Prospective study on retinal nerve fibre layer cha

Authors: Jacky W Y Lee Jimmy S M Lai Doris W F Yick Can Y F Yuen

Publish Date: 2012/07/31

Volume: 32, Issue: 6, Pages: 577-582

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Abstract

To investigate the retinal nerve fibre layer RNFL changes after an acute attack of phacomorphic angle closure This prospective study involved ten cases of phacomorphic angle closure that underwent cataract extraction and intraocular lens insertion after intraocular pressure lowering Apart from visual acuity and intraocular pressure IOP RNFL thickness and vertical cup disc ratio VCDR were measured by optical coherence tomography OCT at 3–9 months post attack Humphrey visual field assessment was performed at 9 months post attack All cases had mean phacomorphic duration of 5 days Postoperatively best correct Snellen visual acuity was 04 ± 02 and IOP at 9 months was 110 ± 31 mmHg There was no difference in VCDR and RNFL between the attack and contralateral eye at 3 months post attack both p = 04 At 9 months post attack there was significant thinning in the average p = 001 superior p = 001 and inferior p = 0006 RNFL There was no significant difference in the pattern standard deviation PSD between the two eyes on the Humphrey visual field nor was there any correlation between PSD severity and RNFL thinning all p  02 Patients with 5 days duration of phacomorphic angle closure are likely to have reasonable postoperative vision An acute episode of phacomorphic angle closure can trigger an accelerated RNFL thinning despite normal IOP and open angles most noticeable in the superior and inferior quadrants occurring between 3 and 9 months post attack Glaucomatous optic neuropathy in the attack eye was evident by OCT but not by visual field assessment at the same time intervalPhacomorphic angle closure is a secondary angle closure caused by a swollen and mature cataract obstructing the drainage angle leading to an acute elevation of intraocular pressure IOP and potential glaucomatous optic neuropathy GON if not treated timely The initial aim of treatment of phacomorphic angle closure is to lower the IOP with combinations of topical antiglaucoma medications systemic acetazolamide intravenous mannitol and or argon laser iridoplasty ALPI 1 All of these treatments have been established to be effective initial treatments with no evidence showing superiority of one over the other at the moment The definitive treatment after IOP control is cataract extractionThe term phacomorphic glaucoma is used if there resultant GON 1 which has been previously quantified and reported using visual field VF assessments or clinical cupdisc ratio monitoring However both of these parameters are variable and not entirely objective especially when phacomorphic angle closure often affects an elderly population where dementia and neglect are common 2 In addition studies in acute primary angle closure APAC have shown that more than half of the patients with a single attack can have no visual field defects 3 On the other hand retinal nerve fiber layer measurements can detect early GON as its damage often precedes visual field loss 4 The use of optical coherence tomography OCT for retinal nerve fibre layer RNFL and optic nerve head analyses is noninvasive requires minimal patient cooperation and provides objective and early assessment of GON in patients with phacomorphic angle closureConsecutive cases of acute phacomorphic angle closure from December 2009 to December 2010 were recruited from Caritas Medical Center Hong Kong Special Administrative Region People’s Republic of China Patient’s intraocular pressure was lowered initially either by ALPI or systemic acetazolamide The selection between the two initial treatments was randomized The randomization was part of a treatment protocol of another study comparing the effects of initial treatments in phacomorphic angle closure Those receiving ALPI received laser applications 360° to the peripheral iris with power titrated to achieve visualized contractions of the iris All ALPI was performed by a single surgeon JL Those receiving systemic acetazolamide received intravenous acetazolamide 500 mg stat followed by oral acetazolamide 250 mg four times daily and slowrelease potassium chloride tablets 600 mg twice daily if there were no systemic contraindications All patients were put on the following eye drops Atropine 1  daily Alcon Inc Hünenberg CH6331 Switzerland Pred forte1 four times daily Allergan Inc Irvine CA 926239534 USA and Timolol 05  twice daily Santen Pharmaceutical Co Ltd Osaka 5338651 Japan in the attack eye Patients with presenting IOP higher than 60 mmHg or IOP higher than 40 mmHg after 2 h of treatment were given 200 ml of 20  mannitol intravenously over 1 h Hourly IOP was documented until it was below 25 mmHgCases were included for consenting individuals with a first episode of acute 14 days phacomorphic angle closure with an IOP more than 40 mmHg The diagnosis of phacomorphic angle closure was based on the presence of an intumescent cataract and signs of acute angle closure conjunctival injection shallow anterior chamber corneal edema in the index eye or an open angle in the contralateral eye as determined by gonioscopy 2 Cases were excluded if IOP lowering treatment was given for this acute episode prior to the study or where ALPI was not possible either due to a severely edematous cornea or uncooperative patientAll cases received extracapsular cataract extraction ECCE and intraocular lens IOL insertion under regional anesthesia by one of the three glaucoma surgeons at our center within 3 days of presentation to our clinic All glaucoma medications were discontinued immediately after the cataract extraction ECCE was chosen over phacoemulsification due to less endothelial damage from ultrasound energy and phacoemulsification would impose greater surgical risk in the setting of phacomorphic angle closure especially in the presence of any residual corneal edema and zonule loosening 2Patients were followed up on day one 1 week 1 month 3 months and as needed postoperatively and IOP was measured by Goldman applanation tonometry in each visit Best corrected visual acuity BCVA was measured by Snellen chart at 1 month postoperatively The trabeculariris angle was measured by gonioscopy and ultrasound biomicroscopy UBM at 3 months post attack

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