Ophthalmology Calculators

Maps the patient's distance visual acuity (best-corrected, better eye, presenting acuity) to its LogMAR equivalent and the WHO 2019 ICD-11 visual-impairment category. Single common reference for documentation, DVLA decisions, certification of vision impairment (CVI), and study endpoints. LogMAR = log₁₀(1 / decimal acuity); each step on a standardised ETDRS chart is 0.10 log units (5 letters).

Globally adopted clinical classification of diabetic retinopathy (Wilkinson 2003, AAO 2017). Drives screening interval and laser/anti-VEGF decisions. Combine with diabetic macular oedema (DMO) staging.

Age-Related Eye Disease Study simplified categories (AREDS Report 18, 2005). Stratifies risk of progression to advanced AMD over 5 years and guides AREDS2 supplementation.

Categorises Goldmann applanation IOP (best of multiple readings, mid-morning) for ocular-hypertension and glaucoma decisions. Apply central corneal thickness (CCT) correction (Ehlers / Dresdner) where available — thin cornea (<540 µm) underestimates true IOP by ~2–5 mmHg.

Quantifies aqueous tear production (Schirmer I — without anaesthesia). Strip placed at junction of middle and lateral 1/3 of lower lid, eyes closed for 5 minutes. Wetting <5 mm/5 min is a major criterion in 2016 ACR/EULAR Sjögren's classification.

Original classification of chemical (alkali/acid) eye injuries (Roper-Hall 1965), based on corneal involvement and limbal ischaemia. Predicts visual prognosis and guides referral urgency. The Dua classification (2001) is a more granular modern alternative.

Modern 6-grade classification (Dua 2001) using analogue clock-hour limbal involvement and percentage conjunctival involvement. More granular than Roper-Hall, with better prognostic accuracy.

Hertel readings measure axial globe position (lateral orbital rim → corneal apex). Caucasian adult normal 12–22 mm; ≥2 mm asymmetry is significant. Higher in African and Asian populations. Used in thyroid eye disease, orbital tumour, cellulitis, and post-trauma evaluation.

Classification of diabetic macular oedema combining historical ETDRS clinically significant macular oedema (CSME) criteria with modern OCT-based centre-involving (CI-DMO) versus non-centre-involving (NCI-DMO) terminology. Drives anti-VEGF / laser decisions.

Graded by % of anterior chamber filled with blood after blunt trauma. Higher grade predicts secondary haemorrhage (rebleed at 2–5 days), elevated IOP, and corneal blood-staining.

Visual-field-based staging of glaucomatous damage (Hodapp 1993) using mean deviation (MD) on 24-2 SITA-Standard fields plus pattern of central involvement. Used to stratify follow-up frequency and treatment intensity.

International Classification of Retinopathy of Prematurity 3rd revision (Chiang 2021). Combines Zone (I most posterior, III peripheral nasal), Stage (1–5), and Plus disease. Used to time treatment in screened preterm neonates.

Bedside estimation of ocular deviation when prism cover test is impractical (uncooperative child, dense amblyopia). Hirschberg: corneal light reflex displacement from pupil centre; each 1 mm ≈ 7° (≈15 prism dioptres / 15Δ). Krimsky modifies by adding prisms over fixing eye until reflex is centred.

ISGEO consensus continuum of primary angle closure disease (Foster 2002, EAGLE 2016). Distinguishes occludable angles (PACS) from those with PAS or elevated IOP (PAC) and from established glaucomatous neuropathy (PACG). Critical for laser-iridotomy and lens-extraction decisions.

Goldmann tonometry assumes CCT of 520–545 µm. Thin corneas under-read, thick corneas over-read true IOP. Approximate corrections: Ehlers (~5 mmHg per 70 µm), Dresdner (~1 mmHg per 25 µm), Doughty meta-analysis (~2.5 mmHg per 50 µm). Pick the CCT band to apply the typical adjustment.

International Myopia Institute classification (IMI 2019). Spherical equivalent (SE) refraction in dioptres after cycloplegic refraction in children. Higher myopia confers greater lifetime risk of myopic maculopathy, retinal detachment, glaucoma, and cataract.