Slit-Lamp Laser Lenses: Magnification and Spot Size Factors

Last updated: October 2026

The contact lens you choose changes the field of view, the image orientation and, most importantly, the true size of the laser spot on the retina. Always multiply the dial setting by the lens's laser spot factor.

Retinal laser lenses

Lens	Image magnification	Laser spot factor	Use
Goldmann three-mirror	About 0.93×	About 1.08×	Posterior pole (centre) and periphery (mirrors); image in the mirrors is inverted top to bottom
Mainster Standard (focal/grid)	About 0.96×	About 1.05×	Macular focal or grid laser
Volk Area Centralis	About 1.06×	About 0.94×	High-detail macular work
Mainster Wide Field	About 0.67×	About 1.50×	PRP
Volk TransEquator	About 0.69×	About 1.44×	PRP
Volk SuperQuad 160 / Mainster PRP 165	About 0.5×	About 2.0×	Fast PRP to the far periphery

Example: a 200 µm setting through a SuperQuad gives about a 400 µm burn on the retina, with four times the area, so use less power per spot than you would with a Goldmann lens.

Anterior segment laser lenses

Lens	Feature	Use
Abraham iridotomy lens	+66 D button; concentrates energy and magnifies (about 1.6×)	Nd:YAG or argon iridotomy
Wise iridotomy lens	+103 D button; about 2.6× magnification	Iridotomy with less energy
Latina SLT lens	Single mirror, no magnification of the 400 µm spot	Selective laser trabeculoplasty
Ritch trabeculoplasty lens	Four mirrors with convex buttons	ALT
Capsulotomy lenses (Abraham, Peyman)	Plano-convex buttons focus energy at the capsule	Nd:YAG posterior capsulotomy

Where residents slip

Using the dial setting as the true spot size: wide-field lenses make the retinal spot larger.
Forgetting that the image in the Goldmann mirrors is upside down.
Treating near the fovea through a wide-field lens: use a macular lens.

Revise with flip cards

Key sources

Manufacturer specifications (Ocular Instruments, Volk Optical) for image magnification and laser spot factors

📘 Want the exam-ready deep dive? This topic, and much more is covered in Ophthalmology Explorer (A High-Yield Clinical Reference for Ophthalmology Residents, Fellows & Board Exams) — available on Kindle. See all my books.

Written and medically reviewed by Dr. Dhaval Patel, MD (Ophthalmology, AIIMS New Delhi) · Editorial policy

Consultant, Cataract & Refractive Surgery — among a small number of AIIMS-trained ophthalmologists practicing in Gujarat. Read full credentials & experience or view his 28 publications on ResearchGate.

📚 Also the author of OKAT Decoded, FRCOphth Decoded and other high-yield ophthalmology exam-prep books used by residents and PG aspirants.

Want to know more about treatment? Read about Retina Treatment at Sadbhaav or book a consultation with Dr. Dhaval Patel.