ABO Cheat Sheet 2026

The 30 highest-yield ABO facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Which anesthetic agent must be avoided in a patient with an intraocular gas bubble? → Nitrous oxide
2. Which is the leading theory for the fluid source in optic pit maculopathy? → Vitreous fluid and/or cerebrospinal fluid via the pit
3. Which retinal detachment configuration is LEAST suited to pneumatic retinopexy based on the original PIVOT-era selection criteria? → Inferior break between 5 and 7 o'clock
4. Which of the following is the most common benign intraocular tumor in adults? → Choroidal nevus
5. Rayleigh scattering intensity is related to wavelength in what way? → Inversely proportional to the fourth power of wavelength
6. According to the Mycotic Ulcer Treatment Trial I, which topical agent gave better outcomes for filamentous fungal keratitis, especially Fusarium? → Natamycin
7. Which pair of ocular side effects is characteristic of netarsudil? → Conjunctival hyperemia and corneal verticillata
8. Which feature best distinguishes Vogt-Koyanagi-Harada disease from sympathetic ophthalmia? → Absence of a history of penetrating ocular trauma or surgery
9. An RGP lens is fit 0.50 D steeper than flat K. How should the contact lens power be adjusted from the spectacle refraction? → Add -0.50 D
10. What is the most common cause of failure after successful retinal detachment repair? → Proliferative vitreoretinopathy
11. On fluorescein angiography, APMPPE lesions characteristically show which pattern? → Early hypofluorescence (blockage) with late staining
12. Corneal melts were most notably reported with which topical NSAID formulation? → Generic diclofenac sodium
13. Below which CD4 count does the risk of CMV retinitis rise sharply in patients with AIDS? → 50 cells/µL
14. What is the primary physiological cause of presbyopia? → Decreased elasticity and hardening of the crystalline lens.
15. What is the preferred chelating agent for removing visually significant calcific band keratopathy? → Disodium EDTA
16. A Horner pupil does not dilate after hydroxyamphetamine. Where is the lesion? → Postganglionic (third-order) neuron
17. In the Tube Versus Trabeculectomy (TVT) study of eyes with prior surgery, what was found at 5 years? → The tube (Baerveldt 350) had a lower failure rate than trabeculectomy with MMC
18. Which finding came from the Optic Neuritis Treatment Trial? → Oral prednisone alone increased the risk of recurrent optic neuritis
19. Which condition is characterized by transient visual loss in one eye described as a 'curtain' descending? → Amaurosis fugax
20. On the Van Herick test, which finding suggests an angle at risk of closure? → Peripheral AC depth less than one-quarter of corneal thickness
21. Why is the anterior chamber angle not visible without a gonioscopy lens? → Total internal reflection at the tear film-air interface
22. What is the main dose-limiting systemic toxicity of IV foscarnet used for CMV retinitis? → Nephrotoxicity
23. What is the main purpose of fogging during manifest refraction? → To relax accommodation by adding plus power
24. Inferior peripheral corneal thinning 1-2 mm from the limbus, with the protrusion above the thinned band and a 'crab claw' topography, suggests which diagnosis? → Pellucid marginal degeneration
25. Which hemoglobin genotype is most associated with proliferative sickle cell retinopathy? → HbSC
26. What is the first-line treatment approach for bilateral retinoblastoma in modern practice? → Systemic chemoreduction followed by focal consolidation
27. What is the most common form of intraocular malignancy overall, including secondary tumors? → Choroidal metastases
28. A patient's refraction is -4.50 +1.00 x 090. To correct this refractive error, what type of lens is required? → A sphero-cylindrical concave lens
29. A 70-year-old woman has chronic unilateral blepharoconjunctivitis unresponsive to treatment, with loss of lashes. Which malignancy must be excluded? → Sebaceous carcinoma
30. A boy has a spoke-wheel foveal pattern and peripheral schisis. Which ERG finding is classic? → Electronegative ERG with reduced b-wave