Optic
Neuritis
or
Anterior Ischemic
Optic Neuropathy?
To the Editor.\p=m-\Intheir article in the December 1991 issue of the ARCHIVES, Rizzo and Lessell1 reported considerable overlap between the clinical profiles of optic neuritis and anterior ischemic optic neuropathy (AION). The experience of the Optic Neuritis Treatment Trial (ONTT) provides further support for the existence of this overlap.2 One of the major clinical features that have been cited for many years as differentiating optic neuritis from AION is the pattern of visual field defects. Among the patients entered into the ONTT, we were surprised to find a high incidence of altitudinal and other nerve fiber bundle types of field defects that, prior to the ONTT, we felt were more typical of AION. Rizzo and Lessell's findings were similar. The ONTT experience and that of Rizzo and Lessell also clearly indicate overlap between AION and optic neuritis in the course of visual loss, the presence of pain, and the appearance of optic disc swelling including hemorrhages. Although the presence of pain may not be a differentiating fea¬ ture, it is possible that the character of the pain is, particu¬ larly if it is worsened by eye movement. Rizzo and Lessell did not have the data to address this issue. A future systematic study of the character of pain in the two entities would be worthwhile. The ONTT concluded that, for patients presumed to have optic neuritis, and who meet the study's entry criteria, an ancillary serologie and radiologie workup was unlikely to de¬ fine a cause for optic neuropathy other than optic neuritis. This conclusion includes AION since, as stressed by Rizzo and Lessell, no ancillary test exists to confirm the diagnosis of AION. Clinicians, including neuro-ophthalmologists, have learned much about the clinical profiles of both optic neuritis and AION from these two studies. The clinician should keep in mind, however, that the diagnostic dilemma of which condi¬ tion is present only exists when the optic disc is swollen. With a retrobulbar process (ie, the optic disc is not swollen), ischemie optic neuropathy is sufficiently rare that overlap with retrobulbar optic neuritis is not a common diagnostic
problem.
Roy W.
Beck, MD Fla 1. Rizzo JF, Lessell S. Optic neuritis and ischemic optic neuropathy: overlapping clinical profiles. Arch Ophthalmol. 1991;109:1668-1672. 2. Optic Neuritis Study Group. The clinical profile of optic neuritis: experience of the Optic Neuritis Treatment Trial. Arch Ophthalmol. 1991;109:1673\x=req-\
Tampa,
1678.
Peribulbar Injection and Direct Infiltration for Vitreoretinal Surgery To the Editor.\p=m-\Weread with interest the article by Friedberg et al1 in the November 1991 issue of the ARCHIVES de-
scribing an alternative technique of local anesthesia for vitreoretinal surgery using a blunt irrigating cannula passed into the posterior sub-Tenon's space. We have been performing this technique in patients since publication of the article by Mein and Woodcock.2 Our experience has been that procedures requiring considerable manipulation of the recti muscles and pressure
on
extraconal orbital tissue (when
us-
ing a tissue retractor) can cause discomfort to the patient despite an adequate intraconal block. The intraconal technique has the advantage of simplicity and relative safety, but our experience is that extraconal orbital tissues are poorly anesthetized by this method. This may not influence vitrectomy cases requiring no scleral buckling, but in cases requiring extensive scleral buckling, poor anesthetization by this method may be a significant limitation. We note that two patients described in the article by Friedberg et al had signif¬ icant discomfort during a scierai buckling procedure despite repeated local infiltration of anesthesia. Two patients also required supplemental anesthesia within the first few min¬ utes of the operation. We have recently modified the tech¬ nique by combining an initial peribulbar injection with later intraconal or extraconal direct infiltration as a supplement, if
needed. No intravenous or oral sedation was involved. An intrave¬ nous cannula was inserted into a forearm vein, and a pulse oximeter was applied to a finger for monitoring of the pulse rate and arterial oxygen saturation. The patients were posi¬ tioned on an operating table that included a molded foam headrest and support mattress for comfort. Topical benoxinate (0.4%) was instilled into the conjunctival sac. The eye¬ lids and conjunctival fornices were prepared with povidoneiodine solution. A 5/s-in, 25-gauge needle was used with a 10-mL syringe, which was filled with 4 mL of 2% lidocaine, 2 mL of 0.5% bupivicaine hydrochloride with adrenalin (1 part per 200 000 parts of bupivicaine), and 1 mL of hyaluronidase. Two thirds of the mixture was injected through eyelid skin just above the inferior orbital rim at the junction of its outer third and inner two thirds. The needle was pointed backward and slightly upward and was advanced to the hub. The remainder of the injection was given just below the orbital roof at the junction of its inner third and outer two thirds, with the needle pointing directly backward. A bag of mercury was then placed on the eye for 5 minutes. A blunt-tipped, 19-gauge, irrigating cannula was connected to a 10-mL syringe containing 10 mL of 2% bupivicaine without adren¬ alin and was placed on the scrub trolley to be used as "top up" if necessary during the procedure. We have been performing this technique for the last 2 months and report 13 cases to date. Six patients underwent vitrectomy (three vitrectomies were combined with scierai buckling); five, conventional ret¬ inal detachment repair with scierai buckling; and two, in¬ traocular gas injections into the vitreous cavity combined with transconjunctival cryotherapy. Operation duration var-
Downloaded From: http://archopht.jamanetwork.com/ by a University of Iowa User on 06/01/2015
Neuritis
or
Anterior Ischemic
Optic Neuropathy?
To the Editor.\p=m-\Intheir article in the December 1991 issue of the ARCHIVES, Rizzo and Lessell1 reported considerable overlap between the clinical profiles of optic neuritis and anterior ischemic optic neuropathy (AION). The experience of the Optic Neuritis Treatment Trial (ONTT) provides further support for the existence of this overlap.2 One of the major clinical features that have been cited for many years as differentiating optic neuritis from AION is the pattern of visual field defects. Among the patients entered into the ONTT, we were surprised to find a high incidence of altitudinal and other nerve fiber bundle types of field defects that, prior to the ONTT, we felt were more typical of AION. Rizzo and Lessell's findings were similar. The ONTT experience and that of Rizzo and Lessell also clearly indicate overlap between AION and optic neuritis in the course of visual loss, the presence of pain, and the appearance of optic disc swelling including hemorrhages. Although the presence of pain may not be a differentiating fea¬ ture, it is possible that the character of the pain is, particu¬ larly if it is worsened by eye movement. Rizzo and Lessell did not have the data to address this issue. A future systematic study of the character of pain in the two entities would be worthwhile. The ONTT concluded that, for patients presumed to have optic neuritis, and who meet the study's entry criteria, an ancillary serologie and radiologie workup was unlikely to de¬ fine a cause for optic neuropathy other than optic neuritis. This conclusion includes AION since, as stressed by Rizzo and Lessell, no ancillary test exists to confirm the diagnosis of AION. Clinicians, including neuro-ophthalmologists, have learned much about the clinical profiles of both optic neuritis and AION from these two studies. The clinician should keep in mind, however, that the diagnostic dilemma of which condi¬ tion is present only exists when the optic disc is swollen. With a retrobulbar process (ie, the optic disc is not swollen), ischemie optic neuropathy is sufficiently rare that overlap with retrobulbar optic neuritis is not a common diagnostic
problem.
Roy W.
Beck, MD Fla 1. Rizzo JF, Lessell S. Optic neuritis and ischemic optic neuropathy: overlapping clinical profiles. Arch Ophthalmol. 1991;109:1668-1672. 2. Optic Neuritis Study Group. The clinical profile of optic neuritis: experience of the Optic Neuritis Treatment Trial. Arch Ophthalmol. 1991;109:1673\x=req-\
Tampa,
1678.
Peribulbar Injection and Direct Infiltration for Vitreoretinal Surgery To the Editor.\p=m-\Weread with interest the article by Friedberg et al1 in the November 1991 issue of the ARCHIVES de-
scribing an alternative technique of local anesthesia for vitreoretinal surgery using a blunt irrigating cannula passed into the posterior sub-Tenon's space. We have been performing this technique in patients since publication of the article by Mein and Woodcock.2 Our experience has been that procedures requiring considerable manipulation of the recti muscles and pressure
on
extraconal orbital tissue (when
us-
ing a tissue retractor) can cause discomfort to the patient despite an adequate intraconal block. The intraconal technique has the advantage of simplicity and relative safety, but our experience is that extraconal orbital tissues are poorly anesthetized by this method. This may not influence vitrectomy cases requiring no scleral buckling, but in cases requiring extensive scleral buckling, poor anesthetization by this method may be a significant limitation. We note that two patients described in the article by Friedberg et al had signif¬ icant discomfort during a scierai buckling procedure despite repeated local infiltration of anesthesia. Two patients also required supplemental anesthesia within the first few min¬ utes of the operation. We have recently modified the tech¬ nique by combining an initial peribulbar injection with later intraconal or extraconal direct infiltration as a supplement, if
needed. No intravenous or oral sedation was involved. An intrave¬ nous cannula was inserted into a forearm vein, and a pulse oximeter was applied to a finger for monitoring of the pulse rate and arterial oxygen saturation. The patients were posi¬ tioned on an operating table that included a molded foam headrest and support mattress for comfort. Topical benoxinate (0.4%) was instilled into the conjunctival sac. The eye¬ lids and conjunctival fornices were prepared with povidoneiodine solution. A 5/s-in, 25-gauge needle was used with a 10-mL syringe, which was filled with 4 mL of 2% lidocaine, 2 mL of 0.5% bupivicaine hydrochloride with adrenalin (1 part per 200 000 parts of bupivicaine), and 1 mL of hyaluronidase. Two thirds of the mixture was injected through eyelid skin just above the inferior orbital rim at the junction of its outer third and inner two thirds. The needle was pointed backward and slightly upward and was advanced to the hub. The remainder of the injection was given just below the orbital roof at the junction of its inner third and outer two thirds, with the needle pointing directly backward. A bag of mercury was then placed on the eye for 5 minutes. A blunt-tipped, 19-gauge, irrigating cannula was connected to a 10-mL syringe containing 10 mL of 2% bupivicaine without adren¬ alin and was placed on the scrub trolley to be used as "top up" if necessary during the procedure. We have been performing this technique for the last 2 months and report 13 cases to date. Six patients underwent vitrectomy (three vitrectomies were combined with scierai buckling); five, conventional ret¬ inal detachment repair with scierai buckling; and two, in¬ traocular gas injections into the vitreous cavity combined with transconjunctival cryotherapy. Operation duration var-
Downloaded From: http://archopht.jamanetwork.com/ by a University of Iowa User on 06/01/2015
