This ppt is about for how you can perform refraction after vitreo retinal cases... In OPD .

1. REFRACTION IN VITREO
RETINAL CASES
ABHISHEKH ROY
M.optm

2. PRESENTATION LAYOUT
> WHAT IS VITREOUS HUMOUR ?
> KNOW ABOUT SILICONE OIL
> REFRACTIVE CHANGES IN SILICON FILLED EYES IN
PATIENT WITH PHAKIC , APHAKIC , PSEUDOPHALIC.
> REFRACTIVE STATE OF THE EYE
> INDICATION FOR SILICONE OIL
> COMPLICATIONS OF SILICONE OIL
> REFRACTIVE CHANGES AFTER ENCIRCLING
BAND OR SEGMENTAL BUCKLES
> REFRACTIVE CHANGES AFTER SCLERAL BUCKLE

3. VITREOS HUMOUR
 DERIVED FROM A LATIN WORD “ VITRUM “ which means glass.
 Inert , transparent , colourless , jelly like hydrophilic gel present in
the posterior cavity .
 Bounded anteriorly by the lens and ciliary body and posteriorly by
the retina.
 Largest and simplest connective tissue present as a single piece in
the human body.
 Spherical in shape , volume 4ml and weight 4gm.

4. SILICIONE OIL REFRACTIVE STATE OF EYE
 Silicon oil has High R.I ( 1.405 ) as compared to vitreous
(1.336 ) .
 Refractive shifts depends on lens status .
 PHAKIC eye – oil forms a concave surface behind lens
ACTS as a MINUS LENS making eye hyperopic – 8D
hyperopia .

5. CONTD.
 APHAKIC EYE – convex surface as it bulges through pupillary aperture –
plus lens Myopic .
 Varies with pupillary aperture diameter size.
 Based on schematic eye calculation , a refractive shift from +12.5 to 5.6D
has been observed in aphakic eye filled with silicone oil .
 stefansson and colleagues observed an avg. shift of 7.4 D .
 Aphakic eye become less hyperopic by an average of 6 to 7 D .
 Where as phakic eye become more hyperopia by an average of 5.5 to 7.6
D .

6. REFRACTIVE STATE IN APHAKIC EYE
 IN THE APHAKIA state ,- silicone oil form a convex anterior
surface to the corneal endothelium. This surface decreases
the overall hyperopia by acting as a plus lens .
 In normal aphakic patient we can take vision with +10D

8. REFRACTIVE STATE IN PHAKIC EYE
 IN THE PHAKIC EYE , - the silicone oil forms a concave
surface behind the natural lens, which acts as a minus lens
and increases the overall level of hyperopia.
 In phakic eyes we can take vision with + 5.00 D because the
lens become concave in shape after inserting silicone oil.

10. REFRACTIVE CHANGES IN
PSEUDOPHAKIC EYE
 IN PSEUDOPHAKIC EYES , SILICONE OIL NULLIFY THE EFFECT
OF INTRAOCULAR LENS ( IF THE REFRACTIVE INDEX IS
SIMILAR TO THAT OF SILICONE OIL ), causing a myopic shift
like that of an aphakic eye.

11. COMPLICATIONS OF SILICONE OIL
 Cataract.
 Glaucoma.
 Keratopathy.
 Migration of silicone oil into optic nerve and rarely into the brain.
 Emulsification.
 Retinopathy.
 Recurrent retinal detachments.

12. REFRACTIVE CHANGES AFTER
ENCIRCLING ELEMENTS or BANDS
 Encircling procedures the greatest change in refractive error.
Generally the change is a spherical refractive change.
 the change is greater for phakic eyes than aphakic eyes,
because of the anterior shift of lens shifting in an increased
shift.
 The various factor which modify the refractive changes in
these cases the size of the encircling element and the height
that it induces the retina.

13. CONTD.
 The height of the encircling element is dependent of the distance
between the anterior and posterior suture placement for the
encirclage and also the tightness of the suture.
 if the dist. between the ante and post suture placed in an
encirclage is less, it will induce a higher intend on the retina and
hence shorten the eyes.
 similarly, if a tighter suture is applied, then also the intend will be
higher and hence the anteroposterior diameter of the eyes gets
shorter and inducing hyperopia.

14. CONTD.
 If we use wider encircling band , the effect is mostly
compression in the centre , which increases the axial length
and cause myopia.
 Rubin found that low to moderate buckle height ( band
width of 2mm) resulted in -1.56d to -2.24 d of change in
phakic eyes and -0.74 to- 1.14 change in aphakic eyes.
 low to moderate buckles induce an increase in axial length
while higher buckles shorten the axial length.

15. REFRACTIVE CHANGES AFTER SCLERAL
BUCKLING
 Most studies have found after scleral buckling induced
myopia will be occur.
 the amount of increased axial length depends upon the
height of encircling scleral buckle.
 The amount of induced myopia has been reported to be
greater in phakic eyes than in aphakic eyes.
 BURTON indicated that astigmatism may result from
alternation of corneal curvature.

16. CONTD.
 The refractive error may gradually decrease over 6 month follow up , with
residual error of -0.50 to -1.00D remaining stable.
 GRUPPOSO in his study found that largest spherical change was -5.50 D
and the largest cylindrical change was -4.00 D.
 High astig. Has been reported after scleral buckling.
 After scleral buckle pt become myopic and there is alternation in corneal
shape so astigmatism may occur more.
 A change in refractive error stabilizes usually within 2 to 3 months after
after scleral buckle. This error can be corrected using spectacles , contact
lens or refractive surgeries.