Common Eye Tests Explained: Understanding Your Eye Examination

Common Eye Tests Explained

Understanding eye tests helps you participate actively in your eye care. Dr. Ahmed Sherif explains each examination component.

Visual Acuity Test

Purpose: Measures sharpness of vision How it Works:

Read letters on chart (Snellen chart)

One eye at a time

Different sizes of letters

Results noted as 20/20, 20/40, etc.

What Results Mean:

20/20: Normal vision

20/40: See at 20 feet what normal eye sees at 40 feet

20/15: Better than normal

Legal driving limit: Usually 20/40 or better

Refraction Assessment

Purpose: Determines eyeglass prescription Equipment: Phoropter (the big machine with lenses) Process:

"Which is better, 1 or 2?"

Multiple lens combinations tested

Fine-tunes your prescription

Determines myopia, hyperopia, astigmatism

Output: Prescription with:

Sphere (SPH): Plus or minus number

Cylinder (CYL): Astigmatism correction

Axis: Angle of astigmatism

Add: Reading addition (if needed)

Tonometry (Eye Pressure)

Purpose: Screen for glaucoma Methods:

Air-Puff Tonometry

Non-contact measurement

Quick puff of air to eye

Mildly startling but painless

Good screening tool

Applanation Tonometry (Gold Standard)

Small probe touches cornea (numbed first)

Most accurate measurement

Used at Dar El Oyoun

Feels like gentle pressure

Normal Range: 10-21 mmHg High Pressure: Risk for glaucoma Low Pressure: Can indicate other issues

Slit Lamp Examination

Purpose: Detailed view of eye structures What Doctor Sees:

Eyelids and lashes

Cornea clarity

Iris and pupil

Lens (for cataracts)

Anterior chamber

Tear film quality

Brightlight: Illuminates internal structures Magnification: Up to 40x zoom Duration: 5-10 minutes Comfort: Bright but not painful

Dilated Eye Exam

Purpose: Examine retina and optic nerve Process:

1. Dilation drops administered

2. Wait 15-30 minutes for full dilation

3. Doctor examines with bright light

4. Detailed retinal viewing

Effects Last: 4-6 hours

Blurred near vision

Light sensitivity

Cannot drive immediately

Bring sunglasses

What's Examined:

Retina health

Macula condition

Optic nerve

Blood vessels

Signs of disease

Optical Coherence Tomography (OCT)

Purpose: Detailed retinal imaging How it Works:

Like ultrasound but uses light

Cross-sectional view of retina

Measures retinal thickness

Non-invasive, no contact

Detects:

Macular degeneration

Diabetic retinopathy

Glaucoma nerve damage

Macular holes

Retinal swelling

At Dar El Oyoun: State-of-the-art OCT technology

Corneal Topography

Purpose: Maps corneal surface Uses:

LASIK evaluation

Keratoconus detection

Astigmatism assessment

Contact lens fitting

Post-surgical monitoring

Process:

Look at target in device

Automated scanning

Generates color map

Shows corneal shape irregularities

Results: Detailed elevation and curvature maps

Visual Field Test (Perimetry)

Purpose: Assess peripheral vision Process:

Look straight ahead at central target

Indicate when you see peripheral lights

Computer maps your visual field

Each eye tested separately

Duration: 5-10 minutes per eye Detects:

Glaucoma damage

Neurological issues

Retinal problems

Blind spots

Pachymetry

Purpose: Measure corneal thickness Importance:

LASIK candidacy

Glaucoma risk assessment

Accurate pressure interpretation

Normal Range: 520-580 microns Quick Test: Non-invasive ultrasound or optical

Color Vision Testing

Purpose: Detect color blindness Common Test: Ishihara plates

Numbers hidden in colored dots

Different types visible to different color perceptions

Quick screening (1-2 minutes)

Types of Color Blindness:

Red-green (most common)

Blue-yellow (rare)

Complete (very rare)

Autorefractor

Purpose: Quick prescription estimate How it Works:

Automated measurement

Look at image inside machine

Computer calculates prescription

Starting point for refraction

Advantage: Fast, objective Limitation: May not be perfectly accurate Use: Initial assessment, children, verification

Specialized Tests at Dar El Oyoun

Corneal Endothelial Cell Count

Assesses corneal health

Important for cataract surgery planning

Contact lens wear monitoring

Wavefront Aberrometry

Measures optical imperfections

Custom LASIK planning

Higher-order aberrations

Night vision assessment

Fundus Photography

Documents retinal appearance

Tracks changes over time

Diabetic retinopathy monitoring

Patient education tool

Preparing for Your Eye Exam

Before Appointment:

List current medications

Note vision concerns

Bring current glasses/contacts

Know family eye history

Arrange ride if dilation expected

What to Bring:

Insurance information

Previous eye records

List of questions

Sunglasses (for after dilation)

Questions to Ask:

What did tests reveal?

Do I need glasses/new prescription?

Any eye health concerns?

When should I return?

Any restrictions or recommendations?

Frequency Recommendations

Dr. Sherif recommends eye exams:

Age 18-40: Every 2-3 years

Age 40-54: Every 2 years

Age 55-64: Every 1-2 years

Age 65+: Annually

More Frequent If You Have:

Diabetes

High blood pressure

Family history of glaucoma/macular degeneration

Previous eye surgery

High myopia

Taking certain medications

At Dar El Oyoun Hospital

Dr. Ahmed Sherif uses the latest diagnostic technology to provide comprehensive eye examinations with:

Advanced equipment

Detailed assessments

Personalized care

Thorough explanations

Treatment planning

Schedule Your Comprehensive Eye Exam:

Sheikh Zayed: 02-37963013

Dokki: 02-33382136

WhatsApp: +201066479644

Early detection through regular exams protects your vision for life.