EYE Examination.pptx- ANATOMY AND PHYSIOLOGY

HE ORBIT AND THE EYEBALL.pptx-THE EYE ANAT

1. EYE Examination BSCN 4 2021

2. Assessment of the Eye Examination of external eye structures Visual acuity of distant and near vision Extra Ocular eye movt -cranial nerves Visual fields by confrontation Six cardinal fields of gaze Corneal light reflex Cover/uncover test Pupils and pupillary response

3. Requirements Pen Paper Snellens chart Pen touch Ophthalmoscope Colour testing chart Tonometry-measure IOP Gonioscopy -visualizes the angleof the anterior chamber Perimetry testing-evaluates field of vision and scotomas (blind areas in the visual field)

4. External Eye Structures Inspect the eyelids and eyelashes Observe the position and alignment of the eyeball in the eye socket Inspect all other structures

5. Eye lid symmetry: Patient unable to completely close left upper eyelid due to peripheral CN 7 dysfunction.

6. Structures to Inspect Position and alignment of eyes Eyebrows Eyelids Lacrimal Apparatus Inspection

7. Visual Acuity Near Visual acuity Distance visual acuity

8. Near Visual Acuity Handheld vision chart Normal acuity is 14/14 with or without corrective lenses

9. Near Visual Acuity  Hold card approx 14” from pt’s nose  Ask pt to cover one eye  Read smallest line  Cover other eye and repeat

10. Testing distant vision.

11. Visual acuity Is the resolving power of the eye Measures quality and ability of the eye to resolve varying letter sizes Measured a 6m (20ft) distance for distant vision

12. Purpose-Visual acuity To determine quantify visual acuity To determine severity of vision imparing disorders To classify visual impairment, low vision and blindness Assessment of patient Assess vision related Hx eg type of vision loss (gradual, sudden, transient) as time of onset, duration, Hx of spectacle wear. Assess Hx of red eye, pain swelling, diplopia, photophobia, trauma, surgery Observe abnormality in posture, capacity to comprehend

13. Required instrument Snellen chart Occluder Patient habitual glasses (if present) Pin hole Patient preparation Position patient at 6m from the chart in adequately illuminated room Explain to patient the nature and importance of the test Each eye is tested independently (i.e. one is covered while the other is used to read).

14. Evaluation Record the score of Snellen test as visual acuity unaided, with correction and with pin hole Visual acuity of 6/6 is normal, less than 6/6 is clinically abnormal Functionally, visual acuity less than 6/12 is considered abnormal

15. Extra Ocular eye movt -cranial nerves

16. Extra Ocular eye movt -cranial nerves The movements should be smooth and coordinated. To assess, proceed as follows : Stand in front of the patient. Ask them to follow your finger with their eyes while keeping their head in one position Using your finger, trace an imaginary "H" or rectangular shape in front of them, making sure that your finger moves far enough out and up/down so that you're able to see all appropriate eye movements ( ie lateral and up, lateral down, medial down, medial up). At the end, bring your finger directly in towards the patient's nose. This will cause the patient to look cross-eyed and the pupils should constrict, a response referred to as accommodation . Interpretation: The eyes should be able to easily and smoothly follow your finger.

17. 15. Extraocular Movements Ask the pt to hold his/her head still and to follow your finger with their eyes

18. Cranial Nerves III, IV, & VI- Inspection & Ocular Alignment Have patient “follow your finger with their eyes without moving their head”. Move your finger side to side, then up and down (in an “H” pattern) Look for failure of movement and nystagmus

19. Pathology Isolated lesions of a cranial nerve or the muscle itself can adversely affect extraocular movement. Patients will report diplopia (double vision) when they look in a direction that's affected. This is because the brain can't put together the discordant images in a way that forms a single picture. In response, they will either assume a head tilt that attempts to correct for the abnormal eye positioning or close the abnormal eye. As an example, the patient shown below has a left cranial nerve 6 lesion, which means that his left lateral rectus no longer functions. When he looks right, his vision is normal. However, when he looks left, he experiences double vision as the left eye can't move laterally. This is referred to as horizontal diplopia.

20. Left CN 6 Palsy: Patient was asked to look left. Note that left eye will not abduct.

21. Visual fields: The normal visual field for each eye extends out from the patient in all directions, with an area of overlap directly in front. Field cuts refer to specific regions where the patient has lost their ability to see. This occurs when the transmitted visual impulse is interrupted at some point in its path from the retina to the visual cortex in the back of the brain. You would, in general, only include a visual field assessment if the patient complained of loss of sight; in particular "blind spots" or "holes" in their vision . Visual fields can be crudely assessed as follows:

22. Visual fields assessment The examiner should be nose to nose with the patient, separated by approximately 8 to 12 inches. Each eye is checked separately. The examiner closes one eye and the patient closes the one opposite. The open eyes should then be staring directly at one another. The examiner should move their hand out towards the periphery of his/her visual field on the side where the eyes are open. The finger should be equidistant from both persons. The examiner should then move the wiggling finger in towards them, along an imaginary line drawn between the two persons.The patient and examiner should detect the finger at more or less the same time. The finger is then moved out to the diagonal corners of the field and moved inwards from each of these directions. Testing is then done starting at a point in front of the closed eyes. The wiggling finger is moved towards the open eyes. The other eye is then tested.

23. Meaningful interpretation is predicated upon the examiner having normal fields, as they are using themselves for comparison. If the examiner cannot seem to move their finger to a point that is outside the patient's field don't worry, as it simply means that their fields are normal. Interpretation: This test is rather crude, and it is quite possible to have small visual field defects that would not be apparent on this type of testing. Prior to interpreting abnormal findings, the examiner must understand the normal pathways by which visual impulses travel from the eye to the brain.

24. Assessment of Pupils Normal pupils appear symmetric. To assess for symmetry, look directly at the patient's eyes and note whether they are in the same relative position within the eye socket and of equal size and shape. Anisocoria means that the pupils are unequal in size. When this occurs, the examiner has to determine which is the abnormal eye (i.e. could be either the large or small pupil ). Sympathetic nerves traveling to the eye cause dilation of the pupil. Processes interfering with sympathetic innervation thus lead to constriction . Sympathetics also innervate a small muscle in lid, such that sympathetic lesions also cause an element of ptosis. Interruption along the sympathetic chain is called Horner’s syndrome, a combination of miosis (pupil appears small), ptosis (droopy eye lid) and anhydrosis (lack of sweating on the affected side – though not commonly assessed). On examination, the affected pupil will appear smaller then it’s counterpart, though it should still constrict in response to direct and indirect light. The subsequent dilation phase (when light removed) will be slower than normal.

25. Anisocoria where the larger pupil is the abnormal one Parasympathetics travel with CN3 and cause pupillary constriction. Lesions affecting the parasympathetics result in dilation and may impair other CN3 functions, including: extra occular movements (all muscles except lateral rectus and superior oblique) and raising the eyelid ( levator palpebrae muscle). A third nerve lesion will often cause the eye to appear “down and out” (deviated laterally and downward), with impaired movement, dilated and minimally or non-reactive pupil, and ptosis. Depending on the cause, all of these findings may not be present (e.g. pupillary function can be spared while positioning and movement are affected). Symptoms can include double vision (impaired eye alignment), light sensitivity (from dilation), blurry vision, and headache depending on the underlying cause. The unaffected eye should be normal.

26. Potential causes of a dilated pupil and their associated findings Stroke affecting CN3: The onset of symptoms is usually acute and may include other deficits depending on the location of the stroke. Tumor directly affecting CN3: This can be either a metastatic lesion or a primary CNS tumor compressing CN3. Aneurysm (posterior communicating artery most common): As the aneurysm grows, it compresses CN3. Pupillary dilation is almost always present. Infection, trauma, bleeding, tumor or anything that increases intracranial pressure can lead to herniation. Prior eye surgery, trauma, or injury to pupillary dilators/constrictors.

27. Assessing Pupillary Response to Light: The normal pupil constricts when exposed to bright light, known as the direct response. In addition, light presented to the opposite eye also causes constriction, which is referred to as the consensual response . Constriction is due to the fact that stimulation of the afferents (i.e. sensory nerves, carried with CN 2) in one eye will trigger efferent (i.e. motor, carried with CN 3) activation and subsequent constriction of the pupils of both eyes.

28. To assess pupillary response to light, proceed as follows Turn down the light in your exam room, which will make the pupils dilate a bit. Observe the pupils. Normally, they should appear equal, round and symmetric in their positioning within the orbit. Instruct the patient to look towards a distant area in the room (e.g. the corner where the wall and ceiling meet) while keeping both of their eyes open. You may need to gently remind them throughout the exam to continue looking in that direction as it is very difficult to examine a roving eyeball. Do not ask them to focus on a specific object as this may lead to pupillary constriction. Turn on your ophthalmoscope and adjust the light intensity to mid-range power. The cone of light produced should be a white, medium sized circle. Then assess whether each pupil constricts appropriately in response to direct and indirect stimulation as follows: Shine a light in one eye and note that the pupil constricts (direct response). Then, shine a light in the opposite eye while looking at the first eye, noting again whether pupillary constriction occurs (consensual response). If you're having trouble detecting any change, have the patient close their eye for several seconds and place your hand over their eyebrows to provide additional shade. This helps to make it as dark as possible, encouraging greater pupillary dilation and therefore accentuating any changes. It may be hard to detect the consensual response if the lighting in your room is sub-optimal (i.e. if it's too dark, you won't be able to see the other eye) or if the patient has dark colored irises. Note that you do not need to look through the viewing window of the scope to perform this exam as you are essentially using it as a flashlight.

29. Cranial Nerves II & III- Pupillary Light Reflex

30. Accommodation and convergence Shifting gaze from far to near Normally, pupils constrict

31. Assessment of internal eye structure Include: Assessment of middle vitreous, posterior vitreous, fundus (retina and optic disc Purpose To examine internal eye structure in routine To detect any abnormalities eg opacity in vitreous To detect any abnormality in retina such as cupping of disc, hemorrhage, exudates, scars and tear

32. Assessment of patient Assess Hx of decrease in vision, sudden loss of vision, DM, HTN, high myopia, glaucoma and other systemic codns Evaluate presence of cataract, ocular movt and disease of anterior segments Assess best corrected visual acuity Assess Hx of trauma or swelling of eye and adnexa

33. Requirements Ophthalmoscope

34. Vitreous examination

35. Examination of the retina

36. Abnormalities of the Fundus continued on next slide