Ophthalmic Microscope Autofocus Using Low-Coherence Interferometry

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Solution Overview

Problem

Existing ophthalmic microscopes struggle to maintain focus on the internal limiting membrane (ILM) during vitreomacular surgeries due to involuntary patient movements, such as respiration, leading to prolonged surgery duration and potential complications.

Innovation Solution

An autofocusing system using low-coherence interferometry with a low-coherence infrared light source and an interferometer to automatically adjust the focus of the microscope lenses based on the axial distance to the ILM, enabling rapid focus adjustments to accommodate patient movements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If manual focusing is used during vitreomacular surgery, then the surgeon can control the focus, but the ILM goes out of focus due to patient movements such as respiration

Engineering Contradiction:

Improvefocus maintenanceVSAvoidsurgery duration

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system uses an interferometer to automatically measure the axial distance to the ILM and control the microscope focus without surgeon intervention. The autofocus system serves itself by continuously tracking ILM position and adjusting focus automatically, eliminating the need for manual focusing during surgery.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The interferometer provides real-time feedback on the axial distance to the ILM, which is fed to the control system to continuously adjust the microscope focus. This closed-loop feedback mechanism ensures the ILM remains in focus despite patient movements.

Inventive Principle:

Principle #23Feedback

2Ease of operation

If manual focusing is used, then the system is simpler, but the surgeon must continuously adjust focus during surgery

Engineering Contradiction:

Improvefocus adjustment effortVSAvoidsurgery efficiency

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

The autofocus system automatically tracks and adjusts focus on the ILM without requiring surgeon intervention. The system serves itself by using the interferometer to measure distance and the control system to adjust lenses, freeing the surgeon from manual focusing tasks.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The manual mechanical focusing operation is replaced by an automated optical measurement and control system. The interferometer optically measures the axial distance, and the control system automatically adjusts the microscope lenses, replacing the need for manual mechanical focus adjustment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Extent of automation

If an interferometer is added for autofocus, then automatic focus control is achieved, but the device complexity increases

Engineering Contradiction:

Improveautofocus capabilityVSAvoidsystem components

Core Design Contradiction:

Extent of automationVSDevice complexity

Solution Approach 1:

The interferometer is integrated into the existing ophthalmic microscope system, serving dual purposes: providing surgical illumination and performing autofocus measurements. This multi-functionality reduces the need for separate dedicated components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The interferometer, light source, and microscope control systems are merged into a single integrated autofocus assembly. The components work together as a unified system, with the interferometer measuring distance and the control system coordinating lens adjustment, reducing overall system complexity.

Inventive Principle:

Principle #5Merging (Combining)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The system ensures the ILM remains in focus without manual intervention, reducing surgery time and minimizing complications associated with manual focusing.

Implementation Method 1

the axial distance between the ILM and a focusing lenses of the microscope is performed using low-coherence interferometry

Methodology Applied

Scientific EffectLow-coherence interferometry: Interference

Implementation Method 2

a low-coherence infrared (IR) light source, for instance at least one super luminescent light-emitting diode (SLED)

Methodology Applied

Scientific EffectInfrared radiation: Infrared Radiation

Data Source

PatentUS20260000294A1Autofocus control for ophthalmic microscope using low-coherence interferometry

Publication Date: 2026.01.01 ALCON INC

AI summary

A system for automatically focusing (“autofocusing”) a microscope during an inner limiting membrane (ILM) peeling maneuver is configured to output low-coherence infrared (IR) light toward the eye during the maneuver. The system includes an interferometer that senses an axial distance between the microscope and ILM and outputs distance signals indicative of the sensed axial distance. An electronic control unit (ECU) is in communication with motor-driven lenses of the microscope and with an IR light source of the interferometer. Execution of the instructions causes the ECU to receive the distance signals from the interferometer. In response to the distance signals, the ECU transmits a focus control signal to the lens(es) to thereby resolve the ILM with a desired depth-of-field. The ECU automatically adjusts a focus level of the microscope on the ILM to accommodate for respiration-related movements of the patient.