Lens and cataract

Lens and cataract

1. Lens and Cataract Mohammad Tailakh 5 th year medical student - JUH

2. Learning objectives To understand: Lens and their abnormalities . The signs, symptoms, pathology and causes of cataract. The reasons for undertaking cataract surgery. The principles of cataract surgery. The complications of cataract surgery. Congenital cataract.

3. Lens Is a transparent biconvex structure immediately behind the iris, held in position by the suspensory ligament ( zonule ), The zonule attaches the equator of the lens to the ciliary body. It is the second major refractive element of the eye, the cornea being the first . It Focuses light on the retina Derived from ectoderm It is avascular It is highly elastic; but it hardens with age Disease may affect structure, shape and position of the lens.

4. Histology of the Lens Lens Capsule (LC) Lens Epithelium (LE) Differentiating Lens Fibers (DLF) Mature Lens Fibers (MLF)

5. Histology of the Lens The lens capsule is a thick, homogenous external lamina formed by proteoglycans & collagen IV for protection of underlying structures and attachment of zonules . The lens epithelium is a single layer of cuboid cells, present only on the anterior surface of the lens. The lens fibers align parallel to the epithelium. Differentiating lens fibers: still have their nuclei, but are greatly elongated, and their cytoplasm is filled with proteins called crystallins . The mature lens fibers: lost their nuclei and became densely packed to produce a unique transparent structure.

6. Change in lens shape Abnormal lens shape is very unusual. The curvature of the anterior part of the lens may be increased centrally ( anterior lenticonus ) in Alport ’ s syndrome, a recessively inherited condition of deafness and nephropathy. An abnormally small lens may be associated with short stature and other skeletal abnormalities.

7. Change in lens position ( ectopia lentis ) Weakness of the zonule causes lens displacement. The lens takes up a more rounded form and the eye becomes more myopic. This may be seen in: • trauma; certain syndromes (e.g. Marfan syndrome) the lens is usually displaced upwards. • inborn errors of metabolism (e.g. homocystinuria ) the lens is usually displaced downwards.

8. Cataract

9. Cataract Cataract is the name given to any light - scattering opacity within the lens wherever it is located It is the opacification of the lens of the eye Opacification: The process of becoming cloudy or opaque Cataract is the commonest cause of treatable blindness in the world.

10. Causes : the commonest cause of cataract is aging because of cumulative exposure to environmental and other influences, such as smoking, UV radiation and elevated blood sugar levels. Ocular causes: Trauma. Uveitis. High myopia. Topical medication (particularly steroid eye drops). Intraocular tumor.

11. Causes : Systemic causes of cataract: Diabetes. Other metabolic disorders (including galactosaemia , hypocalcaemia , Fabry disease). Systemic drugs (particularly steroids, chlorpromazine). Infection (congenital rubella). Myotonic dystrophy. Atopic dermatitis. Systemic syndromes (Down’s, Lowe’s). Congenital, including inherited, cataract. X - Radiation.

12. Symptoms: a painless loss of vision glare “difficulty seeing in bright light” a change in refraction. In infants, cataract causes amblyopia ( a failure of visual maturation ) by depriving the retina of a formed image at a critical stage of visual development. Note : Infants with suspected cataract or a family history of congenital cataracts should be assessed by an ophthalmologist shortly after birth, as a matter of urgency.

13. Signs: 1. Visual acuity is reduced. 2. Loss of red reflex when examined with a direct ophthalmoscope. Other features to suggest an ocular cause for the cataract may be found, for example pigment deposition on the lens suggesting previous inflammation, or damage to the iris suggesting previous ocular trauma Slit - lamp examination allows the cataract to be examined in detail, and the exact site of the opacity in the lens can be identified.

14. Classification Classification of cataract according to the site: 1. Cortical 2. Nuclear 3. Subcapsular (anterior or posterior) Age - related cataract is commonly nuclear, cortical or subcapsular in location Steroid induced cataract is commonly posterior subcapsular .

15. Types of cataract Nuclear: is the most common type of cataract involves the central or 'nuclear' part of the lens. Over time, the nucleus becomes hard or 'sclerotic' due to condensation of lens nucleus and deposition of brown pigment within the lens. Proportion of the crystsllins ,the major lens protein ,undergo crosslinking and the formation of molecular aggregates of sufficient size to scatter light.

16. Types of cataract Cortical : Due to breakdown of groups of fibers in the lens cortex. They occur when changes in the water content of the periphery of the lens causes fissuring. Present with problems like glare and light scattering at night

17. Types of cataract Posterior subcapsular: At back of the lens adjacent to the capsule Because light becomes more focused toward the back of the lens, they can cause disproportionate symptoms for their size

18. Treatment Although much effort has been directed towards slowing the progression of, or preventing cataract, management remains surgical. There is no need to wait for the cataract to ‘ ripen ’ and cause major visual loss. The test is whether or not the cataract produces sufficient visual symptoms to reduce the quality of life . Patients may have difficulty in recognizing faces, reading, carrying out their occupation or achieving the driving standard. Prior to surgery patients must be informed of any coexisting eye disease which may influence the outcome of cataract surgery and the visual prognosis.

19. Cataract Surgery

20. Cataract Surgery Patient managed as a day case. Using Topical, LA / GA. The operation involves removal of most of the lens fibers and epithelial cells & insertion of a plastic lens implant of appropriate optical power.

21. Types of cataract surgeries Phacoemulsification Extra Capsular Cataract Extraction (ECCE ) Intra Capsular Cataract Extraction ( ICCE )

22. Phacoemulsification Anaesthetic   - The eye is numbed with either a subtenon injection around the eye or using simple eye drops. Corneal Incision  - Two cuts are made through the clear cornea to allow insertion of instruments into the eye. Capsulorhexis  - A needle or small pair of forceps is used to create a circular hole in the capsule (or bag) in which the lens sits. Phacoemulsification  - A handheld probe is used to break up and emulsify the lens into liquid using the energy of ultrasound waves. The resulting 'emulsion' is sucked away. Irrigation and Aspiration  - The cortex which is the soft outer layer of the cataract is aspirated or sucked away. Fluid removed is continually replaced with a salt solution to prevent collapse of the structure of the anterior chamber (the front part of the eye). Lens insertion  - A plastic foldable lens is inserted to the capsular bag that is used to contain the natural lens. Some surgeons will also inject an antibiotic in to the eye to reduce the risk of infection. The final step is to inject salt water in to the corneal wounds to cause the area to swell and seal the incision.

23. Extra Capsular Cataract Extraction Consists of removing the lens manually, but leaving the majority of the capsule intact. The lens is expressed through a 10–12 mm incision which is closed with sutures at the end of surgery. Extracapsular extraction is less frequently performed than phacoemulsification but can be useful when dealing with very hard cataracts or other situations where emulsification is problematic. Manual small incision cataract surgery (MSICS) has evolved from extracapsular cataract extraction. In MSICS, the lens is removed through a self-sealing scleral tunnel wound in the sclera which, ideally, is watertight and does not require suturing.

24. Intracapsular cataract extraction The lens and surrounding capsule are removed in one piece through a large incision while pressure is applied to the vitreous membrane. It is rarely performed as the surgery has a high rate of complications

25. Post-op care Patient is given a short course of steroids and antibiotics drops. Note: after cataract surgery the eye become ( hypermetropic ) corrected by : 1. Insertion of intraocular lens (IOL)= Best 2. Contact lens 3. Aphakic spectacles Visual rehabilitation and the prescription of new glasses is much quicker after phacoemulsification. Surgery may sometimes induce a degree of corneal astigmatism( imperfection of curvature) . Where sutures were used their postoperative removal may reduce this. This is done prior to measuring the patient for new glasses but after the wound has healed and steroid drops have been stopped

26. Advantages of phaco over ECCE: small incision. rapid recovery. less astigmatism. less complication. Even though we prefer ECCE over phaco in very dense cataract .

27. Complications of cataract surgery Vitreous loss If the posterior capsule is damaged during the operation the vitreous gel may come forward into the anterior chamber. increase risk for glaucoma or may cause retinal traction. The gel requires careful aspiration and excision ( vitrectomy ) at the time of surgery and placement of the intraocular lens may need to be deferred to a secondary procedure.

28. Complications of cataract surgery Iris prolapse. The iris may protrude through the surgical incision in the immediate postoperative period. It appears as a dark area at the incision site. The pupil is distorted. This requires prompt surgical repair.

29. Complications of cataract surgery Endophthalmitis . A serious but rare infective complication of cataract extraction (less than 0.3%). Patients present, usually within a few days of surgery, with: a. A painful red eye b. reduced visual acuity c. a collection of white cells in the anterior chamber ( hypopyon ). This is an extreme ophthalmic emergency . The patient requires urgent sampling of the aqueous and vitreous for microbiological analysis and an intravitreal broad - spectrum, antibiotic injection at the time of sampling (e.g. vancomycin and ceftazidime) to provide immediate cover.

30. Complications of cataract surgery Common causative organisms Staph. epidermidis Staph. aureus Pseudomonas sp.

31. Complications of cataract surgery Clinical case : A 60 - year - old lady has just had a cataract operation. Three days later she presents to her general practitioner with a painful red eye. The vision, which was initially much improved, has become blurred and she is seeing lots of floaters? The patient has endophthalmitis, a serious eye emergency, and must be referred immediately, requires urgent sampling of the aqueous and vitreous for microbiological analysis and an intravitreal broad - spectrum, antibiotic injection at the time of sampling (e.g. vancomycin and ceftazidime) to provide immediate cover.

32. Complications of cataract surgery Cystoid macular edema. The macula may become edematous following surgery, particularly if surgery was accompanied by vitreous loss or followed by inflammation. It may settle with time but can produce a severe reduction in acuity. Inflammatory prostaglandin release may play a part in this and prompt treatment with topical NSAIDs and steroid. Sometimes it may require treatment with steroids injected into or around the eye.

33. Complications of cataract surgery Retinal detachment.

34. Complications of cataract surgery Opacification of the posterior capsule . In approximately 20% of patients clarity of the posterior capsule decreases in the months following surgery, when residual epithelial cells migrate across its surface to form an opaque scar . Vision becomes blurred and there may be problems with glare. ** A small opening can be made in the capsule with a laser ( neodymium yttrium garnet) ( YAG )laser as an outpatient procedure. There is a small risk of {cystoid macular edema or retinal detachment} following YAG capsulotomy.

35. Congenital cataract

36. Congenital cataract The presence of congenital or infantile cataract is a threat to sight, not only because of the immediate obstruction to vision but because disturbance of the retinal image impairs visual maturation in the infant and leads to amblyopia and squint. If bilateral cataract is present and has a significant effect on retinal image formation this will cause: 1. Amblyopia 2. squint 3 . oscillation of the eyes ( nystagmus ).

37. Congenital cataract Both cataractous lenses require urgent surgery and the fitting of contact lenses to correct the aphakia. The treatment of uniocular congenital cataract remains controversial . Unfortunately the results of surgery are disappointing and vision may improve little because amblyopia develops despite adequate optical correction with a contact lens. To maximize the chances of success, treatment must be performed within the first few weeks of life and be accompanied by a coordinated routine fellow up to eye to stimulate visual maturation in the amblyopic eye and minimize the risk of squint.

38. Congenital cataract Increasingly, intraocular lenses are being implanted in children over 2 years old. The eye becomes increasingly myopic as the child grows, however, making the choice of lens implant power difficult. There is a significant risk of subsequent glaucoma developing in patients undergoing surgery for congenital cataract, particularly when this is performed prior to 1 year of age.