light from the pen can reach its surface. This means that the user can find a position that is comfortable for them.

The device does eliminate many of the issues related to using a standard mouse. However, it does require the user to be able to make small, accurate and steady movements. It also has no tactile feedback so the user must look at the device, from time to time, whilst using it. This device should appeal to users who can move their hands small distances but cannot use their fingers; an obvious group would be people with arthritis in the fingers.

The Starfish is not the answer for everyone wishing to replace the standard mouse but is an important addition to the options available which will ideally suit a percentage of users.