Pupil Examination
Introduction:
The examination of the pupil is a crucial part of clinical optometry and ophthalmology. Pupils provide vital information not only about ocular health but also about the integrity of the visual pathway, autonomic nervous system, and even systemic or neurological conditions. A careful assessment of pupil size, shape, symmetry, and light and near responses can reveal disorders such as optic nerve disease, third nerve palsy, Horner’s syndrome, or pharmacological influences. Because pupil examination is quick, non-invasive, and highly informative, it is performed routinely in all comprehensive eye examinations.
Anatomy of the Pupil
The pupil is the central circular aperture of the iris, typically 2–4 mm in diameter under normal lighting. Its function is to regulate the amount of light entering the eye, similar to a camera aperture. The size of the pupil depends on the balance between two muscles within the iris:
- Sphincter pupillae: Circular muscle fibers innervated by the parasympathetic system (via oculomotor nerve, Edinger–Westphal nucleus). Contraction → pupil constriction (miosis).
- Dilator pupillae: Radial fibers innervated by the sympathetic system (via hypothalamus, cervical sympathetic chain, superior cervical ganglion). Contraction → pupil dilation (mydriasis).
Normal Pupil Characteristics
- Size: 2–4 mm in normal illumination; larger in dim light, smaller in bright light.
- Shape: Round and regular.
- Position: Central in the iris.
- Equality: Pupils are normally equal in size (isocoria), with difference not exceeding 0.5 mm.
Methods of Pupil Examination
1. Inspection
Observe both pupils in normal room light. Assess size, equality, shape, and position. Any inequality (>1 mm difference) is clinically significant and termed anisocoria.
2. Light Reflex
The light reflex is the constriction of the pupil in response to illumination. Two types are assessed:
- Direct light reflex: Constriction of the illuminated pupil.
- Consensual light reflex: Simultaneous constriction of the fellow pupil due to decussation of fibers at the pretectal nucleus.
Procedure: Use a penlight. Shine light obliquely into one eye while observing constriction. Repeat for the other eye.
3. Near Reflex (Accommodation Reflex)
When shifting gaze from distance to a near target, pupils constrict as part of the accommodation triad (accommodation, convergence, miosis).
Procedure: Ask patient to look at a distant object, then quickly shift gaze to a near target (about 15 cm). Observe pupil constriction.
4. Swinging Flashlight Test
This test detects Relative Afferent Pupillary Defect (RAPD), also called the Marcus Gunn pupil.
- Darken the room slightly.
- Ask patient to fixate on a distant target.
- Shine light on one eye for 2–3 seconds, then quickly swing to the other eye.
- Observe pupil reaction. In a normal eye, both pupils constrict equally. In RAPD, pupils dilate when light is shone on the affected eye due to defective afferent signal.
5. Pharmacological Testing
Used in special cases to differentiate causes of anisocoria or to confirm diagnoses such as Horner’s syndrome or Adie’s tonic pupil. Common agents include:
- Pilocarpine (low concentration): Constriction indicates Adie’s tonic pupil.
- Cocaine or Apraclonidine: Used to confirm Horner’s syndrome.
Abnormal Pupil Reactions
1. Anisocoria
Unequal pupil sizes. Causes include physiological anisocoria, Horner’s syndrome, Adie’s tonic pupil, pharmacological agents, or third nerve palsy.
2. Argyll Robertson Pupil
Small, irregular pupils that do not react to light but constrict on near response (“light-near dissociation”). Classically seen in neurosyphilis, but also in diabetes and multiple sclerosis.
3. Adie’s Tonic Pupil
Usually unilateral, dilated pupil with sluggish or absent reaction to light, but constriction on near effort. More common in young women. Supersensitive to dilute pilocarpine.
4. Horner’s Syndrome
Characterized by triad: miosis, ptosis, and anhidrosis due to disruption of sympathetic pathway. Pharmacological testing helps confirm diagnosis.
5. Third Nerve Palsy
Causes dilated, non-reactive pupil often associated with ptosis and ophthalmoplegia.
6. RAPD (Marcus Gunn Pupil)
A hallmark of optic nerve or severe retinal disease. Detected by swinging flashlight test.
Clinical Importance of Pupil Examination
- Neurological: Detects optic nerve disease, brainstem lesions, increased intracranial pressure.
- Ophthalmic: Reveals glaucoma, retinal detachment, ischemic optic neuropathy.
- Systemic: Provides clues to diabetes, syphilis, multiple sclerosis, tumors.
- Medicolegal: Baseline pupil examination is essential before instilling mydriatics, and in trauma or medico-legal cases.
Advantages
- Simple and quick to perform.
- Does not require expensive equipment.
- Provides critical diagnostic information about both ocular and systemic disease.
Limitations
- Requires patient cooperation and attention.
- Interpretation can be affected by ambient lighting.
- Subtle defects may be missed without experience.
- Pharmacological testing may not always be feasible in outpatient settings.
Maddox Rod Test
Introduction:
The Maddox rod test is a well-established clinical procedure used in binocular vision assessment to detect and measure heterophoria (latent deviations) and heterotropia (manifest deviations). It is a dissociation test, which means it breaks the normal fusion mechanism of the eyes, allowing hidden deviations to become manifest. By converting a point light source into a line image through a series of cylindrical rods, the test makes it easier to detect misalignment between the two eyes.
The Maddox rod test is especially useful because it is subjective, simple, and quick, and it allows both detection and quantification of phorias. It is performed routinely in orthoptic clinics, pediatric optometry, and strabismus evaluation. Unlike the cover test, which is more objective, the Maddox rod relies on patient response, making it particularly valuable for cooperative adults and older children who can give reliable feedback.
History
The test was developed by the English ophthalmologist Ernest E. Maddox in the late 19th century. His contribution to binocular vision testing also includes the Maddox wing and Maddox cross, all of which are still used in clinical practice today.
Principle of the Maddox Rod Test
A Maddox rod consists of a series of parallel red or clear glass/plastic cylindrical rods mounted in a frame. When a point source of light is viewed through the rod, it is transformed into a line image oriented perpendicular to the axis of the cylinders.
Example: If the rods are placed horizontally, the patient will see a vertical red line. If placed vertically, the patient sees a horizontal red line.
By dissociating the images of the two eyes, the fusion mechanism is disrupted, and any underlying deviation (phoria or tropia) is revealed as a displacement between the light and the line.
Objectives of the Test
- To detect the presence of heterophoria or heterotropia.
- To identify the type of deviation (eso, exo, hyper, hypo).
- To measure the magnitude of deviation using prisms.
- To assess binocular alignment in cooperative patients.
- To complement cover test and other binocular vision investigations.
Types of Maddox Test
- Maddox Rod Test: Used for distance vision assessment, usually at 6 m.
- Maddox Wing Test: Used for near vision assessment (33 cm), particularly useful in adults for horizontal and vertical phorias.
- Maddox Cross Test: Utilized in some clinics for more detailed alignment evaluation.
Procedure of Maddox Rod Test
- Seat the patient at a distance of 6 meters from a point light source.
- Place the Maddox rod before one eye (commonly the right eye) while the other eye views the light directly.
- Ensure correct orientation of rods:
- Horizontal rods → patient perceives vertical red line (used for detecting horizontal deviations).
- Vertical rods → patient perceives horizontal red line (used for detecting vertical deviations).
- Ask the patient to describe the relative position of the red line and the white light.
- If misalignment is reported, introduce prisms of increasing power before the eye until the line passes through the light (neutralization point).
- Record the prism power and direction, which indicate the magnitude and type of deviation.
Interpretation
Horizontal Deviations
- Exophoria/Exotropia: If the line appears to the left of the light (when Maddox rod is before right eye), it indicates outward deviation.
- Esophoria/Esotropia: If the line appears to the right of the light, it indicates inward deviation.
Vertical Deviations
- Right Hyperphoria/Hypertropia: If the line appears below the light, it means the right eye is deviated upward.
- Right Hypophoria/Hypotropia: If the line appears above the light, it means the right eye is deviated downward.
Torsional Deviations
With specially designed double Maddox rods (placed in both eyes), torsional misalignments can be assessed. If the patient reports tilted lines, it indicates cyclophoria.
Recording Results
Results are recorded in terms of type and magnitude of deviation:
- Horizontal deviation: Prism diopters base in (for exo) or base out (for eso).
- Vertical deviation: Prism diopters base up or base down.
- Example: 6Δ BO (Base Out) indicates 6 prism diopters of esophoria.
Clinical Applications
- Diagnosis of phorias in patients with asthenopic symptoms.
- Detection of decompensated phorias leading to intermittent tropias.
- Assessment of vertical deviations such as hyperphoria.
- Monitoring changes in ocular alignment over time or after treatment.
- Complementary test in strabismus and binocular vision assessment.
Advantages
- Simple and quick to perform.
- Requires minimal equipment (just a Maddox rod and prisms).
- Highly sensitive for detecting latent deviations not revealed by cover test.
- Can measure both horizontal and vertical deviations.
Limitations
- Subjective test, requires cooperative patients who can describe perceptions.
- Not suitable for very young children or non-verbal patients.
- Cannot distinguish between phoria and tropia unless used with cover test.
- Accuracy depends on patient’s understanding and response.
Comparison with Other Tests
- Cover Test: Objective, detects both phorias and tropias, but does not quantify as precisely.
- Maddox Rod: Subjective, detects latent deviations, provides measurement with prisms.
- Prism Cover Test: Gold standard for cooperative patients; Maddox rod complements this by dissociating fusion more effectively.
Special Variations
- Maddox Wing: Performed at near (33 cm) for measuring near phorias, especially horizontal and vertical.
- Double Maddox Rod: Used for assessment of cyclophoria (torsional deviations), especially in patients with cyclovertical muscle palsies.
Clinical Importance
The Maddox rod test is extremely important in orthoptics and binocular vision evaluation. Many patients present with nonspecific symptoms like headache, eye strain, or blurred vision after near work. These may be due to uncorrected phorias that are compensated under normal conditions but become symptomatic under stress. By breaking fusion, the Maddox rod test reveals such deviations and guides optometrists in prescribing prisms, vision therapy, or orthoptic exercises. It also plays a crucial role in diagnosing vertical deviations, which are often missed in routine cover tests.
Van Herrick Test
Introduction:
The Van Herrick test is a quick, simple, and non-contact clinical procedure used to estimate the anterior chamber depth (ACD) of the eye. It is performed with a slit lamp biomicroscope and is particularly important in screening patients for angle closure glaucoma. By comparing the peripheral anterior chamber depth to the corneal thickness, the examiner can classify the anterior chamber as deep, borderline, or shallow.
The test is highly useful in routine practice because it requires no special equipment beyond the slit lamp, is non-invasive, and provides immediate results. Although not as precise as gonioscopy, it serves as an excellent screening test to identify patients at risk of angle closure who may need further evaluation.
Anatomical Background
The anterior chamber is the fluid-filled space between the cornea and iris. Its depth varies between individuals but typically ranges from 2.5–4.0 mm centrally. The peripheral anterior chamber depth is of particular clinical importance, as narrow angles here predispose to angle closure glaucoma.
Normal anatomy:
- Central anterior chamber depth ~3.0 mm.
- Peripheral depth gradually decreases towards the angle.
- Risk of closure increases if iris is anteriorly positioned or lens thickness is increased.
Principle of the Test
The Van Herrick test compares the peripheral anterior chamber depth to the thickness of the cornea at the limbus using an optical section of light. A narrow slit beam is directed at the limbus, and the examiner visually compares the dark space (anterior chamber) to the bright section of the cornea. The ratio of chamber depth to corneal thickness is then graded.
Objectives
- To estimate peripheral anterior chamber depth.
- To screen patients at risk for primary angle closure glaucoma.
- To guide decisions for gonioscopy or prophylactic laser iridotomy.
- To provide a baseline measurement in routine slit lamp examinations.
Equipment Required
- Slit lamp biomicroscope.
- Light source capable of producing a narrow slit beam (1 mm).
- Patient seated comfortably with chin and forehead positioned properly.
Procedure of Van Herrick Test
- Seat the patient at the slit lamp with chin on chin rest and forehead against bar.
- Adjust illumination to a narrow, bright slit beam (about 1 mm width, 60° angle).
- Position the slit beam at the temporal limbus (can also be done nasally for confirmation).
- Direct the beam perpendicular to the corneal surface at 60° to the viewing system.
- Observe the bright optical section of the cornea and the adjacent dark space representing anterior chamber depth.
- Compare the width of the dark space (ACD) to the thickness of the cornea at that point.
- Classify according to the Van Herrick grading system.
Van Herrick Grading System
The test uses a grading scale from 0 to 4:
- Grade 4: ACD ≥ corneal thickness → Wide open angle. Very low risk of closure.
- Grade 3: ACD = ½ corneal thickness → Open angle. Low risk.
- Grade 2: ACD = ¼ corneal thickness → Narrow angle. Moderate risk of closure.
- Grade 1: ACD < ¼ corneal thickness → Extremely narrow. High risk of closure.
- Grade 0: No visible space between cornea and iris → Closed angle.
Interpretation
- Grades 3 and 4: Safe, open angles, no immediate risk.
- Grade 2: Borderline. Needs gonioscopy for further evaluation.
- Grade 1: Narrow. Strong risk of angle closure; prophylactic laser iridotomy often considered.
- Grade 0: Closed angle. Requires urgent ophthalmic intervention.
Clinical Applications
- Screening for primary angle closure glaucoma in routine practice.
- Pre-operative assessment before dilating pupils (to avoid angle closure attack).
- Baseline anterior chamber assessment in patients with hyperopia, shallow orbits, or thick lenses.
- Community eye care programs where gonioscopy is not feasible.
Advantages of Van Herrick Test
- Simple and rapid technique.
- Non-contact, safe, and patient-friendly.
- Requires no additional instruments beyond slit lamp.
- Effective as a screening tool to identify at-risk patients.
Limitations
- Provides only an estimate of anterior chamber depth, not exact measurement.
- Accuracy depends on examiner’s skill and experience.
- Does not visualize the angle directly (gonioscopy is gold standard).
- May be affected by corneal opacity, poor fixation, or patient cooperation.
- Cannot assess peripheral anterior synechiae or angle structures.
Comparison with Other Methods
- Gonioscopy: Gold standard for angle evaluation. Direct visualization of trabecular meshwork, scleral spur, ciliary body band. More accurate but requires contact lens.
- Anterior Segment OCT (AS-OCT): Provides high-resolution imaging of angle. Expensive and not widely available.
- Ultrasound Biomicroscopy: Provides detailed anterior chamber imaging. Requires specialized equipment.
- Van Herrick: Simple, quick, screening tool. Best for routine practice and community screening.
Clinical Importance
The Van Herrick test is invaluable in identifying patients at risk for primary angle closure glaucoma, a potentially blinding condition if untreated. Since dilation of pupils can precipitate acute angle closure in predisposed individuals, Van Herrick is essential before instilling mydriatics.
It also plays a key role in:
- Pre-operative cataract evaluation: Shallow chambers may indicate risk of complications during surgery.
- Screening hypermetropes: They tend to have shorter eyes and shallower chambers.
- Community eye screening: Rapid identification of glaucoma suspects where gonioscopy is impractical.
External Examination of the Eye and Lid Eversion
Introduction:
The external examination of the eye is the first step in a detailed ocular evaluation. It involves systematic inspection of the adnexa, eyelids, conjunctiva, sclera, cornea, and periocular tissues. The goal is to detect abnormalities that can provide diagnostic clues or influence further clinical management. Since many systemic and ocular diseases manifest externally, careful observation is critical.
Lid eversion is an integral part of external examination. It allows visualization of the palpebral conjunctiva, which cannot otherwise be inspected. This procedure is essential for detecting foreign bodies, papillae, follicles, and other conjunctival abnormalities. Together, external examination and lid eversion provide essential diagnostic information, often before any advanced tools like slit-lamp biomicroscopy are used.
Objectives
- To assess adnexal structures (eyelids, lashes, lacrimal apparatus).
- To identify ocular surface abnormalities.
- To detect signs of trauma, infection, allergy, or systemic disease.
- To inspect palpebral conjunctiva for foreign bodies, follicles, papillae, or lesions.
- To guide further investigations and treatment planning.
Components of External Eye Examination
A systematic approach is followed, beginning from periocular tissues and moving inward:
1. General Inspection
Observe the patient’s face and orbital symmetry. Look for signs such as proptosis, enophthalmos, lid swelling, facial palsy, or systemic abnormalities (thyroid eye disease, trauma scars).
2. Eyelids
- Position: Check for ptosis, lid retraction, entropion, or ectropion.
- Movement: Ask patient to open and close eyes to assess levator and orbicularis function.
- Margins: Look for crusting, trichiasis, blepharitis, or notching.
- Lashes: Check alignment, loss (madarosis), or misdirection.
3. Conjunctiva
- Bulbar conjunctiva: Look for hyperemia, chemosis, or subconjunctival hemorrhage.
- Palpebral conjunctiva: Requires lid eversion to inspect for papillae, follicles, concretions, or foreign bodies.
4. Sclera
Assess color (normal white, yellow in jaundice, bluish in connective tissue disorders, red in inflammation). Check for scleritis, episcleritis, or thinning.
5. Cornea
With oblique illumination, inspect clarity, smoothness, and presence of scars, opacities, or vascularization.
6. Lacrimal System
Check for swelling, discharge, or regurgitation on pressure (ROPLAS test). Inspect puncta for patency and position.
Procedure of External Examination
- Seat patient comfortably in well-illuminated environment.
- Begin with gross inspection of face and adnexa.
- Move systematically to eyelids, conjunctiva, sclera, and cornea.
- Use oblique torchlight or slit lamp for detailed inspection.
- Note abnormalities such as redness, swelling, asymmetry, or lesions.
Common Abnormal Findings
- Eyelids: Ptosis, lagophthalmos, blepharitis, stye, chalazion, entropion, ectropion.
- Conjunctiva: Conjunctivitis, follicles, papillae, pterygium, pinguecula.
- Sclera: Episcleritis (localized redness), scleritis (deep, painful congestion).
- Cornea: Opacities, keratitis, corneal ulcer, arcus senilis.
- Lacrimal system: Dacryocystitis, nasolacrimal duct obstruction.
Lid Eversion
Purpose
- To inspect palpebral conjunctiva.
- To detect and remove foreign bodies.
- To assess allergic conditions (giant papillary conjunctivitis).
- To observe follicles in viral or chlamydial infections.
Types of Lid Eversion
- Simple eversion: For upper tarsal conjunctiva.
- Double eversion: For superior fornix examination, often using a Desmarres retractor or glass rod.
Procedure of Simple Upper Lid Eversion
- Ask patient to look down (to relax levator muscle).
- Grasp eyelashes of upper lid gently with thumb and forefinger.
- Place a cotton-tipped applicator or glass rod horizontally across upper tarsus.
- Flip lid upward over the applicator with gentle pressure.
- Hold lid against orbital rim while examining palpebral conjunctiva.
Procedure of Double Eversion
- Perform simple eversion first.
- Then use a retractor or glass rod to further lift everted lid, exposing superior fornix.
- Useful for detecting deeply lodged foreign bodies or trachomatous follicles.
Findings on Lid Eversion
- Foreign bodies: Dust, iron particles, contact lens fragments.
- Papillae: In allergic conjunctivitis, giant papillary conjunctivitis (contact lens wearers).
- Follicles: Viral conjunctivitis, trachoma, chlamydial infections.
- Concretions: Yellow-white spots in elderly or chronic conjunctivitis.
- Tarsal abnormalities: Scarring in trachoma, tumors, inclusion cysts.
Clinical Applications
- Detecting and removing ocular foreign bodies.
- Diagnosis of allergic conjunctivitis and giant papillary conjunctivitis.
- Identifying trachoma and other infectious conjunctivitis.
- Monitoring chronic conjunctival inflammation and scarring.
- Screening for systemic diseases with ocular manifestations.
Advantages
- Simple and quick.
- Requires minimal equipment.
- Can be done in outpatient and emergency settings.
- Provides essential information often missed on surface inspection.
Limitations
- Requires patient cooperation.
- May cause discomfort or reflex blinking.
- Risk of corneal abrasion if performed carelessly.
- Deep lesions or posterior fornix abnormalities may still require slit lamp.
Precautions
- Always wash hands before and after procedure.
- Avoid undue pressure on the globe, especially in trauma cases.
- Be gentle to minimize patient discomfort.
- Use topical anesthetic drops if necessary in sensitive patients.
