Low-power lens
+14D to +18D: High magnification, narrow field. Suitable for detailed observation of the posterior pole.
Binocular Indirect Ophthalmoscopy
Key points at a glance
Section titled “Key points at a glance”1. What is Binocular Indirect Ophthalmoscopy (BIO)?
Section titled “1. What is Binocular Indirect Ophthalmoscopy (BIO)?”Ophthalmoscopy is a routine examination method for observing the fundus, and is broadly divided into direct and indirect ophthalmoscopy.
Direct ophthalmoscopy provides an upright image at about 15× magnification. In contrast, indirect ophthalmoscopy provides an inverted image at 2–5× lower magnification, but offers a wider field of view and is excellent for observing the peripheral retina.
Binocular indirect ophthalmoscopy (BIO) achieves three-dimensional (stereoscopic) observation of the fundus by projecting the optical axis and the left and right visual axes through the pupil. Unlike monocular indirect ophthalmoscopy, it allows stereopsis because both eyes are used.
The main features of BIO are as follows.
- Wide-field fundus observation: Continuous observation from the posterior pole to the periphery is possible.
- Stereopsis: Useful for evaluating the borders of shallow retinal detachments and macular edema.
- Combination with scleral depression: One hand is free, making it easy to combine with a scleral depressor. It allows access to the ora serrata, pars plana, and pars plicata.
- Dynamic observation: Allows dynamic evaluation of the peripheral retina while indenting the sclera
It is useful for observing general fundus diseases, and is particularly effective for three-dimensional evaluation of retinal detachment, assessment of macular edema, and retinal neovascularization. The American Academy of Ophthalmology (AAO) Preferred Practice Pattern 2025 also recommends binocular indirect ophthalmoscopy with scleral depression under dilated pupils for evaluation of acute posterior vitreous detachment, retinal tears, and lattice degeneration[2].
Q
Is this examination painful?
A
The examination itself is not painful. You may feel a slight irritation when the dilating eye drops are applied. If scleral depression is performed, there may be a mild pressure sensation around the eye, but it is not severe pain.
2. Equipment Configuration and Optical Principles
Section titled “2. Equipment Configuration and Optical Principles”
Matteo Fallico; Pietro Alosi; Michele Reibaldi; Antonio Longo; Vincenza Bonfiglio; Teresio Avitabile. Scleral Buckling: A Review of Clinical Aspects and Current Concepts. J Clin Med. 2022 Jan 9; 11(2):314 Figure 1. PMCID: PMC8778378. License: CC BY.
(A) a left eye inferior rhegmatogenous retinal detachment in a young phakic patient, the macula looks attached; (B) a fully reattached retina following scleral buckling with a 360 encircling band with an inferotemporal buckle.
Device Structure
Section titled “Device Structure”BIO consists of three components: a headband, a binocular lens with mirrors, and a light source.
- Light source: Located between the examiner’s eyes, just above the bridge of the nose
- Mirror (prism structure): Bends the optical axis from the light source, splits the reflected light from the fundus left and right, and delivers the image to both eyes of the examiner
- Headband fixation: Fixes the light source to the head, freeing one hand. This allows simultaneous use of a scleral depressor.
Condensing Lens
Section titled “Condensing Lens”The optical principle of indirect ophthalmoscopy is as follows. Light from the source enters the pupil, and the reflected light from the fundus is focused in front of the eye by a convex lens (condensing lens). The examiner observes this image with both eyes.
Magnification is calculated as “refractive power of the eye ÷ refractive power of the condensing lens.” For example, when using a +20D lens, it is 60 ÷ 20 = 3×. The higher the diopter, the lower the magnification and the wider the field of view.
The commonly used condensing lens range is +14D to +30D.
Standard lens
+20D: 3x magnification. The most widely used standard lens for adult BIO.
High-power lens
+25D to +30D: Low magnification, wide field. Suitable for use in children, premature infants, and cases with small pupils.
The position of the condensing lens directly affects observation quality. If too close, illumination of the peripheral retina is insufficient; if too far, reflected light from the periphery does not reach the examiner. A holding distance of about 5 cm from the patient’s eye is a guideline.
Stereopsis adjustment
Section titled “Stereopsis adjustment”Stereopsis is achieved by aligning the optical axis and both visual axes into the pupil. Narrowing the interpupillary distance facilitates insertion into the pupil, while widening enhances stereopsis. When evaluating the border of a shallow retinal detachment or macular edema, a slightly enhanced stereoscopic setting is useful.
Filters
Section titled “Filters”The following filters are used depending on the purpose.
White light
No filter: Used to observe the overall fundus with natural colors.
Yellow
Yellow filter: Reduces light intensity. Used for patients complaining of photophobia.
Red-free
Red-free filter: Useful for improving visualization of blood vessels, hemorrhages, and nerve fiber layer defects.
Blue
Blue filter: Used for observing lesions of the internal limiting membrane and preretinal layers, and for fluorescein angiography.
3. Examination Procedure and Techniques
Section titled “3. Examination Procedure and Techniques”Mydriasis
Section titled “Mydriasis”Adequate mydriasis is necessary to observe the peripheral fundus. Since the bright light of BIO tends to constrict the pupil, maximal dilation is important.
The mydriatic agents used are as follows:
- Parasympatholytic agents: Tropicamide 0.5% (e.g., Mydrin M®)
- Sympathomimetic agents: Phenylephrine 2.5% or 10% (e.g., Neosynephrine®)
Combining both agents enhances the mydriatic effect. The effect lasts for several hours after dilation, during which glare and blurred near vision occur.
BIO Procedure
Section titled “BIO Procedure”The standard procedure is as follows.
- Confirm that mydriasis is sufficient
- Place the patient in a supine position and ensure enough space for the examiner to move freely around the head
- Select the appropriate condensing lens for the purpose
- Secure the BIO device firmly to the head with a headband
- Adjust the interpupillary distance and beam height
- Set the spot size and illumination intensity (start with low illumination)
- Apply necessary filters
- Hold the lens about 5 cm away from the patient’s eye
- Instruct the patient to look straight up, and the examiner stands to the side and leans in to observe
- Examine the peripheral retina 360 degrees while having the patient change gaze direction
- Perform scleral depression if necessary
- Examine the macula last (because exposure to bright light may reduce patient cooperation)
Reasons for Performing in the Supine Position
Section titled “Reasons for Performing in the Supine Position”The reasons why the supine position is recommended are as follows.
- Easier to sketch on the fundus chart
- Allows uniform observation of the entire peripheral retina
- Scleral depression can be performed easily and safely
- In the sitting position, stereoscopic viewing becomes difficult on the temporal and nasal sides, and the range of depression examination is limited
Scleral Depression
Section titled “Scleral Depression”The curvature of the anterior part of the eye prevents observation of the far periphery. Scleral depression is a technique that indents the sclera from the outside to bring the peripheral retina into the viewing field.
Instruments: Various depressors such as Schepens, O’Connor, Schocket double-ended, Josephberg-Besser, and Flynn are used.
Application by site:
- Superior, inferior, temporal: Apply the depressor over the eyelid skin with gentle but firm pressure
- Nasal: Manipulate directly on the conjunctiva
Situations where scleral depression is especially recommended:
- Patients with symptoms of photopsia or floaters
- Patients at risk for retinal tears or retinal detachment
- When searching for tears at the edge of lattice degeneration
- Differentiation of pseudo-tears (white with pressure; WWP may appear normal due to color change during compression)
BIO with scleral indentation is considered the gold standard for detecting peripheral retinal tears. Reports indicate that approximately 11% of acute horseshoe tears are missed with non-contact slit-lamp examination, making BIO with scleral indentation essential for evaluating the far periphery [3,5]. In recent years, comparisons with ultra-widefield fundus imaging (UWF) have been conducted, but some reports show that about half of horseshoe tears are missed by UWF, suggesting that UWF alone cannot fully replace scleral indentation [4].
During scleral indentation, intraocular pressure transiently increases significantly, with reports indicating an average of about 65 mmHg (maximum 88 mmHg) even in routine outpatient examinations. Since this may affect ocular perfusion, care should be taken regarding the duration and force of indentation in patients with ocular hypertension or glaucoma [6].
Q
Is dilation always necessary?
A
Dilation is necessary to adequately observe the peripheral fundus. After dilation, glare and blurred near vision persist for several hours, so patients should be advised to avoid driving on the day of the examination. In emergencies or when combined with slit-lamp examination using a pre-corneal lens, it may be performed without dilation depending on the purpose.
Q
When is scleral indentation performed?
A
It is particularly recommended for patients with photopsia or floaters, or those at risk of retinal tears or detachment. Indentation is essential for evaluating the far periphery (near the ora serrata), and tears at the edge of lattice degeneration may only become apparent with indentation.
4. Clinical Applications and Comparison with Other Examination Methods
Section titled “4. Clinical Applications and Comparison with Other Examination Methods”Advantages and Disadvantages of BIO
Section titled “Advantages and Disadvantages of BIO”Advantages:
- Provides a wide field of view, allowing visualization of the peripheral fundus
- Relatively good observation possible even with small pupils or media opacities (cataract, vitreous hemorrhage, etc.)
- Suitable for fundus examination in infants and children (gold standard for retinopathy of prematurity screening [7])
- Stereoscopic view allows assessment of retinal elevation height and vitreous traction
- Can be observed up to the ora serrata when used together with a scleral depressor
Disadvantages:
- Magnification is low (2–5×), making it unsuitable for detailed observation of fine lesions
- Produces an inverted image, requiring practice for orientation (understanding up/down and left/right)
- Device attachment and adjustment are more complicated compared to monocular indirect ophthalmoscopy
Comparison with other examination methods
Section titled “Comparison with other examination methods”The main differences between monocular and binocular indirect ophthalmoscopy are shown below.
| Item | Monocular indirect ophthalmoscopy | Binocular indirect ophthalmoscopy |
|---|---|---|
| Ease of use | Simple | Complex |
| Stereopsis | Not possible | Possible |
| Scleral depression | Unsuitable | Suitable |
The main differences between direct and indirect ophthalmoscopy are shown below.
| Item | Direct ophthalmoscope | Indirect ophthalmoscope |
|---|---|---|
| Magnification | Approximately 15x | 2–5x |
| Field of view | Narrow (8–10°) | Wide |
| Peripheral observation | Difficult | Easy |
Differentiation from Slit-Lamp Microscopy
Section titled “Differentiation from Slit-Lamp Microscopy”BIO and slit-lamp microscopy (slit-lamp examination) have different roles and are used complementarily.
- Role of BIO: Provides an overview of the entire fundus, evaluating the positional relationship, extent, and three-dimensional shape of lesions. Dynamic observation of the periphery is performed with scleral indentation.
- Role of slit lamp with a pre-corneal lens: Excellent for detailed observation including the adhesion state between the vitreous and retina. Used in combination with Goldmann three-mirror lens, SuperField lens, Volk lens, etc.
In clinical practice, the standard procedure is to first perform fundus charting with BIO, followed by detailed examination of the retina and vitreous using a slit lamp with a Goldmann three-mirror lens or similar.
Fundus Charting
Section titled “Fundus Charting”Fundus sketching (fundus charting) using BIO is an important clinical skill.
Fundus charts are essential for managing fundus diseases, especially retinal detachment. It is said that “retinal detachment surgery without a sketch is as reckless as sailing without a chart.” In scleral buckling surgery, the quality of the sketch directly affects surgical outcomes, the surgeon’s skill improvement, and the team’s shared understanding of the pathology.
Chart paper: Retinal detachment charts designed by Schepens and Tolentino are widely used. Typically, three concentric circles (equator, ora serrata, posterior edge of ciliary processes) are printed.
Color code (AAO recommended): Eight colors are used to record retinal findings.
- Black: Tears, breaks, and transparent findings
- Red: Hemorrhage and vascular findings
- Blue: Detached area and fluid
- Yellow: Macular findings
- Green: Lattice degeneration
- Brown/Orange/Purple: Other degeneration, pigment changes, etc.
Q
How should binocular indirect ophthalmoscopy and slit-lamp examination be used differently?
A
Binocular indirect ophthalmoscopy excels in wide-field stereoscopic observation and is suitable for grasping the positional information of the entire fundus. Slit-lamp biomicroscopy with a pre-corneal lens is superior for detailed observation of vitreoretinal adhesions, etc. The two are complementary; the standard procedure is to create a fundus chart using indirect ophthalmoscopy and then perform detailed examination with the slit lamp.
5. History and Development
Section titled “5. History and Development”The history of fundus observation dates back to the 19th century.
- 1846: Dr. William Cumming described the optical principles and proposed the concept of fundus observation.
- 1851: Hermann von Helmholtz designed the first direct ophthalmoscope, enabling practical fundus observation.
- 1852: Christian Georg Theodor Ruete introduced a concave condensing lens, establishing indirect ophthalmoscopy.
- 1945: Dr. Charles Louis Schepens developed the binocular indirect ophthalmoscope, revolutionizing retinal detachment management and building the foundation of modern fundus examination[1].
- Modern era: Battery-powered wireless types have become widespread, greatly improving operability.
Schepens not only developed the binocular indirect ophthalmoscope but also greatly contributed to the popularization of fundus charts and the systematization of retinal detachment surgery. He is called the “father of retinal detachment”[1].
References
Section titled “References”- Sen M, Honavar SG. Charles L. Schepens: Eye Spy. Indian J Ophthalmol. 2023;71(7):2625-2627. PMID: 37417098. PMCID: PMC10491037.
- Kim SJ, Bailey ST, Kovach JL, et al. Posterior Vitreous Detachment, Retinal Breaks, and Lattice Degeneration Preferred Practice Pattern®. Ophthalmology. 2025;132(4):P163-P196. PMID: 39918519.
- Raevis J, Hariprasad SM, Shrier E. The Depressing Part of Retina: A Review of Scleral Depression and Scleral Indentation. Ophthalmic Surg Lasers Imaging Retina. 2021;52(2):71-74. PMID: 33626165.
- Lin AC, Kalaw FGP, Schönbach EM, et al. The Sensitivity of Ultra-Widefield Fundus Photography Versus Scleral Depressed Examination for Detection of Retinal Horseshoe Tears. Am J Ophthalmol. 2023;255:73-79. PMID: 37468086.
- Natkunarajah M, Goldsmith C, Goble R. Diagnostic effectiveness of noncontact slitlamp examination in the identification of retinal tears. Eye (Lond). 2003;17(5):607-609. PMID: 12855967.
- Trevino R, Stewart B. Change in intraocular pressure during scleral depression. J Optom. 2015;8(4):244-251. PMID: 25444648.
- Dhaliwal C, Wright E, Graham C, McIntosh N, Fleck BW. Wide-field digital retinal imaging versus binocular indirect ophthalmoscopy for retinopathy of prematurity screening: a two-observer prospective, randomised comparison. Br J Ophthalmol. 2009;93(3):355-359. PMID: 19028742.