American Board of Optometry (ABO)
Certification Practice Exam Questions
And Correct Answers (Verified Answers)
Plus Rationales 2025|2026 Q&A |
Instant Download Pdf
1.-Which-cranial-nerve-controls-the-lateral-rectus-muscle?-
A. Oculomotor-(III)-
B. Trochlear-(IV)-
C. Abducens-(VI)-
D. Optic-(II)-
Rationale:-The-lateral-rectus-muscle-abducts-the-eye-and-is-innervated-by-the-
sixth-cranial-nerve,-the-abducens-nerve.-
-
2.-What-is-the-most-common-cause-of-bacterial-conjunctivitis-in-adults?-
A. Pseudomonas-aeruginosa-
B. Staphylococcus-aureus-
C. Haemophilus-influenzae-
,D. Streptococcus-pneumoniae-
Rationale:-Staphylococcus-aureus-is-the-most-common-bacterial-pathogen-in-
adult-bacterial-conjunctivitis,-often-presenting-with-purulent-discharge.-
-
3.-A-patient-presents-with-halos-around-lights-and-increased-intraocular-
pressure.-The-most-likely-diagnosis-is:-A.-Open-angle-glaucoma-
B. Acute-angle-closure-glaucoma-
C. Cataract-
D. Uveitis-
Rationale:-Acute-angle-closure-glaucoma-presents-with-sudden-eye-pain,-
halos-around-lights,-nausea,-and-a-markedly-elevated-intraocular-pressure.-
-
4.-What-is-the-target-diopter-for-a-myopic-patient-who-is--3.00-D-and-wants-
full-correction?-
A. -2.00-D-
B. -3.00-D-
C. -1.50-D-
D. 0.00-D-
Rationale:-Full-correction-for-myopia-is-the-exact-refractive-error-measured-
during-refraction,-in-this-case--3.00-D.-
-
,5.-Which-layer-of-the-cornea-is-primarily-responsible-for-maintaining-corneal-
dehydration-and-clarity?-
A. Epithelium-
B. Stroma-
C. Bowman's-layer-
D. Endothelium-
Rationale:-The-corneal-endothelium-actively-pumps-fluid-out-of-the-stroma-to-
maintain-corneal-transparency.-
-
6.-Which-test-is-most-sensitive-for-detecting-early-keratoconjunctivitis-sicca?-
A. Fluorescein-staining-
B. Rose-Bengal-staining-
C. Schirmer-test-
D. Tonometry-
Rationale:-The-Schirmer-test-measures-tear-production-and-is-sensitive-for-
early-dry-eye-detection.-
-
7.-A-patient-with-a-new-cataract-is-most-likely-to-report:-
A. Eye-pain-
B. Blurred-vision,-especially-at-night-
C. Redness-and-itching-
D. Diplopia-
, Rationale:-Cataracts-commonly-cause-gradual,-painless-blurred-vision-and-
glare,-particularly-at-night.-
-
8.-Which-vitamin-deficiency-is-associated-with-night-blindness?-
A. Vitamin-C-
B. Vitamin-D-
C. Vitamin-A-
D. Vitamin-B12-
Rationale:-Vitamin-A-is-essential-for-rhodopsin-regeneration;-deficiency-leads-
to-nyctalopia-(night-blindness).-
-
9.-The-most-common-cause-of-permanent-vision-loss-in-patients-over-65-is:-
A. Glaucoma-
B. Cataracts-
C. Age-related-macular-degeneration-(AMD)-
D. Diabetic-retinopathy-
Rationale:-AMD,-particularly-the-dry-type,-is-the-leading-cause-of-irreversible-
central-vision-loss-in-older-adults.-
-
10.-Which-retinal-layer-is-affected-in-central-serous-retinopathy?-
A. Ganglion-cell-layer-
B. Inner-nuclear-layer-
Certification Practice Exam Questions
And Correct Answers (Verified Answers)
Plus Rationales 2025|2026 Q&A |
Instant Download Pdf
1.-Which-cranial-nerve-controls-the-lateral-rectus-muscle?-
A. Oculomotor-(III)-
B. Trochlear-(IV)-
C. Abducens-(VI)-
D. Optic-(II)-
Rationale:-The-lateral-rectus-muscle-abducts-the-eye-and-is-innervated-by-the-
sixth-cranial-nerve,-the-abducens-nerve.-
-
2.-What-is-the-most-common-cause-of-bacterial-conjunctivitis-in-adults?-
A. Pseudomonas-aeruginosa-
B. Staphylococcus-aureus-
C. Haemophilus-influenzae-
,D. Streptococcus-pneumoniae-
Rationale:-Staphylococcus-aureus-is-the-most-common-bacterial-pathogen-in-
adult-bacterial-conjunctivitis,-often-presenting-with-purulent-discharge.-
-
3.-A-patient-presents-with-halos-around-lights-and-increased-intraocular-
pressure.-The-most-likely-diagnosis-is:-A.-Open-angle-glaucoma-
B. Acute-angle-closure-glaucoma-
C. Cataract-
D. Uveitis-
Rationale:-Acute-angle-closure-glaucoma-presents-with-sudden-eye-pain,-
halos-around-lights,-nausea,-and-a-markedly-elevated-intraocular-pressure.-
-
4.-What-is-the-target-diopter-for-a-myopic-patient-who-is--3.00-D-and-wants-
full-correction?-
A. -2.00-D-
B. -3.00-D-
C. -1.50-D-
D. 0.00-D-
Rationale:-Full-correction-for-myopia-is-the-exact-refractive-error-measured-
during-refraction,-in-this-case--3.00-D.-
-
,5.-Which-layer-of-the-cornea-is-primarily-responsible-for-maintaining-corneal-
dehydration-and-clarity?-
A. Epithelium-
B. Stroma-
C. Bowman's-layer-
D. Endothelium-
Rationale:-The-corneal-endothelium-actively-pumps-fluid-out-of-the-stroma-to-
maintain-corneal-transparency.-
-
6.-Which-test-is-most-sensitive-for-detecting-early-keratoconjunctivitis-sicca?-
A. Fluorescein-staining-
B. Rose-Bengal-staining-
C. Schirmer-test-
D. Tonometry-
Rationale:-The-Schirmer-test-measures-tear-production-and-is-sensitive-for-
early-dry-eye-detection.-
-
7.-A-patient-with-a-new-cataract-is-most-likely-to-report:-
A. Eye-pain-
B. Blurred-vision,-especially-at-night-
C. Redness-and-itching-
D. Diplopia-
, Rationale:-Cataracts-commonly-cause-gradual,-painless-blurred-vision-and-
glare,-particularly-at-night.-
-
8.-Which-vitamin-deficiency-is-associated-with-night-blindness?-
A. Vitamin-C-
B. Vitamin-D-
C. Vitamin-A-
D. Vitamin-B12-
Rationale:-Vitamin-A-is-essential-for-rhodopsin-regeneration;-deficiency-leads-
to-nyctalopia-(night-blindness).-
-
9.-The-most-common-cause-of-permanent-vision-loss-in-patients-over-65-is:-
A. Glaucoma-
B. Cataracts-
C. Age-related-macular-degeneration-(AMD)-
D. Diabetic-retinopathy-
Rationale:-AMD,-particularly-the-dry-type,-is-the-leading-cause-of-irreversible-
central-vision-loss-in-older-adults.-
-
10.-Which-retinal-layer-is-affected-in-central-serous-retinopathy?-
A. Ganglion-cell-layer-
B. Inner-nuclear-layer-
