Ocular Toxicology Preston H. Blomquist, MD Department of - PowerPoint PPT Presentation

1 / 49
About This Presentation
Title:

Ocular Toxicology Preston H. Blomquist, MD Department of

Description:

Ocular Toxicology Preston H. Blomquist, MD Department of Ophthalmology University of Texas Southwestern Medical Center at Dallas Toxic Optic Neuropathy Symptoms ... – PowerPoint PPT presentation

Number of Views:722
Avg rating:3.0/5.0
Slides: 50
Provided by: toxicolog4
Category:

less

Transcript and Presenter's Notes

Title: Ocular Toxicology Preston H. Blomquist, MD Department of


1
Ocular Toxicology
  • Preston H. Blomquist, MD
  • Department of Ophthalmology
  • University of Texas Southwestern Medical Center
    at Dallas

2
Tamsulosin (Flomax)
  • Systemic alpha-1 antagonist
  • Relaxes the smooth muscle in the bladder neck and
    prostate, improves urinary flow in benign
    prostatic hypertrophy (BPH)
  • Tamsulosin is highly selective for the alpha-1A
    receptor subtype that predominates in the
    prostate, more uroselective compared to other
    alpha-1 blockers for BPH, such as Hytrin and
    Cardura

3
Tamsulosin (Flomax)
  • Intraoperative Floppy Iris Syndrome (IFIS)
  • Subnormal preoperative pupil dilation
  • Repeated incisional prolapse of a billowing,
    floppy iris, causing progressive intraoperative
    miosis that is not prevented by sphincterotomies
    and mechanical pupil stretching.

4
Tamsulosin (Flomax)
  • Intraoperative Floppy Iris Syndrome (IFIS)
  • Stop Flomax 2 weeks preop
  • Improves, but does not eliminate floppy iris
    behavior
  • IFIS occurs as late as 1 year after stopping
    Flomax
  • Iris hooks, pupil expansion rings
  • Sphincterotomies, pupil stretching ineffective
  • Pharmacologic aids
  • Atropine (no!), phenylephrine/epinephrine

5
Erectile DysfunctionAgents
  • Sildenafil (Viagra), tadalafil (Cialis),
    vardenafil (Levitra)
  • Inhibits phosphodiesterase-5 (PDE5) most
    dramatically
  • Also has 10 effectiveness in inhibiting PDE6
    (found in photoreceptors, mediates transduction)
  • Visual symptoms include bluish tinge or haze to
    vision, increased light sensitivity (3 incidence
    at low dosages, 11 after 100 mg dose, near 50
    after 200 mg)

6
Erectile DysfunctionAgents
  • By summer 2005, FDA had received 43 reports of
    NAION in men using these drugs
  • Due to decreased perfusion pressure from
    drug-induced hypotension?
  • Viagra alone estimated to have 23 million
    habitual users

7
Erectile DysfunctionAgents
  • FAA recommends that pilots not fly within 6 hours
    of taking the drug
  • Unknown what long-term effects on eye are
  • Caution advised in patients with retinal problems
    (do not exceed 50 mg)
  • Macular degeneration
  • Retinitis pigmentosa (dont take in autosomal
    recessive RP due to genetic defect in PDE-6?)
  • Diabetic retinopathy
  • Definitely avoid if previously had NAION in one
    eye

8
Vigabatrin (Sabril)
  • Recently approved by FDA
  • Drug may control refractory seizures (inhibits
    GABA transaminase)
  • GABA plays a role in horizontal cell coupling,
    amacrine and bipolar cells in retina
  • High incidence of side effects (20-36)
  • Bilateral peripheral constriction of visual
    field
  • Tunnel vision
  • In children, can have peripheral retinal atrophy
    and secondary inverse (nasal) optic atrophy
  • Visual field loss does not progress on withdrawal
    of drug, but may persist and be irreversible
  • Baseline (within 4 wks of starting drug) exam,
    every 3 months while on drug, and exam 3 6
    months after discontinuing
  • Visual fields
  • Indirect ophthalmoscopy

9
Phenytoin
  • Nystagmus
  • Fine nystagmus at therapeutic doses
  • Coarse nystagmus in toxic states
  • May persist for months after stopping drug

10
Topiramate
  • Used to treat refractory epilepsy and, off label,
    to treat migraine headache or as a weight loss
    medication
  • Can cause transient myopia or, more importantly,
    angle closure glaucoma
  • Treat by stopping drug, use topical cycloplegic
    agents, consider topical beta-blocker and topical
    or oral CAI

11
Cancer Chemotherapy
  • Imperia PS, et al. Surv Ophthalmol 34209-230,
    1989
  • Burns LJ. Seminars in Oncology 19492-500, 1992
  • Al-Tweigeri T, et al. Cancer 781359-1373, 1996
  • Schmid KE, et al. Surv Ophthalmol 5119-46, 2006

12
Alkylating Agents
  • Busulfan Polychromatic posterior subcapsular
    cataract (10 30)
  • Cisplatin Neuroretinal (blurred vision and
    color blindness from retinal toxicity, optic
    neuritis, papilledema)
  • Intracarotid injection may cause ipsilateral
    vision loss from retinal and optic nerve ischemia
  • Cyclophosphamide Blurred vision
  • Nitrosoureas Orbital and neuroretinal toxicity
    with intracarotid administration

13
Antimetabolites
  • 5-Fluorouracil Ocular surface toxicity, punctal
    stenosis
  • Cytosine arabinoside Photophobia and pain from
    keratoconjunctivitis (relieved with topical
    corticosteroids, resolves several weeks after
    completion of therapy)
  • Vincristine Cranial nerve palsies (50), optic
    neuropathy, night blindness, cortical blindness
  • Methotrexate Ocular toxicity in 25
    (periorbital edema, blepharitis, conjunctivitis
    treat with artificial tears)

14
Taxanes
  • Promote the assembly of tubulin micropolymers
    (abnormal microtubules)
  • Paclitaxel
  • Photopsia (flashing lights across the visual
    field), often described as flies, shooting
    lights, or fireworks (usually lasts 15 min to
    3 hr after infusion)
  • Decreased visual acuity
  • Docetaxel
  • Epiphora due to canalicular and nasolacrimal duct
    obstruction (early temporary silicone intubation
    in symptomatic patients recommended)

15
Antibiotics
  • Doxorubicin (adriamycin) conjunctivitis,
    increased tearing (25)
  • Mitomycin C Blurred vision

16
Interferon
  • Interferon-a used for hairy cell leukemia,
    Kaposis sarcoma, CML, non-Hodgkins lymphoma,
    malignant melanoma, renal cell carcinoma
  • Retinopathy common
  • Cotton wool spots, retinal capillary
    non-perfusion, vascular occlusions, leakage,
    hemorrhages, retina edema
  • Likely due to autoimmune mechanism (complement
    dependent)

17
Tamoxifen (Nolvadex)
  • Estrogen antagonist
  • Ocular toxicity at high doses ( 180 mg/d)
  • Keratopathy bilateral white whorl-like
    subepithelial opacities
  • Retinopathy white refractile opacities
    associated with cystoid macular edema
  • Optic neuritis (reported at total dosage of only
    2 to 3 grams)

18
Tamoxifen
  • Probably little ocular risk at low dose (10-20 mg
    bid-tid)
  • Baseline eye exam and repeated eye exams every
    two years recommended
  • Tamoxifen may also increase the risk of posterior
    subcapsular cataracts

19
Corticosteroids
  • Ocular side effects include
  • Cataract (posterior subcapsular)
  • Increased intraocular pressure (secondary open
    angle glaucoma)
  • Immunosuppression leading to infectious
    complications

20
Steroid-Induced Glaucoma
  • More common with topical administration
  • Steroid-induced intraocular pressure (IOP)
    increases occur more frequently, more severely,
    and more rapidly with topical dexamethasone in
    children than adults
  • Even inhaled and intranasal steroids can cause
    IOP rise, especially if positive family history

21
Steroids and Infection
  • Cancer patients
  • Candida endophthalmitis
  • Cytomegalovirus retinitis
  • Ocular toxoplasmosis
  • Topical steroids can potentiate infections
  • Herpes simplex keratitis
  • Fungal keratitis

22
Phenothiazines
  • Thioridazine (Mellaril) may cause a pigmentary
    retinopathy
  • Drug binds to melanin in RPE
  • Rare if daily dose 800 mg
  • Early sxs include blurred vision and decreased
    night vision
  • ERG and EOG abnormal
  • Complicating exam is that patients on
    thioridazine often have significant psychiatric
    disease

23
Phenothiazines
  • Unlike thioridazine, chlorpromazine does not
    cause similar retinopathy
  • Chlorpromazine (Thorazine) can cause heavy
    deposits on the lens and cornea
  • Only other phenothiazine that produces
    retinopathy is experimental drug NP 207 (reported
    in 1956)

24
Lithium
  • Myriad ocular side effects
  • Photophobia
  • Extraocular muscle abnormalities
  • Exophthalmos
  • Pseudotumor cerebri

25
Amiodarone
  • One of the most effective antiarrhythmic agents
    available
  • Up to 40 of patients report seeing colored
    (blue-green) rings or haloes around lights
  • Keratopathy in almost 100 of patients
  • Golden-brown verticillate whorl-like pattern
  • Asymptomatic

26
Amiodarone and AION
  • Anterior ischemic optic neuropathy has been
    reported
  • Because patients taking amiodarone have serious
    cardiovascular disease, unknown if AION is due to
    drug or systemic blood vessel disease

27
Amiodarone and AION
  • In 1997, an Oregon county court awarded a
    20,000,000 judgment against Wyeth-Ayerst
    Laboratories. Plaintiff developed bilateral AION
    6 weeks after starting drug.
  • Even if causal relationship exists, how can one
    withhold drug when indication is for
    life-threatening recurrent ventricular
    arrhythmias not controlled by other meds
  • PDR since suit calls for regular ophthalmic
    examinations

28
Amiodarone Optic Neuropathy
  • Unlike AION, amiodarone optic neuroapthy usually
    presents bilaterally
  • Initially mildly decreased vision, visual field
    defects, optic disc swelling
  • Upon discontinuing amiodarone, optic disc
    swelling and visual function may slowly improve

Nagra PK, Foroozan R, Savino PJ, Castillo I,
Sergott RC. Amiodarone induced optic neuropathy.
Br J Ophthalmol 2003 87420-422
29
Digitalis
  • 11 25 ocular side effects at toxic dosages
  • Color vision abnormality (yellow-blue)
  • Reversible
  • Toxicity may be made worse with concomitant
    quinidine therapy

30
Antimalarials
  • Chloroquine (CQ) and hydroxychloroquine (HCQ) are
    both aminoquinolones
  • CQ first used in the treatment of rheumatologic
    disease in 1950s
  • Hobbs, 1959 association of CQ and retinopathy
    (paracentral scotomas with macular pigmentary
    disturbance, progresses to permanent central
    retina damage (bulls eye maculopathy)
  • Less likely at 3.5 mg/kg/day (250 mg/day for
    small patients)

31
Hydroxychloroquine
  • Unlike CQ, HCQ does not cause a breakdown of
    blood-retinal barrier
  • Less toxicity with HCQ
  • Retinopathy unlikely if daily dose lt 6.5
    mg/kg/day for lt 6 years in patients with normal
    renal function
  • Incidence of corneal deposits lt 10 (as compared
    to 95 of patients on CQ)

32
Hydroxychloroquine
  • PDR recommends quarterly ophthalmologic exams
  • Royal College of Ophthalmologists recommends
    annual check by prescribing physician with
    referral to ophthalmologist only if abnormality
    noted
  • What to do?

33
Screening for HCQ Toxicity
  • Baseline and annual ophthalmologic exams
  • Best-corrected visual acuity
  • Red Amsler grid
  • Color plates
  • Fundus exam
  • Amsler grid to take home and check monthly
  • Consider HVF 10-2 (white target) periodically
  • More frequent exams if
  • Daily dose gt 6.5 mg/kg/day (use lean body
    weight)
  • Duration of treatment gt 6 years
  • Renal disease
  • Age gt 65 years

34
Toxic Optic Neuropathy
  • Symptoms
  • Gradual onset of visual impairment (vision hand
    motion or better)
  • Painless vision loss
  • Bilateral
  • Centrocecal scotomas
  • Dyschromatopsia
  • Optic discs may look normal early on, pale
    (especially temporally) late

35
Alcohols
  • Methanol and ethylene glycol
  • Anion-gap metabolic acidosis
  • Treatment
  • Correct acidosis
  • Hemodialysis
  • Ethanol blocking of alcohol dehydrogenase
  • Sterno 71 ethyl alcohol, 3.6 methanol

36
Antitubercular Drugs
  • Ethambutol
  • Chelates metal ions involved in prokaryotic
    ribosomes (inhibits arabinosyl transferase, an
    enzyme in mycobacterial cell wall synthesis)
  • Bilateral retrobulbar optic neuropathy
  • Even at safe dosage ( 15 mg/kg/d) incidence
    of toxicity is 1 2
  • Risk increased with impaired renal function or
    diabetes
  • Usually noted at 3 6 months
  • Usually reversible if promptly discontinued
  • Isoniazid
  • Optic neuropathy rare

37
Screening for Toxic Optic Neuropathy
  • Measure papillomacular bundle function
  • Visual acuity
  • Color vision
  • Contrast senstivitity
  • Central visual fields
  • Amsler grid (red)
  • HVF 10-2 or 10-1
  • pVEP

38
Quinine
  • Alkaloid from cinchona bark
  • Used for muscle cramps, abortion, suicide
  • Quinidine is an isomer of quinine
  • Cinchonism
  • Tinnitus, vertigo
  • Headache, nausea, vomiting
  • Diarrhea
  • Hot, flushed skin, sweating
  • Delirium, ventricular tachycardia
  • Optic atrophy (ganglion cell damage), congenital
    blindness in unsuccessful abortions

39
Nutritional Optic Neuropathy
  • Tobacco-alcohol amblyopia
  • Thought to be due to dietary deficiency of
    B-complex vitamins, especially thiamine (B1)
  • Some patients may have Lebers hereditary optic
    neuropathy
  • Treatment
  • Vitamin supplementation
  • Discontinue smoking, drinking

40
Pseudotumor Cerebri
  • Idiopathic intracranial hypertension
  • Increased intracranial pressure
  • Normal or small ventricles on neuroimaging
  • Normal CSF
  • Papilledema
  • Exogenous causes
  • Heavy metals (lead, arsenic)
  • Vitamin A / retinoids
  • Tetracycline
  • Nalidixic acid
  • Prolonged corticosteroid therapy (or
    withdrawal)
  • Lithium

41
Drug-Induced Uveitis
  • Systemic drugs
  • Rifabutin semisynthetic derivative of
    rifamycin and rifampin, particularly effective
    against M. avium intracellulare
  • Biphosphonates (pamidronate, etidronate,
    clodronate, risedronate)
  • Sulfonamides (including trimethoprim-sulfamethoxa
    zole)

42
Drug-Induced Uveitis
  • Topical
  • Metipranolol (lt 0.5 incidence)
  • Intravitreal
  • Cidofovir (incidence decreased from 53 to 19
    if oral probenecid given before injection)

43
3-Hydroxy-3-Methyl-Glutaryl-CoA Reductase
Inhibitors (statins)
  • Although initial concern for increased cataracts
    in patients, no evidence that lovastatin is
    cataractogenic
  • Possible association of diplopia, blepharoptosis,
    and ophthalmoplegia with statin use
  • Fraunfelder FW, Richards AB. Ophthalmology
    20081152282-5

44
Niacin (Nicotinic acid)
  • Used to treat hyperlipidemia
  • Causes reversible toxic cystoid maculopathy in
    approximately 0.67 of patients taking high
    dosages (gt 1.5 g/day)
  • Absence of leakage on fluorescein angiography
  • Refer symptomatic patients for exam

45
Ddx of CME without leakage on FA
  • Niacin maculopathy
  • Congenital X-linked retinoschisis
  • Goldmann-Favre syndrome
  • Paclitaxel/docetaxel maculopathy

46
Herbal Supplements
  • Eyebright looks like an eye, so must be good for
    the eye, right?
  • Bilberry (for stabilizing microcirculation)
    pretty safe
  • Gingko biloba acts as a blood thinner (stop 24
    hours prior to surgery)
  • St. Johns wort (natural antidepressant) may
    contribute to cataracts, especially in
    combination with bright-light therapy
  • Canthexanthine (carotenoid) may cause
    crystalline-like retinopathy
  • Licorice can cause transient vision loss similar
    to migraine aura

47
Potpourri
  • Minocycline pseudotumor cerebri, scleral
    pigmentation
  • Ciprofloxacin optic neuropathy similar to other
    quinolones (CQ, quinine)
  • Clomiphene palinopsia (prolonged afterimages),
    shimmering of peripheral field, photophobia
  • Trazadone palinopsia
  • Didanosine retinal lesions, constriction of
    peripheral visual field
  • Cetirizine (Zyrtec) oculogyric crisis
  • Biphosphonates scleritis
  • Thiazolidinediones macular edema (in patients
    also on insulin with peripheral edema)

48
Over-The-Counter Eye Drops
  • Preserved eye drops
  • Preservatives can cause toxic or allergic
    reactions
  • Ocular decongestants
  • Rebound vasodilatation
  • Punctate epithelial keratitis
  • May precipitate acute angle closure glaucoma
    attack in susceptible individuals

49
Topical Anesthetic Abuse
  • Topical anesthetic eye drops are toxic to cornea
  • Prolonged use leads to epithelial loss, stromal
    edema, corneal opacities
  • Typical patient works in medical field with easy
    access to drops
  • May have to search purse, pockets to make the
    diagnosis
  • Never prescribe a patient a topical anesthetic
    drop!
Write a Comment
User Comments (0)
About PowerShow.com