This article will describe a new method of achieving a painless and highly effective eye ball fixation technique for performing clear corneal phacoemulsification and Limbal relaxing incisions (LRI) under topical anaesthesia . The Corneal Pocket Fixation incision (CPFI) will provide good tangential fixation and counter traction for the creation of both the clear corneal side port, and the main port incisions. It is also highly effective in establishing a non rotatory fixation for performing Limbal relaxing incisions, Key Words: eyeball fixation; corneal pocket fixation incision; tangential eyeball fixations.
Achieving a good fixation of the eye ball while executing the main port and the side port incisions during phacoemulsification is crucial especially when the patient is being operated upon under topical anaesthesia. Likewise a firm fixation, which will prevent rotational movement of the eye ball is necessary to perform limbal relaxing incisions (LRI) under topical anaesthesia.(ref.1)
The Corneal Pocket Fixation Incision (CPFI) is a method of achieving eyeball fixation through a partial thickness blind corneal pocket and a hooking instrument like a fine iris repositor.Unlike conventional fixation techniques in which the hold of the fixation instrument is perpendicular to the ocular surface with the exertion of a posterior pressure, to grasp the ocular surface, the CPFI achieves fixation with a tangential hold on the eyeball without exerting any form of posterior pressure on the eyemaball.
Surgical Technique:
The corneal pocket incision is fashioned with a 23 G angled MVR blade by creating a
partial thickness blind corneal pocket, tangential to the limbus at 5.0 o clock and 7.0 o clock
positions. (Fig 1A & 1B). The 23.0G MVR blade is held tangential to the limbus at 5.0 or 7.0
o clock positions and passed into the clear cornea just like one would do to create the shelving
incision required to insert an AC maintainer. However the MVR blade stops blindly in the corneal stroma, without entering the eye. The length of the pocket incision is about 1.0 clock hour. The longer the pocket incision the stronger will be the hold. The fixation is achieved by hooking a slim iris repositor through the corneal pocket and thereby creating a firm tangential hold. This tangential hold prevents torsional rotation of the eye ball. Unlike conventional fixation techniques like that performed with the toothed forceps, the hold from the corneal pocket incision is tangential to the limbus. Since its manipulation is in the same plane and is very similar to the passage and manipulation of the side port instruments and the phaco probe within the eye, the technique can be learnt easily with a very short learning curve.
Once made the 7 o clock CPFI is engaged with an iris repositor to provide fixation and counter traction for the side port incision at the 2 o clock position.(Fig. 3A & 3B). In a similar fashion the 5 o clock CPFI is engaged to made the clear corneal main port incision at the 10 o clock position.(Fig 2A & 2B). The 5.0 o clock CPFI is then engaged with the left hand to fixate the eye in order to carry out the various manoeuvres like capsulorrhexis, hydrodissection and/or hydrodelamination , insertion of the phacoemusification hand piece and the Coaxial I.A probe and also for the Intra ocular lens insertion. If Limbal relaxing incisions are to be made the CPFIs are constructed such that the relaxing incisions do not traverse the pocket incisions. For ATR astigmatism, if the paired 5mm LRIs need to be done astride the 180 deg. meridian, the CPFIs are made at 5.0 o clock and 7.0 o clock positions.(Fig 4A & 4B). Likewise for superior and inferior LRIs for WTR astigmatism straddling the 90 deg meridian, the CPFIs are made at the 3.0 o clock and 9.0 o clock positions.
Discussion
Both phaco surgeons and patients alike seem to prefer surgery under topical anaesthesia, as its has proven to be painless , aesthetic and has the advantage of quick rehabilitation of vision as the eye patch can be done away with.(ref.6) However in certain sensitive patients as well as those with a prominent bell’s phenomenon and in patient requiring Limbal relaxing incisions (LRI), a painless way of achieving eye ball fixation is mandatory. The modalities of globe fixation available today are:
- Toothed forceps:- like the St.Martin’s or the Lim’s forceps may be used to ensure fixation by holding it firmly at the limbus, diametrically opposite the site of incision. (ref 4)However under topical anaesthesia this could prove to be painful. In addition movements of the eye ball or a prominent bell’s phenomenon which can occur under topical anaesthesia can cause the conjunctiva to tear or produce petechial haemorrhages. The toothed forceps fixation is also not ideal for performing LRI as it does not prevent torsional rotation of the eye ball, due to a single point of fixation.
- Cotton bud:- some surgeons use the cotton bud for counter traction and fixation. This method of fixation is weak and the bud tends to slip if the ocular surface is moist.
- The Thornton fixation ring:- is too traumatic to use under topical anaesthesia.
(ref 2,3)This fixation method prevents torsional eye ball rotation and is best suited for
performing Limbal Relaxing Incisions, however the multiple sharp engaging teeth of the
device will induce pain, when used under topical anaesthesia - Fixation through side port incision: some surgeons steady the eye ball by passing an
Iris repositor or a rod like device through the side port incision to steady the eyeball while
making the main port clear corneal incision. (ref 5). This method of fixation in not ideal
as it may cause the viscoelastic material to leak out, leading to progressive hypotony which
may result in an improperly constructed clear corneal incision.
The ‘Corneal Pocket fixation incision’ (CPFI) has the distinct advantage that it is painless , and because of the tangential orientation of the hold, it is firm and prevent torsional rotation of the eye ball, which is ideally suited for performing LRI. Because of the firm hold afforded by the pocket incision it can steady the eye ball even in the presence of a robust bell’s phenomenon.
The Corneal pocket fixation incision induces no corneal astigmatism, completely seals up and is virtually undetectable by the 1st post operative day and even in the event of an inadvertent entry into the anterior chamber, it is self sealing and requires no additional intervention. It can also be used as a fixation methodology in different types of ocular surgeries like ICL (implantable collamer lens), SICS ,Trabeculectomy etc…
The Corneal pocket fixation incision works very well with topical anaesthesia. It has a very small learning curve as all of us are well versed with making shelving clear corneal main port and side port tunnel incisions. Since the smooth flat Iris Repositor is used to hook the shallow corneal pocket there is minimal trauma to the corneal or ocular tissues.When mastered the corneal pocket fixation incision is simply the most elegant and effective way to achieve globe fixation for intra ocular surgery.
Author
Prof.S.Venkatesh MS,FRCS.Dnb,FICO
H.O.D Dept of ophthalmology
Shri Sathya Sai Medical College & R.I.