Ocular Endoscopy

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Cameron Reinisch
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Ocular endoscopy was first developed in 1934 by Thorpe. [1] The intraocular endoscope is a surgical and diagnostic tool that combines, within a single probe, an intraoperative camera with up to 600-micron resolution, a xenon light source for illumination, and an 810 nm diode laser fiber. An endoscope uses reflected (coaxial) light from a probe placed adjacent to the tissue to be visualized. [2] A critical advantage over the traditional operating microscope is bypassing opaque anterior segment media with a “side-on” approach rather than “top-down” (for corneal opacity, small pupil or prosthetic iris, dense cataract, and hyphema). Furthermore, it can visualize ocular structures difficult to assess even with clear media, such as retroirideal space, retrolental space, pars plana, pars plicata, ciliary sulcus, ciliary body, and far anterior retina.[2][3][4] Two ophthalmic endoscope designs are currently on the market. They differ mainly in their image relay system: the rigid GRIN lens system offers better light transmission and image quality but limited maneuverability and a narrower field of view, while the flexible fiberoptic system uses smaller, longer fibers for greater maneuverability, making it more widely adopted.[3][5][6]Early in the learning curve, a conventional wide-angle system should be kept set up alongside the endoscope so the surgeon can switch back to regain orientation. Early cases are best chosen among eyes with clear media.[2] No validated case number for proficiency has been published.[3]

History

The ocular endoscope was developed by Thorpe in 1934 to remove a nonmagnetic intraocular foreign body.[1]  The device consisted of an illumination source within a Galilean telescope, using an eyepiece for direct visualization inside the globe via an 8mm sclerotomy.[7] In 1978, Norris and Cleasby constructed a 1.7mm diameter endoscope, designed for both intraocular and orbital surgeries.[8] [9]Veniamin Volkov came along with the development of the flexible endoscope in 1990.[10] Eguchi and Arai expanded the technology by pairing the flexible endoscope with a “charge-coupled device” camera for live intraoperative video visualization. [11] Shortly after, laser capabilities were incorporated into ocular endoscopes.[12] Since then, the ophthalmic endoscope has undergone multiple iterations and improvements in the camera, illumination, and laser source.[13]

Instrumentation

A complete ophthalmic endoscopy system is a multi-component platform rather than a single instrument. Its essential elements are:

  • Intraocular endoscope probe which carries imaging, illumination, and video-processing components to the surgical field
  • A light source, either xenon or mercury-vapor, coupled to the illumination fiber
  • A camera/image sensor and video processor which convert the fiberoptic image to a digital signal.
  • A video monitor.
  • Laser fiber capable systems may use a visible aiming beam and an 810-nm diode treatment laser, allowing targeted photocoagulation under direct endoscopic visualization.

Because the endoscope is positioned within the eye, visualization is independent of the clarity of intervening ocular media and allows direct viewing of otherwise difficult-to-visualize structures. [14] However, current fiber-optic endoscopes generally provide a two-dimensional, nonstereoscopic image. Depth is therefore estimated using monocular cues such as tissue size and motion parallax, contributing to a learning curve for intraocular orientation and depth perception. [3]

Rigid Versus Flexible Designs

Endoscopic probes are available in different diameters and straight or curved configurations. Larger probes generally accommodate more optical fibers, providing higher image resolution and a wider field of view, whereas smaller-gauge probes permit smaller surgical incisions. [4][14]Probe position and working distance can be adjusted to alter the viewing angle, magnification, and field of view.

Illumination and Light Sources

The endoscope's coaxial (reflected) light is delivered along the same axis as the imaging fiber, which is what allows visualization directly across an opaque anterior segment and of surfaces oriented away from the microscope. Xenon and mercury-vapor sources are typical, and endoillumination generally must be balanced against phototoxicity and the use of light filters and chromovitrectomy dyes in modern practice.[15]

Indications

Media Opacity and Ocular Trauma

Ocular endoscopy is best known for providing adequate visualization of the posterior segment in the presence of media opacities such as corneal scars, corneal edema, band keratopathy, dense cataracts, hypopyon, prosthetic cornea/iris, or hyphema. [4] Recognized sequelae of open globe injuries include corneal edema, scarring, or blood in the anterior chamber, making vitrectomy nearly impossible.[16] Without the use of an ocular endoscope, surgeons are left with two options: Temporary keratoprosthesis (TKP) plus vitrectomy, or delaying surgery until visualization is a suitable option.  TKP is quite invasive and requires coordination of multiple surgeons. A group out of Walter Reed National Military Medical Center compared TKP and endoscopy, finding that both had similar functional success but endoscopy allowed earlier diagnosis and treatment, as well as overall fewer procedures than TKP. [17]

Delaying Intraocular foreign body (IOFB) removal can lead to higher rates of proliferative vitreoretinopathy (PVR) and consequently tractional/recurrent retinal detachments, as well as increased risk of infectious endophthalmitis. [18]A prospective study in 2012 with 11 eyes that had open globe injuries with IOFB used ocular endoscopy instead of delaying surgery, minimizing the theoretical risk of severe proliferative vitreoretinopathy. [19]

Endophthalmitis

Management of severe endophthalmitis often requires vitrectomy for physical debridement in conjunction with intravitreal antibiotics. [20] [21] In severe endophthalmitis, corneal edema, hypopyon, fibrin, and dense vitritis frequently limit the view through the operating microscope. The endoscope bypasses these opaque anterior media because it delivers the light source and camera directly into the vitreous cavity.[22][23]

Although current evidence for use of endoscopy in the setting of endophthalmitis is limited to small retrospective studies, globe salvage seems to be a consistent benefit. [24] [16] Corneal involvement in endophthalmitis is a known risk factor for increased risk of evisceration, with rates varying from 21-70%. [25] [26][27][28]In a 2019 study by Dave et al. of 33 eyes managed with ocular endoscopy in the setting of endophthalmitis, the evisceration rate was only 3.03%. The study noted that endoscopy allowed for earlier intervention, controlling infection before evisceration was necessitated. [29]A subsequent study from Dave and colleagues further supported reduced evisceration rates, with 14.28% of eyes progressing to phthisis. [30]

Visual outcomes remain modest[29] [24], but enrolled eyes have baseline poor vision [31] , suggesting non-inferiority of the technique, although there are no randomized comparisons against conventional vitrectomy. De Smet & Carlborg indicated that visual prognosis with endoscopy depended on presenting visual acuity and retinal appearance visualized at the time of surgery. [32]

Neovascular and Refractory Glaucoma

Endoscopic cyclophotocoagulation (ECP) is the core role of ocular endoscopy in neovascular (NVG) and refractory glaucoma by directly visualize and ablate the ciliary processes, reducing aqueous humor production and lowering intraocular pressure (IOP). [33][34] There are advantages of this process over transscleral cyclophotocoagulation such as direct visualization of the ciliary body, lower rates of complications associated with non-visualized cyclodestruction. [35]

Pediatric Vitreoretinal Disease

Due to the improved visualization of the anterior retina, pars plicata, and retrolental space, ocular endoscopy has been utilized in pediatrics. Pediatric retinal diseases such as retinopathy of prematurity tractional retinal detachments (ROP TRD), familial exudative vitreoretinopathy (FEVR), and persistent fetal vasculature (PFV) frequently have anterior pathology that would be difficult to view using a regular microscope viewing system.[36] The rate of primary lensectomy, a known complication of ROP TRD repairs, was dramatically reduced with the use of an endoscope in a UK preliminary observational study.[37]

In addition to anterior pathology being highly common in pediatric retinal disease, particularly retinopathy of prematurity, the pediatric vitreous cavity is about 20% the size of an adult vitreous cavity.  [36]These two factors result in a higher risk of intraoperative lenticular and retinal trauma. Endoscopy, which allows for better visualization, theoretically decreases this risk.

Surgical Technique and Pearls

Advantages

Limitations and Disadvantages

Complications

References

  1. ↑ 1.0 1.1 Thorpe HE. Ocular endoscope: an instrument for the removal of intravitreous nonmagnetic foreign bodies. Trans Am Acad Ophthalmol 1934; 39:422
  2. ↑ 2.0 2.1 2.2 Wong SC, Lee TC, Heier JS, Ho AC. Endoscopic vitrectomy. Curr Opin Ophthalmol. 2014 May;25(3):195-206. doi: 10.1097/ICU.0000000000000052. PMID: 24713607.
  3. ↑ 3.0 3.1 3.2 3.3 Lai FHP, Wong EWN, Lam WC, Lee TC, Wong SC, Nagiel A, Lam RF. Endoscopic vitreoretinal surgery: Review of current applications and future trends. Surv Ophthalmol. 2021 Mar-Apr;66(2):198-212. doi: 10.1016/j.survophthal.2020.11.004. Epub 2020 Dec 3. PMID: 33278403.
  4. ↑ 4.0 4.1 4.2 Dave VP, Tyagi M, Narayanan R, Pappuru RR. Intraocular endoscopy: A review. Indian J Ophthalmol. 2021 Jan;69(1):14-25. doi: 10.4103/ijo.IJO_1029_20. PMID: 33323565; PMCID: PMC7926106.
  5. ↑ Koch FH, Luloh KP, Augustin AJ, el Agha MS, Guembel H, Ohrloff C, Grizzard WS, Hammer ME, Sinclair S. Subretinal microsurgery with gradient index endoscopes. Ophthalmologica. 1997;211(5):283-7. doi: 10.1159/000310809. PMID: 9286802
  6. ↑ Němcová Š, Čáp J. Mechanically loaded GRIN lens for endoscopy. Opt Express. 2023 Apr 10;31(8):13096-13103. doi: 10.1364/OE.485554. PMID: 37157455.
  7. ↑ Marra KV, Yonekawa Y, Papakostas TD, Arroyo JG. Indications and techniques of endoscope assisted vitrectomy. J Ophthalmic Vis Res. 2013 Jul;8(3):282-90. PMID: 24349675; PMCID: PMC3853791.
  8. ↑ Norris, John L., and Gilbert W. Cleasby. “An Endoscope for Ophthalmology.” American Journal of Ophthalmology [United States], vol. 85, no. 3, March 1978, pp. 420–22, https://doi.org/10.1016/S0002-9394(14)77741-4.
  9. ↑ Norris JL, Cleasby GW, Nakanishi AS, Martin LJ. Intraocular endoscopic surgery. Am J Ophthalmol. 1981;91:603–606. doi: 10.1016/0002-9394(81)90058-1
  10. ↑ Volkov, Veniamin V., et al. “Flexible Endoscope for Intraocular Surgery.” Archives of Ophthalmology (1960) [Chicago, IL], vol. 108, no. 7, July 1990, pp. 1037–38, https://doi.org/10.1001/archopht.1990.01070090139057.
  11. ↑ Eguchi, Shuichiro, and Makoto Araie. “A New Ophthalmic Electronic Videoendoscope System for Intraocular Surgery.” Archives of Ophthalmology (1960) [Chicago, IL], vol. 108, no. 12, December 1990, pp. 1778–81, https://doi.org/10.1001/archopht.1990.01070140132046.
  12. ↑ Uram, Martin. “Ophthalmic Laser Microendoscope Endophotocoagulation.” Ophthalmology (Rochester, Minn.) [United States], vol. 99, no. 12, December 1992, pp. 1829–32, https://doi.org/10.1016/S0161-6420(92)31717-8.
  13. ↑ Marra KV, Yonekawa Y, Papakostas TD, Arroyo JG. Indications and techniques of endoscope assisted vitrectomy. J Ophthalmic Vis Res. 2013 Jul;8(3):282-90. PMID: 24349675; PMCID: PMC3853791.
  14. ↑ 14.0 14.1 Ajlan RS, Desai AA, Mainster MA. Endoscopic vitreoretinal surgery: principles, applications and new directions. Int J Retina Vitreous. 2019 Jun 18;5:15. doi: 10.1186/s40942-019-0165-z. PMID: 31236288; PMCID: PMC6580629.
  15. ↑ Sadeghi, E., Mohan, S., Iannetta, D., & Chhablani, J. (2023). Recent developments in imaging and surgical vision technologies currently available for improving vitreoretinal surgery: a narrative review. Expert Review of Medical Devices, 20(8), 651–672. https://doi.org/10.1080/17434440.2023.2231841
  16. ↑ 16.0 16.1 Dave VP, Chakurkar R, Tyagi M, Narayanan R, Pappuru RR. Intraocular endoscopy in the management of ocular trauma: clinical settings and treatment outcomes at a tertiary eye care centre. Eye (Lond). 2021 Jul;35(7):1904-1908. doi: 10.1038/s41433-020-01179-1. Epub 2020 Sep 11. PMID: 32918042; PMCID: PMC8225868.
  17. ↑ Chun DW, Colyer MH, Wroblewski KJ. Visual and anatomic outcomes of vitrectomy with temporary keratoprosthesis or endoscopy in ocular trauma with opaque cornea. Ophthalmic Surg Lasers Imaging. 2012 Jul 1;43(4):302-10. doi: 10.3928/15428877-20120618-09. PMID: 22788582.
  18. ↑ Jonas JB, Budde WM. Early versus late removal of retained intraocular foreign bodies. Retina. 1999;19(3):193-7. doi: 10.1097/00006982-199905000-00003. PMID: 10380023.
  19. ↑ Sabti KA, Raizada S. Endoscope-assisted pars plana vitrectomy in severe ocular trauma. Br J Ophthalmol. 2012 Nov;96(11):1399-403. doi: 10.1136/bjophthalmol-2012-302187. Epub 2012 Sep 5. PMID: 22952401.
  20. ↑ Durand, M. L., Barshak, M. B., & Sobrin, L. (2023). Eye Infections. The New England Journal of Medicine, 389(25), 2363-2375. https://doi.org/10.1056/NEJMra2216081
  21. ↑ Durand ML. 2017. Bacterial and Fungal Endophthalmitis. Clin Microbiol Rev 30:.https://doi.org/10.1128/cmr.00113-16
  22. ↑ M.D. De Smet, E.A. Carlborg Managing severe endophthalmitis with the use of an endoscope Retina, 25 (2005), pp. 976-980
  23. ↑ Q. Pan, Y. Liu, R. Wang, et al. Treatment of Bacillus cereus endophthalmitis with endoscopy-assisted vitrectomy Medicine (Baltimore), 96 (2017), p. e8701
  24. ↑ 24.0 24.1 Ren H, Jiang R, Xu G, Chang Q, Lv J, Chen Q, Wang W. Endoscopy-assisted vitrectomy for treatment of severe endophthalmitis with retinal detachment. Graefes Arch Clin Exp Ophthalmol. 2013 Jul;251(7):1797-800. doi: 10.1007/s00417-013-2297-4. Epub 2013 Mar 13. PMID: 23512620.
  25. ↑ O’Neill EC, Yeoh J, Fabinyi DC, et al. Risk factors, microbial profiles and prognosis of microbial keratitis-associated endophthalmitis in high-risk eyes. Graefes Arch Clin Exp Ophthalmol. 2014;252(9):1457–1462.
  26. ↑ Scott IU, Flynn HW, Feuer W, et al. Endophthalmitis associated with microbial keratitis. Ophthalmology. 1996;103(11):1864–1870.
  27. ↑ Infectious Keratitis Progressing to Endophthalmitis: A 15-Year Study of Microbiology, Associated Factors, and Clinical Outcomes. Ophthalmology. 2012. Henry CR, Flynn HW, Miller D, Forster RK, Alfonso EC.
  28. ↑ Epidemiology of Keratitis/Scleritis-Related Endophthalmitis in a University Hospital in Thailand. Scientific Reports. 2021. Dhirachaikulpanich D, Soraprajum K, Boonsopon S, et al.
  29. ↑ 29.0 29.1 Dave VP, Pappuru RR, Tyagi M, Pathengay A, Das T. Endoscopic vitrectomy in endophthalmitis: initial experience of 33 cases at a tertiary eye care center. Clin Ophthalmol. 2019 Feb 5;13:243-251. doi: 10.2147/OPTH.S185716. PMID: 30787589; PMCID: PMC6368127.
  30. ↑ Dave VP, Pappuru RR, Khader MA, Basu S, Tyagi M, Pathengay A. Endophthalmitis with opaque cornea managed with primary endoscopic vitrectomy and secondary keratoplasty: Presentations and outcomes. Indian J Ophthalmol. 2020 Aug;68(8):1587-1592. doi: 10.4103/ijo.IJO_1840_19. PMID: 32709783; PMCID: PMC7640882.
  31. ↑ Chen X, Zha Y, Du S, Yang X. Timely Use of Conventional Vitrectomy and Endoscope-Assisted Vitrectomy for Endophthalmitis Following Open Ocular Trauma: A Retrospective Study of 18 Patients. Med Sci Monit. 2019 Nov 16;25:8628-8636. doi: 10.12659/MSM.918017. PMID: 31732711; PMCID: PMC6874835.
  32. ↑ De Smet MD, Carlborg EA. Managing severe endophthalmitis with the use of an endoscope. Retina. 2005 Dec;25(8):976-80. doi: 10.1097/00006982-200512000-00004. PMID: 16340526.
  33. ↑ Gedde S, Bowden E, Challa P ... Primary Open-Angle Glaucoma Preferred Practice Pattern® Ophthalmology, 2026; 133, P1-P103
  34. ↑ Tóth M, Shah A, Hu K, Bunce C, Gazzard G. Endoscopic cyclophotocoagulation (ECP) for open angle glaucoma and primary angle closure. Cochrane Database of Systematic Reviews 2019, Issue 2. Art. No.: CD012741. DOI: 10.1002/14651858.CD012741.pub2. Accessed 27 August 2026.
  35. ↑ Chen MF, Kim CH, Coleman AL. Cyclodestructive procedures for refractory glaucoma. Cochrane Database of Systematic Reviews 2019, Issue 3. Art. No.: CD012223. DOI: 10.1002/14651858.CD012223.pub2.
  36. ↑ 36.0 36.1 Yeo, Damien C. M., et al. “Endoscopy for Pediatric Retinal Disease.” Asia-Pacific Journal of Ophthalmology (Philadelphia, Pa.) [United States], vol. 7, no. 3, May 2018, pp. 200–07, https://doi.org/10.22608/APO.2018154.
  37. ↑ Wong, C., et al. “013 Acute Retinal Detachment in Retinopathy of Prematurity (ROP-RD): UK National Outcomes of Endoscopic Vitrectomy in 51 Consecutive Cases.” Archives of Disease in Childhood [London], vol. 103, no. Suppl 2, December 2018, pp. A6–A6, https://doi.org/10.1136/goshabs.13.
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