Eye Examination and Protection

Educational Objectives

The goal of this program is to improve examination of the eyes in children protection of the eyes while in the wilder­ness. After hearing and assimilating this program, the clinician will be better able to:

1.   Apply the American Academy of Pediatrics recommendations for vision screening and referral.

2.   Employ useful techniques for examination of the eyes in children.

3.   Review the contents of a wilderness emergency kit for the eyes.

4.   Discuss the effects of environment on the eyes.

5.   Advise patients on how to evaluate sunglasses, based on various criteria.

Faculty Disclosure

In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty and members of the planning committee to disclose relevant financial relationships within the past 12 months that might create any per­sonal conflicts of interest. Any identified conflicts were resolved to ensure that this educational activity promotes quality in health care and not a proprietary business or commercial interest. For this program, the faculty and plan­ning committee reported nothing to disclose.

Acknowledgements

Dr. Donner was recorded at 22nd Annual National Conference on Wilderness Medicine, held August 6-10, 2009, in Big Sky, MT, and sponsored by the American College of Emergency Physicians (ACEP), ACEP State Chapter of Cal­ifornia, Inc, and Wilderness and Travel Medicine. Dr. O’Hara was recorded at 2nd Annual Eyes: What Not to Miss and When to Refer, held May 15, 2009, in Napa, CA, and sponsored by the University of California, Davis, Health System, Office of Continuing Medical Education, and The Eye Center. The Audio-Digest Foundation thanks the speakers and the sponsors for their cooperation in the production of this program.

The Pediatric Eye Examination

Mary O’Hara, MD, Professor of Pediatric Ophthalmology and Strabismus, Department of Ophthalmology, University of California, Davis, School of Medicine

Visual acuity: eye-popping phenomenon  —  when infant does not open eyes during examination; in first 3 mo of life, sphincter of iris immature and not as reactive, so infant uses lids to regulate amount of light; infant closes eyes when brought into bright room, and as light turned down, infant’s eyes open; to determine degree of quantitative vi­sion in toddler, hold Near chart »13 in away and have infant point to bird, while covering half of chart; another op­tion using HOTV chart (project chart and point to letter, and let toddler point to same letter); also effective in older stroke victims unable to respond verbally; 20/20 vision  —  at 20 ft, able to see what person with normal vision can see at 20 ft; if vision 20/40, at 20 ft, able to see what person with normal eyesight sees at 40 ft; while performing vi­sual acuity tests, should look at child and behavior (eg, peeking, squinting); nearsighted child squints when glasses removed and asked to look at distance; other individuals use manmade pinhole; pinhole on occluder  —helps deter­mine whether visual deficit pathologic or refractive; if child’s vision better with pinhole, deficit refractive; effective because light rays enter at different angles and focus through cornea and lens; lens focuses to ensure all rays paral­lel going to back of eye; removes rays from all directions, allowing only straight-ahead rays to enter; most people normal; »15% of population of United States nearsighted

Hyperopia: farsightedness; usually shorter eyeballs and correct with plus lenses; hyperopic spectacles magnify eyes

American Academy of Pediatrics (AAP) recommendations for vision screening for referral: for newborns  —medical and family history; general inspection; red reflex; ocular motility; at 6 mo of age  —  eye fixation prefer­ence; muscle imbalance; pupillary light reflex; at 3 to 4 yr of age  —  quantitative visual acuity testing; refer child with  —worse than 20/40 vision if <5 yr of age; 2-line difference between eyes; suspected strabismus; abnormal light or red reflex

Examination: pupils  —  light reflex (direct and consensual); Near reflex; observe reflex in light and dark; red reflex; perform examination in ambient light; shine light in one eye and pupil constricts (direct response); should constrict equally in other eye (consensual response); swinging flashlight test used to determine whether afferent pupillary defect present (comparison of function of optic nerves); external adnexa  —  orbit, eyelids, and tear apparatus; look from above if difficult to determine whether one eye proptotic relative to other; many syndromes have eyelid find­ings; blocked tear duct seen in 6% of newborns, although 90% clear within first year; anterior segment — eyelids and lashes, conjunctiva and sclera, anterior chamber, iris, lens, and cornea

Eye motility: basic screening tests include corneal light reflex test and cover test; also 9 cardinal positions; corneal light reflex test able to determine whether eyes straight; Hirschberg test  —  every 1 mm of displacement equal to 7° on ball of eye and 15 prism diopter (PD) deviation; motility problems quantitated with different-sized prisms; PD unit of measurement; Krimsky method  —  prisms balance corneal light reflexes; cover test  —  best; cover and un­cover eyes with paddle, looking for refixation movement; determines whether manifest deviation (tropia) present; also look for phoria (latent deviation); after tropia test, take paddle and put on one eye, then slowly go to other eye and back, never letting both eyes open at same time (helps bring out latent deviation); 75% of all strabismus esotro­pia (in-turning), 20% exotropia (out-turning), and 5% vertical deviations; should move eye in all 9 fields to deter­mine whether equal in all; if same in all fields, consider infantile esotropia or accommodative esotropia; if different in different fields, consider neurologic or mechanical conditions

Intraocular pressure:  applanation tonometry (Tono-Pen) used; infantile glaucoma  —  signs include increased cor­neal size and decreased corneal clarity (clouding); symptoms tearing and blepharospasm; as disease progresses, eye becomes larger and cornea starts to lose its integrity; cornea dry tissue and when stretched, takes on fluid, becom­ing blistery (matte appearance)

Retina: first evaluation with red fundus reflection; examine vitreous for defects and anything floating, nerves, macula (area of most acute vision), retinal vessels, and choroid

Ophthalmoscopy: indirect  —  able to see 33°of field; accessible to ora serrata; degree of stereopsis present (using both eyes), and image inverted and virtual (upside down and backwards); magnification 2 to 4x; done through di­lated pupil; direct  —  only sees 3° of field at time; only reaches equator; no stereopsis (using only 1 eye); gives erect true image (magnified); visual fields  —confrontation and other types used

Wilderness Eye Protection

Howard J. Donner, MD, Emergency Medicine Physician; Medical Officer, Denali Medical Research Project; member, 1997 Nova Everest Expedition; co-author, Field Guide to Wilderness Medicine, Napa, CA

UV photokeratitis: “snow blindness”; dirt and grass reflect minimal UV light; snow reflects ³90%, depending on amount of dirt present and moisture content; if sunglasses not available or lens lost, use duct tape to create slit-like sunglasses; “sunburn” of corneal epithelium; goal to reduce incident UV light by, eg, wearing baseball cap; if glasses for refraction lost, improvise pinhole setup for glasses (by stretching duct tape over frame where lens miss­ing and punching holes onto it)

Speaker’s wilderness kit: ophthalmic anesthetic  —effective; should not be overused or abused (impairs corneal reepithelialization and causes corneal sloughing); use for initial examination; dilute concentrations of anesthetic safer for repeated use; fluorescein strips  —useful for corneal lesions that take up fluorescein; lightweight hand lens  —  magnifies lesions; irrigation fluid  —isotonic saline ideal; drinking water acceptable; cycloplegic agent  —  in UV keratitis, deeper inflammation or uveitis present, and part of pain or discomfort due to ciliary spasm; speaker uses intermediate-acting cycloplegic, eg, cyclopentolate (effective for »12 hr); “pink eye”  —  most not bacterial, probably viral or allergic; bacterial conjunctivitis typically self-limited; antibiotic drops; ophthalmic illuminator (eg, Bluminator)  —  cobalt blue light; high-quality magnifying lens; excellent for examination of eyes, especially af­ter fluorescein staining; corneal ulceration  —  does not require fluorescein; opacities actually leukocytic infiltration (pus); more common in soft contact lens wearers; treatment fluoroquinolones (eg, moxifloxacin [Vigamox], gati­floxacin [Zymar]); topical nonsteroidal anti-inflammatory drug (NSAID)  —  for UV keratitis; safe; systemic analgesics  —  NSAIDs (eg, ibuprofen) or acetaminophen and hydrocodone (Vicodin); cool compresses help­ful; speaker tends to avoid steroids for eye (exacerbate herpes simplex virus infection of cornea)

Environmental variables in protection of eyes: altitude  —  »4% increase in incident UV light with each 1000-ft in­crease in altitude; latitude; reflection of sunlight by surface  —  for water, »2%, depending upon angle of sun, how much reflected and how much absorbed, and surface of water (whether mirror-like or waves present); grass, 1% to 5%; snow, 80% to 90%; time of day  —amount of UV light less 3 hr from noon; ozone  —deteriorating; more ocular problems due to increasing UV light; UV index forecast map for particular location on given day; UV light impli­cated in ocular disorders, eg, pterygium, pinguecula, UV photokeratitis, cataract formation, retinal issues (eg, mac­ular degeneration, retinitis pigmentosa); certain drugs photosensitizing (eg, tetracyclines), and predispose corneal epithelium to UV keratitis

Evaluating sunglasses

Lens material: glass and plastic attenuate certain amount of UV light due to nature of material; acrylic  —  used in inexpensive sunglasses; dangerous (shatters into shards); lightweight; thermoplastic (warp when heated); distor­tion (spherical aberration); scratches easily; allyl diglycol carbonate (CR-39)  —  better plastic; does not shatter into shards; less thermoplastic; better optical clarity and impact resistance; polycarbonate  —  50 times stronger than glass; optical clarity previously not ideal, but now like CR-39; less spherical aberration and better antireflec­tive coating; scratches easily; higher-index plastic than CR-39; more chromatic aberrations; require better antire­flective coating; low-quality polycarbonate used in inexpensive sunglasses, resulting in more spherical and chromatic aberrations; antireflective and hardness coatings not as good; glass  —  excellent; does not scratch eas­ily; potentially dangerous (shatters); new glass relatively impact-resistant; loses strength if scratched (scored); high-index lenses  —  ideal if sunglasses used for refraction (ie, prescription sunglasses); smaller, without “Coke bottle” look; disadvantages more chromatic aberration and requirement for better antireflective coating

Apparent color shift: unable to determine what wavelengths of light blocked by apparent color shift; function of in­dividual’s own aesthetic interests, but affects profession or activities; selective chromatic adaptation  —  ability of brain to adapt to any color shift

Lens contrast: largely function of blue blocking capability; largely empiric classification; lens with high-contrast effect preferable (typically, blue-blocking lenses rose-colored or amber)

Lens coatings: better coatings seen in more expensive sunglasses; on cheaper brands, try “scotch tape adherence test” (antireflective coating removed when scotch tape placed on sunglasses and removed); some coatings chip off when lens flexes; more expensive sunglasses have antireflective coating on back to reduce reflection

UV transmission: important that lens filters out as much UV light as visible light; study by Consumer Reports of in­expesive sunglasses found no case where greater amount of UV transmission than visible light transmission; meth­ods of reducing incident UV light include wearing baseball cap, side shields, or placing duct tape over temples of sunglasses; American National Standards Institute (ANSI)  —  cosmetic lenses need to absorb >70% of UVB and >20% of UVA; general-purpose lenses must absorb >95% of UVB and >60% of UVA; in wilderness, should use sunglasses that meet ANSI special-purpose category (absorbs 99%-100% of UVB and ³60% of UVA)

Visible light transmission: largely personal issue; for extremely bright light situations, need to absorb 95% to 96% of visible light; in stores, perform “mirror test” (not applicable with antireflective coatings); look at mirror in nor­mally lit store; if able to see eyes through sunglasses, not dark enough for outdoor sports; blue light  —  part of visi­ble light; “blue blur”  —  blue visible light refracted in front of rest of visible spectrum; chromatic aberration occurs when allowing blue light through, causing blue blur; theoretically true, but operationally irrelevant; veiling glare  —  caused by internal fluorescence and reflection inside lens of eye; lens becomes less clear as individual ages; blue-blocking lens cuts through veiling glare as well as atmospheric haze; visible blue light involved in dark adaptation, so blocking blue light during day enhances vision at night; high-energy short-wavelength blue light implicated in some retinal pathology, specifically macular degeneration; avoid 100% blue blocker (giving up true color percep­tion); more expensive sunglasses attenuate blue light; recommendation to allow »10% of blue light through

Infrared (IR) transmission: with extreme IR radiation close to eye, cataracts develop over time; question of whether IR, at normal environmental exposure levels, cause cataracts; high-quality sunglasses block IR to varying degrees; “tired eye”  —  claim that keeping eye cool reduces ciliary muscle spasm and fatigue; wearing IR-blocking lens keeps eye comfortable; contact lens floating on tear film; less evaporation of tear film with IR-blocking lens; ther­mal enhancement theory  —  photochemical changes in lens enhanced by increased temperatures

Suggested Reading

American Academy of Pediatrics; Section on Ophthalmology. American Association for Pediatric Ophthalmol­ogy And Strabismus; American Academy of Ophthalmology; American Association of Certified Orthoptists: Red reflex examination in neonates, infants, and children. Pediatrics. 122:1401, 2008; Boev AN et al: Quantitative pupillom­etry: normative data in healthy pediatric volunteers. J Neurosurg. 103(6 Suppl):496, 2005; Fletcher AE et al: Sunlight exposure, antioxidants, and age-related macular degeneration. Arch Ophthalmol. 126:1396, 2008; Forgey WW:  Wil­derness first aid: managing remote area medical issues. Wilderness Environ Med Summer; 20:106, 2009; Kemper AR et al: Preschool vision screening in pediatric practices. Clin Pediatr (Phila). 45:263, 2006; Karpecki P et al: Besifloxiacin ophthalmic suspension 0.6 in patients with bacterial conjunctivitis: A multicenter, prospective, randomized, double-masked, vehicle-controlled, 5-day efficacy and safety study. Clin Ther  Mar 31:514, 2009; Klein BE et al: Lifestyle ex­posures and eye diseases in adults. Am J Ophthalmol. 144:961, 2007; Mainster MA et al: Blue-blocking intraocular lenses: myth or reality? Am J Ophthalmol. 147:8, 2009; Naradzay J, Barish RA: Approach to ophthalmologic emer­gencies. Med Clin North Am Mar 90:105, 2006; Ooi JL et al: Ultraviolet fluorescence photography to detect early sun damage in the eyes of school-aged children. Am J Ophthalmol. 141:294, 2006.