Calculators

⟳ Vertex Distance Δ Prentice's Rule ◧ Lens Thickness 👁 VA Converter ◱ Slab-Off 🔍 Spectacle Mag.

👁Contact Lenses 🔬Ocular Pathology 📚Clinical Trials 💊Drug Reference 📐Normal Values

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Snellen Hall

The optical reference library for eye care professionals

Optical calculators · Contact lens database · Ocular pathology · Clinical trials · Drug reference · Board-style quizzes

Clinical Databases

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Ocular Pathology

190+ conditions across 8 specialties — searchable by segment, with epidemiology, pathophysiology, signs, and treatment

Anterior Segment Posterior Segment Glaucoma Neuro-Ophthalm. Uveitis

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Contact Lens Database

95+ lenses — soft, scleral, hybrid, ortho-K, and specialty — with full parameter tables and Rx search

Daily Disposable Monthly Scleral Toric Ortho-K

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Reference Libraries

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Clinical Trials

30 landmark studies

MARINA · OHTS · ONTT · DEWS II · ATOM · LiGHT · CITT · BEAT-ROP

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Drug Reference

54 ocular medications

Glaucoma · Mydriatics · Anti-infectives · Anti-inflammatory · Anti-VEGF · Allergy/Dry Eye

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Normal Values

10 reference tables

IOP · RNFL · VF indices · BV norms · Accommodation · VA equivalents · CL fitting

Optical Calculators

Board Exam Preparation

NBEO · KMK · OptoPrep

Optometry Quiz

Clinical vignettes across 10 topics with 3 difficulty levels — posterior segment, glaucoma, neuro, pharmacology, color vision, BV, refraction, and more

Posterior SegmentAnterior SegmentGlaucomaNeuro-Ophthalm.Binocular VisionRefractionContact LensesPharmacologyColor Vision

183

questions

3

difficulty levels

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ABO · NOCE · NCLE

Optics & Dispensing

ABO / NOCE-style questions across all six exam domains — ophthalmic optics, products, instrumentation, dispensing, laws & standards, and anatomy/refraction

Ophthalmic OpticsProductsInstrumentationDispensingLaws & StandardsAnatomy

164

questions

6

ABO domains

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6Calculators

95+Contact Lenses

190+Conditions

30Key Trials

54Drug Entries

312Quiz Questions

For educational and professional reference only. Not for patient-facing diagnostic or treatment decisions. See full disclaimer in footer.

⚠ Important Disclaimer

Snellen Hall is an educational and clinical reference tool intended for licensed eye care professionals. All content is provided for informational purposes only and does not constitute medical advice, diagnosis, or a recommendation for treatment. Clinical decisions must be made by a qualified healthcare provider based on individual patient assessment and current clinical guidelines.

While every effort has been made to ensure accuracy and reference peer-reviewed literature, the creators and operators of Snellen Hall make no representations or warranties of any kind, express or implied, regarding the completeness, accuracy, reliability, suitability, or availability of any information contained herein. Clinical data, drug dosages, treatment protocols, and pharmaceutical approvals change frequently — always verify information against current primary literature, package inserts, and institutional guidelines before clinical application.

Snellen Hall and its creators shall not be liable for any errors, omissions, or inaccuracies in the content, nor for any actions taken in reliance on the information provided, including but not limited to clinical decisions, prescribing decisions, or patient outcomes. Use of this tool constitutes acceptance of these terms.

Contact lens parameter data is sourced from manufacturer specifications and may not reflect the most current product parameters. Always consult current manufacturer fitting guides and prescribing information.

Trademarks & affiliation. Product names, brand names, drug names, and trademarks referenced herein are the property of their respective owners and are used for identification and educational purposes only. Their use does not imply endorsement or affiliation. This site is an independent educational resource and is not affiliated with, sponsored by, or endorsed by the American Academy of Ophthalmology, the American Board of Opticianry, the NBEO, or any manufacturer named.

Sources. Clinical content is summarized in the authors' own words from standard peer-reviewed references (including the AAO Basic and Clinical Science Course, published clinical trials, consensus guidelines, and manufacturer package inserts), which are cited within individual entries. Summaries are original paraphrase and are not reproductions of the source texts. No copyrighted text, figures, or images from those sources are reproduced here.

© 2025 Snellen Hall · For professional reference use only · Not for patient-facing use · Educational content, not medical or legal advice