Microscope-integrated OCT assists intrascleral haptic fixation

Real-time images can improve preoperative planning, intraoperative profile and postoperative management of ISHF.

Issue: December 10, 2020

ByRinky Agarwal, MD, DNB

ByNamrata Sharma, MD, DNB, MNAMS

Intrascleral haptic fixation has taken the world by storm since Gabor Scharioth started performing it in 2006.

In 2007, glued IOL took intrascleral haptic fixation (ISHF) even further. This was followed by Shin Yamane creating the flange technique and Sergio Canabrava modifying the flanges to the sutures. There have been so many pioneers who have made ISHF a reality and taken it to where it is today.

Amar Agarwal

We have published our work in Journal of Cataract and Refractive Surgery on a 12-year study of glued IOL. This is the longest follow-up of glued IOL, and it shows a microtilt of less than 1° as examined on anterior segment OCT. This is one of the biggest advantages of glued IOL as a bad tilt can negate all of the advantages of a surgery. Intraoperative-assisted OCT helps make ISHF more predictable and safe.

The guests in this column are Rinky Agarwal, MD, DNB, MNAMS, and Namrata Sharma, MD, DNB, MNAMS, of Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi.

Amar Agarwal, MS, FRCS, FRCOphth
OSN Complications Consult Editor

Intrascleral haptic fixation (ISHF) of an IOL is a well-established, safe and effective method of optical rehabilitation of aphakia in individuals with deficient capsular support. In this technique, a routinely in-the-sulcus implanted posterior chamber IOL is fixed to the sclera for enhanced support and stability. Microscope-integrated intraoperative OCT (iOCT) is a recently introduced noninvasive noncontact modality for transsurgical objective imaging of intraocular architecture. The apparatus has an incorporated OCT unit with a heads-up display system that provides real-time dynamic feedback on anatomic specifics and ocular structure-instrument interaction during surgical maneuvering. These high-resolution OCT scans are known to enhance anatomical and visual outcomes of various anterior and posterior segment surgeries.

We discuss our experience with iOCT-guided ISHF and firmly believe that, akin to other lamellar corneal surgeries, this apparatus can aid in flattening the learning curve of ISHF (Figures 1 to 6).

Figure 1. iOCT-assisted visualization of partial-thickness scleral incisions.

*Source: Rinky Agarwal, MD, DNB, MNAMS, and Namrata Sharma, MD, DNB, MNAM*

Figure 2. Microcrescent blade seen as hyperreflective structure with hyporeflective core. The dissected scleral depth roughly corresponds to 50% of scleral thickness.

Preoperative decision-making

iOCT-based magnified imaging of 360° retropupillary structures aids in establishing the adequacy as well as the thickness and stability of the residual capsular rim without compromising surgical sterility. This can guide appropriate surgical planning such as one-sided or two-sided ISHF or sulcus placement of the IOL. Scleral integrity and thickness ascertained by the equipment facilitates selection of appropriate surgical technique for ISHF. For example, in the presence of scleral thinning and conjunctival fibrosis, we prefer needle-based procedures to avoid unnecessary soft tissue manipulation.

iOCT-assisted morphological evaluation of scleral health, site, size, integrity and amount of gaping of previous corneal wounds, and white-to-white diameter helps the surgeon in deciding on vertical or horizontal fixation of the IOL. Vivid visualization of anterior chamber anatomy, the extent of the iris defects, and the thickness and mobility of the residual iris enable concomitant procedures such as synechiolysis and pupilloplasty. Occasionally, the modality may depict presence of vitreous strands in the anterior chamber, thereby favoring adequate vitrectomy. iOCT-guided simultaneous assessment of corneal thickness and clarity also allows future planning for keratoplasty. All of these details are particularly beneficial in uncooperative individuals, children, or cases with decompensated/scarred corneas and non-dilating pupil.

Figure 3. Direct visualization of partial-thickness scleral incisions with and without shadowing effect of the overlying instrument.

Figure 4. Microcrescent blade and its relationship with the anterior sclera minimally affected by the metallic composition of the instrument.

Intraoperative utility

Two major techniques of haptic exteriorization during ISHF include the handshake technique and needle-assisted exteriorization. Once exteriorized, the haptics can be either tucked in scleral tunnels or cauterized to form a self-retaining flange/bulb.

Premature scleral entry with the advancing end of sharp metallic instruments used in both techniques may jeopardize further dissection due to sudden unanticipated hypotony. Use of iOCT during these steps constantly guides the precise depth, position and tract of the microcrescent blade or needle. The scleral incision is visualized as a hyporeflective dip in the anterior hyperreflective sclera, and the metallic instrument can be appreciated as a hyperreflective structure with a hyporeflective core. This type of dynamic feedback converts unpredictable blind dissection to a directly scrutinized surgeon-controlled procedure. This appropriately guides attainment of the desired 50% depth while fashioning partial-thickness scleral flaps and tunnels. Proper depth assessment during scleral dissection is important to evade a choroidal detachment, suprachoroidal hemorrhage, or inflated uveal inflammation associated with a deep dissection and haptic exposure encountered with a superficial dissection. Determination of the exact length and width of the scleral tunnel aids in guiding the most appropriate site of sclerotomy, thereby avoiding haptic slippage intraoperatively and IOL tilt or dislocation postoperatively.

Once exteriorized, the haptics are appreciated as a hyperreflective dot in the surrounding hyporeflective scleral tunnel. Detection of any abnormality in their intrascleral tract and angulation on iOCT suggests undue torque on them, and immediate corrective maneuvers may be undertaken accordingly to correct it. Direct imaging of presence of haptics in the scleral tunnel marks the surgical endpoint, while their absence favors inadvertent slippage and deems instantaneous resumption exercises. iOCT-assisted accurate measurement of the size of the flanged haptic, proportion of intrascleral haptic tuck, fine IOL tilt and pseudophakodonesis, findings easily missed on conventional microscopic examination, enables better centration of the IOL. The adequacy of stromal wound hydration and apposition of the scleral, corneal and conjunctival incisions can be established by iOCT at the end of the procedure and tends to decrease the incidence of postoperative wound leak.

Figure 5. Exteriorized haptic visualized well as a hyperreflective tube-like structure on iOCT.

Figure 6. The presence of a well-tucked IOP haptic marks the endpoint of surgery in glued IOL technique. The haptic is appreciated as a round hyperreflective dot in the top cross section and an oblique tube-like structure in the bottom cross section. Presence of a well-tucked haptic rules out its accidental intraocular slippage.

Postoperative phase

The presence and severity of untoward and unexpected postoperative complications such as scleral bleb, scleral melt, haptic exposure, pseudophakodonesis and IOL tilt can be assessed aptly by iOCT, thus helping in choosing the most appropriate rescue procedure. For example, autologous scleral patch grafts for the former three complications are best performed in eyes with surrounding healthy sclera. In noncompliant individuals, individuals who have difficulty with sitting position and children, this may prevent the need for prolonged or repeated corrective procedures.

Limitations

Despite its inherent advantages, widespread use of iOCT is hindered by factors such as its high cost, limited availability, shadowing effect of overlying metallic instruments and repeated necessity to halt the surgery for changing its mode. However, with further refinements in OCT-compatible instrumentation, a new dimension to this technology is expected in the future.

Conclusion

Real-time images delivered by iOCT can improve preoperative planning, intraoperative profile and postoperative management of ISHF. This may be indirectly reflected in its anatomical and visual outcomes. Visualization of minute surgical details and titrated manipulation of ocular structures may shorten the learning curve of novice surgeons by facilitating their judgment, technique and knowledge about the procedure. Continuous video monitoring and recording feature of this instrument can be effectively used for reviewing critical surgical steps later. However, larger long-term studies establishing its concrete role during ISHF are yet awaited.

References:
Agarwal A, et al. J Cataract Refract Surg. 2008;doi:10.1016/j.jcrs.2008.04.040.
Agarwal R, et al. Clin Exp Ophthalmol. 2020;doi:10.1111/ceo.13862.
Narang P, et al. J Cataract Refract Surg. 2019;doi:10.1016/j.jcrs.2018.11.036.
Sharma N, et al. Am J Ophthalmol. 2020;doi:10.1016/j.ajo.2020.07.048.
Yamane S, et al. Ophthalmology. 2017;doi:10.1016/j.ophtha.2017.03.036.

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Edited by Amar Agarwal, MS, FRCS, FRCOphth, director of Dr. Agarwal’s Eye Hospital and Eye Research Centre. Agarwal is the author of several books published by SLACK Incorporated, publisher of Ocular Surgery News, including Phaco Nightmares: Conquering Cataract Catastrophes, Bimanual Phaco: Mastering the Phakonit/MICS Technique, Dry Eye: A Practical Guide to Ocular Surface Disorders and Stem Cell Surgery and Presbyopia: A Surgical Textbook. He can be reached at 19 Cathedral Road, Chennai 600 086, India; email: aehl19c@gmail.com; website: www.dragarwal.com.
Namrata Sharma, MD, DNB, MNAMS, can be reached at Dr. Rajendra Prasad Centre for Ophthalmic Sciences, AIIMS, New Delhi, India; email: namrata.sharma@gmail.com.

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Disclosures: The authors report no relevant financial disclosures.

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