Medical brain notes 32

  The Ophthalmic Examination Equipment The  basic equipment  for the ophthalmic examination includes the following instruments: ❖   Direct ophthalmoscope  for examining the fundus (Fig. 1. 1 ). ❖  Focused light  (Fig. 1. 1 ) for examining the reaction of the pupil and the ante-rior chamber. ❖  Aspheric lens  (Fig. 1. 1 ) for examining the anterior chamber. ❖  Eye chart  for testing visual acuity at a distance of 5 meters (20 feet)(Fig. 1. 2 ). ❖   Binocular loupes  for removing corneal and conjunctival foreign bodies. ❖  Desmarres eyelid retractor  and  glass rod  or  sterile cotton swab  for eyelideversion (Fig. 1. 3 ). Foreign-body needle  for removing superficial corneal foreign bodies (Fig. 1. 3 ). Recommended medications: ❖  Topical anesthetic  (such as oxybuprocaine 0.4% eyedrops) to provide localanesthesia during removal of conjunctival and corneal foreign bodies and supe...

  History A complete history includes four aspects: 1.   Family history.  Many eye disorders are hereditary or of higher incidence inmembers of the same family. Examples include refractive errors, stra-bismus, cataract, glaucoma, retinal detachment, and retinal dystrophy. 2.   Medical history.  As ocular changes may be related to systemic disorders,this possibility must be explored. Conditions affecting the eyes include diabetes mellitus, hypertension, infectious diseases, rheumatic disorders, skin diseases, and surgery. Eye disorders such as corticosteroid-induced glaucoma, corticosteroid-induced cataract, and chloroquine-induced maculopathy can occur as a result of treatment with medications such as steroids, chloroquine, Amiodarone, Myambutol, or chlorpromazine (see table in Appendix). 3.           Ophthalmic history. The examiner should inquire about corrective lenses,strabismus or amblyopia, posttraumatic conditi...

  Visual Acuity Visual acuity, the sharpness of near and distance vision, is tested separately for each eye. One eye is covered with a piece of paper or the palm of the hand placed lightly over the eye. The fingers should not be used to cover the eye because the patient will be able to see between them (Fig. 1. 4 ). The  general practitioner  or  student  can perform an  approximate test ofvisual acuity . The patient is first asked to identify certain visual symbolsreferred to as optotypes (see Fig. 1. 2 ) at a distance of 5 meters or 20 feet ( test ofdistance vision ). These visual symbols are designed so that optotypes of a cer-tain size can barely be resolved by the normal eye at a specified distance (this standard distance is specified in meters next to the respective symbol). The eye charts must be clean and well illuminated for the examination. The sharpness of vision measured is expressed as a fraction: Normal visual acuity  is 5/5 (20/20), or 1...

  Ocular Motility With the patient’s head immobilized, the examiner asks the patient to look in each of the  nine diagnostic positions of gaze:  1, straight ahead; 2, right; 3, upper right; 4, up; 5, upper left; 6, left; 7, lower left; 8, down; and 9, lower right (Fig. 1. 5 ). This allows the examiner to diagnose strabismus, paralysis of ocular muscles, and gaze paresis. Evaluating the  six cardinal directions of gaze  (right, left, upper right, lower right, upper left, lower left) is sufficient when examining paralysis of the one of the six extraocular muscles. The motion impairment of the eye resulting from paralysis of an ocular muscle will be most evident in these positions. Only one of the rectus muscles is involved in each of the left and right positions of gaze (lateral or medial rectus muscle). All other directions of gaze involve several muscles.

  Binocular Alignment Binocular alignment is evaluated with a  cover test . The examiner holds a point light source beneath his or her own eyes and observes the  light reflec-tions in the patient’s corneas  in the near field (40 cm) and at a distance (5 m).The  reflections  are normally  in the center of each pupil.  If the corneal reflection is not in the center of the pupil in one eye, then a tropia is present in that eye. Then the examiner covers one eye with a hand or an occluder (Fig. 1. 6 ) and tests whether the  uncovered eye  makes a compensatory movement. Compen-satory movement of the eye indicates the presence of tropia. However, there will also be a lack of compensatory movement if the eye is blind. The cover test is then repeated with the other eye. If tropia is present in a newborn with extremely poor vision, the baby will not tolerate the good eye being covered.

  Examination of the Eyelids and Nasolacrimal Duct The  upper eyelid  covers the superior margin of the cornea. A few millimeters of the sclera will be visible above the  lower eyelid.  The  eyelids  are in direct con-tact with the eyeball. Stenosis of the nasolacrimal duct produces a  pool of tears in the medialangle  of the eye with  lacrimation  (epiphora). In inflammation of the lacrimalsac, pressure on the nasolacrimal sac frequently causes a reflux of  mucus orpus from the inferior punctum.  Patency of the nasolacrimal duct is tested byinstilling a 10% fluorescein solution in the conjunctival sac of the eye. If the dye is present in nasal mucus expelled into paper tissue after two minutes, the lacrimal duct is open.

  Examination of the Conjunctiva The conjunctiva is examined by direct inspection. The bulbar conjunctiva is directly visible between the eyelids; the palpebral conjunctiva can only be examined by everting the upper or lower eyelid. The normal conjunctiva is smooth, shiny, and moist. The examiner should be alert to any reddening, secretion, thickening, scars, or foreign bodies. Eversion of the lower eyelid. The patient looks up while the examiner pullsthe eyelid downward close to the anterior margin (Fig. 1. 7 ). This exposes the conjunctiva and the posterior surface of the lower eyelid. Eversion of the upper eyelid. Simple eversion (Fig. 1. 8 ). The patient is asked tolook down. The patient should repeatedly be told to relax and to avoid tightly shutting the opposite eye. This relaxes the levator palpebrae superioris and orbicularis oculi muscles. The examiner grasps the eyelashes of the upper eyelid between the thumb and forefinger and everts the eyelid against a glass rod or swa...

  Examination of the Cornea The cornea is examined with a  point light source  and a  loupe  (Fig. 1. 10 ). The cornea is  smooth ,  clear , and  reflective . The reflection is distorted in the pres-ence of corneal disorders. Epithelial defects, which are also very painful, will take on an intense green color after application of fluorescein dye; corneal infiltrates and scars are grayish white. Evaluating corneal sensitivity is also important. Sensitivity is evaluated bilaterally to detect possible differences in the reaction of both eyes. The patient looks straight ahead during the exami-nation. The examiner holds the upper eyelid to prevent reflexive closing and touches the cornea anteriorly (Fig. 1. 11 ). Decreased sensitivity can provide information about trigeminal or facial neuropathy, or may be a sign of a viral infection of the cornea.

  Examination of the Anterior Chamber The anterior chamber is filled with clear aqueous humor. Cellular infiltration and collection of pus may occur (hypopyon). Bleeding in the anterior cham-ber is referred to as hyphema. It is important to  evaluate the depth of the anterior chamber . In a cham-ber of  normal depth , the iris can be well illuminated by a lateral light source (Fig. 1. 12 ). In a  shallow anterior chamber  there will be a medial shadow on the iris. The pupillary dilation should be avoided in patients with shallow ante-rior chambers because of the risk of precipitating a glaucoma attack. Older patients with “small” hyperopic eyes are a particular risk group. Dilation of the pupil with a mydriatic is  contraindicated  in patients with a shallow anterior chamber due to the risk of precipitating angle closure glaucoma.

  Examination of the Lens   The ophthalmologist uses a  slit lamp  to examine the lens. The eye can also be examined with a  focused light  if necessary.   Direct illumination  will produce a red reflection of the fundus if the lens is clear and  gray shadows  if lens opacities are present. The examiner then illuminates the eye  laterally  with a focused light held as close to the eye as possible and inspects the eye through a +14 diopter loupe (see Fig. 1. 10 ). This examination permits better evaluation of changes in the conjunctiva, cornea, and anterior chamber. With severe opacification of the lens, a gray coloration will be vis-ible in the pupillary plane. Any such light-scattering opacity is referred to as a cataract. Indirect ophthalmoscopy is usually performed by the ophthalmologist  and produces a laterally reversed image of the fundus. Less experienced examiners will prefer  direct ophthalmoscopy . Here, the...

  Confrontation Field Testing Confrontation testing provides gross screening of the field of vision where perimetry tests are not available. The patient faces the examiner at a standard distance of 1 m with his or her eyes at the same level as the examiner’s (Fig. 1. 14 ). Both focus on the other’s opposite eye (i.e., the patient’s left eye focuses on the examiner’s right eye) while covering their contralateral eye with the palm of the hand. The examiner moves an object such as a pen, cotton swab, or finger from the periphery toward the midline in all four quadrants (in the superior and infe-rior nasal fields and superior and inferior temporal fields). A patient with a  normal field of vision  will see the object at the same time as the examiner; apatient with an  abnormal or restricted field of vision  will see the object later than the examiner. Confrontation testing is a gross method of assessing the field of vision. It can be used to diagnose a severely rest...

  Measurement of Intraocular Pressure With the patient’s eyes closed, the examiner places his or her hands on the patient’s head and palpates the eye through the upper eyelid with both index fingers (Fig. 1. 15 ). The test is repeated on the contralateral eye for comparison. A “rock hard” eyeball only occurs in acute angle closure glaucoma. Slight increases in intraocular pressure such as occur in chronic glau-coma will not be palpable.

  Eyedrops, Ointment, and Bandages Eyedrops and ointment should be administered posterior to the  everted lowereyelid . One drop or strip of ointment approximately 1 cm long should beadministered  laterally to the inferior conjunctival sac . To avoid injury to the eye, drops should be administered with the patient  supine  (Fig. 1. 16 ) or seated with the  head tilted back and supported . The person administering the medi-cation places his or her hand on the patient’s face for support. Bottles and tubes must not come in contact with the patient’s eyelashes as they might otherwise become contaminated. Allow the drops or strip of ointment to drop into the conjunctival sac. Eye ointment should not be administered following ocular trauma as this may complicate subsequent examination or surgery. Dilation of the pupils with a mydriatic in unconscious patients should be avoided as this complicates neurologic examination. Eye bandage. A sterile swab or commercially...

  Basic Knowledge Protective function of the eyelids:  The eyelids are folds of muscular softtissue that lie anterior to the eyeball and protect it from injury. Their  shape  is such that the eyeball is completely covered when they are closed. Strong mechanical, optical, and acoustic stimuli (such as a foreign body, blinding light, or sudden loud noise) “automatically” elicit an  eye closing reflex . The cornea is also protected by an additional upward movement of the eyeball ( Bell’s phenomenon ).  Regular blinking  (20 – 30 times a minute) helps to uni-formly distribute glandular secretions and tears over the conjunctiva and cor-nea, keeping them from drying out. Structure of the eyelids:  The eyelids consist of superficial and deep layers(Fig. 2. 1 ). ❖ Superficial layer: –  Thin, well vascularized layer of  skin . –  Sweat glands. – Modified  sweat gland  and  sebaceous glands  (ciliary glands or  glands...

  Examination Methods The eyelids are examined by direct inspection under a bright light. A slit lamp may be used for this purpose.  Bilateral inspection of the eyelids  includes the following aspects: ❖  Eyelid position:  Normally the margins of the eyelids are in contact with theeyeball and the puncta are submerged in the lacus lacrimalis. ❖  Width of the palpebral fissure:  When the eye is open and looking straightahead, the upper lid should cover the superior margin of the cornea by about 2 mm. Occasionally a thin strip of sclera will be visible between the cornea and the margin of the lower lid. The width of the palpebral fissure is normally 6 – 10 mm, and the distance between the lateral and medial angles of the eye is 28 – 30 mm (Fig. 2. 2 ). Varying widths of the gaps between the eyelids may be a sign of protrusion of the eyeball, enophthal-mos, or eyeballs of varying size (Table 2. 1 ). ❖  Skin of the eyelid:  The skin of the eyelid ...