Dr. Davinder Sidhu

Dr. Davinder Sidhu Award-Winning Optometrist in British Columbia 🇨🇦

04/22/2026

Your brain doesn’t detect color directly.

It builds it from signals coming from the eye.

Humans are trichromats, meaning we rely on three types of cone photoreceptors in the retina to detect color.

Each cone type is sensitive to different ranges of light wavelengths.

When light enters the eye:

• The retina detects the wavelengths
• Three cone systems respond differently
• The brain compares those signals

From that comparison, the brain constructs the color you perceive.

This is why humans can distinguish millions of colors, even though the retina relies on just three types of color-sensitive cells.

Vision is not simply detection — it is interpretation by the brain.

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Night driving is a high-demand visual task. It requires rapid detection of low-contrast targets, accurate depth and moti...
04/20/2026

Night driving is a high-demand visual task. It requires rapid detection of low-contrast targets, accurate depth and motion judgments, and continuous adaptation to glare. With age, several predictable optical and neural changes can make these demands feel disproportionately harder, even when standard visual acuity and your prescription appear stable.

Three mechanisms contribute most commonly:

• Pupil size decreases in low light. A smaller pupil allows less light into the eye, reducing retinal illumination and making dark scenes appear dimmer.
• Light scatter increases. Age-related changes in the ocular media can increase forward scatter, which amplifies glare from oncoming headlights and reduces image clarity.
• Contrast sensitivity declines. Reduced ability to detect subtle differences between objects and background makes lane markings, pedestrians, and hazards harder to see until they are closer.

Clinically, this is why “20/20” is not a complete night-driving metric. Testing glare disability, contrast sensitivity, and ocular media clarity can reveal limitations that a standard chart does not capture. If you avoid night driving, feel delayed to recognize hazards, or notice halos and glare, it is worth discussing targeted testing at your next exam.

PMIDs: 10785997, 15615747

04/19/2026

Human color vision is based on trichromacy, meaning we primarily rely on three classes of cone photoreceptors. These cones are often described by their peak sensitivity to shorter, medium, and longer wavelength ranges. Color perception emerges from how strongly each cone class responds and how the visual system compares those responses.

Color is not detected by a single “color receptor.” Instead, it is computed through relative patterns of activation across cone types, then processed through retinal and cortical pathways that support discrimination, contrast, and stability across lighting environments.

Trichromatic color vision depends on:

• Three cone classes with overlapping spectral sensitivities.
• Comparative coding rather than absolute wavelength detection.
• Opponent processing pathways that enhance differentiation.
• Cortical integration that accounts for context and illumination.

This is why color perception can shift with lighting conditions and why some retinal or neurological conditions can change color discrimination even when visual acuity is unchanged. The eye captures the signal, but the brain constructs the percept.

If you notice reduced color vibrancy, difficulty distinguishing shades, or changes in contrast sensitivity, bring it up at your next comprehensive exam.

PMID: 24531448

An eyelid twitch can feel strange or annoying, but in most cases it is harmless.The medical term is eyelid myokymia, whi...
04/17/2026

An eyelid twitch can feel strange or annoying, but in most cases it is harmless.

The medical term is eyelid myokymia, which means small, involuntary muscle twitches in the eyelid.

These twitches are usually:

• In one eye
• On and off
• Temporary

The most common causes are related to fatigue and stress on the nervous system.

Common triggers include:

• Stress
• Lack of sleep
• Too much caffeine
• Long hours on screens or close work

When these factors improve, the twitch usually goes away on its own.

Simple things that may help include:

• Getting more sleep
• Reducing caffeine
• Taking breaks from screens
• Managing stress

However, you should consider seeing an eye doctor if:

• The twitch lasts more than a few weeks
• It starts happening in both eyes
• Your eyelid fully closes during the spasms
• The twitch spreads to other parts of your face

In most cases, eyelid twitches are temporary and harmless, but persistent symptoms are worth having checked.

PMIDs: 30190479, 35013446 👁️

04/16/2026

Glaucoma is not simply “high eye pressure.” It is a chronic, progressive optic neuropathy characterized by structural damage to the optic nerve and corresponding visual field loss.

Intraocular pressure is the most significant modifiable risk factor, but glaucoma can occur even when pressure falls within statistically normal ranges. The underlying issue is vulnerability of the retinal ganglion cell axons as they exit the eye through the optic nerve head.

Why it is called the “silent thief”:

• Early stages are typically asymptomatic.
• Peripheral vision declines gradually.
• Central vision often remains clear until late stages.
• Damage is irreversible once it occurs.

Because early visual acuity may remain normal, patients often do not notice functional loss. By the time central vision is affected, significant optic nerve damage has already occurred.

Comprehensive eye examinations evaluate more than clarity. They assess optic nerve structure, retinal nerve fiber layer thickness, intraocular pressure, and visual field integrity. Early detection and consistent monitoring are critical for preserving functional vision.

If you have a family history of glaucoma, elevated eye pressure, or are over age 40, regular screening is essential.

PMID: 32031922

Visual fatigue is frequently dismissed as minor discomfort. In reality, sustained eye strain can influence broader cogni...
04/14/2026

Visual fatigue is frequently dismissed as minor discomfort. In reality, sustained eye strain can influence broader cognitive performance. The visual system is tightly integrated with attention networks, working memory, and executive control. When visual demand exceeds capacity, the resulting strain can spill over into measurable cognitive slowing.

Prolonged near tasks require continuous accommodation, binocular coordination, and stable tear film function. Over time, this can lead to symptoms such as:

• Fluctuating blur after screen use.
• Slower refocusing between distances.
• Forehead or periocular headaches.
• Increased light sensitivity or glare discomfort.

When visual effort increases, attentional resources are diverted toward maintaining clarity and alignment. This redistribution of neural resources can contribute to:

• Reduced sustained focus.
• Slower task completion.
• Increased susceptibility to distraction.
• Higher perceived mental fatigue.

Clinically, complaints of “brain fog” during screen-heavy days may reflect both cognitive load and unaddressed visual demand. Evaluating accommodative function, binocular coordination, and ocular surface stability can be essential when productivity declines alongside visual discomfort.

Improving ergonomics, managing near work duration, and addressing underlying visual inefficiencies can support both visual comfort and cognitive performance.

If your focus drops after prolonged screen time, discuss visual fatigue—not just time management—at your next comprehensive exam.

PMIDs: 30190479, 31262502

04/14/2026

Visual memory isn’t stronger by chance.
It reflects how the brain encodes information.

Research consistently shows that people remember images more accurately than words alone. This is known as the picture superiority effect.

Why does this happen?

Images are processed through multiple neural pathways at once.
They activate perceptual systems, spatial networks, and semantic associations simultaneously, which creates richer encoding in memory.

Visual memory benefits from:

• Dual coding through both visual and conceptual systems
• Stronger activation of associative cortical networks
• More elaborate encoding compared to abstract text
• Greater resistance to forgetting over time

By comparison, verbal memory relies more heavily on sequential language processing.

Images provide instant structure, spatial context, and relationships, which makes retrieval easier for the brain.

Clinically, this matters.

Visual presentation of information can improve learning in patient education, rehabilitation, and individuals with attention or language-processing challenges.

It reinforces an important principle:

Vision is not just about seeing clearly.
It is deeply connected to memory, cognition, and executive function.

PMID: 16338937 🧠👁️

Mobile internet makes information frictionless.It also makes distraction effortless.A randomized field experiment found ...
04/11/2026

Mobile internet makes information frictionless.

It also makes distraction effortless.

A randomized field experiment found that blocking mobile internet for two weeks improved sustained attention and subjective well-being.

Why might that happen?

When mobile data is unavailable:

• Interruptions decrease
• Task switching drops
• Your brain doesn’t have to constantly “reset” to refocus

And fewer switches help attention stay steadier throughout the day.

A practical “digital detox light” approach could look like this:

• Turn off mobile data during work hours (Mon–Fri)
• Use Wi-Fi only on your work device
• Set specific windows to check messages instead of reacting instantly

This isn’t about eliminating technology.

It’s about protecting focused time by reducing the most common source of interruptions.
Try this simple experiment:

Turn off mobile data 9–12 and 1–4 during the workweek, keep Wi-Fi limited to your work device, and notice whether your focus and mental fatigue change.

PMID: 39967678 🧠📱

04/11/2026

Color perception feels immediate and objective. In reality, it is a neural construction.

The retina contains photoreceptors that respond to specific wavelengths of light. These signals travel through the optic nerve to the visual cortex, where higher-order processing integrates context, lighting conditions, memory, and surrounding contrast. What you experience as “color” is the brain’s interpretation of incoming signals, not a direct recording of physical reality.

Color perception depends on:
• Cone photoreceptor activation patterns.
• Opponent processing pathways.
• Cortical integration in visual association areas.
• Contextual modulation and prior visual experience.

This explains why the same object can appear different under varying illumination or why optical illusions can shift perceived hue. The brain continuously adjusts color interpretation to maintain perceptual stability.

Clinically, this distinction matters. Neurological changes, retinal disease, or cortical dysfunction can alter color perception even when visual acuity remains intact. Color is a brain-based percept, not merely an eye-based measurement.

If you notice changes in color vibrancy, contrast, or differentiation, it warrants evaluation beyond a standard acuity test.

PMID: 24531448

It is intuitive to think of vision as a recording process. Light enters the eye, the retina captures it, and the brain “...
04/08/2026

It is intuitive to think of vision as a recording process. Light enters the eye, the retina captures it, and the brain “sees” it. Modern neuroscience suggests a more dynamic model. Vision operates as a predictive system.

The brain continuously generates expectations about the environment based on prior experience. Incoming retinal signals are compared against those predictions. When the prediction matches the input, perception feels stable and effortless. When there is a mismatch, the brain generates an error signal and updates its model.

This predictive framework explains several phenomena:

• Why context alters color and brightness perception.
• Why ambiguous images can flip between interpretations.
• Why we can rapidly recognize objects in cluttered scenes.
• Why unexpected stimuli capture attention so quickly.

Perception, therefore, is not purely bottom-up. It reflects an interaction between sensory data and top-down inference. The retina provides input, but the cortex constructs meaning through comparison, weighting, and updating.

Clinically, this matters because stress, fatigue, neurological injury, and attentional load can alter predictive balance. When the system is strained, patients may report visual overwhelm, slowed processing, or difficulty filtering visual information even when ocular structures are healthy.

Vision is an active brain process. If your visual world feels unstable or effortful, it may be worth discussing both ocular and neural factors at your next comprehensive exam.

PMID: 38871345

04/08/2026

Most people assume vision is slow because it feels effortless. In reality, the visual system is remarkably fast.

Research shows that the brain can process meaningful visual information in approximately 100–120 milliseconds. That is nearly one tenth of a second. Within that brief window, neural pathways from the retina to the visual cortex begin extracting structure, contrast, motion, and relevance.

This speed supports:
• Rapid threat detection.
• Efficient reading and scanning.
• Coordinated motor responses.
• Real-time environmental awareness.

Visual processing speed is not just about how clearly you see. It reflects how efficiently the retina, optic nerve, and visual cortex communicate. When this timing is disrupted, patients may report slowed reactions, difficulty tracking, or cognitive fatigue even when visual acuity appears normal.

Clinically, this is why reaction time, visual attention, and oculomotor function matter. Vision is a brain process, not just an eye measurement.

If you experience delayed responses, visual overwhelm, or fatigue during fast-paced tasks, discuss visual processing at your next comprehensive exam.

PMID: 17003801

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