Gonioscopy Viva: Lenses, Grading Systems and Classic Questions

Start a gonioscopy viva with the optical reason for the lens. The iridocorneal angle is not normally visible directly at the cornea–air interface because light emerging from it undergoes total internal reflection. A gonioscopy lens changes that interface so angle structures can be viewed. Then move straight to a reproducible report: method, quadrant, most posterior structure, configuration, pigmentation, synechiae and indentation finding.

This is postgraduate examination education, not a guide to making a patient-specific diagnosis or treatment decision. Lens handling, illumination and documentation are learned with supervision and may vary by unit and lens design. The European Glaucoma Society guideline places gonioscopy within angle assessment; it does not turn one grade or sign into a management instruction.

The 20-second answer when shown a lens

If an examiner hands you a lens, do not begin with “this is for glaucoma”. Identify the optical category and what it lets you do.

The key contrast is direct versus indirect. Direct gonioscopy uses lens optics to allow direct viewing of the angle. Indirect lenses use mirrors. That distinction is safer than pretending that all named lenses are interchangeable. The AAO EyeWiki gonioscopy reference is a useful authority source for this vocabulary and the basic optical principle.

If asked how you would begin, give a practical but bounded answer: “I would position the patient at the slit lamp, use the appropriate lens and coupling method for this lens, minimise light and avoid prolonged pressure where angle configuration is being assessed.” Do not convert that sentence into a claim that there is one universal illumination setting or one mandatory coupling medium for every lens.

Structures: see them in order, report the most posterior one

The angle is easier to examine when you know its landmarks in anterior-to-posterior order. Use the sequence below as an identification framework, then adapt it to what is actually visible.

1. Schwalbe’s line
2. Trabecular meshwork, with the posterior portion often more pigmented than the anterior portion
3. Scleral spur
4. Ciliary body band
5. Iris root

Do not promise that every structure must be seen in every quadrant. Pigmentation, iris insertion, angle configuration, view quality, lens position and the individual eye can change what is visible. In an examination answer, it is better to say “the most posterior structure I can identify is the scleral spur” than to recite a structure that the view does not show.

When the examiner asks “what do you see?”, build the answer from observation rather than diagnosis: “In the superior quadrant, I can identify [most posterior structure]. The trabecular meshwork pigmentation is [finding]; the iris insertion/configuration is [finding]; and there are/are no visible peripheral anterior synechiae.” That is a report. “This is chronic angle closure” is an interpretation that needs more than one view.

Static gonioscopy: make the view reliable before grading it

An angle grade is only as good as the viewing conditions. In a practical station, mention enough technique to show that you understand the problem, then observe instead of narrating a whole textbook procedure.

• Centre the lens and obtain a stable view before trying to name structures.
• Examine all four quadrants. A single quadrant cannot represent the entire angle.
• Use the station’s requested illumination and avoid turning a narrow-angle assessment into an over-lit, prolonged observation.
• Separate what is visible from what you infer. “Trabecular meshwork is visible” is an observation; “the angle is open in every clinically relevant condition” is too broad.
• Document peripheral anterior synechiae by location and extent when present, rather than treating “PAS present” as a complete description.

The NCBI clinical overview of gonioscopy reinforces a point that is worth saying in a viva: gonioscopic findings are interpreted alongside the rest of the examination. In an exam, this translates to an honest limitation. You can describe an angle configuration and a dynamic response; you should not invent a disease label or individual management plan from one sign.

Indentation: a dynamic observation, not a decorative manoeuvre

Indentation gonioscopy applies controlled central pressure through an appropriate lens while you observe the peripheral iris-angle relationship. In a narrow-angle configuration, the iris may move posteriorly and reveal angle structures if closure is appositional. Peripheral anterior synechiae are adhesions and do not separate in the same way. This is an examination principle, not a standalone diagnostic conclusion.

Use this concise wording:

“With indentation, the peripheral iris [moved posteriorly/did not separate as observed], and [structure] became visible/remained obscured. I would record this as a dynamic gonioscopic finding and correlate it with the rest of the assessment.”

Avoid three traps. First, do not push so hard that you create an artefact and then call it anatomy. Second, do not label every non-opening area as synechial without a credible view. Third, do not state that a responsive angle excludes every other angle mechanism. The examiner wants to hear that you understand the difference between a reversible appositional configuration and an adhesion, and that your conclusion has limits.

Shaffer, Scheie and Spaeth: answer the system that was asked

The systems are not synonyms. A common viva mistake is to say a number confidently without declaring the language it belongs to.

For most short cases, the better answer is not a recital of every numerical threshold. It is: “I will name the grading system, grade each quadrant, state the most posterior visible structure, describe iris configuration and pigmentation, and record any PAS and indentation response.” This prevents the Shaffer-versus-Scheie reversal from becoming a documentation error.

If asked to explain the reversal, say it plainly: Shaffer moves towards a wider angle with higher grades; Scheie moves towards more closure with higher grades. Then stop. Adding uncertain degree ranges after a correct conceptual answer is a common way to lose precision.

Classic questions: give the sign, then its boundary

What is Sampaolesi’s line?

It is a pigmented line anterior to, or at the level of, Schwalbe’s line. In a viva, call it a gonioscopic sign and describe its location. Do not use it as a diagnosis by itself or claim that it proves one specific glaucoma mechanism.

What are peripheral anterior synechiae?

PAS are peripheral iris adhesions to angle structures. Describe their quadrant, extent and appearance. An answer that says only “PAS positive” omits the information an examiner can use. Avoid presenting indentation as a definitive test of every adhesion without an adequate view.

What is plateau iris configuration?

The useful examination concept is that an anteriorly positioned ciliary body can keep the peripheral iris crowded despite a relatively deep central anterior chamber. If the station asks for the sign, describe the configuration; if it asks for a mechanism, distinguish the peripheral configuration from a generic “shallow chamber” statement. Do not turn that into patient-specific laser or surgical advice.

Why do all quadrants matter?

Angle anatomy, pigmentation and pathology can be regional. A superior quadrant may not resemble an inferior quadrant. A quadrant-by-quadrant report is therefore more defensible than a single “open” or “closed” label.

A one-minute presentation

Use a format that leaves the examiner able to check every claim:

“Gonioscopy was performed with a [lens category/name if supplied] using [relevant viewing conditions]. In the [quadrant], the most posterior structure visible is [finding]. The angle is [grade] by the [Shaffer/Scheie/Spaeth] system. Trabecular pigmentation is [finding], iris configuration/insertion is [finding], and PAS are [absent/present with location and extent]. On indentation, [observed dynamic finding]. I would correlate this with the rest of the ocular assessment.”

Practise replacing bracketed words with supplied findings, not with memorised pathology. The sentence is deliberately not a diagnosis. It shows the examiner that you can state what the lens revealed and what it did not.

A 25-minute viva rehearsal

Ask a partner to change only one feature in the second run: for example, alter the most posterior visible structure in one quadrant or replace an appositional opening response with an unchanged peripheral attachment. That trains reasoning. Repeating the same “perfect” angle diagram trains recall, not viva control.

Errors to remove before the next practical

• Saying the lens “opens the angle” instead of explaining that it permits visualisation.
• Calling a mirror lens direct gonioscopy.
• Confusing visible trabecular pigmentation with angle width.
• Giving a Shaffer number without saying “Shaffer”, then using Scheie logic to explain it.
• Looking at one quadrant and reporting the whole angle.
• Using indentation as a ritual without reporting what changed.
• Turning Sampaolesi’s line, PAS or plateau iris configuration into a one-sign diagnosis.
• Offering management advice when the station has only asked for gonioscopy.

For wider revision, the glaucoma MCQs and study guide is the relevant topic hub. To work through glaucoma terminology and mechanism distinctions, use the ophthalmology glossary. If you want a product preview while planning a revision block, see sample pages of Glaucoma Exam Ready Notes. Practical station rehearsal belongs with the OSCE, Practical & Viva Voce Ready bundle. These are OphthaMCQ resources, not a substitute for supervised slit-lamp and gonioscopy training.

Sources

1. European Glaucoma Society Guidelines, 5th edition — angle-assessment and glaucoma context; checked 18 August 2026.
2. AAO EyeWiki: Gonioscopy — optical principle, lens categories, angle structures, indentation and grading-system context; checked 18 August 2026.
3. NCBI Bookshelf: Gonioscopy — clinical context and limits of isolated gonioscopic interpretation; checked 18 August 2026.