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Laboratory Sciences |

Radial Optic Neurotomy Using Nasal and Temporal Approach Incisions:  Histopathologic Study in Human Cadaver Eyes FREE

Michael M. Altaweel, MD; Lars Freisberg, MD; Nikhil Pal, MD; Joel Gleiser, MD; Edwin H. Ryan, MD; Daniel Dawson, MD; Daniel Albert, MD, MS
[+] Author Affiliations

Author Affiliations: Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison (Drs Altaweel, Freisberg, Pal, Gleiser, Dawson, and Albert); Retina Vitreous Consultants, Pittsburgh, Pennsylvania (Dr Freisberg); Dr Rajenda Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi (Dr Pal); Clinica Javier Prado, Lima, Peru (Dr Gleiser); Phillips Eye Institute, Minneapolis, Minnesota (Dr Ryan); and Bascom Palmer Eye Institute, Miami, Florida (Dr Dawson).


Arch Ophthalmol. 2007;125(11):1553-1557. doi:10.1001/archopht.125.11.1553.
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Published online

Objective  To examine the structural effect of radial optic neurotomy (RON) using nasal and temporal approach incisions on the nasal side of the optic nerve (ON) using dominant and nondominant hands in human cadaver eyes.

Methods  Transvitreal RON was performed in 9 eyes with a microvitreoretinal blade by a right-handed surgeon. A nasal approach was used in 4 left eyes (using the right hand) and in 2 right eyes (using the left hand), and a temporal approach was used in 3 right eyes (using the right hand). Histologic sections were examined for depth of nerve penetration and for effect on critical structures.

Results  The scleral canal was fully incised in all cases. The mean depth of nerve penetration was 555 μm (725 μm using the nasal approach and 246.7 μm using the temporal approach) (P =.12). The globe was not ruptured in any eye. In a single right eye approached temporally using the right hand, the adventitial sheath of the central retinal artery was lacerated.

Conclusions  RON in human cadaver eyes results in lysis of the scleral canal at the ON head. Greater depth and improved safety of incision can be achieved by always approaching the incision from the nasal side of the ON using the dominant or nondominant hand.

Figures in this Article

Transvitreal radial optic neurotomy (RON) has recently been described as a surgical management for central retinal vein occlusion,17 combined cilioretinal artery and central retinal vein occlusion,8 and nonarteritic anterior ischemic optic neuropathy,9 as well as for the treatment of acute functional impairment associated with optic nerve (ON) drusen.10 The rationale of RON in central retinal vein occlusion is to alleviate the compartment syndrome that led to occlusion of the central retinal vein, which is housed within the inelastic scleral outlet.1 RON transvitreally penetrates the scleral ring and lamina cribrosa at the level of the proposed location of the thrombus.11

The mechanism of action of neurotomy is uncertain and has been questioned by some authors.12 Complications associated with this procedure are visual field defects, vitreous hemorrhage, subretinal hemorrhage, peripapillary retinal detachment, and choroidal neovascularization.1317 There are few studies2,18,19 on the histopathologic effects of RON.

It is hypothesized that incision of the full depth of the scleral canal at the ON will allow better blood flow in the central retinal vein in a compartment syndrome model. Because RON is a traumatic procedure performed on delicate and critical structures, safety should be considered before effectiveness. The objectives of the present study were to examine histologically the effects of such incisions on human cadaver eyes and to correlate the nasal and temporal approaches for performing RON on the nasal side of the optic disc using the dominant and nondominant hands in terms of depth and width of ON penetration, vessel wall damage, and globe perforation.

Nine human cadaver eyes were selected with consent from the institutional eye bank for the RON procedure by a right-handed surgeon (M.A.A.) using an unmodified 20-gauge microvitreoretinal (MVR) blade having sharp edges on both sides in a transvitreal approach. Following removal of a sclerocorneal button with limbal margins, 2 sclerotomies were created using the MVR blade for the introduction of a fiberoptic light probe and a 20-gauge MVR blade. An operating microscope was used for visualization and illumination. A radial incision into the nasal margin of the ON was performed using the MVR blade without removal of the vitreous. A nasal approach was used in 4 left eyes (using the right hand) and in 2 right eyes (using the left hand) (Figure 1A and B), and a temporal approach (Figure 2) was used in 3 right eyes (using the right hand).

Place holder to copy figure label and caption
Figure 1.

Intraoperative photographs (surgeon's view) of radial optic neurotomy (RON) on the nasal side of the optic nerve in a human cadaveric right eye using a 20-gauge microvitreoretinal blade. A, Nasal approach using the nondominant left hand at the time of entry. B, Clinical appearance of a RON incision.

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Place holder to copy figure label and caption
Figure 2.

Intraoperative photograph (surgeon's view) of radial optic neurotomy on the nasal side of the optic nerve in a human cadaveric eye using a 20-gauge microvitreoretinal blade. The right eye demonstrates the temporal approach using the right hand at the time of entry.

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All tissue samples were embedded in paraffin, and 5-μm sections were obtained in various orientations (1 axial, 1 sagittal, and 7 coronal). Microscopic examination of permanent hematoxylin-eosin slides was used to assess for scleral canal incision and to determine whether damage to ON vasculature occurred. The mean ON area of decompression was measured using commercially available software (Optimus version 6.5; Media Cybernetics, LP, Silver Spring, Maryland). The depth of ON penetration was measured by counting the number of serial sections comprising the incision and then multiplying by 5 μm per section to determine the total depth of ON penetration (Figure 3). Using the Optimus viewer, the mean ON area of the proximal-most slide containing the incision and the distal-most slide containing the incision was taken to calculate the mean ON area (Figure 4A, B, and C). Every fourth section within the incision was viewed using the Optimus viewer, the areas of intra-ON incision (decompression area) were measured, and the areas were averaged to calculate the mean decompression area. The percentage decompression area was calculated as the ratio of the mean decompression area divided by the mean ON area. All incision slides were reviewed; the slide with the greatest radial ON incision length was determined and was measured linearly to obtain the maximum length of ON penetration. This incision was then measured circumferentially, and this was recorded as the maximum width of ON penetration. Finally, the incision slides were reviewed, and the greatest length of aggregate ON and retinal and scleral incision was determined and was measured linearly to calculate the maximum cut length.

Place holder to copy figure label and caption
Figure 3.

Diagram of a coronal section of the optic nerve showing the radial optic neurotomy incision and the measurements analyzed. The white arrow indicates the maximum length of optic nerve penetration.

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Place holder to copy figure label and caption
Figure 4.

Photomicrograph of a human cadaveric eye after radial optic neurotomy (hematoxylin-eosin, original magnification ×4). A, The proximal-most slide containing the incision. B, The midsection slide containing the incision. C, The distal-most slide containing the incision.

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In 7 eyes, coronal sections were of adequate quality for complete analysis. In 2 eyes, the axial and sagittal sections provided information on depth of penetration and potential damage to critical structures (Table). In 8 of 9 eyes, the central retinal vein and artery remained undisturbed. In a single right eye approached from the temporal side using the right hand, the adventitial sheath of the central retinal artery was lacerated, while the lumen, tunica media, and tunica intima were unaffected (Figure 5). The scleral canal was fully incised in all cases, with a mean depth of 555 μm. The mean depth of ON penetration was 725 μm in eyes in which the nasal approach was used and 246.7 μm in eyes in which the temporal approach was used (P =.12). The mean area of ON decompression was 1.12% of the ON area. The nerve fiber layer was minimally disrupted in all eyes. The globe was not ruptured in any eye.

Place holder to copy figure label and caption
Figure 5.

Photomicrograph of a human cadaveric right eye after radial optic neurotomy approached from the temporal side using the right hand showing that the adventitial sheath of the central retinal artery was lacerated, while the lumen, tunica media, and tunica intima were unaffected (arrow) (hematoxylin-eosin, original magnification ×10).

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Table Graphic Jump LocationTable. Characteristics of Radial Optic Neurotomy of Human Cadaveric Eyes in Terms of Incision Approach and Histopathologic Analysis

In addition to containing the ON, the scleral outlet is the space through which the central retinal artery and central retinal vein pass into and out of the eye. The scleral outlet contains the lamina cribrosa and is encompassed by the scleral ring. As the ON approaches the eye, it consists of myelinated nerve fibers, central retinal artery, and central retinal vein and has a diameter of 3.0 mm. However, the internal diameter of the optic disc and scleral outlet is 1.5 mm. Therefore, it has been suggested that relaxation of the scleral outlet by RON might be an effective surgical treatment option for scleral outlet compartment syndromes,1 including central retinal vein occlusion. In view of the potential serious complications of RON, Opremcak et al1 stressed the importance of a consistent incision; the incision is created in a radial fashion using an MVR blade on the nasal side of the optic disc, approaching the center of the cribriform plate with an insertion depth of just beyond the widest portion of the diamond-shaped tip. Modifications of the MVR blade using a blunt lancet2 and a guarded RON knife20 have also been used to produce a safe incision. Although care should be taken to avoid major retinal vessels, it can be difficult to do so, and a case of central retinal artery occlusion has been reported after RON.21

Opremcak et al1 used human cadaveric eyes to investigate the anatomy of the scleral outlet and the best approach to relax the cribriform plate and scleral ring, as well as to determine the location, angle, and depth of penetration using the MVR blade without globe perforation. Measurements for these incisions were not reported. Czajka et al18 performed histologic examination of the ON after RON in 14 porcine eyes and demonstrated foci of hemorrhage, interstitial edema, reactive gliosis, and rare inflammatory cells with complete axonal nerve fiber loss distal to the neurotomy site at 3 weeks. In a surgical technique study of cadaver human, porcine, and rabbit eyes, Lit et al2 demonstrated that puncture of the lamina cribrosa using a specially designed lancet tip having a sharp cutting edge on 1 side and an opposing blunt edge was possible without serious injury to the ON. This procedure differs from the technique and instrumentation used during RON. Tao et al19 studied the histopathologic findings of normal miniature pig eyes after RON and found localized ON atrophy at the incision site.

The histopathologic examination in our study shows that RON in the human cadaver eye reproducibly results in lysis of the scleral canal at the ON head. Damage to the peripheral wall of a major retinal vessel occurred in 1 eye in which the incision was approached temporally. This approach impairs the surgeon's view of the central retinal vessels (Figure 2). Adverse events such as this can be avoided by always approaching the incision from the nasal aspect of the nerve even if this requires the surgeon to use the nondominant hand (Figure 1). Clear corneal phacoemulsification using the nondominant left hand has been previously shown to be safe and efficacious.22 The procedure of incising the optic disc once at the nasal aspect using the nondominant hand is comparatively brief and should be safe for many retina surgeons. Comfort with the procedure can be enhanced through wet laboratory practice.

A recent histologic study23 of 111 human globes found a mean ± SD central lamina cribrosa thickness of 378.1 ± 117.8 μm and a mean ± SD scleral thickness at the optic disc border of 276.7 ± 76.1 μm (range, 120-540 μm). Our study demonstrated a greater mean depth of penetration with incisions created from a nasal approach (725 μm) vs a temporal approach (246.7 μm).Therefore, incisions from a nasal approach are more likely to completely incise the scleral ring and peripheral lamina cribrosa than incisions from a temporal approach. This is due to the more oblique angle of penetration with the temporal approach. It is unknown if a complete incision of the scleral ring is required to potentially relax the compartment, but it seems more likely to result in such relaxation than a partial incision. In addition, the obvious practical improvement in visualization would argue for incisions made using a nasal approach.

The histologic findings of RON in human cadaver eyes support the anatomical claims made by originators of the procedure. RON in the human cadaver eye reproducibly results in incision of the scleral canal at the ON head without globe rupture occurring. We cannot conclude from this study if there are secondary changes in the central retinal vein. Damage to major retinal vessels can more reliably be avoided by approaching the RON incision from the nasal aspect of the ON using the dominant or nondominant hand rather than always using the dominant hand.

Correspondence: Michael M. Altaweel, MD, Department of Ophthalmology and Visual Sciences, University of Wisconsin, 2870 University Ave, Ste 206, Madison, WI 53705 (mmaltaweel@wisc.edu).

Submitted for Publication: October 12, 2005; final revision received March 14, 2007; accepted March 21, 2007.

Author Contributions: Dr Altaweel had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Financial Disclosure: None reported.

Disclaimer: Dr Albert, the journal's editor, was not involved in the editorial review or decision to publish this article.

Opremcak  EMBruce  RALomeo  MDRidenour  CDLetson  ADRehmar  AJ Radial optic neurotomy for central retinal vein occlusion: a retrospective pilot study of 11 consecutive cases. Retina 2001;21 (5) 408- 415
PubMed
Lit  ESTsilimbaris  MGotzaridis  EDD’Amico  DJ Lamina puncture: pars plana optic disc surgery for central retinal vein occlusion. Arch Ophthalmol 2002;120 (4) 495- 499
PubMed
Nagpal  MNagpal  KBhatt  CNagpal  PN Role of early radial optic neurotomy in central retinal vein occlusion. Indian J Ophthalmol 2005;53 (2) 115- 120
PubMed
Martínez-Jardón  CSMeza-de Regil  ADalma-Weiszhausz  J  et al.  Radial optic neurotomy for ischaemic central vein occlusion. Br J Ophthalmol 2005;89 (5) 558- 561
PubMed
Garcíia-Arumíi  JBoixadera  AMartinez-Castillo  VCastillo  RDou  ACorcostegui  B Chorioretinal anastomosis after radial optic neurotomy for central retinal vein occlusion. Arch Ophthalmol 2003;121 (10) 1385- 1391
PubMed
Weizer  JSStinnett  SSFekrat  S Radial optic neurotomy as treatment for central retinal vein occlusion. Am J Ophthalmol 2003;136 (5) 814- 819
PubMed
Patelli  FRadice  PZumbo  GFasolino  GMarchi  S Optical coherence tomography evaluation of macular edema after radial optic neurotomy in patients affected by central retinal vein occlusion. Semin Ophthalmol 2004;19 (1-2) 21- 24
PubMed
Mennel  SDroutsas  KMeyer  CHSchmidt  JCKroll  P Radial optic neurotomy in combined cilioretinal artery and central retinal vein occlusion. Br J Ophthalmol 2005;89 (5) 642- 643
PubMed
Soheilian  MKoochek  AYazdani  SPeyman  GA Transvitreal optic neurotomy for nonarteritic anterior ischemic optic neuropathy. Retina 2003;23 (5) 692- 697
PubMed
Haritoglou  CPrieglinger  SGGrueterich  MKampik  AKriegelstein  GK Radial optic neurotomy for the treatment of acute functional impairment associated with optic nerve drusen. Br J Ophthalmol 2005;89 (6) 779- 780
PubMed
Green  WRChan  CCHutchins  GMTerry  JM Central retinal vein occlusion: a prospective histopathologic study of 29 eyes in 28 cases. Retina 2005;25 (5) ((suppl)) 27- 55
PubMed
Singh Hayreh  SOpremcak  EMBruce  RA  et al.  Radial optic neurotomy for central retinal vein occlusion. Retina 2002;22 (3) 374- 377
PubMed
Williamson  THPoon  WWhitefield  LStrothodis  NJaycock  P A pilot study of pars plana vitrectomy, intraocular gas, and radial neurotomy in ischaemic central retinal vein occlusion. Br J Ophthalmol 2003;87 (9) 1126- 1129[published correction appears in Br J Ophthalmol. 2003;87(11):1432].
PubMed
Schneider  UInhoffen  WGrisanti  SBartz-Schmidt  KU Characteristics of visual field defects by scanning laser ophthalmoscope microperimetry after radial optic neurotomy for central retinal vein occlusion. Retina 2005;25 (6) 704- 712
PubMed
Takaya  KSuzuki  YNakazawa  M Massive hemorrhagic retinal detachment during radial optic neurotomy [published online ahead of print July 23, 2005]. Graefes Arch Clin Exp Ophthalmol 2006;244 (2) 265- 26710.1007/s00417-005-0067-7
PubMed
Samuel  MADesai  URGandolfo  CB Peripapillary retinal detachment after radial optic neurotomy for central retinal vein occlusion. Retina 2003;23 (4) 580- 583
PubMed
Bakri  SJBeer  PM Choroidal neovascularization after radial optic neurotomy for central retinal vein occlusion. Retina 2004;24 (4) 610- 611
PubMed
Czajka  MPCummings  TJMcCuen  BW  IIToth  CANguyen  HFekrat  S Radial optic neurotomy in the porcine eye without retinal vein occlusion. Arch Ophthalmol 2004;122 (8) 1185- 1189
PubMed
Tao  YJiang  YRLi  XXYin  CYYao  J Fundus and histopathological study of radial optic neurotomy in the normal miniature pig eye. Arch Ophthalmol 2005;123 (8) 1097- 1101
PubMed
Chalam  KVShah  VA A newly designed guarded radial optic neurotomy knife. Retina 2004;24 (5) 817- 818
PubMed
Yamamoto  STakatsuna  YSato  EMizunoya  S Central retinal artery occlusion after radial optic neurotomy in a patient with central retinal vein occlusion. Am J Ophthalmol 2005;139 (1) 206- 207
PubMed
Kageyama  TYaguchi  SMetori  Y  et al.  Visual results and complications of temporal incision phacoemulsification performed with the non-dominant left hand by junior ophthalmologists. Br J Ophthalmol 2002;86 (11) 1222- 1224
PubMed
Jonas  JBHolbach  L Central corneal thickness and thickness of the lamina cribrosa in human eyes. Invest Ophthalmol Vis Sci 2005;46 (4) 1275- 1279
PubMed

Figures

Place holder to copy figure label and caption
Figure 1.

Intraoperative photographs (surgeon's view) of radial optic neurotomy (RON) on the nasal side of the optic nerve in a human cadaveric right eye using a 20-gauge microvitreoretinal blade. A, Nasal approach using the nondominant left hand at the time of entry. B, Clinical appearance of a RON incision.

Graphic Jump Location
Place holder to copy figure label and caption
Figure 2.

Intraoperative photograph (surgeon's view) of radial optic neurotomy on the nasal side of the optic nerve in a human cadaveric eye using a 20-gauge microvitreoretinal blade. The right eye demonstrates the temporal approach using the right hand at the time of entry.

Graphic Jump Location
Place holder to copy figure label and caption
Figure 3.

Diagram of a coronal section of the optic nerve showing the radial optic neurotomy incision and the measurements analyzed. The white arrow indicates the maximum length of optic nerve penetration.

Graphic Jump Location
Place holder to copy figure label and caption
Figure 4.

Photomicrograph of a human cadaveric eye after radial optic neurotomy (hematoxylin-eosin, original magnification ×4). A, The proximal-most slide containing the incision. B, The midsection slide containing the incision. C, The distal-most slide containing the incision.

Graphic Jump Location
Place holder to copy figure label and caption
Figure 5.

Photomicrograph of a human cadaveric right eye after radial optic neurotomy approached from the temporal side using the right hand showing that the adventitial sheath of the central retinal artery was lacerated, while the lumen, tunica media, and tunica intima were unaffected (arrow) (hematoxylin-eosin, original magnification ×10).

Graphic Jump Location

Tables

Table Graphic Jump LocationTable. Characteristics of Radial Optic Neurotomy of Human Cadaveric Eyes in Terms of Incision Approach and Histopathologic Analysis

References

Opremcak  EMBruce  RALomeo  MDRidenour  CDLetson  ADRehmar  AJ Radial optic neurotomy for central retinal vein occlusion: a retrospective pilot study of 11 consecutive cases. Retina 2001;21 (5) 408- 415
PubMed
Lit  ESTsilimbaris  MGotzaridis  EDD’Amico  DJ Lamina puncture: pars plana optic disc surgery for central retinal vein occlusion. Arch Ophthalmol 2002;120 (4) 495- 499
PubMed
Nagpal  MNagpal  KBhatt  CNagpal  PN Role of early radial optic neurotomy in central retinal vein occlusion. Indian J Ophthalmol 2005;53 (2) 115- 120
PubMed
Martínez-Jardón  CSMeza-de Regil  ADalma-Weiszhausz  J  et al.  Radial optic neurotomy for ischaemic central vein occlusion. Br J Ophthalmol 2005;89 (5) 558- 561
PubMed
Garcíia-Arumíi  JBoixadera  AMartinez-Castillo  VCastillo  RDou  ACorcostegui  B Chorioretinal anastomosis after radial optic neurotomy for central retinal vein occlusion. Arch Ophthalmol 2003;121 (10) 1385- 1391
PubMed
Weizer  JSStinnett  SSFekrat  S Radial optic neurotomy as treatment for central retinal vein occlusion. Am J Ophthalmol 2003;136 (5) 814- 819
PubMed
Patelli  FRadice  PZumbo  GFasolino  GMarchi  S Optical coherence tomography evaluation of macular edema after radial optic neurotomy in patients affected by central retinal vein occlusion. Semin Ophthalmol 2004;19 (1-2) 21- 24
PubMed
Mennel  SDroutsas  KMeyer  CHSchmidt  JCKroll  P Radial optic neurotomy in combined cilioretinal artery and central retinal vein occlusion. Br J Ophthalmol 2005;89 (5) 642- 643
PubMed
Soheilian  MKoochek  AYazdani  SPeyman  GA Transvitreal optic neurotomy for nonarteritic anterior ischemic optic neuropathy. Retina 2003;23 (5) 692- 697
PubMed
Haritoglou  CPrieglinger  SGGrueterich  MKampik  AKriegelstein  GK Radial optic neurotomy for the treatment of acute functional impairment associated with optic nerve drusen. Br J Ophthalmol 2005;89 (6) 779- 780
PubMed
Green  WRChan  CCHutchins  GMTerry  JM Central retinal vein occlusion: a prospective histopathologic study of 29 eyes in 28 cases. Retina 2005;25 (5) ((suppl)) 27- 55
PubMed
Singh Hayreh  SOpremcak  EMBruce  RA  et al.  Radial optic neurotomy for central retinal vein occlusion. Retina 2002;22 (3) 374- 377
PubMed
Williamson  THPoon  WWhitefield  LStrothodis  NJaycock  P A pilot study of pars plana vitrectomy, intraocular gas, and radial neurotomy in ischaemic central retinal vein occlusion. Br J Ophthalmol 2003;87 (9) 1126- 1129[published correction appears in Br J Ophthalmol. 2003;87(11):1432].
PubMed
Schneider  UInhoffen  WGrisanti  SBartz-Schmidt  KU Characteristics of visual field defects by scanning laser ophthalmoscope microperimetry after radial optic neurotomy for central retinal vein occlusion. Retina 2005;25 (6) 704- 712
PubMed
Takaya  KSuzuki  YNakazawa  M Massive hemorrhagic retinal detachment during radial optic neurotomy [published online ahead of print July 23, 2005]. Graefes Arch Clin Exp Ophthalmol 2006;244 (2) 265- 26710.1007/s00417-005-0067-7
PubMed
Samuel  MADesai  URGandolfo  CB Peripapillary retinal detachment after radial optic neurotomy for central retinal vein occlusion. Retina 2003;23 (4) 580- 583
PubMed
Bakri  SJBeer  PM Choroidal neovascularization after radial optic neurotomy for central retinal vein occlusion. Retina 2004;24 (4) 610- 611
PubMed
Czajka  MPCummings  TJMcCuen  BW  IIToth  CANguyen  HFekrat  S Radial optic neurotomy in the porcine eye without retinal vein occlusion. Arch Ophthalmol 2004;122 (8) 1185- 1189
PubMed
Tao  YJiang  YRLi  XXYin  CYYao  J Fundus and histopathological study of radial optic neurotomy in the normal miniature pig eye. Arch Ophthalmol 2005;123 (8) 1097- 1101
PubMed
Chalam  KVShah  VA A newly designed guarded radial optic neurotomy knife. Retina 2004;24 (5) 817- 818
PubMed
Yamamoto  STakatsuna  YSato  EMizunoya  S Central retinal artery occlusion after radial optic neurotomy in a patient with central retinal vein occlusion. Am J Ophthalmol 2005;139 (1) 206- 207
PubMed
Kageyama  TYaguchi  SMetori  Y  et al.  Visual results and complications of temporal incision phacoemulsification performed with the non-dominant left hand by junior ophthalmologists. Br J Ophthalmol 2002;86 (11) 1222- 1224
PubMed
Jonas  JBHolbach  L Central corneal thickness and thickness of the lamina cribrosa in human eyes. Invest Ophthalmol Vis Sci 2005;46 (4) 1275- 1279
PubMed

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