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OPTHALMOLOGY > Lens > Flashcards

Flashcards in Lens Deck (31):
1

Function

Cornea and lens: main refractive surfaces of the eye--> focusing a clear image on the retina.

2

Function

Cornea and lens: main refractive surfaces of the eye--> focusing a clear image on the retina.

3

Function

Cornea and lens: main refractive surfaces of the eye--> focusing a clear image on the retina.

4

Function

Cornea and lens: main refractive surfaces of the eye--> focusing a clear image on the retina.

5

Blood and nerve supply

Does not have a nerve or blood supply. Nutrients diffuse into the lens from the aqueous and the vitreous humour.

6

Anatomy of the lens

The lens consists of three transparent parts:
1. Capsule: a thin outer membrane.
2. Cortex: a soft layer under the capsule. 3. 3. Nucleus: a harder central core that only develops later and is not present in children and young adults.

7

Accommodation

1. Ciliary body functions as a circular muscle.
2. Thin filamentous zonules from the ciliary body suspend the lens in position between the iris anteriorly and the vitreous posteriorly.
3. Contraction of the ciliary muscle --> < tension on the zonules--> Allows lens to assume its relaxed and more spherical form.
4. > bending light rays --> bring the focal point closer to lens and near object into focus.

8

Cataract
Definition
Classification
Causes
Symptoms
Diagnosis
Special investigations
Complications
Treatment

DEFINITION:
- Any opacity/discolouration of lens that varies from a local opacity to total loss of clarity.
- Also known as lens sclerosis

CLASSIFICATION:
1. Subcapsular: in the cortex immediately under the capsule.
2. Cortical: in the deeper cortex.
3. Nuclear.

INCIDENCE:
65-75 years: 70% have some degree of lens sclerosis, 20% have visual disability.
75-85 years: 90% have some degree of lens sclerosis, 40% have visual disability.

CAUSES
1. Age-related: ageing of the lens is the commonest cause of cataract.
2. Metabolic: many metabolic diseases cause or accelerate cataract formation.
Diabetes mellitus is by far the most important.
3. Drugs: systemic and topical steroids are the most important.
4. Trauma: blunt or sharp.
5. Uveitis.
6. Infections of the fetus: e.g. rubella, CMV, toxoplasmosis.
7. Smoking.

SYMPTOMS
1. Gradual painless loss of vision.
2. Monocular diplopia may occur if the lens develops areas of differing refractive power. 3. Vision may vary with illumination, and may improve in either bright or dim light.
4. A nuclear cataract often increases the refractive power of the lens and myopia results--> patient is once again able to read without reading glasses.

DIAGNOSIS
1. VA is reduced in a comfortable white eye. 2. Inspection: leukocoria only if advanced.
3. Ophthalmoscopy:
- Opacity in the red reflex localised in or just behind the level of the pupil.
- Advanced the red reflex may be absent.
- Dull or absent image of the fundus.
4. Blood glucose in patients under 50 years of age.

COMPLICA TIONS
1. Phacolytic Glucoma
Lens is completely white--> lens protein may leak through lens capsule into the aqueous humour--> Macrophages swollen with phagocytosed lens material block the trabecular meshwork and obstruct aqueous outflow--> secondary open angle glaucoma.
RX: lens extraction.
2. Phacoanaphylactic uveitis
Lens capsule rupture--> releases lens protein into aqueous humour--> inflammatory reaction--> anterior uveitis.
RX: lens extraction and steroids.

TREATMENT:
1. Non-surgical:
1. information diagnosis and prognosis.
2. change spectacle strength .
3. A magnifying glass/ change of illumination for reading

2. Surgical:
Indications:
1. No longer able to perform their everyday tasks such as driving a car or doing their job.
2. Usually surgery is not performed until the VA with spectacles drops below 6/9.
3. Where it is essential to be able to see the fundus better e.g. patient with diabetes.
4. Complications of cataract: phacolytic glaucoma, phacoanaphylactic uveitis.
Contraindications:
1. The patient does not want surgery.
2. Supportive management results in adequate functional vision.
3. Where surgery will not improve the vision e.g. macular degeneration.
Procedure:
LENS EXTRACTION & INTRAOCULAR LENS IMPLANTATION
1. A small incision in clear cornea near the limbus provides access to the lens.
2. A round opening is made in the anterior capsule through which the nucleus is broken up by ultrasound in a process known as phacoemulsification.
3. The cortex and emulsified nucleus are removed by aspiration, leaving the peripheral and posterior capsular bag intact.
4. An intraocular lens is then inserted into the capsular bag through its anterior opening.
5. Vision is restored to 6/12 or better in approximately 90% of eyes without other pathology.

9

ECTOPIA LENTIS
Types
Causes
Complications
Treatment

TYPES:
1. Subluxation: the lens is only partially displaced due to rupture of some of the zonules.
2. Dislocation: the lens is completely displaced into either the anterior chamber or the vitreous humour.

CAUSES
1. Trauma
2. Collagen disease where the zonules are weak, such as Marfan’s disease.

COMPLICA TION
1. Displaced lens may cause pupil block
2. acute angle closure glaucoma.

TREATMENT
1. Refer to ophthalmologist
2. Lens extraction if there is a significant reduction in vision or if lens displacement is severe.

10

CONGENITAL CATARACT

Diagnosis:
1. Red reflex at birth
2. No red reflex--> eye examination with dialted pupils

Treatment:
1. Surgery is performed before the age of 3 months in order to prevent amblyopia from developing.

Prognosis: Visual results are unfortunately often disappointing.

11

Blood and nerve supply

Does not have a nerve or blood supply. Nutrients diffuse into the lens from the aqueous and the vitreous humour.

12

Anatomy of the lens

The lens consists of three transparent parts:
1. Capsule: a thin outer membrane.
2. Cortex: a soft layer under the capsule. 3. 3. Nucleus: a harder central core that only develops later and is not present in children and young adults.

13

Accommodation

1. Ciliary body functions as a circular muscle.
2. Thin filamentous zonules from the ciliary body suspend the lens in position between the iris anteriorly and the vitreous posteriorly.
3. Contraction of the ciliary muscle --> < tension on the zonules--> Allows lens to assume its relaxed and more spherical form.
4. > bending light rays --> bring the focal point closer to lens and near object into focus.

14

Cataract:
Definition
Classification
Causes
Symptoms
Diagnosis
Special investigations
Complications
Treatment

DEFINITION:
- Any opacity/discolouration of lens that varies from a local opacity to total loss of clarity.
- Also known as lens sclerosis

CLASSIFICATION:
1. Subcapsular: in the cortex immediately under the capsule.
2. Cortical: in the deeper cortex.
3. Nuclear.

INCIDENCE:
65-75 years: 70% have some degree of lens sclerosis, 20% have visual disability.
75-85 years: 90% have some degree of lens sclerosis, 40% have visual disability.

CAUSES
1. Age-related: ageing of the lens is the commonest cause of cataract.
2. Metabolic: many metabolic diseases cause or accelerate cataract formation.
Diabetes mellitus is by far the most important.
3. Drugs: systemic and topical steroids are the most important.
4. Trauma: blunt or sharp.
5. Uveitis.
6. Infections of the fetus: e.g. rubella, CMV, toxoplasmosis.
7. Smoking.

SYMPTOMS
1. Gradual painless loss of vision.
2. Monocular diplopia may occur if the lens develops areas of differing refractive power. 3. Vision may vary with illumination, and may improve in either bright or dim light.
4. A nuclear cataract often increases the refractive power of the lens and myopia results--> patient is once again able to read without reading glasses.

DIAGNOSIS
1. VA is reduced in a comfortable white eye. 2. Inspection: leukocoria only if advanced.
3. Ophthalmoscopy:
- Opacity in the red reflex localised in or just behind the level of the pupil.
- Advanced the red reflex may be absent.
- Dull or absent image of the fundus.
4. Blood glucose in patients under 50 years of age.

COMPLICA TIONS
1. Phacolytic Glucoma
Lens is completely white--> lens protein may leak through lens capsule into the aqueous humour--> Macrophages swollen with phagocytosed lens material block the trabecular meshwork and obstruct aqueous outflow--> secondary open angle glaucoma.
RX: lens extraction.
2. Phacoanaphylactic uveitis
Lens capsule rupture--> releases lens protein into aqueous humour--> inflammatory reaction--> anterior uveitis.
RX: lens extraction and steroids.

TREATMENT:
1. Non-surgical:
1. information diagnosis and prognosis.
2. change spectacle strength .
3. A magnifying glass/ change of illumination for reading

2. Surgical:
Indications:
1. No longer able to perform their everyday tasks such as driving a car or doing their job.
2. Usually surgery is not performed until the VA with spectacles drops below 6/9.
3. Where it is essential to be able to see the fundus better e.g. patient with diabetes.
4. Complications of cataract: phacolytic glaucoma, phacoanaphylactic uveitis.
Contraindications:
1. The patient does not want surgery.
2. Supportive management results in adequate functional vision.
3. Where surgery will not improve the vision e.g. macular degeneration.
Procedure:
LENS EXTRACTION & INTRAOCULAR LENS IMPLANTATION
1. A small incision in clear cornea near the limbus provides access to the lens.
2. A round opening is made in the anterior capsule through which the nucleus is broken up by ultrasound in a process known as phacoemulsification.
3. The cortex and emulsified nucleus are removed by aspiration, leaving the peripheral and posterior capsular bag intact.
4. An intraocular lens is then inserted into the capsular bag through its anterior opening.
5. Vision is restored to 6/12 or better in approximately 90% of eyes without other pathology.

15

Ectopia Lentis:
Types
Causes
Complications
Treatment

TYPES:
1. Subluxation: the lens is only partially displaced due to rupture of some of the zonules.
2. Dislocation: the lens is completely displaced into either the anterior chamber or the vitreous humour.

CAUSES
1. Trauma
2. Collagen disease where the zonules are weak, such as Marfan’s disease.

COMPLICA TION
1. Displaced lens may cause pupil block
2. acute angle closure glaucoma.

TREATMENT
1. Refer to ophthalmologist
2. Lens extraction if there is a significant reduction in vision or if lens displacement is severe.

16

CONGENITAL CATARACT:
Diagnosis
Treatment
Prognosis

Diagnosis:
1. Red reflex at birth
2. No red reflex--> eye examination with dialted pupils

Treatment:
1. Surgery is performed before the age of 3 months in order to prevent amblyopia from developing.

Prognosis: Visual results are unfortunately often disappointing.

17

Lens pathology (3)

1. Cataracts
2. Congenital Cataracts
3. Ectopia Lentis

18

Blood and nerve supply

Does not have a nerve or blood supply. Nutrients diffuse into the lens from the aqueous and the vitreous humour.

19

Anatomy of the lens

The lens consists of three transparent parts:
1. Capsule: a thin outer membrane.
2. Cortex: a soft layer under the capsule. 3. 3. Nucleus: a harder central core that only develops later and is not present in children and young adults.

20

Accommodation

1. Ciliary body functions as a circular muscle.
2. Thin filamentous zonules from the ciliary body suspend the lens in position between the iris anteriorly and the vitreous posteriorly.
3. Contraction of the ciliary muscle --> < tension on the zonules--> Allows lens to assume its relaxed and more spherical form.
4. > bending light rays --> bring the focal point closer to lens and near object into focus.

21

Cataract:
Definition
Classification
Causes
Symptoms
Diagnosis
Special investigations
Complications
Treatment

DEFINITION:
- Any opacity/discolouration of lens that varies from a local opacity to total loss of clarity.
- Also known as lens sclerosis

CLASSIFICATION:
1. Subcapsular: in the cortex immediately under the capsule.
2. Cortical: in the deeper cortex.
3. Nuclear.

INCIDENCE:
65-75 years: 70% have some degree of lens sclerosis, 20% have visual disability.
75-85 years: 90% have some degree of lens sclerosis, 40% have visual disability.

CAUSES
1. Age-related: ageing of the lens is the commonest cause of cataract.
2. Metabolic: many metabolic diseases cause or accelerate cataract formation.
Diabetes mellitus is by far the most important.
3. Drugs: systemic and topical steroids are the most important.
4. Trauma: blunt or sharp.
5. Uveitis.
6. Infections of the fetus: e.g. rubella, CMV, toxoplasmosis.
7. Smoking.

SYMPTOMS
1. Gradual painless loss of vision.
2. Monocular diplopia may occur if the lens develops areas of differing refractive power. 3. Vision may vary with illumination, and may improve in either bright or dim light.
4. A nuclear cataract often increases the refractive power of the lens and myopia results--> patient is once again able to read without reading glasses.

DIAGNOSIS
1. VA is reduced in a comfortable white eye. 2. Inspection: leukocoria only if advanced.
3. Ophthalmoscopy:
- Opacity in the red reflex localised in or just behind the level of the pupil.
- Advanced the red reflex may be absent.
- Dull or absent image of the fundus.
4. Blood glucose in patients under 50 years of age.

COMPLICA TIONS
1. Phacolytic Glucoma
Lens is completely white--> lens protein may leak through lens capsule into the aqueous humour--> Macrophages swollen with phagocytosed lens material block the trabecular meshwork and obstruct aqueous outflow--> secondary open angle glaucoma.
RX: lens extraction.
2. Phacoanaphylactic uveitis
Lens capsule rupture--> releases lens protein into aqueous humour--> inflammatory reaction--> anterior uveitis.
RX: lens extraction and steroids.

TREATMENT:
1. Non-surgical:
1. information diagnosis and prognosis.
2. change spectacle strength .
3. A magnifying glass/ change of illumination for reading

2. Surgical:
Indications:
1. No longer able to perform their everyday tasks such as driving a car or doing their job.
2. Usually surgery is not performed until the VA with spectacles drops below 6/9.
3. Where it is essential to be able to see the fundus better e.g. patient with diabetes.
4. Complications of cataract: phacolytic glaucoma, phacoanaphylactic uveitis.
Contraindications:
1. The patient does not want surgery.
2. Supportive management results in adequate functional vision.
3. Where surgery will not improve the vision e.g. macular degeneration.
Procedure:
LENS EXTRACTION & INTRAOCULAR LENS IMPLANTATION
1. A small incision in clear cornea near the limbus provides access to the lens.
2. A round opening is made in the anterior capsule through which the nucleus is broken up by ultrasound in a process known as phacoemulsification.
3. The cortex and emulsified nucleus are removed by aspiration, leaving the peripheral and posterior capsular bag intact.
4. An intraocular lens is then inserted into the capsular bag through its anterior opening.
5. Vision is restored to 6/12 or better in approximately 90% of eyes without other pathology.

22

Ectopia Lentis:
Types
Causes
Complications
Treatment

TYPES:
1. Subluxation: the lens is only partially displaced due to rupture of some of the zonules.
2. Dislocation: the lens is completely displaced into either the anterior chamber or the vitreous humour.

CAUSES
1. Trauma
2. Collagen disease where the zonules are weak, such as Marfan’s disease.

COMPLICA TION
1. Displaced lens may cause pupil block
2. acute angle closure glaucoma.

TREATMENT
1. Refer to ophthalmologist
2. Lens extraction if there is a significant reduction in vision or if lens displacement is severe.

23

CONGENITAL CATARACT:
Diagnosis
Treatment
Prognosis

Diagnosis:
1. Red reflex at birth
2. No red reflex--> eye examination with dialted pupils

Treatment:
1. Surgery is performed before the age of 3 months in order to prevent amblyopia from developing.

Prognosis: Visual results are unfortunately often disappointing.

24

Lens pathology (3)

1. Cataracts
2. Congenital Cataracts
3. Ectopia Lentis

25

Blood and nerve supply

Does not have a nerve or blood supply. Nutrients diffuse into the lens from the aqueous and the vitreous humour.

26

Anatomy of the lens

The lens consists of three transparent parts:
1. Capsule: a thin outer membrane.
2. Cortex: a soft layer under the capsule. 3. 3. Nucleus: a harder central core that only develops later and is not present in children and young adults.

27

Accommodation

1. Ciliary body functions as a circular muscle.
2. Thin filamentous zonules from the ciliary body suspend the lens in position between the iris anteriorly and the vitreous posteriorly.
3. Contraction of the ciliary muscle --> < tension on the zonules--> Allows lens to assume its relaxed and more spherical form.
4. > bending light rays --> bring the focal point closer to lens and near object into focus.

28

Cataract:
Definition
Classification
Causes
Symptoms
Diagnosis
Special investigations
Complications
Treatment

DEFINITION:
- Any opacity/discolouration of lens that varies from a local opacity to total loss of clarity.
- Also known as lens sclerosis

CLASSIFICATION:
1. Subcapsular: in the cortex immediately under the capsule.
2. Cortical: in the deeper cortex.
3. Nuclear.

INCIDENCE:
65-75 years: 70% have some degree of lens sclerosis, 20% have visual disability.
75-85 years: 90% have some degree of lens sclerosis, 40% have visual disability.

CAUSES
1. Age-related: ageing of the lens is the commonest cause of cataract.
2. Metabolic: many metabolic diseases cause or accelerate cataract formation.
Diabetes mellitus is by far the most important.
3. Drugs: systemic and topical steroids are the most important.
4. Trauma: blunt or sharp.
5. Uveitis.
6. Infections of the fetus: e.g. rubella, CMV, toxoplasmosis.
7. Smoking.

SYMPTOMS
1. Gradual painless loss of vision.
2. Monocular diplopia may occur if the lens develops areas of differing refractive power. 3. Vision may vary with illumination, and may improve in either bright or dim light.
4. A nuclear cataract often increases the refractive power of the lens and myopia results--> patient is once again able to read without reading glasses.

DIAGNOSIS
1. VA is reduced in a comfortable white eye. 2. Inspection: leukocoria only if advanced.
3. Ophthalmoscopy:
- Opacity in the red reflex localised in or just behind the level of the pupil.
- Advanced the red reflex may be absent.
- Dull or absent image of the fundus.
4. Blood glucose in patients under 50 years of age.

COMPLICA TIONS
1. Phacolytic Glucoma
Lens is completely white--> lens protein may leak through lens capsule into the aqueous humour--> Macrophages swollen with phagocytosed lens material block the trabecular meshwork and obstruct aqueous outflow--> secondary open angle glaucoma.
RX: lens extraction.
2. Phacoanaphylactic uveitis
Lens capsule rupture--> releases lens protein into aqueous humour--> inflammatory reaction--> anterior uveitis.
RX: lens extraction and steroids.

TREATMENT:
1. Non-surgical:
1. information diagnosis and prognosis.
2. change spectacle strength .
3. A magnifying glass/ change of illumination for reading

2. Surgical:
Indications:
1. No longer able to perform their everyday tasks such as driving a car or doing their job.
2. Usually surgery is not performed until the VA with spectacles drops below 6/9.
3. Where it is essential to be able to see the fundus better e.g. patient with diabetes.
4. Complications of cataract: phacolytic glaucoma, phacoanaphylactic uveitis.
Contraindications:
1. The patient does not want surgery.
2. Supportive management results in adequate functional vision.
3. Where surgery will not improve the vision e.g. macular degeneration.
Procedure:
LENS EXTRACTION & INTRAOCULAR LENS IMPLANTATION
1. A small incision in clear cornea near the limbus provides access to the lens.
2. A round opening is made in the anterior capsule through which the nucleus is broken up by ultrasound in a process known as phacoemulsification.
3. The cortex and emulsified nucleus are removed by aspiration, leaving the peripheral and posterior capsular bag intact.
4. An intraocular lens is then inserted into the capsular bag through its anterior opening.
5. Vision is restored to 6/12 or better in approximately 90% of eyes without other pathology.

29

Ectopia Lentis:
Types
Causes
Complications
Treatment

TYPES:
1. Subluxation: the lens is only partially displaced due to rupture of some of the zonules.
2. Dislocation: the lens is completely displaced into either the anterior chamber or the vitreous humour.

CAUSES
1. Trauma
2. Collagen disease where the zonules are weak, such as Marfan’s disease.

COMPLICA TION
1. Displaced lens may cause pupil block
2. acute angle closure glaucoma.

TREATMENT
1. Refer to ophthalmologist
2. Lens extraction if there is a significant reduction in vision or if lens displacement is severe.

30

CONGENITAL CATARACT:
Diagnosis
Treatment
Prognosis

Diagnosis:
1. Red reflex at birth
2. No red reflex--> eye examination with dialted pupils

Treatment:
1. Surgery is performed before the age of 3 months in order to prevent amblyopia from developing.

Prognosis: Visual results are unfortunately often disappointing.

31

Lens pathology (3)

1. Cataracts
2. Congenital Cataracts
3. Ectopia Lentis