Ординатура / Офтальмология / Английские материалы / Small Incision Cataract Surgery (Manual Phaco)_Singh_2002

Fig. 33.6: Small posterior capsular suplure with no disturbance of anterior hyaloid face in the bag implantation can be done

POSTOPERATIVE COMPLICATIONS

•Shallow AC It can be seen if the surgeon has not tested the corneal valve by depressing the upper sclera behind the incision. This complication can be tackled by applying a suture and reviewing the wound. If postoperatively chamber is shallow the patient should be taken to operation theatre for re-suturing.

•Corneal Oedema Postoperative corneal oedema is usually transient. It disappears in 2-3 days. If it does

not, then hypertonic saline should be added to the treatment regimen.

•Endophthalmitis

•Posterior capsular opacification

Table 33.1: Author’s experience with complications in 250 consecutive patients including initial cases:

FURTHER READING

1.Drews RC: Management of complications during posterior chamber implantation. Implants in Ophthalmology 2: 17576,1998.

2.Skuta GL et al: Zonular dialysis during extracapsular cataract extraction in pseudoexfoliation syndrome. Arch Ophthalmol 105: 632-34, 1987.

3.Ulreche Demeler Management of intraoperative complications. In Piers Percival (Ed): A Colour Atlas of Lens Implantation Wolfe Publishing Ltd: 1991.

4.Shah Anil: Complications in Small Incision Cataract Surgery

Bhalani Publishing House, India: 2000.

5.Duch Mestres: Intraoperative complications of ECCE/SICS J Cat Ref Surg 25: 1275-79, 1999.

Management 34

of Posteriorly

Dislocated Lenses

Lalit Verma

PVenkatesh HK Tiwari

The aim of every cataract surgeon is to ensure a safe removal of the cataractous lens. In addition there is an overpowering desire by the patient to

be rehabilitated early. This is matched by an equally sincere effort by the surgeon to provide the same. Sometimes, however, the surgeon encounters a scenario of having either the crystalline lens or pseudophakos dislocated posteriorly into the vitreous. This undesirable situation may occur during conventional cataract surgery as well as phacoemulsification. Such a mishap not only compromises restoration of the patient’s vision but also the surgeon’s confidence, particularly so in the case of novice surgeons. Today however, the surgeon may take solace in the fact that the situation is not beyond salvage if the management is appropriately planned. Planning must be individualised taking several factors into consideration such as the following questions: What happens if the dislocated components are left to stay? Is prognosis affected? When must one intervene? Who should intervene and how?

Clinical Situations

Broadly, posteriorly dislocated crystalline lens or a pseudophakos can have a typical or an atypical presentation, an immediate or delayed presentation and an uncomplicated or complicated presentation (Chart 34.1). In a typical case the history itself is diagnostic. Atypical cases are those in which a history is lacking and the patient presents with features of “endophthalmitis” (read case 1), vitreous hemorrhage or other complications such as “aphakic glaucoma” (read case 2). Another atypical presentation is a patient with an anterior chamber IOL found alongwith a dislocated posterior chamber IOL (often detected incidentally). This latter situation we designate as a new entity called the “Double IOL syndrome” (read case 3). Only a thorough clinical evaluation and

also a degree of suspicion can identify the atypical cases. The following three case descriptions as encountered by us highlight these atypical presentations.

Immediate Delayed

Chart 34.1: Presentation in sunk phakos and pseudophakos

Case 1: Endophthalmitis

An elderly male with a subluxated lens was meant to undergo an intracapsular cataract surgery. His discharge summary read “OD/OS ICCE done”. This patient presented to the emergency on the third postoperative day with features of endophthalmitis. Indirect ophthalmoscopy was not performed. Ultrasonography reported the presence of focal low to medium reflectivity lesion, as possible exudates due to the presence of other point like and pseudomembranous vitreous opacities. Indirect ophthalmoscopy done at a later date however, revealed a dislocated lens. Evidently this had been fallaciously interpreted by USG as possible exudates. The short coming here was an incomplete discharge summary but complete clinical evaluation.

Case 2: Aphakic Glaucoma

This was again a male patient. He was being managed as a case of aphakic glaucoma. Fundus could not be visualised due to a small pupil with synechiae and media opacification. A careful history was re-elicited and this

pointed towards the possibility of an attempt at implantation having been made. In this case ultrasonography was conclusive in that a dislocated IOL was identified in the inferior vitreous. This case emphasises the need to approach some atypical cases with a degree of suspicion.

Case 3: The Double IOL Syndrome

We had a patient referred to our retina services with a diagnosis of pseudophakos (AC-IOL) with retinal detachment. During a repeat indirect ophthalmoscopy in the clinic a posteriorly dislocated PC IOL was detected. Conventional retinal detachment (RD) surgery was planned in this patient with the double IOL syndrome for two reasons -firstly the posteriorly dislocated IOL was relatively fixed and secondly, removal of the PC IOL following a vitreoretinal surgery would entail more significant anterior segment trauma because of the AC IOL.

An immediate or delayed presentation in such cases has a bearing not only on the visual prognosis but also on the surgical plan. In those presenting early, the surgeon will have to specially consider the corneoscleral incision parameters. A large or small section, the wound architecture and wound integrity will have a bearing on the surgical approach.

Any nucleus or artiphakia dislocated posteriorly and associated with the following, either singly or in combination falls into the complicated category (Chart 34.2). The complications could be vitreous haemorrhage, retinal detachment, severe inflammatory reaction, glaucoma or the double IOL syndrome. In cases with retinal detachment distinction has to be made as to its relation with the dislocated lens. The answer to the question “is the IOL directly responsible for the RD”? will determine the surgical approach in some cases. (case 4) Patients with a dislocated IOL of longstanding duration and one that is fixed by fibrosis and without the above mentioned complications fall into an entirely separate category. All

Chart 34.2: The complicated dislocation

that these patients may need is a close follow-up and visual rehabilitation by contact lenses, spectacles or secondary AC-IOL. (creating a “double IOL” syndrome in a relatively “safe” eye) depending on the compatibility of the ocular structures (e.g. angle) and fellow eye status.

Case 4: Is IOL Directly Responsible for the RD?

We had a patient with subtotal retinal detachment, a welldefined primary break in the superotemporal quadrant and without PVR. In association with this was a not so easily discernible PC IOL dislocated into the anterior midvitreous inferiorly. As the retinal detachment did not appear to be directly related to the dislocated IOL a conventional RD surgery with subretinal fluid drainage was undertaken. The retina settled with an uneventful postoperative course. He had a best corrected visual acuity of 6/36. At a second stage, AC IOL implantation was undertaken as the dislocated IOL was “fixed”. Thereby a “double IOL” syndrome was created considering this eye to be relatively safe. Until the last follow-up he has had no complications and has retained 6/24 vision.

It is clearly self evident that with the possibility of the above enumerated complications a conservative approach to managing these cases is ill-suited in most. Preoperatively however, intraocular inflammation and raised intraocular pressure should be controlled by medical treatment.

Non-surgical management may be considered in a quiet eye with small retained lens fragments or wherein the entire lens with its capsule intact (as in couching) has dislocated. Time is a great healer in some patients who have less than one quarter of the lens material dislocated. This may be well tolerated and eventually may get resorbed after a variable length of time. Gilliland et al however, reported that even small fragments may be associated with significant macular oedema, persistent uveitis and glaucoma on long-term follow-up. A careful follow-up of such cases wherein conservative management has been planned is therefore important.

In all cases of dislocated lens or its fragments and in dislocated artiphakic lenses, the essential cause is a breach in the integrity of the capsular bag during several surgical steps ranging from capsulotomy, nucleus delivery or phacoemulsification to irrigation-aspiration of lens remnants. In a situation wherein the cataract surgeon sees a dislocating nucleus what should he do? when should he make an effort at removing it himself/herself and when should he take the expertise of a vitreoretinal surgeon?

The cataract surgeon may make an attempt at removal when the dislocated lens material is seen to be lying on

the anterior hyaloid membrane. In such cases use of lens loop, wire vectis and cryoprobe have been reported to be effective. Injection of visco-elastic posterior to nucleus can be tried with the aim of floating the nucleus anteriorly and removing it subsequently from the limbal section. Once the nucleus or lens remnants migrate posteriorly these methods rarely succeed and infact may worsen the situation. Panic attempts involving excessive surgical manipulation and invasion of the vitreous with scoops, cryoprobes or excessive irrigation only complicates things further. Associated with these manoeuvres may be subsequent retinal break formation and retinal detachment. The essence in preventing further complications is to the treat the vitreous with care. Mishandling this vital component leads to untold problems. It should never be pulled out, no matter how gently. The safest way of handling the vitreous is to cut, aspirate; cut and aspirate. Sponge and scissors vitrectomy is an unsafe method of approaching vitreous complication.

In the above scenario the cataract surgeon can perform a good anterior vitrectomy using not weck cell sponge and Vannas scissors but a functioning vitreous probe. The wound should be closed properly without any attempt at an intraocular implantation. Having done so the patient should be referred to a vitreoretinal surgeon. The other option is to let a vitreoretinal surgeon take over at the same sitting. The latter approach is possible only if a vitreoretinal surgeon is immediately available. All cataract surgeons would do well to have atleast a standby functioning vitrectomy set at hand (Chart 34.3).

Dislocating nucleus/fragment

Chart 34.3: Dislocating nucleus/fragment

Cases that have been referred for later surgery need to be carefully evaluated preoperatively. This would include determining the potential visual acuity of the involved eye and the fellow eye status. On this would depend the plan of visual rehabilitation. Wound architecture as well as integrity will determine the need

for its strengthening and preplanning any surgical incision that may need to be made while removing a large nucleus or IOL. Corneal endothelial cell count and gonioscopy would indicate if an AC IOL is going to be compatible if ever desired by the surgeon. Pupillary dilation should also be evaluated. Elevated intraocular pressure and inflammation should be controlled by medical treatment. The status of retina, the mobility or fixity of the dislocated component should be properly assessed. In the presence of an opaque media ultrasonography may help to localise, confirm or detect a retinal detachment. Bright flash ERG and VER may help in predicting status of retina and optic nerve conduction.

Having taken a decision to operate, the visual prognosis should be explained to the patient and an informed written consent obtained.

Surgical steps should be preplanned and modified as needed preoperatively. Factors to be considered during this planning process are the need for a preplaced corneoscleral groove, actual incision site taking astigmatism also into consideration. The nucleus density should be assessed if possible. The need for an encirclage and/or buckle placement as also that of a long-term vitreous substitute like silicone oil or gas should be assessed. A combined approach vitreous surgery may be safer in certain situations. The necessity of having to use perfluorocarbon liquids should also be pre-evaluated.

The subsequent approaches available to a vitreoretinal surgeon are many. The final approach would depend largely on the hardness of the dislocated nucleus and the individual surgeon’s preference and experience. (Chart 34.4) Simple pars plana vitrectomy with cutting and aspiration alone may suffice when the dislocated component is only cortical matter, a soft nucleus or a small nuclear piece. In the presence of a large nucleus resistant to cutting and aspiration the technique of impalement of nucleus using an MVR blade can be tried

PPV

Resistant nucleus identified

Impale with MVR blade

Endoilluminator acts as support

Tilt MVR knife with the impaled nucleus

into the anterior chamber

Can constrict pupil

(with Pilocarpine chelate)

Complete preplaced corneal groove (6-8 mm)

(by surgeon/assistant)

Express nucleus

Chart 34.5: Dislocated nucleus-surgical algorithm

successfully in significant percentage of cases (Chart 34.5). The disadvantages of this technique are probability of greater tissue trauma and the possibility of the impaled nucleus falling back into the vitreous. The use of perfluorocarbon liquids prevents this risk and reduces tissue trauma. Cost of PFCLs is an overbearing factor.

For removal of lost lens fragments Weinstein et al have reported a new surgical technique using the Machemer lens. In a recent report Rover claims good results of phacoemulsification in the mid-vitreous cavity for dislocated lenses in 15 patients. Phacoemulsification was preceded by pars plana vitrectomy. No perfluorocarbon liquids were used in the study. The author concludes that the procedure is safe and easy, has no retinal side effects and reduces the intraoperative risks of alternate methods by avoiding a large opening into the anterior chamber and ocular hypotony. The approach seems agressive and we advocate that extreme caution is necessary while performing phacoemulsification in the vitreous even by the most experienced surgeons.

In our experience the two approaches which can be employed successfully in patients with a dislocated nucleus are (1) Use of perfluorocarbon liquids (2) MVR blade impalement and delivery through the limbal route. About PFCLs, we again re-emphasise that although expensive, it makes surgery safer and causes less tissue trauma. It should be made use of wherever possible.

One sentence of caution: PFCL is no magic liquid, it makes surgery atraumatic and successful provided it is injected only after a thorough vitrectomy. PFCL should

never be injected without prior vitrectomy. A problem that may arise while using PFCL is entrapment of some nuclear remnants in the depths of the convex PFCL meniscus and the ocular coat anywhere around the periphery and beyond the surgeon’s view. In case of doubt gentle depression will make them evident, following which they can be removed. If this precaution is not undertaken the surgeon may be surprised to find a few remnants following PFCL removal and an unnecessary prolongation of surgical time ensues. Layering the PFCL above with visco-elastic has been reported to facilitate removal of such fragments trapped in the periphery.

The management of intraocular lenses dislocated into the vitreous cavity is different surgically from that described above for dislocated nucleus. Peroperative evaluation and surgical planning are however similar. In addition the surgeon should decide whether to explant the IOL and leave the eye aphakic to explant the dislocated IOL and replace a new PC IOL or AC IOL or to reimplant the same dislocated IOL. The latter can be achieved by placing the IOL onto the capsulolenticular remnants or by scleral fixation. Several methods of removing a dislocated implant have been described but central to all these is a good pars plana vitrectomy. Unlike in surgery for removing a dislocated nucleus, PFCL is not as indispensable during surgery for a dislocated IOL.

Three kinds of approaches to surgery for management of a dislocated IOL can be used. These are a limbal approach, a pars plana approach or a combined limbal and pars plana approach.

The limbal approach is to be preferred when the dislocated implant is in the anterior or mid-vitreous and easily visible under the microscope without the need for an endoilluminator. Pars plana approach is generally preferred when the luxated IOL is in the posterior vitreous cavity, is lying on the retinal surface or is associated with complications such as severe vitreous reaction, retinal detachment, etc.

In both approaches no effort should be made at pulling on the implant prematurely. A complete vitrectomy is a must even before trying to grip the IOL. Perilenticular adhesions have to be carefully cut with Vannas scissors (limbal approach) or intravitreal scissors or probe and the IOL dissected completely free. The free IOL can only then be safely picked up using intravitreal forceps or other less desirable methods like a modified iris hook, etc. It is better to grip the optic and push the IOL up rather than grip the haptic and pull on it. The latter approach risks

breakage of the haptic with the IOL subsequently falling back onto the retina. Here again use of PFCL makes surgery relatively safer by preventing this possibility.

To have the eye aphakic or implant the same or a new IOL will depend on factors previously discussed and also on those shown in Chart 34.6. Internal scleral fixation techniques described for reimplanting the dislocated IOL are time consuming and cause more tissue trauma in the learning phase at least. Chang and colleagues have devised a new 25-guage forceps that they found useful for anterior segment application during vitreous surgery. This forceps has a curved shaft, a tip with a distal platform for grasping a suture and a proximal groove for gripping a haptic. These forceps facilitate manipulations such as fastening a suture loop around a haptic, repositioning an intraocular lens at the ciliary sulcus or repairing inadvertent or pre-existing iridodialysis.

Use of PFCL becomes mandatory if proliferative vitreoretinopathy is present or the surgeon has decided to manage both the dislocated implant and retinal detachment or to reimplant the same lens.

Visual Prognosis

Several reports are available in literature that compare visual results with the timing of surgery. Gilliland et al did not find any statistical difference between the timing of vitrectomy and incidence of glaucoma. In contrast Fastenberg et al reported that delayed vitrectomy (9-50 days) was associated with a better visual acuity but an increased incidence of glaucoma.

Blodi and associates report that vitrectomy performed within 3 weeks of cataract surgery had a lower incidence of glaucoma, compared to that undertaken beyond 3 weeks (18 percent to 60 percent). In this study 63 percent of those subjected to early vitrectomy had a vision of 6/ 60 or better. All patients undergoing vitrectomy at later stage had a vision of only finger counting.

Kim et al in 1994 reported no significant difference in final visual acuity or incidence of glaucoma following early (within 7 days) and late vitrectomy groups. However, visual outcome was better and complications minimised when the case was immediately taken over by a vitreoretinal surgeon. Seventy-five percent of such

patients had a visual acuity of 20/40 or better in comparison to 67 percent in all others.

Factors that probably would improve success of the surgery are three preoperative factors, three peroperative factors and three postoperative factors. Proper and complete clinical evaluation, controlling intraocular pressure and inflammation medically and preplanning surgical steps are the preoperative factors. Peroperative factors are constituted by patient anaesthesia (general anaesthesia or adequately prepared local anaesthesia), modifying and executing the preplanned steps and finally

good instrumentation and co-ordinated assistance. Postoperative regime, patient positioning and augmentation (e.g. laser), if needed, constitute the postoperative factors.

To conclude it may be said that all lenses (crystalline or artificial) can sink easily in a complicated cataract surgery and it is only with an effort that they can be removed. Falling back of the lens nucleus or IOL is analogous to sliding down a slope, while retrieving them is analogous to climbing up the slope. A team effort with good co-ordination makes the climb not only easier but also less hazardous.

INCIDENCE AND AETIOLOGY

Postoperative endophthalmitis is a catastrophic complication of intraocular surgery. Although its reported incidence has decreased significantly in the present era from 1% to about 0.05-0.1%. It still remains a source of dread for all eye specialists. Despite improvements in asepsis and sterilization, infectious endophthalmitis continues to persist as one of the most important sight threatening condition.

The incidence of post-surgical endophthalmitis is dependent on the type of surgery, the criteria used for diagnosis (clinical/ laboratory culture) and the duration of follow up. In the series reported by Kattan et al (30,002 cases), the incidence of culture positive endophthalmitis following cataract surgery, secondary IOL implantation, penetrating keratoplasty, filtering surgery for glaucoma and pars plana vitrectomy was 0.072%, 0.30%, 0.11%, 0.061% and 0.051% respectively. The risk seems higher following penetrating keratoplasty because of the donor cornea being potentially contaminated and in secondary implant surgery due to a lack of compartmentalization. Other less common situations wherein endophthalmitis may occur are, following removal of sutures and after laser capsulotomy.

Postoperative endophthalmitis can present within a few days to weeks (early endophthalmitis) or after several months to years (delayed endophthalmitis). Depending on the severity and clinical course the infection can be acute or chronic. In delayed onset endophthalmitis it is important to distinguish between cases that occur following a delayed entry of the organism (e.g. bleb related/wound dehiscence) from those due to a delayed manifestation. In the former situation the etiologic agent is usually highly virulent and manifests acute clinical symptoms and signs while in the latter situation, the infecting agent has a low virulence and tends to follow an indolent course.

Although all groups of bacteria can produce endophthalmitis, the predominant form is gram-positive organisms. Gram-positive organisms are responsible for 90 to 95 per cent of all post-surgical endophthalmitis. In the Endophthalmitis Vitrectomy Study (EVS), gramnegative isolates on culture were obtained in only 6% of endophthalmitis cases following cataract surgery. Despite this low prevalence of gram-negative infection they are important to recognize early, as these organisms are highly virulent, produce endotoxins and rapidly begin to colonize the vitreous cavity. They need a more vigorous management approach and early vitrectomy may also become necessary. Fungal endophthalmitis following intraocular surgery is seen in about 3% of patients. EVS did not include any case suspected of being fungal in origin into its study.

Gram-positive organisms that have been isolated in cases of post-surgical endophthalmitis have been

Staphylococcus epidermides, Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus viridans, Streptococcus pyogenes, Peptostreptococci and Corynebacterium. Of these, Staphylococcus epidermides is the predominant isolate in 20 to 50 per cent cases.

Propionibacterium acnes and Actinomyeces are grampositive organisms capable of producing a slow grade endophthalmitis. Staphylococcus epidermides also has this ability. Clostridium, a positive anaerobe, is an extremely rare cause unlike in post-traumatic cases.

Gram-negative organisms known to cause bacterial endophthalmitis are Pseudomonas aeruginosa (most common isolate), Proteus mirabilis, Klebsiella pneumoniae, Haemophilus influenzae, Escherichia coli and enterococci. Post-surgical fungal endophthalmitis has been reported with the following organisms, Aspergillus,

Candida, Cephalosporium, Penicillium and Paecilomyces.

Interestingly, several studies have shown that most cases of endophthalmitis are caused by organisms that

normally inhabit the conjunctival sac either as saprophytes or opportunistic pathogens. Staphylococcus epidermides has been isolated from the conjunctival sac in 69% and Staphylococcus aureus in about 33% of normal eyes. H. influenzae and rarely fungi may also be present as normal microflora. Accumulating evidence has shown that in the majority of post-surgical endophthalmitis, the causative organism is derived from the patients own periocular microbial flora. More recent studies have infact shown using plasmid typing, restriction endonuclease analysis, southern blot hybridization and pulsed field electrophoresis, that isolates obtained from the conjunctival sac and from intraocular aspirates are genetically indistinguishable. This reflects on how important it is to ensure topical asepsis and sterility during all intraocular procedures. This also shows the need to defer intraocular surgery until conditions such as dacryocystitis, lid infection and blepharitis have been adequately treated.

POST-SURGICAL BACTERIAL ENDOPHTHALMITIS Clinical Features

In the majority of cases with post-surgical bacterial endophthalmitis the clinical presentation is very classical and causes little problems in diagnosis. However, a not so infrequent occurrence is the presence of subtle signs in the early stages that keeps the surgeon wondering whether it is an infectious endophthalmitis or a sterile inflammation. This is most likely to be seen in the early follow up period after surgery. In such situations observation over the next 6-24 hours is very critical to make a definitive diagnosis. During this period of observation, the patient is started on adequate doses of topical and systemic anti-inflammatory agents (mainly corticosteroids). Endophthalmitis of an infectious origin usually progresses significantly while a sterile inflammation either remains stable or shows a minimal worsening. When uncertainty still prevails it is better to err on the side of an infectious endophthalmitis and start appropriate treatment.

Three forms of endophthalmitis are recognized based on the clinical profile. The fulminant variety occurs within about 4 days and is usually caused by gram-negative bacteria, streptococci or Staphylococcus aureus. The acute form develops between 5-7 days and is most likely to be caused by S. epidermides or coagulase negative cocci (rarely by fungi). Chronic type of endophthalmitis usually develops one to several months after the surgery and organisms involved are fungi, Propionibacterium acnes or S. epidermides.

The cardinal symptoms of post-surgical bacterial endophthalmitis revolve around the attributes of vision and pain. In the early postoperative period, pain more than anticipated is a common symptom but is not present universally in all cases. The grade of pain may vary from absent to mild to severe. In the EVS report, 26 per cent of patients had no pain at all. Hence, the absence of pain should not be taken as a factor against the likelihood of infectious endophthalmitis. When a decrease in pain is the usual course in the days following surgery, its worsening is however, an ominous symptom. A nonimprovement in vision to the anticipated degree, when accompanied by an unexpected inflammatory reaction, is a more frequently observed presentation in early postoperative endophthalmitis. Blurring was the presenting symptom in 94% of patients studied in the EVS and so may be considered as the most common symptom. There may be an associated mucopurulent discharge.

Acute bacterial endophthalmitis occurring later on has a very classical presentation. Most patients complain of a sudden onset and a rapid worsening of pain accompanied by a significant decrease in vision. Other symptoms that may be present are discharge, excessive tearing, increased sensitivity to normal light (photophobia), increase in redness of the eye and blepharospasm.

On examination the visual acuity is less than anticipated and may even be hand motions or only light perception in fulminant cases and when the presentation to an ophthalmologist is delayed. In the EVS study, hand movements were tested at a distance of 60 cm and light projection from 90 cm. A normal range of ocular motility makes the likelihood of panophthalmitis unlikely. The conjunctiva shows a variable degree of hyperemia and chaemosis and there is marked circumcorneal congestion. Corneal involvement is variable, ranging from a relatively clear cornea to one that is grossly oedematous and hazy. A limbal ring abscess, suture abscess, wound dehiscence are other signs that may be present. The anterior chamber shows a significant degree of flare and cells, the reaction sometimes being frankly fibrinous. The presence of a hypopyon is considered by most as a cardinal sign of infectious endophthalmitis. The hypopyon is dependent and in early cases may be confined to the angle alone when it may be missed. The iris pattern is lost, appears muddy and boggy and is resistant to dilation. There is a tendency to form posterior synechiae early. Pupillary response to light is absent or sluggish. In less fulminant cases one may be able to appreciate a retrolenticular flare and cells. In more severe cases, a dense discrete or confluent, yellowish vitreous exudation is evident. The

intraocular pressure is usually on the lower side of normal but may be elevated in the early stages of endophthalmitis. Most cases have some degree of digital tenderness.

Clarity of the media in endophthalmitis is graded (as adopted by EVS) depending on the visibility of the retinal details on indirect ophthalmoscopy and is as under:

Grade 1 More than 20/40 (6/12) view of the retina. Grade 2 Second order retinal vessels visible. Grade 3 Some vessels visible but not second order. Grade 4 No retinal vessels visible.

Grade 5 No red reflex.

In any patient with suspected endophthalmitis and where retinal details are not visible it is mandatory to undertake ultrasonography whenever it is available, before instituting any form of invasive, diagnostic or therapeutic interventions. This is to rule out the possibility of conditions that may mimic endophthalmitis such as dislocated nucleus and also to detect the presence of a choroidal detachment, retinal detachment and the degree of vitreous exudation and posterior vitreous detachment. Ultrasonography thus is a useful aid in establishing the diagnosis, prognostication, planning surgery and sometimes in follow up. Other investigations like visual evoked potential and electroretinography have no role in either the management or the prognostication in endophthalmitis and so are not indicated.

Confirmation of Diagnosis

Although it is prudent to follow the dictum that all unexpected inflammatory response be considered endophthalmitis unless proven otherwise, it is nevertheless important to confirm the diagnosis by culturing the organism from intraocular samples obtained in the laboratory. This raises several issues such as which ocular sample to culture, on what media to culture and when to interpret the growth as positive or otherwise.

In the recent past there was an emphasis that in patients with endophthalmitis discharge from the conjunctival sac and lid margin should be sent for culture. This is no longer recommended because of several reasons such as poor yield, culture of an unrelated organism and wasteful expenditure. If however, a suture abscess or infected suture tract is present, the removed suture must be cultured.

The most important samples to culture are aspirates from the aqueous and vitreous cavity. Although the possibility of isolating an organism is 56-70 per cent from

vitreous samples and only 36-40 per cent from aqueous samples, there have been reports when the latter was positive and the former negative. For this reason it is necessary to culture specimen obtained from both aqueous and vitreous. If an aspirate has been obtained into a syringe and the laboratory can be reached immediately, then the specimens are best sent to the laboratory with the original syringe with a cap on the needle to prevent contamination.

Aqueous tap is obtained by a paracentesis using a 25-27 gauge, half inch needle mounted on a tuberculin syringe with its plunger on. About 0.1 ml of fluid is aspirated in a controlled manner by gently withdrawing the plunger. The needle may be directly inoculated into the culture media. A part of the aspirate is ideally plated directly on to the culture media while any remaining aspirate is used to prepare slides for Gram stain and Giemsa stain.

A sample of the vitreous is the most important source to know the organism producing the endophthalmitis. It is sometimes recommended that the vitreous sample may be obtained using a 23 gauge needle introduced through the pars plana just before injecting the intravitreal antibiotics. This is said to provide an undiluted specimen and also create space for the antibiotic drugs to be subsequently injected. Although aspiration of vitreous may appear simpler it is fraught with a risk of producing vitreous traction particularly when the vitreous is formed. Aspiration may also not provide adequate sample for analysis as in endophthalmitis the vitreous is denser and usually contains inflammatory membranes. Infact it is possible that most retinal detachments following intravitreal injection are a result of vitreous aspiration rather than the injection. For aspiration of vitreous a 22 gauge needle should be used. In an aphakic patient without an intact posterior capsule and in the absence of a limbal infiltrate or abscess, one may aspirate vitreous through the anterior chamber itself. If the vitreous is fluid, 0.2-0.3 ml of fluid is gently aspirated.

The safest method to obtain vitreous sample is by vitreous biopsy. Vitreous biopsy not only enables an adequate volume of sample to be obtained but also prevents vitreous traction by cutting the strands rather than pulling on it. Vitreous biopsy can be obtained by one of two methods: with an infusion line and without an infusion line. The former has the disadvantages of diluting the specimen obtained and the need for an additional sclerotomy to be made. For obtaining an undiluted specimen by vitreous biopsy, the suction line on the vitreous cutter (which is usually connected to an