Pupillary and visual dysfunction in progressive supranuclear palsy (PSP) extends beyond the characteristic supranuclear gaze palsy to encompass a range of ocular abnormalities including pupillary size and reactivity changes, contrast sensitivity deficits, color vision abnormalities, and ocular surface disease. These features provide insights into the underlying neuropathology and contribute to the differential diagnosis from other parkinsonian syndromes.
¶ Prevalence and Types
Pupillary abnormalities occur in the majority of PSP patients:
| Abnormality Type |
Prevalence |
Clinical Significance |
| Miosis (small pupils) |
40-55% |
Moderate |
| Reduced light reactivity |
35-50% |
High |
| Anisocoria (asymmetric pupils) |
15-25% |
Moderate |
| Abnormal convergence |
30-40% |
Moderate |
| Tonic pupil (rare) |
5-10% |
Low |
Pupillary abnormalities in PSP stem from:
- Edinger-Westphal nucleus: Tau pathology in parasympathetic output
- Pretectal area: Light reflex pathway involvement
- Superior colliculus: Visual integration center
- Hypothalamus: Autonomic regulation
- Ciliary ganglion: Post-ganglionic involvement
The autonomic nervous system plays a key role:
- Sympathetic dysfunction: Reduced pupillary dilation
- Parasympathetic impairment: Reduced constriction
- Dysautonomia correlation: Orthostatic hypotension link
- Reduced constriction amplitude: <2mm in bright light
- Prolonged constriction latency: >300ms delay
- Impaired dilation: Slow or incomplete
- Light-near dissociation: Present in some cases
- Convergence impairment: Reduced miosis with accommodation
- Accommodative insufficiency: Difficulty with near focus
- Pseudo-Argyll Robertson: Light-near dissociation
Contrast sensitivity impairment is common in PSP:
- Spatial frequencies: Low and mid-frequency loss predominates
- Severity: Moderate (1-2 log units below normal)
- Progression: Generally stable over time
- Correlation: With disease severity
- Retinal ganglion cell loss: Variable involvement
- Optic nerve involvement: Axonal loss in some cases
- Cortical processing: Post-retinal deficits
- Attention: Visuospatial attention contribution
Standardized assessments include:
- Pelli-Robson chart: Low-contrast letter recognition
- CSV-1000: Spatial frequency specific
- Mars letter contrast sensitivity test: Alternative method
- Functional vision: Real-world impact assessment
¶ Prevalence and Pattern
- Overall prevalence: 40-60% of PSP patients
- Type: Mild to moderate deficits
- Pattern: Blue-yellow axis involvement more common
- Severity: Usually not severe enough to meet color blindness criteria
- Retinal involvement: Variable ganglion cell loss
- Optic pathway: Post-retinal processing deficits
- Cortical color centers: Ventral temporal involvement
- Tau pathology: Direct involvement of color processing regions
- Ishihara plates: Screening for red-green deficits
- Farnsworth-Munsell D-15: Detailed axis assessment
- Lanthony desaturated panel: Sensitive to mild deficits
¶ Prevalence and Impact
Ocular surface disease is highly prevalent in PSP:
| Condition |
Prevalence |
Impact |
| Dry eye disease |
50-70% |
Moderate-severe |
| Blepharitis |
30-40% |
Mild-moderate |
| Lagophthalmos |
20-30% |
Moderate |
| Conjunctival injection |
40-50% |
Mild |
- Reduced blink rate: From 15-20/min to <10/min in PSP
- Incomplete blink: 70% of blinks incomplete
- Facial masking: Reduced protective blinks
- Eye closure: Incomplete during sleep
- Reduced tear production: Autonomic tear gland dysfunction
- Abnormal tear film composition: Altered mucus and lipid layers
- Meibomian gland dysfunction: Altered secretion
Symptoms include:
- Burning sensation: 60-70%
- Gritty feeling: 50-60%
- Redness: 40-50%
- Blurred vision: Variable
- Excessive tearing: Compensatory (paradoxical)
- Artificial tears: Preserved and preservative-free options
- Warm compresses: For meibomian gland dysfunction
- Eyelid hygiene: Regular cleaning
- Humidifier: Environmental modification
- Anti-inflammatory drops: Cyclosporine, lifitegrast
- Punctal plugs: For severe dry eye
- Antibiotics: For blepharitis (topical)
- Tetracycline derivatives: Oral for meibomian disease
- Tarsorrhaphy: Partial for lagophthalmos
- Lateral canthoplasty: For exposure
- Punctal occlusion: Permanent
¶ Pattern and Prevalence
- Constricted visual fields: 30-40%
- Central scotomas: 10-15%
- Altitudinal defects: Rare
- Diffuse depression: Common
- Optic nerve involvement: Variable axonal loss
- Chiasmal involvement: Rare
- Cortical loss: Post-chiasmal contributions
- Attention deficits: Functional visual field restriction
¶ Reading and Visual Processing
PSP patients commonly experience:
- Slow reading speed: 40-50% slower than controls
- Line loss: Difficulty maintaining place
- Saccadic intrusions: Interruption during reading
- Visual fatigue: Rapid onset of exhaustion
- Reduced span: Fewer items in focus
- Slow shifts: Prolonged saccade latencies
- Neglect-like features: Spatial attention deficits
- Simultanagnosia: In advanced cases
| Feature |
PSP |
PD |
| Blink rate |
Markedly reduced |
Moderately reduced |
| Dry eye |
Common |
Common |
| Contrast sensitivity |
Moderate deficit |
Mild deficit |
| Color vision |
Variable |
Variable |
| Pupillary size |
Small (miosis) |
Normal |
| Feature |
PSP |
CBS |
| Pupillary abnormalities |
Moderate |
Variable |
| Ocular surface disease |
Common |
Common |
| Visual field defects |
Uncommon |
More common |
| Reading difficulties |
Prominent |
Variable |
| Feature |
PSP |
MSA |
| Pupillary abnormalities |
Moderate-severe |
Variable |
| Dry eye |
Common |
Less common |
| Visual processing |
Deficits |
Relatively preserved |
Ocular findings assist in:
- MSA differentiation: Preserved pupillary reactions vs. PSP
- PD differentiation: More severe olfactory loss vs. pupillary changes in PSP
- CBS overlap: Variable presentations
Research directions include:
- OCT measures: Retinal nerve fiber layer thickness
- Pupillometry: Quantitative light response
- Blink rate: Automated measurement
- Tear film analysis: Biomarker discovery
Effective management requires:
- Neurology: Overall disease management
- Ophthalmology: Specialized assessment
- Optometry: Low vision services
- Occupational therapy: Environmental adaptations
- Lighting optimization: Enhanced contrast
- Magnification: Low vision devices
- Audio description: Complementary information
- Simplified materials: Reduced visual demands
- Adaptive optics: Retinal cellular imaging
- Electrophysiology: Pattern ERG, VEP
- Biomarkers: Tear and conjunctival markers
- Therapeutic trials: Ocular endpoints
- Progression markers: Ocular measures over time
- Pathological correlation: Tau burden relationship
- Treatment response: Outcome measures
Recent longitudinal studies have refined our understanding of pupillary progression in PSP:
- Progressive constriction: Pupillary diameter decreases by approximately 0.3mm per year
- Light reflex decline: Constriction amplitude declines faster than dilation
- Prognostic value: Baseline pupillary abnormalities predict 2-year progression
Optical coherence tomography angiography has revealed new insights in PSP:
- Microvascular changes: Reduced peripapillary capillary density correlates with disease severity
- Nerve fiber layer: thinning correlates with motor progression
- Choroidal changes: Altered choroidal thickness in PSP compared to PD
Machine learning approaches have improved visual assessment in PSP:
- Automated perimetry: AI-assisted visual field testing improves reliability
- Pattern classification: Deep learning distinguishes PSP from PD visual patterns
- Progression modeling: Individualized progression prediction from baseline measures
Novel research has identified tear film biomarkers in PSP:
- Inflammatory markers: Elevated IL-6 and TNF-alpha in PSP tears
- Protein profiling: Distinct tear protein patterns from PD and controls
- Diagnostic potential: Tear biomarker panel shows 75% sensitivity for PSP
Spectral-domain OCT studies have demonstrated specific patterns of retinal layer thinning in PSP:
- RNFL thinning: 20-30% reduction compared to controls, most pronounced in the superior and nasal sectors
- GCC loss: Ganglion cell complex thinning parallels cortical tau burden
- Inner retinal layers: Correlation with disease duration and severity