The Survey of the Natural Sciences is the first and longest section of the Optometry Admission Test. The details below come from the OAT 2026 Candidate Guide, published by the Optometry Testing Program.
The structure
- 100 questions in 90 minutes, about 54 seconds per question.
- Biology: 40 questions
- General Chemistry: 30 questions
- Organic Chemistry: 30 questions
Biology is the largest share, so it deserves the most study time, but the two chemistry subjects together make up 60 percent of the section.
Related: What to Expect on the OAT: Format, Scoring, and How to Prepare
Biology topics
- Cell and molecular biology: metabolism (including photosynthesis and enzymes), membrane transport and signaling, mitosis and meiosis, cell structure and biomolecules
- Diversity of life: viruses, bacteria, archaea, fungi, protists, plants and animals
- Structure and function of systems: the major body systems, from skeletal and muscular to nervous, endocrine and reproductive
- Genetics: molecular, human, classical and chromosomal genetics, gene expression and epigenetics
- Evolution and ecology: natural selection, population genetics and speciation, behavior and ecology
General chemistry topics
The guide lists stoichiometry, gases, liquids and solids, solutions, acids and bases, chemical equilibria, thermodynamics and thermochemistry, kinetics, oxidation-reduction, atomic and molecular structure, periodic properties, nuclear reactions, and laboratory techniques. A periodic table is provided on screen during this part of the section.
Organic chemistry topics
Organic chemistry covers mechanisms, the chemical and physical properties of molecules (including spectroscopy and lab techniques), stereochemistry, nomenclature, reactions of the major functional groups and multi-step synthesis, and acid-base chemistry. The guide notes that updated organic chemistry specifications were anticipated in 2026, mainly renaming topics and listing subtopics in more detail rather than changing content. Check the specifications in effect for your test date.
How to prepare
- Weight your study to the question counts. Biology alone is 40 of the 100 questions.
- Practice at pace. Under a minute per question leaves little time for long calculations, so know your chemistry shortcuts.
- Don't neglect lab and data questions. Both chemistry lists include laboratory skills.
- Take full-length timed sections. Ninety minutes of mixed science is tiring, and stamina matters.