How to Choose Syntonic Filters: A Practitioner's Guide to Filter Pairs and Protocols

2 days ago

6 min read

Learning how to choose syntonic filters is not about picking a colour from a chart. It is about reading a patient, deciding what their visual system needs right now, and matching that decision to a filter or a filter pair. This guide covers what a filter does, why practitioners work in pairs, how the 13-filter system is organised, the pairs that come up most often, and how to build a useful starter set.

Scope note: Syntonic phototherapy is a professional modality. Filter selection is determined by the prescribing practitioner, based on their own assessment of each patient. This guide describes how practitioners generally approach selection. It is not a prescription for any particular patient.

What a syntonic filter actually does

A syntonic filter sits between a light source and the patient's eyes. It does not change the light unit. It changes which parts of the visible light spectrum reach the eye, and in what balance.

That is why the filter is part of the prescription. Two patients can use the same light unit for the same time and have quite different sessions, because different filters were chosen for each of them. Selecting well depends on assessment, not on a preference for a colour.

One filter, or a pair?

Single filters have their place — for example, when introducing syntonics to a sensitive patient or testing a response. A single filter keeps the session simple and makes the response easier to read.

Most day-to-day work, however, is done with pairs. A pair lets the practitioner balance a session, supporting one function while settling another. Pairs are also how the traditional system is usually taught and recorded, which makes a protocol easier to document, repeat, and adjust.

For new practitioners, understand pairs first. Treat single-filter use as a later variation.

The 13-filter system, in plain language

The full syntonic system uses 13 filters, each with a Greek-letter name and a characteristic colour. You do not need to memorise all 13 on day one. Most protocols are built from five core filters:

Alpha — red. The warm, stimulating end of the core set, and one half of two widely used pairs.
Delta — amber. A warm, grounding filter that pairs readily with Alpha and with Mu.
Mu — green. The middle of the system, appearing most often in pairs for ongoing, established presentations.
Upsilon — blue. A cooler filter, often paired where a settling influence is wanted.
Omega — cobalt. A deep blue filter used where pain or emotional load is part of the presentation.

Once those five are familiar, the remaining filters are easier to place.

Five common filter pairs

These pairs come up repeatedly in practice. The descriptions are the traditional associations learned with each pair. They are not a promise of an outcome for any individual patient, and they do not replace assessment.

Alpha Delta — traditionally associated with lazy eye syndrome presentations.
Mu Delta — traditionally associated with chronic presentations.
Mu Upsilon — traditionally associated with acute presentations.
Upsilon Omega — traditionally associated with work where pain relief is part of the goal.
Alpha Omega — traditionally associated with presentations involving emotional fatigue.

Reading pairs as combinations helps more than memorising a list. Mu appears in both the chronic and acute pairs, with the second filter changing to suit the case. Alpha appears where stimulation is part of the picture, and Omega where load is being taken into account.

How practitioners actually choose

No responsible practitioner chooses from a diagnosis label alone. Selection draws on four sources, taken together.

Case history comes first: when the problem began, whether it is chronic or acute, and what the patient hopes to change. History alone can change the choice, as the chronic and acute pairs above show.

Pupil responses show how the patient's system is responding on the day, and can be rechecked between sessions.

Visual fields, charted at the start, show where function is reduced or constricted. Comparing later charts with the first is one of the clearest ways to track change.

Autonomic balance — between the activating and settling sides of the nervous system — sits behind much of syntonic selection. The pair is how a judgement about which side needs support is put into practice.

When those four point the same way, the choice is usually straightforward. When they do not, practitioners generally start conservatively and let re-assessment guide the next step.

Building a starter set that covers real work

A starter set should cover the core filters and common pairs, in formats you will use in the clinic and, where appropriate, at home. Hummingbird Hues supplies the main formats:

Glass filters with handles — the classic in-office format. Easy to hold, swap, and combine, which suits assessment and changing a pair mid-protocol.
Syntonic gel filters — a flexible format that works well with light units and suits a set made up for repeated use.
Filter goggles — hands-free, keeping filters in place for the full session. Useful for younger patients and anyone who finds it hard to stay positioned.
Clip-on filter glasses — these clip over a patient's own glasses, making them practical for home programs.
Plastic-framed syntonic glasses — ready-to-wear filtered glasses, simple to dispense and easy for patients to use correctly at home.

Start with the core filters in handled glass, then add one wearable format for home programs. That covers most early cases.

What a typical protocol looks like

Protocols vary by practitioner and patient, but a common pattern is a session of about 20 minutes, several times per week, over a course that often runs to around 20 sessions. The practitioner reviews progress during the course, repeating the pupil checks and visual field charting used at the start, and adjusts the pair if the presentation changes.

Some patients are also given a home program, using goggles, clip-ons, or plastic-framed glasses with a portable light unit, following the practitioner's filter choice and timings. Home use extends the plan; it does not replace assessment, so home filters and schedules should always come from the prescribing practitioner.

Consistency matters more than intensity — a steady schedule gives a clearer read on change.

Common mistakes when choosing filters

Choosing from the diagnosis alone. Two patients with the same label can need different pairs.
Skipping re-assessment. Without rechecking pupils and fields, you cannot tell whether the protocol should change.
Changing too much at once. If pair, session length, and schedule all change together, you cannot tell which change mattered.
Buying formats before filters. Cover the core filters first, then add formats.
Treating associations as guarantees. The pairs guide a choice; they do not determine a result.

Practitioner's checklist: choosing a filter pair

Take a full history; note whether the presentation is chronic or acute
Check and record pupil responses before the first session
Chart the visual field, for comparison with later charts
Form a view on autonomic balance — which side needs support
Select a filter or pair matching that assessment, and record why
Confirm you have it in a format suited to office or home use
Set session length and weekly schedule, and explain both to the patient
Book the review point, and recheck pupils and fields there
Change one element at a time if adjusting the protocol

Frequently asked questions

How many filters should I start with?

Start with the core filters that make up the common pairs — Alpha, Delta, Mu, Upsilon, and Omega — in one reliable office format, such as glass filters with handles. That gives you all five pairs above and covers most presentations a new practitioner will assess.

Do I need all 13 filters?

Not at the start. Many established practices hold all 13, but sound protocols can be run from the core set while you build experience, adding the rest as casework calls for them. Depth of assessment matters more than breadth of inventory.

Can two patients with the same diagnosis get different filters?

Yes, and this is normal. Selection is based on the individual assessment — history, pupils, visual fields, and autonomic balance — not on the label alone. Two patients with the same diagnosis may present differently on every measure, so a practitioner may prescribe different pairs for each.

How do I know if a pair is working?

Judge it from the measures taken at the start. Repeat the pupil checks, compare a new visual field chart with the first, and listen to the patient's report of day-to-day function. Change across those measures tells the practitioner whether to continue or adjust the pair. One session alone is not a reliable basis for that judgement.

Start with assessment, and the filters follow

Once history, pupils, visual fields, and autonomic balance are clear, the core filters and their common pairs turn that assessment into a protocol — and a starter set built around them will carry real clinical work.

Hummingbird Hues has supplied syntonic equipment to eye care professionals since 2012, including filters in the formats above, light units, and field charting tools.